Differential modulation of corticomotor excitability in older compared to young adults following a single bout of strength-exercise

Evidence shows corticomotor plasticity diminishes with age. Nevertheless, whether strength -training, a proven intervention that induces corticomotor plasticity in younger adults, also takes effect in older adults, remains untested. This study examined the effect of a single -session of strength -exercise on corticomotor plasticity in older and younger adults. Thirteen older adults (72.3 +/- 6.5 years) and eleven younger adults (29.9 +/- 6.9 years), novice to strength -exercise, participated. Strength -exercise involved four sets of 6-8 repetitions of a dumbbell biceps curl at 70-75% of their one -repetition maximum (1-RM). Muscle strength, cortical, corticomotor and spinal excitability, before and up to 60 -minutes after the strength -exercise session were assessed. We observed significant changes over time (p < 0.05) and an interaction between time and age group (p < 0.05) indicating a decrease in corticomotor excitability (18% p < 0.05) for older adults at 30- and 60 -minutes post strength -exercise and an increase (26% and 40%, allp < 0.05) in younger adults at the same time points. Voluntary activation (VA) declined in older adults immediately post and 60 -minutes post strength -exercise (36% and 25%, all p < 0.05). Exercise had no effect on the cortical silent period (cSP) in older adults however, in young adults cSP durations were shorter at both 30- and 60- minute time points (17% 30 -minute post and 9% 60 -minute post, p < 0.05). There were no differences in short -interval cortical inhibition (SICI) or intracortical facilitation (ICF) between groups. Although the corticomotor responses to strength -exercise were different within groups, overall, the neural responses seem to be independent of age.