The 100 most-cited articles in Medicine & Science in Sports & Exercise, 2016

BACKGROUND: The relationship among physical activity (PA), fitness, cognitive function, and academic achievement in children is receiving considerable attention. The utility of PA to improve cognition and academic achievement is promising but uncertain; thus, this position stand will provide clarity from the available science. OBJECTIVE: The purpose of this study was to answer the following questions: 1) among children age 5-13 yr, do PA and physical fitness influence cognition, learning, brain structure, and brain function? 2) Among children age 5-13 yr, do PA, physical education (PE), and sports programs influence standardized achievement test performance and concentration/attention? STUDY ELIGIBILITY CRITERIA: This study used primary source articles published in English in peer-reviewed journals. Articles that presented data on, PA, fitness, or PE/sport participation and cognition, learning, brain function/structure, academic achievement, or concentration/attention were included. DATA SOURCES: Two separate searches were performed to identify studies that focused on 1) cognition,…

It is the position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine that the performance of, and recovery from, sporting activities are enhanced by well-chosen nutrition strategies. These organizations provide guidelines for the appropriate type, amount, and timing of intake of food, fluids, and supplements to promote optimal health and performance across different scenarios of training and competitive sport. This position paper was prepared for members of the Academy of Nutrition and Dietetics, Dietitians of Canada (DC), and American College of Sports Medicine (ACSM), other professional associations, government agencies, industry, and the public. It outlines the Academy's, DC's and ACSM's stance on nutrition factors that have been determined to influence athletic performance and emerging trends in the field of sports nutrition. Athletes should be referred to a registered dietitian/nutritionist for a personalized nutrition plan. In the United States and in Canada, the Certified Specialist in Sports Dietetics (CSSD) is a…

Despite flourishing interest in the topic of fatigue-as indicated by the many presentations on fatigue at the 2015 Annual Meeting of the American College of Sports Medicine-surprisingly little is known about its effect on human performance. There are two main reasons for this dilemma: 1) the inability of current terminology to accommodate the scope of the conditions ascribed to fatigue, and 2) a paucity of validated experimental models. In contrast to current practice, a case is made for a unified definition of fatigue to facilitate its management in health and disease. On the basis of the classic two-domain concept of Mosso, fatigue is defined as a disabling symptom in which physical and cognitive function is limited by interactions between performance fatigability and perceived fatigability. As a symptom, fatigue can only be measured by self-report, quantified as either a trait characteristic or a state variable. One consequence of such a definition is that the word fatigue should not be preceded by an adjective (e.g., central, mental, muscle, peripheral, and supraspinal) to…

: During exercise, there is a progressive reduction in the ability to produce muscle force. Processes within the nervous system as well as within the muscles contribute to this fatigue. In addition to impaired function of the motor system, sensations associated with fatigue and impairment of homeostasis can contribute to the impairment of performance during exercise. This review discusses some of the neural changes that accompany exercise and the development of fatigue. The role of brain monoaminergic neurotransmitter systems in whole-body endurance performance is discussed, particularly with regard to exercise in hot environments. Next, fatigue-related alterations in the neuromuscular pathway are discussed in terms of changes in motor unit firing, motoneuron excitability, and motor cortical excitability. These changes have mostly been investigated during single-limb isometric contractions. Finally, the small-diameter muscle afferents that increase firing with exercise and fatigue are discussed. These afferents have roles in cardiovascular and respiratory responses to exercise, and…

: The hyperbolic form of the power-duration relationship is rigorous and highly conserved across species, forms of exercise, and individual muscles/muscle groups. For modalities such as cycling, the relationship resolves to two parameters, the asymptote for power (critical power [CP]) and the so-called W' (work doable above CP), which together predict the tolerable duration of exercise above CP. Crucially, the CP concept integrates sentinel physiological profiles-respiratory, metabolic, and contractile-within a coherent framework that has great scientific and practical utility. Rather than calibrating equivalent exercise intensities relative to metabolically distant parameters such as the lactate threshold or V˙O2max, setting the exercise intensity relative to CP unifies the profile of systemic and intramuscular responses and, if greater than CP, predicts the tolerable duration of exercise until W' is expended, V˙O2max is attained, and intolerance is manifested. CP may be regarded as a "fatigue threshold" in the sense that it separates exercise intensity domains within which the…

Performance fatigability differs between men and women for a range of fatiguing tasks. Women are usually less fatigable than men, and this is most widely described for isometric fatiguing contractions and some dynamic tasks. The sex difference in fatigability is specific to the task demands so that one mechanism is not universal, including any sex differences in skeletal muscle physiology, muscle perfusion, and voluntary activation. However, there are substantial knowledge gaps about the task dependency of the sex differences in fatigability, the involved mechanisms, and the relevance to clinical populations and with advanced age. The knowledge gaps are in part due to the significant deficits in the number of women included in performance fatigability studies despite a gradual increase in the inclusion of women for the last 20 yr. Therefore, this review 1) provides a rationale for the limited knowledge about sex differences in performance fatigability, 2) summarizes the current knowledge on sex differences in fatigability and the potential mechanisms across a range of tasks, 3)…

PURPOSE: This study aimed to evaluate the initial and long-term effectiveness of a workplace intervention compared with usual practice, targeting the reduction of sitting on activity outcomes. METHODS: Office worksites (≥1 km apart) from a single organization in Victoria, Australia, were cluster randomized to intervention (n = 7) or control (n = 7). Participants were 231 desk-based office workers (5-39 participants per worksite) working at least 0.6 full-time equivalent. The workplace-delivered intervention addressed organizational, physical environment, and individual behavioral changes to reduce sitting time. Assessments occurred at baseline, 3 months, and 12 months, with the primary outcome participants' objectively measured (activPAL3 device) workplace sitting time (minutes per 8-h workday). Secondary activity outcomes were workplace time spent standing, stepping (light, moderate to vigorous, and total), and in prolonged (≥30 min) sitting bouts (hours per 8-h workday); usual duration of workplace sitting bouts; and overall sitting, standing, and stepping time (minutes per 16-h…

PURPOSE: Emerging literature suggests that physical activity and fitness may have a positive effect on cognitive and mental health in adolescents. The purpose of the current study was to evaluate the efficacy of two high-intensity interval training (HIIT) protocols for improving cognitive and mental health outcomes (executive function, psychological well-being, psychological distress, and physical self-concept) in adolescents. METHODS: Participants (n = 65; mean age = 15.8 ± 0.6 yr) were randomized to three conditions: aerobic exercise program (AEP; n = 21), resistance and aerobic program (RAP; n = 22), and control (n = 22). HIIT sessions (8-10 min per session) were delivered during physical education lessons or at lunchtime three times per week for 8 wk. Assessments were conducted at baseline and immediately postintervention to detect changes in executive function (trail making test), psychological well-being, psychological distress, and physical self-description by researchers blinded to treatment allocation. Intervention effects were examined using linear mixed models. Cohen's d…

PURPOSE: Our goal was to quantify if small (1%-3%) changes in running economy quantitatively affect distance-running performance. Based on the linear relationship between metabolic rate and running velocity and on earlier observations that added shoe mass increases metabolic rate by ~1% per 100 g per shoe, we hypothesized that adding 100 and 300 g per shoe would slow 3000-m time-trial performance by 1% and 3%, respectively. METHODS: Eighteen male sub-20-min 5-km runners completed treadmill testing, and three 3000-m time trials wearing control shoes and identical shoes with 100 and 300 g of discreetly added mass. We measured rates of oxygen consumption and carbon dioxide production and calculated metabolic rates for the treadmill tests, and we recorded overall running time for the time trials. RESULTS: Adding mass to the shoes significantly increased metabolic rate at 3.5 m·s by 1.11% per 100 g per shoe (95% confidence interval = 0.88%-1.35%). While wearing the control shoes, participants ran the 3000-m time trial in 626.1 ± 55.6 s. Times averaged 0.65% ± 1.36% and 2.37% ± 2.09%…

The activPAL (AP) monitor is well established for distinguishing sitting, standing, and stepping time. However, its validity in predicting time in physical activity intensity categories in a free-living environment has not been determined. PURPOSE: This study aimed to determine the validity of the AP in estimating time spent in sedentary, light, and moderate-to-vigorous physical activity (MVPA) in a free-living environment. METHODS: Thirteen participants (mean ± SD age = 24.8 ± 5.2 yr, BMI = 23.8 ± 1.9 kg·m) were directly observed for three 10-h periods wearing an AP. A custom R program was developed and used to summarize detailed active and sedentary behavior variables from the AP. AP estimates were compared with direct observation. RESULTS: The AP accurately and precisely estimated time in activity intensity categories (bias [95% confidence interval]; sedentary = 0.8 min [-2.9 to 4.5], light = 1.7 min [2.2-5.7], and -2.6 min [-5.8 to 0.7]). The overall accuracy rate for time in intensity categories was 96.2%. The AP also accurately estimated guideline minutes, guideline bouts,…

Numerous health problems, including acute critical illness, cancer, diseases associated with chronic inflammation, and neurological disorders, often result in skeletal muscle weakness and fatigue. Disease-related muscle atrophy and fatigue is an important clinical problem because acquired skeletal muscle weakness can increase the duration of hospitalization, result in exercise limitation, and contribute to a poor quality of life. Importantly, skeletal muscle atrophy is also associated with increased morbidity and mortality of patients. Therefore, improving our understanding of the mechanism(s) responsible for skeletal muscle weakness and fatigue in patients is a required first step to develop clinical protocols to prevent these skeletal muscle problems. This review will highlight the consequences and potential mechanisms responsible for skeletal muscle atrophy and fatigue in patients experiencing acute critical illness, cancer, chronic inflammatory diseases, and neurological disorders.

PURPOSE: To examine the test-retest reliability and validity of ten activity trackers for step counting at three different walking speeds. METHODS: Thirty-one healthy participants walked twice on a treadmill for 30 min while wearing 10 activity trackers (Polar Loop, Garmin Vivosmart, Fitbit Charge HR, Apple Watch Sport, Pebble Smartwatch, Samsung Gear S, Misfit Flash, Jawbone Up Move, Flyfit, and Moves). Participants walked three walking speeds for 10 min each; slow (3.2 km·h), average (4.8 km·h), and vigorous (6.4 km·h). To measure test-retest reliability, intraclass correlations (ICC) were determined between the first and second treadmill test. Validity was determined by comparing the trackers with the gold standard (hand counting), using mean differences, mean absolute percentage errors, and ICC. Statistical differences were calculated by paired-sample t tests, Wilcoxon signed-rank tests, and by constructing Bland-Altman plots. RESULTS: Test-retest reliability varied with ICC ranging from -0.02 to 0.97. Validity varied between trackers and different walking speeds with mean…

This systematic review (1) examined the evidence linking physical activity (PA) to cognition and academic performance in elementary school children. Specifically, in reviewing the literature, we sought to answer the following two questions: 1) Among children age 5–13 yr, do PA and physical fitness influence brain structure, brain function, cognition, and learning? 2) Among children age 5–13 yr, do PA, physical education, and sports programs influence standardized achievement test performance and concentration/attention? METHODS The review was performed and reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines (ref. 105 in [1]). The search was applied to PubMed and adapted for Embase, Education Resources Information Center, PsychInfo, SportDiscus, Scopus, Web of Science, and Academic Search Premier (1990 to September 2014). A reference librarian was consulted on the search process. Study quality was assessed using a checklist developed by Downs and Black (ref. 59 in [1]) that was designed to assess the quality of both…

