Keeping your muscles young

For several years now, Dr. Russell Hepple has been closely monitoring a group who, by all definitions, defy the descriptions of most people their age.

Along with his co-investigator, Dr. Tanja Taivassalo, and other colleagues at McGill and in the U.S., Hepple is studying 15 octogenarians who are avid participants in masters athlete track and field competitions.

“We’re still in the preliminary stages of understanding why these people can maintain their capacity for physical activity,” says Hepple, who is director of the McGill Research Centre for Physical Activity and Health (PATH) and principal investigator of McGill’s Muscle Aging Diagnostics Laboratory. “Genetics likely has something to do with it, and we want to understand if this explains the greater protection in terms of the functional units of muscle as they age. We’re hoping to better understand how they can compete at this level and, in general, continue to have such impressive physical capabilities at an age better known for physical frailty.”

The most important change the muscle experiences with aging is in the connection between the nervous system and our muscles, which is through our motor neurons. The neurons have groups of muscle fibres plugged into them. For most of our adult life any given muscle fibre goes through a repetitive cycle where at one moment, the nerves are functioning properly and the next moment the muscle fibre loses its nerve supply, which can happen when a motor neuron dies. The muscle then has to acquire a new nerve supply which usually comes from an adjacent motor neuron. This cycle is known as denervation-reinnervation and it happens throughout our lives.

The not so golden years

These cycles are considered normal but in advanced age—that is, 80 plus—people become much more susceptible to problems associated with muscle deterioration such as increased frequency of falls, impaired mobility and increased physical frailty. The current evidence seems to suggest that as the body ages, there’s a deterioration of the capacity for muscle reinnervation.

“Although we don’t yet know if people who maintain a high level of physical activity throughout their lives also experience a different frequency of denervation and reinnervation cycles, we do think they have an enhanced capacity for reinnervation,” says Hepple.

Some unexpected findings

Hepple points out though that increased physical activity doesn’t necessarily mean stronger muscles. In 2009, he and his associates published some surprising results from an animal study in which older rats underwent a seven-month training program which initially showed benefits in terms of recovering muscle and improving aerobic function. But a couple of months into the study, the active group of rats began to exhibit more muscle atrophy than the sedentary group of rats, something that may have been due to an accelerated denervation component. Hepple points out, however, that despite what happened in the muscle, the rats were healthier overall, with lower body fat, better heart function and longer average lifespan than their sedentary counterparts. Overall, the good outweighed the bad.

Gaining a better understanding of the cycles of denervation and reinnervation will be key to developing therapeutic approaches to better preserve muscle for as much of the lifespan as possible, and improve quality of life in the process.

“Either figuring out how to slow down the denervation, or finding ways to better preserve the reinnervation may prove beneficial in time,” says Hepple. “We’re not quite there yet, but I hope that within five years, we’ll have some of the answers.”

The key to long-term success: tips from the masters athletes

Hepple says the masters athletes he has met have something in common.

“They all talk about the necessity to monitor their bodies on a moment-to-moment basis,” he says. “If they have a tight calf one day, they don’t run. The next day it might be their knee. They modify the type of activity they engage in all the time to avoid injuries. These octogenarians are the ones to listen to because they have been physically active for such a long time. They really know when to listen to their body.”

Working with a personalized trainer is a good idea if you have both the time and the money, but if that’s not in the cards, you can still put together an exercise routine that is sure to bring lasting benefits:

  • As much as possible, create a mix of physical activity that comprises weight-bearing activities, cardiovascular fitness, and balance and flexibility training.
  • Listen to your body. For example, if you have joint problems, then modify your activities accordingly.
  • If you want to increase the intensity of your workout, build it up slowly over time to minimize the chance of injury.
  • Above all, get active and stay active.

 

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