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any muscle having three heads, or points of attachment, but especially the triceps brachii at the back of the upper arm. One head originates on the shoulder blade and two on the upper-arm bone, or humerus. Uniting part of the way down the arm, the heads swell into the belly, or muscle proper. This tapers to a tendon that rounds the elbow and attaches to the ulna, the larger of the two forearm bones. Since contraction of the triceps straightens the arm, the muscle is called an extensor. It also helps lock the elbow when the forearm pushes forward against resistance. The triceps works in coordination with a flexor muscle, the bicepsbiceps
, any muscle having two heads, or fixed ends of attachment, notably the biceps brachii at the front of the upper arm and the biceps femoris in the thigh. Originating in the shoulder area, the heads of the biceps merge partway down the arm to form a rounded mass of tissue
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 brachii of the upper arm.



a muscle that arises from three heads. The triceps muscle of the arm, situated on the posterior surface of the humerus, extends the forearm at the elbow joint. The triceps muscle of the calf is at the back of the leg below the knee; it consists of the two-headed gastrocnemius muscle and the one-headed soleus muscle, and it flexes the foot at the ankle joint.


any muscle having three heads, esp the one (triceps brachii) that extends the forearm
References in periodicals archive ?
In sheep 2, areas with moderate muscle fiber segmental necrosis were observed in masseter, semi membranosus, longissimus lumborum and triceps brachii muscles.
Saeterbakken and Fimland (11) reported greater load during 6RM for the bench press on the SS and higher EMG activation of the pectoralis major and triceps brachii muscles on the flat bench, which revealed that the increased instability on the Swiss ball did not require greater muscle activation during the exercise (but a higher total load was lifted by subjects on the SS).