The good, the bad, and the ugly. Is High Intensity Interval Training (HIIT) for you?

If you pay attention to sports journals, health magazines, or daytime TV, you have most likely heard the term ‘HIIT’ training. Everyone from TV doctors, celebrities, and your best friends have been preaching the benefits of this high intensity, short duration training. Some of these protocols call for no more than 4-10 minutes a day and make claims of building muscle while burning fat at an incredible rate. Sounds too good to be true, I’ll admit.

What is HIIT or IT training?


Although this style of training has been mainstream for just under a decade, its originates in the 1930’s. HIIT’s debut, or at least the display of its effectiveness, was in 1939 when Rudolf Harbig ran an 800m sprint in 1:46, shaving an incredible 1.6 seconds from the previous world record! This massive success on the track has been attributed to his having trained with a now famous and renowned German doctor, Woldemar Gerschler. Dr. Gershcler had been working with Rudolf, among other track runners, within the parameters of a new program he’d developed to specifically target the ability of an athletes heart. He had hypothesized he could increase the volume of blood an athletes heart could pump per beat, as well as condition the hearts ability recover from strenuous exercise, by focusing on the the time taken between sprints rather than the sprinting itself. The reasoning went like this: Although a persons heart rate increases and decreases in beats per minute (bpm) depending on response to activity, the overall blood volume within the body always stays the same. The stress on the heart to pump the same volume of blood at a fast rate continues for a while following a burst of intense exercise as the heart returns to a slower beat. He believed the body would adapt the heart in this “recovery zone” to pump blood more efficiently by increasing the amount of blood each beat could move.   How he did it – Gershcler would have a runner perform an all-out sprint for 200m. Following the sprint, the runner would have perform active rest like walking, allowing the heart rate to come back down. During the sprint, the runners heart rate would climb to 180bpm or over, whereas by the end of the 90 second rest it would drop back to 120-125bpm. However, if the runners heart rate had not dropped back down to 120 bpm within the allotted 90 seconds, the sprinting effort was adjusted until he accomplished the desired resting heart rate. This ability to return to a recover heart rate of 120 bpm after each graduation on the 200m was responsible, he believed, for the physiological changes in the runners cardiac output – specifically, the amount of blood the heart could move with a single stroke. Less strokes to accomplish the same blood flow translates to a more efficient cardiac system and increased cardiac output/performance.


There is no doubt high intensity interval training is effective in the training and conditioning of a persons athletic ability. However, HIIT has recently taken on many sizes and shapes. With further research into HIIT by sports performance pioneers like Izumi Tabata (the Tabata protocol) and Professor Martin Gibala, the ability to alter a humans physiology moved beyond a change in cardiac output and is now used to help people of nearly all levels achieve their fitness goals.   Many of us are familiar with the claims made of HIIT’s ability to accomplish rapid fat loss. What is of even more interest to most people is the ability to accomplish this loss in fat with less time spent exercising overall. This appears counter intuitive as it would seem the lower caloric expenditure during HIIT as compare with steady state, aerobic exercise would burn less calories. This, in fact, is true. A person who spends 15 minutes following a typical HIIT routine burns less calories than a person following a typical 45-60 minute aerobic routine. But just like how Dr. Gerschler focused on the time between sprints and not the sprints themselves, HIIT’s effectiveness in weight fat loss would also found in an unlikely place; between the times of exercise, not during. The time between HIIT workouts creates a desired physiological response called EPOC

EPOC is an acronym for excess post-exercise oxygen consumption. EPOC is not just a great name for the next Tom Cruise movie, but is a physiological process largely responsible for turning a beer gut into a six pack. In a nutshell, it manifests due to the energy pathways being used while a person exercises. During aerobic activity, the human body uses both glycogen and fat as an energy source to provide muscles with energy (ATP). The primary source during aerobic activity is glycogen (carbohydrate) and to a lesser extent fat. During anaerobic exercise, however, the body can no longer replace the expended energy (ATP) through aerobic metabolism within the mitochondria iself(cell). As a result, the body begins a much faster, albeit much more inefficient, process of ATP production which happens outside the cell membrane and without the presence of oxygen. The ability for the body to produce ATP in this way is severely restricted in time. At maximum capacity, this system can only last for around 1:30 – 2:00 before it must return to a more aerobic state.

