Central adaptations to repetitive grasping in healthy aging.

Augmented cortical activity during repetitive grasping mitigates repetition-related decrease in cortical efficiency in young adults. It is unclear if similar processes occur with healthy aging. We recorded movement-related cortical potentials (MRCP) during 150 repetitive handgrip contractions at 70% of maximal voluntary contraction (MVC) in healthy young (n = 10) and old (n = 10) adults. Repetitions were grouped into two Blocks (Block 1 and 2: repetitions 1-60 and 91-150, respectively) and analyzed separately to assess the effects of aging and block. EMG of the flexor digitorum superficialis and handgrip force were also recorded. No changes in EMG or MVC were observed across blocks for either group. Significant interactions (P < 0.05) were observed for MRCPs recorded from mesial (FCz, Cz, CPz) and motor (C1, C3, Cz) electrode sites, with younger adults demonstrating significant increases in MRCP amplitude. Focal MRCP activity in response to repetitive grasping resulted in minimal changes (i.e. Block 1 versus Block 2) in older adults. Central adaptive processes change across the lifespan, showing increasingly less focal activation in older adults during repetitive grasping. Our findings are consistent with previous paradigms demonstrating more diffuse cortical activation during motor tasks in older adults.