Validity and Reliability of the 6-Minute Step Test in Healthy Individuals: A Cross-sectional Study

Objective:To determine the 6-minute step test's (6MST) reliability and validity and to establish reference performance values of this test.Design:Prospective observational cross-sectional study.Setting:Spirometry and Respiratory Physiotherapy Laboratory, Federal University of SAo Carlos (institutional).Participants:Ninety-one individuals [42 men and 49 women, mean age = 39 years (SD, 17 years)] without any diagnosed diseases and with normal exercise capacity [6-minute walk test (6MWT) >75% of the predicted normal].Independent Variables:Participants underwent two 6MST on 1 day and two 6MWT on another day in randomized order. Furthermore, age, gender, height, weight, lower limbs length, abdominal circumference, percentage of body fat, and fat-free mass were obtained.Main Outcome Measures:Test-retest reliability was assessed by comparing the findings of the two 6MST using the intraclass correlation coefficient (ICC) and Bland-Altman plot. Validity was assessed by comparing outcomes of the 6MST to outcomes of 6MWT using the Pearson correlation coefficient. A multiple regression analysis was conducted using the stepwise method to develop an equation to predict reference values.Results:The performance (mean steps SD) in the first and second test was 149 34 and 149 +/- 36 steps, respectively, which was correlated to distance (in meters) in 6MWT (r = 0.72; P < 0.05). Six-minute step test performance was reliable (ICC = 0.9; 95% confidence interval: 0.85-0.93). The equation to predict reference values for the first 6MST was significant (P < 0.001 and R-2 = 0.48): Performance((steps)) = 174 to 1.05 x Age((years)) to women and Performance((steps)) = 209 to 1.05 x Age((years)) to men.Conclusions:Six-minute step test is a reliable and valid test. Moreover, the number of steps may be predicted by demographic and anthropometric variables with moderate strength of prediction.