As pointed out above, 1 minute per day is clickbait. The study used 10 minutes per session. If you are fit, you probably will need more than a 3x20s session on

As pointed out above, 1 minute per day is clickbait. The study used 10 minutes per session. If you are fit, you probably will need more than a 3x20s session on a stationary bike as well. HIIT "works". Even with fit people. Probably especially with fit people. Think how sprinters train for instance. It's a bit hyped now of course. I've seen a lot on the web that puts together a standard circuit training type exercise and calls it as "HIIT". Wrong. Nothing wrong with circuits at all, they are great, but you're not going to get to 90% heart rate with planks. :) "Works" too depends on your goals. "Just HIIT" is better than nothing, I'm sure. But HIIT is (typically) cardio; for best benefit, you would also strength train and do some mobility / flexibility training as well. Diet is an important part of fitness as well. I'll be honest, I personally think HIIT is a better solution for the modestly fit versus the completely untrained. HIIT is much more physically demanding than a standard circuit or jog. Consequently, I think there is a greater possibility of "overtraining" or over-exerting yourself, perhaps to the point of injury. It really shouldn't be "1 minute per day" for instance because 24 hours is probably not enough time for most people to recover from a legitimate HIIT session.