The lower extremity kinematics and kinetics of stationary cycling in young children with and without cerebral palsy

Children with cerebral palsy (CP) are at risk of secondary changes, such as bone deformation. Physical activity is important to reduce these changes and to improve physical function, especially when children are young. Cycling is a great locomotor skill for this because it can be used in therapeutic and in recreational settings. Standardization of cycling protocols is needed to give therapists a better understanding how maximum improvements can be obtained. For this, we have to understand the biomechanics of cycling in young children with CP. We have investigated the kinematics and kinetics of cycling in young children with and without CP, and the influence of changes in task demands on these biomechanics. It was hypothesized that young typically developing (TD) children have altered biomechanics during cycling in comparison to older children and that young children with CP have alterations in comparison to TD peers. Furthermore, it was expected that spasticity reduction by botulinum toxin (BTX) treatment would improve these biomechanics in children with CP. In Study 1, it was shown that 4-year-olds TD children had more out-of-plane motion than 6-, 8- and 10-year olds, while motions in the sagittal plane were similar between groups. Also, 4-year-olds produced higher jerk cost when cycling at high cadences. In Study 2, analysis revealed that children with CP were only able to cycle at low resistance and low cadences and were less adaptable to changes in movement speed. Adjustments in joint angles, joint torques, jerk cost and pedal forces in all three planes of motion were observed, indicating that children with CP cycled less efficiently than TD peers. In Study 3, it was shown that CP-specific alterations in cycling biomechanics were reduced 3 weeks after BTX injections. This work has increased our understanding of the cycling ability of young children. It led to the conclusion that children with CP can cycle under reduced task demands in comparison to TD peers. When spasticity is reduced, the adaptability of children with CP against changes in task demands is increased. The findings of these studies help us understanding the influences of cycling in children with CP.