Long-term high-level exercise promotes muscle reinnervation with age

Authors: Mosole S(1), Carraro U(1), Kern H(2,3), Loefler S(2), Fruhmann H(2), Vogelauer M(3), Burggraf S(2), Mayr W(4), Krenn M(4), Paternostro-Sluga T(5), Hamar D(6), Cvecka J(6), Sedliak M(6), Tirpakova V(6), Sarabon N(7), Musarò A(8), Sandri M(9), Protasi F(10), Nori A(11), Pond A(12), Zampieri S(1,2)

Source: J Neuropathol Exp Neurol. 2014 Apr;73(4):284-94.

DOI: 10.1097/NEN.0000000000000032

Keywords: Aging, Coexpression of fast and slow myosin heavy chains, Denervation and reinnervation, Fiber-type grouping, Human skeletal muscle, Recreational sport activity

Abstract:

The histologic features of aging muscle suggest that denervation contributes to atrophy, that immobility accelerates the process, and that routine exercise may protect against loss of motor units and muscle tissue. Here, we compared muscle biopsies from sedentary and physically active seniors and found that seniors with a long history of high-level recreational activity up to the time of muscle biopsy had 1) lower loss of muscle strength versus young men (32% loss in physically active vs 51% loss in sedentary seniors); 2) fewer small angulated (denervated) myofibers; 3) a higher percentage of fiber-type groups (reinnervated muscle fibers) that were almost exclusive of the slow type; and 4) sparse normal-size muscle fibers coexpressing fast and slow myosin heavy chains, which is not compatible with exercise-driven muscle-type transformation. The biopsies from the old physically active seniors varied from sparse fiber-type groupings to almost fully transformed muscle, suggesting that coexpressing fibers appear to fill gaps. Altogether, the data show that long-term physical activity promotes reinnervation of muscle fibers and suggest that decades of high-level exercise allow the body to adapt to age-related denervation by saving otherwise lost muscle fibers through selective recruitment to slow motor units. These effects on size and structure of myofibers may delay functional decline in late aging.Trial registration: ClinicalTrials.gov (NCT01679977).

Affiliations:

1 Laboratory of Translation Myology, Department of Biomedical Sciences, University of Padua, Padua, Italy
2 Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Vienna, Austria
3 Department of Physical Medicine and Rehabilitation, Wilhelminenspital, Vienna, Austria
4 Center of Biomedical Engineering and Physics, Medical University of Vienna, Vienna, Austria
5 University Clinic for Physical Medicine and Rehabilitation, Medical University of Vienna, Vienna, Austria
6 Faculty of Physical Education and Sport, Comenius University, Bratislava, Slovakia
7 Science and Research Centre, Institute for Kinesilogical Research, University of Primorska, Koper, Slovenia
8 DAHFMO-Unit of Histology and Medical Embryology, IIM, Sapienza University of Rome, Rome, Italy
9 Venetian Institute of Molecular Medicine, Dulbecco Telethon Institute, and Department of Biomedical Science, University of Padua, Padua, Italy
10 CeSI-Center for Research on Aging, and DNIDepartment of Neuroscience and Imaging, University G. d’Annunzio of Chieti, Chieti, Italy
11  
12 Anatomy Department, Southern Illinois University School of Medicine, Carbondale, Illinois