We’ve all had to lose some weight at some point or another. If you are anything like me, you probably just hop on the treadmill and do your best to find your “happy place” in this exhaustingly boring cardio session. However, there are better alternatives out there that can help you shed that extra fluff. Today, we delve into the now-famous high-intensity interval training, including the many benefits it provides its benefits and some potential issues. 

Before we talk about the benefits of HIIT, we have to understand what it is. There are two core types of cardiovascular training modalities: low-intensity steady-state training (LISS) and high-intensity interval training (HIIT). 

LISS is any type of cardio (whether that’s running, swimming, cycling, etc.) conducted at a low intensity for a sustained period. Technical jargon aside, it refers to a typical jogging session that lasts at least ten minutes. Most of us are quite familiar with this type of training.

On the other hand, high-intensity interval training (HIIT) is a training style that stands at odds with LISS. This type of training is generally much shorter in duration but much more demanding. The typical structure of HIIT workouts is to alternate between very high-intensity rounds and very low-intensity rounds. In other words, in the first 1 minute round, you'd have to sprint at maximal capacity, and in the second round, you get to rest for a minute. You alternate between these two rounds until you reach your allocated workout time, and you are done. As you can imagine, they tend to be lower in duration than LISS workouts.

High-intensity interval training has gained an enormous amount of popularity in the last few years and that’s for good reason, it provides several valuable benefits:

• Simultaneous aerobic and anaerobic improvements.
• Less adaptive interference.
• Saves you a whole lot of time.
• Promotes amazing fat loss.

Although it is a minor effect on individuals already strength training, HIIT can produce both aerobic and anaerobic improvements. Unlike slower jogging sessions, this type of workout trains the same pathways as your typical strength training, and as such, it can elicit similar results. If you are a typical endurance athlete, this can be a good way to get some added muscularity without having to do any strength training. Furthermore, if you are the typical “bro” that skips leg day, HIIT can be a decent way of training your lower body while shedding some fat.

As I just mentioned, HIIT trains similar pathways to a typical strength training routine. As a result, it circumvents what is known as the interference effect. You see, a typical slow jogging session trains your endurance pathways, which are not conducive to high force outputs.

 In other words, if you strength train you are sending a signal to your body that it needs to get stronger and bigger. However, when you jog, you send the opposite signal, that your body should be more enduring. By sending mixed signals, you keep slowing down the adaptation you could get for either pathway.

Instead, by using a HIIT approach, you send a single unified message consistently, ensuring that the interference effect is minimized and the adaptations you elicit from your body are all about strength and power.

The efficiency of a HIIT approach is one of its most appealing benefits. As mentioned in the first point, not only do you get simultaneous improvements, but you get them at a fraction of the time required to perform an effective LISS session.

Why? As a general rule of thumb, the more intense a workout, the less time you need to perform it. There are versions of HIIT that are so extreme that you can get similar results to a 60 minute LISS session in just a few minutes. Extrapolate that to your monthly training time, and you are literally freeing dozens of hours of your time while getting the same results. Granted, as we will see in the drawback section, this type of intensity comes at a cost.

Last but not least, HIIT produces similar fat loss results to the more time-consuming alternatives. How can that be? Thanks to an increased exercise post-oxygen consumption (EPOC), also commonly known as the afterburn effect. Although a HIIT session burns fewer calories during the session itself (after all, it lasts a fraction of the time), it manages to burn a substantial amount of calories after the training session is over. After your workout, your metabolism's expenditure increases by a decent amount for a long period (10-24h), leading to higher total expenditure.

Sadly, there is nothing perfect in life and HIIT is no exception. Although the drawbacks are limited, you should be aware of them before embracing this type of training.

• Extreme intensity requirements.
• Not a good fit for beginners.
• Takes a heavy recovery toll.
• The total potential energy expenditure is limited.

As you know by now, HIIT requires a great deal of intensity. Sadly, if you do not push yourself enough to reach the intensity threshold required, you do not activate the afterburn effect and you are unlikely to promote simultaneous anaerobic and aerobic improvements. In other words, you end up with a subpar training session that barely did anything aside from wasting some time and burning through a laughable number of calories.

You might already be rolling your eyes, you’re not some “wuss” and you know how to push yourself so this won’t be an issue for you. However, we aren’t always at 100%, even the best of us have days when we can’t grind or perform well. In those days, a HIIT workout is unlikely a good option and you better stick to easier training.

As you can imagine, the type of intensity required makes this type of training a bad fit for most beginners. If the last time you’ve performed some actual cardio was PE class in high school, trying a HIIT workout is a likely quick way to get injured.

Beginners need to take some time before embracing this type of training. You should first start with easy jogging sessions and as you improve, you can slowly increase the intensity. Once you are capable of jogging with a decent bit of intensity, you can attempt a HIIT workout. Of course, keep the intensity and duration of the sprinting rounds relatively low and take ample time to rest between said rounds. As you improve, you can start pushing yourself a bit more and decreasing the rest periods getting slowly closer to the “ideal” HIIT session.

High intensity tends to create high recovery demands, which can be an issue. If you are involved in a sport that already stresses your recovery excessively, adding several HIIT sessions a week could put you over your recovery capabilities leading to a drop in performance in your sport. 

From personal experience, I can guarantee that if you push yourself in a HIIT session, the next day your legs will not be capable of performing at maximum capacity, so forget about heavy squats or deadlifts. If you still want to train with a HIIT approach, you need to consider your recovery and modulate the intensity of your HIIT session or your sport of choice, depending on your goals. 

The last drawback of HIIT is the total amount of calories you can burn. Although HIIT can burn more calories than LISS sessions, the amount of HIIT sessions you can perform per week quickly gets capped due to the recovery demands it puts on your body. 

Although you could get away with doing a dozen of HIIT sessions if you are not involved in any sports or other types of training, odds are, if you are reading this you have to consider your recovery capabilities and manage more than one type of training. 

With that in mind, going on walks or very easy jogging sessions can help you increase your weekly expenditure without really taxing your recovery and that’s just not an option with HIIT.

The key takeaway here is that a HIIT-type cardio session can help you burn an extra bit of calories at a fraction of the time of your typical jogging session. However, it is not necessarily for everyone since it can be quite demanding from a mental and physical perspective. Overall, it is a great tool to have in your toolkit and warrants a closer look.