Bursting the HIIT Bubble

Bursting the HIIT Bubble
By Henry Toraño

It’s one of the more trendy concepts in the fitness scene. Surprisingly, it’s stuck for a good number of years. High Intensity Interval Training, or HIIT as it’s more commonly referred to has been highly touted as a good way to get fit fast. There has been several companies that have been built around this concept, such as F45 and Orange Theory. It’s all based on the idea that at slower speeds you get slow results, but, if you speed things up, work harder for periods of time, you get faster results. Well, there’s several things that are wrong in this though process and I’m going to clear some of it up so that you can start making better sense of it.

For starters, we need to establish that interval training is by no means “the new thing”. This method has been used for over a century in endurance sports, mainly runners. However, there’s several applications for it that shouldn’t be confused. Interval training merely suggests that bouts of a given activity are programmed with set duration at given intensities with establish rest periods between repetitions. The key here being “given intensities”. By this I mean that not all intervals are necessarily considered high intensity. In fact, perhaps what’s most interesting is that the vast majority of interval training occurs in aerobic settings, which are referred to in the performance world as “moderate intensity”. The main reason for this is that very few sports scenarios place anaerobic demands on athletes. In recreational fitness scenarios this is also the case. Regardless of the fact that we’re calling it “high intensity” actual power output isn’t all that high because the folks engaging in these activities cannot actually express high intensity. So maybe we should also consider what may be requirements to express and ultimately benefit from interval training, regardless of intensity.

For one, let’s consider aerobic (moderate) interval training. These are characterized by repeatable and sustainable bouts of a given activity. Rest periods are generally between one half to twice as long as duration of work. For example, a two minute work interval will be followed 90 seconds of rest. This is not a random concept, but rather proven strategies that confirm that in order for this work/rest ratio to be extended for a number sets, the activity is performed at aerobic efforts as confirmed by lab data, mainly heart rate and lactate monitoring. Now, you can ask anybody that has experience in endurance sports training about when this is implemented into a training cycle. I guarantee that every single experienced coach and athlete will agree that long and slow base training precedes the progressively faster intervals in every training plan. This should also be the case in the athlete’s career. At the beginning, one spends more time building a base. This requires NOT trying to go faster, but rather being able to sustain the SAME effort for longer durations, up to a predetermined functional volume depending on the sport that she is training for. It’s only after this base is set, often a process that takes years, that intervals are introduced into more of the training.

On the flip side, let’s consider what truly high intensity intervals entail. In contrast to the characteristics of aerobic training, anaerobic training is unsustainable. These efforts cannot be held for much longer than the established interval duration. Rest periods often range from three to fifteen times the duration of the work period. The key here is to realize that this is not done just because it says so in a manual. These work/rest scenarios are implemented because the only way in which the athlete’s output metrics will reach the target is by extending recovery for this long. To be clear on this, I’m saying that 0:30 of TRUE high intensity work will require in the ballpark of 5:00 rest for there to be enough recovery for that effort to be repeated. I’m also saying that if you’re performing 10 sets of 0:30 work with 0:30 rest, this are not high intensity intervals, per se. They may be HIGHER intensity aerobic intervals, but aerobic nonetheless. 

Now, you may be thinking that this is all semantics: HIGH intensity vs. HIGHER intensity. But there’s a lot to this seemingly minute detail. If you go out and search for the benefits of HIIT you will undoubtedly come across this point:

Not only do you burn more calories during a HIIT workout than steady-state cardio, but the effect of all that intense exertion kicks your body's repair cycle into hyperdrive. That means you burn more fat and calories in the 24 hours after a HIIT workout than you do after, say, a steady-pace run.
Excerpt from Shape.com’s article: https://www.shape.com/fitness/workouts/8-benefits-high-intensity-interval-training-hiit

They key benefit to HIIT training is the metabolic kick that you get for hours after your workout. This is a 100% true and valid point, but, it requires that the work is performed at high intensity, anaerobic efforts. Otherwise, you’re caught in a middle zone of slightly higher aerobic work that doesn’t provide the benefits of true anaerobic training or slow aerobic training. This is extremely important considering that the vast majority of people engaging in these activities are doing so for weight loss or to lean out. Ironically, this is not a good idea because the aforementioned “middle zone” puts one in what is known as a glycolytic state. This means that you’re body requires sugars for energy and the nutrition protocols required to fuel these activities are not at all like what we know is effective for fat loss. In these cases, what is recommended is more of a polarized approach. By this I mean very slow aerobic work combined with high level contractions. If you haven’t put it together yet, I’m talking about walking combined with weight training. A fitness program that consists of these two aligns perfectly with a nutrition plan that promotes fat loss.

