Fig. 1

Screenshots from Fit 4 Surgery App. a training video for patients on how to use the app. b safety notification screen (c) one of the exercise videos which shows feedback e.g. duration of exercise, heart rate and O2 saturation. d one of the education videos that patients can view using the app. e a summary screen post exercise which shows if target heartrate was achieved, average O2 saturation and motivation feedback. f Additional comments box screenshot