An exercise apparatus in this disclosure includes a doorway mountable runner restraint device. The device has a generally rigid, preferably padded, belly pad that is placed against and in front of a user's pelvis and abdominal area. A pair of cords are attached to the belly pad, each having an opposite end attached to an elastic member. Each of the elastic members is, in turn, attached to an anchor which is removably fastened to a door, a doorway frame, or sandwiched between a closed door and the doorway frame. A user fastens the apparatus in place in a doorway, faces away from the doorway, and places the belly pad against his or her torso directly over the pelvis area, and then runs in a direction away from the doorway. The elastic members resist and restrain the user from substantial movement away from the doorway but stretch to allow forward running movement.