PURPOSE: Consumer-based physical activity (PA) monitors are popular for individual tracking of PA variables. However, current research has not examined how these monitors track energy expenditure (EE) and steps in distinct activities. This study examined the accuracy of the Fitbits One, Zip, and Flex and Jawbone UP24 for estimating EE and steps for specific activities and activity categories. METHODS: Thirty subjects completed a structured protocol consisting of three sedentary, four household, and four ambulatory/exercise activities. All subjects began by lying on a bed for 10 min; 10 other activities were performed for 5 min each. Indirect calorimetry (COSMED) and researcher-counted steps were criterion measures for EE and step counts, respectively. The Omron HJ-720IT pedometer was used as a comparison of step count accuracy. EE and steps were compared with criterion measures using the Friedman repeated-measures nonparametric test and mean absolute percent error (MAPE). RESULTS: All PA monitors predicted EE within 8% of COSMED for sedentary activity but overestimated EE by 16%-40%…

PURPOSE: We examined total activity, light activity, and moderate-to-vigorous physical activity (MVPA) as predictors of mortality in a nationally representative sample of older adults. Then we explored the theoretical consequences of replacing sedentary time with the same duration of light activity or MVPA. METHODS: Using accelerometer-measured activity, the associations between total activity, light activity (100-2019 counts per minute), and MVPA (>2019 counts per minute) counts and mortality were examined in adults age 50 to 79 yr in the National Health and Nutrition Examination Survey, 2003-2006 (n = 3029), with mortality follow-up through December 2011. Cox proportional hazard models were fitted to estimate mortality risks. An isotemporal substitution model was used to examine the theoretical consequences of replacing sedentary time with light activity or MVPA on mortality. RESULTS: After adjusting for potential confounders, including age, sex, race/ethnicity, education, BMI, and the presence of comorbid conditions, those in the highest tertile of total activity counts had one…

PURPOSE: Understanding factors that influence accurate assessment of physical activity (PA) and sedentary behavior (SB) is important to measurement development, epidemiologic studies, and interventions. This study examined agreement between self-reported (International Physical Activity Questionnaire-Long Form [IPAQ-LF]) and accelerometry-based estimates of PA and SB across six countries and identified correlates of between-method agreement. METHODS: Self-report and objective (accelerometry-based) PA and SB data were collected in 2002-2011 from 3865 adult participants in eight cities from six countries (Belgium, Czech Republic, Denmark, Spain, United Kingdom, and United States). Between-method relative agreement (correlation) and absolute disagreement (mean difference between conceptually and intensity-matched IPAQ-LF and accelerometry-based PA and SB variables) were estimated. Also, sociodemographic characteristics and PA patterns were examined as correlates of between-method agreement. RESULTS: Observed relative agreement (relationships of IPAQ-LF with accelerometry-based PA and…

PURPOSE: This study aimed to evaluate the hypothesis that exercise attenuates the reductions in lean mass, muscle strength, bone mineral density, and V˙O2max that accompany modest weight loss induced by calorie restriction (CR). METHODS: Overweight, sedentary women and men (n = 52, 45-65 yr) were randomized to 6%-8% weight loss by using CR, endurance exercise training (EX), or both (CREX). The CR and the CREX groups underwent counseling to reduce energy intake by 20% and 10%, respectively. The EX and the CREX groups exercised 7.4 ± 0.5 and 4.4 ± 0.5 h·wk, respectively. Before and after 16.8 ± 1.1 wk of weight loss, lean mass and bone mineral density were measured with dual-energy x-ray absorptiometry, strength was measured with dynamometry, and aerobic capacity (V˙O2max) was measured with indirect calorimetry during maximal-intensity treadmill exercise. RESULTS: Weight loss was ~7% in all groups. Decreases in whole-body (~2%, P = 0.003) and lower extremity (~4%, P < 0.0001) lean mass occurred in the CR group (both P < 0.05). Despite similar weight loss, these reductions were…

PURPOSE: The aim of this investigation was to examine the influence of different types of exercise exertion on primary school children's working memory (WM). METHODS: Participants (N = 71, 9.4 yr, 39 girls) were randomly assigned to a cardiovascular exercise (CE), a motor exercise (ME), or a control group (CON). They underwent a letter digit span task (WM) before and after an intervention period that involved 10 wk of an additional afterschool exercise regimen, which took place three times a week for 45 min. Students in the control group participated in assisted homework sessions. RESULTS: WM performance of the 9- to 10-yr-old children benefited from both the cardiovascular and the motor exercise programs, but not from the control condition. The increase in WM performance was significantly larger for children in the ME compared with the CE or CON. CONCLUSION: These findings add to the knowledge base relating different types of exercise and WM. Besides the efficiency of cardiovascular exercise training, a special motor-demanding intervention seems to be a beneficial strategy to…

PURPOSE: Sedentary behavior is an emerging independent health risk factor. The accuracy of measuring sedentary time using accelerometers may depend on the wear location. This study in older adults evaluated the accuracy of various hip- and wrist-worn ActiGraph accelerometer cutoff points to define sedentary time using the activPAL as the reference method. METHODS: Data from 62 adults (mean age, 78.4 yr) of the Aging Research Evaluating Accelerometry study were used. Participants simultaneously wore an activPAL accelerometer on the thigh and ActiGraph accelerometers on the hip, dominant, and nondominant wrist for 7 d in a free-living environment. Using the activPAL as the reference criteria, we compared classification of sedentary time to hip-worn and wrist-worn ActiGraph accelerometers over a range of cutoff points for both 60-s and 15-s epochs. RESULTS: The optimal cutoff point for the hip vertical axis was <22 counts per minute with an area under the curve (AUC) of 0.85; the optimal hip vector magnitude cutoff point was <174 counts per minute with an AUC of 0.89. For the dominant…

PURPOSE: The underlying cause of balance impairments in chronic ankle instability (CAI) patients remains unknown, but an altered use of sensory information has been hypothesized as a potential cause. The purpose of this systematic review with meta-analysis was to determine whether CAI patients use somatosensory information to the same extent as uninjured controls during static single limb stance. METHODS: We searched PubMed, CINAHL, SPORTDiscus, and Scopus databases from origin to March 2016 using the combination of key words, including postural control, postural stability, single limb stance, single leg stance, single leg balance, single limb balance, and time to boundary (TTB). Eligible studies had to include instrumented single leg stance with both eyes open and eyes closed in healthy, CAI, or both groups as well as report TTB mean and SD values. RESULTS: A total of 11 articles were identified. Effect sizes using eyes closed to eyes open standardized mean differences and 95% confidence intervals were calculated for all studies that were included in this investigation. Similarly,…

Increases in maximal oxygen uptake (V˙O2max) frequently occur with high-intensity interval training (HIIT), yet the specific adaptation explaining this result remains elusive. PURPOSE: This study examined changes in V˙O2max and cardiac output (CO) in response to periodized HIIT. METHODS: Thirty-nine active men and women (mean age and V˙O2max = 22.9 ± 5.4 yr and 39.6 ± 5.6 mL·kg·min) performed HIIT and 32 men and women (age and V˙O2max = 25.7 ± 4.5 yr and 40.7 ± 5.2 mL·kg·min) were nonexercising controls (CON). The first 10 sessions of HIIT required eight to ten 60 s bouts of cycling at 90%-110% percent peak power output interspersed with 75 s recovery, followed by randomization to one of three regimes (sprint interval training (SIT), high-volume interval training (HIITHI), or periodized interval training (PER) for the subsequent 10 sessions. Before, midway, and at the end of training, progressive cycling to exhaustion was completed during which V˙O2max and maximal CO were estimated. RESULTS: Compared with CON, significant (P < 0.001) increases in V˙O2max in HIIT + SIT (39.8 ± 7.3…

PURPOSE: This study aimed to investigate potential bidirectional relationships between sport participation and mental health during early adolescence. METHODS: Data were taken from wave 5 (2012) and wave 6 (2014) of the K cohort of the Longitudinal Study of Australian Children. In total, there were 4023 participants (mean age = 12.41 yr, SD = 0.49 yr, at baseline), and this sample was followed up 24 months later. Cross-lagged panel models were used to examine bidirectional relationships between sport participation (hours per week for team, individual, and total sport participation) and mental health (total psychological difficulties, internalizing problems, and externalizing problems) as measured by the parent-report version of the Strengths and Difficulties Questionnaire (SDQ). RESULTS: Bidirectional relationships were evident between time involved in sport and overall mental health (Sport12→SDQ14: β = -0.048; SDQ12→Sport14: β = -0.062). Bidirectional relationships were also evident between time involved in sport participation and internalizing (social and emotional) problems…

INTRODUCTION/PURPOSE: Quadriceps strength is a useful clinical predictor of self-reported function after anterior cruciate ligament reconstruction (ACLR). However, it remains unknown if quadriceps strength normalized to body mass (QBM) or quadriceps strength limb symmetry index (QLSI) is the best predictor of self-reported function in individuals with ACLR. We sought to determine whether QBM and QLSI are able to predict individuals with ACLR who self-report high function (≥90% on the international knee documentation committee (IKDC) index). METHODS: Ninety-six individuals with a history of a primary unilateral ACLR were recruited for a multisite cross-sectional descriptive laboratory experiment. Bilateral isometric quadriceps strength was collected at 90° of knee flexion to calculate QBM and QLSI (ratio of the ACLR limb to the contralateral limb). Area under the curve (AUC) values were calculated using receiver operating characteristic curve analyses to determine the capacity of QBM and QLSI to predict individuals with high self-reported function on the IKDC index. RESULTS: QBM…

PURPOSE: Asymmetrical loading patterns are commonplace in football sports. Our aim was to examine the influence of training age and limb function on lower-body musculoskeletal morphology. METHODS: Fifty-five elite football athletes were stratified into less experienced (≤3 yr; n = 27) and more experienced (>3 yr; n = 28) groups by training age. All athletes underwent whole-body dual-energy x-ray absorptiometry scans and lower-body peripheral quantitative computed tomography tibial scans on the kicking and support limbs. RESULTS: Significant interactions between training age and limb function were evident across all skeletal parameters (F16, 91 = 0.182, P = 0.031, Wilks Λ = 0.969). Asymmetries between limbs were significantly larger in the more experienced players than the less experienced players for tibial mass (P ≤ 0.044, d ≥ 0.50), total cross-sectional area (P ≤ 0.039, d ≥ 0.53), and stress-strain indices (P ≤ 0.050, d ≥ 0.42). No significant asymmetry was evident for total volumetric density. More experienced players also exhibited greater lower-body tibial mass (P ≤ 0.001, d ≥…

PURPOSE: We tested the hypothesis that central and peripheral fatigue after constant-load cycling exercise would vary with exercise intensity and duration. METHODS: Twelve well-trained male cyclists (V˙O2max, 4.49 ± 0.35 L·min) completed three constant-load cycling trials to the limit of tolerance in a randomized crossover design. Exercise intensities were set according to the respiratory responses to a preliminary ramp test to elicit cardiorespiratory and metabolic responses consistent with exercise in the severe and heavy exercise domains: 1) at power at V˙O2max (S+, 379 ± 31 W), 2) at 60% of the difference between gas exchange threshold and V˙O2max (S-, 305 ± 23 W), and 3) at the respiratory compensation point (RCP, 254 ± 26 W). Pre- and postexercise twitch responses from the quadriceps to the electrical stimulation of the femoral nerve and magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function, respectively. RESULTS: Exercise time was 3.14 ± 0.59, 11.11 ± 1.86, and 42.14 ± 9.09 min for S+, S-, and RCP, respectively. All trials…

PURPOSE: Emerging evidence suggests physical activity (PA) is associated with cognitive function. To overcome limitations of self-report PA measures, this study investigated the association of accelerometer-measured PA with incident cognitive impairment and longitudinal cognition among older adults. METHODS: Participants were recruited from the cohort study Reasons for Geographic and Racial Differences in Stroke in the United States. Accelerometers provided PA measures, including the percentage of total accelerometer wearing time spent in moderate-to-vigorous-intensity PA (MVPA%), light-intensity PA, and sedentary time for four to seven consecutive days at baseline. Cognitive impairment was defined by the Six-Item Screener. Letter fluency, animal fluency, word list learning, and Montreal Cognitive Assessment (orientation and recall) were conducted to assess executive function and memory. RESULTS: Participants (N = 6452, 69.7 ± 8.5 yr, 55.3% women, 30.5% Black) with usable accelerometer and cognition measures spent extremely limited time in MVPA (1.5% ± 1.9% of accelerometer wearing…

