I've done this for a decade. It's real. I exercise a couple minutes doing all out sprints 3-4x a week and it increased my VO2 max faster then running 5 miles ev

I've done this for a decade. It's real. I exercise a couple minutes doing all out sprints 3-4x a week and it increased my VO2 max faster then running 5 miles everyday. I've tried both. The increase in performance is dramatic. Like you can bring yourself to way above average VO2 max performance doing HIIT on the daily. I want to emphasize though that one thing I noticed is that this is exclusively for VO2 max. I'm not sure if this type of exercise is good for the long term. It's good for increasing your performance.