Asymmetry in children with unilateral cerebral palsy during sit-to-stand movement: Cross-sectional, repeated-measures and comparative study.

Background: We aimed to compare motor strategies adopted by children with unilateral Cerebral Palsy and typically developing children during the performance of sit-to-stand.

Methods: Eleven children with unilateral cerebral palsy and 20 typically developing children were evaluated. Kinematic and kinetic analysis of the sit-to-stand movement was performed. Three seat heights were evaluated: neutral (90° of hip-knee-ankle flexion), elevated to 120% of the neutral height, and lowered to 80% of the neutral height. As outcome variables, we considered sit-to-stand duration (temporal); initial, final and maximal sagittal angles and range of motion of trunk, pelvis, hip, knee, and ankle (kinematics); the peak of vertical ground reaction force (kinetics), and asymmetric index. Effect size is represented by ηp.

Findings: We found that for the lowered seat, all groups presented increased flexion of lower limbs and trunk to initiate sit-to-stand (p≤0.012; ηp = 0.41-0.84), increased peak flexion of trunk, hip and knee (p≤0.01; ηp = 0.39-0.88), increased range of motion of knee and trunk (p≤0.01; ηp = 0.45-0.85) and the duration of sit-to-stand (p≤0.05 ηp = 0.23-0.56). Children with unilateral cerebral palsy presented increased posterior pelvic tilt (p≤0.01) and decreased hip flexion of both lower limbs (p≤0.01) for all seat heights and moved their non-affected limb backward in the lowered seat (p≤0.01). Asymmetry was observed for the final and the maximal angles of the ankle in neutral and lowered seats in unilateral cerebral palsy (asymmetry index = 3.3-5.8%).

Interpretation: The lowered seat height led to adaptive motor strategies in children with unilateral cerebral palsy, which should be considered in clinical practice.