One of the well-known consequences of aging is the loss of lean muscle mass. In particular, the type II muscle fibers (fast twitch) decrease the most – the ones we use for speed and quickness.
In a recent study, researchers took biopsies of the Vastus Lateralis (one of the quadriceps, or knee extensor muscles) and found that individuals in the 20-29 age group had 39 percent type I muscle fibers (slow twitch) while individuals in the 60-65 age group had 66 percent type I muscle fibers. They concluded that the fast twitch fibers decrease linearly from the third to the seventh decade.
So not only do you lose muscle mass as the years advance, but, the muscle that you have, downgrades to slow twitch muscle fibers because the muscles are not generating enough force.
Researchers report that this effect is not inevitable; it can be reversed if the training stimulus is of sufficient intensity and duration. In practical terms this means high intensity weight training – lifting heavier weights for fewer repetitions.
Fitness theorist, Art De Vany, suggests performing high-intensity exercise in the context of our evolutionary past. The idea is that our bodies and minds are product of millions of years of evolution. And since our genes haven’t changed over the last 40,000 years, our DNA is that of the hunter-gatherers.
De Vany says that exercise should mimic the activities of our ancestral past. The key is to hit the right balance of intensity and variety. He states that “you have to live in the fast twitch muscle fiber zone where your metabolic rate is many times your basal metabolism for intermittent, brief intervals. The intensity is the key to reaching the fast twitch fibers of the muscles, which are the key fibers to staying young.”