Merel-Anne Brehm, Suzan Verduijn, Jurgen Bon, Nicoline Bredt, Frans Nollet
Department of Rehabilitation , Academic Medical Center, University of Amsterdam, PO 22660, 1100 DD Amsterdam, The Netherlands. E-mail: m.a.brehm@amc.uva.nl
DOI: 10.2340/16501977-2264

Objective: To compare walking dynamics and test-retest reliability for 2 frequently applied walk tests in polio survivors: the 6-minute walk test (6MWT) to walk as far as possible; and the 6-minute walking energy cost test (WECT) at comfortable speed.
Design: Observational study.
Participants: Thirty-three polio survivors, able to walk ≥ 150 m.
Methods: On the same day participants performed a 6MWT and a WECT, which were repeated 1–3 weeks later. For each test, distance walked, heart rate and reduction in speed were assessed.
Results: The mean distance walked and mean heart rate were significantly higher in the 6MWT (441 m (standard deviation) (SD 79. 7); 118 bpm (SD 19. 2)) compared with the WECT (366 m (SD 67. 3); 103 bpm (SD 14. 3)); p < 0. 001. Furthermore, during the 6MWT, patients continuously slowed down (–6%), while during the WECT speed dropped only slightly during the first 2 min, by –1. 8% in total. Test-retest reliability of both tests was excellent (intraclass correlation coefficient (ICC) ≥ 0. 95; lower bound 95% confidence interval (95% CI) ≥ 0. 87). The smallest detectable change for the walked distance was 42 m (9. 7% change from the mean) and 50 m (13. 7%) on the 6MWT and WECT, respectively.
Conclusion: Both the 6MWT and the WECT are reliable to assess walking capacity in polio survivors, with slightly superior sensitivity to detect change for the 6MWT. Differences in walking dynamics confirm that the tests cannot be used interchangeably. The 6MWT is recommended for measuring maximal walking capacity and the WECT for measuring submaximal walking capacity.

Field walk tests, such as the 6-minute walk test (6MWT) and the 6-minute walking energy cost test (WECT) are often used to evaluate changes in walking capacity. We studied differences in walking dynamics and test-retest reliability between the 6MWT and the WECT in 33 polio survivors. For each test, the walked distance, heart rate and speed decline were measured. It appeared that the 6MWT and the WECT showed excellent reliability, with slightly better sensitivity to detect change for the 6MWT. Furthermore, we found a 15% higher heart rate at the expense of a 6% decline in walking speed at this heart rate during the 6MWT compared to the WECT. This difference in walking dynamics indicates that the 6MWT and the WECT cannot be used interchangeable.