Reliability of functional tests of the lower limbs and core stability in children and adolescents with cerebral palsy.

Background: Muscle weakness in children and adolescents with cerebral palsy (CP) can affect daily life activities, even more if functional capabilities are poor. Also, core stability plays an important role in distal force generation.

Aim: The main purpose of this study was to investigate the reliability of functional tests of the lower limbs and the core stability in children and adolescents with bilateral spastic CP with Gross Motor Function Classification System (GMFCS) levels II and III. Secondary, associations within the functional tests and between the functional tests and gait capacity were analyzed.

Design: Cross-sectional study.

Setting: CP reference center at Ghent University Hospital, pediatric physiotherapists and schools for children and adolescents with motor impairments.

Population: Twenty-four children and adolescents with CP (11.4±2.5 yrs, GMFCS II/III:13/11) participated in this study.

Methods: Functional tests of the lower limbs (GMFCS II: sit-to-stand [STS], lateral step-up [LSU], bilateral heel rise [BHR], high jump [HJ], long jump [LJ]; GMFCS III: STS, LSU) and core stability (bridging and rolling like a ball [RLB]) were tested twice. On the second test occasion, gait capacity (1-minute walk test [1MWT] and modified timed up and go [mTUG]) were also assessed.

Results: Relative reliability of the functional tests ranged from good to excellent (Intraclass Correlation Coefficients (ICC), 0.88 - 0.96). Absolute reliability showed large variability with acceptable results for the BHR, HJ, LJ and RLB (Minimal Detectable Change % (MDC%) <40%). Strong associations were found of the RLB test and the mTUG with the BHR, HJ and LJ tests.

Conclusions: The functional tests of the lower limbs and core stability were found reliable. To measure change over time, the BHR, the HJ and LJ can be used for children and adolescents with GMFCS level II. The RLB test can be used for both GMFCS levels. Associations between the BHR, HJ and LJ tests showed strong associations with the RLB test and with the mTUG.

Clinical Rehabilitation Impact: The study highlighted the importance of developing functional tests for children and adolescents with lower motor function capacities and to integrate core stability tests in routine clinical assessments.