Reverse Curl 21s Similar to classic 21s, this variation has you do 21 total repetitions. You do the first half of the range of motion for seven reps, then the middle to top half for another seven reps, and finish with seven complete reps. Doing so is excellent for maximizing time under tension and metabolic stress (3).

Reverse Straight Bicep 21s The reverse 21s bicep curl targets your forearms more than traditional bicep 21s. Begin in the same setup position as the original, but curl upwards with your palms facing down. Other than this change, the form remains the same!