• Exercise

As the co-chairs of the joint American Thoracic Society/European Thoracic Society (ATS/ERS) task force on field exercise testing we noted with interest the work by Beekman et al,1 who describe reference values for a 6-min walk test (6MWT) performed around a 10 m course. These authors have previously shown that walk distances on this track provoke a significantly shorter distance than on the course consistently recommended in guidelines in patients with COPD.2 This protocol deviation does not represent a conventional 6MWT,3 and we suggest should be renamed to avoid confusion. Importantly, it remains unclear whether other important ‘benchmark values’ such as the minimal important difference (MID) and the distance below which survival is affected can simply be transposed to the 10 m-6MW. We appreciate that space is an important constraint in many clinical settings, including primary care environments, however we believe there are robust tests of walking performance that are conducted over a course shorter than 30 m, such as the incremental shuttle walking test,4–6 and the 4 m gait.7–10 It is currently unclear what this variant adds to this existing repertoire of field based exercise tests.

While we appreciate the test is conducted within 6 min, it does not accurately reflect current guidance on standard performance of the 6MWT in terms of track length. We would encourage researchers and clinicians to conduct the 6MWT as indicated in international guidelines.3 For clarity, we would propose to label this test as 10 m-6MW or comparable alternative. In addition we want to alert readers to the fact that for this version of the test little is known about the validity, reliability, responsiveness and its place in an end-point model of outcomes.