Ultrasound-derived Biceps Femoris Long-Head Fascicle Length: Extrapolation Pitfalls Purpose To compare biceps femoris long-head (BFlh) fascicle lengths (Lfs) obtained with different ultrasound-based approaches: 1) single ultrasound images and linear Lf extrapolation; 2) single ultrasound images and one of two different trigonometric equations (termed equations A and B); and 3) extended field of view (EFOV) ultrasound images. Methods Thirty-seven elite alpine skiers (21.7±2.8 yrs) without a previous history of hamstring strain injury were tested. Single ultrasound images were collected with a 5 cm linear transducer from BFlh at 50% femur length and were compared with whole muscle scans acquired by EFOV ultrasound. Results The intra-session reliability (ICC3,k = intra-class correlation coefficient) of Lf measurements was very high for both single ultrasound images (i.e., Lf estimated by linear extrapolation; ICC3,k = 0.96-0.99, SEM = 0.18 cm) and EFOV scans (ICC3,k = 0.91 -0.98, SEM = 0.19 cm). Although extrapolation methods showed cases of overestimation and underestimation of Lf when compared with EFOV scans, mean Lf measured from EFOV scans (8.07±1.36 cm) was significantly shorter than Lf estimated by trigonometric equations A (9.98±2.12 cm, P<0.01) and B (8.57±1.59 cm, P=0.03), but not significantly different from Lf estimated with manual linear extrapolation (MLE) (8.40±1.68 cm, p=0.13). Bland-Altman analyses revealed mean differences in Lfs obtained from EFOV scans and those estimated from equation A, equation B and MLE of 1.91±2.1 cm, 0.50±1.0 cm and 0.33±1.0 cm, respectively. Conclusions The typical extrapolation methods used for estimating Lf from single ultrasound images are reliable within the same session, but not accurate for estimating BFlh Lf at rest with a 5-cm FOV. We recommend that EFOV scans are implemented to accurately determine intervention-related Lf changes in BFlh. Address for correspondence: Dr Martino Franchi Institute of Physiology, Department of Biomedical Sciences, University of Padua, Italy martino.franchi@unipd.it The authors would like to thank Swiss Ski and Balgrist foundation stitftung for the financial support for the present study. The authors declare the non-presence of any conflict of interests. The results of the present study do not constitute endorsement by ACSM. The results of the present study are presented clearly, honestly, without fabrication, falsification or inappropriate data manipulation. Accepted for Publication: 26 July 2019 © 2019 American College of Sports Medicine

Can Creatine Combat the Mental Fatigue–associated Decrease in Visuomotor Skills? Purpose The importance of the brain in sports was recently confirmed by the negative effect of mental fatigue (MF) on sport-specific psychomotor skills. Creatine supplementation improves strength, but can also improve cognitive functioning. To explore the role of creatine in combatting MF, we evaluated whether creatine supplementation counteracts the MF-associated impairment in sport-specific psychomotor skills. Methods In 23°C, 14 healthy participants (4F 10M; mean ± SD; age:24 ± 3 y; mass:74 ± 13 kg; height:179 ± 9 cm) performed -counterbalanced, crossover and double blinded- a 90-min mentally fatiguing task (i.e. Stroop task) in two different conditions: after a 7-day creatine supplementation (CR; 20 g/day) and after a 7-day calcium lactate supplementation (PLAC; placebo), separated by a 5-week washout. In both conditions, a 7-min sport-specific visuomotor task, a dynamic handgrip strength endurance task and a 3-min Flanker task was performed before and after the mentally fatiguing task. Physiological and perceptual responses were measured throughout the protocol. Results Handgrip strength endurance was higher in CR compared to PLAC (p=0.022). MF impaired visuomotor response time (+4.4%; p=0.022) and Flanker accuracy (-5.0%; p=0.009) in both conditions. Accuracy on the Stroop task was higher in CR compared to PLAC (+4.9%; p=0.026). Within the perceptual and physiological parameters, only motivation and vigor (p≤0.027) were lower in CR compared to PLAC. Conclusion Creatine supplementation improved physical (strength endurance) and prolonged cognitive (Stroop accuracy) performance, yet it did not combat mental fatigue-induced impairments in short sport-specific psychomotor or cognitive (Flanker) performance. These results warrant further investigation in the potential role of creatine in combatting the MF-associated decrements in prolonged (e.g. 90-min soccer game) sport performance, and suggest a role of brain-phosphocreatine in MF. Corresponding author: Romain Meeusen Human Physiology and Sports Physiotherapy Research Group Pleinlaan 2 B-1050 Brussels, Belgium Email: romain.meeusen@vub.be Tel: +32 2 629 27 32 The authors declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. The results of the present study do not constitute endorsement by ACSM. No conflict of interest is declared by the authors. Accepted for Publication: 5 August 2019 © 2019 American College of Sports Medicine

