The brachioradialis is a stronger elbow
flexor when the radioulnar joint (forearm) is in a midposition
When the forearm is pronated, the brachioradialis is more active
during elbow flexion since the biceps
brachii is in a mechanical disadvantage.
When the forearm is pronated, the brachioradialis tends to
supinate as it flexes. In a supinated position, it tends to pronate
as it flexes.