Amino acids plus lifting boosted strength in older adults, not muscle size

Sarcopenia, the age-related loss of muscle and strength, raises the risk of falls, frailty and lost independence in later life. Resistance training is the cornerstone of managing it, yet many older adults struggle to rebuild strength through lifting alone. Amino acid-based supplements, including essential amino acids, branched-chain amino acids, leucine and the leucine derivative HMB, are widely sold on the promise of amplifying training gains. Whether they genuinely add anything on top of a structured training programme in people who already have sarcopenia has remained an open question, which is exactly what this analysis set out to answer.

The researchers searched four major medical databases up to February 2025 for randomised controlled trials comparing resistance training plus an amino acid-based supplement against resistance training alone in older adults with sarcopenia. Nine trials covering 496 participants met the criteria. Results were pooled using a random-effects model, the risk of bias in each trial was assessed with a standard Cochrane tool, and the certainty of the overall evidence was formally graded. Subgroup analyses then probed whether factors such as baseline protein intake, training frequency, supplement type, intervention setting and the presence of co-nutrients changed the outcome.

Adding amino acid supplementation to resistance training produced significantly better handgrip strength, faster gait speed, higher scores on the Short Physical Performance Battery and quicker times on the five times sit-to-stand test than training alone. Muscle size told a different story: neither skeletal muscle mass index nor appendicular skeletal muscle mass improved significantly. The certainty of the evidence was rated low to very low throughout. Subgroup analyses suggested the response varied with baseline protein intake, the setting of the intervention, the type of amino acid supplement, how often participants trained, and whether the supplement included other nutrients alongside the amino acids.

The result sits comfortably alongside the established view that resistance training is the foundation of sarcopenia management, while complicating a common assumption: that if supplements work at all, they work by building visible muscle. Here the benefits showed up in strength and function rather than mass, which matters because function is what predicts independence in later life. The low certainty of the evidence and the strong influence of modifying factors leave big questions open, including which type of supplement works best, whether people already eating plenty of protein gain anything extra, and whether the functional improvements last.

For anyone training into older age, or helping a parent do so, this is a reason to think of amino acid supplements as a possible booster for strength and everyday function rather than a shortcut to bigger muscles. It is also a reason to keep expectations modest, because the evidence was graded low to very low certainty and the benefit appeared to depend on existing protein intake and how often people trained. The lifting itself remains the non-negotiable part of the equation; the supplement question is still being worked out.