Short Sprints Accumulated at School Modulate Postprandial Metabolism in Boys Introduction This study examined the efficacy of maximal sprint running accumulated during a typical school day to modulate postprandial metabolism in adolescent boys. Methods Nineteen adolescent boys completed three, 2-day experimental conditions; a standard-practice control (CON); accumulated in-school sprint running (ACC); and a single block of afterschool sprint running (BLO). On Day 1, a fasting capillary blood sample was taken at 07:35 in the school. Three subsequent postprandial blood samples were taken at predetermined times after consumption of standardised breakfast and lunch. During ACC, participants accumulated four sets of 10 × 30 m maximal-intensity sprint runs across natural breaks in lessons. During BLO, participants performed the same number of sprints (forty) in a single after-school exercise session. The blood samples from Day 1 were replicated on the day after exercise (Day 2). Results On Day 1, no significant differences in total area under the plasma triacylglycerol concentration versus time curve (TAUC-TAG) were observed between conditions (P = 0.126). However, TAUC-insulin was lower in ACC compared with BLO (-26%, ES = 0.86, P = 0.001) and CON (-22%, ES = 0.72, P = 0.010). On Day 2, TAUC-TAG was 12% lower after ACC (ES = 0.49; P = 0.002) and 10% lower after BLO (ES = 0.37; P = 0.019) compared with CON. No significant differences were observed between conditions on Day 2 for postprandial insulin or glucose (P ≥ 0.738). Conclusion Four sets of 10 × 30 m sprints, accumulated in four separate bouts (<5 min) during the school day reduced postprandial triacylglycerol and insulin concentrations in adolescent boys and may represent an effective in-school exercise strategy to promote metabolic health. Corresponding author: Dr Keith Tolfrey, School of Sport Exercise and Health Sciences, Loughborough University, Epinal Way, Loughborough, LE11 3TU. k.tolfrey@lboro.ac.uk, +44 (0)1509 226355 This research was supported by the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre. The views expressed are those of the authors and not necessarily those of the NHS, the NIHR or the Department of Health. CONFLICT OF INTEREST: The authors declare no conflict of interest. The results of the present study do not constitute endorsement by ACSM. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 2 August 2019 © 2019 American College of Sports Medicine

During Cycling What Limits Maximum Mechanical Power Output at Cadences above 120 rpm? Purpose A key determinant of muscle coordination and maximum power output during cycling is pedalling cadence. During cycling the neuromuscular system may select from numerous solutions that solve the task demands while producing the same result. For more challenging tasks fewer solutions will be available. Changes in the variability of individual muscle excitations (EMG) and multi-muscle coordination, quantified by entropic half-life (EnHL), can reflect the number of solutions available at each system level. We therefore ask whether reduced variability in muscle coordination patterns occur at critical cadences and if they coincide with reduced variability in excitations of individual muscles. Methods Eleven trained cyclists completed an array of cadence-power output conditions. EnHL of EMG intensity recorded from 10 leg muscles and EnHL of principal components describing muscle coordination were calculated. Multivariate adaptive regressive splines were used to determine the relationships between each EnHL and cycling condition or excitation characteristics (duration, duty cycle). Results Muscle coordination became more persistent at cadences up to 120 r.p.m., indicated by increasing EnHL values. Changes in EnHL at the level of the individual muscles differed from the changes in muscle coordination EnHL, with longer