Myth Buster: HITT – is it good or bad?


Is HITT good or bad for you? Well that depends on who’s asking. High-Intensity Interval Training (HIIT) is a well known and effective form of exercise that involves short bursts of intense activity followed by brief periods of rest or low-intensity activity. It has become popular and known for its ability to help people burn calories, improve cardiovascular health, and build muscle. However, there are some misconceptions and misunderstandings about HIIT, particularly in relation to cortisol and fat gain. Let’s address some of these concerns together

MYTH: HIIT has negative impacts on the body because it increases Cortisol which is your body’s stress hormone

TRUTH: HIIT workouts are intense and can temporarily elevate cortisol levels, which is a stress hormone. This is our body’s natural response to intense physical activity. However, the cortisol increase during a HIIT workout is generally meant to be short-lived and part of the body’s normal stress response. After the workout, cortisol levels should return to baseline. In fact, regular exercise, including HIIT, can help regulate cortisol levels over time by improving the body’s ability to manage stress.

The birth of the myth: The reason this seems to have gained popularity is because while the normal stress response is to elevate and return to baseline after the 60-90min session of exercise is over, that might not always happen for a few reasons:

  1. You haven’t given yourself enough carbs and proteins to handle the workout
  2. You aren’t sleeping well, meaning you aren’t getting proper recovery time after your workouts
  3. Your life outside of the gym is also very stressful

Other reasons exist, but it comes down to you haven’t fueled or recovered properly, leading to the workout itself not being the cause of the cortisol increase, but the high intensity of the interval training isn’t helping to calm the system from everything else going on.

MYTH: HIIT causes fat gain

TRUTH: HIIT is not a workout that makes you fat. In fact, HIIT is often recommended for fat loss and improving body composition. HIIT workouts are effective at burning calories during the workout and can also boost your metabolism, which means you continue to burn calories even after the workout is over. The key to fat loss, however, is not just the exercise itself but also your overall diet and lifestyle choices.

The birth of the myth: What might be seen, instead of fat, is the scale isn’t going down, and in fact you look puffier than before. That’s because of the amount of inflammation that is produced with ANY form of physical activity that adds a stress to the body in order for it to grow. As we said above, this is a normal process, but the problem lies when we aren’t able to properly cool down and regulate our system in order to get rid of the inflammation (or puffiness) post workout. This is usually helped by increasing recovery foods after the workout, like protein, and adding in practices that support detoxification or flushing out the system, like saunas, recovery IVs or increasing healthy fats.

MYTH: I will lose muscle from HIIT training 

TRUTH: HIIT can help build muscle, but it’s not typically associated with significant muscle mass gains as traditional strength training. HIIT can help increase muscle definition and tone, especially when combined with resistance exercises. However, if your primary goal is to build substantial muscle mass, you might want to incorporate dedicated strength training workouts into your routine.

The birth of the myth: HIIT is used more so for training endurance and power. Unless you incorporate resistance training into your HIIT workouts that won’t be the focus of your development, which isn’t necessarily a negative. The myth can relate back to that “puffy” look that happens with poor inflammation and recovery management so it gives the appearance of losing muscle. Also, if you do not recover properly, daily movement will feel more fatiguing, which also gives to that illusion.

So is HITT good or bad? There really isn’t a black or white answer to this. HIIT is an effective and time-efficient form of exercise that can be part of a balanced fitness routine. It can help with fat loss, improve cardiovascular health, and enhance overall fitness. It does not inherently make you fat or chronically elevated cortisol levels. The key to making sure you get the most out of your HIIT workouts is in the recovery around it, which is where naturopathic medical care fits in. If you know how to assist your body with appropriate recovery and manage any stress or inflammation that might come up, you’ll be able to see those muscles defined all the better, knowing your hard work is really paying off!

Need help recovering? Book Your Naturopathic Health Assessment Today

If you find that your high intensity interval training is making you feel worse than when you started – it might be time to take a deeper dive into your health. 

Nana-adjoa Bourne Naturopathic Doctor

Dr. Nana-Adjoa Bourne, ND

Dr. Bourne is a Naturopathic Doctor and certified Sports Nutritionist at Axis Therapy & Performance located in Toronto. She works from the inside-out, supporting performance optimization and injury recovery alongside physical rehabilitation. She also incorporates IV Therapy into her treatment protocols

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