Effort-limited treadmill walk test: reliability and validity in subjects with postpolio syndrome.

Abstract

To determine the reliability and construct validity of an effort-limited treadmill walk test to measure functional ability in subjects with postpolio syndrome in an outpatient postpolio clinic. Functioning and distance walked on a treadmill to a Borg "hard" effort level were measured three times, a week apart, by two blinded raters in 15 subjects with postpolio syndrome, aged 37-67 yrs, with new weakness, fatigue, and pain but with no other cause of symptomatology or condition-limiting walking. One rater tested them twice. Fatigue activity level, mobility, and health-related quality of life (Medical Outcome Study Short Form Health Survey [SF-36]) defined functioning. Generalizability correlation coefficients determined intrarater, test-retest and interrater reliability. The correlations relating the distance walked and functioning determined construct validity. Reliability for generalizability correlation coefficients were: intrarater, 0.91; test-retest, 0.85; and interrater, 0.58. Interrater reliability improved to 0.91 with adherence to a standardized protocol. Validity was established with correlations between the distance walked and SF-36 physical component score (0.66), physical role (0.60), bodily pain (0.60), and vitality (0.55). The treadmill walk test provides a reproducible and valid measure of ability in persons with postpolio syndrome with a single rater, but a standardized protocol is essential for reliability.