EnHLs occurring at the slowest (< 80 r.p.m.) and fastest (>120 r.p.m.) cadences. EnHL of the main power producing muscles however reached a minimum by 80 r.p.m. and did not change across the faster cadences studied. Conclusions Muscle coordination patterns, rather than the contribution of individual muscles, are key to power production at faster cadences in trained cyclists. Reductions in maximum power output at cadences above 120 r.p.m. could be a function of the time available to coordinate orientation and transfer of forces to the pedals. Corresponding author: Name: Dr. E. F. Hodson-Tole, Mailing address: Dpt. Life Sciences, Manchester Metropolitan University, Manchester, M1 5GD, UK. Tel: +44 161 247 5923. Email: e.tole@mmu.ac.uk There are no professional relationships with companies or manufacturers to disclose for all authors. This research was supported by the Natural Sciences and Engineering Research Council of Canada (NSERC) Discovery Grant to J.M. Wakeling. O.M. Blake was supported by an NSERC Vanier Scholarship. The results of the present study do not constitute endorsement by the American College of Sports Medicine. The authors declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 11 July 2019. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. © 2019 American College of Sports Medicine

Response of Liver Metabolic Pathways to Ketogenic Diet and Exercise Are Not Additive Purpose Studies suggest ketogenic diets (KDs) produce favorable outcomes (health and exercise performance); however, most rodent studies have used a low protein KD, which does not reflect the normal-to-high protein KDs used by humans. Liver has an important role in ketoadaptation due to its involvement in gluconeogenesis and ketogenesis. This study was designed to test the hypothesis that exercise training (ExTr) while consuming a normal protein KD (NPKD) would induce additive/synergistic responses in liver metabolic pathways. Methods Lean, healthy male C57BL/6J mice were fed a low-fat control diet (15.9% kcal protein, 11.9% kcal fat, 72.2% kcal carbohydrate) or carbohydrate-deficient NPKD (16.1% protein, 83.9% kcal fat) for 6 weeks. After 3 weeks on the diet, half were subjected to 3-week treadmill ExTr (5day/week, 60min/day, moderate-vigorous intensity). Upon conclusion, metabolic and endocrine outcomes related to substrate metabolism were tested in liver and pancreas. Results NPKD-fed mice had higher circulating β-hydroxybutyrate and maintained glucose at rest and during exercise. Liver of NPKD-fed mice had lower pyruvate utilization and greater ketogenic potential as evidenced by higher oxidative rates to catabolize lipids (mitochondrial and peroxisomal) and ketogenic amino acids (leucine). ExTr had higher expression of the gluconeogenic gene, Pck1, but lower hepatic glycogen, pyruvate oxidation, incomplete fat oxidation, and total pancreas area. Interaction effects between the NPKD and ExTr were observed for intrahepatic triglycerides, as well as genes involved in gluconeogenesis, ketogenesis, mitochondrial fat oxidation, and peroxisomal markers; however, none were additive/synergistic. Rather, in each instance the interaction effects showed the NPKD and ExTr opposed each other. Conclusions A NPKD and ExTr independently induce shifts in hepatic metabolic pathways, but changes do not seem to be additive/synergistic in healthy mice. Corresponding author: Robert C. Noland, Office: 225-763-2788, Fax: 225-763-0273. Email:robert.noland@pbrc.edu. Mailing address: 6400 Perkins Road, Baton Rouge, LA, 70808 This work utilized PBRC core facilities (Genomics, and Animal Metabolism and Behavior) that are supported in part by COBRE (NIH 3 P30-GM118430) and NORC (NIH 2P30-DK072476) center grants from the National Institutes of Health. This research was supported by NIH 1R01DK103860 (R.C.N.). F.R.G. and S.E.F. were supported by a T32 fellowship (AT004094). Declaration of Interests: Authors have no commercial or financial conflicts of interest to report. The results are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation and do not constitute endorsement by the American College of Sports Medicine. Accepted for Publication: 15 July 2019. This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal. © 2019 American College of Sports Medicine