Rather than go down the rabbit hole that is the electron transport processes and how they differ in aerobic and anaerobic activity, I will use a metaphor instead. Let us think of the aerobic pathway as our checking account (fat and glycogen as money) and our anaerobic pathway as our VISA (glycogen/debt). Aerobic activity is similar to the effect regular bills have on our checking account; we have enough money in there to cover these bills and if we don’t, we work more or spend less to keep ourselves from being evicted. Anaerobic activity, especially in the case of HIIT, is like the VISA of a recently turned 21 year old while vacationing in Las Vegas. He will spend the entire available credit and he will spend it fast. Upon returning home, he will realize, hopefully, that he has a massive credit card bill to pay. Over the next few weeks he will move funds from his checking account in order to pay the debt he racked up on his VISA. Similarly, during a HIIT session the body uses glycogen as the primary ATP replacement fuel source and in a completely anaerobic state. Following this exercise, the body finds its bank account low on ATP, CP, and glycogen, not to mention all the body tissues in need of repair and waste material in need of excretion or transformation. As a result, the body begins paying ATP back by way of aerobic metabolism of stored fat and conserving what glycogen is left as well as ingested (carbohydrate). The observed effect is a higher than normal resting metabolism of fats as a fuel source, sometimes for up to 36 hours following exercise! Over time, incorporating training such as this can greatly increase the amount of stored fat used as an energy source for the bodies functions. Not only that, but multiple studies have shown this style of training increases both aerobic and anaerobic performance as well or better than just aerobic training.

How do you incorporate HIIT into your workout routine?

A quick search on the internet and classes offered by local gyms will come up with innumerable exercise regimes and protocols. Although many of these will have the desired effect there are a few things to consider first. The number one consideration, in my opinion, is how complex are the exercises being performed. There are a growing number of people participating in Crossfit, boot camps, and kettle bell clubs. While there is no question these clubs and classes will help their clients get the body they want, there is an element of risk involved as well. To the newcomer, the less complex the exercises, the better. A graduated program is ideal, as you will want to incorporate more complex movements as you become better and more fit.

If you are considering Crossfit, boot camp, or any other high intensity group fitness class, I highly recommend you do two things:

Check out multiple group gyms and look at how attentive trainers are to the participants. It is difficult to coach many people at once, especially when there is a laundry list of injuries or medical histories to consider between all participants. A good group instructor will be able to set up a class that will coach movements properly no matter a persons level. I am fortunate to work in a gym where the bootcamps are taught by such trainers. I have, however, worked and been a member with gyms where this is not the case. Injury is almost inevitable in such a class, and you do not want your goals to be pushed back because of something so preventable.

If you have no prior gym experience, ask the group instructor if he or she offers private training. If they don’t, seek out a personal trainer of your own. With only a few sessions you can become familiar with the proper movement patterns which will not only set you up for greater success in the future, but also save you from possible injury. A few sessions one on one with your trainer will also help you build confidence for when you go to class. If you plan on taking Crossfit, I cannot recommend this book enough I have read it cover to cover many times. Kelly Starrette has many insights into how Crossfit should be properly performed, something many Crossfit coaches fail to teach their groups. I do not dislike Crossfit, in fact I believe it is a great way to become superhuman fit! I do, however, cringe when I see the form people are allowed to get away with in some box’s (Crossfit gyms), either as a result of an over sized group or a trainer not having the proper knowledge. Clients should be properly trained and graduated through the different movements. Also, in my opinion no one should be doing dead lifts for time unless they have made it a career choice.

How do I incorporate HIIT with my personal training clients?

The answer is: It depends. I like to incorporate HIIT into a clients training routine almost from day one. Of course, the high intensity part of a new clients interval training will be very different then say for that of a client who I have been training for 6 months. Also, we have to take into account that the effectiveness of HIIT is very dependent on a persons lean muscle mass. The more muscle, the more effective this training becomes. Therefore, a new client and I will focus mainly on foundation movement patterns and muscle building, leaving room at the end of the hour for a quick round of sprints on the elliptical. There is a reason I wait until the end of the hour and another as to why I use the elliptical machine: 1. During a foundation phase of training, it is imperative to ingrain the proper movement form of exercises. Following HIIT, the body is severely fatigued and, as such, a client will find it much more difficult to maintain proper posture and form. 2. With a trainer around it is nearly impossible to use the elliptical machine out of form. This makes for a great framework to achieve maximal output of the clients body while maintaining a level of safety against injury. As the client progresses and develops a better grasp of movements and form, we will transition the HIIT into plyometric exercises such as burpees, switch-lunges, jumping squats, etc. At this point we can begin having 5 minute blocks of HIIT sandwiched by conventional resistance training. This type of training is my favorite to do with clients as it makes the hour go by fast and keeps things fun and intense. Also, for myself and for my clients, I like to use a heart rate monitor. This single device has changed the performance and results of both myself and my clients in the gym so much so that I will not do a workout without one now.


HIIT’s effectiveness has been proven on athletes and average Joe’s and Jill’s  alike. If incorporated into you and your trainers routine properly, you will quickly feel and look better than ever before. Take group classes that offer this type of training so long as it also offers a safe, well managed environment. If you decide to take up Crossfit, BUY THIS BOOK! If you decide on a trainer, find out what their take is on HIIT and how they intend to implement it in your routine. But most of all, find a method of exercise you enjoy and can see yourself sticking with!

Thank you reading! If you found this information useful and enjoyed it, please share with your friends!

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