Explaining Terms of Motion
Simply put, pronation and supination are components, or phases of motion and you cannot have one without the other.
To pronate or pronation, is to collapse or lengthen tissues, to stretch. This phase is also associated with a control of motion, such as a decreasing in joint angle or flexion as seen during shock absorption.
Think of jumping off a stone hedge with bent knees and absorbing the sting to the bones by softening the landing verses when you land stiff legged. Also, felt when going down the bluff on a hike, when your knees start to give aches-These are times you can appreciate the ability to pronate and control motion.
To supinate or supination, is to spring and propel forward or upward. In this phase of motion your muscles are using the stored energy obtained from the stretch of pronation to then propel forward. This phase is associated with production of motion or the explosive component of motion.
Think of how much more height you gain if you crouch down and explode up vs just jumping from a stand still. The picture of Superman taking off into a flying leap also resonates with my image of supinating—powerful.
The key to function of a muscle is to produce and control motion.
The Connection of Terms and the Transfer of Motion
When there is a limit or a change to one of the phases of motion, at the foot or above, either via the muscular system or a physical change to the structure, outside the foot or internally,* everything in the body is affected.
*This includes: muscle imbalances to deal with changes, shoe wear, the use of orthotics, or a lift, surgical interventions to bunions or hammertoes, nerve impingements and many others changes that affect the natural way in which a foot is designed for motion.
Each joint in the body depends on the muscles to transfer the kinetic energy of both pronation and supination and when you have one without the other, things get whacked out!
The individual components of one joint and all the muscles acting on it will ultimately affect the placement and the efficiency of the adjacent joints.
In other words, if one joint is wonky it will affect the whole-body motion.
A muscle functioning optimally is able to better cushion forces like a spring from the bones and passive structures and transform the forces with a spring-like recoil into supination. Without pronation, shock and efficiency is lost and it affects the whole body.
It is amazing how truly simply something can be and yet how complex it can become.