Supination resistance is an attempt to measure the force that is needed to supinate the foot. It is used in the clinical assessment of patients and in the prescribing of foot orthotics. In foot orthotic prescribing, the “rule” is that the more force needed to supinate the foot, so the more rigid and inverted the foot orthotic should be. If that force is low, then softer and more flexible foot orthotics can be used. The supination resistance force also correlates with some pathologies in the foot.
PodChatLive had an episode on supination resistance to bring together all the key researchers on the topic (embedded above). Podiatry Arena has a lot of threads on the supination resistance and this blog post explains it in great detail.