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Updated: May 2, 2026

Application of Chronic Stimulation to Study Contractile Activity-induced Rat Skeletal Muscle Phenotypic Adaptations
Published on: January 25, 2018
Long-term high-level exercise promotes muscle reinnervation with age
Simone Mosole1, Ugo Carraro, Helmut Kern
1From the Laboratory of Translation Myology, Department of Biomedical Sciences, University of Padua, Padua, Italy (SM, UC, AN, SZ); Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria (HK, SL, HF, SB, SZ); Department of Physical Medicine and Rehabilitation, Wilhelminenspital, Vienna, Austria (HK, MV); Center of Biomedical Engineering and Physics, Medical University of Vienna, Vienna, Austria (WM, MK); Department of Physical Medicine and Rehabilitation, Medical University of Vienna, Vienna, Austria (TP-S); Faculty of Physical Education and Sport, Comenius University, Bratislava, Slovakia (DH, JC, MSedliak, VT); Science and Research Centre, Institute for Kinesilogical Research, University of Primorska, Koper, Slovenia (NS); DAHFMO-Unit of Histology and Medical Embryology, IIM, Sapienza University of Rome, Rome, Italy (AM); Venetian Institute of Molecular Medicine, Dulbecco Telethon Institute, and Department of Biomedical Science, University of Padua, Padua, Italy (MSandri); CeSI-Center for Research on Aging, and DNI-Department of Neuroscience and Imaging, University G. d'Annunzio of Chieti, Chieti, Italy (FP); and Anatomy Department, Southern Illinois University School of Medicine, Carbondale, Illinois (AP).
Regular exercise preserves muscle strength and fiber integrity in seniors. High-level physical activity promotes muscle reinnervation, counteracting age-related muscle loss and potentially delaying functional decline.
Area of Science:
- Gerontology
- Muscle Physiology
- Exercise Science
Background:
- Aging muscle undergoes denervation, leading to atrophy.
- Immobility accelerates muscle loss, while exercise may offer protection.
- Understanding the impact of long-term physical activity on aging muscle is crucial.
Purpose of the Study:
- To compare muscle biopsies from sedentary and physically active seniors.
- To investigate the effects of long-term high-level recreational activity on muscle structure and function in aging.
- To determine if exercise can mitigate age-related muscle denervation and atrophy.
Main Methods:
- Histologic examination of muscle biopsies from sedentary and physically active seniors.
- Comparison of muscle strength loss between active and sedentary seniors and young men.
- Analysis of myofiber characteristics, including size, angulation, fiber-type grouping, and myosin heavy chain coexpression.
Main Results:
- Physically active seniors exhibited less muscle strength loss (32%) compared to sedentary seniors (51%).
- Fewer small angulated (denervated) myofibers were observed in active seniors.
- Active seniors showed a higher percentage of slow-type reinnervated muscle fibers (fiber-type grouping).
- Sparse muscle fibers coexpressing fast and slow myosin heavy chains were noted in active seniors.
Conclusions:
- Long-term physical activity promotes reinnervation of muscle fibers in aging individuals.
- Decades of exercise enable adaptation to age-related denervation by preserving muscle fibers via slow motor unit recruitment.
- These adaptations may delay functional decline in late aging by maintaining myofiber size and structure.
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