Physical Strain During Walking in Adults With Cerebral Palsy: A Construct Validity Study.

OBJECTIVE

To describe the physical strain of walking in adults with spastic cerebral palsy (CP) and investigate the construct (known-groups, convergent, and discriminant) validity of physical strain.

DESIGN

Cross-sectional design.

SETTING

Rehabilitation hospital.

PARTICIPANTS

A total of 94 ambulant adults (N=94) (41 men) with spastic CP.

INTERVENTIONS: Not applicable.

MAIN OUTCOME MEASURES: Peak oxygen uptake (VO2peak), physical strain (%VO2peak), 6-minute walk test (6MWT), mobility (Timed Up and Go Test), and quality of life (QoL).

RESULTS

The overall physical strain was median (interquartile range) 50% (18), mean (SD) VO2peak of 36.2 (8.6), and median (interquartile range) 6MWT distance of 553 m (144). The physical strain test was significantly different between Gross Motor Function Classification System levels I and II (P=.002) and between Gross Motor Function Classification System levels I and III (P≤.001), and distinguished acceptably between unilateral and bilateral CP subgroups (area under the curve=0.739; P<.001). The association between physical strain and 6MWT was high (r=-0.716; P< .001), the association with timed Up and Go Test was weak-to-moderate (r=0.490; P<.001), and the association with QoL was very weak and nonsignificant (r=0.157; P=.129).

CONCLUSIONS

Physical strain of walking in adults with spastic CP increased with decreasing gross motor function, and was significantly different between known-groups of adults with spastic CP. This study confirmed the hypotheses of a strong inverse association between physical strain and walking capacity. The weak-to-moderate association with functional mobility and the lack of association with QoL support divergent validity. Our results support the use of physical strain for adults with CP, inversely reflecting functional walking capacity, in clinical practice and research.