Bicep curls are weight training exercises that target the biceps brachii muscle. The movement can be performed with dumbbells, a barbell, or an ergonomically designed bar known as an EZ curl bar. Alternatively, the exercise can be carried out on a bicep curl machine or using a low pulley cable. Variations of the exercise can include preacher curls, alternate dumbbell curls, and hammer curls – each movement is intended to stimulate a different area of the muscle.
The anatomical term biceps brachii originates from the Latin words biceps meaning "two heads," and brachii meaning "of the arm." Therefore the term describes a two-headed muscle of the arm, and it is this dichotomous nature of that muscle that leads to the numerous variations of bicep curls. For example, straight barbell curls will activate the lateral or long head of the biceps, while movements that require rotation of the forearm – such as alternate dumbbell curls – will activate the medial or short head of the biceps. Hammer curls, which require a neutral grip in which there is no pronation or supination of the wrist, activate both heads of the biceps as well as the brachialis, a smaller muscle that lies beneath the biceps brachii and assists in elbow flexion.
Dumbbell bicep curls can be performed either seated, standing, or supine on a weight bench. Barbell bicep curls typically are only performed standing. A seated dumbbell curl is generally a good movement for beginners, as it lessens the likelihood both of injury and of cheating by adjusting the torso or upper arms to handle more weight during the movement. Whether standing or seated, the torso should always remain perpendicular to the floor, the shoulders set, and the legs slightly flexed and shoulder-width apart. Throughout the movement care should be taken to minimize any swinging motion of the upper arm, as this usually brings other muscles into play and removes focus from the biceps.
As with any weight training exercise, the amount of weight used for bicep curls and the number of sets and repetitions can be adjusted depending on personal goals. A heavier weight with fewer repetitions should stimulate the fast-twitch muscle fibers and build bicep muscle size and strength. Higher repetitions with a lighter weight will tend to stimulate the slow-twitch muscle fibers and result in an increase in overall endurance without adding bulk to the muscle. In either case, correct form should be maintained throughout the movement to minimize risk of injury and properly focus the stress on the biceps brachii muscle.