HIIT vs. HIRT: Reducing Workout Stress To Increase Fitness

The fitness world is booming these days. You can see it in the popularity of CrossFit boxes, obstacle course and endurance events, and record-breaking gym construction. It’s encouraging. Inspiring even. But there’s also a downside to the rising gym memberships and event registrations. There are still too many people dealing with recurring patterns of breakdown, burnout, illness and injury. More people are trying to do the right thing, but the flawed approaches they often gravitate to end up derailing them.

Nonetheless, there are changes afoot. It’s an evolution of thinking that’s slowly spreading its way through fitness circles. More forward-thinking coaches, trainers, and researchers are helping right the wrongs of the fitness boom with a general rejection of the “more is better” approach for one that respects the importance of balancing stress and rest, one that moves toward an intuitive approach to workout planning.

More people are implementing strategies to maximize workout return on investment and minimize the risk of injury and burnout that too often result from an indiscriminate approach. The endurance world, for example, is finally rejecting the narrowly focused, overly stressful chronic cardio approach of old in favor of emphasizing aerobic development at lower heart rates, avoiding chronic patterns, and becoming fat adapted instead of sugar addicted. Endurance athletes are embracing the importance of strength training and explosive sprinting just as strength/power athletes are doing more aerobic conditioning. The CrossFit movement itself is an ode to the health and longevity benefits and increased enjoyment that comes from achieving broader fitness competency.

What’s Wrong With HIIT?

I’ve talked recently about microworkouts and recovery-based workouts. Today, I want to delve in further and share a radical transformation in the way high intensity workouts are conducted that will generate fitness breakthroughs while simultaneously minimizing the risk of exhaustion. Specifically, I’m taking aim at the extremely popular workout pattern known as HIIT—High Intensity Interval Training. Sprinting is a part of the Primal Blueprint Fitness Pyramid, but I’ve been wary of the details around traditional HIIT practices because these workouts are quite often too stressful and exhausting to deliver the intended fitness boost they promise.

Yes, you have to challenge your body regularly with hard efforts to build fitness, but most of us do it the wrong way. When you complete a killer HIIT session at morning boot camp or spin class, at home on your Peloton bike, or with the Tuesday night track group, you get a tremendous sense of accomplishment and a flood of feel-good endorphin chemicals into your bloodstream. Unfortunately, the typical HIIT workout can also be depleting, exhausting, and stimulate an assortment of unnecessary cellular damage and inflammation.

It doesn’t have to be that way. Be redesigning your high intensity workouts, you can get leaner and fitter with higher quality, more explosive, less physically stressful workouts that are easier to recover from and thus can be performed more frequently. In short, a better approach involves transitioning from HIIT to HIRT, High Intensity Repeat Training. HIRT is an acronym coined by Dr. Craig Marker, psychologist, certified strength and conditioning coach, and CrossFit instructor from Florida.

Here’s a compare and contrast that can revolutionize your approach to intense workouts….

Comparing HIIT and HIRT

The problem with a typical HIIT workout is that it’s too strenuous—too many repetitions of hard effort that (each) last too long, and with insufficient rest between hard efforts. This results in cumulative fatigue during the workout, a diminishing quality of performance over the course of the workout, increased cellular damage due to this cumulative fatigue, and extended recovery time afterward. These kinds of sufferfests are a great source of satisfaction and personal growth when you high five your fellow bootcamp classmates after an hour of power, or cross the finish line of a big event in which you’ve trained for months to prepare. But including them as a major and recurring element of your training program is a really bad idea. Unfortunately, the sufferfest mindset is incredibly common these days, perhaps suggesting that the ego has more influence that strategic planning or intuitive decision making.

A HIRT workout stops short of the exhaustive nature of HIIT. The essence of HIRT is to conduct maximum efforts, typically of shorter duration, with much longer recovery, and fewer total efforts than a HIIT session. The word “Repeat” in the acronym suggests that you maintain a consistent quality of effort on every repetition of hard work. This means not only the same performance standard, but also the same level of perceived exertion.

For example, say your workout entails running 100-meter sprints across a football field, and you hit 18 seconds for your first sprint. This is a nice controlled, explosive effort with excellent technique, and you assign a perceived exertion level of around 90 out of 100. Hence, you’ll want to do successive sprints in 18-19 seconds each, preserving explosiveness and excellent technique—delivering what you still discern to be 90 out of 100 on the effort scale. If you have to “dig deep” (the implicit objective, and badge of honor, with a HIIT session) just to arrive at 19 seconds on your fourth effort, that’s it, you’re done. If you notice a slight attrition in explosiveness or breaking form during the effort, you’re done. Typically, this might be a little twinge in the hamstrings or lower back, a tensing of the face or chest, or any other indicator that you have played your best cards of the day.

