> The whole point of HIT is that you get all of the cardiovascular benefits of endurance sports without the repetitive stress injuries. And the current evidence is that your maximum exertion is what matters, not time spent exercising.

This cannot be true, it contradicts literally all the best training knowledge for distance runners. NCAA cross country coaches and professional distance coaches have their runners doing high mileage easy days and intervals on hard days, and as someone who has experienced this training first hand, you absolutely cannot do the hard days at a proper intensity if you haven’t built up your aerobic capacity through a LOT of easy to medium effort long runs. If they could get all the cardiovascular benefits from HIT, they would only be doing that. The teams that win college championships and the pro teams sending athletes to the Olympics are the ones with the fittest runners, the fittest runners are the ones with the best training. They are doing the majority of their mileage in long easy efforts.

Anecdotally, myself and many teammates I’ve known have seen our biggest jumps in performance come from increasing weekly mileage (more easy miles) and while keeping the volume of hard efforts the same. Time spent exercising matters very much.