Posture versus power: how does this patient move?

The authors believe to best answer questions brought to one by referring physicians, one needs to understand how ones´ patients call upon their neural, muscular, and skeletal systems to walk across the room. Two theories are prominent in explaining the presence of anterior ground reaction forces (GRFs) needed to accelerate the body center-of-mass (COM) in the direction of progression. The first involves the posture of the body, i.e., the position of the COM forward of its base of support. The authors test this “falling COM model” by computer simulations of an inverted pendulum and find partial explanation for anterior GRFs. The second theory involves the use of mechanical power at the lower extremity joints to perform work on the body and cause changes in its mechanical energy. The authors demonstrate that these two theories complement each other, and both can be used to interpret movement strategies in pathological gait