I Want to gain muscle?
Muscle is harder to build and maintain as we age. In fact, most of us start losing muscle around age 30, with a 3- to 8-percent reduction in lean muscle mass every decade thereafter.
This is due to lower testosterone levels in men and lower estrogen levels in women — both hormones that help build muscle — as well as changes in nerve and blood cells and the body not converting amino acids to muscle tissue as efficiently, among other factors. But muscle loss doesn't have to be inevitable: For adult men and women, regular resistance training exercises are key to building and keeping muscle.