Showing papers in "Medicine and Science in Sports and Exercise in 2015"
TL;DR: The new ACSM exercise preparticipation health screening recommendations reduce possible unnecessary barriers to adopting and maintaining a regular exercise program, a lifestyle of habitual physical activity, or both, and thereby emphasize the important public health message that regular physical activity is important for all individuals.
Abstract: The purpose of the American College of Sports Medicine's (ACSM) exercise preparticipation health screening process is to identify individuals who may be at elevated risk for exercise-related sudden cardiac death and/or acute myocardial infarction. Recent studies have suggested that using the current ACSM exercise preparticipation health screening guidelines can result in excessive physician referrals, possibly creating a barrier to exercise participation. In addition, there is considerable evidence that exercise is safe for most people and has many associated health and fitness benefits; exercise-related cardiovascular events are often preceded by warning signs/symptoms; and the cardiovascular risks associated with exercise lessen as individuals become more physically active/fit. Consequently, a scientific roundtable was convened by the ACSM in June 2014 to evaluate the current exercise preparticipation health screening recommendations. The roundtable proposed a new evidence-informed model for exercise preparticipation health screening on the basis of three factors: 1) the individual's current level of physical activity, 2) presence of signs or symptoms and/or known cardiovascular, metabolic, or renal disease, and 3) desired exercise intensity, as these variables have been identified as risk modulators of exercise-related cardiovascular events. Identifying cardiovascular disease risk factors remains an important objective of overall disease prevention and management, but risk factor profiling is no longer included in the exercise preparticipation health screening process. The new ACSM exercise preparticipation health screening recommendations reduce possible unnecessary barriers to adopting and maintaining a regular exercise program, a lifestyle of habitual physical activity, or both, and thereby emphasize the important public health message that regular physical activity is important for all individuals.
441 citations
TL;DR: The sex-specific regression equations developed using anthropometric measures to predict somatic maturity provided good fits in external samples and provide an alternative to commonly used models.
Abstract: AB Purpose: Assessing biological maturity in studies of children is challenging. Sex-specific regression equations developed using anthropometric measures are widely used to predict somatic maturity. However, prediction accuracy was not established in external samples. Thus, we aimed to evaluate the fit of these equations, assess for overfitting (adjusting as necessary), and calibrate using external samples. Methods: We evaluated potential overfitting using the original Pediatric Bone Mineral Accrual Study (PBMAS; 79 boys and 72 girls; 7.5-17.5 yr). We assessed change in R2 and standard error of the estimate (SEE) with the addition of predictor variables. We determined the effect of within-subject correlation using cluster-robust variance and fivefold random splitting followed by forward-stepwise regression. We used dominant predictors from these splits to assess predictive abilities of various models. We calibrated using participants from the Healthy Bones Study III (HBS-III; 42 boys and 39 girls; 8.9-18.9 yr) and Harpenden Growth Study (HGS; 38 boys and 32 girls; 6.5-19.1 yr). Results: Change in R2 and SEE was negligible when later predictors were added during step-by-step refitting of the original equations, suggesting overfitting. After redevelopment, new models included age x sitting height for boys (R2, 0.91; SEE, 0.51) and age x height for girls (R2, 0.90; SEE, 0.52). These models calibrated well in external samples; HBS boys: b0, 0.04 (0.05); b1, 0.98 (0.03); RMSE, 0.89; HBS girls: b0, 0.35 (0.04); b1, 1.01 (0.02); RMSE, 0.65; HGS boys: b0, -0.20 (0.02); b1, 1.02 (0.01); RMSE, 0.85; HGS girls: b0, -0.02 (0.03); b1, 0.97 (0.02); RMSE, 0.70; where b0 equals calibration intercept (standard error (SE)) and b1 equals calibration slope (SE), and RMSE equals root mean squared error (of prediction). We subsequently developed an age x height alternate for boys, allowing for predictions without sitting height. Conclusion: Our equations provided good fits in external samples and provide an alternative to commonly used models. Original prediction equations were simplified with no meaningful increase in estimation error. (C) 2015 American College of Sports Medicine
375 citations
TL;DR: Interaction effects suggest that the additional risk of future HSI associated with advancing age or previous injury was mitigated by higher levels of eccentric hamstring strength, as well as interactions between both athlete age and history of HSI with eccentric hamstringstrength.
Abstract: PurposeAre eccentric hamstring strength and between-limb imbalance in eccentric strength, measured during the Nordic hamstring exercise, risk factors for hamstring strain injury (HSI)?MethodsElite Australian footballers (n = 210) from five different teams participated Eccentric hamstring st
248 citations
TL;DR: Prospective experimental studies provide considerable evidence of the positive effects of breaking up prolonged time spent sitting on metabolic outcomes, but it seems that the type, intensity, and frequency of physical activity necessary to effectively counteract the detrimental effects of prolonged sitting may differ according to the subjects' characteristics.
