Symmetrical kinematics does not imply symmetrical kinetics in people with transtibial amputation using cycling model

People with amputation move asymmetrically with regard to kinematics (joint angles) and kinetics (joint forces and moments). Clinicians have traditionally sought to minimize kinematic asymmetries, assuming kinetic asymmetries would also be minimized. A cycling model evaluated locomotor asymmetries. Eight individuals with unilateral transtibial amputation pedaled with 172 mm-length crank arms on both sides (control condition) and with the crank arm length shortened to 162 mm on the amputated side (CRANK condition). Pedaling kinetics and limb kinematics were recorded. Joint kinetics, joint angles (mean and range of motion [ROM]), and pedaling asymmetries were calculated from force pedals and with a motion capture system. A one-way analysis of variance with Tukey post hoc compared kinetics and kinematics across limbs. Statistical significance was set to p </= 0.05. The CRANK condition reduced hip and knee ROM in the amputated limb compared with the control condition. There were no differences in joint kinematics between the contralateral and amputated limbs during the CRANK condition. Pedaling asymmetries did not differ and were 23.0% +/- 9.8% and 23.2% +/- 12.0% for the control and CRANK conditions, respectively. Our results suggest that minimizing kinematic asymmetries does not relate to kinetic asymmetries as clinically assumed. We propose that future research should concentrate on defining acceptable asymmetry.