The American Thoracic Society guidelines (ATS 2002) state that the walking course for the 6MWT must be 30 m in a straight line. Normative values have been established for this distance and other distances, mainly exceeding 30 m. An overview of published reference equations for

the 6MWT on various course lengths is shown in Table 1. In physiotherapy practices in a primary care setting, a 30 m straight TGF-beta inhibitor or circular course is often not available, while continuous (oval) courses increase the distance achieved (Sciurba et al 2003). Space limitations frequently force clinicians and researchers to administer the 6MWT on a 10 m course. Being aware of the space limitation, a COPD guideline for physiotherapists advocates performance of the standardised 6MWT on a course of at least 10 m (Gosselink et al 2008). Studies on whether course length impacts the performance of patients with COPD are inconclusive. In a crosss-ectional study, Sciurba and colleagues (2003) compared 6MWDs of different subjects in different centres and reported that course lengths ranging from 17 m to 55 m had no significant effect on walk distance of 761 patients with severe emphysema. Bortezomib However, Enright and colleagues (2003) suggested in a narrative review that the greater number of turns with a shorter

course length is one of the factors associated with achieving a shorter distance. So far, only one study has published the effects of walkway length comparing 10 m

and 30 m in healthy adults (Ng et al 2013). Similarly, only one study has examined this in patients with stroke, who are limited in their walking speed due to abnormal gait and reduced walking endurance (Ng et al 2011). Although these studies concluded that different course lengths have a significant effect on the 6MWD, the question remains whether the same effect occurs in people with COPD, who are limited in their walking speed due to dyspnoea and/or peripheral muscle fatigue. This may invalidate the use of reference equations with results from 6MWTs conducted on different course lengths than the one used to generate the reference equations. No study has Etomidate described the difference in 6MWD on 10 m versus 30 m courses in patients with COPD. Therefore, the research questions of the present study were: 1. Do patients with chronic obstructive pulmonary disease (COPD) achieve a different distance on a 6MWT conducted on a 10 m course versus on a 30 m course? A double-crossover design was used to measure the 6MWD on different course lengths. Patients were instructed to attend the rehabilitation centre twice, with seven days between the visits. This was done to correct for the learning effect that has been reported in patients with COPD (Hernandes et al 2011) and because performance usually reaches a plateau after two tests done within a week (ATS 2002).