The effects of fixation and contraction mode on prone isokinetic knee flexor tests

BACKGROUND: Adequate participant’s fixation affects measurement accuracy and performance of isokinetic exercise. OBJECTIVE: To examine the effects of different fixation methods and contraction mode on the kinetics and 3D kinematics of prone isokinetic knee flexor tests. METHODS: Fourteen healthy male participants performed maximal unilateral concentric and eccentric knee flexion movements with minimal (hand grips), moderate (grips, hip strap) and maximal (grips, thigh and hip strap, hip wedges, shoulder pads) fixation at 30°/s. RESULTS: Concentric and eccentric peak moments were highest at minimal and maximal fixation, whereas contractional work peaked at minimal fixation. Axis alignment was best at moderate fixation. Initial axis alignment caused an average antero-cranial shift (2.0 and 0.1 cm) as well as mean roll and yaw angle tilts of -0.1° and −6.1°. Hip motion was significantly reduced at maximal fixation. Eccentric movements demonstrated a lower mean angular velocity (26.0°/s) than concentric tests (29.4°/s). CONCLUSIONS: Depending on their purpose, prone isokinetic knee flexor tests or training sessions should be conducted with minimal (maximal force production) or moderate (axis alignment) fixation. When interpreting and comparing isokinetic results, the examined kinematic and kinetic effects of different fixation methods should be taken into account.