The 50 most-cited articles in Medicine & Science in Sports & Exercise, 2017

PURPOSE: Exercise is associated with altered gut microbial composition, but studies have not investigated whether the gut microbiota and associated metabolites are modulated by exercise training in humans. We explored the impact of 6 wk of endurance exercise on the composition, functional capacity, and metabolic output of the gut microbiota in lean and obese adults with multiple-day dietary controls before outcome variable collection. METHODS: Thirty-two lean (n = 18 [9 female]) and obese (n = 14 [11 female]), previously sedentary subjects participated in 6 wk of supervised, endurance-based exercise training (3 d·wk) that progressed from 30 to 60 min·d and from moderate (60% of HR reserve) to vigorous intensity (75% HR reserve). Subsequently, participants returned to a sedentary lifestyle activity for a 6-wk washout period. Fecal samples were collected before and after 6 wk of exercise, as well as after the sedentary washout period, with 3-d dietary controls in place before each collection. RESULTS: β-diversity analysis revealed that exercise-induced alterations of the gut…

INTRODUCTION: Recent studies suggested that muscle mass and muscle strength may independently or synergistically affect aging-related health outcomes in older adults; however, prospective data on mortality in the general population are sparse. METHODS: We aimed to prospectively examine individual and joint associations of low muscle mass and low muscle strength with all-cause mortality in a nationally representative sample. This study included 4449 participants age 50 yr and older from the National Health and Nutrition Examination Survey 1999 to 2002 with public use 2011 linked mortality files. Weighted multivariable logistic regression models were adjusted for age, sex, race, body mass index (BMI), smoking, alcohol use, education, leisure time physical activity, sedentary time, and comorbid diseases. RESULTS: Overall, the prevalence of low muscle mass was 23.1% defined by appendicular lean mass (ALM) and 17.0% defined by ALM/BMI, and the prevalence of low muscle strength was 19.4%. In the joint analyses, all-cause mortality was significantly higher among individuals with low muscle…

PURPOSE: A Youth Compendium of Physical Activities (Youth Compendium) was developed to estimate the energy costs of physical activities using data on youth only. METHODS: On the basis of a literature search and pooled data of energy expenditure measurements in youth, the energy costs of 196 activities were compiled in 16 activity categories to form a Youth Compendium of Physical Activities. To estimate the intensity of each activity, measured oxygen consumption (V˙O2) was divided by basal metabolic rate (Schofield age-, sex-, and mass-specific equations) to produce a youth MET (METy). A mixed linear model was developed for each activity category to impute missing values for age ranges with no observations for a specific activity. RESULTS: This Youth Compendium consists of METy values for 196 specific activities classified into 16 major categories for four age-groups, 6-9, 10-12, 13-15, and 16-18 yr. METy values in this Youth Compendium were measured (51%) or imputed (49%) from youth data. CONCLUSION: This Youth Compendium of Physical Activities uses pediatric data exclusively,…

PURPOSE: Athletes and members of the public increasingly rely on wearable HR monitors to guide physical activity and training. The accuracy of newer, optically based monitors is unconfirmed. We sought to assess the accuracy of five optically based HR monitors during various types of aerobic exercise. METHODS: Fifty healthy adult volunteers (mean ± SD age = 38 ± 12 yr, 54% female) completed exercise protocols on a treadmill, a stationary bicycle, and an elliptical trainer (±arm movement). Each participant underwent HR monitoring with an electrocardiogaphic chest strap monitor (Polar H7), forearm monitor (Scosche Rhythm+), and two randomly assigned wrist-worn HR monitors (Apple Watch, Fitbit Blaze, Garmin Forerunner 235, and TomTom Spark Cardio), one on each wrist. For each exercise type, HR was recorded at rest, light, moderate, and vigorous intensity. Agreement between HR measurements was assessed using Lin's concordance correlation coefficient (rc). RESULTS: Across all exercise conditions, the chest strap monitor (Polar H7) had the best agreement with ECG (rc = 0.996) followed by…

PURPOSE: Evaluate the effects of a low-intensity resistance training (LI-RT) program associated with partial blood flow restriction on selected clinical outcomes in patients with knee osteoarthritis (OA). METHODS: Forty-eight women with knee OA were randomized into one of the three groups: LI-RT (30% one repetition maximum [1-RM]) associated (blood flow restriction training [BFRT]) or not (LI-RT) with partial blood flow restriction, and high-intensity resistance training (HI-RT, 80% 1-RM). Patients underwent a 12-wk supervised training program and were assessed for lower-limb 1-RM, quadriceps cross-sectional area, functionality (timed-stands test and timed-up-and-go test), and disease-specific inventory (Western Ontario and McMaster Universities Osteoarthritis Index [WOMAC]) before (PRE) and after (POST) the protocol. RESULTS: Similar within-group increases were observed in leg press (26% and 33%, all P < 0.0001), knee extension 1-RM (23% and 22%; all P < 0.0001) and cross-sectional area (7% and 8%; all P < 0.0001) in BFRT and HI-RT, respectively, and these were significantly…

Despite an intuitive relationship between technique and both running economy (RE) and performance, and the diverse techniques used by runners to achieve forward locomotion, the objective importance of overall technique and the key components therein remain to be elucidated. PURPOSE: This study aimed to determine the relationship between individual and combined kinematic measures of technique with both RE and performance. METHODS: Ninety-seven endurance runners (47 females) of diverse competitive standards performed a discontinuous protocol of incremental treadmill running (4-min stages, 1-km·h increments). Measurements included three-dimensional full-body kinematics, respiratory gases to determine energy cost, and velocity of lactate turn point. Five categories of kinematic measures (vertical oscillation, braking, posture, stride parameters, and lower limb angles) and locomotory energy cost (LEc) were averaged across 10-12 km·h (the highest common velocity < velocity of lactate turn point). Performance was measured as season's best (SB) time converted to a sex-specific z-score.…

