The safety, physiological response and repeatability of the incremental shuttle walk test in survivors of COVID-19.

Background: The incremental shuttle walk test (ISWT) may be a valuable tool for measuring exercise tolerance in patients after a hospital admission with COVID-19. However, the safety, physiological response and repeatability of the ISWT are unknown in this cohort. The present study aimed to explore the properties of this test using the Post-Hospital COVID-19 (PHOSP-COVID) study. Methods: Participants performed two ISWTs, with a 30-min rest between tests, at 5 and 12 months post-hospital discharge for COVID-19. Heart rate and fingertip peripheral oxygen saturation were recorded pre- and post-test. Reasons for test termination were noted. Results: 1593 individuals (median (interquartile range) age 58 (50-66) years and body mass index 31.2 (27.6-35.8) kg·m- 2; 967 (60.7%) males) performed an ISWT; two tests were performed by 1034 and 390 participants at the 5- and 12-month visit, respectively. At 5 months post-discharge, six patients (0.4%) had an adverse event and the most common reason contributing to test termination was breathlessness (826 (54.2%) participants). 336/1470 (22.9%) participants experienced exertional desaturation. Distance walked was greater in the second ISWT compared to the first ISWT at 5 and 12 months post-discharge (mean±sd difference: 5 months: 19±94 m; 12 months: 11±80 m; p<0.05), with an intraclass correlation coefficient estimate of 0.96 (95% CI 0.95-0.97) at 5 months and 0.97 (95% CI 0.96-0.97) at 12 months. Conclusions: The ISWT appeared to be safe in this large cohort, supporting use of this field walking test for this population in clinical and research settings. A familiarisation test is recommended, with further study needed to determine the number of familiarisation tests required to achieve acceptable within-day repeatability.