Changes in cutaneomuscular reflex responses in relation to normal ageing in man.

Changes in cutaneomuscular reflex responses (CMRs) have been studied in relation to normal ageing in man. Multiunit surface EMG signals were recorded from right and left first dorsal interosseous (1DI) hand muscles from 23 elderly adults (mean age 71.1, range 58-88 years) and 11 young adults (mean age 25.9, range 19-31 years). Subjects (1) performed index finger abduction and (2) gripped a dowel while concomitant stimulation of the digital nerves of the index finger was delivered at x2.5 threshold for perception. The E1 spinally mediated components of the CMRs recorded from 1DI were significantly smaller in the elderly subjects compared with young subjects for both tasks. The I1 and E2 transcortical components did not show a significant change in size with age although the incidence of I1 components was significantly reduced in the elderly subjects.