Effects of Exercise Training and Statin Use in People Living with HIV with Dyslipidemia Purpose To evaluate the effects of the combination of ET and statins in people living with HIV. Methods This was a randomized, double-blind, placebo-controlled clinical trial. Eighty-three people living with HIV were assigned to either placebo (PL), statins (STA), placebo + ET (PLET) or statins + ET (STAET) groups. Volunteers assigned to STA and STAET groups were administered 10 mg of rosuvastatin, whereas the PL and PLET groups were administered a placebo. PLET and STAET groups performed ET three times a week. Before and after the 12-week follow-up, the volunteers underwent to anthropometric assessment and blood collection to evaluate lipid profile, cardiovascular markers, inflammatory profile; a Doppler ultrasound examination, muscle strength (MS) and cardiorespiratory fitness (CF) tests were performed. Results There was a decrease in total cholesterol (TC), triglycerides (TG), low-density lipoprotein (LDL-c), C-reactive protein, fibrinogen, interleukin (IL)-1β and right carotid intima-media thickness (cIMT) in the STA, PLET, and STAET groups compared to PL group (p<0.001). Furthermore, there was a decrease in TC, TG, LDL, IL-1β, IL-6, and IL-8 levels and in left and right cIMT and an increase in HDL-c levels in the STAET groups compared to the STA (p<0.001) and PLET groups (p<0.001). There was an increase in IL-10 levels, peak-systolic velocity, end-diastolic velocity, wall shear rate in the PLET and STAET groups compared to the PL (p<0.001) and STA groups (p<0.001). The PLET and STAET groups reduced body fat mass, body fat percentage and increased lean body mass, MS and CF compared to PL (p<0.001) and STA (p<0.001) groups. Conclusion The combination of ET and statins is useful to enhance lipid and inflammatory profiles, reduce CVD markers, and improve Doppler ultrasound findings, MS and CF in people living with HIV. Corresponding author: Hugo Ribeiro Zanetti, Postgraduate Program in Health Science - Federal University of Uberlândia, Para Avenue 1720 – Umuarama – Uberlândia/MG, Brazil. Telephone number +55 (34) 3225 8628. E-mail: hugo.zanetti@hotmail.com We thank the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) for the supporting of this publication. Conflict of interest: The authors disclose no conflict of interest and state that the results of the present study do not constitute any endorsement by ACSM and declare that the results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 27 July 2019. © 2019 American College of Sports Medicine

Acute Exercise Effects Predict Training Change in Cognition and Connectivity Purpose Previous studies report memory and functional connectivity of memory systems improve acutely after a single aerobic exercise session or with training, suggesting the acute effects of aerobic exercise may reflect initial changes that adapt over time. In this trial, for the first time, we test the proof-of-concept of whether the acute and training effects of aerobic exercise on working memory and brain network connectivity are related in the same participants. Methods Cognitively normal older participants (N=34) were enrolled in a randomized clinical trial (NCT02453178). Participants completed fMRI resting state and a face working memory N-back task acutely after light and moderate intensity exercise and after a 12-week aerobic training intervention. Results Functional connectivity did not change more after moderate compared with light intensity training. However, both training groups showed similar changes in cardiorespiratory fitness (maximal exercise oxygen uptake, VO2peak), limiting group-level comparisons. Acute effects of moderate intensity aerobic exercise on hippocampal-cortical connections in the default network predicted training enhancements in the same connections. Working memory also improved acutely, especially following moderate intensity, and greater acute improvements predicted greater working memory improvement with training. Exercise effects on functional connectivity of right lateralized fronto-parietal connections were related to both acute and training gains in working memory. Conclusion Our data support the concept of acute aerobic exercise effects on functional brain systems and performance as an activity-evoked biomarker for exercise training benefits in the same outcomes. These findings may lead to new insights and methods for improving memory outcomes with aerobic exercise training. Corresponding author: Michelle W. Voss, W311 Seashore Hall, Iowa City, IA 52242-1407, Phone: 319-335-2057, Fax: 319-335-0191. Email: michelle-voss@uiowa.edu Conflicts of interest, acknowledgements, and source of funding: None of the authors declare a conflict of interest. Research support provided by 5R21AG048170 from the National Institutes of Health/National Institute on Aging. The results of the present study do not constitute endorsement by ACSM. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. Accepted for Publication: 19 July 2019. © 2019 American College of Sports Medicine

