Are Your Constant HIIT Sessions Holding You Back

What is HIIT?

HIIT is periods of high intensity exercise, separated by periods of rest. There are many variations of this from Tabata (20 seconds on 10 seconds off, repeated 8 times) to longer intervals of up to 4 minutes with 3 minutes rest. Typically, these sessions last for around 30 minutes, with the most important factor being the intensity of the exercise. Exercise periods should typically be between 80-95% of max HR to gain the benefits promoted with this type of exercise. Within session rest periods of also very important with regards to the benefits of the exercise with work to rest ratios of ranging from 1:1 to 1:6 for typical programs (We will go into all the details of interval training, fartlek, intermittent training and continuous training in another blog). 

Over the past decade there has been a huge increase in High Intensity Interval Training (HIIT) with some gyms promoting HIIT training in every session, which could be the reason you aren’t getting the results you want.

Here we look at five reasons why your HIIT training could be holding you back.

Energy Expenditure

Lots of people are now performing HIIT training on consecutive days and multiple times per week with the belief that more is better. Studies into this show that HIIT twice a week is the most effective. But the benefits of HIIT have certainly been overhyped by some. If you look at the research then the benefits of HIIT are clear. It should increase your VO2 Max through various mechanisms. BUT IT IS NOT DESIGNED TO HELP YOU LOSE WEIGHT.  Many people will tell you that the Excess Post-Exercise Oxygen Consumption (EPOC) (the amount of calories you consume after HIIT will lead to weight loss). Again, the research will tell you that this is not true and that the additional calories that may be burned are minimal. 

Greater Risk Of Injury

In most facilities HIIT sessions are performed in large groups of up 25/30 individuals, they are fast paced and the “coaches” spend more time cheerleading than they do making sure each exercise is performed correctly. Many people use HIIT style workouts to push themselves to the limit, but when fatigue sets in, exercise technique tends to go out of the window, and this can cause people to run into trouble. Especially if these sessions are being done too frequently (or even on the same day!). 

There is an additional risk for injury in those new to exercise too. Going from nothing or very little into high intensity HIIT style sessions (as described above) all too often results in injury. 

True high intensity training can’t be done frequently as the body cannot easily recover from it. 2 – 3 Sessions a week is what the typical recommendation is for this style of training, to both gain the desired adaptations, and reduce injury risk.


Exercise has a huge amount of positive benefits on health, and is typically classed as a positive stress. But stress is stress, and too frequent, intense exercise just like other life stresses has the potential to fill your stress bucket. Stress is largely individual, different people will have differing levels of stress. Which is going to largely dictate their recovery, performance and results. Take an athlete for example, they may train twice a day, but their life stress is low. Their meals may be cooked or prepared for them, they spend the time in between sessions sleeping and using recovery methods. When you compare this to your typical day to day person, who may work 40 – 50 hours a week (stress), have family (waking up frequently in the night – stress), have financial worries (stress), they may be caring for their elderly parents (stress). It’s clear to see if we were to compare the stress levels between the two there is no comparison, one would be much higher than the other.

Fat Loss

As we established in point 1 the idea behind HIIT training is to increase your VO2 Max and not as some facilities would suggest promote fat loss. Exercise is hugely beneficial for improving your body composition (increasing muscle, and losing body fat),WHEN COMBINED WTH NUTRITION. But the type of exercise matters, and it’s important to consider that exercise can have differing impacts on people’s hunger and consequently eating habits. We’ve all experienced the increase in hunger/cravings after exercise, which makes sense as Intense and frequent exercise, needs fuel and to be recovered from. So understandably the desire to eat when you exercise most days, every day, even twice a day may be higher. Which is what often becomes the reason why people struggle to lose body fat. This increase in hunger causes people to consume more food than they think, and as a result struggle to lose weight, despite training so frequently/intensely. We also have to consider the food as reward dynamic that hinders so many people’s weight loss efforts. Often when people exercise (especially after a particularly gruelling session) they justify their cravings for treats, or high calorie foods, not aware this reward based behaviour is what is causing them to not see the results they want. There’s research showing that this happens[2][3].

In one of the aforementioned studies the participants performed enough exercise to burn 300 calories (unbeknown to them), they were then asked how many calories they thought they had burned, and had them eat that many calories from a buffet.

On average the participants estimated that they had burned over 800 calories, and ate back over 600 calories! Resulting in an overall increase of over 300 calories despite burning off 300 calories during the exercise session. This shows how easy it is to over consume calories, and one common reason people struggle to lose weight.

[2] How post-workout food rewards can sabotage your goals – The Washington Post

[3] Randomised Controlled Trial 

Immune Health

As we can see from this ‘J’ shaped curve in the image below, little to no exercise resulted in a higher risk of illness (URTI – upper respiratory tract infection). Moderate amounts of exercise actually decreased the risk of illness. Whereas very frequent and intense bouts of exercise (especially without appropriate rest between sessions) actually resulted in a higher risk of URTI, more than that of doing little to no exercise[1]. 

We hope that you can start to see the reason why at The Fitness Collective we deliver three distinct forms of training and not just one. We use a personalised approach with our members and our training sessions are limited in numbers to ensure high quality coaching. The programmes are designed by our experienced coaching team. We have the key combination of strength, stamina and flexibility work, alongside personalised nutrition coaching, education for our members (monthly seminars), and a community of like-minded people. As you can see from our testimonials, when we apply our unique approach and combination to training, we get results.

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