The 6-minute walk test: how important is the learning effect?

BACKGROUND: The 6-minute walk test is a submaximal exercise test that is widely used as an outcomes measure in clinical trials and cardiopulmonary rehabilitation. An initial learning effect with repeated administration is well documented, but it is unknown whether this learning effect persists with time.
METHODS: This study was designed to determine whether the learning effect persists after 2 months. Fifty healthy adults (mean age, 30.6 years; 48% men, 82% white) unfamiliar with the 6-minute walk test completed 3 walks at baseline (walks 1-3) and 3 walks at follow-up (walks 4-6). Height, weight, and self-reported physical activity were assessed at both points. Distances walked during the 6 walks were compared with a general linear model for repeated measures with post-hoc pairwise comparisons corrected by the Bonferroni method. A P value <.05 was considered to be significant.
RESULTS: The distance walked increased significantly between walks 1 and 3 (2046 +/- 228 ft to 2194 +/- 266 ft, P <.05). There was no difference in distance walked between walks 3 and 4, which were conducted 2 months apart. The distance walked increased significantly between walks 4 and 6 (2201 +/- 233 ft to 2285 +/- 257 ft, P <.05). The overall learning effect was inversely correlated with distance walked at walk 1, but was unrelated to age, sex, height, weight, or physical activity level.
CONCLUSION: The initial learning effect is maintained during a 2-month period. A more modest additional learning effect occurs during the follow-up walks. Both learning effects should be taken into account when using the 6-minute walk test as an outcomes measure.