> The adaptations come from the cardiac system. Basically, the body can use more oxygen more efficiently. I'm quite sure HIIT is near optimal for improving VO2

> The adaptations come from the cardiac system. Basically, the body can use more oxygen more efficiently. I'm quite sure HIIT is near optimal for improving VO2max - and if you look at it through the less of time vs. benefit then it's unrivalled in terms of cardiovascular health.