When the foot is over pronated the bones of the foot are naturally unlocked and rely on ligament and muscle strength for stability, therefore putting a greater load on the the calf muscles which will fatigue early and lead to trigger points and chronic tendinitis etc.
Foot Orthotics for cyclists can really help
In the first picture the feet and legs are aligned during pedalling. The foot does not have optimum contact with the inside of the cycling shoe.
The foot rolls inwards (pronates) the leg rotates inward causing additional ligament stretch forces at the knee which is no longer centred over the pedal.This excessive inward rotation will increase the risk of an tendon and ligament overuse injuries. The foot in an unlocked or pronated position will not deliver efficient power negatively impact performance.
Feet are supported evenly and consistently on the pedal platform. Feet, ankles, knees and hips are aligned, with the knee centred over the foot. With a customised surface between the sole of the foot and the inside of the shoe, the foot receives support and greater contact with the pedal, improving efficient power delivery.