PURPOSE: Statistical equivalence testing is more appropriate than conventional tests of difference to assess the validity of physical activity (PA) measures. This article presents the underlying principles of equivalence testing and gives three examples from PA and fitness assessment research. METHODS: The three examples illustrate different uses of equivalence tests. Example 1 uses PA data to evaluate an activity monitor's equivalence to a known criterion. Example 2 illustrates the equivalence of two field-based measures of physical fitness with no known reference method. Example 3 uses regression to evaluate an activity monitor's equivalence across a suite of 23 activities. RESULTS: The examples illustrate the appropriate reporting and interpretation of results from equivalence tests. In the first example, the mean criterion measure is significantly within ±15% of the mean PA monitor. The mean difference is 0.18 METs and the 90% confidence interval of -0.15 to 0.52 is inside the equivalence region of -0.65 to 0.65. In the second example, we chose to define equivalence for these…

PURPOSE: The presence of bone metastases has excluded participation of cancer patients in exercise interventions and is a relative contraindication to supervised exercise in the community setting because of concerns of fragility fracture. We examined the efficacy and safety of a modular multimodal exercise program in prostate cancer patients with bone metastases. METHODS: Between 2012 and 2015, 57 prostate cancer patients (70.0 ± 8.4 yr; body mass index, 28.7 ± 4.0 kg·m) with bone metastases (pelvis, 75.4%; femur, 40.4%; rib/thoracic spine, 66.7%; lumbar spine, 43.9%; humerus, 24.6%; other sites, 70.2%) were randomized to multimodal supervised aerobic, resistance, and flexibility exercises undertaken thrice weekly (EX; n = 28) or usual care (CON; n = 29) for 3 months. Physical function subscale of the Medical Outcomes Study Short-Form 36 was the primary end point as an indicator of patient-rated physical functioning. Secondary end points included objective measures of physical function, lower body muscle strength, body composition, and fatigue. Safety was assessed by recording the…

INTRODUCTION: The use of wearable activity monitors has seen rapid growth; however, the mode and intensity of exercise could affect the validity of heart rate (HR) and caloric (energy) expenditure (EE) readings. There is a lack of data regarding the validity of wearable activity monitors during graded cycling regimen and a standard resistance exercise. The present study determined the validity of eight monitors for HR compared with an ECG and seven monitors for EE compared with a metabolic analyzer during graded cycling and resistance exercise. METHODS: Fifty subjects (28 women, 22 men) completed separate trials of graded cycling and three sets of four resistance exercises at a 10-repetition-maximum load. Monitors included the following: Apple Watch Series 2, Fitbit Blaze, Fitbit Charge 2, Polar H7, Polar A360, Garmin Vivosmart HR, TomTom Touch, and Bose SoundSport Pulse (BSP) headphones. HR was recorded after each cycling intensity and after each resistance exercise set. EE was recorded after both protocols. Validity was established as having a mean absolute percent error (MAPE)…

PURPOSE: Accelerometers are increasingly being used to assess physical activity in large-scale surveys. Establishing whether key physical activity outcomes can be considered equivalent between three widely used accelerometer brands would be a significant step toward capitalizing on the increasing availability of accelerometry data for epidemiological research. METHODS: Twenty participants wore a GENEActiv, an Axivity AX3, and an ActiGraph GT9X on their nondominant wrist and were observed for 2 h in a simulated living space. Participants undertook a series of seated and upright light/active behaviors at their own pace. All accelerometer data were processed identically using open-source software (GGIR) to generate physical activity outcomes (including average dynamic acceleration (ACC) and time within intensity cut points). Data were analyzed using pairwise 95% equivalence tests (±10% equivalence zone), intraclass correlation coefficients (ICC) and limits of agreement. RESULTS: The GENEActiv and Axivity could be considered equivalent for ACC (ICC = 0.95, 95% confidence interval (CI),…

: New evidence suggests that reductions in sedentary behavior may increase physical activity and improve health. These findings point to new behavioral targets for intervention and new ways to think about intervening to increase overall physical activity in the population. This report provides a knowledge update reflecting the rapid accumulation of new evidence related to sedentary behavior and health among adults. Recent observational studies suggest that leveraging the time-inverse relationship between sedentary and active behaviors by replacing sitting with standing, light- or moderate-intensity activity can have important health benefits, particularly among less active adults. Clinical studies are providing evidence of the probable physiologic mechanisms underlying these associations, as well as insights into the cardiometabolic impact of breaking up and reducing sedentary behavior. In contrast to the well-established behavioral theories that guide the development and dissemination of evidence-based interventions to increase moderate- to vigorous-intensity physical activity,…

PURPOSE: This study aimed to implement an aggregation method in Matlab for generating ActiGraph counts from raw acceleration recorded with an alternative accelerometer device and to investigate the validity of the method. METHODS: The aggregation method, including the frequency band-pass filter, was implemented and optimized based on standardized sinusoidal acceleration signals generated in Matlab and processed in the ActiLife software. Evaluating the validity of the aggregation method was approached using a mechanical setup and with a 24-h free-living recording using a convenient sample of nine subjects. Counts generated with the aggregation method applied to Axivity AX3 raw acceleration data were compared with counts generated with ActiLife from ActiGraph GT3X+ data. RESULTS: An optimal band-pass filter was fitted resulting in a root-mean-square error of 25.7 counts per 10 s and mean absolute error of 15.0 counts per second across the full frequency range. The mechanical evaluation of the proposed aggregation method resulted in an absolute mean ± SD difference of -0.11 ± 0.97…

INTRODUCTION: Given the prevalence of hamstring injuries in football, a rehabilitation program that effectively promotes muscle tissue repair and functional recovery is paramount to minimize reinjury risk and optimize player performance and availability. PURPOSE: This study aimed to assess the concurrent effectiveness of administering an individualized and multifactorial criteria-based algorithm (rehabilitation algorithm [RA]) on hamstring injury rehabilitation in comparison with using a general rehabilitation protocol (RP). METHODS: Implementing a double-blind randomized controlled trial approach, two equal groups of 24 football players (48 total) completed either an RA group or a validated RP group 5 d after an acute hamstring injury. RESULTS: Within 6 months after return to sport, six hamstring reinjuries occurred in RP versus one injury in RA (relative risk = 6, 90% confidence interval = 1-35; clinical inference: very likely beneficial effect). The average duration of return to sport was possibly quicker (effect size = 0.34 ± 0.42) in RP (23.2 ± 11.7 d) compared with RA (25.5 ±…

