Fig. 1.
During walking, forward progression is maintained when the extrapolated center of mass (XCoM) projects anterior to the posterior border of the base of support at toe-off, i.e. when the backward margin of stability (MoSBW) at toe off is positive. In prosthetic gait, control of MoSBW is affected by reduced push-off power of the prosthetic foot. a Depicts the prosthetic step for which no problem occurs. b Depicts the intact step. Due to the reduced push-off power of the prosthetic foot the center of mass velocity is reduced and hence XCoM projects less far anteriorly. With normal step length, the MoSBW would be reduced causing a treat for a loss of progression or a backward fall. c When the intact leg step length is reduced, MoSBW is restored but at the expense of step length asymmetry (i.e intact step is shorter compared to the prosthetic step)