Our group has shown a greater number of functioning motor units (MU) in a cohort of highly-active older(~65y) masters runners relative to age-matched controls. Owing to the precipitous loss in the number of functioning MUs in the 8th and 9th decade of life it is unknown whether older world class octogenarian masters athletes (MA) would also have greater numbers of functioning MUs (MUNE) compared with age-matched controls. We measured MU numbers and neuromuscular transmission stability in the tibialis anterior of world champion MAs (~80y), and compared the values to healthy age-matched controls (~80y). Decomposition-enhanced spike-triggered averaging was used to collect surface and intramuscular electromyography signals during dorsiflexion at ~25% of maximum voluntary isometric contraction(MVC). Near fibre (NF) MU potential analysis was used to assess neuromuscular transmission stability. For the MAs as compared with age-matched controls; the amount of excitable muscle mass (CMAP) was 14% greater (p less than 0.05), there was a trend (p=0.07) towards a 27% smaller surface detected motor unit potential - representative of less collateral reinnervation, and 28% more functioning MUs (p less than 0.05). Additionally, the MAs had greater MU neuromuscular stability than the controls as indicated by lower NF jitter and jiggle values (p less than 0.05). These results demonstrate that high performing octogenarians better maintain neuromuscular stability of the MU and mitigate the loss of MUs associated with aging well into the later decades of life during which time the loss of muscle mass and strength become functionally relevant. Future studies need to identify the concomitant roles genetics and exercise play in neuroprotection.
Thursday, April 07, 2016
Muscle mass and nerve control enhanced in octogenarian athletes.
Power et al. expand their earlier studies on active runners ~65 years old to find ~14% greater muscle mass and ~28% more functioning motor nerve units in octogenarian masters athletes than in healthy age-matched controls.