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

Area of Science:

• Neuroscience
• Gerontology
• Motor Control

Background:

• Age-related neuromuscular decline is evident, but underlying cortical mechanisms are poorly understood.
• Transcranial magnetic stimulation (TMS) offers insights into corticospinal and intracortical function.

Purpose of the Study:

• To systematically review and meta-analyze age-related differences in corticospinal and intracortical function using TMS.
• To quantify age-related differences in maximal voluntary strength.

Main Methods:

• Systematic review and meta-analysis of 52 studies comparing younger and older adults.
• Assessed corticospinal excitability, cortical silent period, and intracortical inhibition/facilitation via TMS.
• Analyzed maximal isometric voluntary force as a secondary outcome.

Main Results:

• Older adults exhibited lower maximal voluntary force (SMD = -0.76) and reduced resting motor evoked potential amplitudes (SMD = -0.55).
• Reduced intracortical facilitation (SMD = -0.27) and prolonged cortical silent periods (SMD = 0.39) were observed in older adults.
• No significant age differences in short- or long-interval intracortical inhibition were found; differences were absent during active contractions.

Conclusions:

• Aging is associated with diminished resting corticospinal and intracortical excitability and reduced maximal strength.
• Prolonged cortical silent periods in older adults suggest altered cortical inhibition.
• Central neural alterations are plausible targets for interventions to mitigate age-related neuromuscular decline.