PURPOSE: This study aimed to determine the agreement between outputs from contemporaneous measures of acceleration from wrist-worn GENEActiv and ActiGraph accelerometers when processed using the GGIR open source package. METHODS: Thirty-four participants wore a GENEActiv and an ActiGraph GT3X+ on their nondominant wrist continuously for 2 d to ensure the capture of one 24-h day and one nocturnal sleep. GENEActiv.bin files and ActiGraph .csv files were analyzed with R-package GGIR version 1.2-0. Key outcome variables were as follows: wear time, average magnitude of dynamic wrist acceleration (Euclidean norm minus one [ENMO]), percentile distribution of accelerations, time spent across acceleration levels in a 40-mg resolution, time in moderate-to-vigorous physical activity (MVPA: total, 10-min bouts), and duration of nocturnal sleep. RESULTS: There was a high agreement between accelerometer brands for all derived outcomes (wear time, MVPA, and sleep; intraclass correlation coefficient [ICC] > 0.96), ENMO (ICC = 0.99), time spent across acceleration levels (ICC > 0.93), and…

PURPOSE: We investigated the effect of a chronic dietary periodization strategy on endurance performance in trained athletes. METHODS: Twenty-one triathletes (V˙O2max: 58.7 ± 5.7 mL·min(-1)·kg(-1)) were divided into two groups: a "sleep-low" (SL) (n = 11) and a control (CON) group (n = 10) consumed the same daily carbohydrate (CHO) intake (6 g·kg(-1)·d(-1)) but with different timing over the day to manipulate CHO availability before and after training sessions. The SL strategy consisted of a 3-wk training-diet intervention comprising three blocks of diet-exercise manipulations: 1) "train-high" interval training sessions in the evening with high-CHO availability, 2) overnight CHO restriction ("sleeping-low"), and 3) "train-low" sessions with low endogenous and exogenous CHO availability. The CON group followed the same training program but with high CHO availability throughout training sessions (no CHO restriction overnight, training sessions with exogenous CHO provision). RESULTS: There was a significant improvement in delta efficiency during submaximal cycling for SL versus CON…

PURPOSE: The objective of this study is to compare the accuracy of the activPAL and ActiGraph GT3X+ (waist and thigh) proprietary postural allocation algorithms and an open-source postural allocation algorithm applied to GENEActiv (thigh) and ActiGraph GT3X+ (thigh) data. METHODS: Thirty-four adults (≥18 yr) wore the activPAL3, GENEActiv, and ActiGraph GT3X+ on the right thigh and an ActiGraph on the right hip while performing four lying, seven sitting, and five upright activities in the laboratory. Lying and sitting tasks incorporated a range of leg angles (e.g., lying with legs bent and sitting with legs crossed). Each activity was performed for 5 min while being directly observed. The percentage of the time the posture was correctly classified was calculated. RESULTS: Participants consisted of 14 males and 20 females (mean age, 27.2 ± 5.9 yr; mean body mass index, 23.8 ± 3.7 kg·m). All postural allocation algorithms applied to monitors worn on the thigh correctly classified ≥93% of the time lying, ≥91% of the time sitting, and ≥93% of the time upright. The ActiGraph waist…

PURPOSE: This study aimed to examine the association of strength training with incident type 2 diabetes and cardiovascular disease risk. METHODS: We followed 35,754 healthy women (mean age = 62.6 yr, range = 47.0-97.8) from the Women's Health Study, who responded to a health questionnaire that included physical activity questions in 2000, assessing health outcomes through annual health questionnaire through 2014 (mean ± SD follow-up = 10.7 ± 3.7 yr). Incident type 2 diabetes (N cases = 2120) and cardiovascular disease (N cases = 1742) were confirmed on medical record review. Cases of cardiovascular disease were defined as confirmed cases of myocardial infarction, stroke, coronary artery bypass graft, angioplasty, or cardiovascular disease death. RESULTS: Compared with women who reported no strength training, women engaging in any strength training experienced a reduced rate of type 2 diabetes of 30% (hazard ratio = 0.70, 95% confidence interval = 0.61-0.80) when controlling for time spent in other activities and other confounders. A risk reduction of 17% was observed for…

INTRODUCTION: Measures of HR variability (HRV) have shown potential to be of use in training prescription. PURPOSE: The aim of this study was to investigate the effectiveness of using HRV in endurance training prescription. METHODS: Forty recreational endurance runners were divided into the HRV-guided experimental training group (EXP) and traditional predefined training group (TRAD). After a 4-wk preparation training period, TRAD trained according to a predefined training program including two to three moderate- (MOD) and high-intensity training (HIT) sessions per week during an 8-wk intensive training period. The timing of MOD and HIT sessions in EXP was based on HRV, measured every morning. The MOD/HIT session was programmed if HRV was within an individually determined smallest worthwhile change. Otherwise, low-intensity training was performed. Maximal oxygen consumption (V˙O2max) and 3000-m running performance (RS3000m) were measured before and after both training periods. RESULTS: The number of MOD and HIT sessions was significantly lower (P = 0.021, effect size = 0.98) in EXP…

DESCRIPTION This is an update of a book that covers all aspects of strength and conditioning that professionals in the field of exercise require. The Website offers ancillary videos and laboratory activities. The third edition was published in 2008. PURPOSE It is intended to be a comprehensive resource on all aspects of the field of strength and conditioning. Copious amounts of recent and relevant research are detailed in a concise manner. The online videos help with understanding, supplementing the photographs in the book. AUDIENCE The intended audience includes anyone in the field of strength and conditioning, from students to seasoned professionals. The authors successfully serve this wide-ranging audience with a book that is readable and relevant for all. Seasoned professionals can use this as a reference or to update their knowledge to align with current research, whereas students can use it to understand new and often complicated information. The book is appropriate for professionals familiar with the verbiage, and it highlights key terms for students who may be struggling to…

INTRODUCTION: Although exercise is an effective intervention for many psychological health issues, it has often been overlooked as a potential adjunct to eating disorder (ED) treatment. Thus, our objective was to summarize the literature by synthesizing themes identified in clinical studies and explicit guidelines or recommendations for the use or management of exercise in ED interventions into a proposed set of guidelines for the use of exercise in ED treatment. METHODS: A literature search in exercise science, health psychology, and the ED literature was conducted. The focus was to obtain articles that reported on therapeutic effects and/or guidelines for the therapeutic use of exercise in individuals with ED. RESULTS: Our review identified 11 core themes describing techniques that have been successful in using exercise therapeutically in ED treatment. These 11 guidelines are as follows: employ a team of relevant experts, monitor medical status, screen for exercise-related psychopathology, create a written contract of how therapeutic exercise will be used, include a…

PURPOSE: Sprint interval training (SIT) is a time-efficient strategy to improve cardiorespiratory fitness (CRF); however, most protocols have been studied in laboratory settings and require specialized equipment. We investigated the efficacy of brief intense stair climbing as a practical model of SIT to improve CRF. METHODS: Two separate studies, each consisting of an acute and chronic phase, were conducted in a total of 31 sedentary women (age = 24 ± 10 yr, body mass index = 23 ± 4 kg·m). RESULTS: The acute phase of study 1 established that the mean HR, blood [lactate], and RPE were similar when participants (n = 8) performed an SIT protocol that involved 3 × 20-s "all-out" efforts of either continuously ascending stairs or cycling. The chronic phase demonstrated that CRF, as determined by peak oxygen uptake (V˙O2peak), increased by 12% or ~1 MET (8.27 ± 1.05 to 9.25 ± 1.01 METs, P = 0.002) when participants (n = 12) performed the 3 × 20-s stair climbing protocol 3 d·wk for 6 wk. The acute phase of study 2 established that HR and RPE were similar when participants (n = 11)…

DESCRIPTION The third edition of this book is divided into three sections to provide updates on the diagnosis and management of musculoskeletal disorders, pain, and chronic medical conditions. The second edition was published in 2008. PURPOSE The purpose is to concisely cover the diagnosis and management of these conditions while addressing new topics, including shoulder and hip labral tears, cancer-associated conditions, and updated ICD-10 codes. The book successfully meets the objectives, including the aim to enhance the practice of busy physicians seeing patients with these conditions. AUDIENCE The audience includes physiatrists, internists, family physicians, orthopedists, rheumatologists, and neurologists. It especially targets ambulatory practitioners. It also would be a helpful review for medical students who are interested in these topics. FEATURES This book is divided into three sections. The first covers 94 specific musculoskeletal diagnoses, organized by anatomic region. The second covers 23 pain conditions and their management, and the third section 45 typically chronic…

INTRODUCTION: Data evaluating mortality benefit from replacing sedentary time with physical activity are sparse. We explored reallocating time spent in sedentary behavior to physical activity of different intensities in relation to mortality risk. METHODS: Women and men age 50-85 yr from the National Health and Nutrition Examination Survey 2003-2004 and 2005-2006 cycles with follow-up through December 31, 2011, were included. Sedentary time and physical activity were assessed using an ActiGraph accelerometer. Isotemporal substitution models were used to estimate the effect of replacing one activity behavior with another activity behavior for the same amount of time while holding total accelerometer wear time constant. RESULTS: During a mean follow-up of 6.35 yr, 697 deaths from any cause occurred. Replacing 30 min of sedentary time with an equal amount of light activity was associated with 14% reduced risk of mortality (multivariable-adjusted hazard ratio (HR), 0.86; 95% confidence interval (CI), 0.83-0.90). Replacement of sedentary time with moderate to vigorous activity was…

UNLABELLED: Cardiometabolic impairments that begin early in life are particularly critical, because they often predict metabolic dysfunction in adulthood. Obesity, high-fat diet (HFD), and inactivity are all associated with adipose tissue (AT) inflammation and insulin resistance (IR), major predictors of metabolic dysfunction. Recent evidence has also associated the gut microbiome with cardiometabolic health. PURPOSE: The objective of this study is to compare equal energy deficits induced by exercise and caloric reduction on cardiometabolic disease risk parameters including AT inflammation, IR, and gut microbiota changes during HFD consumption. METHODS: Obesity-prone rats fed HFD were exercise trained (Ex, n = 10) or weight matched to Ex via caloric reduction although kept sedentary (WM, n = 10), and compared with ad libitum HFD-fed (Sed, n = 10) rats for IR, systemic energetics and spontaneous physical activity (SPA), adiposity, and fasting metabolic parameters. Visceral, subcutaneous, periaortic, and brown AT (BAT), liver, aorta, and cecal digesta were examined. RESULTS: Despite…

The etiology of muscle fatigue defined as a loss of force, velocity, and power in response to contractile activity has been studied and debated for over a hundred years, yet important questions remain either unresolved or controversial (2,7,10). As clearly shown in published reviews by Fitts (7) and later by Allen et al. (2) and Kent-Braun et al. (10), the causes of muscle fatigue are complex and involve multiple factors within the central nervous system and the active muscles. The factors central to the debate on the importance of low cell pH as a causative fatiguing agent are the definition of muscle fatigue, the extent of intracellular acidosis, and the changes in the cellular environment that occur in conjunction with the increase in H+. The most pertinent established facts are that: 1) high-intensity contractile activity can cause muscle pH to decline from 7.0 to as low as 6.3–6.2 in multiple species, including frogs, cats, rats, and humans (7); 2) acidosis induced by contractile activity can be correlated with muscle fatigue (7); and 3) the fatigue-inducing effects of low pH…

