[00:01] of the most powerful forms of exercise you can do. It's the fastest way to improve your VO2 max, cardiovascular fitness, and heart function. And in some studies, it's been even shown to make the heart function to resemble a heart
[00:13] problem. There are a ton of different protocols out there. Sprint interval training, the Norwegian 4 by 4 method, Tabata intervals, REHIT, shuttle runs, the Gibala method, and probably 20 more variations people argue about online. So
[00:28] which one's actually the best? I decided to try a bunch of the most popular HIT methods for myself. And while doing that, I dug into the research behind these methods to see which one has the strongest evidence, and which one is the
[00:40] people. So in this video, I'm going to compare the most popular HIT methods, show you which ones I like the most, which ones feel terrible, and which ones effectiveness, efficiency, and sustainability. The idea behind high
[00:54] intensity interval training, or HIT, is quite simple. High intensity exercise for a short period of time, which is the interval. They can last anywhere from 15 seconds to several minutes. Recovery interval at low intensity or at no
[01:06] exercise. Repeat it for multiple rounds. High intensity interval training, or HIT, protocols are usually done at an intensity of 85 to 95% of your maximum You could also do it at lower intensities, but the 85 to 95% range is
[01:23] true HIT. In practice, you're going quite hard. Not an all-out sprint, but you're going fast and hard. Think of it as your 1-mile run speed. The duration of your intervals can vary a lot, and it's not that important. They can all
[01:35] improve your VO2 max and your overall fitness. But longer intervals appear to be better than shorter intervals in research. The first interval training famous ones. It's called the Tabata method. It's created by a Japanese
[01:48] professor, Izumi Tabata, in the '90s. In his 1996 study on Olympic speed skaters, he showed that the very short, ultra-high intensity intervals on the bike ergometer can increase VO2 max as much as longer periods of steady-state
[02:01] cardio. The steady-state group had a higher VO2 max at the end, from 52 to 57 ml per kilogram per minute, whereas the Tabata group went from 48 to 55 ml per kilogram per minute. The percent increase was similar, but the Tabata
[02:15] group exercised only 4 minutes per day compared to 60 minutes of the steady-state cardio group. Arguably, the Tabata group had a greater total increase in the VO2 max. Seven points versus five points for the low-intensity
[02:27] group. But, it's a bit easier to increase your VO2 max if it's lower, if because it's harder to make progress the higher your VO2 max is. The protocol was 20 seconds of ultra-intense exercise up to 170%
[02:42] of VO2 max, followed by 20 seconds repeated for 4 minutes with eight rounds in total. They trained four times a week for 6 weeks, whereas the steady-state cardio group trained 60 minutes a day for 5 days of the week at 70% of the VO2
[02:55] max. It's important to keep in mind that 170% of your VO2 max is not the same as 170% of your maximum heart rate. These are completely different things. 170% of are completely different things. 170% of VO2 max refers to 170% of power output
[03:09] that corresponds to VO2 max. Basically, it's supramaximal effort. It's super hard, beyond what you're capable of. This is what it looks like in practice. If your power at VO2 max on a bike is 250 W, then 170% would be 425 W. That is
[03:24] the kind of effort you can hold only very short periods of time, not even for minutes. Here's my experience doing the Tabata on the bike ergometer. It's very hard, like super hard, and even though it lasts for 20 seconds, you can barely
[03:36] make it. Because it's so short, you need to be going super hard for it to be wondering if you're going hard enough, and the other half of the time you're half-assing it because it's so difficult. Overall, my rating for the
[03:49] Tabata method is 3.5 out of five. Not that it's not effective, it's because it's so hard and most people aren't able to pull it off. Most people will never be able to reach 170% of the VO2 max even if they try to because you need to
[04:01] be literally going all out and then some. If you're not an athlete, then don't know what your maximum is in the first place and you don't know what's beyond the maximum. So, for most people, if they try to do the Tabata method,
[04:13] they end up going around 80 to maybe 110 or 120% of their VO2 max. Which is still you're missing out on a lot of the potential. So, what I think is that it makes sense to reduce the intensity but increase the duration. There's no reason
[04:28] the interval needs to be only 20 seconds. It can be 30 or 60 seconds. You reduce some of the intensity, bring it down to 100% of VO2 max and go for a 60-second sprint. You're probably going to get better results or at least the
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[05:48] Norwegian method is one of the most infamous high-intensity interval protocols out there. It's called Norwegian because it was developed and popularized by researchers Jan Hoff and Jan Helgerud at the Norwegian University
[06:01] of Science and Technology in the 1990s. The Norwegian method is also one of the most brutal HIIT protocols. 4 minutes hard at 85 to 95% of max heart rate, 3 minutes easy between bouts, repeated for four rounds. The biggest difference
[06:15] HIIT protocols is that it's unusually long. 4 minutes is unusually long, not for the entire workout session, but just for one interval. And the intensity is also very high, 85 to 95%. Now, there is a scientific reason for that, why it is
[06:30] intervals appear to be better than shorter intervals for increasing VO2 max. A 2019 meta-analysis of 53 randomized controlled trials found that short intervals, less than 30 seconds, low volume, less than 5 minutes, and
[06:44] effective and time-efficient way to increase VO2 max. However, to maximize VO2 max adaptations, long intervals that last over 2 minutes, high volume, over 15 minutes in total, and moderate to long-term, over 4 to 12 weeks, were
[06:59] better and more effective. Another 2016 randomized controlled trial on overweight and obese people showed that the Norwegian protocol for 6 weeks was superior to 10 1-minute intervals, as well as 45 minutes of moderate
[07:11] continuous training, in increasing VO2 max. So, high frequency and longer intervals are better than shorter intervals and shorter frequency and reason is obvious. You just spend more time doing the interval, you spend more
