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

Increasing inter-pedal distance (Q-Factor; QF) in cycling increases peak internal knee abduction moments (KAbM). The effect of smaller, normalized changes in QF has not been investigated, and the effect of static knee alignment at varying QFs is unknown. Purpose: The primary purpose of this study was to see if significant changes in KAbM were detectable with normalized increases in QF that are smaller than what has previously been investigated. The secondary purpose of this study was to investigate whether static knee alignment accounts for any changes in knee biomechanics while cycling at different QFs. Methods: Fifteen healthy participants were included in this study (7 Males, 8 Females, age: 22.7±2.5 years, BMI: 23.95±3.21 kg/m2 ; Mean±STD). Motion capture and instrumented pedals were used to collect kinematic (240 Hz) and pedal reaction force (PRF, 1200 Hz) data, respectively, while cycling at five different QFs. The participant’s mechanical axis angle (MAA) was determined using motion capture. Each participant’s QFs were normalized by starting at 160 mm and increasing by 2% of the participant’s trochanteric leg length (L) where the five QF conditions were (in mm): Q1 (160), Q2 (160 + 0.02*L), Q3 (160 + 0.04*L), Q4 (160 + 0.06*L), and Q5 (160 + 0.08*L). A mixed model analysis of variance was performed to detect differences between QF conditions (α = 0.05). Correlation was calculated between MAA and select variables. Results: KAbM was increased by at least 30% in Q5 from Q1, Q2, Q3, and Q4. Medial PRF was increased by at least 20% in Q5 from Q1, Q2, and Q3. There were no significant changes seen in peak vertical PRF, sagittal-plane moments and angles, or peak abduction angle that were concurrent with significant changes in KAbM. MAA had varying degrees of correlation with the variables of interest. Conclusions: These results suggest that KAbM is more sensitive to changes in QF at greater QF increases. The effect of MAA on frontal-plane knee biomechanics requires further investigation.