[Within-subject variability of the 6-minute walk test]

Area of Science:

• Cardiopulmonary Exercise Testing
• Clinical Biomechanics
• Rehabilitation Medicine

Background:

• The 6-minute walk test (6MWT) is a widely utilized, cost-effective, and versatile tool for assessing exercise capacity.
• Despite its common use, the variability associated with the 6MWT necessitates careful consideration of its application.

Purpose of the Study:

• To evaluate the utility and reproducibility of performing a second 6-minute walk test (6MWT) shortly after an initial assessment.
• To determine if a repeat 6MWT provides additional valuable information or introduces unnecessary variability.

Main Methods:

• An observational, longitudinal study was conducted with healthy individuals residing in Mexico City.
• Demographic data were collected, and differences between two 6MWTs, separated by 30 minutes, were analyzed using t-tests and Bland-Altman statistics.
• Intraclass correlation coefficients (ICC) and 95% confidence intervals (95% CI) were calculated to assess reproducibility.

Main Results:

• Data from 200 tests (100 subjects) were analyzed, with a mean age of 36 ± 11 years and BMI of 24.71 ± 3.24 kg/m².
• The mean difference (bias) between the first and second 6MWT was -4 meters, with wide limits of agreement (-65.9 to 57.9 meters).
• The intraclass correlation coefficient (ICC) was 0.800 (95% CI, 0.717-0.861), indicating moderate to good reproducibility but with significant variability.

Conclusions:

• The 6-minute walk test demonstrates reproducibility but is characterized by considerable variability.
• The findings suggest that performing a single 6-minute walk test is sufficient for assessing exercise capacity.
• The variability observed in repeat testing may limit the clinical utility of a second 6MWT performed shortly after the first.