Lean Muscle Mass in Special Operations Forces: Implications for Performance, Selection, and Injury Reduction A...

Oftentimes, special operations forces (SOF) function in near-extreme physical and psychological conditions demanding exceptional physiological resistance. Strength and aerobic fitness are well-established predictors of SOF performance, but the role of lean muscle mass (LM) within military tests and training paradigms is under-researched. The purpose of this narrative review is to synthesize evidence on the role of LM for SOF selection success, physical performance, and injury prevention.

A comprehensive literature search was conducted across six databases (PubMed/MEDLINE, Scopus, Web of Science, EBSCO, Military Medicine archives, DTIC) from January 2001 to July 2025. Studies were included if they examined LM in SOF populations and reported on performance, selection, or injury outcomes.

Twenty-eight studies examining 2,239 SOF operators and candidates met the inclusion criteria. LM emerged as a significant predictor of operational performance, with strong correlations to load carrying capacity (r = 0.68) and military-specific tasks. Selected SFAS candidates possessed higher LM than nonselected peers (67.2 ± 7.3 kg vs. 61.9 ± 7.6 kg; d = 0.71, large effect). Each kilogram increase in arm lean mass increased the odds of casualty drag completion by nearly 12-fold (OR = 11.69; 95% CI: 3.84-35.60). Higher LM was associated with reduced musculoskeletal injury (MSKI) risk when coupled with movement symmetry; however, operators with >25% movement asymmetry and body mass >81.8 kg showed 100% injury rates. Operational deployments resulted in substantial LM degradation (4.6% loss) with disproportionate strength decline (11.7%), driven by energy deficits averaging 2,200 kcal/day and hormonal disruption.

Higher LM was associated with favorable outcomes across performance, selection, and injury domains in observational studies, though causal relationships remain unestablished. Despite the limited number of studies that directly assess SOF populations, large effect sizes are shown in SFAS selection, but are susceptible to confounding variables. Contradictory evidence exists regarding optimal body mass and injury interactions. Randomized controlled trials comparing LM-focused versus alternative preparation strategies are needed to establish causality before operational implementation. Current evidence identifies LM as worthy of experimental investigation but insufficient to support definitive recommendations for selection preparation or operational preservation protocols.