Only lifting improved strength per unit of muscle in older adults

Sarcopenia, the age-related loss of muscle, is usually framed as a problem of shrinking mass, but researchers increasingly focus on muscle-specific strength: the force a muscle produces relative to its size. Deficient muscle-specific strength is now recognised as a key component of sarcopenia, because a muscle can hold its size on paper while becoming functionally weaker. Plenty of interventions promise to keep older adults strong, from lifting weights to nutritional supplements, yet nobody had systematically reviewed which of them actually improve strength relative to muscle mass.

The authors searched major databases for randomised controlled trials in adults aged 60 or older, with interventions lasting at least 8 weeks and muscle strength measured after normalising for muscle mass. In total 41 trials with 3,141 participants qualified. The interventions covered resistance exercise, nutritional supplementation, aerobic exercise, concurrent training, combined exercise and nutrition, caloric restriction and other therapies. Results were pooled using random-effects models, and the consistency of findings across trials was formally assessed.

Resistance exercise significantly improved muscle-specific strength, with a standardised effect of 0.61, a moderate benefit, although the trials disagreed with each other considerably. None of the other approaches cleared the bar: aerobic exercise, concurrent training, combined exercise and nutrition, and nutritional supplementation all failed to show significant improvements in muscle-specific strength. Variation between studies was high across the board, which tempers confidence in the precise size of every estimate.

This review reinforces resistance training's position as the cornerstone intervention for ageing muscle, and extends that case to muscle quality specifically rather than just size or raw strength. It also complicates the popular idea that supplements or aerobic work can substitute for lifting where muscle-specific strength is concerned, though the authors stress these results are inconclusive rather than negative. They call for further well-designed trials exploring diverse exercise regimens and nutritional interventions to settle the question.

For anyone thinking about strength in later life, this is a reason to see resistance exercise as the intervention with the clearest evidence for improving the quality of muscle, not merely its bulk. It is equally a reason for scepticism towards claims that a supplement alone will restore strength, since pooled trial evidence could not show that. Absence of proof is not proof of absence, but for now the burden sits with the alternatives.