Most people can build muscle and endurance with exercise. But as Gretchen Reynolds reports in this column in the New York Times magazine, some people's bodies respond better than others, and some don't respond at all. Reynolds cites a 21 week Finnish study of 175 sedentary adults. Some of the group lifted weights, and some jogged or walked. Reynolds reports that after 21 weeks, physiological improvement ranged from a negative 8 percent (meaning they became 8 percent less fit) to a positive 42 percent. Some of the subjects improved their strength enormously, some not at all. Others became aerobically fitter but not stronger, while still others showed no improvements in either area. Only a few became both fitter and more buff.
What's up with that? Reynolds tells us that the experts think much of our bodies' response to exercise depends on genetics, some depends on diet, and some on epigenetics, "a complicated process in which the environment (including where you live and what you eat) affects how and when genes are activated." And, she says, there's a lot we don't know.
Wow, this is earth shaking! I can’t imagine a sedentary person not improving with exercise, both is strength and generally fitness. It has been my observation without a scientific study that people who exercise are more fit, so I assumed, possibly incorrectly, that if one was not fit exercise would move their bodies in that direction.
I am still skeptical, I would certainly like to see the results of another study to see if the findings are confirmed.