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

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?

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.

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.

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.