In Dr. Marker’s landmark article titled “HIIT versus HIRT” at www.BreakingMuscle.com, he explains that after HIIT sessions we bask in self-satisfaction of a job well-done, but disregard the health-destructive consequences of these sufferfests: “[Y]our subjective feeling of the effectiveness of a workout is not as important as what science tells us is important to building an impressive base of endurance and changing your body composition.” (That sound you hear is a slap to the face of highly motivated, goal oriented, Type-A fitness enthusiasts across the land. Don’t worry, I’ve been there, too….)

This admonition applies to everyone from elites to novices. Elite athletes are notorious for constantly pushing the envelope and frequently succumbing to injuries or periods of declining performances. Novices generally don’t concern themselves with training strategies, often leaving their fates in the hands of the bootcamp instructor. Without sufficient experience or reference points, they exercise themselves into exhaustion, believing that pain and suffering are part and parcel of the fitness experience.

The (too often) result? Ambitious, well-meaning enthusiasts burn themselves out and then are down for the count. The most dedicated keep going to their detriment, all the while accumulating fatigue, injuries and even pounds. Others simply stay away from the gym by invisible magnetic force. Alas, the subconscious is very good at avoiding sources of pain and suffering. Can we dump this suffering-and-attrition dynamic already?

Side note for those who love to read about sports: For inspiration, check out this article about the greatest marathon runner in the history of the planet, the amazing Kenyan Eulid Kipchoge. The article describes his training regimen as extremely devoted and incredibly impressive, yet he maintains a relaxed mindset, remains in control of his energy output, and never extends beyond his limits into exhaustion. Even the march to the unthinkable two-hour marathon (Kipchoge’s current world record stands at a mind-bending 2:01.39) comes from a sensible approach instead of an extreme one.

Marker explains that there’s an optimal duration for sprinting where you can obtain maximum benefits with minimal cellular destruction, and this is typically around 15-20 seconds. Try to maintain maximum effort for any longer than that and you’re not really sprinting anymore anyway, since it’s impossible to maintain maximum energy output.

Here’s why this works:

Look at what’s happening physiologically over the duration of a near-maximum intensity sprint of any kind (running, cycling, rowing, or kettlebell swings). During the first five seconds of your sprint, lactate starts to accumulate in the bloodstream. Lactate levels double between five to ten seconds, then double again from 10 seconds to 20 seconds—up to what Marker calls the highest acceptable level. As you increasingly feel the burn, lactate doubles again from 20 seconds to 30 seconds. It doubles again from 30 seconds to 60 seconds, causing cellular destruction, ammonia toxicity, and extended recovery time.

As Marker explains, “The amount of lactic acid produced up to 20 seconds [of sprinting] is still manageable, but the next doubling is over the top. Even a single 30-second sprint spikes ammonia levels almost five times! Why trash the body for no good reason? Rebuilding broken down cells is a costly and time-consuming process. And while it’s taking place, you feel tired and run down, with your ATP short of a full stack.”

You may be familiar with the Tabata concept of interval training, which entails a repeating pattern of work efforts lasting twice as long as rest intervals until you complete a Tabata set of a certain total duration. The original Tabata protocol, developed by Japanese physician and researcher Dr. Izumi Tabata and colleagues at the Japanese Institute of Fitness and Sport in Tokyo, calls for four minutes of a 20-second sprint, 10-second rest, 20-second sprint, 10-second rest pattern. In the original studies, Japanese Olympic speed skaters achieved massive boosts in VO2 Max in a short time with Tabata training. Unfortunately, the original Tabata concept has been widely misappropriated into workouts that honor the 2:1 work-to-rest ratio, but carry on for too long and generate cellular damage and exhaustion: multiple sets of kettlebell swings, pushups, box jumps, running sprints, cycling sprints, and so forth. Bottom line with sprint workouts: a little goes a long way, and too much can really mess you up.

How To Transition From HIIT To HIRT

To transition into a more effective, less stressful high intensity workout pattern, pick the sweet spot of 10-20 seconds for your explosive efforts. Take what Marker calls “luxurious” rest intervals to ensure that your cells have a chance to partially or fully regenerate ATP (takes around three minutes) and minimize the disassembling and deamination that occur when you ask your body to perform again and again with rapidly depleting cellular energy.

Finally, conduct between 4 and 10 sprints. You should be able to manage four shorts sprints even if you’re a novice. If you claim you can complete more than 10 and feel great, you’re better off going faster and doing fewer more explosively.

