ZULTA
NL Join the waitlist

Biceps

21s

The 21s is a strength exercise with a barbell for your biceps. Share of the load in the Zulta muscle model: biceps (short head) 30%, biceps (long head) 28% and brachialis 17%.

Also known as: barbell 21s

Level: IntermediateEquipment: BarbellSingle-joint (isolation)

How to do it

  1. Stand tall holding a barbell with palms facing forward, hands shoulder-width, arms straight.
  2. Do 7 half reps from the bottom, curling only until the forearms are parallel to the floor.
  3. Without resting, do 7 half reps from that parallel point up to the top.
  4. Finish with 7 full curls from straight arms to the top.
  5. Keep the elbows at your sides and lower under control on every rep.

Tips

  • Use about 60 to 70 percent of your normal curl weight: 21 reps adds up.
  • Pause briefly at the parallel point so each half stays clean.

Common mistakes

  • Swinging the hips to get through the last full reps.
  • Letting the half reps grow into full reps as fatigue sets in.

Muscles worked by the 21s

  • Biceps (short head) Primary30%
  • Biceps (long head) Primary28%
  • Brachialis Secondary17%
  • Brachioradialis Minor6%
  • Forearm flexors Minor6%
  • Spinal erectors (lower back) Stabilizer5%
  • Front delts Stabilizer3%
  • Gluteus maximus Stabilizer3%
  • Upper abs Stabilizer2%

Share per muscle in the Zulta muscle model. The model spreads the load of one rep over 40 muscles, based on EMG and biomechanics research.

Momentum or partial ranges change where tension sits, not which muscles work. Elbow flexion with a supinated grip: both biceps heads lead, brachialis assists, the forearm muscles hold the wrist.

21s alternatives

Same equipment

Different equipment

Easier

Make it harder

Make it easier

Similar exercises

Frequently asked questions

What muscles does the 21s work?

Mainly the biceps (short head) and biceps (long head). The brachialis assist.

Is the 21s good for beginners?

The 21s is rated intermediate. If you are new, learn the EZ Bar 21s first and build up from there.

What is a good alternative to the 21s?

For example the Barbell Cheat Curl, Axle Bar Curl and Cheat Curl. They train mostly the same muscles, some with different equipment.

How do you make the 21s harder?

Add weight or reps, or move on to the Barbell Cheat Curl and Cheat Curl.

Sources

  • Oliveira et al. 2009, J Sports Sci Med 8(1):24-29 (shoulder position and biceps activity)

Log your sets in Zulta

Zulta tracks your sets, weights and muscle load next to your running, riding or Hyrox training. The app opens soon.

Join the waitlist