No body part gets worked as much as the shoulders. To some degree, they’re involved in chest, back, and even triceps training—and that’s before you’ve done a single dedicated movement for deltoids. Because the delicate ball-and-socket joints of the shoulder can be injured so easily and in so many different ways, extended high-volume, heavy training can take its toll even when you’re careful. That’s why an intermediate-level workout needs to balance the total number of sets with adequate…