Age-Related Differences in Corticospinal Function and Muscle Strength: A Systematic Review and Meta-Analysis

Age-related declines in neuromuscular performance are well documented; however, the cortical processes underlying these changes remain unclear. This systematic review and meta-analysis compared younger and older adults across key transcranial magnetic stimulation measures of corticospinal and intracortical function, including corticospinal excitability, cortical silent period, intracortical facilitation and intracortical inhibition. Age-related differences in maximal voluntary strength were also quantified as a secondary outcome. A comprehensive literature search identified 52 eligible studies from 1682 records. Methodological quality was evaluated using a modified Downs and Black checklist, and the certainty of evidence was assessed using the GRADE approach. A random-effects model was applied to calculate standardised mean differences (SMDs) with 95% confidence intervals (CIs). Compared to younger adults, older adults produced lower maximal isometric voluntary force (SMD = -0.76) and exhibited reduced resting motor evoked potential amplitudes (SMD = -0.55) and intracortical facilitation (SMD = -0.27). These age-related differences were not observed during active contractions. Cortical silent period duration was longer in older adults (SMD = 0.39). No age-related differences were found in short- or long-interval intracortical inhibition. These findings indicate that ageing is associated with reduced resting corticospinal and intracortical excitability, prolonged cortical silent periods and lower maximal voluntary strength. As neural and strength outcomes were analysed independently, a causal relationship cannot be established, but the parallel pattern points to central neural alterations as plausible targets for future interventions aimed at mitigating age-related neuromuscular decline.