Jump Performance and its Relationship with Lower Body Joint Kinetics and Kinematics in Children with Cerebral Palsy.

PURPOSE: The aim was to quantify jump performance in children with cerebral palsy (CP) and determine if the expected deficit is related to their lower-body-joint kinetics and kinematics.

METHODS: Twenty-four ambulatory (n = 17 level I and 7 level II in the Gross Motor Function Classification System) children with spastic CP (n = 13 unilateral and 11 bilateral) and 24 age-, sex-, and race-matched typically developing controls were studied. Jump height and peak power and range of motion at the hip, knee, and ankle of the more affected limb in children with CP and the nondominant limb in controls were assessed during a countermovement jump using three-dimensional motion capture and a force platform.

RESULTS: Compared to controls, children with CP had lower jump height (33%, Cohen's d (d) = 1.217), peak power at the knee (39%, d = 1.013) and ankle (46%, d = 1.687), and range of motion at the hip (32%, d = 1.180), knee (39%, d = 2.067), and ankle (46%, d = 3.195; all p < 0.001). Jump height was positively related to hip, knee, and ankle power and range of motion in children with CP (rs range = 0.474-0.613, p < 0.05), and hip and ankle power and knee and ankle range of motion in controls (rs range = 0.458-0.630, p < 0.05). The group difference in jump height was no longer detected when ankle joint power, ankle range of motion, or knee range of motion was statistically controlled (p > 0.15).

CONCLUSIONS: Jump performance is compromised in children with CP and is associated with low power generation and range of motion in the lower limb, especially at the ankle.