We read with great interest the article by Weir et al1 published in CHEST (December 2013). The authors compared the effect of the instruction “walk as fast as you can” (fast walk) with the standard instruction “walk as far as you can in 6 min” (standard walk) for the 6-min walk test (6MWT) in patients with pulmonary arterial hypertension, idiopathic pulmonary fibrosis, and other forms of interstitial lung diseases. They found that patients walked longer distances in 6 min with the fast walk compared with the standard walk. We would like to emphasize that an important component of the applicability of the 6MWT is its ability to reflect activities of daily living over other walk tests.2 In day-to-day life, patients are used to walking at their own pace and not fast. As a result, the reduction in distance of fast walk may not truly reflect an equivalent reduction in patients’ activities of daily living. In addition, for measuring functional capacity, we believe that repeatability of the test, which the authors did not study, is more important.