I realize that by now you may be thinking that I’m suggesting that training at high intensities is useless. But this is not at all what I’m saying. I’m not questioning the science, I’m just implying that application of the research is inadequate. This brings us to perhaps the most important point to consider in all of this: INTENT. Why are you even considering HIIT? What’s the purpose behind it? Put more simply, why do you even work out? Stop for a minute and ask yourself these questions. If your answer is weight loss, health, body composition, or longevity then I hate to tell you that you’re actually pulling away from your goals rather than working towards them. 

If you’re working out for any of the reasons I’ve just mentioned you need to understand that a good health and fitness program is one that considers exercise, nutrition, and lifestyle withing the package. These items are not mutually inclusive. You need to ask yourself if the things that you’re doing for those three components align with one another. Is your nutrition plan designed for your goals? Does that nutrition plan fuel the type of training you’re engaging in? Does your lifestyle support recovery and adaptation of the other two? I can tell you that if you’re doing this for weight loss, health, body composition, or longevity in no way does HIIT factor into that equation.

The lifestyle piece is one that is severely underestimated, perhaps because the term is misunderstood in this context. By lifestyle, I’m talking about a set of behaviors such as wake/sleep rhythm, hydration, food hygiene, relationships, and stress management. The latter being a key point in this conversation. Stress is now widely considered the biggest culprit in chronic disease, obesity included. It’s not only because of the emotional toll it takes and the actions it triggers, but mainly because of the physiological effect it has on us. You see, stress triggers the release of a hormone called cortisol. In the fitness scene, it is commonly referred to a as the evil hormone. I cannot think of a worse way to think of it.

You see, cortisol is released by the adrenal glands as a reaction to stressful demands. It speeds up certain processes such as glucose (sugar) metabolism and slows down others, such as digestion, excretion, and fat metabolism to put our bodies in the best possible state to respond to the stressor. You could say that cortisol catalyzes the processes that allow humans to express peak performance. The problem with cortisol is exactly all the reason that I just described as benefits. This due to the fact that all those other processes are also essential for homeostasis. Cortisol is good, but chronically elevated levels will lead to many health problems because of all the activities that it inhibits. Do you know what exercises trigger the highest levels of cortisol? Believe it or not, it’s high intensity activities. You must produce cortisol in order to perform at those high intensities. If you combine high stress bouts of exercise with all the other stress factors commonly associated with everyday life you’re putting yourself in a constant state of elevated cortisol where you do NOT burn fat, digest properly, and are not able to get good sleep. Do any of these sound like they could be conducive to health?

What’s worse is that many people are actually cortisol junkies. This may sound a little extreme, but how many times have you heard the following: “I love my high intensity intervals because I walk into the gym feeling tired and sleepy, but after my training I feel energized and ready for the day”. What’s wrong with that? Well, cortisol is accompanied by adrenaline. The fact that you’re feeling so tired to begin with and only intense exercise can remedy that state, suggests that you are experiencing adrenal fatigue. Your body cannot produce enough cortisol to get you going on its own so it requires an additional dose of stress to make it happen. This kicks off a vicious cycle of you needing more stress to produce the hormonal response and your organs losing its ability to produce them. Again I ask: Does this sound like it could be conducive to health?

I hope that this little bit of information has helped in providing a better understanding of what high intensity intervals actually means and how modern application has failed to do it justice. If there’s one thing that I can recommend to everybody looking to embark or currently in their fitness journey is to periodically pause and examine your reasons for doing what you’re doing. Exercise selection and training modalities should not be a matter of a trends. We shouldn’t simply do something because it exists. In the same way that everything will work for someone, no one thing is good for everyone. Find your why, constantly challenge yourself in your reasoning. Consider exercise, nutrition, and lifestyle as equally important ingredients in your fitness recipe. Lastly, I highly encourage that you seek professional guidance in all of the three buckets. And when in doubt, go slow and lift heavy!