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Scientists Discover Why High Intensity Interval Training Can Match Endurance Training


Scientists have always struggled to understand exactly how a few short minutes, intense interval exercises can produce similar effects to much more time consuming endurance training.

High intensity interval training, also known by its acronym HIIT, has become very popular in recent years with beginners, professional athletes and patients with reduced muscle functions as it has clear health benefits. Now, researchers from Stockholm’s Karolinska Institutet have discovered cellular mechanisms behind the positive benefits of HIIT and the reason endurance training is undermined by antioxidants.

Short bursts of just a few minutes of exhausting physical activity can prepare muscles to work harder, boosting the production of new mitochondria (powerhouses of the cells, generating the energy that our cells need to do their tasks), which culminates endurance enhancement much like more time consuming endurance training. High-intensity exercise triggers the breakdown of calcium channels as a result of an increased production of free radicals (highly receptive radicals which can act as oxidants for cellular metabolism). The muscle cells thus have anti-oxidative systems for trapping and nullifying the radicals.

The scientists also discovered that antioxidants like Vitamins C and E, very common ingredients of dietary supplements, remove the effect on the calcium channels, resulting in the weakening of the muscle response to endurance training.

Hakan Westerblad, a professor of physiology and pharmacology, said :

“Our study shows that three minutes of high-intensity exercise breaks down calcium channels in the muscle cells.
This causes a lasting change in how the cells handle calcium, and is an excellent signal for adaptation, such as the formation of new mitochondria.
Our study shows that antioxidants remove the effect on the calcium channels, which might explain why they can weaken muscular response to endurance training and they also show that the calcium channels aren’t affected by the three minutes of high-intensity interval exercise in elite endurance athletes, who have built up more effective antioxidative systems. “

The research included male subjects who cycled for 30 seconds for maximum-exertion, followed by 4 minutes of rest and repeat this routine 6 times altogether. Twenty-four hours after the test, tissue samples of their thigh muscles were taken and revealed an increased rate of free radicals, showing that just a few minutes of intense exercise is all it takes for benefits to kick in.

The research has been published in the journal PNAS in an article: “Ryanodine receptor fragmentation and sarcoplasmic reticulum Ca2+ leak after one session of high-intensity interval exercise”.

About the author

Dean Smith

  • That’s great news, especially for people who find it difficult to ‘find’ time to exercise (most everybody!) Even if they can get in 3 – 7 minutes, there’s some payoff.

    • Harry

      And now people cant use the “I dont have enough time” excuse lol

      • Bryan Wood

        lol true. I am currently getting in shape for the first time in my life. I’ve finished a 5k running app (yay tech) and have started a 10k running app. It’s things like this, while I’m a beginner and such, that make me go “well crap, am I doing it right? HIIT or endurance? Weights or no weights?” It’s like how they waffled over eggs being good/bad for you for decades.

        • Dana

          Eggs being good/bad for you is not a debate. They’re horrible for you.

          • Geoff Winans

            I’d like some of the crack you’re smoking.

          • Eduardo Domingos

            Isn’t true! Eggs is the second best food in the world, just loosing for mother’s milk. What’s horrible is the oil where you fry it.

          • DЯESDEN

            Correct. I was gonna say, eggs bad for you? Sure there is a lot of cholesterol in the yoke, but its packed with omega goodness and essential fats, which are necessary for balancing cholesterol in the body.. Besides, low cal, hi protein cant be beat.

          • Some Guy

            Not to mention, cholesterol in food has no proven relationship with cholesterol in the body- we make our own.

          • Terence Elliott

            It’s “losing to”, not “loosing for”

          • Bryan Wood

            Lol see? Debate!

          • Czyrek

            This is the internet, you could post any statement of fact or opinion and someone would be there to say you were wrong.

          • Christian

            you’re wrong
            lmao jk

          • misanthropytoday

            Wrong. You probably think carbs are great for you

          • misanthropytoday

            Wrong. You probably think carbs are great for you

          • fuckingretardsinthisthread

            carbs are good for you, you can’t survive without carbs. you also need carbs for the initiation of protein synthesis.. you know… the thing that helps build muscle.

          • DЯESDEN

            Wrong again Dana, we all need carbs. Its energy for the body.

          • kek

            Lol, you’re retarded

          • AvadaKedavra

            That’s completely and categorically wrong.

          • Justiciar

            The troll is strong with this one.

          • Ruben Ramos

            incorrect. They are great for you. The yolk has received much bad press, which has been proven false in recent years.

