It’s No Big Secret

Here’s why exercise order matters: It can affect hormonal responses, says a 2016 study published in the Asian Journal Of Sports Medicine.

Researchers compared the effects of starting with large muscle groups first versus leading off with smaller bodyparts on serum insulin-like growth factor-1 (IGF-1), testosterone, and cortisol levels in 25 untrained college-aged men who did three sets of 10 reps maximum to near fatigue in their workouts. While the order didn’t impact the number of reps they could muster, and IGF-1 and testosterone increased immediately post-exercise for both protocols, doing large muscle group exercises first and then progressing to small muscle groups produced greater anabolic hormonal response compared to the reverse sequence in normal-weight men.

Of course, in muscle building, hormones matter—so it makes sense to do legs, back, chest, and shoulders before arms, calves, and abs.