Abstract: AB Introduction: Prolonged time spent in sedentary behaviors (i.e., activities performed while sitting or reclining) has been consistently shown as an independent risk factor for increased cardiometabolic risk and all-cause mortality, whereas breaking up sedentary time is associated with improved cardiometabolic profile. However, there is still great controversy with the respect to what would be the optimal or minimum type, intensity, and frequency of physical activity necessary to revenue such positive outcomes in different populations. Objective: In this review, we aimed to discuss the available evidence from prospective experimental studies regarding the beneficial effects of breaking up prolonged sitting time on cardiometabolic risk factors, and the influence of intensity, frequency, and volume of the physical activity replacing sitting. Methods: A structured computer-based search on the electronic databases PUBMED and SCOPUS was independently conducted by two researchers. Only prospective intervention studies (controlled and uncontrolled) evaluating the effects of explicitly replacing sitting time with physical activity (including standing) on metabolic parameters as outcomes were included. Results: Seventeen studies were included in the review. Discussion: The currently available prospective experimental studies do advocate that breaking up sitting time and replacing it with light-intensity ambulatory physical activity and standing may be a stimulus sufficient enough to induce acute favorable changes in the postprandial metabolic parameters in physically inactive and type 2 diabetic subjects, whereas a higher intensity or volume seems to be more effective in rendering such positive outcomes in young habitually physically active subjects. Conclusion: Prospective experimental studies provide considerable evidence of the positive effects of breaking up prolonged time spent sitting on metabolic outcomes. However, it seems that the type, intensity, and frequency of physical activity necessary to effectively counteract the detrimental effects of prolonged sitting may differ according to the subjects' characteristics, especially with respect to the subjects' habitual physical activity level.
243 citations
TL;DR: The purpose of this study was to examine the association between YBT (asymmetry and composite score (CS) and noncontact injury in a sample of Division I (DI) college athletes from multiple sports and found that CS in this sample of DI athletes was not associated with increased risk of injury.
Abstract: AB Purpose: The Y balance test (YBT) is a screen of dynamic balance requiring stance leg balance while the contralateral leg reaches in anterior (ANT), posteromedial (PM), and posterolateral (PL) directions. YBT has been proposed as a screen for injury risk; however, limited research has examined the association between YBT and injury. The purpose of this study was to examine the association between YBT (asymmetry and composite score (CS)) and noncontact injury in a sample of Division I (DI) college athletes from multiple sports. Methods: DI college athletes were screened with the YBT during the preparticipation examination to determine asymmetry (absolute difference between legs in ANT, PL, and PM) and CS (summed average of right/left ANT, PL, and PM normalized to leg length). Participants were followed throughout the sport season, and noncontact injuries requiring athletic training staff intervention were recorded for analysis. Demographic variables between injured and uninjured athletes were assessed with independent t-tests. Receiver operating characteristic (ROC) curves determined optimal cut points for predicting injury on the basis of CS and asymmetry. CS was analyzed as a continuous variable, as ROC curves were unable to maximize sensitivity and specificity. Logistic regression models adjusted for sport and previous injury determined the odds of injury on the basis of asymmetry and CS. Results: One hundred and eighty-four participants were included in analysis; 81 were injured. ROC curves determined asymmetry >4 cm (sensitivity, 59%; specificity, 72%) as the optimal cut point for predicting injury. Only ANT asymmetry was significantly associated with noncontact injury (odds ratio, 2.33; 95% confidence interval, 1.15-4.76). Conclusions: ANT asymmetry >4 cm was associated with increased risk of noncontact injury. CS in this sample of DI athletes was not associated with increased risk of injury.
229 citations
TL;DR: At the time of return to sport, individuals after ACL reconstruction with weaker QF demonstrate altered landing patterns, whereas those with nearly symmetrical QF strength demonstrate landing patterns similar to uninjured individuals.
Abstract: Purpose
Evidence-based quadriceps femoris muscle (QF) strength guidelines for return to sport following anterior cruciate ligament (ACL) reconstruction are lacking. This study investigated the impact of QF strength asymmetry on knee landing biomechanics at the time of return to sport following ACL reconstruction.
229 citations
University of Cambridge1, University of Queensland2, University of South Carolina3, University of Western Australia4, Glasgow Caledonian University5, Baker IDI Heart and Diabetes Institute6, Norwegian School of Sport Sciences7, Loughborough University8, University of South Australia9, University of Massachusetts Amherst10, RMIT University11, Children's Hospital of Eastern Ontario12, University of Ottawa13
TL;DR: This research highlights the need to understand more fully the rationale behind the continued use of these devices, as well as their applications in the field of medicine and sport.
