HIIT increases cortisol
so should we avoid it?
“high intensity interval training (HIIT) increases cortisol - so women should avoid it”
Let’s clear this up…
Yes, cortisol spikes acutely during HIIT.
That’s supposed to happen.
It’s your body mobilising fuel to meet the demand.
Cortisol rises during the session then it comes back down, often to lower baseline levels over time.
What matters isn’t the short term spike, it’s the long term levels over time.
Fluctuations in cortisol are healthy and show you can adapt to stress.
The Evidence:
A recent study (PMCID:10124995) looked at women with PCOS who did 8 weeks of HIIT.
Here’s what actually happened:
Cortisol levels decreased after training
Insulin levels decreased
Insulin sensitivity improved
Researchers suggest this happens because better insulin sensitivity reduces the activity of enzymes that are activated by high insulin and drive excess cortisol and androgens in PCOS.
Translation: you train your body to regulate stress hormones better. The evidence supports HIIT having a positive impact on long term cortisol levels.
So why does HIIT get such a bad rep?
People read “HIIT increases cortisol” and assume it’s bad.
But context matters.. a lot.
A temporary, purposeful rise in cortisol during exercise is a healthy stress response. It’s what stimulates your body to adapt - to build muscle, improve insulin sensitivity and increase resilience.
In fact, all exercise is stressful - you are stressing your body intentionally so it adapts and can respond better next time it is under stress. This is how you get fitter, stronger and faster.
Chronic stress is problematic.
Acute stress is beneficial in the right dose.
HIIT is the latter when programmed properly i.e. when you are able to recover from the stimulus.
More is not better.
You don’t want to be doing HIIT every day.
Recovery is dependent on your fitness levels, nutrition and sleep quality but for most people 1-3 HIIT workouts a week is a good aim and hugely beneficial to health.
Take away:
Women do not need to avoid HIIT, especially not women with PCOS or peri-post menopause, in fact you will probably benefit more due to the potent impact on insulin sensitivity.
You don’t need to avoid HIIT you just need to recover properly from it.
1-3 sessions per week is plenty.
Prioritise sleep, rest days, and balanced nutrition.
Pair it with strength training for the best metabolic results.
including:
Increased insulin sensitivity
Lower baseline cortisol
Better energy and mood
Train smart & recover well.
if you have any questions on this my inbox is always open here.