Training and exercise have numerous health benefits ranging from improved mental health, reduced stress, depression, and improved cognitive performance, to cardiovascular and metabolic health.
There has long been anecdotal evidence that training causes a kind of euphoric feeling, a “runner’s high”, but what is the “runner’s high”? and what type of exercise causes this feeling of wellbeing?
It’s been speculated that the cause of the euphoric feeling after exercise is related to endorphins. Endorphins are substances produced by our bodies after exercise. These substances bind to opiod receptors (receptors that modulate pain, reward, and euphoria) and can affect mood and reward. That being said, we still don’t know if it really is the increase in these endorphins that causes the feeling of wellbeing or if there’s just a slight correlation.
A recently published study compared 1 hour of continuous cycling exercise (moderate-intensity continuous training, MICT) to high-intensity interval training (HIIT) consisting of 5 all-out cycling sprints for 30 seconds.
The study found that MICT improved ratings of mood, satisfaction, and euphoria. Whereas the HIIT participants reported lowered mood, reduced satisfaction, lowered motivation, and increased exhaustion compared to the MICT group (Saanijoki et al., 2017).
So, if you want to improve mood, do you just do MICT? Not so fast. An important disclaimer is that the feelings and mood were recorded within 3 minutes after exercise. This is especially important considering that the uncomfortable feelings after HIIT can last for several minutes. It could be that if the participants had a few more minutes of recovery they would have seen beneficial effects.
Previous research has actually indicated that high-intensity exercise seems to more effectively increase endorphin levels compared to low to moderate-intensity exercise (Saanijoki et al., 2017). The “need” for this increased release could be due to the higher stress and more uncomfortable nature of the all-out exercise, but the release is still not enough to be able to counteract the pain from the HIIT compared to MICT.
Also, longer marathon-like exercise has a higher chance of eliciting the “runner’s high”, but shorter, low to moderate-intensity training can generate milder mood improvements.
It is important to note that well-trained individuals might require higher or different intensities to elicit the same feeling of wellbeing as novices.
It seems that moderate-intensity exercise improves mood acutely after exercise whereas HIIT acutely decreases mood. This is not to say that HIIT could not improve mood after a few more minutes of rest, especially since HIIT seems to be more effective at releasing endorphins.
HIIT is an effective training modality for improving health, cardiorespiratory fitness and glycemic control (Gibala et al., 2014) so this study is in no way a good reason to avoid HIIT.
In the end, it all comes down to your own preferences and goals. Do you like to train to the point of exhaustion and feel that you have really given it your all? Are you short on time? Perfect, do HIIT and you’ll reap a wealth of health benefits!
If you have more time, and prefer a more comfortable exercise session, then choose moderate-intensity exercise.
Fredrik Wernstål is a final year medical student with a passion for nutrition, training, performance, and health. His goal is to help people reach a healthier and happier life by providing research-based advice.
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