Exercises› Arms› 21s Curl

21s Curl: Correct Form & Technique

Biceps primary Barbell or EZ Bar Intermediate Isolation · Pull

The 21s curl is a classic bicep burnout protocol: 7 reps in the bottom half, 7 reps in the top half, then 7 full range reps — 21 total. The partial ranges exhaust different parts of the strength curve before finishing with full reps, creating an intense pump.

Front Back
Bicepsprimary
Forearmssecondary

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21s Curl Video Tutorial

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Video tutorial coming soon

How to Do the 21s Curl

  1. Stand holding an EZ bar or barbell with underhand grip. Start with lighter weight than your normal curls — you'll need it.
  2. FIRST 7 REPS: Curl from full extension to the halfway point (forearms parallel to floor). Only the bottom half. 7 reps.
  3. NEXT 7 REPS: Without resting, curl from the halfway point to the top (full contraction). Only the top half. 7 reps.
  4. FINAL 7 REPS: Without resting, perform 7 full range of motion curls — bottom to top. These will burn intensely.
  5. That's one set of 21s. Rest and repeat if you can.

21s Curl Mistakes to Avoid

Going too heavy — you need to complete all 21 reps. Use about 40-50% of your normal curl weight. The cumulative fatigue is brutal.
Resting between the three phases — the point is continuous tension. No breaks between the 7-7-7.
Sloppy form on the last 7 — the full-range reps at the end are the hardest. Fight to keep good form. Controlled cheat reps are OK on the final 2-3.
Doing 21s as your primary bicep exercise — they're a finisher/pump exercise. Do your heavy curls first, then 21s at the end.

21s Curl Muscles Worked

21s target the full biceps through partial and full range reps. The bottom half emphasizes the stretch/long head. The top half emphasizes the contraction/short head. The final full reps exhaust everything. It's a complete bicep protocol in one set.

21s Curl Alternatives

Barbell CurlWant standard full-range curling for strength
Cable CurlWant constant tension curling — 21s also work great on cables
Dumbbell CurlWant independent arm curling
Preacher CurlWant strict locked-position curling
↑ Harder variation
Barbell Curl
↓ Easier variation
Cable Curl

21s Curl Programming

Strength
2 × 21 (7-7-7)
sets × reps
Rest 2 min
Hypertrophy
2 × 21 (7-7-7)
sets × reps
Rest 90 sec
Endurance
3 × 21 (7-7-7)
sets × reps
Rest 60 sec

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21s Curl FAQ

Why are they called 21s?
7 bottom-half reps + 7 top-half reps + 7 full reps = 21 total reps in one continuous set.
How much weight for 21s?
40-50% of your normal curl weight. If you barbell curl 30kg, try 21s with 12-15kg. The continuous 21 reps with no rest is much harder than it sounds.
When should I do 21s?
At the END of arm day as a pump finisher. 1-2 sets after your main curling work. Not as a primary exercise.
Can I do 21s with other exercises?
Absolutely — the 21s protocol works with any exercise. Lateral raise 21s, tricep pushdown 21s, leg extension 21s. The principle (bottom half, top half, full range) applies universally.

Related Arms Exercises

Barbell Curl
Biceps · Barbell · Beginner
EZ Bar Curl
Biceps · EZ Bar · Beginner
Cable Curl
Biceps · Cable · Beginner
Dumbbell Curl
Biceps · Dumbbell · Beginner
Preacher Curl
Biceps · EZ Bar · Beginner
Hammer Curl
Biceps · Dumbbell · Beginner
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