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Creeping Cortisol: Is HIIT Overstressing You?

Hey Angels and Alphas,

If you’ve done high-intensity interval training before, you know it can produce some amazing results. But, like anything, it’s best done in moderation. High-intensity interval training has gained massive acclaim as being an efficient way to improve many aspects of your physical fitness.

But without adequate recovery, intense exercise can actually lead to elevated levels of cortisol in the bloodstream and heightened symptoms of physical stress… even when you’re not doing exercise.

What is HIIT?

Whether you’re on a Peloton bike, attending a gym class, or doing a YouTube workout, chances are you’ve heard of or even tried HIIT.  

These short bouts of intense work lasting anywhere from 15 to 60 seconds, followed immediately by active recovery of the same length or longer, make up the main concept of HIIT. A cycle of hard work and recovery that is essentially repeated anywhere between 3 and 15 times. Depending on the workout.

Positive physiological benefits from HIIT also include heightened post-exercise metabolism, improved fasting blood sugar, body composition, insulin response, and more. And because of its benefits gained with only a few workouts, HIIT as a whole has gained a reputation for being a magic pill for exercise.

With HIIT, you might start seeing changes within a matter of the first few weeks, and you’ll walk away from your workouts feeling like you’ve reached an entirely new level of power and productivity.

It only takes a few intervals to experience your body’s heightened level of energy, which is influenced by a massive fluctuation of hormones, especially cortisol.

What is cortisol?

Cortisol is one of the countless hormones that our body produces to manage stress. During high-intensity training, the brain starts sensing stress, and a cascade of these hormones is released. The release of cortisol then activates the sympathetic nervous system, essentially generating a fight-or-flight response. Historically, the sympathetic nervous system’s response to dangers was crucial to our ability to survive, and it provides our bodies with the immediate energy we might need to fight or flee from a foe.

Cortisol is responsible for physiological changes, one of which is the breakdown of fats and carbs and a subsequent rise in blood sugar for immediate energy. Not to mention, repressing the immune system to focus the body’s energy on the potentially life-threatening situation that it’s facing.

HIIT affects cortisol levels in a couple of ways.

Part of what makes HIIT training so effective at turning your body lean and strong is this cortisol response that it will generate. As your legs start pedaling as fast as possible, your brain starts receiving the message that your survival depends on this interval. At that point, cortisol and other hormones are released, creating a response in the sympathetic nervous system. The body then makes the according metabolic improvements following this hormonally demanding situation.  

The problem with cortisol is that when your body builds up too much of it, either because of physical or psychological stress, it will float freely in your bloodstream. This will cause negative symptoms to start creeping into your life. 

Overtraining syndrome, which has some physiological causes, may actually include a raised level of cortisol. The symptoms of overtraining include:

  • anxiety
  • changes in mood
  • muscle fatigue or less power when exercising
  • chronic fatigue
  • changes in sleep patterns
  • repressed immune system response

Naturally, when your body is overly taxed by this imbalance of cortisol, any of these symptoms may be present, even if you haven’t worked out in the last couple of days. 

Ideally, your body should be able to determine on its own when the reaction of fight or flight is useful and actually appropriate. But too much HIIT can send confusing signals to the brain to create a protective response even when our bodies are supposed to be calm and at rest. 

Everyday tasks such as driving to work and packing lunch might leave you feeling slightly agitated because your body is misinterpreting everyday stress as a different type of stress. 

Because HIIT creates this powerful reaction in our sympathetic nervous system, it’s important to prioritize recovery and make sure we’re always getting in enough rest between our workouts, whether they include weights or short bouts of HIIT.

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