Abstract: WIJNDAELE, K., K. WESTGATE, S. K. STEPHENS, S. N. BLAIR, F. C. BULL, S. F. M. CHASTIN, D. W. DUNSTAN, U. EKELUND, D. W. ESLIGER, P. S. FREEDSON, M. H. GRANAT, C. E. MATTHEWS, N. OWEN, A. V. ROWLANDS, L. B. SHERAR, M. S. TREMBLAY, R. P. TROIANO, S. BRAGE, and G. N. HEALY. Utilization and Harmonization of Adult Accelerometry Data: Review and Expert Consensus. Med. Sci. Sports Exerc., Vol. 47, No. 10, pp. 2129–2139, 2015. Purpose: This study aimed to describe the scope of accelerometry data collected internationally in adults and to obtain a consensus from measurement experts regarding the optimal strategies to harmonize international accelerometry data. Methods: In March 2014, a comprehensive review was undertaken to identify studies that collected accelerometry data in adults (sample size, n Q 400). In addition, 20 physical activity experts were invited to participate in a twophase Delphi process to obtain consensus on the following: unique research opportunities available with such data, additional data required to address these opportunities, strategies for enabling comparisons between studies/countries, requirements for implementing/progressing such strategies, and value of a global repository of accelerometry data. Results: The review identified accelerometry data from more than 275,000 adults from 76 studies across 36 countries. Consensus was achieved after two rounds of the Delphi process; 18 experts participated in one or both rounds. The key opportunities highlighted were the ability for cross-country/cross-population comparisons and the analytic options available with the larger heterogeneity and greater statistical power. Basic sociodemographic and anthropometric data were considered a prerequisite for this. Disclosure of monitor specifications and protocols for data collection and processing were deemed essential to enable comparison and data harmonization. There was strong consensus that standardization of data collection, processing, and analytical procedures was needed. To implement these strategies, communication and consensus among researchers, development of an online infrastructure, and methodological comparison work were required. There was consensus that a global accelerometry data repository
212 citations
TL;DR: In this paper, the authors examined the effects of breaking sitting time on superficial femoral artery (SFA) endothelial functi and found that the effect of breaking ST on SFA was associated with cardiovascular disease risk factors.
Abstract: Sitting time (ST) is associated with cardiovascular disease risk factors, whereas breaking ST has been reported to be beneficial for reducing cardiovascular risk.PurposeThe objective of this study is to examine the effects of breaking ST on superficial femoral artery (SFA) endothelial functi
200 citations
TL;DR: This article reports on the "Research Evidence on Sedentary behavior" session of the Sedentary Behavior: Identifying Research Priorities workshop, sponsored by the National Heart, Lung, and Blood Institute and the National Institute on Aging, which aimed to identify priorities in SB research.
Abstract: Purpose and MethodsAlthough evidence is accumulating that sedentary behavior (SB), independent of moderate-to-vigorous intensity physical activity (MVPA), is associated with cardiometabolic and aging outcomes in adults, several gaps present opportunities for future research. This article rep
197 citations
TL;DR: Attaining at least 55 min·d of MVPA is associated with lower obesity in this multinational sample of children, which supports current guidelines, and greater MVPA and VPA were bothassociated with lower odds of obesity independent of sedentary behavior.
Abstract: PurposeTo determine the relationships between moderate-to-vigorous physical activity (MVPA), vigorous physical activity (VPA), sedentary time, and obesity in children from 12 countries representing a wide range of human developmentMethodsThe sample included 6539 children age 9–11 yr Times
182 citations
TL;DR: Step outputs obtained from waist- and wrist-worn accelerometer attachment sites are generally not comparable under either laboratory or free-living conditions.
Abstract: AB Purpose: The objective of this study is to compare step outputs obtained from waist and wrist accelerometer attachment sites under laboratory and free-living conditions. Methods: Under the laboratory condition, participants concurrently wore ActiGraph accelerometers at their waist and nondominant wrist while walking/running at treadmill speeds between 14 and 188 m[middle dot]min-1. Visually counted steps served as a criterion standard. Participants then wore both accelerometers for 7 d. All accelerometer step data were processed applying both the manufacturer's default and low-frequency extension filters. Paired sample t-tests were used to evaluate mean differences in criterion steps per minute and the four (attachment site x filter) estimates produced from the waist- and wrist-worn accelerometers in the laboratory study. Free-living differences in mean steps per day detected between the waist and wrist (considering both filters) were computed. Results: Relative to visually counted steps, the waist attachment site generally outperformed the wrist attachment site at most speeds, regardless of the applied filtering process. Under free-living conditions, the waist-worn accelerometer detected 6743 +/- 2398 (default filter) and 13,029 +/- 3734 (low-frequency extension) steps per day. The concurrently worn wrist accelerometer detected 9301 +/- 2887 (default filter) and 15,493 +/- 3958 (low-frequency extension) steps per day. Conclusion: The wrist attachment site detected consistently fewer visually counted steps than the waist attachment site at most treadmill speeds during laboratory testing. In contrast, the wrist attachment site produced a higher average step count (ranging from approximately 2500 to 8700 more steps per day under free-living conditions, dependent on the filtering process applied) than the waist attachment site under free-living conditions. In conclusion, step outputs obtained from waist- and wrist-worn accelerometer attachment sites are generally not comparable under either laboratory or free-living conditions.
