The better your body composition – that is, more muscle and bone, and less fat – the leaner you’ll ultimately be. Muscle increases your resting metabolic rate, burning a higher amount of calories around the clock. And muscular strength is connected with lower risks of cancer and cardiovascular disease.
"When you hit your late thirties, your muscles have great maturity and muscle memory, so you can make incredible gains,” says Dwayne Johnson. And if there's one person who knows about middle-age muscle, it's him.