PURPOSE: To compare the degree to which four accelerometer metrics-total activity counts per day (TAC per day), steps per day (steps per day), physical activity energy expenditure (PAEE) (kcal·kg·d), and moderate- to vigorous-intensity physical activity (MVPA) (min·d)-were correlated with PAEE measured by doubly labeled water (DLW). Additionally, accelerometer metrics based on vertical axis counts and triaxial counts were compared. METHODS: This analysis included 684 women and 611 men age 43 to 83 yr. Participants wore the Actigraph GT3X on the hip for 7 d twice during the study and the average of the two measurements was used. Each participant also completed one DLW measurement, with a subset having a repeat. PAEE was estimated by subtracting resting metabolic rate and the thermic effect of food from total daily energy expenditure estimated by DLW. Partial Spearman correlations were used to estimate associations between PAEE and each accelerometer metric. RESULTS: Correlations between the accelerometer metrics and DLW-determined PAEE were higher for triaxial counts than vertical…

Acute aerobic exercise improves mood and activates the endocannabinoid (eCB) system in physically active individuals; however, both mood and eCB responses to exercise may vary based on habitual levels of physical activity. PURPOSE: This study aimed to examine eCB and mood responses to prescribed and preferred exercises among individuals with low, moderate, and high levels of physical activity. METHODS: Thirty-six healthy adults (21 ± 4 yr) were recruited from low (≤60 min moderate-vigorous physical activity [MVPA] per week), moderate (150-299 min MVPA per week), and high (≥300 MVPA per week) physical activity groups. Participants performed both prescribed (approximately 70%-75% max) and preferred (i.e., self-selected) aerobic exercise on separate days. Mood states and eCB concentrations were assessed before and after exercise conditions. RESULTS: Both preferred and prescribed exercise resulted in significant increases (P < 0.01) in circulating eCB (N-arachidonoylethanolamine [AEA] and 2-arachidonoylglycerol); however, increases in AEA (P < 0.05) were larger in the prescribed…

PURPOSE: To determine if muscle growth is important for increasing muscle strength or if changes in strength can be entirely explained from practicing the strength test. METHODS: Thirty-eight untrained individuals performed knee extension and chest press exercise for 8 wk. Individuals were randomly assigned to either a high-volume training group (HYPER) or a group just performing the one repetition maximum (1RM) strength test (TEST). The HYPER group performed four sets to volitional failure (~8RM-12RM), whereas the TEST group performed up to five attempts to lift as much weight as possible one time each visit. RESULTS: Data are presented as mean (90% confidence interval). The change in muscle size was greater in the HYPER group for both the upper and lower bodies at most but not all sites. The change in 1RM strength for both the upper body (difference of -1.1 [-4.8, 2.4] kg) and lower body (difference of 1.0 [-0.7, 2.8] kg for dominant leg) was not different between groups (similar for nondominant). Changes in isometric and isokinetic torque were not different between groups. The…

INTRODUCTION: Chronic reductions in energy availability (EA) suppress reproductive function. A particular calculation of EA quantifies the dietary energy remaining after exercise for all physiological functions. Reductions in luteinizing hormone pulse frequency have been demonstrated when EA using this calculation is <30 kcal·kg·fat-free mass (ffm)·d. PURPOSE: We determined whether menstrual disturbances (MD) are induced when EA is <30 kcal·kg ffm·d. METHODS: Thirty-five sedentary, ovulatory women age 18 to 24 yr (weight, 59.0 ± 0.8 kg; body mass index, 21.8 ± 0.4 kg·m) completed a diet and exercise intervention over three menstrual cycles. Participants were randomized to groups that varied in the magnitude of negative energy balance created by the combination of exercise and energy restriction. Menstrual disturbances were determined using daily urinary estrone-1-glucuronide and pregnanediol glucuronide, midcycle luteinizing hormone, and menstrual calendars. In a secondary analysis, we calculated EA from energy balance data and tested the association of EA with MD. RESULTS: A…

PURPOSE: This study aimed to investigate longitudinal associations of objectively measured physical activity (PA) and sedentary behavior (SB) with body composition and physical fitness at a 12-month follow-up in healthy Swedish 4-yr-old children. METHODS: The data from the population-based MINISTOP trial were collected between 2014 and 2016, and this study included the 138 children who were in the control group. PA and SB were assessed using the wrist-worn ActiGraph (wGT3x-BT) accelerometer during seven 24-h periods and, subsequently, defined as SB, light-intensity PA, moderate-intensity PA, vigorous-intensity PA (VPA), and moderate-to-vigorous PA (MVPA). Body composition was measured using air-displacement plethysmography and physical fitness (cardiorespiratory fitness, lower and upper muscular strength as well as motor fitness) by the PREFIT fitness battery. Linear regression and isotemporal substitution models were applied. RESULTS: Greater VPA and MVPA at the age of 4.5 yr were associated with higher fat-free mass index (FFMI) at 5.5 yr (P < 0.001 and P = 0.044, respectively).…

PURPOSE: To evaluate the initial and long-term impacts on cardiometabolic health indicators of the Stand Up Victoria intervention-a 12-month, multicomponent workplace-delivered intervention that successfully reduced overall sitting time, primarily by increasing standing time. METHODS: Office worksites (≥1 km apart) from a single organization were cluster randomized to intervention (n = 7) or control (n = 7). Participants were 136 intervention and 95 control desk-based workers (5-39 per worksite; 68% women; mean ± SD age = 45.6 ± 9.4 yr). Outcomes, assessed at baseline (0 months), 3, and 12 months, were 14 individual biomarkers of body composition, blood pressure, glucose metabolism, lipid metabolism, and a composite overall cardiometabolic risk score. Intervention effects were assessed by linear mixed models, accounting for repeated measures and clustering, baseline values, and potential confounders. Missing data were multiply imputed. Significance was set at P < 0.05, two-tailed. RESULTS: No significant intervention effects were observed at 3 months. Significant effects, favoring…

