Effect of very old age on anconeus motor unit loss and compensatory remodelling

ABSTRACT Introduction: It is not known how the process of compensatory remodeling through collateral reinnervation continues into very old age (>80 years) or whether there is a limit to effective motor unit (MU) reinnervation. Therefore, we explore electrophysiological properties related to motor unit number estimates (MUNEs) in very old participants (79–90 years of age) compared with young controls (25–29 years of age). Methods: Decomposition‐enhanced spike‐triggered averaging was used to collect surface and intramuscular electromyography information from the anconeus to derive a MUNE. Results: Young participants had a MUNE of ∼38 and ∼25 at 30% and 50% root mean squared maximum voluntary contraction (RMSMVC) with surface motor unit potentials (S‐MUPs) of ∼145 μV and 236 μV, respectively. Older participants had a MUNE of ∼23 and ∼16 at 30% and 50% RMSMVC with S‐MUPs of 168 μV and 232 μV, respectively. Discussion: In this muscle, an age limit to successful remodeling through collateral reinnervation, to compensate for the presumed ongoing losses of MUs, may have been surpassed. Muscle Nerve 57: 659–663, 2018