An exercise apparatus is disclosed. The exercise apparatus comprises: a three-dimensional coordinate system having an x-axis, a y-axis, and a z-axis lower limb segments a moving arm a multi-axis force sensor at least one footplate attached to said multi-axis force sensor for supporting a human foot or shoe a compact real-time ankle motion measurement device, said motion measurement device attached between the leg and foot and capable of measuring the ankle joint motion in at least one degree of freedom and a central processor, said central processor capable of calculating lower-limb joint moments in real time. The central processor calculates lower-limb joint moments with a modified inverse dynamic method, which does not involve computation of location of center of pressure.
