They say there's no rest for the weary. And as this 100-rep dumbbell challenge proves, there's also no rest for guys looking to stack some extra size on their upper bodies.

A test of sheer physical fitness and mental toughness, this dumbbell circuit is brutally simple, but it'll help you build slabs of muscle on every part of your shoulders. It might not feel that tough at the start, but by rep number 60, you'll start feeling the heat—and it only gets worse from there.

Directions

Do 10 dumbbell rows, and then do 10 neutral-grip presses. Do that superset five times with minimal rest—for a total of 100 reps—and you're done. Depending on your ability, however, you may lengthen the rest period.

For a complete archive of our daily quick-hit routines, go to mensfitness.com/todaysworkout.