The radius and ulna are the two bones that run the length of your forearm. The ulna is located on the pinkie side. These two bones form a joint with the upper arm bone, or humerus, at the elbow, but they also form joints with one another at the elbow and wrist. Movement at these radioulnar joints causes the radius and ulna to rotate around one another. Consult with doctor to make sure this exercise is safe for you.
Pronation and Supination
If you stand with your arms hanging at your sides and your palms facing rear, your radioulnar joints will be fully pronated. To supinate from this position, you turn your forearms away from your body without rotating your upper arms. Once your palms are facing forward, your radioulnar joints is fully supinated. Muscles that cross the radioulnar joints produce pronation and supination.
Supination Muscles
The predominant muscle that performs radioulnar supination is the supinator. The biceps brachii is a two-headed muscle that also assists under specific circumstances. For example, its long head is more active when the elbow is straight, whereas its short head takes over when the elbow is bent. The biceps brachii also flexes the elbow, which is why dumbbell curls are often performed so that they end with supination.
Exercise
To perform an exercise to isolate supination of the radioulnar joint, hold a dumbbell in your left hand and sit on an exercise bench with your left forearm supported on your left thigh. Your palm should be facing down. From this position, turn your hand counterclockwise until your palm is facing up. Make sure not to move your upper arm or any other part of your body as you perform this movement. Once your palm is facing up, pause momentarily before returning to the starting position and repeating for multiple repetitions. When you're done with a set for your left arm, switch hands and exercise your right.
Alternative
If you don't have dumbbells to exercise with, you can also perform an exercise for supination of the radioulnar joint with a hammer. To do this, hold the middle section of the hammer and perform the exercise described above. This alternative allows you to slowly increase the load you work against by holding the hammer closer to its handle so that more of its weight extends past the outside portion of your hand in the starting position.
Sets and Reps
American College of Sports Medicine guidelines suggest that you perform resistance training for a specific muscle for one set of eight to 12 repetitions two times each week. It also suggests that sets should be continued until volitional fatigue, which means that you should choose a dumbbell that is heavy enough to bring you to muscle failure once eight to 12 repetitions of this exercise have been completed.
References
- "Kinesiology: Scientific Basis of Human Motion Twelfth Edition"; N. Hamilton, W. Weimar and K. Luttgens; 2008
- American College of Sports Medicine: Recommendations for Resistance Training Exercise
