The relationship between the physical cost index and knee extensor strength in children with hemiplegic cerebral palsy

[Purpose] Lower extremity strength is a contributing factor to energy efficiency of gait. However, this contribution has not previously been evaluated in children with hemiplegic cerebral palsy (CP). The aim of this study was to evaluate the association between energy consumption, measured by the physical cost index (PCI), and strength of lower extremity, measured by the maximum knee extensor strength (MKES), in children with hemiplegic CP. [Subjects and Methods] Subjects were 10 children (4 males and 6 females; age, 7-17 years) with hemiplegic CP, but no history of orthopedic intervention or botulinum toxin treatment over the 1 year prior to the assessment. The PCI was measured during a 6-min walk test, and MKES using hand-held dynamometry, with the highest of two measures used for analysis. [Results] A negative correlation was identified between the PCI and MKES (R-value, -0.81 (affected) and -0.83 (unaffected) lower limb). [Conclusion] Higher lower extremity strength was associated with lower fatigability during a 6-min walk test in children with hemiplegic CP, providing evidence for the inclusion of strengthening exercises for both the affected and unaffected extremities in the rehabilitation of these children.