Relationship between energy cost, gait speed, vertical displacement of centre of body mass and efficiency of pendulum-like mechanism in unilateral amputee gait.

The energy cost of gait (C) is greater in amputee than in normal subjects. Our objective was to assess the influence of lower speed, inefficient pendulum mechanism and disturbed smoothness of centre of body mass (CM(b)) displacement on C in unilateral amputees and to have a better understanding the relationship between these variables. Twelve adult patients (six traumatic transfemoral and six vascular transtibial amputees) participated in the study. Lower limb kinematics, displacement of CM(b), mechanical work done by the muscles to move the CM(b) and the segments due to their movements relative to the CM(b), efficiency of the pendulum mechanism, and C were assessed simultaneously in the 12 amputees walking at their self-selected speed. Our results show that C depended on gait speed, and efficiency of pendulum-like mechanism of walking but did not depend on the smoothness of CM(b). The use of only a single variable to explain the extra cost in amputee gait could sometimes be misleading.