Pedaling smoothness and electromyography patterns were quantified in children with spastic diplegic cerebral palsy (CP) and a cohort of children with typical development. Video analysis of the pedaling rhythm yielded equivalent time periods for the control group and irregular time periods in the group with CP, with greater time spent at the bottom of the pedaling cycle. Electromyography patterns of the tibialis anterior, rectus femoris, medial hamstring and lateral gastrocnemius muscle groups yielded greater percentages of muscle activity time and co-contraction time at both the ankle and knee in the group with CP; however, the control group had longer ankle co-contraction times than were expected from previous adult studies.