Rasmussen IE, Foged F, Bjørn Budde J, et al. Protective potential of high-intensity interval training on cardiac structure and function after COVID-19: protocol and statistical analysis plan for an investigator-blinded randomised controlled trial. BMJ Open 2021;11:e048281. doi: 10.1136/bmjopen-2020-048281

The authors want to alert the readers that an error has been noted in the sample size and power calculations. The section ‘Sample size’ has therefore been rephrased as outlined below, and figure 4 has been modified accordingly. These changes do not affect the design, conduct or the conclusions that can be drawn from the study.

Sample size

Inspired by a previous study performed at our research centre (Christensen et al. Circulation. 2019 Nov 12;140(20):1684–1686. doi: 10.1161/CIRCULATIONAHA.119.042287; Christensen et al. JAMA Cardiol. 2019 Aug 1;4 (8):778–787. doi: 10.1001/jamacardio.2019.2074), it is expected that the HIIT group will increase left ventricular mass (LVM) up to 17% more than the standard care group with an SD of 10%. However, as the target group for this study is expected to be more heterogeneous compared with the previous study, we assume a lower effect size and precision of the estimate. The different sample size scenarios are depicted in figure 4.