          • Dan

            Tell that to my cholesterol

          • DЯESDEN

            Anything can be bad if you eat too much of it, but in moderation and proper portion control, neither carbs or eggs are bad for you. In fact, they are extremely important for you to maintain a healthy diet. Now, if you are overweight and your doctor has cautioned you away from such foods until your levels are regulated, thats a completely different story. But any healthy person can enjoy carbs and eggs and fats without an issue as long as they dont over do it.

    • cyclopath

      On the other hand, this type of maximal exercise is going to require a lenghthy warmup and cooldown.

      • J.r. Dubroy

        If I remember correctly the warm up and cool down should be about 7-10 minutes. From what I’ve heard, however, is that with HIIT it creates a lengthy after burn ( where the body continues burning calories at an accerlated rate) that continues for a while after.

  • SomeGuyNamedMark

    So antioxidents interfere with this response eh? So don’t eat anything rich in vitamins, including supplements, a few hours before or after?

  • Terry Pernell

    I was never into spending long hours in the gym. All I need is an hour at the most and that includes showering and leaving. Good to know I can keep that up!

  • Lord Petyr Baelish

    That’s now possible

  • Timgreetsfromgermany

    This is only addressing triggers for mitochondria genesis and none other of multiple relevant factors for endurance performance. Don’t get me wrong, it’s a well done study. But stop misinterpreting and exaggerate. It takes good skills to understand and interpret scientific papers and this behaviour totally lacks respect and appreciation for those.

    HIIT is not a substitute to high volume training. It’s a very (very! ) good supplement and has its obvious perks regarding basic endurance work.

    • Konstantin Gergov

      Thank you! If only more people could understand how a research works and how data should be read. And if only people wouldn’t argue about eggs and go and understand what exactly a calcium channel is.

  • mark

    Gay eggs are the worst for you. Always landing on the hiiiiiips.

  • Chavez Clemons

    It makes sense.

    In nature, there are long periods of lull followed by intense periods of activity (for example, a lion chasing his next meal or a gazelle trying to outrun a lion).

    Our bodies have found a way to strengthen themselves from this type of activity.

    Very fascinating indeed. I can’t wait to hear more developments.

    • Konstantin Gergov

      Completely true. If you don’t take into account the fact that a lion or a gazelle have a completely different anatomy than a human. Our upright, two-legged structure is the best there is in nature for distance (endurance) running. We are nature as much as all the other species on earth are and we certainly must NOT follow their routines. It makes as much sense as a fish trying to fly because birds are nature.

  • CommunityPride

    “mitochondria (the cell’s batteries)”// I’m disgusted! EVERYONE knows, the mitochondria is the POWERHOUSE of the cell!!!

    • TheLatestNews

      Thank you for noticing this typo corrected.

  • HIIT is something that everyone should be doing and the benefits are outstanding. It is nice to be able to exercise for a short time (don’t forget to warm-up and cool-down) and literally be burning calories hours later sitting on your couch watching TV. My heart-rate stays elevated for hours afterwards compared to traditional exercise where it goes back to my normal resting rate quiet fast.

  • Ted Striker

    Just do both types of exercise, they both have their benefits, add in strength training and flexibility work and you have a complete routine

    Athletes can do coordination/explosive work too but common person doesn’t need that

  • Ted Striker

    Just do both types of exercise, they both have their benefits, add in strength training and flexibility work and you have a complete routine

    Athletes can do coordination/explosive work too but common person doesn’t need that

  • Rob Bohte

    Probably I missed it, my conclusion is when your are amateur/ elite athlete HIT will not increase # of mito’s or hardly compare to healthy ‘untrained’ subjects?!

  • Andrew Magness

    interesting article for sure. I’ve used HIITalmost exclusively for the last several years and have trained for many endurance events with it (50 mile runs, adventure races, ultra bike races, triathlon). I love it. It works for me (ultramentalbook.com). But what this article misses is that HIIT(real hit, what i lovingly call SHIIT because of what it does to my bowels) is inaccessible to most people. Sure, theoretically it can produce the benefits of higher volume training. It does for me. But consistent use of it to create, say, a 15-20 minute weekly routine that maximizes fitness (endurance) is not something that most wanna be endurophiles will be able to tolerate. So for most, even in light of this new ‘research’, traditional high volume training will continue to appeal more I figure.

  • dudeson

    Arn´t free radicals extremely dangerous for the body?

    • SD83

      There was research done recently where they destroyed the pathways in rats that deal with oxidative stress and they found… the rats lived just as long as unmodified rats do. I think there’s a lot that still isn’t understood about oxidation and what effect it has on the body.

  • Jurgy

    so does this mean I should not take vitamin C supplements because vitamin C reverses or prevents the result of a HIIT routiine? …

  • Pav

    Check out my HIIT calculator. Still in beta, it calculates the calories burned after working out. http://www.hiitscience.com/calculator/