Effect of crank length on biomechanical parameters and muscle activity during standing cycling

This study investigated the effect of crank length on biomechanical parameters and muscle activity during standing cycling. Ten participants performed submaximal cycling trials on a stand-up bicycle using four crank lengths. Joint angles, moments, powers, and works of the lower limbs were calculated from motion data and pedal reaction forces. Electromyographic (EMG) data were recorded from gluteus maximus (GM), vastus medialis, rectus femoris, biceps femoris (BF), gastrocnemius medialis, soleus, and tibialis anterior, and used to obtain the integrated EMG. Statistical parametric mapping was employed to analyse the biomechanical parameters throughout the pedalling cycle. Knee and hip flexion angles and hip power increased at the initiation (0-20%) of pedalling with increasing crank length, while the BF and GM muscle activities increased during propulsion (20-40%). Additionally, increasing the crank length resulted in increased knee power absorption during upstroke phase (70-100%). Peak knee extension moment increased with decreasing crank length during propulsion, but the moment at a short crank length during propulsion was comparable to fast walking. Consequently, longer crank lengths require increased propulsion power by the lower limb muscles during standing cycling compared to shorter crank lengths. Therefore, shorter crank lengths are recommended for stand-up bicycles to avoid fatigue.