Kevin J Gilmore1, Tobias Morat2, Timothy J Doherty3,4, Charles L Rice1,5. 1. School of Kinesiology, Faculty of Health Sciences, The University of Western Ontario, London, Ontario, Canada. 2. German Sport University Cologne, Institute of Movement and Sport Gerontology, Cologne, Germany. 3. Department of Clinical Neurological Sciences, The University of Western Ontario, London, Ontario, Canada. 4. Department of Physical Medicine and Rehabilitation, The University of Western Ontario, London, Ontario, Canada. 5. Department of Anatomy and Cell Biology, Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario N6G 1H1, Canada.
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.
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.
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