Habitual physical activity score as a predictor of the 6-min walk test distance in healthy adults.

Background: The 6-min walk test (6MWT) is a simple, inexpensive test of functional exercise capacity. The 6MWT distance (6MWD) in healthy adults varies geographically, emphasizing the need for population-specific reference equations. The purpose of the present study was to investigate the influences of the habitual physical activity (HPA) score and other anthropometric and demographic parameters on the variability of the 6MWD among healthy adults and to propose a reference equation.

Methods: This was a prospective, cross-sectional, observational study. The 6MWT was conducted in a 30-m hospital corridor on 201 healthy volunteers, 125 men and 76 women, aged 20-60 years. The HPA in the previous 6 months was assessed using Baecke's questionnaire. Univariate analysis followed by multiple regression analysis was performed to analyze the significance levels of different probable predictors.

Results: The 6MWD was significantly greater in more active than in less active subjects (663.8±55.4m vs. 599.9±67.8m, p<0.001). The regression analysis showed that the subject's age in years (p=0.017), gender (p=0.006), height in cm (p=0.004), weight in kg (p<0.001), total activity score (TS) (p<0.001), and absolute difference in heart rate before and after exercise (p<0.001) could explain 48.9% of the variability in the 6MWD in healthy adults.

Conclusions: The HPA score is probably the most appropriate variable to include in the reference equation predicting the 6MWD in healthy adults from the Indian subcontinent.