Differential Effects of Military Training on Fat-Free Mass and Plasma Amino Acid Adaptations in Men and Women

Lee Margolis,James Mcclung,Kelly Williams,Stefan Pasiakos,Andrew Young,J Karl,Sonya Cable,Jennifer Rood

doi:10.3390/nu4122035

Abstract

Fat-free mass (FFM) adaptations to physical training may differ between sexes based on disparities in fitness level, dietary intake, and levels of plasma amino acids (AA). This investigation aimed to determine FFM and plasma AA responses to military training, examine whether adaptations differ between male and female recruits, and explore potential associations between FFM and AA responses to training. Body composition and plasma AA levels were assessed in US Army recruits (n = 209, 118 males, 91 females) before (baseline) and every three weeks during basic combat training (BCT), a 10-week military training course. Body weight decreased in men but remained stable in women during BCT (sex-by-time interaction, P < 0.05). Fifty-eight percent of recruits gained FFM during BCT, with more (P < 0.05) females (88%) gaining FFM than males (36%). Total plasma AA increased (P < 0.05) during BCT, with greater (P < 0.05) increases observed in females (17%) then in males (4%). Essential amino acids (EAA) and branched-chain amino acids (BCAA) were increased (P < 0.05) in females but did not change in males (sex-by-time interaction, P < 0.05). Independent of sex, changes in EAA (r = 0.34) and BCAA (r = 0.27) from baseline were associated with changes in FFM (P < 0.05); greater (P < 0.05) increases in AA concentrations were observed for those who gained FFM. Increases in FFM and plasma AA suggest that BCT elicits a more pronounced anabolic response in women compared to men, which may reflect sex-specific differences in the relative intensity of the combined training and physiological stimulus associated with BCT.

Highlights

Skeletal muscle anabolic adaptations to physical training may be influenced by habitual dietary intake, initial fitness level, and potentially, plasma amino acid (AA) concentrations
These data demonstrate that plasma amino acids (AA) and Fat-free mass (FFM) responses to military training differ by sex, as the percentage of female recruits who experienced gains in FFM
Data from the current study suggest that the intensity and volume of physical training during basic combat training (BCT) elicits an anabolic response in most

Summary

Introduction

Skeletal muscle anabolic adaptations to physical training may be influenced by habitual dietary intake, initial fitness level, and potentially, plasma amino acid (AA) concentrations. Initial fitness level may dictate the anabolic response to training, and trained adults typically exhibit greater FFM and AA levels as compared to untrained adults [4], they require a greater anabolic stimulus to elicit further hypertrophic gains [5]. Plasma AA responses to exercise may contribute to long-term anabolic adaptations to physical training. In contrast to acute exercise bouts, AA responses to training are not well described, and whether long-term AA responses to training and concomitant skeletal muscle adaptations differ between men and women has not been determined

Methods

Results

Conclusion