Often times a salesperson will be able to tell you which running shoes you should buy based on the wear and tear of your old shoes (think pronation and supination).
The first provides stiff anti pronation, anti supination and anti torsion (which basically means your foot is kept steady and cradled within the shoe).
The wing of the bird is folded in a unique way, namely, the radius parallel with the humerus, and the whole wrist and hand with their ulnar side against the ulna; upper and forearm in a state of supination, the hand in that of strong abduction.
The muscles of the limbs are modified from those of the ordinary mammalian type in accordance with the reduced condition of the bones and the simple requirements of flexion and extension of the joints, no such actions as pronation and supination, or opposition of digits, being possible or needed.