INTRODUCTION: The application of contemporary statistical approaches coming from Machine Learning and Data Mining environments to build more robust predictive models to identify athletes at high risk for injury might support injury prevention strategies of the future. PURPOSE: The purpose was to analyze and compare the behavior of numerous machine learning methods to select the best-performing injury risk factor model to identify athlete at risk for lower extremity muscle injuries (MUSINJ). METHODS: A total of 132 male professional soccer and handball players underwent a preseason screening evaluation that included personal, psychological, and neuromuscular measures. Furthermore, injury surveillance was used to capture all the MUSINJ occurring in the 2013/2014 seasons. The predictive ability of several models built by applying a range of learning techniques were analyzed and compared. RESULTS: There were 32 MUSINJ over the follow-up period, 21 (65.6%) of which corresponded to the hamstrings, 3 to the quadriceps (9.3%), 4 to the adductors (12.5%), and 4 to the triceps surae (12.5%).…

INTRODUCTION/PURPOSE: To assess the utility of measurement methods that may be more accurate and precise than traditional questionnaire-based estimates of habitual physical activity and sedentary behavior we compared the measurement properties of a past year questionnaire (AARP) and more comprehensive measures: an internet-based 24-h recall (ACT24), and a variety of estimates from an accelerometer (ActiGraph). METHODS: Participants were 932 adults (50-74 yr) in a 12-month study that included reference measures of energy expenditure from doubly labeled water (DLW) and active and sedentary time via activPAL. RESULTS: Accuracy at the group level (mean differences) was generally better for both ACT24 and ActiGraph than the AARP questionnaire. The AARP accuracy for energy expenditure ranged from -4% to -13% lower than DLW, but its accuracy was poorer for physical activity duration (-48%) and sedentary time (-18%) versus activPAL. In contrast, ACT24 accuracy was within 3% to 10% of DLW expenditure measures and within 1% to 3% of active and sedentary time from activPAL. For ActiGraph,…

INTRODUCTION: Comprehensive evaluation of movement strategies during functional movement is a difficult undertaking. Because of this challenge, studied movements have been oversimplified. Furthermore, evaluating movement strategies at only a discrete time point(s) provide limited insight into how movement strategies may change or adapt in chronic ankle instability (CAI) patients. This study aimed to identify abnormal movement strategies in individuals with a history of ankle sprain injury during a sports maneuver compared with healthy controls. METHODS: Sixty-six participants, consisting of 22 CAI patients, 22 ankle sprain copers, and 22 healthy controls, participated in this study. Functional profiles of lower extremity kinematics, kinetics, and EMG activation from initial contact (0% of stance) to toe-off (100% of stance) were collected and analyzed during a jump landing/cutting task using a functional data analysis approach. RESULTS: Compared with copers, CAI patients displayed landing positions of less plantarflexion, less inversion, more knee flexion, more hip flexion, and less…

PURPOSE: This study aimed to examine the effects of swimming exercise pretreatment on a streptozotocin (STZ)-induced sporadic Alzheimer's disease (AD) rat model and provide an initial understanding of related molecular mechanisms. METHODS: Male 2.5-month-old Sprague-Dawley rats were divided into the following four groups: (a) control, (b) swim + vehicle, (c) STZ without swim, and (d) swim + STZ. The Barnes maze task and novel object recognition test were used to measure hippocampus-dependent spatial learning and working memory, respectively. Immunofluorescence staining, Western blot analysis, enzyme-linked immunosorbent assay (ELISA) analysis, and related assay kits were used to assess synaptic proteins, inflammatory cytokines, total antioxidant capacity, antioxidant enzymes, amyloid-beta production, and tau hyperphosphorylation. RESULTS: Behavioral tests revealed that exercise pretreatment could significantly inhibit STZ-induced cognitive dysfunction (P < 0.05). STZ animals displayed significant loss of presynaptic/postsynaptic markers in the hippocampal CA1 that was reversed by…

PURPOSE: Physical activity unquestionably maintains and improves health; however, physical activity levels globally are low and not rising despite all the resources devoted to this goal. Attention in both the research literature and the public policy domain has focused on social-behavioral factors; however, a growing body of literature suggests that biological determinants play a significant role in regulating physical activity levels. For instance, physical activity level, measured in various manners, has a genetic component in both humans and nonhuman animal models. This consensus article, developed as a result of an American College of Sports Medicine-sponsored round table, provides a brief review of the theoretical concepts and existing literature that supports a significant role of genetic and other biological factors in the regulation of physical activity. CONCLUSIONS: Future research on physical activity regulation should incorporate genetics and other biological determinants of physical activity instead of a sole reliance on social and other environmental determinants.

PURPOSE: We profiled the etiology and recovery of neuromuscular fatigue after simulated soccer match play. METHODS: Fifteen semiprofessional players completed a 90-min simulated soccer match. Before, immediately after, and at 24, 48, and 72 h, participants completed a battery of neuromuscular, physical, and perceptual tests. Perceived fatigue and muscle soreness were assessed via visual analog scales. Maximum voluntary contraction (MVC) and twitch responses to electrical (femoral nerve) and magnetic (motor cortex) stimulation during isometric knee extensor contractions and at rest were measured to assess central (voluntary activation) and peripheral (quadriceps potentiated twitch force, Qtw,pot) fatigue, and responses to single and paired magnetic stimuli were assessed to quantify corticospinal excitability and short intracortical inhibition, respectively. Countermovement jump, reactive strength index, and sprint performance were assessed to profile the recovery of physical function. RESULTS: Simulated match play elicited decrements in MVC that remained unresolved at 72 h (P =…

