I think the PB fitness approach is to do low intensity exercise on a frequent basis and high intensity exercise on an infrequent basis.
In other words, walking daily at low-level intensity (or equivalent exercise) and only doing high intensity resistance training for short brief periods (always < about 30 minutes) maybe once or twice a week and as for high-intensity-interval-training, do only for a few minutes maybe once a week.
The approach is to imitate our primal ancestors. Walking daily to hunt and gather. Lifting heavy objects now and then for various reasons. Moving quickly every once in a while to avoid some traumatic experience.