Motor Unit Number Estimates in Masters Runners

Abstract

These results demonstrate that lifelong high-intensity physical activity could potentially mitigate the loss of MU associated with aging well into the seventh decade of life.

The influence on sarcopenia of muscle quality and quantity derived from magnetic resonance imaging and neuromuscular properties

“…Hence, the functional effects of muscle structure decline may not become apparent until later in the aging process as shown by our results of decreased absolute strength concomitant with a loss of functional MUs owing to deficient collateral reinnervation in older men. Our MUNE results are consistent with previous research on the TA showing an age-related loss of functioning MUs (McNeil et al 2005b;Power et al 2010). In the present study, an age difference of 45 years between the young and old group showed a~25 % lower value in mean MUNE, whereas with a~10-year difference between two old groups, the MUNE was lower by~27 %.…”

“…When remolded MUs with a large number of muscle fibers die (decreased MUNE), a larger amount of excitable muscle mass (decreased CMAP and CSA) is lost, resulting in greater loss of muscle mass and consequently, reduced absolute strength as observed here in the older men. However, high levels of physical activity in old age have been shown to mitigate the loss of MUs, excitable muscle mass (Power et al 2010) and maintain muscle fiber quality (D'Antona et al 2007).…”

“…For decomposition-enhanced spike-triggered averaging (DE-STA) measures that include an estimate of the number of functional motor units (MUNE), intramuscular EMG signals were recorded via a disposable concentric needle electrode with a recording surface of 0.03 mm 2 (Model N53153; Teca, Hawthorne, New York) inserted into the TA, 5-10 mm proximal to the active surface electrode. The MUNE technique was performed similarly to what we have reported previously (Dalton et al 2008;McNeil et al 2005b;Power et al 2012aPower et al , 2010. Electromyography data were acquired using customized software on a Neuroscan Comperio system (Neurosoft, El Paso, Texas).…”

Motor unit loss is accompanied by decreased peak muscle power in the lower limb of older adults

“…Reductions in MUNEs have been reported in a number of upper [13,[32][33][34][35], and lower limb [10,11,[36][37][38][39] muscles studies. Our obtained values for MU…”

“…There are several factors that contribute to the development of sarcopenia with age including genetic predisposition, excitation-contraction uncoupling, altered diet, lack of exercise, and changes in endocrine function [7,8]; however motor unit (MU) loss, and associated denervation of skeletal muscle, is one aspect of typical human aging that has been extensively studied [7,[9][10][11][12][13] and is considered to be one of the primary factors leading to age-related muscle weakness and loss of muscle mass.…”