HIIT: Work Through the Pain to Reach Euphoria

Andy Peloquin

Personal Training


We all know that exercise can boost your mood and drive away stress. When we engage in high-intensity exercise (such as HIIT), our brains release Brain-Derived Neurotrophic Factor (BDNF), a protein that can boost cognitive function and relax our minds. BDNF can also protect your brain, repair your memory, and reset your mood.


But in a study on opiod release after HIIT Finnish researchers have found that exercise-induced endorphin release in the brain relies on the intensity of the exercise. According to the data, an increase in endorphins can do wonders to alleviate physical and emotional stress, but first, you've got to work through the pain.



The study, conducted at the Turku PET Centre, University of Turku, examined the effects of HIIT training on 22 healthy adults. Positron Emission Technology (PET) was used to measure the levels of radioactivity in the brain after the participants were injected with a radioactive compound. The compound was designed to bond with the opioid receptors in the brain.


Essentially, higher bonding with the opioid receptors was proportionate to a positive mood.

The participants were then subjected to a 60-minute aerobic training workout of moderate- intensity, a high-intensity (HIIT) aerobic workout, and a rest period. PET scans were taken of the frontolimbic regions of the brain (thalamus, insula, orbitofrontal cortex, hippocampus, and anterior cingulate cortex), which are involved in pain, reward, and emotional processing.


Moderate-intensity exercise did nothing to increase binding with the opioid receptors in the brain, but HIIT exercise increased the release of endorphins and other opioid peptides. HIIT also led to increased negative feelings, a result of the higher release of endorphins. However, it ultimately led to pleasurable sensations and euphoria, the other result of endorphins flooding your body.


What does this mean? According to the lead researcher, "Our results highlight that exercise intensity affects endorphin release and that the brain opioid system is involved in both positive and negative feelings caused by physical exercise performed at different intensities."

The researcher went on to explain, "At moderate training intensities, the pleasurable sensations caused by the possible release of endorphins may promote habitual exercise. At very high exercise intensities, the release of endorphins appears to be linked to increased negative feelings and pain, and may be needed to manage the emotionally and physically demanding challenge."


So, HIIT will release endorphins into your body, but those endorphins are used to manage the negative feelings and pain associated with the very high-intensity training. Though "such negative feelings may discourage further exercise," it's essential that you're prepared for them when beginning HIIT training. You'll have to learn to push through the pain and stress of the workout to ultimately experience the high (euphoria) caused by the endorphins produced by the high-intensity nature of the workout.



1. Tiina Saanijoki, Lauri Tuominen, Jetro J Tuulari, Lauri Nummenmaa, Eveliina Arponen, Kari Kalliokoski, and Jussi Hirvonen. "Opioid Release after High-Intensity Interval Training in Healthy Human Subjects." Neuropsychopharmacology advance online publication 16 August 2017; doi: 10.1038/npp.2017.148.

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