Effects of Vertical Alignment of Leg on the Knee Trajectory and Pedal Force during Pedaling

Objective: This study evaluated the vertical and horizontal forces in the frontal plane acting on a pedal due to the vertical alignment of the lower limbs. Method: Seven male subjects (age: 25.3 ± 0.8 years, height: 175.4 ± 4.7 cm, weight: 74.7 ± 14.2 kg, foot size: 262.9 ± 7.6 mm) participated in two 2-minute cycle pedaling tests, with the same load and cadence (60 revolutions per minute) across all subjects. The subject``s saddle height was determined by the height when the knee was at 25° flexion when the pedal crank was at the 6 o``clock position (knee angle method). The horizontal force acting on the pedal, vertical force acting on the pedal in the frontal plane, ratio of the two forces, and knee range of motion in the frontal plane were calculated for four pedaling phases (phase 1: 330~30°, phase 2: 30~150°, phase 3: 150~210°, phase 4: 210~330°) and the complete pedaling cycle. Results: The range of motion of the knee in the frontal plane was decreased, and the ratio of vertical force to horizontal force and overall pedal force in the complete cycle were increased after vertical alignment. Conclusion: The ratio of vertical force to horizontal force in the frontal plane may be used as an injury prevention index of the lower limb.