Keep in mind that a properly conducted HIRT workout is going to feel different than a HIIT sufferfest. It may require an adjustment in your mindset to feel confident and satisfied that you’re training with maximum efficiency and minimal suffering like a “real athlete.” If you’re a focused, driven, goal-oriented type, be vigilant about resisting the addictive allure of the endorphin rush that happens after a sufferfest. Remember, the blissful feeling of powerful pain-killing chemicals flooding your bloodstream is a fight or flight reaction to the extreme stress of the workout. Realize that the genetic purpose of the endorphin response is to help you continue to run for your life instead of lay down in exhaustion! If you abuse this delicate mechanism with a chronic pattern of extreme workouts, you’re going to pay a heavy price. Dr. Tommy Wood calls this overactivation of the fight or flight response, “liquidating your assets,” and I couldn’t agree more.

Several friends who have recently updated their approach to a HIRT protocol report feeling much better in the days following their most challenging sessions—more energy, less soreness and stiffness. That’s how it should be.

Combine the HIRT strategy with recovery-based workouts and walking. See how it goes for you, and let me know. Thanks for stopping in. Share your questions and thoughts below, too.

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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32 thoughts on “HIIT vs. HIRT: Reducing Workout Stress To Increase Fitness”

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  1. No one is posting yet. Too shocked. Cross fitters sitting, numb and catatonic, at their keyboards….

  2. What is the duration of rest periods then? And can we apply the same for high intensity resistance training?

    1. The duration of the rest is different for everyone. You rest until your heart rate drops back to normal, you can breathe normally and feel you can go just as hard for 15-20 seconds again.
      It’s pretty simple , just listen to your body. For me, if I use an Airbike for my HIITs ( Now i realise i have been doing HIRTs all this time ) and my rest period can be up to 4 minutes and i can go about 6 times before my output drops.
      There is no formula or set time becasue everyone is different.
      I initially did those so called HIIT classes, 30-45 secons effort, 30-45 seconds rest. All for 45 minutes.
      There is no way i was doing max effort this long and that often for 45 minutes, byt yeah, i felt great after. And trashed the day after. Even tho i like those classes because sometimes it’s nice to have someone tell you what to do, i dont think they’d be very popular if people were told torest 3 minutes and just stand around when music is blearing and it’s all about “come on, yeah, harder”
      Just imagine seeing a calss with 20 people just standing there for 3 minutes and only actually “train” 15-20 seconds…

  3. Hi Mark,

    how would you suggest to transform a running HIIT Training (5x1000m full speed (18-19 km/h) with 1000m recovery distance with baseline speed (12 km/h) inbetween) to HIRT. Cause this is my “tool” to become faster for the 10.000m. Should I recover 1500-2000m in between?

    Thanks and kind regards from Berlin,

  4. Thanks, Mark. As always, intriguing non-traditional insights 😉

    Does HIRT apply to resistance training? you provided a Spring example. I am curious whether the science, or your personal experience, suggests a similar approach to resistance training.

    1. I have this question, too. I’ve looked on this site and across the internet for reasons why doing hard deadlifts (for example), 4-6 reps to near failure over 15-20 seconds, with 2 minutes rest in between doesn’t do the same thing as sprints or HIRT. Do we really gain anything by adding sprints when our resistance training is done very much like what is described as HIRT?

      Such great info – always giving us new ideas for optimizing our efforts!

  5. Mark, You write the most perceptive articles. I look forward to reading each new offering. Thanks for what you do. Jim

  6. I’ve called it HIIT. I’ve called it SIT. Now I guess I’ll call what I’ve been doing for the last 6 years, HIRT. All I know is I love my 2X per week 8 reps of 25 seconds all out with 1 minute recovery in between workouts.

  7. I switched to HIRT several months ago. I now do 7, 10 second hill sprints, walk to the bottom of the hill and rest a full minute before the next sprint. I used to walk to the bottom and then immediately start the next sprint until I had done 8 to 10 total. Since changing my routine I no longer feel exhausted the next day and now look forward to my hill sprints.

  8. This new protocol is actually relieving to me. I used to dread sprint days, mostly because I was doing them wrong (HIIT), patting myself on the back for going deep into the pain cave more often but not really enjoying the process.

    Now I look forward to these workouts with the longer rests. Workouts are better and the longer rest intervals provide not just physical recovery, but psychological recovery prior to the next effort.

  9. Switch to these and feel amazing. Hungry for more and the next session in a week. I recover much better and even seems to help with T levels spiking and night (better erections) and deeper sleep.

  10. I’ve been intuitively doing 5-7, 10-20 second sprints for over 4 years now. When trying HIIT in the beginning (8 years ago), it just seemed like it was unhealthy and crazy, so I stopped that. I usually do my normal PEM workout the following day with no adverse effects.

  11. The original Tabata approach (20 seconds maximum effort, 10 seconds rest, 20 seconds maximum effort & 10 seconds rest, repeated four times (preceded by two minutes of easy warm-up) looks like it still does the job. No improvements needed I have been doing it one or two times per week for several years. It’s efficient and gives me time, once I catch my breath, to do other things like carry heavy things, balance, walk or play.

