Older lifters get stronger by waking the nervous system, not just growing muscle

Getting weaker with age is usually blamed on losing muscle, but atrophy only explains part of the decline. The nervous system changes too: older adults often cannot voluntarily activate all of a muscle's capacity, and the opposing muscles may work against a movement more than they need to. If training can restore that neural drive, then strength gains in later life would not depend on muscle growth alone. This review set out to establish how much of the strength older people gain from exercise comes from these neuromuscular changes rather than from bigger muscles.

The authors systematically searched the literature for studies reporting how exercise affects two neural measures in older people: voluntary muscle activation, which is how completely a person can switch a muscle on, and antagonist co-activation, which is how much the opposing muscle fires during a movement. Seventeen relevant studies were identified. Four investigated voluntary activation, eight investigated antagonist co-activation and five looked at both. The results were then pooled in a meta-analysis using weighted mean differences.

Exercise improved voluntary activation in the plantar flexors, the muscles that point the foot, by 8.8%, and in the knee extensors by 1.8%, and both improvements were statistically clear. Crucially, people who began with lower activation levels gained the most activation capacity from training. The picture for antagonist co-activation was different: there was no significant overall effect during ankle plantar flexion or knee extension, whichever way the studies were analysed. So the neural benefit showed up in switching muscle on, not in quieting the opposition.

The findings support the idea that strength gains from resistance training in older adults are partly neural, which fits the long-standing observation that strength often improves before muscle size does. They also clarify which neural mechanism matters: the evidence favours improved voluntary activation, while the role of antagonist co-activation remains inconsistent across studies. The authors call for more research to pin down whether reducing co-activation contributes anything to strength gains at all. The review is confined to the lower limbs, so the upper body is an open question.

This is a reason to think strength training in later life pays off even when the tape measure barely moves: some of the gain happens in the wiring, not the muscle. It is also a reason for the people who feel weakest to be encouraged rather than put off, because those starting with the lowest activation improved the most. The evidence here concerns older adults and lower-body muscles, so it describes where the strongest proof currently sits rather than a universal rule.