21's Bicep Curls Workout (Proper Form & Benefits)

To do dumbbell 21s bicep curls:

1. Stand shoulder-width apart while holding two dumbbells by the sides of your thighs with your palms facing up.
2. Contract your biceps to curl upwards halfway until your hands align with your elbows. When you do this exercise, engage your core and keep your back straight.
3. Take a brief pause of two to three seconds before resuming back to the initial position.
4. Repeat this half curl until you complete seven reps.
5. Curl the weight upwards to your biceps near the shoulder level from where your hands are in line with your elbows.
6. Pause while squeezing your biceps at the movement's top and return to the starting position. Repeat until you complete seven reps.
7. Return the dumbbells to the sides of your thighs and raise them until your hands are near your shoulders.
8. Pause while squeezing your biceps at the movement's top before returning to the starting position.
9. Repeat until you complete the last seven reps.

“Don’t recruit the shoulders or torso to swing the weights up when doing the dumbbell curl. This can feel like a swinging, twisting, or heaving movement. Do not allow your hips to hinge or your lower body to assist the movement in any way.”

- Paul Rogers, Personal Trainer

The variations of 21s bicep curls are the 21s concentration curls, 21s hammer curls, reverse straight bicep 21s, 21s preacher biceps, and 21s standing biceps cable curls. These are effective ways to build overall arm strength and increase bicep size.

1. Concentration Curls 21s

To perform the concentration curls 21s: 

1. Sit on the edge of a bench with your feet flat on the ground.
2. Grab a dumbbell between your legs with one hand using an underhand grip.
3. Lean forward, then position your active upper arm against your thigh.
4. Raise the dumbbell until your elbow reaches a 90-degree angle.
5. Lower the weight back down to the starting position.
6. Repeat this motion until you complete seven reps.
7. Maintain the 90-degree angle at the elbow position once you complete the seventh curl.
8. From this position, curl the weight upward, bringing the dumbbell to a point approximately one to two inches away from your shoulder.
9. Lower the weight back to the 90-degree elbow position and repeat for seven reps.
10. Return your arms to full extension.
11. Perform seven reps of full-range motion curls, curling the weight to full contraction approximately one to two inches from your shoulder.

2. Hammer Curl 21s

To perform the hammer curl 21s, follow similar steps as the 21s standard biceps curl, except for the grip. Instead, use a neutral grip.

You have the flexibility to do the hammer curl 21s with dumbbells, resistance bands, or a cable machine.

The benefits of biceps 21s are increased hypertrophy, improved strength, prevented plateaus, enhanced muscle and mind connection, and promoted physical appearance.

Increase Hypertrophy

Research findings have consistently shown that generating muscle tension through a partial range of motion exercises can effectively stimulate muscle hypertrophy [1].

Integrating 21s bicep curls into your workout regimen can help you increase muscle mass in your biceps brachii, composed of brachioradialis (responsible for supination, pronation, and forearm flexion), and brachialis (which produces the majority of force during elbow flexion), by prolonging the Time Under Tension (TUT) and inducing a more significant metabolic stress response [2].

Related: Best Hypertrophy Program

Enhanced Strength

Incorporating biceps 21s into your training regimen contributes to developing stronger biceps muscle and overall upper and lower arms, improved grip strength, and enhanced upper body strength.

• Using momentum - Refrain from swinging your arms and relying on momentum to move the weights when performing this bicep workout. Maintaining constant tension on your muscles throughout the entire range of motion is essential to fully reap the benefits and achieve the intended purpose of the exercise.
• Using heavy weights - Building upon the previous point, it is advisable to select light to moderate weights for this bicep exercise. If you opt for excessively heavy weights, you may find yourself resorting to swinging the weights rather than engaging the targeted muscles.
• Rushing the last reps - It is important to resist the temptation of rushing through the last seven reps of the exercise, especially when you begin to feel a significant burning sensation in your bicep muscle. It is crucial to lift and lower the weight in a slow and controlled manner to maximize muscle tension and metabolic stress.
• Rounding the back - As fatigue sets in during the last reps, be cautious of rounding your back. Stay aware of your spine's alignment as you transition between reps. Opting for lighter weight and ensuring the proper engagement of your back muscles will help you challenge your biceps safely and effectively.
• Not changing equipment or weights - It is crucial to keep challenging your muscles to prevent your body from adapting to the same training stimuli. There are various ways to achieve this, such as altering the equipment used, changing sets and reps, incorporating different training methods, experimenting with grip variations, and even changing up your body positioning and angle.