The best workout ever, according to science

IT SEEMS LIKE every other week there’s a new study touting the best way to work out. And, really, how you do it depends a lot on your goal—someone looking to gain muscle mass may hit the gym differently than someone training for a triathlon. A few specific trends have emerged in recent years regarding working out for general fitness, and more specifically how to elicit the optimal metabolic response—that “afterburn” effect of continued calorie consumption for up to 48 hours after a session—e.g., the biggest bang for your effort and time. What the studies have in common: taking a circuit approach to resistance training, using heavy-but-manageable loads, alternately working multiple muscle groups, and rotating through the exercises with little or no rest in between.