Long term wearing of motion and heart rate sensors are essential aspects for longitudinal studies on physical activity measurement studies. We conducted a qualitative study with seven subjects in a total of 13 test sessions to identify usability and handling problems associated with Stayhealth RT3, Actigraph GT1M and Polar RS800 sensors. We found that battery life limitation is the most recurrent technical problem and long term wear of heart rate sensors produces discomfort and skin irritation.