Looks like for this current thing he just shows up day in and day out churning out the swim/bike/run at a modest endurance pace. e.g., I read his average pace for the run was 11:27/mile, but in a post I saw from today or yesterday it was 16:37 per mile, which is basically the speed of a brisk walk.
Seems way different though than the power numbers and physical exertion that pro cyclists hit day in and day out for multi day races.