TL;DR: Mental fatigue impairs intermittent running performance, and this negative effect of mental fatigue seems to be mediated by higher perception of effort.
Abstract: PurposeThe purpose of the study was to investigate the effects of mental fatigue on intermittent running performance.MethodsTen male intermittent team sports players performed two identical self-paced, intermittent running protocols. The two trials were separated by 7 d and preceded, in a ra
TL;DR: It is demonstrated that fatigue after self-paced exercise is task dependent, with a greater degree of peripheral fatigue after shorter higher-intensity TTs and more central fatigue after longer lower- intensity TTs.
Abstract: Purpose: Few studies have assessed neuromuscular fatigue after self-paced locomotor exercise; moreover, none have assessed the degree of supraspinal fatigue. This study assessed central and peripheral fatigue after self-paced exercise of different durations. Methods: Thirteen well-trained male cyclists completed 4 km, 20 km and 40 km simulated time-trials (TTs). Pre- and immediately post-TT (< 2.5 min), twitch responses from the knee-extensors
to electrical stimulation of the femoral nerve and transcranial magnetic stimulation of the motor cortex were recorded to assess neuromuscular and corticospinal function. Results: Time to complete 4 km, 20 km and 40 km was 6.0±0.2 min, 31.8±1.0 min and 65.8±2.2 min,
at average exercise intensities of 96%, 92% and 87% of V O2max, respectively. Exercise resulted in significant reductions in maximum voluntary contraction, with no difference between TTs (–18%, –15% and –16% for 4, 20 and 40 km respectively). Greater peripheral fatigue was evident after the 4 km (40% reduction in potentiated twitch) compared to the 20 km (31%) and 40 km TTs (29%). In contrast, longer TTs were characterized by more central
fatigue, with greater reductions in voluntary activation measured by motor nerve (–11% and – 10% for 20 km and 40 km vs. –7% for 4 km) and cortical (–12% and –10% for 20 km and 40 km vs. –6% for 4 km) stimulation. Conclusions: These data demonstrate fatigue after selfpaced exercise is task-dependent, with a greater degree of peripheral fatigue after shorter, higher intensity (~6 min) TTs and more central fatigue after longer, lower intensity TTs (>30
min).
TL;DR: RET seems to be a means to augment the respiratory capacity and intrinsic function of skeletal muscle mitochondria, and was accompanied by modest changes in mitochondrial proteins and transcript expression.
Abstract: PORTER C., P. T. REIDY, N. BHATTARAI, L. S. SIDOSSIS, and B. B. RASMUSSEN. Resistance Exercise Training Alters Mitochondrial Function in Human Skeletal Muscle. Med. Sci. Sports Exerc., Vol. 47, No. 9, pp. 1922–1931, 2015. Introduction: Loss of mitochondrial competency is associated with several chronic illnesses. Therefore, strategies that maintain or increase mitochondrial function will likely be of benefit in numerous clinical settings. Endurance exercise has long been known to increase mitochondrial function in the skeletal muscle. Comparatively little is known regarding the effect of resistance exercise training (RET) on skeletal muscle mitochondrial respiratory function. Purpose: The purpose of the current study was to determine the effect of chronic resistance training on skeletal muscle mitochondrial respiratory capacity and function. Methods: Here, we studied the effect of a 12-wk RET program on skeletal muscle mitochondrial function in 11 young healthy men. Muscle biopsies were collected before and after the 12-wk training program, and mitochondrial respiratory capacity was determined in permeabilized myofibers by high-resolution respirometry. Results: RET increased lean body mass and quadriceps muscle strength by 4% and 15%, respectively (P G 0.001). Coupled mitochondrial respiration supported by complex I, and complex I and II substrates increased by 2- and 1.4-fold, respectively (P G 0.01). The ratio of coupled complex I-supported respiration to maximal respiration increased with RET (P G 0.05), as did complex I protein abundance (P G 0.05), whereas the substrate control ratio for succinate was reduced after RET (P G 0.001). Transcripts responsible for proteins critical to electron transfer and NAD + production increased with training (P G 0.05), whereas transcripts involved in mitochondrial biogenesis were unaltered. Conclusions: Collectively, 12 wk of RET resulted in qualitative and quantitative changes in skeletal muscle mitochondrial respiration. This adaptation was accompanied by modest changes in mitochondrial proteins and transcript expression. RET seems to be a means to augment the respiratory capacity and
TL;DR: On the basis of the 100% survival rate from EHS in this large cohort, it is recommended that immediate CWI be implemented for the treatment of EHS.
