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Long-Term Endurance and Power Training May Facilitate Motor Unit Size Expansion to Compensate for Declining Motor Unit Numbers in Older Age.

  • Piasecki, M1
  • Ireland, A2
  • Piasecki, J3
  • Degens, H2, 4
  • Stashuk, D W5
  • Swiecicka, A6
  • Rutter, M K6, 7
  • Jones, D A2
  • McPhee, J S8, 9
  • 1 Clinical, Metabolic and Molecular Physiology, MRC-ARUK Centre for Musculoskeletal Ageing Research, National Institute for Health Research (NIHR) Nottingham Biomedical Research Centre, University of Nottingham, Nottingham, United Kingdom. , (United Kingdom)
  • 2 School of Healthcare Science, Manchester Metropolitan University, Manchester, United Kingdom. , (United Kingdom)
  • 3 Musculoskeletal Physiology Research Group, Sport, Health and Performance Enhancement Research Centre, School of Science and Technology, Nottingham Trent University, Nottingham, United Kingdom. , (United Kingdom)
  • 4 Institute of Sport Science and Innovations, Lithuanian Sports University, Kaunas, Lithuania. , (Lithuania)
  • 5 Department of Systems Design Engineering, University of Waterloo, Waterloo, ON, Canada. , (Canada)
  • 6 Division of Diabetes, Endocrinology and Gastroenterology, School of Medical Sciences, Faculty of Biology, Medicine and Health, The University of Manchester, Manchester, United Kingdom. , (United Kingdom)
  • 7 Manchester Diabetes Centre, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester, United Kingdom. , (United Kingdom)
  • 8 Department of Sport and Exercise Sciences, Musculoskeletal Science and Sports Medicine Research Centre, Manchester Metropolitan University, Manchester, United Kingdom. , (United Kingdom)
  • 9 Department of Physiology, University of Padova, Padova, Italy. , (Italy)
Published Article
Frontiers in Physiology
Frontiers Media SA
Publication Date
Jan 01, 2019
DOI: 10.3389/fphys.2019.00449
PMID: 31080415


The evidence concerning the effects of exercise in older age on motor unit (MU) numbers, muscle fiber denervation and reinnervation cycles is inconclusive and it remains unknown whether any effects are dependent on the type of exercise undertaken or are localized to highly used muscles. MU characteristics of the vastus lateralis (VL) were assessed using surface and intramuscular electromyography in eighty-five participants, divided into sub groups based on age (young, old) and athletic discipline (control, endurance, power). In a separate study of the biceps brachii (BB), the same characteristics were compared in the favored and non-favored arms in eleven masters tennis players. Muscle size was assessed using MRI and ultrasound. In the VL, the CSA was greater in young compared to old, and power athletes had the largest CSA within their age groups. Motor unit potential (MUP) size was larger in all old compared to young (p < 0.001), with interaction contrasts showing this age-related difference was greater for endurance and power athletes than controls, and MUP size was greater in old athletes compared to old controls. In the BB, thickness did not differ between favored and non-favored arms (p = 0.575), but MUP size was larger in the favored arm (p < 0.001). Long-term athletic training does not prevent age-related loss of muscle size in the VL or BB, regardless of athletic discipline, but may facilitate more successful axonal sprouting and reinnervation of denervated fibers. These effects may be localized to muscles most involved in the exercise.

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