Input and Soft-Tissue Vibration Characteristics during Sport-Specific Tasks Purpose To assess the influence of sport-specific tasks on the characteristics of input and soft-tissue vibrations. Method Triaxial accelerometers were used to quantify the input (heel cup of the shoe) and soft-tissue vibrations of the gastrocnemius medialis and vastus lateralis muscles during seven sport-specific tasks performed by 10 healthy volunteers. A wavelet analysis was used to analyze the acceleration signals in the time-frequency domain. The energy and frequency of the input and soft-tissue vibrations, as well as the transmission of energy from the input to the muscles and the damping properties of soft tissues, were computed. Results Different inputs, energy transmissions and damping properties were found between the various movements. Landings and side cuts induced the greatest input frequency and energy, as well as the greatest soft-tissue vibration energy. These tasks produced up to three times greater energy than in-line running. Positive energy transmission was found for frequencies under 50 Hz and for frequencies up to 90 Hz for some movements, indicating a possible change in the natural frequency of vibration within muscle. Only small differences in damping properties were found, which may indicate that the attenuation of the vibration was not the priority during these tasks. Conclusion Athletes are subject to greater energy impacts and vibrations during some sport-specific tasks compared to running. It may be useful to decrease such input/vibration energy via the usage of footwear or compression tools in order to limit their potential deleterious effects on the musculoskeletal system. It is therefore recommended to quantify and control the number of impacts induced by the different sport-specific tasks. Corresponding author: Robin Trama, UFR STAPS 1, 27/29 Boulevard du 11 Novembre 1918, 69622 Villeurbanne Cedex, +33649850040, robin.trama@univ-lyon1.fr This study was financed by the European Regional Development Fund, FUI VIBRINNOV. The results of the study are presented clearly, honestly and without fabrication, falsification or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. None of the authors are in conflict of interest with regards to this research. Accepted for Publication: 18 July 2019. © 2019 American College of Sports Medicine

A Dual-Accelerometer System for Detecting Human Movement in a Free-living Environment Purpose Accurate measurement of various human movement behaviours are essential in developing 24-hour movement profiles. A dual accelerometer system recently showed promising results for accurately classifying a broad range of behaviours in a controlled laboratory environment. As a progressive step, the aim of this study is to validate the same dual-accelerometer system in semi free-living conditions in children and adults. The efficacy of several placement sites (e.g., wrist, thigh, back) were evaluated for comparison. Methods Thirty participants (15 children) wore three Axivity AX3 accelerometers alongside an automated clip camera (clipped to the lapel) that recorded video of their free-living environment (ground truth criterion measure of physical activity). Participants were encouraged to complete a range of daily-living activities within a two-hour timeframe. A random forest machine-learning classifier was trained using features generated from the raw accelerometer data. Three different placement combinations were examined (thigh-back, thigh-wrist, back-wrist), and their performance was evaluated using leave-one-out cross-validation for the child and adult samples separately. Results Machine learning models developed using the thigh-back accelerometer combination performed the best in distinguishing seven distinct activity classes with an overall accuracy of 95.6% in the adult sample, and eight activity classes with an overall accuracy of 92.0% in the child sample. There was a drop in accuracy (at least 11.0%) when other placement combinations were evaluated. Conclusions