Standing up, with your back toward a fixed support of approximately shoulder-height, with the elbow extended and the arm internally rotated (the thumb pointing inward), rest the back of the hand on the support and lower the trunk until you can feel the stretch around the biceps.
Again, it is not enough to simply extend the elbow in order to stretch the biceps, you also have to move the shoulder to separate its points of insertion. This exercise, if performed slowly, manages a good stretch of the biceps. In fact, from among the exercises designed to stretch the biceps individually (without assistance) this is one of the most effective. Due to the position of the arm and the movement that we perform, the anterior portion of the shoulder is also stretched.