PAI (Personal Activity Intelligence) is a personalized weekly activity program that shows each end user exactly how much exercise their body needs to live a longer, healthier life. PAI is the first scientifically validated score that guides users toward improving their cardiorespiratory fitness (CRF) with a customized, intelligent program. CRF is determined using a fitness age risk monitoring calculator to provide an assessment of current CRF compared to peers in the same age group.