Jay R. Hydren

Human Muscle Protein Synthetic Responses during Weight-Bearing and Non-Weight-Bearing Exercise: A Comparative Study of Exercise Modes and Recovery Nutrition

Effects of conventional endurance (CE) exercise and essential amino acid (EAA) supplementation on protein turnover are well described. Protein turnover responses to weighted endurance exercise (i.e., load carriage, LC) and EAA may differ from CE, because the mechanical forces and contractile properties of LC and CE likely differ. This study examined muscle protein synthesis (MPS) and whole-body protein turnover in response to LC and CE, with and without EAA supplementation, using stable isotope amino acid tracer infusions. Forty adults (mean ± SD, 22 ± 4 y, 80 ± 10 kg, VO2peak 4.0 ± 0.5 L∙min-1) were randomly assigned to perform 90 min, absolute intensity-matched (2.2 ± 0.1 VO2 L∙m-1) LC (performed on a treadmill wearing a vest equal to 30% of individual body mass, mean ± SD load carried 24 ± 3 kg) or CE (cycle ergometry performed at the same absolute VO2 as LC) exercise, during which EAA (10 g EAA, 3.6 g leucine) or control (CON, non-nutritive) drinks were consumed. Mixed-muscle and myofibrillar MPS were higher during exercise for LC than CE (mode main effect, P < 0.05), independent of dietary treatment. EAA enhanced mixed-muscle and sarcoplasmic MPS during exercise, regardless of mode (drink main effect, P < 0.05). Mixed-muscle and sarcoplasmic MPS were higher in recovery for LC than CE (mode main effect, P < 0.05). No other differences or interactions (mode x drink) were observed. However, EAA attenuated whole-body protein breakdown, increased amino acid oxidation, and enhanced net protein balance in recovery compared to CON, regardless of exercise mode (P < 0.05). These data show that, although whole-body protein turnover responses to absolute VO2-matched LC and CE are the same, LC elicited a greater muscle protein synthetic response than CE.

U.S. Army physical demands study: Identification and validation of the physically demanding tasks of combat arms occupations

OBJECTIVES In 2013, the U.S. Army began developing physical tests to predict a recruits ability to perform the critical, physically demanding tasks (CPDTs) of combat arms jobs previously not open to women. The purpose of this paper is to describe the methodology and results of analyses of the accuracy and inclusiveness of the critical physically demanding task list. While the job analysis included seven combat arms jobs, only data from the 19D Cavalry Scout occupation are presented as the process was similar for all seven jobs. DESIGN Job analysis METHODS: As the foundation, senior subject matter experts from each job reviewed materials and reached consensus on the CPDTs and performance standards for each job. The list was reviewed by Army leadership and provided to the researchers. The job analysis consisted of reviewing job and task related documents and field manuals, observing >900 soldiers performing the 32 CPDTs, conducting two focus groups for each job, and analyzing responses to widely distributed job analysis questionnaires. RESULTS Of the 32 CPDTs identified for seven combat jobs, nine were relevant to 19D soldiers. Focus group discussions and job analysis questionnaire results supported the tasks and standards identified by subject matter experts while also identifying additional tasks. CONCLUSIONS The tasks identified by subject matter experts were representative of the physically demanding aspects of the 19D occupation.

Systematic Review and Meta-analysis of Predictors of Military Task Performance: Maximal Lift Capacity

Abstract Hydren, JR, Borges, AS, and Sharp, MA. Systematic review and meta-analysis of predictors of military task performance: maximal lift capacity. J Strength Cond Res 31(4): 1142–1164, 2017—Physical performance tests (e.g., physical employment tests, return-to-duty tests) are commonly used to predict occupational task performance to assess the ability of individuals to do a job. The purpose of this systematic review was to identify predictive tests that correlate well with maximal lifting capacity in military personnel. Three databases were searched and experts in the field were contacted, resulting in the identification of 9 reports confined to military personnel that presented correlations between predictor tests and job tasks that measured maximal lift capacity. These 9 studies used 9 variations of a maximal lift capacity test, which were pooled to evaluate comparisons. The predictive tests were categorized into 10 fitness domains, which in ranked order were as follows: body mass and composition, absolute aerobic capacity, dynamic strength, power, isometric strength, strength-endurance, speed, isokinetic strength, flexibility, and age. Limitations of these data include a restricted age range (95% confidence interval [95% CI], 20–35; no correlations to maximal lift capacity) and the limited number of comparisons available within the cited studies. Weighted mean correlations ( ) and 95% CI were calculated for each test. Lean body mass (kg) was the strongest overall predictor ( ; 95% CI, 0.697–0.966). Tests of dynamic strength had stronger correlations than strength endurance ( , 95% CI, 0.69–0.89 vs. , 95% CI, 0.21–0.61). The following 6 domains of physical performance predictive tests had pooled correlations of 0.40 or greater for combined-sex samples: dynamic strength, power, isometric strength, strength endurance, speed, and isokinetic strength. Anthropometric measures explain 24–54% of maximal lift capacity variance, and lean body mass alone accounts for ∼69%. This review provides summarized information to assist in the selection of predictive tests for maximal lifting capacity in military personnel.

Erratum to: Bone formation is suppressed with multi-stressor military training

immediate post-training measures. A repeated-measures ANOVA with time as the only factor was used to analyze data on the subset of 8 subjects who completed follow-up data collection. Results BAP and OCN significantly decreased by 22.8 ± 15.5 % (pre 41.9 ± 10.1; post 31.7 ± 7.8 ng/ml) and 21.0 ± 23.3 % (pre 15.0 ± 3.5; post 11.3 ± 2.1 ng/ ml), respectively, with training, suggesting suppressed bone formation. OCN returned to baseline, while BAP remained suppressed 2–6 weeks post-training. TRAP5b significantly increased by 57.5 ± 51.6 % (pre 3.0 ± 0.9; post 4.6 ± 1.4 ng/ml) from preto post-training, suggesting increased bone resorption, and returned to baseline 2–6 weeks post-training. PTH Increased significantly by 37.3 ± 45.2 % with training. No changes in CTX, calcium, or PTH were detected. Conclusions These data indicate that multi-stressor military training results in increased bone resorption and suppressed bone formation, with recovery of bone metabolism 2–6 weeks after completion of training.