Biomechanical changes elicited by an anterior cruciate ligament deficiency during steady rate cycling

Objectives. To identify any changes to lower limb biomechanics during steady rate cycling as a result of an anterior cruciate ligament deficiency. Design. Comparative study in which healthy and anterior cruciate ligament injured individuals underwent biomechanical analysis during stationary cycling. Background. Individuals with an anterior cruciate ligament deficiency often exhibit reductions in the magnitude of quadriceps muscle activity and subsequent knee joint extensor moments during walking. It is not known whether these compensations are present during cycling, an exercise frequently used to retrain anterior cruciate ligament injured individuals. Methods. Ten healthy and 10 unilateral anterior cruciate ligament deficient individuals participated. All participants were required to cycle for approximately 30 s at each of six different cycling intensities while lower limb EMG, kinetics, and kinematics were collected bilaterally. Before riding, participants performed submaximal isometric contractions to generate normalizing data. Results. In addition to reduced quadriceps activation and net knee joint extensor moments, the anterior cruciate ligament deficient limbs exhibited decreases in linear impulse of the resultant pedal force, knee joint flexor moments, hip and ankle extensor moments, and muscle activity from gluteus maximus. These decreases were counteracted by an increase in output from the anterior cruciate ligament intact limb. Conclusion. Anterior cruciate ligament injured individuals exhibited a limb attenuation strategy during cycling activities.