Variabilidad intrasujeto de la prueba de caminata de seis minutos

BACKGROUND: The 6-minute walk test assesses the ability to perform exercise and it is widely used, of low cost, and of diverse variability. OBJECTIVE: To define the usefulness of a second 6-minute walk test performed 30 minutes from the first. MATERIAL AND METHODS: An observational, longitudinal and analytical study was carried out in subjects born and inhabitants from Mexico City, both genders, without cardiopulmonary disease. Their demographic variables were recorded. Differences were calculated with the t test for independent groups and variability with the Bland-Altman statistic; its magnitude, with the intraclass correlation coefficient and 95% confidence intervals (95% CI). A p < 0.05 was considered significant. RESULTS: 200 tests from 100 subjects were studied. Average age was 36 ± 11 years. Body mass index average was 24.71 ± 3.24 kg/m2. 43 subjects were male (43%). The most frequent activity was arts and crafts in 38 (38%). Only 55 subjects (55%) increased by 24 the number of meters walked in the second test. Total of meters walked on walk 1 vs. 2 were: 437.65 ± 48.84 vs. 441.62 ± 11.49. Mean difference (bias) was of −4 (57.9, −65.9) and intraclass correlation coefficient of 0.800 (95% CI, 0.717-0.861). CONCLUSIONS: The 6-minute walk test is reproducible with wide variability. These results suggest to do only one 6-minute walk test.