Bicep curls look easy — but this common mistake can hurt your back (2024)

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The bicep curl is one of those staple moves you see in almost every strength routine. They are a go-to exercise for toning and strengthening the arms, and because of that, it’s often assumed that everyone knows how to do them.

However, I see a lot of my clients making minor mistakes that make the exercise less effective or even potentially harmful. When performed incorrectly, bicep curls pull the shoulder too far forward and strain the back muscles. These mistakes can lead to back pain and injury.

Bicep curl: Muscles worked and benefits

Bicep curls, when performed correctly and consistently, increase strength in the muscles located at the front of the upper arm. This move does a great job of isolating the biceps, which ensures that you’re actually working these muscles.

Strong biceps are needed for everyday activities like picking things up and putting them down. Bicep curls cause hypertrophy, or growth in muscle size, of the bicep. So if you’re looking to make everyday activities easier while toning your arms, bicep curls can definitely help.

Building a strong bicep muscle also adds to the appearance of strength in the upper body. Strengthening the front of the arm can help create a leaner and more toned appearance, so bicep curls are a common upper-body exercise used to get people "tank top" ready.

The common mistakes people make when doing bicep curls

A lot of people tend to move too much — swinging their hips or moving their whole arm while curling. Bicep curls need to be performed slowly and steadily to obtain the maximum benefits.

It’s also common to pick too heavy of a weight, which causes your body to recruit other muscles to complete the exercise. This takes away from the biceps and ultimately decreases the efficiency of a bicep curl. For example, when the weight is too heavy it’s easier to recruit the shoulders into action, which can cause your shoulders to round forward and place strain on the back.

To correct these mistakes:

• Only move your forearms while lifting your dumbbell. Refrain from moving your whole arm.
• Keep your elbows hugged in to your body throughout the whole exercise.
• Do not rock your hips from side to side. Keep your lower body in one place while performing the bicep curl.
• Choose a weight that allows you to perform all of the repetitions in your set (usually 10-15) without compromising your form. Test out a few different sizes before choosing the right weight for you.

How to do a modified bicep curl

If you’re not entirely confident in your upper-body strength, you’re not alone. There are plenty of ways to increase your strength gradually.

For a modified bicep curl, only raise the dumbbell half way in the curl (stopping when your elbow is bent at 90 degrees) or use 1- or 2-pound weights. This will help ensure you’re not straining any muscles. If you’re feeling unbalanced, sit in a chair (preferably a stool or chair without arms) and lift slowly. For the most basic modification, don’t hold any weights — just perform the movement with your palms face up to get your body used to the motion.

Bicep curl form

Taking the time to perform bicep curls slowly, step by step, will help you develop a muscle memory so that when they pop up during a workout, you can be confident you’re performing them correctly.

1. Stand straight with your feet hip-width apart. Tighten your abs, so that you’re balanced throughout the move, and softly bend your knees.
2. Holding one dumbbell in each hand (I recommend starting with 5-pound weights), relax your arms so that they hang at the side of your body.
3. Make sure your palms are facing forward. Keep your shoulders back and down. Bend at your elbow and curl the dumbbells up toward your shoulders. Make sure to keep your elbows hugging the sides of your body.
4. Lower both weights back down slowly.
5. Exhale while lifting the weights, and inhale when you lower them down. I recommend three sets of 10 curls with your selected weight.

Bicep curl variations and exercises

If you find yourself making some of the common mistakes, these exercises will help you develop your arm strength so that you don’t need to recruit other muscles to complete a bicep curl.

Arm circles

Rotating your arms in circles is a great way to get your blood flowing and warm up your arms before trying a bicep curl. Arm circles also loosen up your shoulders, which is perfect preparation. You can either do one arm at a time or circle both arms at once. Straighten your arms out toward your sides and begin rotating in large circles forward for 10 rotations. Switch the direction and complete 10 rotations backward.

Air curls

A great way to master proper form is to perform the bicep curl motion without the weights. Release the arms down by your sides and twist your hands forward so that your palms face out in front of you. Curl the arms up so that your hands almost touch your shoulders; release the arms down by your sides. Repeat 10 times.

Boxing movements

Boxing can help you become more confident in your upper-body strength while increasing your power. Warm up with jabs, and then focus on uppercuts and hooks while engaging your biceps. You don’t need gloves or equipment. Just focus on the up and down and side to side movements while squeezing your biceps.

Single arm bicep curl

Perform the bicep curl, but with one arm at a time instead of curling both weights up together. Curl the right arm up first, then lower it down. Then curl the left arm up and lower it down. Alternate for 10 reps.

More ways to master the move:

• How to do a squat that actually work your glutes
• How to do crunches so they don't hurt your neck
• Can't do a pushup? These 4 exercises will help you get there