INTRODUCTION: The randomized controlled trial "Physical Activity in Pediatric Cancer" determined the effects of an inhospital exercise intervention combining aerobic and muscle strength training on pediatric cancer patients with solid tumors undergoing neoadjuvant chemotherapy. METHODS: Participants were allocated to an exercise (n = 24, 17 boys; mean ± SEM age, 10 ± 1 yr) or control group (n = 25, 18 boys; 11 ± 1 yr). Training included three sessions per week for 19 ± 2 wk. Participants were assessed at treatment initiation, termination, and 2 months after end treatment. The primary endpoint was muscle strength (as assessed by upper and lower-body five-repetition-maximum tests). Secondary endpoints included cardiorespiratory fitness, functional capacity during daily life activities, physical activity, body mass and body mass index, and quality of life. RESULTS: Most sessions were performed in the hospital's gymnasium. Adherence to the program averaged 68% ± 4% and no major adverse events or health issues were noted. A significant interaction (group-time) effect was found for all…

PURPOSE: The objective of this study is to compare the physiological capacity and training characteristics of the world's six highest ranked female cross-country skiers (world class (WC)) with those of six competitors of national class (NC). METHODS: Immediately before the start of the competition season, all skiers performed three 5-min submaximal stages of roller skiing on a treadmill for measurement of oxygen cost, as well as a 3-min self-paced performance test using both the double poling (DP) and diagonal stride (DIA) techniques. During the 3-min performance tests, the total distance covered, peak oxygen uptake (V˙O2peak), and accumulated oxygen deficit were determined. Each skier documented the intensity and mode of their training during the preceding 6 months in a diary. RESULTS: There were no differences between the groups with respect to oxygen cost or gross efficiency at the submaximal speeds. The WC skiers covered 6%-7% longer distances during the 3-min tests and exhibited average V˙O2peak values of ∼70 and ∼65 mL·min·kg with DIA and DP, respectively, which were 10% and…

INTRODUCTION: Physical inactivity is associated with increased risk for morbidity and mortality and contributes to health care costs. Although data supporting the secondary preventive benefits of being physically active continues to grow, there is limited data on the prevalence of sufficient volume of leisure-time physical activity among individuals diagnosed with chronic disease. PURPOSE: To describe the association between select chronic diseases and the prevalence of sufficient volume of aerobic leisure-time physical activity to achieve substantial health benefits (i.e., ≥150 min·wk) among adults in the United States. METHODS: Self-reported leisure-time physical activity (LTPA) and history of select chronic diseases were obtained from a nationally representative sample of noninstitutionalized civilian adults 18 yr or older in the United States who participated in the 2014 National Health Interview Survey (n = 36,697). RESULTS: Among all adults, the prevalence of sufficient volume of aerobic LTPA was 50.1% ± 0.5% (mean ± standard error). This prevalence was inversely related to…

PURPOSE: This study aimed to compare physical activity estimates across different accelerometer wear locations, wear time protocols, and data processing techniques. METHODS: A convenience sample of middle-age to older women wore a GT3X+ accelerometer at the wrist and hip for 7 d. Physical activity estimates were calculated using three data processing techniques: single-axis cut points, raw vector magnitude thresholds, and machine learning algorithms applied to the raw data from the three axes. Daily estimates were compared for the 321 women using generalized estimating equations. RESULTS: A total of 1420 d were analyzed. Compliance rates for the hip versus wrist location only varied by 2.7%. All differences between techniques, wear locations, and wear time protocols were statistically different (P < 0.05). Mean minutes per day in physical activity varied from 22 to 67 depending on location and method. On the hip, the 1952-count cut point found at least 150 min·wk of physical activity in 22% of participants, raw vector magnitude found 32%, and the machine-learned algorithm found 74%…

INTRODUCTION: The purpose of this study was to identify unique organized sport trajectories from early childhood to late adolescence in an Australian pregnancy cohort, the Raine Study. METHODS: Participation in organized sport was assessed at ages 5, 8, 10, 14, and 17 yr. Physical activity, body composition, and self-rated physical and mental health were assessed at the age of 20 yr. Latent class analysis was used to identify patterns of sport participation. To assess the internal validity of the trajectory classes, differences in health characteristics between trajectories were analyzed using generalized linear models. RESULTS: For girls, three trajectory classes were identified: consistent sport participators (47.5%), sport dropouts (34.3%), and sport nonparticipators (18.1%). For boys, three trajectory classes were identified: consistent sport participators (55.2%), sport dropouts (36.9%), and sport joiners (8.1%). For girls, there were overall differences across trajectory classes in lean body mass (P = 0.003), lean mass index (P = 0.06), and physical health (P = 0.004). For…

: Aerobic exercise training and, to a lesser degree, dynamic resistance training, are recommended to lower blood pressure (BP) among adults with hypertension. Yet the combined influence of these exercise modalities, termed concurrent exercise training (CET), on resting BP is unclear. PURPOSE: This study aimed to meta-analyze the literature to determine the efficacy of CET as antihypertensive therapy. METHODS: Electronic databases were searched for trials that included the following: adults (>19 yr), controlled CET interventions, and BP measured pre- and postintervention. Study quality was assessed with a modified Downs and Black Checklist. Analyses incorporated random-effects assumptions. RESULTS: Sixty-eight trials yielded 76 interventions. Subjects (N = 4110) were middle- to older-age (55.8 ± 14.4 yr), were overweight (28.0 ± 3.6 kg·m), and had prehypertension (systolic BP [SBP]/diastolic BP [DBP] = 134.6 ± 10.9/80.7 ± 7.5 mm Hg). CET was performed at moderate intensity (aerobic = 55% maximal oxygen consumption, resistance = 60% one-repetition maximum), 2.9 ± 0.7 d·wk for 58.3 ±…

The repeated intense stimulation of skeletal muscle rapidly decreases its force- and motion-generating capacity. This type of fatigue can be temporally correlated with the accumulation of metabolic by-products, including phosphate (Pi) and protons (H). Experiments on skinned single muscle fibers demonstrate that elevated concentrations of these ions can reduce maximal isometric force, unloaded shortening velocity, and peak power, providing strong evidence for a causative role in the fatigue process. This seems to be due, in part, to their direct effect on muscle's molecular motor, myosin, because in assays using isolated proteins, these ions directly inhibit myosin's ability to move actin. Indeed, recent work using a single molecule laser trap assay has revealed the specific steps in the crossbridge cycle affected by these ions. In addition to their direct effects, these ions also indirectly affect myosin by decreasing the sensitivity of the myofilaments to calcium, primarily by altering the ability of the muscle regulatory proteins, troponin and tropomyosin, to govern myosin…

PURPOSE: This randomized controlled trial compared the effects of resistance training (RT) and RT with instability (RTI) on the timed up and go test (TUG), on-medication Unified Parkinson's Disease Rating Scale part III motor subscale score (UPDRS-III), Montreal Cognitive Assessment (MoCA) score, Parkinson's Disease Questionnaire (PDQ-39) score, and muscle strength in the leg press exercise (one-repetition maximum) of patients with Parkinson's disease (PD). METHODS: Thirty-nine patients with moderate to severe PD were randomly assigned to a nonexercising control group (C), RT group, and RTI group. The RT and RTI groups performed progressive RT twice a week for 12 wk. However, only the RTI group used high motor complexity exercises (i.e., progressive RT with unstable devices), for example, half squat exercise on the BOSU® device. The primary outcome was mobility (TUG). The secondary outcomes were on-medication motor signs (UPDRS-III), cognitive impairment (MoCA), quality of life (PDQ-39), and muscle strength (one-repetition maximum). RESULTS: There were no differences between RTI and…

PURPOSE: American football athletes are exposed to subconcussive impacts over the course of the season resulting in elevations in serum neurofilament light (NFL), a biomarker of axonal injury. Docosahexaenoic acid (DHA) has been reported to reduce axonal trauma associated with traumatic brain injury in rodent models. However, the optimal dose in American football athletes is unknown. This study examined the effect of differing doses of DHA on serum NFL over the course of a season of American football. METHODS: In a randomized, double-blind, placebo-controlled, parallel design, 81 National Collegiate Athletic Association Division I American football athletes were assigned to ingest either 2, 4, 6 g·d of DHA or placebo. Blood was sampled at specific times over the course of 189 d, coincident with changes in intensity, hours of contact, and likely changes in head impacts. Standardized magnitude-based inference was used to define outcomes. RESULTS: DHA supplementation increased plasma DHA in a dose-dependent manner (2 g·d: mean difference from baseline; ±90% CL; 2 g·d: 1.3; ±0.6; 4 g·d:…

PURPOSE: This study investigated the relationship between aerobic and muscular fitness with working memory and academic achievement in preadolescent children. METHODS: Seventy-nine 9- to 11-yr-old children completed an aerobic fitness assessment using a graded exercise test; a muscular fitness assessment consisting of upper body, lower body, and core exercises; a serial n-back task to assess working memory; and an academic achievement test of mathematics and reading. RESULTS: Hierarchical regression analyses indicated that after controlling for demographic variables (age, sex, grade, IQ, socioeconomic status), aerobic fitness was associated with greater response accuracy and d' in the 2-back condition and increased mathematic performance in algebraic functions. Muscular fitness was associated with increased response accuracy and d', and longer reaction time in the 2-back condition. Further, the associations of muscular fitness with response accuracy and d' in the 2-back condition were independent of aerobic fitness. CONCLUSION: The current findings suggest the differential…

PURPOSE: Chronic quadriceps dysfunction has been implicated as a contributor to knee osteoarthritis (OA) development after anterior cruciate ligament reconstruction (ACLR). This dysfunction potentially leads to impulsive/high-rate loading during gait, thus accelerating cartilage degradation. The purpose of this study was to examine relationships between several indices of quadriceps function and gait biomechanics linked to knee OA development in individuals with ACLR. METHODS: Gait biomechanics and quadriceps function were assessed in 39 individuals with ACLR. Indices of quadriceps function included isometric peak torque and rate of torque development (RTD), isokinetic peak torque and power, and the central activation ratio. Gait biomechanics included the peak vertical ground reaction force and loading rate, and the heel strike transient (HST) magnitude and loading rate. RESULTS: Isometric peak torque was not associated with any of the gait biomechanical variables. However, greater RTD was associated with lesser peak vertical ground reaction force linear (r = -0.490, P = 0.003) and…

PURPOSE: High school cross-country runners have a high incidence of injury, particularly at the shin and knee. An increased step rate during running has been shown to reduce impact forces and loading of the lower extremity joints. The purpose of this prospective study was to examine step rate as a risk factor for injury occurrence. MATERIALS AND METHODS: Running step rates of 68 healthy high school cross-country runners (47 females; 21 males; mean age 16.2 ± 1.3 yr) were assessed at a fixed speed (3.3 ± 0.0 m·s) and self-selected speed (mean, 3.8 ± 0.5 m·s). Runners were prospectively followed during the interscholastic season to determine athletic exposures, occurrences of shin injury and anterior knee pain (AKP), and days lost to injury. RESULTS: During the season, 19.1% of runners experienced a shin injury and 4.4% experienced AKP. Most injuries (63.6%) were classified as minor (1-7 d lost). At the fixed speed, runners in the lowest tertile of step rate (≤164 steps per minute) were more likely (odds ratio, 6.67; 95% confidence interval, 1.2-36.7; P = 0.03) to experience a shin…

PURPOSE: The aims of this study were to investigate the age-related changes in fatty replacement and cross-sectional area (CSA) of cervical, thoracic, and lumbar paraspinal muscles versus leg muscles in healthy adults and to test for association between muscle fat fraction and lifestyle factors. METHODS: Fifty-three healthy adults (24-76 yr) were included. Dixon magnetic resonance imaging technique was used to determine CSA and to quantify the fat fraction of paraspinal and leg muscles. Muscle CSA and fat fractions were tested for association with age and muscle strength. The fat fractions were also tested for association with sex, body mass index (BMI), physical activity, and lower back pain. RESULTS: Both paraspinal and leg fat fractions correlated directly with age (P < 0.0001). At all ages, fat fraction was higher in paraspinal than leg muscles. The age-related increase in fat fraction was higher in paraspinal muscles than leg muscles (P < 0.0001). The CSA of the muscles did not correlate with age. Knee extension strength correlated with fat fraction (P < 0.05), and the muscle…

