BELIEVE IT OR NOT, CARDIO BUILDS MUSCLE

If you avoid cardio because you think it may negate or slow your muscle gains, think again: According to a new review of 14 studies, aerobic training like running, walking, and cycling not only doesn’t diminish leg muscle mass—it actually increases it. 

In several of the studies reviewed, both younger and older men who did about 45 minutes of cardio four days a week at 80% max heart rate increased leg muscle size by 5% and 6%, respectively. “Aerobic exercise, if done properly, can lead to as much muscle growth as you’d expect with resistance exercise,” says study author Matthew Harber, Ph.D. “Intensity is more important than duration, so if the goal’s growth, work up to 80% of your max heart rate.”