Abstract
Background: Chronic obstructive pulmonary disease (COPD) is associated with a reduced exercise capacity. Although several field tests for exercise capacity have been modified for non-standard settings, i.e. outside the hospital clinic or pulmonary rehabilitation center, their uptake remains limited. Objectives: To assess the test-retest reliability, constuct validity and responsiveness of the one-minute sit-to-stand test (1'STST) adopted in clinical practice among patients with COPD and to confirm the earlier established minimal important difference (MID) of three repetitions. Methods: Patients with COPD performed two 1'STSTs, two 6-minute walk tests (6MWT), an isometric quadriceps force (QF) measurement, a cardiopulmonary exercise test (CPET), and a seven-day physical activity (PA) measurement before and after three months of pulmonary rehabilitation (PR). An Intraclass Correlation Coefficient (ICC) evaluated the agreement between two 1'STSTs. Pearson Correlation examined the association between the 1'STST and other physical measurements, and their changes following PR. A receiver operating characteristic (ROC) curve was constructed using a 30-meter increment in the 6MWT as cut-off to identify responders. Results: The 1'STST demonstrated good reliability (Δ0.9 ± 4.0 repetitions, p = .13; ICC = 0.79). The 1'STST was moderately correlated with the 6MWT (r = 0.57, p < .0001), VO(2)max (r = 0.50, p = .0006) and maximal work rate (r = 0.52, p = .0003). Weak correlations were observed with QF (r = 0.33, p = .03) and step count (r = 0.38, p = .013). The 1'STST improved after PR (∆ = 3.6 ± 6.4 repetitions, p = .0013) and changes correlated moderately with changes in the 6MWT (r = 0.57, p = .002), QF (r = 0.48, p = .003) and VO(2)max (r = 0.41, p = .014). A cut-off of three repetitions demonstrated a 71% accuracy in identifying responders to a rehabilitation program. Conclusion: The 1'STST is a valuable alternative to evaluate exercise capacity in patients with COPD when more expensive and time-consuming tests are unavailable.