Effects Of Unilateral Crankarm Length Adjustments On Hip And Ankle Kinematics During Stationary Cycling

Cycling is commonly used in rehabilitation for people with joint replacement. We recently reported the knee range of motion (ROM) reductions with the unilateral shortening of crankarm length. However, the effects of unilateral crankarm adjustments on hip and ankle kinematics have not fully been explored and may provide evidence of exercise prescription for hip or ankle orthopedic conditions. PURPOSE: To examine effects of adjusting crankarm length for one limb while maintaining a constant crankarm length on the contralateral limb, on hip and ankle joint kinematics during stationary cycling. METHODS: Eleven recreationally active and healthy young adults cycled on a cycle ergometer at 7 different crankarm length conditions on the right limb: 130 - 190 mm in 10 mm increments using customized adjustable crankarms. The left crankarm length was fixed at 170 mm. The participants cycled at a work rate of 100 Watts and cadence of 80 revolutions per minute. A 13-camera motion capture system (240 Hz) collected 3 dimensional kinematic data. A 2 (limb) x 7 (crankarm length) repeated measures ANOVA was performed to detect differences in selected kinematic variables (α = 0.05). RESULTS: No interactions of limb and crankarm length were found. The ankle plantarflexion ROM, peak ankle plantarflexion velocity, hip extension ROM, and peak hip extension velocity were mostly reduced (p < 0.05) in every 10 mm reduction from 190 mm to 130 mm, except for comparisons between 130-140 mm for peak plantarflexion velocity, 140-150 mm for plantarflexion ROM, 150-160 mm for peak plantarflexion velocity, and 180-190 mm for both ankle variables. Total and average reductions between 130-170 mm were 10.1° and 2.5° for plantarflexion ROM, 69.4°/s and 17.4°/s for peak plantarflexion velocity, 9.9° and 2.5° for hip ROM, and 49.0°/s and 12.3°/s for peak hip extension velocity, respectively. The average reductions of ankle and hip ROMs were smaller than that of knee ROM (4.6°) reported elsewhere. CONCLUSIONS: These results demonstrate that unilateral reductions in crankarm length in stationary cycling can effectively reduce both ankle and hip ROMs and peak velocities. These reductions in hip and ankle ROM requirements may have implications on exercise prescription for patients with ankle and hip joint limitation due to orthopaedic or neuromuscular conditions.