Causes

A repetitive and prolonged use of the shoulder and upper arm may fray the biceps tendons. This leads to the development of tendon inflammation or tendonitis, followed by an initial partial tear, possibly leading to a complete rupture of the tendon when executing a sudden and strenuous movement. A tendon rupture severely impairs the use of the arm. The causes leading to a biceps tendon rupture are:

Tear of the rotator cuff

Shoulder instability

Joint stiffness particularly of the elbow

Lack of, or excessive training

Inadequate warm up

Weakness of the muscles  

Tightness of the biceps