Jaw-as-Brake Foot Lift

Complete Practice

Lie supine, knees bent. Inversion of effort produces movement: assume that movement is produced by removing the right constraint, not by adding force. Lift your right foot half an inch off the floor and hold. Identify the muscle that is contracted to keep it there. Now find a muscle elsewhere — perhaps in the contralateral hip, perhaps in the jaw — that, when you release it, allows the lifted foot to rise further with no additional input from the leg. That second muscle is the active constraint. The leg was not the engine; the jaw was the brake.