Mitigation of Muscle Loss in Stressed Physiology: Military Relevance

Abstract

Military personnel may be exposed to circumstances (e.g., large energy deficits, sleep deprivation, cognitive demands, and environmental extremes) of external stressors during training and combat operations (i.e., operational stressors) that combine to degrade muscle protein. The loss of muscle protein is further exacerbated by frequent periods of severe energy deficit. Exposure to these factors results in a hypogonadal state that may contribute to observed decrements in muscle mass. In this review, lessons learned from studying severe clinical stressed states and the interventions designed to mitigate the loss of muscle protein are discussed in the context of military operational stress. For example, restoration of the anabolic hormonal status (e.g., testosterone, insulin, and growth hormone) in stressed physiological states may be necessary to restore the anabolic influence derived from dietary protein on muscle. Based on our clinical experiences, restoration of the normal testosterone status during sustained periods of operational stress may be advantageous. We demonstrated that in severe burn patients, pharmacologic normalization of the anabolic hormonal status restores the anabolic stimulatory effect of nutrition on muscle by improving the protein synthetic efficiency and limiting amino acid loss from skeletal muscle. Furthermore, an optimal protein intake, and in particular essential amino acid delivery, may be an integral ingredient in a restored anabolic response during the stress state. Interventions which improve the muscle net protein balance may positively impact soldier performance in trying conditions.

Effects of gradual weight loss v. rapid weight loss on body composition and RMR: a systematic review and meta-analysis

“…Several factors could be responsible for these results. First, it is well established that increasing dietary protein may attenuate the WL-induced reduction in muscle mass (58,59) . Some (two of seven) studies (31,32) included in the meta-analysis did not report sufficient dietary information for these variables to be considered in the present analysis, meaning it is possible that the percentage of energy derived from different macronutrients, notably protein, could have differed between experimental arms or studies.…”

Energy Expenditure and Changes in Body Composition During Submarine Deployment—An Observational Study “DasBoost 2-2017”

“…This data therefore suggests, that submariners are at increased risk for muscle mass loss. The causes of the accelerated reduction in fat-free mass remain speculative, but may relate to the irregular daily rhythm induced by shift-work [25,26], voided sunlight/vitamin D deficiency [27,28], chronic stress [10], and altered dietary pattern, e.g., low protein [29], low eating frequency [30,31]. Notably, in other studies on submariners, a reduction in fat-free mass was not observed [7,32], and vitamin D supplementation did not increase fat-free mass during 3-month submarine deployment [6].…”

“…Specifically, deployment settings onto submarines reduce opportunity for activity, void access to fresh foods and sunlight, and require shift-work of 6 h on-duty and 6 h off-duty. As a result, submarine deployment has been shown to impair metabolic health, including promotion of obesity, metabolic syndrome and reduced bone health [5][6][7][8][9][10][11].…”

Alaska backcountry expeditionary hunting promotes rapid improvements in metabolic biomarkers in healthy males and females

“…The atrophy of skeletal muscle during weight loss has been studied extensively in a wide range of individuals due to its inextricable link to deleterious alterations in physical function and/or performance (Cava et al, 2017; Church et al, 2019; Palus et al, 2014; Tassone & Baker, 2017). Our ABEH immersion resulted in negative energy balance largely due to the influence of sustained physical activity on TEE, coupled with the various barriers to eating enough to maintain energy balance.…”