The first reference equations for the 6-minute walk distance over a 10 m course.

RATIONALE: As primary care practice space is mostly limited to 10 m, the 6-minute walk test (6MWT) over a 10 m course is a frequently used alternative to evaluate patients' performance in COPD. Considering that course length significantly affects distance walked in 6 minutes (6MWD), this study aims to develop appropriate reference equations for the 10 m 6MWT. METHODS: 181 healthy subjects, aged 40-90 years, performed two standardised 6MWTs over a straight 10 m course in a cross-sectional study. RESULTS: Average distance achieved was 578±108 m and differed between males and females (p<0.001). Resulting sex-specific reference equations from multiple regression analysis included age, body mass index and change in heart rate, explaining 62% of the variance in 6MWD for males and 71% for females. CONCLUSIONS: The presented reference equations are the first to evaluate 6MWD over a 10 m course and expand the usefulness of the 6MWT.

Correlates of variability in endurance shuttle walk test time in patients with chronic obstructive pulmonary disease.

BACKGROUND: The endurance shuttle walk test (ESWT) is used to evaluate exercise tolerance in patients with chronic obstructive pulmonary disease (COPD). The recommended pre-intervention tolerated duration (Tlim) is between 3-8 minutes for optimal interpretation of treatment effects. However, this window may be exceeded and factors determining ESWT Tlim are not completely understood. Therefore, we aimed to determine whether pulmonary function, physical and incremental shuttle walk test (ISWT) performance measures are associated with ESWT Tlim in COPD patients. METHODS: Assessment data from patients eligible for pulmonary rehabilitation was retrospectively analyzed. Inclusion criteria were: diagnosis of COPD and complete data availability regarding ESWT and ISWT. Patients performed an ESWT at 85% of ISWT speed and were divided into three groups (ESWT Tlim: <3 minutes, 3-8 minutes, >8 minutes). Subject characteristics, severity of complaints, pulmonary function, physical capacity and activity, exercise tolerance and quadriceps muscle strength were evaluated. RESULTS: 245 COPD patients (FEV1 38 (29-52)% predicted) were included. Median ESWT Tlim was 6.0 (3.7-10.3) minutes, 41 (17%) patients walked <3 minutes and 80 (33%) patients walked >8 minutes. Body mass index, maximal oxygen consumption, Tlim on constant work rate cycle test, physical activity level, maximal ISWT speed, dyspnoea Borg score at rest and increase of leg fatigue Borg score during ISWT independently predicted Tlim in multivariate regression analysis (R2 = 0.297, p<0.001). CONCLUSION: This study reported a large variability in ESWT Tlim in COPD patients. Secondly, these results demonstrated that next to maximal ISWT speed, other ISWT performance measures as well as clinical measures of pulmonary function, physical capacity and physical activity were independent determinants of ESWT Tlim. Nevertheless, as these determinants only explained ~30% of the variability, future studies are needed to establish whether additional factors can be used to better adjust individual ESWT pace in order to reduce ESWT Tlim variability.

Course length of 30 metres versus 10 metres has a significant influence on six-minute walk distance in patients with COPD: an experimental crossover study.

QUESTIONS: Do patients with chronic obstructive pulmonary disease (COPD) achieve a different distance on the six minute walk test (6MWT) conducted on a 10m course versus on a 30m course? When assessing the distance on a 6MWT conducted on a 10m course, is it valid to use existing reference equations that were generated on longer courses? DESIGN: A randomised double-crossover experimental study. PARTICIPANTS: Forty-five patients with COPD in primary physiotherapy care. INTERVENTION: All patients performed a 6MWT twice over a 10m course and twice over a 30m course. The 6MWTs were performed in accordance with the American Thoracic Society guidelines. OUTCOME MEASURES: 6MWD was assessed and predicted distance was calculated based on a range of reference equations. RESULTS: The 6MWD on the 10m course was 49.5m shorter than on the 30m course, which was statistically significant (95% CI 39.4 to 59.6). By using existing reference equations for a 6MWT conducted on the 10m course, the predicted distance is highly overestimated (with a range of 30% to 33%) and the average distance as a percentage of the predicted value is 8%pred lower compared to a 6MWT conducted on the 30m course, resulting in a worse representation of a COPD patient's functional exercise capacity. CONCLUSION: This study shows that the impact of course length on the 6MWD and on the use of reference equations in patients with COPD is substantial and clinically relevant (based on the most conservative published minimum clinically important difference). Therefore, existing reference equations established for a 6MWT conducted over a 30m (or longer) course cannot be applied to predict the distance achieved on the 6MWT on a 10m course, which is frequently used in primary care physiotherapy practices for patients with COPD.