Motor unit number estimation and neuromuscular fidelity in 3 stages of sarcopenia

• Published in: Muscle & nerve Vol. 55; no. 5; pp. 676 - 684
• Main Authors: Gilmore, Kevin J., Morat, Tobias, Doherty, Timothy J., Rice, Charles L.
• Format: Journal Article
• Language: English
• Published: United States Wiley Subscription Services, Inc 01.05.2017
• Subjects: Aged; Aged, 80 and over; aging; Aging - physiology; Electromyography; Female; Hand Strength - physiology; human; Humans; Male; motor neuron; Motor Neurons - physiology; muscle; Muscle Contraction - physiology; Muscle Strength - physiology; Muscle, Skeletal - physiopathology; Neuromuscular Junction - physiopathology; Sarcopenia; Sarcopenia - physiopathology; strength; aging; strength; human; electromyography; motor neuron; muscle
• ISSN: 0148-639X; 1097-4598
• DOI: 10.1002/mus.25394

ABSTRACT Introduction: Loss of motor units (MUs) and alterations in MU properties are major factors in development of sarcopenia. The purpose of this study was to compare MU properties among 3 groups categorized as either pre‐sarcopenic (n = 7), sarcopenic (n = 7), or severely sarcopenic (n = 5), all with similarly aged subjects (75–82 years). Methods: Using decomposition‐enhanced quantitative electromyography, MU number estimates and neuromuscular stability measures of near‐fiber (NF) jitter and jiggle were derived in addition to contractile properties of ankle dorsiflexors. Results: MU number estimates were similar across groups; however, maximal voluntary strength in the severe sarcopenia group was 27% and 37% less than the sarcopenic and pre‐sarcopenic groups, respectively. Moreover, NF jiggle was 31% greater in the severe group compared with pre‐sarcopenia, NF jitter was 43% greater in the severe group compared with the pre‐sarcopenic group. Conclusion: Unlike MU number estimates, strength and MU stability differed across groups and related to degree of sarcopenia. Muscle Nerve 55: 676–684, 2017