The fifth fundamental Biomechanical principle included in this model is the Angular Impulse-Momentum Principle. This principle states that an increase in angular velocity of a body segment is caused by an increase in the joint torque (i.e., the turning effect caused by a muscle force), and/or an increase in the application time of the joint torque (i.e., the amount of time the joint torque is applied at the joint) and/or a decrease in the body component’s angular inertia (i.e., the resistance of the body component being moved to the angular motion).
The equation for the Angular Impulse – Momentum Principle is given here
Click on "read more" to view my description of the application of the Angular Impulse-Momentum Principle to real-world running.