PURPOSE: With the increasing popularity of Hatha yoga, it is important to understand the energy cost and METs of yoga practice within the context of the American College of Sports Medicine (ACSM) and the American Heart Association (AHA) physical activity guidelines. METHODS: This systematic review evaluated the energy cost and metabolic intensity of yoga practice including yoga asanas (poses/postures) and pranayamas (breath exercises) measured by indirect calorimetry. The English-speaking literature was surveyed via PubMed using the general terms "yoga" and "energy expenditure" with no date limitations. RESULTS: Thirteen manuscripts were initially identified with an additional four located from review of manuscript references. Of the 17 studies, 10 evaluated the energy cost and METs of full yoga sessions or flow through Surya Namaskar (sun salutations), eight of individual asanas, and five of pranayamas. METs for yoga practice averaged 3.3 ± 1.6 (range = 1.83-7.4 METs) and 2.9 ± 0.8 METs when one outlier (i.e., 7.4 METs for Surya Namaskar) was omitted. METs for individual asanas…

Acute skeletal muscle fatigue develops in situations with high energy demand and large dependency on anaerobic metabolism. When fatigued, muscles become weaker and slower, and two end products of anaerobic metabolism, H+ and inorganic phosphate ions (Pi), have received most attention as causes of the impaired contractility in fatigue (1). In particular, the increase in H+ (i.e., reduced intracellular pH [pHi] or acidosis) is believed to play a central role in skeletal muscle fatigue. However, this belief has been challenged, and here I present experimental evidence that speaks against acidosis as a central factor underlying the impaired contractile function in fatigued mammalian muscle. Any factor that directly causes fatigue-induced contractile impairments should change in parallel with the decline in contractile function. Many studies have shown a good temporal correlation between the extent of acidosis and the decrease in contractile function (5,10). However, there are situations where this correlation is missing. For instance, a study of fatigue in human calf muscle showed…

INTRODUCTION: The aim of this study was to describe maximal fat oxidation (MFO) rates in an athletic population. METHOD: In total, 1121 athletes (933 males and 188 females), from a variety of sports and competitive level, undertook a graded exercise test on a treadmill in a fasted state (≥5 h fasted). Rates of fat oxidation were determined using indirect calorimetry. RESULTS: The average MFO was 0.59 ± 0.18 g·min, ranging from 0.17 to 1.27 g·min. Maximal rates occurred at an average exercise intensity of 49.3% ± 14.8% V˙O2max, ranging from 22.6% to 88.8% V˙O2max. In absolute terms, male athletes had significantly higher MFO compared with females (0.61 and 0.50 g·min, respectively, P < 0.001). Expressed relative to fat-free mass (FFM), MFO were higher in the females compared with males (MFO/FFM: 11.0 and 10.0 mg·kg·FFM·min, respectively, P < 0.001). Soccer players had the highest MFO/FFM (10.8 mg·kg·FFM·min), ranging from 4.1 to 20.5 mg·kg·FFM·min, whereas American Football players displayed the lowest rates of MFO/FFM (9.2 mg·kg·FFM·min). In all athletes, and when separated by…

PURPOSE: The aim of this study was to explore the relationship between muscle fiber conduction velocity (MFCV), fiber type composition, and power performance in participants with different training background. METHODS: Thirty-eight young males with different training background participated: sedentary (n = 10), endurance runners (n = 9), power trained (n = 10), and strength trained (n = 9). They performed maximal countermovement jumps (CMJ) and maximal isometric leg press for the measurement of the rate of force development (RFD). Resting vastus lateralis MFCV was measured with intramuscular microelectrodes on a different occasion, whereas muscle fiber type and cross-sectional area (CSA) of vastus lateralis were evaluated through muscle biopsies 1wk later. RESULTS: MFCV, CMJ power, RFD, and % CSA of type II and type IIx fibers were higher for the power-trained group (P < 0.001). No difference was found between sedentary participants and endurance runners in these variables, but both of these groups performed worse than strength/power participants. Close correlations were found…

PURPOSES: Physical activity (PA) is important for the development of children with disabilities, but rarely does this population meet the recommended standards. Schools are salient locations for PA, but little is known about how specific school settings affect the PA of children with diverse disabilities. We assessed PA and sedentary time (ST) of children with disabilities in three school settings (physical education, recess, lunchtime). METHODS: Participants included 259 children from 13 Hong Kong special schools for five primary disabilities: visual impairments, hearing impairments, physical disabilities, intellectual disabilities, and social development problems. Children wore accelerometers at school for 3 d, and the time (min and %) they engaged in moderate-to-vigorous PA (MVPA) and ST was extracted for each school setting by sex. Analyses included multiple linear mixed models to determine differences in MVPA and ST by sex across disability types, adjusting for body mass index, grade level, and duration in each setting. RESULTS: Overall, children spent 70% of their day at…

PURPOSE: Skeletal muscle capillarization plays a key role in oxygen and nutrient delivery to muscle. The loss of muscle mass with aging and the concept of anabolic resistance have been, at least partly, attributed to changes in skeletal muscle capillary structure and function. We aimed to compare skeletal muscle capillarization between young and older men and evaluate whether resistance-type exercise training increases muscle capillarization in older men. METHODS: Muscle biopsies were obtained from the vastus lateralis of healthy young (n = 14, 26 ± 2 yr) and older (n = 16, 72 ± 1 yr) adult men, with biopsies before and after 12 wk of resistance-type exercise training in the older subjects. Immunohistochemistry was used to assess skeletal muscle fiber size, capillary contacts (CC) per muscle fiber, and the capillary-to-fiber perimeter exchange (CFPE) index in type I and II muscle fibers. RESULTS: Type II muscle fibers were smaller in old versus young (4507 ± 268 vs 6084 ± 497 μm, respectively, P = 0.007). Type I and type II muscle fiber CC and CFPE index were smaller in old compared…

PURPOSE: Physical activity is associated with decreased adiposity-related inflammation in adults. Whether this association is independent of central obesity is unknown but important for understanding the mechanisms associated with reducing cardiometabolic disease risk through physical activity. This study examined whether associations of physical activity and obesity-related inflammatory markers were independent of central adiposity. METHODS: Between 2002 and 2005, 1970 participants from the Multi-Ethnic Study of Atherosclerosis completed detailed health history and physical activity questionnaires, underwent physical measurements including computed tomography to quantify abdominal visceral and subcutaneous fat, and measurements of adiponectin, leptin, interleukin-6, tumor necrosis factor-alpha, and resistin. Statistical analyses included analysis of covariance and multivariable-adjusted regression. RESULTS: The mean (range) age of participants was 64.7 (55-84) yr and 50% were women. After adjustment for age and sex, and compared with the lowest quartile, inflammatory markers in the…

PURPOSE: We tested the effectiveness of a 2-wk motivational self-talk (MST) intervention-specific to heat tolerance-on endurance capacity and cognitive function in the heat. METHODS: Eighteen trained male (n = 14) and female (n = 4) cyclists randomly received 2 wk of MST training (n = 9) or a control regimen (CON, n = 9). The experimental protocol was a PRE/POST design consisting of 30 min of cycling at 60% peak power output (PPO) in the heat (35°C, 50% relative humidity, ~3.0 m·s airflow), a 30-min rest period, followed by a time to exhaustion (TTE) test at 80% PPO, and an identical rest period. Executive function, reaction time, and working memory were tested at baseline and each rest period. Key measures included TTE, speed and accuracy on the cognitive tests, rectal temperature, HR, oxygen consumption, and RPE. RESULTS: Group (MST vs CON) × test (PRE vs POST) × time repeated-measures ANOVA revealed that MST significantly increased TTE from PRE (487 ± 173 s) to POST (679 ± 251 s, P = 0.021) concurrent with a higher terminating rectal temperature (PRE, 38.5°C ± 0.2°C; POST, 38.8°C…

PURPOSE: High-intensity interval training (HIIT) is documented to yield effective improvements in the cardiovascular system and be an excellent strategy for healthy aging. However, it is not determined how age may affect the training response of key components of aerobic endurance. METHODS: We recruited 72 males (mean ± SD, weight = 84.9 ± 12.9 kg, height = 180.4 ± 5.8 cm) and 22 females (weight = 76.0 ± 17.2 kg, height = 171.2 ± 6.7 cm) from 20 to 70+ yr with a training status typical for their age group and divided them into six decade cohorts. The participants followed supervised training with a targeted intensity of 90%-95% of maximal HR (HRmax) three times a week for 8 wk. RESULTS: After HIIT, all age groups increased (P < 0.001-P = 0.004) maximal oxygen consumption (V˙O2max) with 0.39 ± 0.20 (20-29 yr), 0.28 ± 0.21 (30-39 yr), 0.36 ± 0.08 (40-49 yr), 0.34 ± 0.27 (50-59 yr), 0.33 ± 0.23 (60-69 yr), and 0.34 ± 0.14 (70+ yr) L·min, respectively. These 9%-13% improvements were not significantly different between the age groups. In contrast to age, the percentage improvements after…

PURPOSE: This study aimed to determine whether higher levels of physical activity (PA) and less sedentary behavior (SB) are associated with less inflammation, indicated by inflammatory and hemostatic biomarkers, in older men. METHODS: A cross-sectional study of 1139 men, from the British Regional Heart Study (mean ± SD age = 78 ± 5 yr), and longitudinal analyses of 490 men with two PA measures 1 yr apart were used in this study. Single fasting venous blood samples were analyzed for several biomarkers. PA and SB were measured using ActiGraph GT3X accelerometers. Total time and time spent in bouts of moderate to vigorous PA (MVPA), light PA, and SB were derived. Linear regression analyses were used to investigate associations. RESULTS: Cross-sectionally, higher total PA, daily steps, and MVPA were all associated with lower levels of interleukin 6 (IL-6), C-reactive protein (CRP), tissue plasminogen activator (tPA), von Willebrand factor (vWF), and D-dimer, whereas higher levels of SB were associated with higher levels of IL-6, CRP, and tPA. Each additional 10 min of MVPA was…

INTRODUCTION: Running with a forefoot strike (FFS) pattern has been suggested to reduce the risk of overuse running injuries, due to a reduced vertical load rate compared with rearfoot strike (RFS) running. However, resultant load rate has been reported to be similar between foot strikes when running in traditional shoes, leading to questions regarding the value of running with a FFS. The influence of minimal footwear on the resultant load rate has not been considered. This study aimed to compare component and resultant instantaneous loading rate (ILR) between runners with different foot strike patterns in their habitual footwear conditions. METHODS: Twenty-nine injury-free participants (22 men, seven women) ran at 3.13 m·s along a 30-m runway, with their habitual foot strike and footwear condition. Ground reaction force data were collected. Peak ILR values were compared between three conditions; those who habitually run with an RFS in standard shoes, with an FFS in standard shoes, and with an FFS in minimal shoes. RESULTS: Peak resultant, vertical, lateral, and medial ILR were…

PURPOSE: The main purpose of this study was to examine the accuracy of wristband activity monitors on measuring step counts at prescribed speeds on a treadmill and under short bouts of common daily activities. METHODS: Thirty healthy young adults wore three wristband activity monitors on both wrists while walking or jogging on a treadmill at different speeds (54, 80, 107, and 134 m·min) and performing six different common daily activities for 5 min each. The monitors included the Fitbit Flex, the Garmin Vivofit, and the Jawbone UP. The common daily activity conditions included two sitting activities (playing a tablet computer game and folding laundry), two walking activities (pushing a stroller, carrying a bag), and two stair climbing activities (down and up). Absolute percentage error (APE) scores were computed to examine the accuracy between actual observed steps and monitor-detected steps. RESULTS: Under the treadmill condition, the APE ranged between 1.5% and 9.6%. Accuracy was improved at faster speeds (134 m·min) for all the monitors (APE < 2.5%). In the common daily activity…

