Dr. Gibala: I think we've at least talked about it before, the notion of REHIT. At the same time as we were sort of coming up with the one-minute workout, UK researchers Metcalfe, Vollaard, they've done a lot of this work.

They termed what they called reduced exertion high-intensity training on a very similar theme where they were using a 10-minute start to finish workout, but their protocol involves 10 to 20, only one to two 10 to 20-second efforts. So all of this variations on a theme where we're talking no more than one minute of very intense exercise in a 10-minute time course.

And we've done a number of studies now looking at that workout and showing that, certainly, you know, it can improve VO2 max...many of the things we've talked about, it can improve it to at least very similar extent as more traditional modern intensity continuous training that takes five times longer, five times the total exercise volume.

Rhonda: That's a really big interest, I mean, I think, to a lot of people. So I mean, that's...for me and, I mean, people that I know, a lot of busy people that I know, I mean, it's like, you know. So I guess the moral of the story here is I think I've...the work-to-rest ratios in a way do matter to some respect because...and that was kind of a big question for me was what I'm doing every day was a very specific work-to-rest ratio, but going a little bit harder and that really does make sense and I knew it, like there's something in me that was like, I just need to hear Marty tell me. So thank you. You mentioned some of the other protocols like the REHIT. How does that, you know, how would you say that really differs from high-intensity normal training? I mean, with respect to maybe some of these endpoints we're talking about like VO2 max?

Dr. Gibala: So again, like, you know, first of all, it's all interval training. Whether it's HIIT depends on your definition a little bit and so that's why, again, you know, I really like this idea, this notion or this terminology of interval training because it covers all the bases. It's just alternating more intense, less intense periods of work. High intensity for many is 80% or higher heart rate as a metric and, you know, and we've done this but to try and...because our first work we called everything HIIT, right? Which is much of the field at the time, everything was HIIT. But you know, five minutes at 80% of VO2 max is a very different stress as we just talked about from a 20-second to battle workout. So at least to try and distinguish the interval training a little bit more, there was this move to try and distinguish HIIT, which is intense but submaximal efforts from sit or sprint type training, which is much closer to the sprint from danger base type efforts.

So you know, I would say REHIT is absolutely interval training. It's probably closer to sprint type training than traditional HIIT, which just because of the power outputs. You know, you're working 10, 20 seconds, but these are very, very high power outputs that you're generating and much higher than VO2 max pace. So...

Rhonda: Oh, so I was completely confused about that because reduced exertion, to me, I was going, oh, this is less than 80%.

Dr. Gibala: So the reduced exertion, it was 10 or 20 seconds. It feels a lot easier than a 30-second Wingate and it was because, you know, these investigators know 30-second Wingates hurt and all of the lactic acid and the pain and the discomfort and even the nausea and dizziness sometimes that can go wrong with 30 seconds. If you're doing 15 or 10 seconds, much of that is attenuated. So the exertion comes down from the metabolic feelings and it's not the exertion level in terms of the power outputs on the bike. Just to take that one step further, Dr. Ed Coyle at the University of Texas at Austin, big name in the field of exercise physiology. Dr. Coyle's recent work is looking at four-second all-out efforts, but doing a fair number of them. And it's really just a variation on a theme. And Dr. Coyle's point would be, you can work very, very hard, even fairly deconditioned people can put out extremely high power outputs for four seconds. Then you give them, I think it's 12 seconds of recovery and they do it again.

And so the point there is these very short, very hard efforts aren't associated with the feeling, the perceptions of discomfort when we initially think of Wingate tests, sprint from danger pace. And you know, there's a lot of critics certainly on the behavioral side of things who are saying interval training is doomed to failure as a public health priority because we know that anything above lactate threshold, it hurts. It makes people uncomfortable. They're less likely to do it. But there's a whole other group in the exercise behavior field are going like, well, wait a minute, continuous high intensity efforts, even continuous sprint efforts are very different from intermittent high intensity efforts. And so there's a lot of, certainly a lot of arguing right now and a lot of Twitter polemics, but I think still a lot of good work to be done looking at these perceptual responses to different types of interval training. It's too simplistic to just go, well, sprint type training, no one's going to do that because it hurts because now there's evidence to show that, well, actually it doesn't. When people rate this, they don't find it as unpleasant, as uncomfortable as some make it out to claim that it is.

Rhonda: So the reduced exertion interval training, the REHIT, reduced exertion high intensity training is you still... They're messing around with more of the work to rest ratios and you are still going, you're still going very hard, but your perceived exertion isn't as high as it would be if you were doing a Wingate or sprint interval training. And so at the end of the day, it really goes to say that, you know, perceived exertion isn't necessarily the best way to gauge how hard you're going because if you're still going hard on your four or five seconds, you know, you're doing good.