Comparing treadmill and overground versions of the two-minute walk test in people with low back pain

Purpose: Individuals with Low Back Pain (LBP) often face significant disabilities, including walking limitations. We use the Two-Minute Walk Test (2MWT) to assess walking performance, comparing overground and treadmill versions for correlation and interchangeability. Material and methods: A randomised cross-over study of 40 participants with LBP randomly completed the 2MWT in a hallway and on a treadmill. The correlation was analysed by the Spearman Rho correlation coefficient (r), the agreement by the Bland-Altman method, differences between the testing orders by a paired sample t-test, and the association by a univariate regression. Results: A high correlation was found between the methods (r = 0.76, p < 0.01). The difference between the methods was 45.4 metres (95% CI 33.4: 57.4, p < 0.01) or 29%, with an insignificant 6.8 metres (95% CI −17.4: 31.0, p = 0.57) between the testing orders. Notably, the distance walked in the hallway served as a strong predictor, explaining a substantial portion of the variation observed in the distance covered on the treadmill (R² = 0.61, p < 0.01). Conclusion: Performance of the 2MWT overground and on a treadmill correlate highly in people with LBP. However, because participants walked 29% further in the hallway, treadmill walking is likely not an interchangeable alternative to testing when the aim is to evaluate performance.