PURPOSE: The objective of this study is to determine whether childhood muscular fitness phenotypes (strength, endurance, and power) are independently associated with adult metabolic syndrome (MetS). METHODS: We conducted a longitudinal study including 737 participants who had muscular fitness measures in 1985 when age 9, 12, or 15 yr and attended follow-up in young adulthood 20 yr later when measures of MetS were collected. Childhood measures of muscular fitness included strength (right and left grip, leg, and shoulder extension and flexion), endurance (number of push-ups in 30 s), and power (distance of a standing long jump). A muscular fitness score was created using all individual muscular fitness phenotypes. In adulthood, waist circumference, blood pressure, HDL cholesterol, triglycerides, and glucose were measured. Adult outcomes were MetS defined using the harmonized definition and a continuous MetS risk score. RESULTS: Participants with childhood muscular strength, muscular power, and combined muscular fitness score in the highest third had significantly lower relative risk…

PURPOSE: To investigate differences in anterior cruciate ligament-reconstructed (ACLR) and healthy individuals in terms of the magnitude of the tibiofemoral contact forces, as well as the relative muscle and external load contributions to those contact forces, during walking, running, and sidestepping gait tasks. METHODS: A computational EMG-driven neuromusculoskeletal model was used to estimate the muscle and tibiofemoral contact forces in those with single-bundle combined semitendinosus and gracilis tendon autograft ACLR (n = 104, 29.7 ± 6.5 yr, 78.1 ± 14.4 kg) and healthy controls (n = 60, 27.5 ± 5.4 yr, 67.8 ± 14.0 kg) during walking (1.4 ± 0.2 m·s), running (4.5 ± 0.5 m·s) and sidestepping (3.7 ± 0.6 m·s). Within the computational model, the semitendinosus of ACLR participants was adjusted to account for literature reported strength deficits and morphological changes subsequent to autograft harvesting. RESULTS: ACLR had smaller maximum total and medial tibiofemoral contact forces (~80% of control values, scaled to bodyweight) during the different gait tasks. Compared with…

INTRODUCTION: Skeletal muscle carnosine content can be increased through β-alanine (BA) supplementation, but the maximum increase achievable with supplementation is unknown. No study has investigated the effects of prolonged supplementation on carnosine-related genes or exercise capacity. PURPOSE: This study aimed to investigate the effects of 24 wk of BA supplementation on muscle carnosine content, gene expression, and high-intensity cycling capacity (CCT110%). METHODS: Twenty-five active males were supplemented with 6.4 g·d of sustained release BA or placebo for a 24 wk period. Every 4 wk participants provided a muscle biopsy and performed the CCT110%. Biopsies were analyzed for muscle carnosine content and gene expression (CARNS, TauT, ABAT, CNDP2, PHT1, PEPT2, and PAT1). RESULTS: Carnosine content was increased from baseline at every time point in BA (all P < 0.0001; week 4 = +11.37 ± 7.03 mmol·kg dm, week 8 = +13.88 ± 7.84 mmol·kg dm, week 12 = +16.95 ± 8.54 mmol·kg dm, week 16 = +17.63 ± 8.42 mmol·kg dm, week 20 = +21.20 ± 7.86 mmol·kg dm, and week 24 = +20.15 ± 7.63 mmol·kg…

PURPOSE: Supplementation with dietary forms of vitamin D is commonplace in clinical medicine, elite athletic cohorts, and the general population, yet the response of all major vitamin D metabolites to high doses of vitamin D is poorly characterized. We aimed to identify the responses of all major vitamin D metabolites to moderate- and high-dose supplemental vitamin D3. METHODS: A repeated-measures design was implemented in which 46 elite professional European athletes were block randomized based on their basal 25[OH]D concentration into two treatment groups. Athletes received either 35,000 or 70,000 IU·wk vitamin D3 for 12 wk, and 42 athletes completed the trial. Blood samples were collected for 18 wk to monitor the response to supplementation and withdrawal from supplementation. RESULTS: Both doses led to significant increases in serum 25[OH]D, and 1,25[OH]2D3. 70,000 IU·wk also resulted in a significant increase of the metabolite 24,25[OH]2D at weeks 6 and 12 that persisted after supplementation withdrawal at week 18, despite a marked decrease in 1,25[OH]2D3. Intact parathyroid…

PURPOSE: This study aimed to compare the effects of three different high-intensity training (HIT) models, balanced for total load but differing in training plan progression, on endurance adaptations. METHODS: Sixty-three cyclists (peak oxygen uptake (V˙O2peak) 61.3 ± 5.8 mL·kg·min) were randomized to three training groups and instructed to follow a 12-wk training program consisting of 24 interval sessions, a high volume of low-intensity training, and laboratory testing. The increasing HIT group (n = 23) performed interval training as 4 × 16 min in weeks 1-4, 4 × 8 min in weeks 5-8, and 4 × 4 min in weeks 9-12. The decreasing HIT group (n = 20) performed interval sessions in the opposite mesocycle order as the increasing HIT group, and the mixed HIT group (n = 20) performed the interval prescriptions in a mixed distribution in all mesocycles. Interval sessions were prescribed as maximal session efforts and executed at mean values 4.7, 9.2, and 12.7 mmol·L blood lactate in 4 × 16-, 4 × 8-, and 4 × 4-min sessions, respectively (P < 0.001). Pre- and postintervention, cyclists were…

INTRODUCTION: High-intensity interval training (HIT) exercise has gained much interest in both performance and recreational sports. This study aims to compare the effect of HIT versus continuous (CONT) exercise with regard to changes of circulating T cells and progenitor cells. METHODS: Subjects (n = 23) completed an HIT test and an isocaloric CONT test. Blood samples were collected before, immediately after, and 3 and 24 h postexercise for the assessment of low differentiated (CD3CD28CD57), highly differentiated T cells (CD3CD28CD57), regulatory T cells (Tregs) (CD4CD25CD127), hematopoietic progenitor cells (CD45CD34), and endothelial progenitor cells (CD45CD34KDR) by flow cytometry. The detection of apoptosis was performed by using labeling with annexin V. To analyze potential mechanisms affecting T cells, several hormones and metabolites were analyzed. RESULTS: Both exercise tests induced an increase of catecholamines, cortisol, and thiobarbituric acid-reactive substances (P < 0.05). CONT induced a higher increase of apoptosis in low differentiated T cells compared with the HIT…

Standardizing a dual x-ray absorptiometry (DXA) protocol is thought to provide a reliable measurement of body composition. PURPOSE: We investigated the effects of manipulating muscle glycogen and creatine content independently and additively on DXA estimates of lean mass. METHOD: Eighteen well-trained male cyclists undertook a parallel group application of creatine loading (n = 9) (20 g·d for 5 d loading; 3 g·d maintenance) or placebo (n = 9) with crossover application of glycogen loading (12 v 6 g·kg BM per day for 48 h) as part of a larger study involving a glycogen-depleting exercise protocol. Body composition, total body water, muscle glycogen and creatine content were assessed via DXA, bioelectrical impedance spectroscopy and standard biopsy techniques. Changes in the mean were assessed using the following effect-size scale: >0.2 small, >0.6, moderate, >1.2 large and compared with the threshold for the smallest worthwhile effect of the treatment. RESULTS: Glycogen loading, both with and without creatine loading, resulted in substantial increases in estimates of lean body mass…

PURPOSE: This study aimed to catalog the relationships between step-based accelerometer metrics indicative of physical activity volume (steps per day, adjusted to a pedometer scale), intensity (mean steps per minute from the highest, not necessarily consecutive, minutes in a day; peak 30-min cadence), and sedentary behavior (percent time at zero cadence relative to wear time; %TZC) and cardiometabolic risk factors. METHODS: We analyzed data from 3388 participants, 20+ yr old, in the 2005-2006 National Health and Nutrition Examination Survey with ≥1 valid day of accelerometer data and at least some data on weight, body mass index, waist circumference, systolic and diastolic blood pressure, glucose, insulin, HDL cholesterol, triglycerides, and/or glycohemoglobin. Linear trends were evaluated for cardiometabolic variables, adjusted for age and race, across quintiles of steps per day, peak 30-min cadence, and %TZC. RESULTS: Median steps per day ranged from 2247 to 12,334 steps per day for men and from 1755 to 9824 steps per day for women, and median peak 30-min cadence ranged from 48.1…

PURPOSE: The objective of this study is to test the feasibility and impact of a 10-wk after-school exercise program for children with attention deficit hyperactivity disorder and/or disruptive behavior disorders living in an urban poor community. METHODS: Children were randomized to an exercise program (n = 19) or a comparable but sedentary attention control program (n = 16). Cognitive and behavioral outcomes were collected pre-/posttest. Intent-to-treat mixed models tested group-time and group-time-attendance interactions. Effect sizes were calculated within and between groups. RESULTS: Feasibility was evidenced by 86% retention, 60% attendance, and average 75% maximum HR. Group-time results were null on the primary outcome, parent-reported executive function. Among secondary outcomes, between-group effect sizes favored exercise on hyperactive symptoms (d = 0.47) and verbal working memory (d = 0.26), and controls on visuospatial working memory (d = -0.21) and oppositional defiant symptoms (d = -0.37). In each group, within-group effect sizes were moderate to large on most outcomes…

INTRODUCTION: For more than three decades, muscle biologists have been fascinated by reactive oxygen species (ROS) generated in exercising muscle and the potential role that ROS may play in fatigue. METHODS: Reports in the peer-reviewed literature were analyzed and published findings integrated to synthesize an overview of ROS as agents of fatigue. RESULTS: Muscle tissue contains multiple sources of ROS, and specific ROS molecules have been detected in muscle, including superoxide anions, hydrogen peroxide, and hydroxyl radicals. These species are present throughout the tissue, i.e., myofiber organelles and cytosol, extracellular space, and intravascular compartment, and ROS concentrations increase during strenuous contractions. Direct ROS exposure evokes many of the same changes that occur in muscle during fatigue, suggesting a possible relationship. The hypothesis that ROS play a causal role in fatigue has been tested extensively, a large body of data have been compiled, and the once-controversial verdict is now in: ROS accumulation in working muscle clearly contributes to the…

DESCRIPTION This book discusses the continuity of the fascial planes to provide an understanding of the function of the fascia as a connection between muscles, nerves, and blood vessels. A wealth of illustrative material supports the text, and an accompanying website provides instructional videos. PURPOSE The purpose of this book is to provide a photographic understanding of the connections that exist between fascia, muscles, and nerves and, therefore, support the work of manual medicine practitioners. The book stresses the coordination of muscular activity in the body. This is a worthy addition to resources for manual practitioners. AUDIENCE The primary audience is anyone practicing musculoskeletal medicine and using manual procedures, such as physical therapists, massage therapists, chiropractors, osteopaths, and physiatrists, among others. It will be most helpful for students in these disciplines since it so nicely illustrates the actual appearance and location of the involved structures. Carla Stecco is an accomplished orthopedic surgeon and well known in the field. FEATURES The…

PURPOSE: Ischemic preconditioning (IPC) has been shown to improve performance of exercises lasting 10-90 s (anaerobic) and more than 90 s (aerobic). However, its effect on repeated sprint performance has been controversial, placebo effect has not been adequately controlled, and nocebo effect has not been avoided. Thus, the IPC effect on repeated sprint performance was investigated using a swimming task and controlling placebo/nocebo effects. METHODS: Short-distance university swimmers were randomized to two groups. One group (n = 15, 24 ± 1 yr [mean ± SEM]) was exposed to IPC (ischemia cycles lasted 5 min) and control (CT) (no ischemia); another (n = 15, 24 ± 1 yr) to a placebo intervention (SHAM) (ischemia cycles lasted 1 min) and CT. Seven subjects crossed over groups. Subjects were informed IPC and SHAM would improve performance compared with CT and would be harmless despite circulatory occlusion sensations. The swimming task consisted of six 50-m all-out efforts repeated every 3 min. RESULTS: IPC, in contrast with SHAM, reduced worst sprint time (IPC, 35.21 ± 0.73 vs CT, 36.53 ±…