This validation study demonstrated that a dual accelerometer system previously validated in a laboratory setting also performs well in semi free-living conditions. Although these results are promising and progressive, further work is needed to expand the scope of this measurement system to detect other components of behaviour (e.g., activity intensity and sleep) that are related to health. Corresponding author: Tom Stewart, Auckland University of Technology, Private Bag 92006, Auckland 1142, New Zealand, Phone: +64 9 921 9999 ext 7855. E-mail: tom.stewart@aut.ac.nz AN received the 2018 AUT Human Potential Centre Fees Scholarship Award which funded the study. Participant incentives were covered using internal department funds. The results of this study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by ACSM. Competing interests. The authors declare that they have no competing interests. Accepted for Publication: 17 July 2019 © 2019 American College of Sports Medicine

Factors Associated with Persistently High Muscular Power from Childhood to Adulthood Purpose Child and adult muscular power have been shown to associate with contemporary cardiometabolic health. Muscular power typically persists (tracks) between childhood and adulthood. Few studies span childhood to adulthood, so we aimed to identify modifiable and environmental factors associated with the persistence or change in muscular power across the life course. Methods Prospective study examining 1,938 participants who had their muscular power (standing long jump distance) measured in 1985 as children aged 7-15-years and again 20-years later in adulthood (aged 26–36-years). A selection of objectively measured anthropometric characteristics (adiposity and fat-free mass), cardiorespiratory fitness (CRF), self-reported physical activity, dietary (quality and fruit, vegetable, protein intake) and sociodemographic data were available at both time-points. Muscular power was separated into thirds and participants were reported as having persistently low, decreasing, persistently moderate, increasing, or persistently high muscular power. Results Higher adiposity, lower physical activity, diet quality and socioeconomic status (SES) across the life course, and lower adult CRF were associated with persistently low muscular power. Lower adult protein intake and an increase in adiposity over time were associated with decreasing muscular power. An increase in fat-free mass was associated with a reduced probability of decreasing or persistently high muscular power, and an increased probability of increasing muscular power. Higher adult fruit intake was associated with increasing muscular power. Lower adiposity across the life course, higher adult CRF and SES, and higher child protein intake were associated with persistently high muscular power. Conclusion A healthy weight, good CRF, greater protein intake and high SES are important correlates of high muscular power maintained from childhood to adulthood. Correspondence: Brooklyn J. Fraser, Menzies Institute for Medical Research, University of Tasmania, Private Bag 23, Hobart 7001, Tasmania, Australia. E-mail: fraserbj@utas.edu.au The baseline study was supported by grants from the Commonwealth Departments of Sport, Recreation and Tourism, and Health; The National Heart Foundation; and the Commonwealth Schools Commission. The follow-up study was funded by grants from the National Health and Medical Research Council (211316), the National Heart Foundation (GOOH 0578), the Tasmanian Community Fund (D0013808) and Veolia Environmental Services. Sponsors included Sanitarium, ASICS and Target. CGM (100849), VC (100444) and SG (100446) are supported by National Heart Foundation of Australia Future Leader Fellowships. KJS is supported by NHMRC Early Career Fellowship (1072516). BJF is supported by the Patricia F Gordon Scholarship in Medical Research. Funding bodies and sponsors did not play a role in the study design, collection, analysis, or interpretation of data, in the writing of the manuscript, or the decision to submit the manuscript for publication. The authors declare no conflict of interest. The results of the study are presented clearly, honestly, and without fabrication, falsification, or inappropriate data manipulation. The results of the present study do not constitute endorsement by the American College of Sports Medicine. Accepted for Publication: 19 July 2019. © 2019 American College of Sports Medicine