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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 [1], 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 [2] and recovery-based workouts [3]. 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 [4], 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 [5] landmark article [6] 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 [7] 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 [8] 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 [9]) and minimize the disassembling and deamination [10] 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,” [11] 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.