PURPOSE: This study aimed to determine the association between injury history at enrollment and incident lower extremity (LE) injury during cadet basic training among first-year military cadets. METHODS: Medically treated LE injuries during cadet basic training documented in the Defense Medical Surveillance System were ascertained in a prospective cohort study of three large US military academies from 2005 to 2008. Both acute injuries (International Classification of Disease, Ninth Revision, codes in the 800-900s, including fracture, dislocations, and sprains/strains) and injury-related musculoskeletal injuries (International Classification of Disease, Ninth Revision, codes in the 700s, including inflammation and pain, joint derangement, stress fracture, sprain/strain/rupture, and dislocation) were included. Risk ratio (RR) and 95% confidence interval (CI) were computed using multivariate log-binomial models stratified by gender. RESULTS: During basic training, there were 1438 medically treated acute and 1719 musculoskeletal-related LE injuries in the 9811 cadets. The most frequent…

PURPOSE: Recent studies have reported ischemic preconditioning (IPC) can acutely improve endurance exercise performance in athletes. However, placebo and nocebo effects have not been sufficiently controlled, and the effect on aerobic metabolism parameters that determine endurance performance (e.g., oxygen cost of running, lactate threshold, and maximal oxygen uptake [V˙O2max]) has been equivocal. Thus, we circumvented limitations from previous studies to test the effect of IPC on aerobic metabolism parameters and endurance performance in well-trained runners. METHODS: Eighteen runners (14 men/4 women) were submitted to three interventions, in random order: IPC; sham intervention (SHAM); and resting control (CT). Subjects were told both IPC and SHAM would improve performance compared to CT (i.e., similar placebo induction), and IPC would be harmless despite circulatory occlusion sensations (i.e., nocebo avoidance). Next, pulmonary ventilation and gas exchange, blood lactate concentration, and perceived effort were measured during a discontinuous incremental test on a treadmill. Then,…

PURPOSE: Recent research indicates that a concussion increases the risk of musculoskeletal injury. Neuromuscular changes after concussion might contribute to the increased risk of injury. Many studies have examined gait postconcussion, but few studies have examined more demanding tasks. This study compared changes in stiffness across the lower extremity, a measure of neuromuscular function, during a jump-landing task in athletes with a concussion (CONC) to uninjured athletes (UNINJ). METHODS: Division I football players (13 CONC and 26 UNINJ) were tested pre- and postseason. A motion capture system recorded subjects jumping on one limb from a 25.4-cm step onto a force plate. Hip, knee, and ankle joint stiffness were calculated from initial contact to peak joint flexion using the regression line slopes of the joint moment versus the joint angle plots. Leg stiffness was (peak vertical ground reaction force [PVGRF]/lower extremity vertical displacement) from initial contact to peak vertical ground reaction force. All stiffness values were normalized to body weight. Values from both…

INTRODUCTION: Barefoot locomotion is widely believed to be beneficial for motor development and biomechanics but are implied to be responsible for foot pathologies and running-related injuries. Although most of available studies focused on acute effects of barefoot running and walking little is known regarding the effects of long-term barefoot versus shod locomotion. The purpose of this study was to systematically review the literature to evaluate current evidence of habitual barefoot (HB) versus habitual shod locomotion on foot anthropometrics, biomechanics, motor performance, and pathologies. METHODS: Four electronic databases were searched using terms related to habitually barefoot locomotion. Relevant studies were identified based on title, abstract, and full text, and a forward (citation tracking) and backward (references) search was performed. Risk of bias was assessed, data pooling, and meta-analysis (random effects model) performed and finally levels of evidence determined. RESULTS: Fifteen studies with 8399 participants were included. Limited evidence was found for a…

INTRODUCTION: There are limited nonlaboratory soccer head impact biomechanics data. This is surprising given soccer's global popularity. Epidemiological data suggest that female college soccer players are at a greater concussion injury risk than their male counterparts. Therefore, the purposes of our study were to quantify head impact frequency and magnitude during women's soccer practices and games in the National Collegiate Athletic Association and to characterize these data across event type, playing position, year on the team, and segment of game (first and second halves). METHODS: Head impact biomechanics were collected from female college soccer players (n = 22; mean ± SD age = 19.1 ± 0.1 yr, height = 168.0 ± 3.5 cm, mass = 63.7 ± 6.0 kg). We employed a helmetless head impact measurement device (X2 Biosystems xPatch) before each competition and practice across a single season. Peak linear and rotational accelerations were categorized based on impact magnitude and subsequently analyzed using appropriate nonparametric analyses. RESULTS: Overall, women's college soccer players…

PURPOSE: Breast cancer-related lymphedema is a common and debilitating side effect of cancer treatment. This randomized trial compared the effect of progressive resistance- or aerobic-based exercise on breast cancer-related lymphedema extent and severity, as well as participants' muscular strength and endurance, aerobic fitness, body composition, upper-body function, and quality of life. METHODS: Women with a clinical diagnosis of stable unilateral, upper-limb lymphedema secondary to breast cancer were randomly allocated to a resistance-based (n = 21) or aerobic-based (n = 20) exercise group (12-wk intervention). Women were assessed preintervention, postintervention, and 12 wk postintervention, with generalized estimating equation models used to compare over time changes in each group's lymphedema (two-tailed P < 0.05). RESULTS: Lymphedema remained stable in both groups (as measured by bioimpedance spectroscopy and circumferences), with no significant differences between groups noted in lymphedema status. There was a significant (P < 0.01) time-group effect for upper-body strength…

PURPOSE: State-of-the-art methods for recognizing human activity using raw data from body-worn accelerometers have primarily been validated with data collected from adults. This study applies a previously available method for activity classification using wrist or ankle accelerometer to data sets collected from both adults and youth. METHODS: An algorithm for detecting activity from wrist-worn accelerometers, originally developed using data from 33 adults, is tested on a data set of 20 youth (age, 13 ± 1.3 yr). The algorithm is also extended by adding new features required to improve performance on the youth data set. Subsequent tests on both the adult and youth data were performed using crossed tests (training on one group and testing on the other) and leave-one-subject-out cross-validation. RESULTS: The new feature set improved overall recognition using wrist data by 2.3% for adults and 5.1% for youth. Leave-one-subject-out cross-validation accuracy performance was 87.0% (wrist) and 94.8% (ankle) for adults, and 91.0% (wrist) and 92.4% (ankle) for youth. Merging the two data sets,…

UNLABELLED: Accurate assessments of both physical activity and sedentary behaviors are crucial to understand the health consequences of movement patterns and to track changes over time and in response to interventions. PURPOSE: The study evaluates the validity of an integrative, machine learning method for processing activity monitor data in relation to a portable metabolic analyzer (Oxycon mobile [OM]) and direct observation (DO). METHODS: Forty-nine adults (age 18-40 yr) each completed 5-min bouts of 15 activities ranging from sedentary to vigorous intensity in a laboratory setting while wearing ActiGraph (AG) on the hip, activPAL on the thigh, and OM. Estimates of energy expenditure (EE) and categorization of activity intensity were obtained from the AG processed with Lyden's sojourn (SOJ) method and from our new sojourns including posture (SIP) method, which integrates output from the AG and activPAL. Classification accuracy and estimates of EE were then compared with criterion measures (OM and DO) using confusion matrices and comparisons of the mean absolute error of…

INTRODUCTION: We have previously shown that protein ingestion before sleep increases overnight muscle protein synthesis rates. Whether prior exercise further augments the muscle protein synthetic response to presleep protein ingestion remains to be established. OBJECTIVE: This study aimed to assess whether resistance-type exercise performed in the evening increases the overnight muscle protein synthetic response to presleep protein ingestion. METHODS: Twenty-four healthy young men were randomly assigned to ingest 30 g intrinsically L-[1-C]-phenylalanine and L-[1-C]-leucine-labeled casein protein before going to sleep with (PRO + EX, n = 12) or without (PRO, n = 12) prior resistance-type exercise performed in the evening. Continuous intravenous L-[ring-H5]-phenylalanine, L-[1-C]-leucine, and L-[ring-H2]-tyrosine infusions were applied. Blood and muscle tissue samples were collected to assess whole-body protein balance, myofibrillar protein synthesis rates, and overnight incorporation of dietary protein-derived amino acids into de novo myofibrillar protein. RESULTS: A total of 57% ±…

INTRODUCTION: This case study reports a range of physiological characteristics in a two-time Tour de France champion. METHODS: After body composition assessment (dual-energy x-ray absorptiometry), two submaximal cycling step tests were performed in ambient (20°C, 40%) and hot and humid (30°C, 60% [HH]) conditions from which measures of gross efficiency (GE), lactate-power landmarks, and heart rate responses were calculated. In addition, thermoregulatory and sweat responses were collected throughout. V˙O2peak and peak power output (PPO) were also identified after a separate ramp test to exhaustion. RESULTS: V˙O2peak and PPO were 5.91 L·min (84 mL·kg·min) and 525 W, respectively, whereas mean GE values were 23.0% and 23.6% for ambient and HH conditions, respectively. In addition to superior GE, power output at 4 mmol·L lactate was higher in HH versus ambient conditions (429.6 vs 419.0 W) supporting anecdotal reports from the participant of good performance in the heat. Peak core and skin temperature, sweat rate, and electrolyte content were higher in HH conditions. Body fat percentage…

PURPOSE: Little is known about whether acute exercise affects signs or symptoms of attention deficit/hyperactivity disorder (ADHD) in adults. This experiment sought to determine the effects of a single bout of moderate-intensity leg cycling exercise on measures of attention, hyperactivity, mood, and motivation to complete mental work in adult men reporting elevated ADHD symptoms. METHODS: A repeated-measures crossover experiment was conducted with 32 adult men (18-33 yr) with symptoms consistent with adult ADHD assessed by the Adult Self-Report Scale V1.1. Measures of attention (continuous performance task and Bakan vigilance task), motivation to perform the mental work (visual analog scale), lower leg physical activity (accelerometry), and mood (Profile of Mood States and Addiction Research Center Inventory amphetamine scale) were measured before and twice after a 20-min seated rest control or exercise condition involving cycling at 65% V˙O2peak. Condition (exercise vs rest) × time (baseline, post 1, and post 2) ANOVA was used to test the hypothesized exercise-induced improvements…

PURPOSE: This study aimed to prospectively investigate the association between isolated and functional lower extremity muscle strength and the risk for noncontact anterior cruciate ligament (ACL) injury in Norwegian female elite handball and football players. METHODS: From 2007 through 2015, premier league players participated in strength testing and were prospectively followed for ACL injury risk. At baseline, we recorded player demographics, playing and ACL injury history, and measured peak concentric isokinetic quadriceps and hamstring torques (60°·s), hamstring-to-quadriceps ratio, isometric hip abduction strength, and one-repetition maximum in a seated leg press. We followed a predefined statistical protocol where we generated five separate logistic regression models, one for each of the proposed strength risk factors and adjusted for confounding factors. New ACL injury was the outcome, using the leg as the unit of analysis. RESULTS: A total of 57 (6.6%) of 867 players (age = 21 ± 4 yr, height = 170 ± 6 cm, body mass = 66 ± 8 kg) suffered from a noncontact ACL injury after…

