Courtesy of Turku PET Centre
High-intensity interval training (HIIT) triggers endorphin release in the brain.
Source: Courtesy of Turku PET Centre

Researchers in Finland have discovered that exercise-induced endorphin release in the brain depends on the intensity of aerobic activity. This is important because understanding how to unleash the analgesic “painkilling” power of endorphin (your body’s own morphine) could increase exercise motivation and your odds of sticking with a regular workout routine.

The secret to pushing endorphin across the blood-brain barrier seems to be high-intensity interval training (HIIT) which consists of short bursts of vigorous output followed by a period of low-intensity recovery repeated in a cyclical series.* This Finnish study, “Opioid Release After High-Intensity Interval Training in Healthy Human Subjects," was published July 19 in the journal Neuropsychopharmacology.

The research team led by Tiina Saanijoki of the Turku PET Centre at the University of Turku—who collaborated with Lauri Tuominen of Harvard Medical School and others—found that HIIT significantly increased the release of endorphins and other opioid peptides in brain areas associated with controlling pain and emotional valence.

Notably, a one-hour session of moderate-intensity aerobic activity did not trigger a surge of endorphin release comparable to HIIT. That said, other research has found that moderate-to-vigorous physical activity (MVPA) releases endocannabinoids (your brain’s own cannabis) which are colloquially referred to as “bliss molecules” and play a big role in facilitating runner’s high.

In The Athlete's Way: Sweat and the Biology of Bliss (St. Martin's Press) I explore a myriad of endogenous (self-produced) neurotransmitters and hormones that make us feel good during and after various intensities of physical exertion. Although much of the prescriptive advice in this manuscript was based on anecdotal evidence and animal studies available at the time (2007), the latest empirical evidence based on human research corroborates that the key to secreting a smorgasbord of endogenous brain chemicals that make you feel really good when you're finished working out involves mixing up the aerobic intensity and duration. 

For example, the latest research from Finland shows that HIIT releases a surge of endorphins into the brain. However, this release of endorphin comes at the cost of emotional discomfort and the sufferfest aspects of "red lining it" beyond an agreeable aerobic comfort zone. When incorporating HIIT into your workout regimen, be careful not to overdo it. Because all animals (including humans) seek pleasure and avoid pain, if your HIIT workouts are too hard and feel emotionally disagreeable you will inevitably form negative associations with exercise, which could lead to avoidance behaviors—even if you are getting a surge of endorphin.

Therefore, it's best to dole out "doable doses" of high-intensity interval training that deliver quick hits of endorphin while spending most of your aerobic time in a "sweet spot" of moderate intensity that slightly nudges against your psychological and physical comfort zones. This will keep the endocannabinoids pumping.

Additionally, taking slow meditative walks at a very low intensity can facilitate diaphragmatic breathing in a way that triggers the calming effects of acetylcholine (vagusstoff) and GABA which act like tranquilizers within your nervous system.

If you'd like some free advice on how to structure a weekly workout routine that optimizes the endogenous psychopharmacological benefits of various aerobic intensities check out Chapter Six, "The Cardio Program," in The Athlete's Way

*As always, please use common sense and consult with your primary health care provider before beginning any type of new exercise routine—especially one that involves vigorous, high-intensity interval training (HIIT).

References

Tiina Saanijoki, Lauri Tuominen, Jetro J Tuulari, Lauri Nummenmaa, Eveliina Arponen, Kari Kalliokoski, Jussi Hirvonen. "Opioid Release After High-Intensity Interval Training in Healthy Human Subjects." Neuropsychopharmacology, 2017; DOI: 10.1038/npp.2017.148

Fuss, Johannes, Jörg Steinle, Laura Bindila, Matthias K. Auer, Hartmut Kirchherr, Beat Lutz, and Peter Gass. "A runner’s high depends on cannabinoid receptors in mice." Proceedings of the National Academy of Sciences 112, no. 42 (2015): 13105-13108. DOI: 10.1073/pnas.1514996112

Galdino, Giovane, Thiago RL Romero, José Felipe P. Silva, Daniele C. Aguiar, Ana Maria de Paula, Jader S. Cruz, Cosimo Parrella et al. "The endocannabinoid system mediates aerobic exercise-induced antinociception in rats." Neuropharmacology 77 (2014): 313-324. DOI: 10.1016/j.neuropharm.2013.09.022

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