In human anatomy, the biceps brachii, or as it is commonly known, the biceps, is a two-headed muscle. The biceps lies on the upper arm between the shoulder and the elbow. Both heads arise on the scapula and join to form a single muscle belly which is attached to the upper forearm. While the biceps crosses both the shoulder and elbow joints, its main function is to flex the elbow and supinate the forearm.
The primary function of the biceps brachii is as a powerful supinator of the forearm (turns the palm upwards). This action, which is aided by the supinator muscle, requires the elbow to be at least partially flexed. If the elbow, or humeroulnar joint, is fully extended, supination is then primarily carried out by the supinator muscle.
In doing a dumbbell or barbell curl the bicep flexes as you curl the weight up to your shoulder, relaxing as you lower the weight. This exercise is one of the most common ways to strengthen the biceps, with many variations available to focus on different sections of the muscle group.
When doing weight, or resistance, training to isolate the bicep for maximum results one must hyperextend the shoulder. By stretching out the shoulder (hyperextending) it brings the power of the movement to the bicep and away from employing the shoulder as an assistant.
There are many different types and forms of exercise available for the bicep, and depending what your goal may be, whether to build mass to the muscle, to strengthen it for a specific sport (such as pitching in baseball), or to firm up the muscle for a more aesthetic look, will determine what numbers you will choose for your number of repetitions and sets each time, and how often, you exercise your biceps.
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