Across 41 randomized controlled trials encompassing 3,141 adults aged 60 and older, resistance exercise emerged as the sole intervention significantly improving muscle-specific strength — a metric that normalizes force output by muscle mass — yielding a standardized mean difference of 0.61 (95% CI: 0.27–0.94). Aerobic exercise, concurrent training, nutritional supplementation, caloric restriction, and combined exercise-plus-nutrition protocols all failed to reach statistical significance on this measure. High heterogeneity plagued every intervention category (I² = 81% for resistance training alone), signaling wide variability in protocols, populations, and outcome tools.
The finding reframes how we should interpret sarcopenia research. Most prior literature celebrates gross muscle mass or raw strength gains; muscle-specific strength — essentially a proxy for muscle quality — is arguably the more clinically meaningful target, predicting fall risk and functional independence better than mass alone. The exclusive effectiveness of resistance training here aligns mechanistically with its unique capacity to drive neuromuscular adaptations, fiber-type remodeling, and intramuscular fat reduction simultaneously.
The null results for protein supplementation are provocative but should not be over-interpreted. Many nutritional trials are underpowered, use heterogeneous dosing, and were not designed with muscle-specific strength as a primary endpoint. The I² problem also cautions against strong conclusions. This meta-analysis is confirmatory and directionally important, but the high heterogeneity and absence of dose-response data for resistance protocols leave the "optimal prescription" question open for practitioners designing elder-care programs.
