Why it works: Performing this move on an exercise ball forces your entire body to stabilize, which makes it a great core and arm move. Plus, on the ball, you can’t use your shoulders or back to help you move the weights, so you’ll really focus the work on the triceps, Gillespie says. (Don't have access to a ball? You can sub in a bench.)
How to do it: Lie with your upper back on an exercise ball, feet on floor and hips raised in a bridge position. Hold one dumbbell with both hands above chest, arms straight. Bending just at the elbows, slowly lower the weight toward head until forearms are parallel to floor. Pause, then return to start. Do three sets of 12 to 15 reps.
Bonus Move: Coach Durkin has his athletes superset this move with pull-overs (similar to skull crushers but you rotate your elbows back toward your ears for a start position, versus hinging at the elbow) and close-grip bench press. Do a few of each all in a row and you’ll feel it the next day.