Aging and the Effect On Muscle Use

Mary has a hard time getting out of bed in the morning. Now almost 53 years old, it takes about a half-hour for her to stand without muscle pain in her legs. She sits up in bed and does some stretches, and gradually her muscles settle down so she can stand without fear of falling. This does nothing to help her back pain. She has a degenerative disc condition that—by her accounts—the doctors have told her she just needs to live with. Some days are good, others not so good. She feels depressed at times because she can no longer enjoy many of the things that gave her pleasure, especially going for long walks with her husband and dog.

Jim also has a hard time getting out of bed. His legs are sore and he has to pause a moment before he stands up in the morning. Once he gets moving he is fine. it just takes him longer on days after a long run. Jim is 92 and preparing for his 10th marathon.  is soreness is due to a training run he did the day before…a run of 20 miles.

How can it be that two people have such different experiences when it comes to physical function? When one looks at the research on motor function and aging there are very few summary statements that can be made. Depending on the study reviewed, the findings vary tremendously. Some studies report no change in function of the neural sub-systems controlling posture and locomotion with age while others show a severe decline.  Some studies exclude subjects with any kind of pathology, while others do not. Not surprisingly, studies that do not include people with pathology (such as neurologic or cardiovascular) found no significant difference between the younger and older adult groups.

But just what causes aging in the first place? One set of theories on aging says an important contributing factor is DNA damage. The cells of our bodies undergo 800 DNA lesions per hour, or 19,200 per cell day! Most of the lesions are repaired, but there are inevitably some errors. Nonreplicating cells in the brain, muscle and liver accumulate the most damage. The main source of DNA damage leading to normal aging is reactive oxygen from normal metabolism. As such, this is something that can be affected by diet and exercise. But there is good news; research indicates genetic factors contribute about 20% to longevity, while health-related behaviors—including lifestyle, diet and levels of exercise, stress and a person’s perception of his or her ability to succeed—contribute 80%!  This may be why studies that look at the effect of exercise on overall health often find positive benefits.