The impact of minor crank length adjustments on lower body cycling kinematics

This study examined the effect of minor crank length adjustments on lower body cycling kinematics and exercise tolerance. Fourteen amateur cyclists performed sub-maximal cycling trials with five different crank lengths, preferred (165.0-172.5 mm), ±5 and 10 mm. An RPE prescription method determined intensity, and three-dimensional kinematics were collected using Vicon motion capture. Statistical parametric mapping was employed to analyse lower body kinematics. Changes in crank length had no effect on the mean power output (199.1 ± 50.5 W). However, minor reductions were associated with significant decreases in knee (0-24%; 58-100%) and hip (0-13%) flexion as well as increases in the anterior pelvic tilt (0-40%; 74-100%). Additionally, shorter cranks resulted in less pelvic obliquity and rotation, hip abduction and knee rotation. Minor reductions in crank length can decrease hip and knee flexion, can limit non-sagittal plane motion and could serve as an effective bike manipulation to reduce the risk of overuse injury. Shorter cranks also enable riders to achieve anterior pelvic tilt and could limit stress on the lumbar spine. As minor adjustments did not impact power output, crank length alterations should be considered during bike fits and by bike manufacturers.