Abstract: AB Purpose: This study aimed to investigate the effectiveness (speed of cooling and survival rates) of cold water immersion (CWI) in the treatment of patients with exertional heat stroke (EHS). Secondly, this study aimed to compare cooling rates on the basis of gender, age, and initial rectal temperature (Tr). Methods: Eighteen years of finish line medical tent patient records were obtained from the exertional heat illness treatment area at the Falmouth Road Race. Study participants included patients with EHS who were treated with CWI in the medical tent. The number of EHS cases was recorded for each year, and incidence was established on the basis of the number of finishers. Overall cooling rate and differences between initial Tr, age, and sex were evaluated. Results: A total of 274 cases of EHS was observed over the 18 yr of collected data. A mean of 15.2 +/- 13.0 EHS cases per year was recorded, with an overall incidence of 2.13 +/- 1.62 EHS cases per 1000 finishers. The average initial Tr was 41.44[degrees]C +/- 0.63[degrees]C, and the average cooling rate for patients with EHS was 0.22[degrees]C[middle dot]min-1 +/- 0.11[degrees]C[middle dot]min-1. CWI resulted in a 100% survival rate for all patients with EHS. No significant interactions between cooling rate and initial Tr (P = 0.778), sex (P = 0.89), or age (P = 0.70) were observed. Conclusions: CWI was found to effectively treat all cases of EHS observed in this study. CWI provided similar treatment outcomes in all patients, with no significant differences noted on the basis of initial Tr, age, or sex. On the basis of the 100% survival rate from EHS in this large cohort, it is recommended that immediate (on site) CWI be implemented for the treatment of EHS.
TL;DR: The findings underscore the need to explore functional movement and dynamic postural control assessments in postconcussion injury assessment protocols and suggest that the brain may be unable to effectively coordinate movement.
Abstract: AB Dynamic postural control deficits and disrupted cortical pathways have been reported to persist beyond an athlete's return to activity after concussion, potentially increasing the risk of acute lower extremity musculoskeletal injury. Purpose: This study aimed to investigate acute lower extremity musculoskeletal injury rates before and after concussion in athletes with concussion and their matched control. Methods: College athletes with concussion (n = 44; age, 20.0 +/- 1.2 yr) were physician-diagnosed. Nonconcussed college athletes (n = 58; age, 20.5 +/- 1.3 yr) were matched to individuals with concussion. Acute lower extremity musculoskeletal injury data were collected for 2 yr (+/-1 yr of the diagnosed concussion) using electronic medical records. Control participants' 2-yr window for exposure and musculoskeletal injury data were anchored to their match's concussion injury date. Pre- and postconcussion musculoskeletal injury rates were calculated for 90-, 180-, and 365-d periods for both study cohorts. Risk ratios were calculated to determine differences within and between groups for all periods. Results: Within 1 yr after concussion, the group with concussion was 1.97 (95% confidence interval (CI), 1.19-3.28; P = 0.01) times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than before concussion and 1.64 times (95% CI, 1.07-2.51; P = 0.02) more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than their matched nonconcussed cohort over the same period. Up to 180 d after concussion, the group with concussion was 2.02 (95% CI, 1.08-3.78; P = 0.02) times more likely to have experienced an acute lower extremity musculoskeletal injury after concussion than before concussion. Conclusions: Previous literature has identified dynamic postural control deficits along with increased motor evoked potential latency and decreased amplitude after concussion, suggesting that the brain may be unable to effectively coordinate movement. Our findings underscore the need to explore functional movement and dynamic postural control assessments in postconcussion injury assessment protocols.
TL;DR: Physical activity intervention strategies for older adults often focus on aerobic exercise, but the findings suggest that reducing sitting time and engaging in a variety of activities is also important, particularly for inactive adults.
