Kinematic Measures Of The Knee While Cycling

Abstract

Factors contributing to knee pain in cyclists include deviations from optimal pedaling patterns and poor bike fit. Accurate measurement of kinematics is essential to obtain optimal positioning, but motion analysis equipment cost is an obstacle for many clinicians. PURPOSE: To compare the Retül 3D motion capture system to the Vicon 3D system. A lack of significant difference between devices would support a low-cost option for clinicians working with cyclists. METHODS: Cycling kinematics were captured from eleven competitive female cyclists using a 10-camera Vicon MX system and compared with a cycling-specific motion analysis system, Retül, while pedaling at 70% peak power output on a Velotron cycle ergometer. RESULTS: MANOVA demonstrated no significant difference between systems for knee range of motion (ROM) (mean difference (MD)=0.12°, p=0.96), knee extension (MD=0.12°, p=0.10), knee frontal plane knee angles (MD=2.7°, p=0.15), ankle dorsiflexion (DF) (MD=1.45°, p=0.46) and plantarflexion (PF) (MD=4.51°). However, knee flexion (MD=1.42°, p=0.02), hip flexion (MD=32.83°, p<0.001), hip ROM (MD=3.8°, p<0.001), ankle ROM (MD=3.7°, p<0.001) and measurement of the mean knee distance from bicycle centerline (MD=11.13 mm, p<0.001) were significantly different between systems. ICC indicated moderate agreement between systems for knee flexion (ICC(2,5)=0.52, p<0.001). Linear regression of difference scores on mean scores demonstrate a significant relationship for knee flexion, hip ROM and ankle DF (p=0.66, p=0.10, p=0.38, respectively). CONCLUSION: In general, these data support Retül for use in comparison with Vicon for the measurement of knee extension, ankle DF and ankle PF, which are most relevant measurements for obtaining correct fit on a bicycle. Keywords: Bike-fit, kinematics, agreement