Figure 1: Schematic diagram of the lower body positive pressure (LBPP) treadmill chamber. A buoyant force (F1) equal to the pressure differential (ΔP) between the pressure inside the chamber (P1) and outside the chamber (P2) multiplied by the cross-sectional area of the body and the flexible waist seal (Axy) counteracts the downward gravitational force (Mg), thus decreasing the net vertical ground reaction force (GRF). During ambulation, an inertial force (Maz,CM) equal to the mass of the individual multiplied by the body’s acceleration also contributes to net GRF.