Abstract: MATTHEWS, C. E., S. C. MOORE, J. SAMPSON, A. BLAIR, Q. XIAO, S. K. KEADLE, A. HOLLENBECK, and Y. PARK. Mortality Benefits for Replacing Sitting Time with Different Physical Activities. Med. Sci. Sports Exerc., Vol. 47, No. 9, pp. 1833–1840, 2015. Purpose: Prolonged sitting has emerged as a risk factor for early mortality, but the extent of benefit realized by replacing sitting time with exercise or activities of everyday living (i.e., nonexercise activities) is not known. Methods: We prospectively followed 154,614 older adults (59–82 yr) in the National Institutes of Health-AARP Diet and Health Study who reported no major chronic diseases at baseline and reported detailed information about sitting time, exercise, and nonexercise activities. Proportional hazard models were used to estimate adjusted hazard ratios and 95% confidence intervals (HR (95% confidence interval)) for mortality. An isotemporal modeling approach was used to estimate associations for replacing sitting time with specific types of physical activity, with separate models fit for less active and more active participants to accou nt for nonlinear associations. Results: During 6.8 yr (SD, 1.0) of follow-up, 12,201 deaths occurred. Greater sitting time (Q12 vs G 5h Id j1 ) was associated with increased risk for all-cause and cardiovascular mortality. In less active adults (G 2h Id j1 total activity), replacing 1 hId j1 of sitting with an equal amount of activity was associated with lower all-cause mortality for both exercise (HR, 0.58 (0.54–0.63)) and nonexercise activities (HR, 0.70 (0.66–0.74)), including household chores, lawn and garden work, and daily walking. Among more active participants (2+ hId j1 total activity), replacement of sitting time with purposeful exercise was associated with lower mortality (HR, 0.91 (0.88–0.94)) but not with nonexercise activity (HR, 1.00 (0.98–1.02)). Similar results were noted for cardiovascular mortality. Conclusions: Physical activity intervention strategies for older adults often focus on aerobic exercise, but our findings suggest that reducing sitting time and
TL;DR: It is suggested that the individual aerobic fitness level affects the ergogenic benefits induced by dietary nitrate supplementation and the optimal nitrate loading regimen required to elevate plasma [NO2] and to enhance performance in elite athletes is different from that of low-fit subjects and requires further studies.
Abstract: PurposeDietary nitrate supplementation has been shown to reduce O2 cost of submaximal exercise, improve exercise tolerance, and enhance performance in moderately trained individuals. In contrast, data have been provided that elite athletes do not benefit from nitrate supplementation. The aim
TL;DR: Although the standard methods for determination of CP, RCP, MLSS, and [HHb]BP are different, these indices occur at the same V˙O2p, suggesting that i) they may manifest as a result of similar physiological phenomenon and ii) each provides a valid delineation between tolerable and intolerable constant-power exercise.
Abstract: Critical power (CP), respiratory compensation point (RCP), maximal lactate steady state (MLSS), and deoxyhemoglobin breakpoint ([HHb]BP) are alternative functional indices that are thought to demarcate the highest exercise intensity that can be tolerated for long durations.PurposeWe tested t
TL;DR: Researchers should continue to consider metrics that reflect the total volume of PA in addition to existing PA metrics, and the use of TAC/d or standardized units of acceleration could harmonize PA across studies.
Abstract: The use of accelerometers in physical activity (PA) research has increased exponentially over the past 20 yr. The first commercially available accelerometer for assessing PA, the Caltrac, was worn on the waist and estimated PA energy expenditure in kilocalories. Around 1995, the emphasis shifted to measuring minutes of moderate-to-vigorous PA (MVPA), especially for bouts of 10 min or longer. Recent studies, however, show that light-intensity PA and intermittent (nonbout) MVPA also have important health benefits. The total volume of PA performed is an important variable because it takes the frequency, intensity, and duration of activity bouts and condenses them down into a single metric. The total volume of PA is appropriate for many research applications and can enhance comparisons between studies. In the future, machine learning algorithms will provide improved accuracy for activity type recognition and estimation of PA energy expenditure. However, in the current landscape of objectively measured PA, total activity counts per day (TAC/d) is a proxy for the total volume of PA. TAC/d percentiles for age- and gender-specific groups have been developed from the National Health and Nutrition Examination Survey ActiGraph data (2003-2006), providing a novel way to assess PA. The use of TAC/d or standardized units of acceleration could harmonize PA across studies. TAC/d should be viewed as an additional metric, not intended to replace other metrics (e.g., sedentary time, light-intensity PA, moderate PA, and vigorous PA) that may also be related to health. As future refinements to wearable monitors occur, researchers should continue to consider metrics that reflect the total volume of PA in addition to existing PA metrics.
TL;DR: The RSA is a refinement of the previous algorithm, allowing researchers who use a 24-h waist-worn accelerometry protocol to distinguish children's nocturnal sleep (including night time wake episodes) from daytime activities.
