What is HIIT

HIIT is one of the most misunderstood areas of the fitness industry, with a lot of people not even aware of what the acronym means. High Intensity Interval Training is when we perform a cardiovascular activity at 85-100% intensity, for repeated bouts with rest in-between. The goal is a sustained near maximal heart rate, pushing your cardiovascular system close to its maximal capacity.

Why Is HIIT Beneficial

This article is not discrediting the beneficial effects of HIIT training, the inverse, it is attempting that you use HIIT training to your advantage in order to reap the rewards that this extremely beneficial style of training can have. I do not want to labour on the benefits as most of us are well aware that this activity can have very beneficial effects on our cardiovascular system and general health. Here are three of these benefits

Increase Mitochondrial density

Increase VO2 Max

Reduced Inflammation.

5 Reasons to Avoid HIIT Training

When Your Sick

As a CrossFit gym owner, I am constantly witnessing people come to the gym when they are worse for wear. The reality is CrossFit and HIIT in general are very tough exercises regimes, making them very impractical when you’re ill. Interval training has been shown to reduce immune function (1) in the short term, meaning it makes you either less likely to recover and more likely to make your illness worse.

Obviously every illness is different, some small colds might pass but when you have systems that are making you feel more fatigue than normal, thats because your body is working to fight whatever illness you’re recovering from. Make intelligent decisions about when you want to train hard and when you need to rest. Rest doesn’t necessarily mean being sedentary, going for a walk, or just doing a 30 minute LISS session on a bike will be much less likely to impact your recovery and give you the feeling of accomplishment your looking for.

When You Cannot Perform the Exercises Correctly

If you are unable to perform an exercise with correct technique, it seems very intuitive to not do this exercise at a high intensity. If you have done 10 squats in your life and have poor technique, adding intensity to this exercise by doing difficult circuit or high volume repetitions is a very bad idea. It will likely just engrain poor positions, increasing the chance of injury later down the road. I do not want to instill fear that HIIT is bad for you, on the contrary, but there is a time for intensity and there is a time for skill acquisition.

When “Life Stress” Is High

For the 99.99% of us who are not progressional athletes, and even for professional athletes, our lifestyles need to be taken into consideration when we are making decisions around our exercise protocols. The body cannot differenciate between stress from different factors, be that stress from the gym, stress from work, stress from relationships from lack of sleep, the list goes on and on for all the factors which can be affecting the levels of stress we place on our bodies.

Stress is amazing, but only in certain doses, recoverable doses. If you are in a particularly tough time, feel overwhelmed by life, maybe going to your 6am high interval interval session isn’t a great idea? This doesn’t mean dropping your exercise regime completely, it means modifying it to take into account how stress from life is affecting you. I feel exercising is more important when life stress is high as it helps emotionally, but that doesn’t mean exercising in ways that drastically increase fatigue but exercise which builds you up and gives you energy.

When You Do Multiple Sports

HIIT is an extremely beneficial practice as seen above, however when your performing multiple sports in the course of your week you need to be wary about when HIIT is a good idea and when it is a bad idea. Again this all comes back on the stress placed on the body, above we have seen how illness and psychological stress put a load on the body, other physically intense activities do the same and need to be taken into consideration.

In my gym I am constantly seeing people who have been out running that morning and are coming into do a workout that might involve some form of assault bike or rowing intervals. This makes such little senses from an adaptation point of view, you can only send a certain amount of signals to the body at once, doing two intervals or cardiovascular sessions in a day for someone in the general population is redundant.

This is all particularly true when the sport you play or do is very intense, like rugby or MMA, if you doing a very fatiguing sport you need to us HIIT to your advantage and not your detriment. This is all done through appropriate planning of your week and ensuring you are recovering well.

When You Have Already Done 5 HIIT Sessions This Week

I am exaggerating here, 5 is already way to much. HIIT should really only be done 1-2 times a week maximum when your striving for health. This will easily be enough to create the adaptations you’re looking for in the cardiovascular system whilst giving you plenty of time to recover. Doing additional LISS on top of this is highly recommended, alongside resistance evidently. If you are constantly doing HIIT workouts you will eventually start to accumulate to much fatigue and start to see negative effects on your performance but also on factors like mood, general energy levels and sleep. Making intelligent, science based decisions for your exercise routine will result in long term health and have beneficial effects on many other areas of your life.

Sample Monostructural HIIT Workout

Assault Bike Intervals

5 x 60 Cals w/ Rest 1:1

Sample Mixed Model HIIT Workout

AMRAP 5 Minutes

400m Run

12 DB Thrusters

10 Burpees

Rest 2’

Repeat 3 Times

References