Determinants of Skeletal Muscle Hypertrophy and the Attenuated Hypertrophic Response at Old Age
- *Corresponding Author:
- Dr. Hans Degens
Institute for Biomedical Research into Human Movement and Health
Manchester Metropolitan University, John Dalton Building
Chester Street, Manchester M1 5GD, United Kingdom
E-mail: [email protected]
Received Date: January 16, 2012; Accepted Date: February 23, 2012; Published Date: February 27, 2012
Citation: Degens H (2012) Determinants of Skeletal Muscle Hypertrophy and the Attenuated Hypertrophic Response at Old Age. J Sport Medic Doping Studie S1:003. doi:10.4172/2161-0673.S1-003
Copyright: © 2012 Degens H. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
In 2012 we will again see the impressive achievements of many athletes during the London Olympic Games. In particular for weightlifters success is dependent on the power- and force-generating capacity of their muscles, which in turn are strongly determined by muscle mass. Many athletes and bodybuilders therefore train intensively to develop as much muscle hypertrophy as possible. Unlimited hypertrophy, however, is impossible. Limitations may be imposed by the peak forces that the tendons, bones and joints can cope with, but also by factors within the muscles themselves. For instance, an increase in pennation angle, which accompanies hypertrophy, beyond 45 0 would result in a reduction in muscle strength even if muscle mass continuous to increase. There also is a trade-off between metabolism and diffusion, where highly oxidative fibers require shorter diffusion distances, and hence smaller fibers, for adequate oxygen supply to the mitochondria, than glycolytic fibers. A similar situation applies to the myonuclei where transcripts are distributed over the cell mainly by diffusion and unbridled hypertrophy would, at least in theory, cause serious problems with fiber maintenance. Despite these limiting factors muscles in bodybuilders can be as much as 74% larger than in the normal population. Elderly people have a lower muscle mass that may cause problems with daily life activities and an increase in muscle strength would improve their quality of life. There are indications, however, that the maximal attainable hypertrophy is significantly reduced in the elderly. Here it is suggested that while individual fibers in the elderly may hypertrophy to a similar extent as their younger counterparts, the age-related loss of muscle fibers is an additional limiting factor of the whole muscle hypertrophy at old age.