Abstract: AB Purpose: The purposes of this study were 1) to add layers and features to a previously published fully automated algorithm designed to identify children's nocturnal sleep and to exclude episodes of nighttime nonwear/wakefulness and potentially misclassified daytime sleep episodes and 2) to validate this refined sleep algorithm (RSA) against sleep logs. Methods: Forty-five fourth-grade school children (51% female) participants were asked to log evening bedtime and morning wake time and wear an ActiGraph GT3X+ (ActiGraph LLC, Pensacola, FL) accelerometer at their waist for seven consecutive days. Accelerometers were distributed through a single school participating in the Baton Rouge, USA, site of the International Study of Childhood Obesity, Lifestyle, and the Environment. We compared log-based variables of sleep period time (SPT), bedtime, and wake time to corresponding accelerometer-determined variables of total sleep episode time, sleep onset, and sleep offset estimated with the RSA. In addition, SPT and sleep onset estimated using standard procedures combining sleep logs and accelerometry (Log + Accel) were compared to the RSA-derived values. Results: RSA total sleep episode time (540 +/- 36 min) was significantly different from Log SPT (560 +/- 24 min), P = 0.003, but not different from Log + Accel SPT (549 +/- 24 min), P = 0.15. Significant and moderately high correlations were apparent between RSA-determined variables and those using the other methods (r = 0.61 to 0.74). There were no differences between RSA and Log + Accel estimates of sleep onset (P = 0.15) or RSA sleep offset and log wake time (P = 0.16). Conclusions: The RSA is a refinement of our previous algorithm, allowing researchers who use a 24-h waist-worn accelerometry protocol to distinguish children's nocturnal sleep (including night time wake episodes) from daytime activities
TL;DR: After 2 wk of acclimatization, trained cyclists are capable of completing a prolonged TT in a similar time in the heat compared with cool conditions, whereas in the unacclimatized state, they experienced a marked decrease in power output during the TTH.
Abstract: Purpose
This study aimed to determine the effects of heat acclimatization on performance and pacing during outdoor cycling time trials (TT, 43.4 km) in the heat.
TL;DR: Adolescents with concussion displayed increased center-of-mass medial/lateral displacement and velocity during dual-task walking after RTA, suggesting a regression of recovery in gait balance control, reinforces the need for a multifaceted approach to concussion management and continued monitoring beyond the point of clinical recovery.
Abstract: HOWELL, D. R., L. R. OSTERNIG, and L.-S. CHOU. Return to Activity after Concussion Affects Dual-Task Gait Balance Control Recovery. Med. Sci. Sports Exerc., Vol. 47, No. 4, pp. 673–680, 2015. Background: Recent work has identified deficits in dual-task gait balance control for up to 2 months after adolescent concussion; however, how resumption of preinjury physical activities affects recovery is unknown. Purpose: The objective of this study is to examine how return to activity (RTA) affects recovery from concussion on measures of symptom severity, cognition, and balance control during single-task and dual-task walking. Methods: Nineteen adolescents with concussion who returned to preinjury activity within 2 months after injury and 19 uninjured, matched controls completed symptom inventories, computerized cognitive testing, and single-task and dual-task gait analyses. Concussion participants were assessed at five time points: within 72 h, 1 wk, 2 wk, 1 month, and 2 months postinjury. Control participants were assessed at the same time points as their matched concussion counterparts. RTA day was documented as the postinjury day in which physical activity participation was allowed. The effect of returning to physical activity was assessed by examining the percent change on each dependent variable across time before and directly after the RTA. Data were analyzed by two-way mixed effects ANOVAs. Results: After the RTA day, concussion participants significantly increased their total center-of-mass medial/lateral displacement (P = 0.009, Gp 2 = .175) and peak velocity (P = 0.048, Gp 2 = 0.104) during dual-task walking when compared with pre-RTA data, whereas no changes for the concussion group or between groups were detected on measures of single-task walking, forward movement, or cognition. Conclusions: Adolescents with concussion displayed increased center-of-mass medial/lateral displacement and velocity during dual-task walking after RTA, suggesting a regression of recovery in gait balance control. This study reinforces the need for a multifaceted approach to con
TL;DR: Listening to music during intense interval exercise may be an effective strategy for facilitating participation in, and adherence to, this form of training.
Abstract: IntroductionInterval exercise training can elicit physiological adaptations similar to those of traditional endurance training, but with reduced time. However, the intense nature of specific protocols, particularly the “all-out” efforts characteristic of sprint interval training (SIT), may b
TL;DR: An exercise session consisting of a 5-min warm-up, 20 min of moderate-intensity exercise, and a5-min cooldown improves cognition, whereas shorter or longer durations of moderate exercise have negligible benefits.
