written by Johnny Nguyen
As we age, we naturally undergo many physiologic changes. The 3 changes that are relevant and significant to your health and function are:
1. Decreased muscle tissue
2. Changes at the location where nerves innervate muscles
3. Reduced oxidative capacity of muscle
The good news is that exercise slows the decay and even reverses the condition of these physiologic templates that support our long-term capacity to live a healthy and physically independent life.
Let’s briefly break them down…
Decreased Muscle Size and Contractibility
Decreased muscle tissue means that we lose body shape and the structural support that muscle provides our frame. And since muscle fibers carry contractile elements, we also lose the ability to produce sufficient forces to perform normal, daily functions.
Structural and Functional Changes Where Nerves Innervate Muscles
The junction where a nerve communicates with a muscle fiber is called a motor unit. As we age, we lose many of these motor units, leaving many muscle fibers “orphaned” and without nerve innervation. The remaining nerves, therefore, must share their innervation with orphaned muscle fibers through “collateral sprouting.” The result is that motor characteristics suffer greater variability — movement becomes shaky, less precise, and weakened.
Motor-unit changes are profound because they produce exponentially greater loss of strength than mere loss of muscle mass. Structural and functional changes in the motor units are worse news for us than mere loss of muscle tissue.
Reduced Oxidative Capacity in Skeletal Muscle
The loss of muscle and muscle function greatly reduces capillary numbers, lowering nutrient and oxygen influx and waste removal, thus compromising metabolism and the regulation of energy. Among many negative effects, this reduction leads to diminishing aerobic capacity, which is strongly associated with premature morbidity and all-cause mortality.
The good news is that this can be significantly reversed with exercise. Exercise training in older people can improve aerobic capacity by up to 125%.
But I believe in exercising, regardless of age, to create a physiologic headroom. It gives us a good functional and health reserve to age with, and a safe margin in case of unexpected illness or trauma — as those with high fitness levels also enjoy the greatest survival odds against endogenous shock and illness.
Exercise is, On Average, the True Fountain of Youth
Research shows that regular exercise of adequate intensity can reduce — or reverse — some of the most important physiologic effects of aging in the neuromuscular system. The key here is in the words “sufficient intensity.”
But I also believe that, given modern life’s restriction on time and all-day activity, the types of exercise (when we workout) become more important, because only certain kinds can facilitate the physiologic and metabolic load that he change a body that otherwise encounters too much sedentary time.