Reinnervation of Vastus lateralis is increased significantly in seniors (70-years old) with a lifelong history of high-level exercise

Authors: Simone Mosole (1,2), Katia Rossini (1,2), Helmut Kern (2), Stefan Löfler (2), Hannah Fruhmann (2), Michael Vogelauer (3), Samantha Burggraf (2), Martina Grim-Stieger (3), Ján Cvečka (4), Dušan Hamar (4), Milan Sedliak (4), Nejc Šarabon (5), Amber Pond (6), Donatella Biral (7), Ugo Carraro (1), Sandra Zampieri (1,2)

Source: European Journal Translational Myology - Basic Applied Myology 2012; 23 (3): 205-210

DOI: http://dx.doi.org/10.4081/bam.2013.4.205

Keywords: aging, human skeletal muscle, lifelong physical exercise, senior sportsmen, denervation and reinnervation, fiber-type grouping, training

Abstract:

It has long been recognized that histological changes observed in aging muscle suggest that denervation contributes to muscle deterioration and that disuse accelerates the process while running activity, sustained for decades, protects against age-related loss of motor units. Here we show at the histological level that lifelong increased physical activity promotes reinnervation of muscle fibers. In muscle biopsies from 70-year old men with a lifelong history of high-level physical activity, we observed a considerable increase in fiber-type groupings (almost exclusively of the slow type) in comparison to sedentary seniors, revealing a large population of reinnervated muscle fibers in the sportsmen. Slow-type transformation by reinnervation in senior sportsmen seems to be a clinically relevant mechanism: the muscle biopsies fluctuate from those with scarce fiber-type transformation and groupings to almost fully transformed muscle, going through a process in which isolated fibers co-expressing fast and slow MHCs seems to fill the gaps. Taken together, our results suggest that, beyond the direct effects of aging on the muscle fibers, changes occurring in skeletal muscle tissue appear to be largely, although not solely, a result of sparse denervation. Our data suggest that lifelong exercise allows the body to adapt to the consequences of the age-related denervation and to preserve muscle structure and function by saving otherwise lost muscle fibers through recruitment to different, mainly slow, motor units. These beneficial effects on motoneurons and, subsequently on muscle fibers, serve to maintain size, structure and function of muscle fibers, delaying the functional decline and loss of independence that are commonly seen in late aging. Trial Registration: ClinicalTrials.gov: NCT01679977

Affiliations:

1 Laboratory of Translation Myology, Department of Biomedical Sciences, Padova, Italy
2 Ludwig Boltzmann Institute of Electrical Stimulation and Physical Rehabilitation, Wien, Austria
3 Department of Physical Medicine and Rehabilitation, Wilhelminenspital, Vienna, Austria
4 Faculty of Physical Education and Sport, Comenius University, Bratislava, Slovakia
5 University of Primorska, Science and Research Centre, Institute for Kinesilogical Research, Koper, Slovenia
6 Anatomy Department, Southern Illinois University School of Medicine, Carbondale, IL, United States
7 C.N.R. Institute of Neuroscience, Department of Biomedical Sciences, Padova, Italy