Lever & Moment
Short definition
A rigid segment (lever) and the rotating moment about its joint axis.
Full definition
A lever is a rigid skeletal segment rotating about a joint axis. Moment of force = force × moment arm. The fundamental balance for every movement is: M_muscles = M_load + M_inertia + M_external. In static optimization (isometric, acceleration ≈ 0) it is: Σ (a_i · F_max_i · MA_i) = T_req. The lever concept explains why equal muscle forces yield different efforts at different angles.
Examples
The biceps' elbow moment arm is about 4–6 cm.