The purpose of the study was to study the utilization of range of motion at the hip, knee, and ankle joints during exercise on a bicycle ergometer. Six healthy subjects biked at different workloads, pedaling rates, saddle heights, and pedal foot positions. The subjects were filmed in the sagittal plane with a cine-film camera at 60 frames/sec. The mean hip range of motion (ROM) during normal cycling was 38 degrees ranging from 32-70 degrees hip flexion. The mean knee ROM was 66 degrees ranging from 46-112 degrees knee flexion, and the ankle ROM was 24 degrees ranging from 2 degrees plantarflexion to 22 degrees dorsiflexion. The hip, knee, and ankle joint motions were influenced by changes of the saddle height or pedal foot position. Different workloads had a small but statistically significant influence on the joint motions while different pedaling rates did not significantly change the lower limb joint motions. The range of motion utilized during cycling is approximately equal to, but more flexed compared to level walking and stair walking. The most effective way of increasing the ROM and obtaining more extension of the lower limb joints is to change the saddle height.J Orthop Sports Phys Ther 1988;9(8):273-278.