Abstract: A system of monitoring impact stress, or acceleration forces on a user while exercising is disclosed. An exercise machine is equipped with sensing apparatus that measures the downward force exerted on the supporting surface by the lower extremities of the user. In this way, the corresponding impact forces are determined as a function of the user's body weight and communicated via a display monitor as “G-forces” or “Earth Gravity Units.” This allows the user to keep exercise impact within limits desired by the user, a physical therapist, or other qualified professional.