INTRODUCTION: Gastrointestinal (GI) distress in endurance athletes is prevalent and detrimental to performance. Adverse GI symptomatology can be analogous with irritable bowel syndrome, where fermentable oligosaccharide, disaccharide, monosaccharide, and polyols (FODMAP) reduction has demonstrated efficacy. This study investigated the effects of low FODMAP (LFOD) diet on GI distress parameters in runners with a history of nonclinical exercise-associated GI symptoms. METHODS: Eleven recreationally competitive runners (five men, six women; 5-km personal best 23:00 ± 4:02 min:s) participated in the study. Runners were allocated to a randomized 6-d LFOD or high FODMAP (HFOD) diet separated by a 1-d wash-out in a controlled, single-blinded cross-over study. In each period participants completed two strenuous running sessions consisting of 5 × 1000 m and a 7-km threshold run. GI symptoms (during-exercise and daily) and the Daily Analysis of Life Demand for Athletes questionnaires were completed. Area under the curve was calculated for daily GI symptoms across each dietary period and…

PURPOSE: Telemetric temperature capsule systems are wireless, relatively noninvasive, and easily applicable in field conditions and have therefore great advantages for monitoring core body temperature. However, the accuracy and responsiveness of available capsule systems have not been compared previously. Therefore, the aim of this study was to examine the validity, reliability, and inertia characteristics of four ingestible temperature capsule systems (i.e., CorTemp, e-Celsius, myTemp, and VitalSense). METHODS: Ten temperature capsules were examined for each system in a temperature-controlled water bath during three trials. The water bath temperature gradually increased from 33°C to 44°C in trials 1 and 2 to assess the validity and reliability, and from 36°C to 42°C in trial 3 to assess the inertia characteristics of the temperature capsules. RESULTS: A systematic difference between capsule and water bath temperature was found for CorTemp (0.077°C ± 0.040°C), e-Celsius (-0.081°C ± 0.055°C), myTemp (-0.003°C ± 0.006°C), and VitalSense (-0.017°C ± 0.023°C; P < 0.010), with the lowest…

PURPOSE: The present study was designed to provide mechanistic insight into the time course and etiology of muscle fatigue development and recovery during and after low-intensity exercise when it is combined with blood flow restriction (BFR). METHODS: Seventeen resistance-trained males completed four sets of low-intensity isotonic resistance exercise under two experimental conditions: knee extension exercise (i) with BFR and (ii) without BFR (CON). Neuromuscular tests were performed before, during (immediately after each set of knee extension exercise), and 1, 2, 4, and 8 min after each experimental condition. Maximal voluntary torque, quadriceps twitch torque in response to paired electrical stimuli at 10 Hz (PS10) and 100 Hz (PS100), PS10·PS100 ratio as an index of low-frequency fatigue, and voluntary activation were measured under isometric conditions. Perceptual and EMG data were recorded during each exercise condition. RESULTS: After the first set of exercise, BFR induced significantly greater reductions in maximal voluntary torque, PS100, and PS10·PS100 ratio compared with…

PURPOSE: Recent meta-analyses indicate that sprint interval training (SIT) improves cardiorespiratory fitness (V˙O2max), but the effects of various training parameters on the magnitude of the improvement remain unknown. The present meta-analysis examined the modifying effect of the number of sprint repetitions in an SIT session on improvements in V˙O2max. METHODS: The databases PubMed and Web of Science were searched for original studies that have examined pre- and posttraining V˙O2max in adults after ≥2 wk of training consisting of repeated (≥2) Wingate-type cycle sprints, published up to May 1, 2016. Articles were excluded if they were not in English; if they involved patients, athletes, or participants with a mean baseline V˙O2max of >55 mL·kg·min or a mean age <18 yr; and if an SIT trial was combined with another intervention or used intervals shorter than 10 s. A total of 38 SIT trials from 34 studies were included in the meta-analysis. Probabilistic magnitude-based inferences were made to interpret the outcome of the analysis. RESULTS: The meta-analysis revealed a likely large…

DESCRIPTION The Orthopedic Knowledge Update series has long been the foundational source of efficient review for all aspects of orthopedic surgery. This book covers the subspecialty of sports medicine. Responding to an ever-changing field, the series is continually updated and this fifth edition of the OKU in sports medicine is a timely, thorough, well-written update. PURPOSE This is exactly what the title suggests. It is not a comprehensive book on the subject, but rather an efficient and thorough update that assumes some basic knowledge and then discusses updates in orthopedic sports medicine. The print version has long been the go-to review source for residents in training and orthopedic practitioners for recertification preparation. The addition of a video supplement provides more depth and visualization of various techniques discussed in the book. However, they are bonus material and not essential to the substance of the review, so users lose nothing if they choose not to take advantage of the website. AUDIENCE The target audience is obviously orthopedic surgeons looking for an…

PURPOSE: Three of the most commonly identified hamstring strain injury (HSI) risk factors are age, previous HSI, and low levels of eccentric hamstring strength. However, no study has investigated the ability of these risk factors to predict the incidence of HSI in elite Australian footballers. Accordingly, the purpose of this prospective cohort study was to investigate the predictive ability of HSI risk factors using machine learning techniques. METHODS: Eccentric hamstring strength, demographic and injury history data were collected at the start of preseason for 186 and 176 elite Australian footballers in 2013 and 2015, respectively. Any prospectively occurring HSI were reported to the research team. Using various machine learning techniques, predictive models were built for 2013 and 2015 within-year HSI prediction and between-year HSI prediction (2013 to 2015). The calculated probabilities of HSI were compared with the injury outcomes and area under the curve (AUC) was determined and used to assess the predictive performance of each model. RESULTS: The minimum, maximum, and median…

PURPOSE: Guidelines recommend that young people engage in muscle-strengthening activities on at least 3 d·wk. The purpose of this study was to examine the effect of a school-based intervention focused on resistance training (RT) for adolescents. METHODS: The "Resistance Training for Teens" intervention was evaluated using a cluster-randomized, controlled trial with 607 adolescents (50.1% girls; 14.1 ± 0.5 yr) from 16 secondary schools. Teachers were trained to deliver the intervention, which included the following: (i) an interactive student seminar; (ii) a structured physical activity program, focused on RT; (iii) lunchtime fitness sessions; and (iv) Web-based smartphone apps. The primary outcome was muscular fitness (MF) and secondary outcomes included body mass index, RT skill competency, flexibility, physical activity, self-efficacy, and motivation. Assessments were conducted at baseline, 6 months (postprogram; primary end point), and 12 months (follow-up). Outcomes were assessed using linear mixed models, with three potential moderators tested using interaction terms (and…

