Associations of inter-segmental coordination and treadmill walking economy in youth with cerebral palsy.
This study investigated associations of thigh-shank coordination deficit severity and metabolic demands of walking in youth with cerebral palsy (CP) and their typically developing (TD) peers. Youth (ages 8-18 years) with hemiplegic and diplegic CP [Gross Motor Classification System (GMFCS) I-III] and their age (within 12 months) and sex-matched peers performed a modified six-minute-walk-test on a treadmill. Kinematics (Motion Analysis, USA, 240 Hz) and mass-specific gross metabolic rate (GMR; COSMED, Italy) were analyzed for minute two of treadmill walking. Thigh-shank coordination was determined using continuous relative phase (CRP) analysis. GMR was normalized using participant specific Froude numbers (i.e. GMREq). Maximum and minimum CRP deficit angles (CRPMax,CRPMin) were analysed in SPSS (IBM, USA) using paired samples t-tests with Bonferroni correction (p = 0.0125). Associations of knee extension angle deficit (KEDMax) and coordination outcomes with GMREq (log) were assessed using multiple linear regression. Twenty-eight matched pairs were included, demonstrating significantly larger CRPMax for youth with CP [GMFCS I mean pair difference (98.75%CI) 8.2 (-0.1,16.5), P = 0.013; GMFCS II/III 26.1 (2.3,50.0), P = 0.008]. Joint kinematics and coordination outcomes were significantly associated with GMREq (P < 0.001), primarily due to CRPMax (P < 0.001), leading to a 1.7 (95%CI; 1.1, 2.4)% increase in GMREq for every degree increase in CRPMax. These findings indicate an association of thigh-shank coordination deficit severity and increasing metabolic demands of walking in youth with CP. CRP may be a clinically useful predictor of metabolic demands of walking in CP. Future work will evaluate the sensitivity of CRP to coordination and walking economy changes with surgical and non-surgical management.