Two-Mass Model (IMAGE) Southern Methodist University Caption The two-mass model of the human body and a corresponding pattern of running foot-ground force application. The overall force-time pattern can be accurately understood as the sum of two parts: 1) the force corresponding to the collision of the lower limb with the ground (dashed red curve); and 2) the force corresponding to the motion of the remainder of the body's mass (dashed green curve). The sum of the force curves provides the total ground force (solid blue curve). Credit Laurence J. Ryan/SMU Usage Restrictions Please credit License Licensed content Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.