Supination
In the forearm, supination is a turning movement that makes the palm face forward or upward. In the foot, it is a movement in which the inner edge of the sole lifts and weight shifts toward the outside. Although they share the same name, the joints involved and the way the movements look are different, so it helps to first distinguish whether you are talking about the arm or the foot. The opposite movement is Pronation.
What kind of movement is it?
The Korean term for supination is derived from Chinese characters meaning “to rotate outward.” Forearm supination is a movement in which the two bones rotate relative to one another to turn the palm forward or upward. Foot supination occurs below the ankle and causes the outside of the foot to press against the ground. The difference is that forearm supination is a simple rotation in one direction, while foot supination is a combined movement involving several joints.
Forearm supination
The forearm has two bones lying side by side: the Radius on the thumb side and the Ulna on the little-finger side. In the Anatomical position, with the palms facing forward, the two bones lie parallel to each other. This is the supinated position. Conversely, turning the palm backward makes the radius cross over the ulna. This is Pronation.
The main muscles that produce supination are the Supinator in the forearm and the Biceps brachii at the front of the upper arm. The biceps acts particularly strongly when the elbow is bent, helping you apply force when tightening a screw clockwise or turning a bottle cap.
With your elbow bent and held against your side, supination is the direction that turns your palm upward. This position looks like supporting a bowl on your palm. The direction the palm appears to face varies with shoulder position and elbow angle, so whether the palm faces “up” or “forward” needs to be described together with the posture to be accurate.
Everyday movements that involve supination include turning a doorknob or key, supporting a cup, tightening a screw, and placing an object on your palm. When you type on a keyboard for a long time, your forearms remain in a pronated position. Turning them toward supination may then give you a feeling of loosening up.
Foot supination
Foot supination occurs through the combined movement of the subtalar joint just below the ankle, the midfoot joints, and other joints. Its characteristic features are a lifting of the inner edge of the sole, an outward tilt of the foot, and a higher, more rigid Foot arch.
During walking or running, the foot alternates between pronation and supination. When the heel contacts the ground, contact begins on the outside and the foot rolls inward to absorb impact (pronation). When the foot pushes off the ground, it moves in the direction that makes it more rigid (supination). This ability to become either flexible or rigid according to the situation allows the foot to adapt to the ground and transmit force.
A foot with more pronounced supination may feel as though weight is concentrated on the outside, and the outside of the shoe may wear down more. These features vary depending on Ankle movement, arch height, footwear and ground surface, and walking speed, so it is difficult to draw a firm conclusion from an isolated observation. If you want to understand your usual foot posture, it is helpful to look at how you walk barefoot, how you stand, and the soles of your shoes together.
Try these movements
- Forearm rotation — Bend your elbow to 90 degrees and hold it against your side, then slowly rotate your palm to face upward and then downward. Keeping your elbow from moving away from your body lets you feel the rotation of the forearm rather than the shoulder.
- Feel the weight on your feet — Stand barefoot and feel whether your weight is distributed evenly across three points: the big-toe side, the little-toe side, and the heel.
- Ankle circles — While seated, make large circles with your ankle, alternating between tilting inward and outward to get a feel for pronation and supination.