To reach 100 reps each day, Heria completed 50 per arm. He could split the reps into as many sets as needed and spread them across the day. After each session, he rated the difficulty and fatigue.

Push-ups may seem like one of the simplest exercises: you go down, and you come up. However, that simplicity conceals a mistake that almost everyone makes—letting the hips sag. When your body loses ...