Nerve-firing differences with age vary across leg muscles
Electrical recordings from 30 young and 30 older adults linked age to different firing patterns depending on the leg muscle and effort level.
Limit: Nerve-current activity was estimated indirectly rather than measured directly
Edited by Boris Djordjevic · AgingResearch.News
Thirty young adults averaging 24 years and 30 older adults averaging 73 took part in a cross-sectional observational study. Each group included 15 women; participants had low to moderate physical activity. Researchers used scans, strength tests and electrical recordings during contractions at 30%, 50% and 70% of maximum force.
A motor unit is a nerve cell and the muscle fibers it controls. Older adults were weaker in both tasks. Their motor units fired more slowly at all tested effort levels in a front-of-shin muscle, but only at 30% and 50% in an outer-thigh muscle. A measure estimating how nerve currents help sustain firing was lower in older adults at all three levels in the shin muscle, but only at 70% in the thigh muscle. Its increase with effort was smaller in both muscles.
Why it matters
The authors suggest that age-related weakness likely depends more on muscle structure in muscles that straighten the knee, and more on nerve function in muscles that lift the foot.
Caveats
The study compared age groups rather than following people as they aged, and nerve-current activity was estimated indirectly. It excluded sedentary or systematically trained people and those with cardiovascular, neurological or respiratory disorders or lower-limb injuries.
- Age-related strength loss
- Acceleration and attenuation slopes
- Ascending discharge rate non-linearity
- Discharge rate hysteresis
- Motor unit discharge rate
- Humans
The paper
Age-related differences in motor unit discharge rate modulation across contraction levels
Loughborough University
GeroScience, Jun 30, 2026, Open access