[07:25] time at the 85 to 95% of your max heart rate, and therefore you're going to get the Norwegian method is considered to be one of the most effective HIIT protocols for athletes especially. It's hard, most average people aren't going to be able
[07:38] are not going to be able to do it. But, for athletes, it's brutally effective. training method has also been seen to reverse the structural age of the heart they incorporated multiple different
[07:53] months, they did three 30-minute steady-state cardio sessions per week at 60 to 75% of the max heart rate. At months 3 to 10, they added the 4 by 4 Norwegian protocol. And by month 6, their weekly workout plan looked like
[08:07] this: two interval sessions for hit, one long base session over 60 minutes at low intensity, one moderate base session for 30 minutes, two strength training sessions per week, and one recovery day. Here's my experience doing the 4 by 4
[08:20] Norwegian method. This is one of the most brutal hit methods, but it's also first few times doing it, but you feel that your cardio and VO2 max is improving every workout. Because it's so intense, you're very dependent of the
[08:33] recovery. If you slept bad or you're a bit sore, you'll immediately notice it interval is always the hardest and weakest in terms of performance. If you can get the first 4-minute interval done, then the second and third ones
[08:46] will be more bearable, and you even start enjoying it a little bit. I think the most difficult, but probably also the most effective hit protocol. Most consistently. They might try it once a month or something like that, but there
[08:59] able to pull it off every week. But, I don't think that you even need to do the it's so effective and intense, doing it every 2 weeks or once a month is already going to be quite good. My overall rating for the Norwegian method is 4.5
[09:13] out of 5. The reason is because it's very effective and is not dependent on necessarily going all out with your intervals. Even if you don't go 85 to interval, if you stay like 80% of your max heart rate, it's still going to be
[09:26] very effective. And the reason for that is because the intervals last for 4 training, the intervals are only 20 seconds, so you need to make them count. seconds. Sprint interval training or SIT was
[09:40] pioneered by Dr. Niels Vollaard at the University of Stirling. You basically sprint all out for 20 seconds and do a few rounds. A 2017 meta-analysis of sprint interval training found that two to three sprints may be enough and four
[09:54] to seven sprints could be more than necessary to increase VO2 max as long as the sprints are done at all out effort. Doing more sprints increases fatigue, but they may provide diminishing returns. In this 2016 study, they
[10:07] compared sprint interval training to moderate intensity continuous cardio and way to get similar results. The sprinting workout consisted of three 20-second all-out sprints with 2 minutes rest between sprints done three times a
[10:22] week. The cardio group was 45 minutes continuous cycling at 70% max heart rate for 12 weeks in total. Both groups saw improvement in VO2 peak by 19%. Both groups also saw improvement in insulin sensitivity, but with no statistical
[10:37] same for mitochondrial content and body composition. The difference is that the sprint group trained in total 30 minutes per week, whereas the moderate intensity cardio group trained 50 minutes in total. Here's my experience training
[10:50] sprint interval training. It's very quick and efficient. You don't need to have as high expectations as with the Tabata method and the sprints are more bearable. It's good to think of sprint interval training as a skill training
[11:02] rather than VO2 max training because the sprints require require good form as safely and effectively. You should try to get better with each sprint in terms of speed. Don't focus on getting your heart rate elevated, focus on running
[11:15] faster and getting your form right. My overall rating for sprint interval training is 4.2 out of five. It's a great time-efficient way to increase VO2 element of sprinting, which is underrated. The Gibala method is made by
[11:29] Professor Martin Gibala and his team at McMaster University in Canada. The idea is basically 1 minute near maximum effort at 100% peak power output followed by 75 seconds of rest repeated for 8 to 12 cycles. It's sometimes also
[11:43] called the little method. In a 2010 study, Gibala and colleagues showed that this method done for three times per week on a stationary bike resulted in mitochondrial biogenesis and cycling
[11:56] the Gibala method. The intervals are long enough to get exhausted if you're going all out, but they're short enough to not die while doing them. The sprints are also manageable enough if done repeatedly, so
[12:09] the overall workout is less intimidating than the Norwegian protocol. Compared to Gibala method is a little bit more sustainable and realistic for average people. First of all, the intervals are less intense. You don't need to go
[12:22] beyond your maximum. Yes, the Gibala intervals are 1 minute compared to the 20 seconds of the Tabata method, but because the intensity is lower, they're minute interval. Most people won't maximize the benefits from the Tabata
[12:34] method because they're not going all out beyond the maximum. And funny enough, Tabata method will end up doing the Gibala method. It's just that they're going to do 20-second Gibala intervals. They are going all out, but they're not
[12:47] going Gibala method, but they're only doing 20-second intervals. So, you intervals instead. My overall rating for the Gibala method is 4.8 out of five, the most practical and realistic for most people. The intervals aren't super
[13:02] long, the intensity is manageable, and you don't need that much recovery time. REHIT or reduced exertion high-intensity interval training was developed as an even more time-efficient version of sprint interval training. The protocol
[13:15] is simple, a 10-minute bike session done three times per week, mostly easy cycling with just one or two very short all-out sprints for 20 seconds. In the original 2012 study, this approach improved aerobic capacity in sedentary
[13:29] adults, while also improving insulin sensitivity in the male training group. It shows that even extremely small doses of intense exercise can produce measurable metabolic benefits. This REHIT is a relatively low effort and low
[13:41] volume type of high-intensity interval training, and I think that it suits mostly absolute beginners or people who are very unfit. I don't think it's people who are above average in terms of fitness.
