Six minute walk test in healthy persons with sufficient and insufficint levels of physical activity

Abstract

Six minute walk test (6MWT) is a common functional exercise capacity test in individuals with cardiopulmonary disease. Recent reference equations were derived from majority healthy subjects with sufficient physical activity (86-90%). Predicted walk distance from the equations may overestimate when used in patients with limited physical activity. Objective: To compare six minute walk distance (6MWD) between healthy persons with sufficient and insufficient levels of physical activity. Methods: Thai volunteers aged 45-65 years living in Bangkok and metropolitan area (n = 162; 77 males and 85 females) performed three standard 6MWTs. Best 6MWD of three tests was recorded. Physical activity levels were determined using one week recall physical activity questionnaire. Data analyses were based on 2 groups of sufficient and insufficient levels of physical activity. Results: 6MWD in sufficient level of physical activity group was greater than insufficient one in both males (701 ± 89 m vs. 652 ± 55 m; p = 0.005) and females (619 ± 49 m vs. 571 ± 35 m; p < 0.001). In women with insufficient physical activity, the predicted 6MWD from the equations of Hermione et al. and Bernadine et al. overestimated real 6MWD. Stepwise multiple regression analysis showed that height, energy expenditure per week, a percentage of the predicted maximal HR (%predHRmax), sex, weight and age were independent contributors of 6MWD in overall (r² = 0.58). Normal stride length, energy expenditure per week, %predHRmax, sex, weight and age were independent contributors of 6MWD in the group of sufficient physical activity (r² = 0.61). Height, %predHRmax and sex were independent contributors of 6MWD in the group of insufficient physical activity (r² = 0.54). Conclusion: Subjects with sufficient activity had significantly greater 6MWD than those with insufficiency activity. Using the published equations for females should be cautiously interpreted. Physical activity classification did not affect the prediction equations in males.