  12. My sentiments exactly. If you are paying attention everything in this article is intuitive.

  13. Great article. So, for a beginner such as myself, is there a website that outlines HIRT training regimens, or a way to final a personal trainer who subscribes to this philosophy?

    1. I second this! I am at the very beginning stages of the primal lifestyle and as such, very much a beginner to working out as far as getting the sets/reps/etc right. Is there a guideline anywhere that can give more specific ideas/examples for good HIRT workouts?

      1. Just start out trying to do sprints once every ten days on days you feel good. Move it up to once a week if you’re well recovered from any lifting your doing (you are lifting heavy things, right?). If it’s working really well, you feel great, and you’re sleeping well…perhaps 2 x per week. Any more than than isn’t necessary unless you’re actually training for something specific.

  14. So would you apply this to all types of movement. And just do your 4-10 sprints of that movement with 3ish minutes of rest in between after an easy warmup and then call it a day? Then repeat the next day with a different movement? And repeat every day? I have pretty bad asthma so this sounds like exactly what I need, even more so than most people.

  15. Terrific post, Mark. My sprint/plyo day once aweek that I’ve done for the past 12 years or so follows the protocols outlined here almost to the letter. It seems intuitive, really.
    3 fwd sprints–50yds
    3 backwd sprints–50 yds
    2 side step sprints -50
    2 grapevine sprints – 50
    Finish with a set of bounding, depth jumps, lateral jumps. total workout is 30 mins, no soreness. Barefoot workout on grass football field. Mid 40’s and more explosive than ever. HIRT as you call it is definitely the way to go. Thanks Mark for a great, informative post.

  16. SMALL comment – just noticed there’s a typo in the last sentence of the first bullet point of HIIT vs HIRT. “that” should be “than. Great content; clears up lots of recent questions for me regarding anaerobic training!

  17. Thanks for the great link to my article. I love the stuff you do here. We have been playing with these HIRT style protocols in our research. Without getting too deep into the details, we have been adjusting them to affect mitochondrial fission and fusion (although we can’t measure it directly, it is what we hypothesize is happening). We also built a hypertrophy program based around it: https://strength.university/hirt-for-hypertrophy/ It would be great to talk more about it on your podcast someday. Thanks again for the awesome community and information you provide.

    1. Craig, great to see you on this site. (all the best coming together). I have always appreciated your work. I did your kettlebell snatch protocol and built great endurance and strength. It would be awesome to hear you on their podcast.

  18. OK, Cliff Notes version do I have this right?

    HIRT is basically HIIT with longer rest periods?

    1. Longer rests and shorter (typically – as many have stated, their or a class they attend have 30-45 second work times) work times.

  19. With up to 10 sprints there will be 9 intervals between them, right?
    If i am calculating that right HIRT can be up to 30 minutes?

    I got it but in the end we wil have a more long train? What could we do if we have maximum 20 minutes? We should do less sprints then?

  20. Great article, but am wondering how to reconcile sprints (even in a HIRT) pattern with keeping max heart rate below 180-age (+5 if fit). Specifically, my father is a very fit man, but has stopped doing spin interval training because no way to do even an 75% effort sprint w/o exceeding the max heart rate recs. Please clarify.

      1. Perhaps heart rate is a non-issue with HIRT. In other words, it is what it is. Years ago when i did wind sprints with rest intervals, I never concerned myself with heart rate – just getting in shape.

        1. From what I understand from the books by Phil Maffetone (who developed the 180-age formula), that HR limit applies to long aerobic sessions. For short sessions, it’s a different matter, and the limit seems to be set (as described in the blog post) by time and intensity. That said, in my HIRT sessions, I’ve been using the Maffetone limit. In each rep, I sprint for 10-15 seconds, and then I rest by walking around (or going slow on the elliptical) until my HR drops a few beats/min below the 180-age limit. Typically, I can manage 8 or 9 reps within 30 minutes (maybe 10 someday as I make more mitochondria). The first gaps are about 2 minutes, but they steadily increase. By the 8th or 9th rep, it has gone up to 4 minutes. And, so far, it’s at least 5 or 6 minutes after the 9th rep, which is why I haven’t got in the 10th rep before 30 minutes are done. I take the very long gap also as a sign from my body that it’s time to stop, as it’s having trouble recovering.

  21. HIRT concept has been wonderful for me. I used to love HIIT workouts, but my health and energy is not able to take the stress now and they would leave me exhausted. But I sorely missed the intensity. Swimming and treadmill (not the best I know) had been what I was able to do for HIRT sessions. But now with Gyms closed I have been struggling.

    Any suggestions on how to get a truly explosive 10-20 seconds in an indoor @home scenario without Any equipment like a bike or treadmill?

    Thanks for any ideas !