PURPOSE: Using a novel technique of high-density surface EMG decomposition and motor unit (MU) tracking, we compared changes in the properties of vastus medialis and vastus lateralis MU after endurance (END) and high-intensity interval training (HIIT). METHODS: Sixteen men were assigned to the END or the HIIT group (n = 8 each) and performed six training sessions for 14 d. Each session consisted of 8-12 × 60-s intervals at 100% peak power output separated by 75 s of recovery (HIIT) or 90-120 min continuous cycling at ~65% V˙O2peak (END). Pre- and postintervention, participants performed 1) incremental cycling to determine V˙O2peak and peak power output and 2) maximal, submaximal (10%, 30%, 50%, and 70% maximum voluntary contraction [MVC]), and sustained (until task failure at 30% MVC) isometric knee extensions while high-density surface EMG signals were recorded from the vastus medialis and vastus lateralis. EMG signals were decomposed (submaximal contractions) into individual MU by convolutive blind source separation. Finally, MU were tracked across sessions by semiblind source…

PURPOSE: This study aimed to examine the associations between participation frequency in physical education (PE) classes and objective measures of physical activity (PA) and sedentary behavior (SB) in children from 12 countries at different levels of development. METHODS: This multinational, cross-sectional study included 5874 children 9-11 yr old from sites in Australia, Brazil, Canada, China, Colombia, Finland, India, Kenya, Portugal, South Africa, the United Kingdom, and the United States. PA and SB were monitored for seven consecutive days using a waist-worn accelerometer. PA and SB data were presented for weekdays (times in and out of school) and weekend days. Participation frequency in PE classes was determined by questionnaire. Multilevel modeling analyses stratified by sex were used. RESULTS: Overall, 24.8% of children self-reported participation in PE classes ≥3 times per week (25.3% in high-income countries [HIC] and 24.3% in low- and middle-income countries [LMIC]). After adjusting for age, sex, parental education, and body mass index z-score, results showed that children…

PURPOSE: This study aimed to determine the recovery timeline of sleep, subjective jet lag and fatigue, and team sport physical performance after east and west long-haul travel. METHODS: Ten physically trained men underwent testing at 0900 h and 1700 h local time on four consecutive days 2 wk before outbound travel (BASE), and the first 4 d after 21 h of outbound (WEST) and return (EAST) air travel across eight time zones between Australia and Qatar. Data collection included performance (countermovement jump, 20-m sprint, and Yo-Yo intermittent recovery level 1 [YYIR1] test) and perceptual (jet lag, motivation, perceived exertion, and physical feeling) measures. In addition, sleep was measured via wrist activity monitors and self-report diaries throughout the aforementioned data collection periods. RESULTS: Compared with the corresponding day at BASE, the reduction in YYIR1 distance after EAST was significantly different from the increase in WEST on day 1 after travel (P < 0.001). On day 2, significantly slower 20-m sprint times were detected in EAST compared with WEST (P = 0.03),…

PURPOSE: When assessing neuromuscular fatigue (NMF) from dynamic exercise using large muscle mass (e.g., cycling), most studies have delayed measurement for 1 to 3 min after task failure. This study aimed to determine the reliability of an innovative cycling ergometer permitting the start of fatigue measurement within 1 s after cycling. METHODS: Twelve subjects participated in two experimental sessions. Knee-extensor NMF was assessed by electrical nerve and transcranial magnetic stimulation with both a traditional chair setup (PRE- and POST-Chair, 2 min postexercise) and the new cycling ergometer (PRE, every 3 min during incremental exercise and POST-Bike, at task failure). RESULTS: The reduction in maximal voluntary contraction force POST-Bike (63% ± 12% PRE; P < 0.001) was not different between sessions and there was excellent reliability at PRE-Bike (intraclass correlation coefficient [ICC], 0.97; coefficients of variation [CV], 3.2%) and POST-Bike. Twitch (Tw) and high-frequency paired-pulse (Db100) forces decreased to 53% ± 14% and 62% ± 9% PRE, respectively (P < 0.001). Both…

PURPOSE: Data from large randomized controlled trials confirming sleep quality improvements with aerobic physical activity have heretofore been lacking for post-primary treatment breast cancer survivors. Our primary purpose for this report was to determine the effects of a physical activity behavior change intervention, previously reported to significantly increase physical activity behavior, on sleep quality in post-primary treatment breast cancer survivors. METHODS: Post-primary treatment breast cancer survivors (n = 222) were randomized to a 3-month physical activity behavior change intervention (Better Exercise Adherence after Treatment for Cancer [BEAT Cancer]) or usual care. Self-report (Pittsburgh Sleep Quality Index [PSQI]) and actigraphy (latency and efficiency) sleep outcomes were measured at baseline, 3 months (M3), and 6 months (M6). RESULTS: After adjusting for covariates, BEAT Cancer significantly improved PSQI global sleep quality when compared with usual care at M3 (mean between-group difference [M] = -1.4, 95% confidence interval [CI] = -2.1 to -0.7, P < 0.001) and…

PURPOSE: Mental fatigue is a psychobiological state caused by prolonged periods of demanding cognitive activity and has been observed to decrease time trial (TT) endurance performance by ∼3.5% in normal ambient temperatures. Recently, it has been suggested that heat may augment the negative effect of mental fatigue on cognitive performance, raising the question whether it may also amplify the effect of mental fatigue on TT performance. METHODS: In 30°C and 30% relative humidity, 10 endurance-trained male athletes (mean ± SD; age = 22 ± 3 yr, Wmax = 332 ± 41 W) completed two experimental conditions: intervention (I; 45-min Stroop task) and control (C; 45-min documentary). Pre- and postintervention/control, cognitive performance was followed up with a 5-min Flanker task. Thereafter, subjects cycled for 45 min at a fixed pace equal to 60% Wmax, immediately followed by a self-paced TT in which they had to produce a fixed amount of work (equal to cycling 15 min at 80% Wmax) as fast as possible. RESULTS: Self-reported mental fatigue was significantly higher after I compared with C (P <…

