The impact of seat height on 1-min sit-to-stand test performance in COPD: a randomised crossover trial

STUDY QUESTION: Is there a difference in the number of repetitions in the 1-minute sit-to-stand (1MSTS) test using an individually adapted seat height to 90° knee flexion (1MSTS(IND)), compared with the commonly used standard chair seat height of 46 cm (1MSTS(STD)), in people with COPD? METHODS: We conducted a single-centre, single-blinded, randomised crossover trial in people with COPD between August 2020 and March 2021 at a specialised rehabilitation clinic in Switzerland. After a learning 1MSTS test, all participants performed two 1MSTS tests in random order on consecutive days. Participants were blinded, as they did not receive detailed information on the testing protocols. RESULTS: 49 individuals with COPD (47% female) participated. In a regression model adjusted for sequence period and subject, 1MSTS test performance was lower on 1MSTS(IND) compared to 1MSTS(STD) (−0.78 repetitions, 95% CI −1.47 to −0.11). In a second regression model additionally including the knee angle and an interaction term (1MSTS(IND)×knee angle), the interaction term was significant: 0.18 (95% CI 0.05 to 0.30). The limits of agreement were between −5.5 and 4 repetitions. CONCLUSION: Although we observed a statistically significant difference between 1MSTS(IND) and 1MSTS(STD) on a population level, the difference is negligible. Further studies may be needed to determine whether individual adaptation of seat height is needed for very tall or short people to ensure a valid assessment of 1MSTS test performance in COPD.