Joint Torques and Patellofemoral Force During Single-Leg Assisted and Unassisted Cycling

Context: Unassisted single-leg cycling should be replaced by assisted single-leg cycling, given that this last approach has potential to mimic joint kinetics and kinematics from double-leg cycling. However, there is need to test if assisting devices during pedaling effectively replicate joint forces and torque from double-leg cycling. Objectives: To compare double-leg, single-leg assisted, and unassisted cycling in terms of lower-limb kinetics and kinematics. Design: Cross-sectional crossover. Setting: Laboratory. Participants: 14 healthy nonathletes. Interventions: Two double-leg cycling trials (240 +/- 23 W) and 2 single-leg trials (120 +/- 11 W) at 90 rpm were performed for 2 min using a bicycle attached to a cycle trainer. Measurements of pedal force and joint kinematics of participants' right lower limb were performed during double-and single-leg trials. For the single-leg assisted trial, a custom-made adaptor was used to attach 10 kg of weight to the contralateral crank. Main Outcome Measures: Peak hip, knee, and ankle torques (flexors and extensors) along with knee flexion angle and peak patellofemoral compressive force. Results: Reduced peak hip-extensor torque (10%) and increased peak knee-flexor torque (157%) were observed at the single-leg assisted cycling compared with the double-leg cycling. No differences were found for peak patellofemoral compressive force or knee-flexion angle comparing double-leg with single-leg assisted cycling. However, single-leg unassisted cycling resulted in larger peak patellofemoral compressive force (28%) and lower knee-flexion angle (3%) than double-leg cycling. Conclusions: These results suggest that although single-leg assisted cycling differs for joint torques, it replicates knee loads from double-leg cycling.