[13:53] A 2016 study found that a single 20-second all-out Wingate sprint done three times per week for 4 weeks with no warm-up or no cool-down wasn't enough to increase VO2 peak. So, just a single all-out sprint isn't enough, and you
[14:07] need multiple rounds of all-out sprints. That's why the Gibala method or sprint for people who are slightly more athletic. Here's my experience with I was doing REHIT while cycling in the summer outside, and I think it's a good
[14:21] on a long 1-hour bike ride, and then every 5 to 10 minutes or so, you do a sprint for 100 m. It's very manageable and easy because there's no expectations great healthy way to do cardio, but it's also less effective. My overall rating
[14:35] for REHIT is three out of five just because it's not that effective, at least for more athletic or fitter individuals. But, if you're just great way to start. Next, we have 30-second all-out sprints
[14:48] with 30 seconds of rest. This protocol was investigated by Jorge Zuniga and colleagues. In his 2011 paper, he showed that in 12 recreationally competitive triathletes, 30-second intervals beat 3-minute
[15:01] intervals for total session oxygen consumption, session duration, mean oxygen uptake, and heart rate, while also producing lower lactate levels. 90% of maximum power output beat 100% power output for total oxygen consumed and
[15:15] total exercise time. In the original study, the athletes were told to do as many of these intervals as they could do, 30 seconds on, 30 seconds off. In practice, it ended up being 30 rounds, so 30-minute workout in total. Here's my
[15:28] experience with the 30-30 intervals. They're quite difficult, actually. The fine, but after that, they become increasingly more difficult. The last you've kept your speed high. If you start running slower and slower with
[15:42] each passing sprint, you're not doing it correctly. The point is to run as fast as possible every sprint, not slow down. My overall rating for the 30-30 intervals is 3.5 out of five. The reason is that I think the intervals are a
[15:56] going to half as most of the sprints by the end of the workout, you're missing rather do something like the Gibala method or even the Norwegian method. Another strategy to improve your cardiorespiratory fitness is to include
[16:09] also called vigorous independent lifestyle physical activity or Vilpa. It's been found that Vilpas lasting for 1 to 2 minutes, done three times per day, are associated with a reduced risk of all-cause mortality by 38 to 40% and
[16:24] cardiovascular disease mortality by 48 to 49% compared to no vigorous daily activity at all. Exercise snack in insulin-resistant individuals haven't seem to improve glycemic control as well as improve VO2 max. I like exercise
[16:37] snacks, running up the stairs for a bit or just sprinting with my dog. I do those a few times a day. I think everyone should incorporate some form of have to be an all-out sprint or something else very intense, but just
[16:50] move every few hours. My overall rating for exercise snacks is four out of five. They're simple, they're short, and they're not that difficult. Overall, I from some form of high-intensity interval training, especially if they're
[17:04] cardio. If you're doing frequently zone two cardio or some other low-intensity cardio, then you might not need to do additional high-intensity interval cardio at all, then the hit cardio can be a time-efficient and short way to
[17:18] cardiorespiratory fitness. Here's the final rankings for all the HIIT protocols I tried. Tabata, 3.5 out of 5. Norwegian, 4.5 out of 5. Sprint interval training, 4.2 out of 5. Gibala method, 4.8 out of 5. REHIT, 3 out of 5.
[17:34] 30-30 intervals, 3.5 out of 5. And exercise snacks, 4 out of 5. So, if I the Gibala method, sprint interval think these are the most time-efficient ways and the most effective ways in
[17:49] expectations you can get. There are many exercises out there that are worth doing besides HIIT. Check out my video where I rank 100 exercises from my video where I rank 100 exercises from worst to best next.