What Muscles Does a Preacher Curl Exercise?

Who knows how the exercise got its name, but preacher curl benefits include toning and strengthening the biceps muscles. Whether you're using a machine or doing a barbell preacher curl, it's important to use proper form to get the best results and prevent injury.

The preacher curl is an isolation exercise that focuses on a single muscle group — the biceps brachii, commonly referred to as just the biceps. These large muscles located on the front of the upper arms are composed of two "heads." This means they have two insertion points — the short head originates at the coracoid process of the scapula and the long head originates at the supraglenoid tubercle of the scapula, according to the University of Arkansas for Medical Sciences.

Outside of anatomy class, the biceps are known as the classic flexing muscles, and having big biceps has become synonymous with being strong and tough. But the biceps serve a purpose even for those who don't aspire to be bodybuilders or bodyguards. Responsible for flexing the arm at the elbow and maintaining tension against resistance when the arm is in a flexed position, they are the muscles that enable you to lift a heavy bag of groceries or a bucket of water.

They also assist in other exercises, such as pull-ups, chin-ups and rows. Increasing your biceps strength with preacher curls benefits your performance in these other moves.

There is no doubt that preacher curls are an effective exercise. However, according to researchers from the American Council on Exercise, there is something better. In a small 2014 study, they examined muscle activity during eight popular biceps exercises, including the cable curl, barbell curl, concentration curl, chin-up, EZ curl (both wide and narrow grip), incline curl and preacher curl.

After analyzing data from electrodes attached to the muscles during the exercise, they found that the concentration curl elicited significantly higher muscle activity than the other seven exercises.

​Read more:​ The Best Biceps Home Workout Without Equipment

The preacher curl isn't a difficult move, but things can go wrong without proper form. Due to the position of the upper arms on the pads, it's easy to allow the arms to hyperextend at the elbows, which, when holding a heavy weight in a barbell preacher curl, can spell trouble for the elbow. Here's what you should do instead:

1. Adjust the seat height, then sit down at the machine. If you are doing a barbell preacher curl, you will need to sit down with the weight in your hands, or have someone hand it to you after you are seated. If you are using a machine, adjust the resistance using the pin in the weight stack.
2. Lay your upper arms on the pads. Grasp the handles if you are using a machine. If you are using a bar, your hands should be about shoulders' width apart.
3. Keep some tension in the biceps and a slight bend in your elbow to avoid hyperextension.
4. Contract your core muscles and keep your spine erect.
5. Slowly curl the bar up towards your shoulders.
6. Squeeze the biceps at the top, then slowly lower the bar back down.
7. Maintain some tension in your biceps at the bottom of the move before going into your next repetition to avoid hyperextension.

The American Council on Exercise advises that strain can also be placed on the lower back if you swing your torso backwards. Be sure to keep your core contracted and your torso in a stable position throughout the move.