Stand holding a barbell using a shoulder-width underhand (supinated) grip. Your elbows should be almost fully extended and the barbell should be resting against your thighs.
Exhale as you flex your elbows and raise the barbell straight up the front of your body, keeping it close to the contours of your torso. To keep the barbell close to your body, you will have to pull your elbows backward. Keep raising the barbell as high as you can without allowing your elbows to travel forward.
At the top of the movement, hold for a count of two and squeeze your biceps.
Reverse the movement and lower the barbell back down the front of your body to the starting position, stopping with your elbows almost fully extended.
Repeat the barbell drag curl for the prescribed number of repetitions.
Comments and tips
Just like the name implies, the barbell is kept close to the body throughout the exercise, as if being dragged up and down its surface.
In addition to elbow flexion, the barbell drag curl incorporates shoulder hyperextension (when the elbows move backward), which activates the posterior deltoid. However, the activation of the posterior deltoid is relatively small, even under heavy load, so the effect of the barbell drag curl on posterior deltoid development is minimal.
Even though the exercise incorporates both elbow flexion and shoulder hyperextension, it is still considered an isolation exercise as opposed to a compound exercise because the extent of the shoulder hyperextension is small.
The long head of the biceps brachii is activated more than the short head is because, when the elbows move backward, the long head is stretched more than the short head is, allowing the long head to make more of a contribution to the lift.
You will often see demonstrations of the barbell drag curl in which the barbell is raised much higher up the front of the body, until the forearms are vertical. In order to get the forearms vertical, the elbows must move significantly forward, which requires shoulder flexion. As such, this variation of the barbell drag curl also activates the anterior deltoids and, weakly, the upper pectoralis major (chest) and short head of the biceps brachii. The recommendation is to use both variations of the barbell drag curl, focusing on the variation described above, under Execution, when you want to emphasize the development of the biceps brachii, especially the long head.