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), compared with the commonly used standard chair seat height of 46 cm (1MSTS), 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 compared to 1MSTS (-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×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 and 1MSTS 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.