Abstract: Purpose: The study aimed to provide evidence-based recommendations for the prescription of a single session of exercise to improve cognitive performance. In particular, the purpose was to determine the dose–response relation between exercise duration and cognitive performance for a moderate-intensity session of aerobic exercise. Methods: Twenty-six healthy young men participated in a reading control treatment and three exercise treatments presented in a random order. The exercise treatments were designed on the basis of the American College of Sports Medicine guidelines and consisted of a 5-min warm-up, a 5-min cooldown, and cycling at moderate intensity (approximately 65% HR reserve) for 10, 20, or 45 min. The Stroop test was administrated after completion of each assigned treatment. Results: Exercise at moderate intensity for 20 min resulted in significantly better cognitive performance, as assessed by shorter response time and higher accuracy. This result was found regardless of the type of cognitive function assessed. In addition, a curvilinear dose–response relation between exercise duration and cognitive performance was observed. Conclusions: An exercise session consisting of a 5-min warm-up, 20 min of moderate-intensity exercise, and a 5-min cooldown improves cognition, whereas shorter or longer durations of moderate exercise have negligible benefits. This study provides the foundation for the prescription of a single session of moderate exercise to facilitate cognitive function in healthy younger adults.
TL;DR: Weight-bearing athletic activity increases BMD but may increase stress fracture risk in those with menstrual dysfunction and bone microarchitecture and strength differences are more pronounced in AA with multiple stress fractures.
Abstract: IntroductionThis study was aimed to compare fracture prevalence in oligoamenorrheic athletes (AA), eumenorrheic athletes (EA), and nonathletes (NA) and determine relationships with bone density, structure, and strength estimates.MethodsOne hundred seventy-five females (100 AA, 35 EA, and 40
TL;DR: These data indicate that two-dimensional ultrasonography is reliable for assessing BFlh architecture at rest and during graded isometric contractions, and Fascicle length, fascicle length relative to muscle thickness, and pennation angle are significantly different in previously injured biceps femoris long head compared to an uninjured contralateral B flh.
Abstract: PurposeThis study aimed (i) to determine the reliability of two-dimensional ultrasonography for the assessment of biceps femoris long head (BFlh) architectural characteristics and (ii) to determine whether limbs with a history of strain injury in the BFlh display different architecture and e
TL;DR: In this paper, the reliability of the sex difference in pacing across many marathons and after adjusting women's performances by 12% to address men's greater maxima was determined.
Abstract: Studies on nonelite distance runners suggest that men are more likely than women to slow their pace in a marathon.PurposeThis study determined the reliability of the sex difference in pacing across many marathons and after adjusting women’s performances by 12% to address men’s greater maxima
TL;DR: This research highlights the need to understand more fully the rationale behind the continued use of these devices, as well as their applications in the field of medicine and sport.
Abstract: AB Introduction: In vivo measurements have been used in the past two decades to investigate the effects of increased loading on tendon properties, yet the current understanding of tendon macroscopic changes to training is rather fragmented, limited to reports of tendon stiffening, supported by changes in material properties and/or tendon hypertrophy. The main aim of this review was to analyze the existing literature to gain further insights into tendon adaptations by extracting patterns of dose-response and time-course. Methods: PubMed/Medline, SPORTDiscus, and Google Scholar databases were searched for studies examining the effect of training on material, mechanical, and morphological properties via longitudinal or cross-sectional designs. Results: Thirty-five of 6440 peer-reviewed articles met the inclusion criteria. The key findings were i) the confirmation of a nearly systematic adaptation of tendon tissue to training, ii) the important variability in the observed changes in tendon properties between and within studies, and iii) the absence of a consistent incremental pattern regarding the dose-response or the time-course relation of tendon adaptation within the first months of training. However, long-term (years) training was associated with a larger tendon cross-sectional area, without any evidence of differences in material properties. Our analysis also highlighted several gaps in the existing literature, which may be addressed in future research. Conclusions: In line with some cross-species observations about tendon design, tendon cross-sectional area allegedly constitutes the ultimate adjusting parameter to increased loading. We propose here a theoretical model placing tendon hypertrophy and adjustments in material properties as parts of the same adaptive continuum
TL;DR: Compared to measured values, the VA and VM regression models developed on wrist accelerometer data had insignificant mean bias for child-METs and time spent in SB, LPA, MPA, and VPA; however, they had large individual errors.
Abstract: PurposeThe purpose of this study was to develop and validate methods for analyzing wrist accelerometer data in youth.MethodsA total of 181 youth (mean ± SD; age, 12.0 ± 1.5 yr) completed 30 min of supine rest and 8 min each of 2 to 7 structured activities, selected from a list of 25. Receive