PURPOSE: Carnosine is a dipeptide composed of β-alanine and L-histidine and is present in skeletal muscle. Chronic oral β-alanine supplementation can induce muscle carnosine loading and is therefore seen as the rate-limiting factor for carnosine synthesis. However, the effect of L-histidine supplementation on carnosine levels in humans is never established. This study aims to investigate whether 1) L-histidine supplementation can induce muscle carnosine loading and 2) combined supplementation of both amino acids is more efficient than β-alanine supplementation alone. METHODS: Fifteen male and 15 female participants were equally divided in three groups. Each group was supplemented with either pure β-alanine (BA) (6 g·d), L-histidine (HIS) (3.5 g·d), or both amino acids (BA + HIS). Before (D0), after 12 d (D12), and after 23 d (D23) of supplementation, carnosine content was evaluated in soleus and gastrocnemius medialis muscles by H-MRS, and venous blood samples were collected. Muscle biopsies were taken at D0 and D23 from the vastus lateralis. Plasma and muscle metabolites…

INTRODUCTION: Secondary functional hypothalamic amenorrhea (SFHA) is common among female athletes, especially in weight-sensitive sports. The aim of this study was to investigate the link between SFHA and neuromuscular performance in elite endurance athletes. METHODS: Sixteen eumenorrheic (EUM) and 14 SFHA athletes from national teams and competitive clubs participated. Methods included gynecological examination, body composition (dual-energy x-ray absorptiometry), resting metabolic rate and work efficiency, exercise capacity, knee muscular strength (KMS) and knee muscular endurance (KME), reaction time (RT), blood sampling performed on the third to fifth days of the menstrual cycle, and 7-d assessment of energy availability. RESULTS: SFHA athletes had lower estrogen (0.12 ± 0.03 vs 0.17 ± 0.09 nmol·L, P < 0.05), triiodothyronine (T3) (1.4 ± 0.2 vs 1.7 ± 0.3 nmol·L, P < 0.01), and blood glucose (3.8 ± 0.3 vs 4.4 ± 0.3 mmol·L, P < 0.001) but higher cortisol levels (564 ± 111 vs 400 ± 140 nmol·L, P < 0.05) compared with EUM athletes. SFHA had a lower body weight (55.0 ± 5.8 vs 60.6 ±…

PURPOSE: Although the World Health Organization has recommended moderate- to vigorous-intensity physical activity (MVPA) to prevent cardiovascular disease (CVD) and some cancers, there are no estimates of lifetime risk of these noncommunicable diseases according to PA levels. We aimed to estimate the lifetime risk of CVD and cancers according to PA levels. METHODS: We followed 5807 men and 7252 women in the United States, 45-64 yr old, initially free of CVD and cancer from 1987 through 2012, and used a life table approach to estimate lifetime risks of CVD (coronary heart disease, heart failure, and stroke) and total cancer according to PA levels: poor (0 min·wk of MVPA), intermediate (1-74 min·wk of VPA or 1-149 min·wk of MVPA), or recommended (≥75 min·wk of VPA or ≥150 min·wk of MVPA). RESULTS: During the 246,886 person-years of follow-up, we documented 4065 CVD and 3509 cancer events and 2062 non-CVD and 2326 noncancer deaths. In men, the lifetime risks of CVD from 45 through 85 yr were 52.7% (95% confidence interval = 49.4-55.5) for poor PA and 45.7% (42.7-48.3) for recommended…

DESCRIPTION This is the latest update of a wonderful, go-to reference for surgical approaches to the musculoskeletal system since it was originally written in 1984. Now more than 30 years later, “Hoppenfeld's” remains the mainstay for resident and surgeon preparation for surgical procedures. The images are of the highest quality and thoughtfully represent a stepwise, layered, anatomic approach. The addition of pure anatomy and not just surgical approach images enables users to recognize normal relationships between structures and, particularly, at-risk neuromuscular elements. This edition retains the image quality and adds electronic access as a wonderful bonus. PURPOSE This book continues to serve as the leading reference on surgical approaches to the musculoskeletal system. Nothing else comes close. The online availability makes it even more user-friendly and accessible even when the hard copy is unavailable. AUDIENCE Although this book has long been “the” reference for residents in orthopedic training, after 24 y of practice, I still turn to it when I am performing surgery in a…

PURPOSE: To investigate whether the use of ensemble learning algorithms improve physical activity recognition accuracy compared to the single classifier algorithms, and to compare the classification accuracy achieved by three conventional ensemble machine learning methods (bagging, boosting, random forest) and a custom ensemble model comprising four algorithms commonly used for activity recognition (binary decision tree, k nearest neighbor, support vector machine, and neural network). METHODS: The study used three independent data sets that included wrist-worn accelerometer data. For each data set, a four-step classification framework consisting of data preprocessing, feature extraction, normalization and feature selection, and classifier training and testing was implemented. For the custom ensemble, decisions from the single classifiers were aggregated using three decision fusion methods: weighted majority vote, naïve Bayes combination, and behavior knowledge space combination. Classifiers were cross-validated using leave-one subject out cross-validation and compared on the basis…

PURPOSE: To prospectively assess adherence to oncologist-referred, exercise programming consistent with current recommendations for cancer survivors among women with early breast cancer across the trajectory of adjuvant treatment. METHODS: Sixty-eight women participated in supervised, hour-long, moderate-intensity, aerobic, and resistance exercise thrice per week during adjuvant chemotherapy ± radiation, with a step-down in frequency for 20 additional weeks. Adherence to exercise frequency (i.e., attendance), intensity, and time/duration, and barriers to adherence were tracked and compared during chemotherapy versus radiation, and during treatment (chemotherapy plus radiation, if received) versus after treatment. RESULTS: Attendance decreased with cumulative chemotherapy dose (cycles 1-2 vs cycles 3-8, cycle 3 vs cycles 7-8, all P ≤ 0.05) and was lower during chemotherapy than radiation (64% ± 25% vs 71% ± 32%, P = 0.02) and after treatment than during treatment (P < 0.01). Adherence to exercise intensity trended toward being higher during chemotherapy than radiation (69% ± 23% vs…

