21’s are most commonly used for the biceps muscles, though they can be utilized for other muscle groups as well. In this method a weight is picked that can be lifted 21 times and to fatigue or close. The weight is lifted half way through range of motion reps, then the other half of the range of motion for 7 reps, then full range of motion for 7 reps.
Example: Barbell Biceps Curl
1. The barbell is lifted from the thighs until arms are parallel to the floor for 7 reps
2. The barbell is lifted from the parallel position to the chest for 7 reps
3. The barbell is lifted from the thighs to the chest for 7 reps