>In conclusion, if you're out of shape, you can improve a limited number of fitness measures just as much doing 3x8 minutes of higher intensity exercise as much

>In conclusion, if you're out of shape, you can improve a limited number of fitness measures just as much doing 3x8 minutes of higher intensity exercise as much 3×45m less intense exercise over 12 weeks Make no mistake. The metric HIIT improves are limited, but these metrics are the ones we anecdotally use to observationally to separate people who are fit and people who are unfit. In other words, the people who we consider to be "fit" when exercising tend to be extremely high in these specific metrics. I've been doing HIIT almost exclusively for a decade. You may still have high cholesterol after doing HIIT, but your VO2 max will be through the roof. And not just a little. This isn't just for people who are unfit, it can bring those specific metrics to near athlete level performance if you go at it consistently. From a more laymans perspective, VO2 max is the main metric that this type of exercise improves which dramatically improves your observed athleticism in sprinting, running and almost every sport that involves endurance. It won't help you lose your gut or lose weight though. This is just my own anecdotal observations after a decade of using HIIT as my main exercise.