PURPOSE: To quantify how maximum skin wettedness (ωmax); that is, the determinant of the boundary between compensable and uncompensable heat stress, is altered by aerobic training in previously unfit individuals and further augmented by heat acclimation. METHODS: Eight untrained individuals completed an 8-wk aerobic training program immediately followed by 8 d of hot/humid (38°C, 65%RH) heat acclimation. Participants completed a humidity ramp protocol pretraining (PRE-TRN), posttraining (POST-TRN), and after heat acclimation (POST-HA), involving treadmill marching at a heat production of 450 W for 105 min in 37.5°C, 2.0 kPa (35%RH). After attaining a steady-state esophageal temperature (Tes), humidity increased 0.04 kPa·min. An upward inflection in Tes indicated the upper limit of physiological compensability (Pcrit), which was then used to quantify ωmax. Local sweat rate, activated sweat gland density, and sweat gland output on the back and arm were simultaneously measured throughout. RESULTS: Peak aerobic capacity increased POST-TRN by approximately 14% (PRE-TRN: 45.8 ± 11.8…

Dietary inorganic nitrate (NO3) supplementation improves skeletal muscle (SkM) contractile efficiency, and although rodent literature has suggested improvements in calcium handling or redox modifications as likely explanations, the direct mechanism of action in humans remains unknown. PURPOSE: This study aimed to examine the effects of 7 d of beetroot juice (BRJ) supplementation on SkM contractile characteristics and function. METHODS: Recreationally active males (n = 8) underwent transcutaneous electrical muscle stimulation of the vastus lateralis for the evaluation of contractile characteristics before and after 7 d of BRJ supplementation (280 mL·d, ~26 mmol NO3). An additional group of individuals (n = 8) followed the same supplementation protocol but underwent SkM biopsies pre- and post-supplementation for the determination of proteins associated with calcium handling via Western blotting, and the ratio of reduced/oxidized glutathione (GSH:GSSG), an indicator of cellular redox state, via high-performance liquid chromatography (HPLC). RESULTS: After supplementation, there was no…

BACKGROUND: According to cross-sectional and acute experimental evidence, reducing sitting time should improve cardiometabolic health risk biomarkers. Furthermore, the improvements obtained may depend on whether sitting is replaced with standing or ambulatory activities. Based on data from the Stand Up Victoria multicomponent workplace intervention, we examined this issue using compositional data analysis-a method that can examine and compare all activity changes simultaneously. METHODS: Participants receiving the intervention (n = 136 ≥ 0.6 full-time equivalent desk-based workers, 65% women, mean ± SD age = 44.6 ± 9.1 yr from seven worksites) were asked to improve whole-of-day activity by standing up, sitting less, and moving more. Their changes in the composition of daily waking hours (activPAL-assessed sitting, standing, and stepping) were quantified then tested for associations with concurrent changes in cardiometabolic risk (CMR) scores and 14 biomarkers concerning body composition, glucose, insulin, and lipid metabolism. Analyses were by mixed models, accounting for clustering…

INTRODUCTION: Physical endurance can be limited by muscle glycogen stores, in that glycogen depletion markedly reduces external work. During carbohydrate restriction, the liver synthesizes the ketone bodies, D-β-hydroxybutyrate, and acetoacetate from fatty acids. In animals and in the presence of glucose, D-β-hydroxybutyrate promotes insulin secretion and increases glycogen synthesis. Here we determined whether a dietary ketone ester, combined with plentiful glucose, can increase postexercise glycogen synthesis in human skeletal muscle. METHODS: After an interval-based glycogen depletion exercise protocol, 12 well-trained male athletes completed a randomized, three-arm, blinded crossover recovery study that consisted of consumption of either a taste-matched, zero-calorie control or a ketone monoester drink, followed by a 10-mM glucose clamp or saline infusion for 2 h. The three postexercise conditions were control drink then saline infusion, control drink then hyperglycemic clamp, or ketone ester drink then hyperglycemic clamp. Skeletal muscle glycogen content was determined in…

INTRODUCTION: Prostate cancer is the most common cancer in men, and patients treated with androgen deprivation therapy (ADT) experience unfavorable changes in body composition and associated metabolic complications, which can increase the risk of cardiovascular disease. We examined the effect of a 6-month program of aerobic and resistance exercise aimed at improving body composition and cardiorespiratory health in this population. METHODS: Ninety-seven men (43-90 yr) with localized prostate cancer receiving ADT were randomized to either exercise (EX, n = 50) or usual care (CON, n = 47). Supervised exercise was undertaken twice weekly at moderate to high intensity. Measures of cardiorespiratory capacity (V˙O2max), resting metabolic rate, central blood pressure, hemodynamic variables, blood markers, and body composition were assessed. RESULTS: There was a significant group-time interaction present for V˙O2max (P = 0.033) with a treatment effect for EX of 0.11 L·min (95% confidence interval [CI] = 0.04-0.19) (relative to body mass = 1.3 mL·kg·min, 95% CI = 0.3-2.3) and fat oxidation (P…

Large elastic arteries stiffen with age, which predisposes older adults to increased risk for cardiovascular disease. Aerobic exercise training is known to reduce the risk for cardiovascular disease, but the optimal exercise prescription for attenuating large elastic arterial stiffening in older adults is not known. PURPOSE: The purpose of this randomized controlled trial was to compare the effect of all-extremity high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on aortic pulse wave velocity (PWV) and carotid artery compliance in older adults. METHODS: Forty-nine sedentary older adults (age = 64 ± 1 yr), free of overt major clinical disease, were randomized to HIIT (n = 17), MICT (n = 18), or nonexercise controls (CONT; n = 14). HIIT (4 × 4 min at 90% HRpeak interspersed with 3 × 3 min active recovery at 70% HRpeak) and isocaloric MICT (70% HRpeak) were performed on an all-extremity non-weight-bearing ergometer, 4 d·wk for 8 wk under supervision. Aortic (carotid to femoral PWV [cfPWV]) and common carotid artery compliance were assessed at…