Effects of Small and Normalized Q-Factor Changes and Knee Alignment on Knee Biomechanics during Stationary Cycling

TL;DR

This study shows that increasing the inter-pedal distance in cycling significantly affects knee biomechanics, with larger increases causing bigger changes in knee abduction moments.

Contribution

The study investigates small and normalized changes in Q-Factor and their effects on knee biomechanics, which has not been previously explored.

Findings

Knee abduction moments increased by over 30% with the largest Q-Factor increase.

Medial pedal reaction forces increased by at least 20% with larger Q-Factor settings.

Static knee alignment showed varying correlations with biomechanical changes.

Abstract

Increasing inter-pedal distance (Q-Factor: QF) in cycling increases peak internal knee abduction moments (KAbM). The effect of smaller and normalized changes in QF has not been investigated. The purposes of this study were to examine changes in KAbM with small and normalized increases and whether static knee alignment accounts for any changes in knee biomechanics in cycling. Fifteen healthy participants were included (age: 22.7 ± 2.5 years, BMI: 23.95 ± 3.21 kg/m2). Motion capture and instrumented pedals collected kinematic and pedal reaction force (PRF) data, respectively, while participants cycled at five different QFs. Each participant’s mechanical axis angle (MAA) was estimated using motion capture. Each participant’s QFs were normalized by starting at 160 mm and increasing by 2% of the participant’s leg length (L), where the five QF conditions were as follows: QF1 (160), QF2 (160 + 0.02 × L), QF3 (160 + 0.04 × L), QF4 (160 + 0.06 × L), and QF5 (160 + 0.08 × L). A linear mixed model was performed to detect differences between QF conditions. KAbM increased by more than 30% in QF5 from QF1, QF2, QF3, and QF4. Medial PRF increased by at least 20% in QF5 from QF1, QF2, and QF3. MAA had varying degrees of correlation with the variables of interest. These results suggest that KAbM is more sensitive to changes in QF at greater QF increases.

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