Exploring Physical Activity During the Discharge Transition Phase in People With Acquired Brain Injury—An Observational Study

•New accelerometer-based algorithm applied to classify activities in everyday life.•Participants with acquired brain injury had a high average active time of 5:49 hours per day.•A reversed relation between cognitive function and physical activity was observed.•Low levels of general fatigue and mental fatigue was related to low levels of physical activity. To explore physical activity trajectories during the discharge transition phase after in-hospital rehabilitation after acquired brain injury (ABI). A cross-sectional observational study. Transition from an in-hospital rehabilitation center to community-based living. Independently walking patients with ABI (n=10) who were ready for discharge. Not applicable. Two weeks of physically active time continuously monitored with an accelerometer and classified by a machine learning algorithm summed as daily average and total active time for each participant and classified into standing, walking, running, bike riding, stair climbing, ambulation, and sedentary time. Physical activity trajectories showing the total daily active time for all participants were inspected before and after discharge, and the average active time per participant was plotted against self-reported scores of potentially explanatory factors. Average total physically active time was 5:49 hours (range 4:26-7:13 hours). Average daily physically active time for participants appeared to be related to functional independence measure sub scores, fatigue, and pre-morbid physical activity level. Individual physical activity trajectories showed a decreased walking activity after discharge, which increased again after 1-2 days. Daily total physically active time among participants was higher than expected. Factors expectedly related to physical activity trajectories in the discharge transition phase were explored and showed some relation to functional scores.