Is it necessary to include biarticular effects within joint torque representations of knee flexion and knee extension?
2012-05-09T07:50:51Z (GMT) by
The purpose of this study was to consider whether it is necessary for biarticular effects to be accounted for in subject-specific representations of maximal voluntary knee extension and knee flexion torques. Isovelocity and isometric knee torques were measured on a single participant at three different hip angles using a Contrex MJ dynamometer. Maximal voluntary torque was represented by a 19-parameter two-joint function of knee and hip joint angles and angular velocities with the parameters determined by minimising a weighted root mean square difference between measured torques and the two-joint function. The weighted root mean square difference between the two-joint function and the measured knee flexion torques was 14 Nm or 9% of maximum torque, whilst for knee extension the difference was 26 Nm or 9% of maximum torque. The two-joint representation was shown to be more accurate than an existing single-joint representation for torques measured at hip angles other than those used to derive the single-joint function parameter values. The differences between the traditionally used single-joint representation and the measured knee flexion and knee extension torques were largest for the most extended hip joint angle (15% and 18% of maximum torque respectively) while the corresponding differences for the two-joint function were 9% and 8% of maximum torque. It is concluded that a two-joint function can account for changes in knee flexion and knee extension joint torques due to both monoarticular and biarticular muscles over a range of both hip and knee angles, and this has the potential to improve the biofidelity of whole body subject-specific torque-driven simulation models.