A wearable device including a sensor system for Manual Wheelchair Users (MWCUs) to provide an alert to the MWCUs when there is an increased risk of injury is provided. The wearable device includes sensors measuring the physical activity of the MWCU and transmitting it as user data to a user motion dynamics analysis system on a user device. When the user motion dynamics analysis system determines that there is a risk of injury, it transmits an alert to the wearable device for display to the user.