thanks for the great reply @hsitz. One thing I did notice that as a fitness marker was the authors heart-rate (BPM). His resting heart rate measured at 48bpm. This is unusual and is in the range of ^endurance athletes^. In fact, soldiers are tested on carefully for this marker. It indicates no matter how fit you may be, resting heart-rate is an indicator of ^endurance^ capability. That resting heart rate means he can push a lot further, longer than most people.