Simple exercise can limit harmful weight gain New research shows that physical activity equivalent to 100 PAI a week can counteract excessive weight gain. PAI stands for Personal Activity Intelligence and tracks how physically active you are throughout the week. You can measure PAI with just about any device that can measure heart rate. The activity metric has been developed by the Cardiac Exercise Research Group (CERG) at the Norwegian University of Science and Technology (NTNU) under the leadership of NTNU Professor Ulrik Wisløff. Previously, we found that 100 PAI a week can give us a longer and healthier life without cardiovascular disease. Our new study shows that PAI can also help people maintain a healthy body weight."