Predictive equation of the six-minute walk test considering the distance of the course and the level of physical activity

Abstract

Introduction: The six minute walk test (6MWT) is used worldwide for functional capacity assessment. In addition to being simple and requiring minimal technology, 6MWT has proven reproducible and well tolerated since its first use. Predictive equations consider anthropometric and clinical data, specific to each country. However, the international standardization (American Thoracic Society) still advocates performing the test in corridors of 30 meters in length, since in smaller corridors, the distances can be underestimated. In addition, little is said about the importance of the impact of non-anthropometric factors on functional capacity, for example, the level of physical activity, especially in healthy young adults. Given this, we question the possibility of including the distance of the corridor and the level of physical activity in the predictive equation of the 6MWT. Objective: To elaborate a predictive equation of the 6MWT, considering the length of the corridor and the level of physical activity as a variable of the predictive model. Methods: We included healthy individuals, who performed three 6MWT each, at distances of 10, 20 and 30 meters, according to ATS. All of them responded to International Physical Activity Questionnaire (IPAQ) and performed spirometry to assess their level of physical activity and lung function. According to the IPAQ, the subjects were categorized as sedentary, irregularly active or active. Results: Two articles were written from the data of this research. In the first, it was a cross-sectional study involving 190 healthy young adults submitted to 6MWT, assessing the degree of dyspnea on the Borg scale. The distance in the 6MWT (6MWD) was positively correlated with pulmonary function parameters (p ≤ 0.002 for all parameters). There was a marginally significant correlation between the 6MWD and the difference between the scores evaluated before and after the test by the Borg scale. There was a trend for significant differences in the 6MWD according to the IPAQ categories. In addition, forced vital capacity (FVC) was the only parameter of pulmonary function with significant differences between IPAQ categories (p = 0.02). In the second study, 215 individuals were evaluated, with mean 34.1 years and body mass index (BMI) of 24 kg/m2. The mean distances of 10, 20 and 30 m in 6MWT were 590, 652 and 677 meters, respectively, were observed. The variables gender, age, BMI, IPAQ, Δ heart rate, Δ Borg, and course distance were included in the prediction model of the equation (p <0.001). Conclusion: It is possible to perform 6MWT in corridors smaller than 30 meters, using corridor length and IPAQ classification as variables that predict this distance. In healthy young adults, increased lung function indicates a higher 6MWT. In these subjects, the level of physical activity based on IPAQ categories affects lung function, mainly FVC. However, the IPAQ category and degree of dyspnea are poorly related to the 6MWT of these subjects.