Moment Arm In the context of strength and conditioning, a moment arm explains why an exercise feels harder or easier at certain joint angles, because it determines how much torque the muscle must produce to move or control a load. It is tightly related to concepts of lever classes and, in part, helps to determine the sticking point of an exercise. Definition: The moment arm is the perpendicular distance between a force’s line of action and the axis of rotation at a joint. In resistance training: - It determines how much torque (rotational force) is produced at a joint. - A longer moment arm = more torque required from the muscle. - A shorter moment arm = less torque required. Example: During a biceps curl, the moment arm of the external load is greatest when the forearm is around 90° of elbow flexion, which is why the lift feels hardest there. Lock this concept in with your own training. When an exercise feels harder at certain joint angles or through a specific ROM, it’s likely because the moment arm is larger and the muscle has to produce more force. Question: Have you ever tried or prescribed targeted isometric or partial ROM work at the sticking point of a lift? For example, pause squats, pause at the knee deadlifts or cleans, spoto press, etc.?