Arm pronation is a condition that orients the palms of the hands outward away from or backward from the body. This is a natural position for some people, while other people may find this condition difficult to achieve. Many athletes, especially baseball pitchers, can benefit from some arm pronation, as it sometime aids in natural movement of the arm. Weight lifters may benefit from this orientation when performing certain exercises. In other cases, however, this orientation of the arms can cause pain or discomfort due to unnatural movement of the shoulders, elbows, or wrists.
Athletes are often more concerned than any other segment of the population about arm pronation. Baseball pitchers will need to work on proper form throughout the stride to ensure pronation occurs, since arm pronation helps protect the elbow and rotator cuff from injury. Without pronating, the pitcher may end up locking the elbow, which can lead to several painful conditions, including sprains, muscle strains, or even stress fractures. Repeated motion can increase the likelihood of injury, but pronation can help prevent injury during such repeated stresses.
Weight lifters also focus on arm pronation to prevent injury during exercises and to even improve muscle performance. The orientation of the arm will often dictate the efficiency with which an object can be lifted. More arm pronation is likely as the weight of the object being lifted is increased. This is why baseball players are more susceptible to injuries when throwing: a baseball is very light, which means less pronation is likely. A shot putter, however, usually uses a much larger object for throwing, which means more pronation will occur. Pronation of course does not prevent injury altogether, though the risk of injury is reduced significantly.
The transfer of strain in the muscles is also reduced by pronation. When an athlete throws an object, most of the muscles in the arm will undergo some sort of stress, but if the arm is properly pronated, less stress will be transferred to smaller, weaker muscles, such as the ones found in the rotator cuff or in the elbow. The load is instead transferred to longer, stronger muscles that can handle the excess force of the throw. During the course of the throw, much of the stress may actually end up in the back instead of the arm. These muscles are longer and stronger, as well as better prepared for the repeated stresses of physical activity.