21s
A set of 21 reps divided into three ranges of motion: bottom, top, and full.
21s are a classic intensity technique involving 7 reps in the bottom half of ROM, 7 in the top half, then 7 full range reps, totaling 21. This extended set thoroughly fatigues the muscle through all ranges while creating significant metabolic stress. Most commonly used for bicep curls but applicable to many exercises.
Where the twenty-one comes from
Seven reps in the bottom half of the range, seven in the top half, then seven full reps, for twenty-one in total without setting the weight down. Splitting the range this way means the muscle spends far longer under tension than a straight set of seven would, and the final seven full reps arrive with both halves of the range already fatigued, which is what makes them so much harder than the count suggests.
How to use them
Barbell and EZ-bar curls are the traditional home, and the technique transfers well to lateral raises, leg extensions and cable work. Use roughly 40 to 60 per cent of the weight you would use for a normal working set, because twenty-one reps of continuous tension is a different demand from seven. One or two sets at the end of an arm or shoulder session is enough; this is a finisher, not a foundation.
Common mistakes
Loading it like a straight set, which means the last seven full reps turn into a swinging mess. Letting the half-rep boundaries drift so that the bottom seven creep upward and the top seven creep down, until the set is twenty-one vague reps in the easiest third of the range. And using it as a staple: it is a high-fatigue, low-load stimulus, which makes it a poor substitute for progressive loading over time.
Examples
- Bicep curl 21s: 7 bottom half, 7 top half, 7 full
- Leg extension 21s
- Total of 21 reps per set
Compound exercises
Put this into practice with exercises from the library.