Instead of lifting weights this afternoon, go for a run. Or swim. Or bike. Men lose something on the order of 5% of their muscle mass each decade after the age of 35 — hence the prescription to lift, building up to heavy weights using compound exercises. (Think: deadlifts, not bicep curls. Squats, not leg extensions.) In our love of grunting in front of mirrors, we’ve lost the plot: Cardio isn’t just good for your ticker, it’s great for business, too. Plumb the effects of a few half-hour cardio sessions on the brain — as told through science and CEOs — in the Men’s Health classic “The Aristocracy of Cardio,” by Adam Campbell, one of America’s best health writers.