Jesus Creed
To keep our muscles healthy deep into retirement, we may need to start working out more now, according to a new study of world-class octogenarian athletes. The study found substantial differences at a cellular level between the athletes’ muscles and those of less active people.
Muscular health is, of course, essential for successful aging. As young adults, we generally have scads of robust muscle mass. But that situation doesn’t last.
Muscles consist of fibers, each attached to a motor neuron in our spinal column by long, skinny nerve threads called axons. The fiber and its neuron are known as a muscle unit.
When this muscle unit is intact, the neuron sends commands to the muscle fiber to contract. The muscle fiber responds, and your leg, eyelid, pinky finger or other body part moves.
However, motor neurons die as we age, beginning as early as in our 30s, abruptly marooning the attached muscle fiber, leaving it disconnected from the nervous system. In younger people, another neuron can come to the rescue, snaking out a new axon and re-attaching the fiber to the spinal cord
But with each passing decade, we have fewer motor neurons. So some muscle fibers, bereft of their original neuron, do not get another. These fibers wither and die and we lose muscle mass, becoming more frail. This process speeds up substantially once we reach age 60 or so.
Scientists have not known whether the decline in muscular health with age is inevitable or whether it might be slowed or altered.
There have been encouraging hints that exercise changes the trajectory of muscle aging. A 2010 study of recreational runners in their 60s, for instance, found that their leg muscles contained far more intact muscle units than the muscles of sedentary people of the same age.
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