Muscle: Use it or lose it

Use your muscles or you’ll lose them

"The challenge, then, is to regularly involve as many slow-twitch and fast-twitch fibers as you can to let them know you care about them and want to keep them around. This, in turn, begs the question, how can you engage all of these muscle fibers? The answer is through resistance training (lifting weights). And the best way to know if you are doing enough is to push the muscles to mild exhaustion. You can do this with lighter weights (more repetitions) or heavier weights (fewer repetitions). Regardless, just keep going until the muscle tells you it can’t do any more."