UNLABELLED: Soldiers often experience negative energy balance during military operations that diminish whole-body protein retention, even when dietary protein is consumed within recommended levels (1.5-2.0 g·kg·d). PURPOSE: The objective of this study is to determine whether providing supplemental nutrition spares whole-body protein by attenuating the level of negative energy balance induced by military training and to assess whether protein balance is differentially influenced by the macronutrient source. METHODS: Soldiers participating in 4-d arctic military training (AMT) (51-km ski march) were randomized to receive three combat rations (CON) (n = 18), three combat rations plus four 250-kcal protein-based bars (PRO, 20 g protein) (n = 28), or three combat rations plus four 250-kcal carbohydrate-based bars daily (CHO, 48 g carbohydrate) (n = 27). Energy expenditure (D2O) and energy intake were measured daily. Nitrogen balance (NBAL) and protein turnover were determined at baseline (BL) and day 3 of AMT using 24-h urine and [N]-glycine. RESULTS: Protein and carbohydrate intakes…

PURPOSE: The infiltration of macrophages in skeletal muscle during exhaustive exercise promotes inflammation, myofiber lesion, and muscle injury. Although neutrophils upregulate macrophage infiltration in skeletal muscles during exercise, the role of neutrophils in promoting muscle injury after exhaustive exercise remains unclear. In this study, we investigated the effects of preexercise neutrophil depletion with antineutrophil antibody treatment on muscle injury, inflammation, and macrophage infiltration after exhaustive exercise. METHODS: Male C57BL/6J mice were randomly assigned to four groups, namely, sedentary with control antibody (n = 10), sedentary with antineutrophil antibody (n = 10), exhaustive exercise with control antibody (n = 10), and exhaustive exercise with antineutrophil antibody (n = 10). The mice were given intraperitoneal injection of the antineutrophil antibody (anti-Ly-6G, clone 1A8) or the control antibody (anti-Ly-6G, clone 2A3), and remained inactive or performed exhaustive exercise on a treadmill 48 h after the injection. Twenty-four hours after the…

This review of the exercise genomics literature encompasses the highest-quality articles published in 2015 across seven broad topics: physical activity behavior, muscular strength and power, cardiorespiratory fitness and endurance performance, body weight and adiposity, insulin and glucose metabolism, lipid and lipoprotein metabolism, and hemodynamic traits. One study used a quantitative trait locus for wheel running in mice to identify single nucleotide polymorphisms (SNPs) in humans associated with physical activity levels. Two studies examined the association of candidate gene ACTN3 R577X genotype on muscular performance. Several studies examined gene-physical activity interactions on cardiometabolic traits. One study showed that physical inactivity exacerbated the body mass index (BMI)-increasing effect of an FTO SNP but only in individuals of European ancestry, whereas another showed that high-density lipoprotein cholesterol (HDL-C) SNPs from genome-wide association studies exerted a smaller effect in active individuals. Increased levels of moderate-to-vigorous-intensity…

INTRODUCTION: In previous work, acute high-intensity aerobic exercise benefited continuous motor sequence task learning. As memory processes underlying motor sequence learning vary between tasks involving continuous and discrete movements, the objective of the current study was to determine whether the beneficial effects of acute aerobic exercise generalize to the learning of a discrete motor sequence task. METHODS: Sixteen young healthy individuals practiced a discrete motor sequence task preceded by either a period of rest or a bout of high-intensity cycling. Participants moved a cursor with a computer mouse to a series of discretely presented targets on a screen. Target presentation followed either a repeated or a random sequence, which allowed the evaluation of implicit sequence-specific motor learning. The change in movement response time over practice (△-ACQ) and from practice to a 24-h "no-exercise" retention test (△-RET) and the rate of improvement over practice (α-ACQ) and during the retention test (α-RET) were calculated. RESULTS: α-RET was greater for the repeated…

INTRODUCTION: Altitude training has been shown to improve aerobic capacity (VO2max) in elite and well-trained athletes. A variety of methods have been developed to simulate the hematological benefits obtained when training at altitude. The Elevation Training Mask 2.0 (ETM) purportedly simulates altitude training and has been suggested to increase VO2max, endurance performance, and lung function. METHODS: Twenty-four moderately trained subjects completed 6 weeks of high-intensity cycle ergometer training. Subjects were randomized into a mask (n=12) and no mask (n=12) group. Pre and post-training tests included VO2max, pulmonary function, maximal inspiration pressure, hemoglobin and hematocrit. Results: No significant differences were found in pulmonary function or hematological variables between or within groups. There was a significant improvement in VO2max in both the control (13.5%) and mask (16.5%) groups. The mask group also had significant improvements in ventilatory threshold (VT) (13.9%), power output at VT (31 W), respiratory compensation threshold (RCT) (10.2%), and power…

INTRODUCTION: In light of the recent revolutionary change in the use of the double-poling (DP) technique in cross-country skiing, our purpose was to compare the associated kinetics and kinematics on flat (DPflat) and uphill terrain (DPup), as well as to identify factors that determine performance. METHODS: Thirteen elite male cross-country skiers completed two incremental speed tests (Vpeak) involving roller skiing with the DP technique at moderate (13 and 24 km·h) and high speed (15 and 28.5 km·h) on a treadmill that was flat (1°) or tilted uphill (7°). Pole forces and three-dimensional whole-body kinematics were monitored simultaneously. RESULTS: In comparison to DPflat, during DPup, swing times were much shorter (-48%) and peak pole forces greater (+13%) and generated later during the poling phase (+68%), with higher impulses for all force components (+87%-123%). Furthermore, pole forces were 18% more effectively oriented for propulsion. During DPup, the skiers demonstrated more flexed elbows, as well as shoulder angles that were less flexed in the forward direction and less…

PURPOSE: The effect of exercise volume represented by exercise intensity and duration on postexercise executive function (EF) improvement remains unclear. In the present study, involving two volume-controlled evaluations, we aimed to compare acute exercise protocols with differing intensities and durations to establish an effective exercise protocol for improving EF. METHODS: In study 1, 12 healthy male subjects performed cycle ergometer exercise, based on a low-intensity (LI) protocol for 20 min (LI20), moderate-intensity (MI) protocol for 20 min (MI20), and MI20 volume-matched LI protocol for 40 min (LI40). The exercise intensities for the LI and MI were set at 30% and 60% of peak oxygen consumption, respectively. In study 2, 15 healthy male subjects performed MI exercise for 10 min (MI10), MI20, and 40 min (MI40). To evaluate the EF, the color-word Stroop task was administrated before exercise, immediately after exercise, and during the 30-min postexercise recovery. RESULTS: In study 1, postexercise EF improvement was sustained for a longer duration after MI20 than after LI40 and…

PURPOSE: This study compared the magnitude of the repeated bout effect (RBE) for different time intervals between two bouts of eccentric exercise of the elbow flexors to better understand the contralateral RBE (CL-RBE). METHODS: Untrained young men (22.0 ± 1.8 yr) were allocated to either a control or one of seven CL-RBE groups (n = 13 per group). The CL-RBE groups performed exercise consisting of 30 maximal isokinetic (30°·s) eccentric contractions of the elbow flexors (ECC1) with either dominant or nondominant arm followed 0.5 h, 6 h, 12 h, 24 h (1 d), 7 d (1 wk), 28 d (4 wk), or 56 d (8 wk) by the same exercise (ECC2) using the opposite arm. The control group used the nondominant arm for ECC1 and ECC2 separated by 2 wk. RESULTS: Maximal voluntary concentric contraction torque, peak torque angle, range of motion, upper arm circumference, muscle soreness, ultrasound echo intensity, and plasma creatine kinase activity and myoglobin concentration changed (P < 0.05) after ECC1, without significant difference among the groups. Changes in all variables after ECC2 were smaller (P < 0.05)…

PURPOSE: This study aimed to investigate in a real-life setting how moderate- and vigorous-intensity physical activity (PA) volumes differ according to absolute intensity recommendation and relative to individual fitness level by sex, age, and body mass index. METHODS: A total of 23,224 Finnish employees (10,201 men and 13,023 women; ages 18-65 yr; body mass index = 18.5-40.0 kg·m) participated in heart rate recording for 2+ d. We used heart rate and its variability, respiration rate, and on/off response information from R-R interval data calibrated by participant characteristics to objectively determine daily PA volume, as follows: daily minutes of absolute moderate (3-<6 METs) and vigorous (≥6 METs) PA and minutes relative to individual aerobic fitness for moderate (40%-<60% of oxygen uptake reserve) and vigorous (≥60%) PA. RESULTS: According to absolute intensity categorization, the volume of both moderate- and vigorous-intensity PA was higher in men compared with women (P < 0.001), in younger compared with older participants (P < 0.001), and in normal weight compared with…

INTRODUCTION: Quantifying corticomotor alterations is important to understand the neurophysiological mechanisms that likely contribute to the neuromuscular control deficits observed in patients with chronic ankle instability (CAI). Corticomotor output mapping provides further insight into the changes within the motor cortex and identifies potential changes in the area of the motor cortex associated with selected muscles. Therefore, this investigation compared the corticomotor map output for the fibularis longus (FL) muscle in patients with and without CAI. METHODS: Eighteen CAI patients and 16 healthy controls (HC) volunteered. Transcranial magnetic stimulation was used to map the motor cortex's representation of the FL. The normalized average of three motor evoked potentials at 100% of active motor threshold intensity was recorded for each scalp site on a 6 × 6 cm grid. Corticomotor output map was compared between groups through 1) the size of the corticomotor map area, 2) the volume of the corticomotor map, and 3) the location of cortical representation. Independent t-tests were…

PURPOSE: Exercise is an effective approach for developing bone mass and adolescence is a key period to optimize bone health. However, sports-specific training may have different effects on bone outcomes. This study examined the differences on bone outcomes between osteogenic (football) and nonosteogenic (swimming and cycling) sports and a control group in male adolescents. METHODS: One hundred twenty one males (13.1 ± 0.1 yr) were measured: 41 swimmers, 37 footballers, 29 cyclists, and 14 controls. Dual energy X-ray absorptiometry measured bone mineral density (BMD) and bone mineral content at lumbar spine, right and left hip, and total body. Hip Structural Analysis evaluated bone geometry at the femoral neck. Quantitative ultrasound evaluated bone stiffness at both feet. RESULTS: Footballers had significantly higher BMD at total body less head (7%-9%), total hip (12%-21%), and legs (7%-11%) compared with all groups and significantly higher BMD at the femoral neck than controls (14%). Cyclists had higher BMD at the trochanter (10%) and bone mineral content at the arms (10%) compared…

PURPOSE: To compare the metabolic effects of breaking up sedentary time with prolonged periods of standing versus multiple shorter standing bouts with the same total duration to determine whether, in principle, altering the frequency of "standing breaks" in sedentary time, influences metabolic responses over the course of the day. METHODS: Ten normoglycemic overweight/obese men (age, 33 ± 13 yr; body mass index, 28.3 ± 3.0 kg·m; mean ± SD) each participated in three experimental trials in random order, in which they arrived fasted, then consumed a test breakfast (8 kcal·kg body weight, with 37% energy from fat, 49% from carbohydrates, 14% from protein) and, 4 h later, an identical test lunch. Expired air and blood samples were taken fasted and for 8 h postprandially. In one trial (uninterrupted sitting), participants sat continuously throughout the observation period; in the prolonged standing (PRO-Stand) trial, participants stood still for 15 min every 30 min; and in the intermittent standing trial (INT-Stand), they stood for 1.5 min, 10 times every 30 min. RESULTS: Compared with…

There is clear and consistent evidence that regular physical activity is an important component of healthy lifestyles and fundamental to promoting health and preventing disease. Despite the known benefits of physical activity participation, many people in the United States remain inactive. More specifically, physical activity behavior is socially patterned with lower participation rates among women; racial/ethnic minorities; sexual minority youth; individuals with less education; persons with physical, mental, and cognitive disabilities; individuals >65 yr of age; and those living in the southeast region of the United States. Many health-related outcomes follow a pattern that is similar to physical activity participation. In response to the problem of inequities in physical activity and overall health in the United States, the American College of Sports Medicine (ACSM) has developed a national roadmap that supports achieving health equity through a physically active lifestyle. The actionable, integrated pathways that provide the foundation of ACSM's roadmap include the following: 1)…