By Evette Smayda
5-minute read
High intensity interval training (HITT) is an efficient way to fit in your exercise, especially for those with a busy schedule. The current guidelines recommend 150 minutes of moderate intensity exercise or 75 minutes of high intensity exercise per week. By dedicating just fifteen minutes a day, five days a week to high intensity exercise, you can easily meet the weekly target.
HIIT workouts offer a multitude of benefits, not just time efficiency. They have been proven to enhance cardiorespiratory fitness1, body composition2, insulin sensitivity3, and other metabolic markers4. Additionally, HIIT can boost muscular endurance5 and strength6, and reduce blood pressure7,8. While it’s true that HIIT is challenging, the rewards it offers are substantial.
Unfortunately, there is a downside to HIIT. HIIT workouts have been shown to increase cortisol levels in the blood. Research shows that increases in cortisol after a HIIT workout only last a few hours9,10. But when other stressors in life contribute to increases in cortisol levels, this may not be a good thing. Most of us do not need additional cortisol throughout the day and may need to take steps to bring down cortisol levels to baseline.
First, cortisol is not a bad thing. We need cortisol, and your entire body needs cortisol to function correctly. Also, not everyone is affected by increases in cortisol. Many people have normal cortisol levels that drop and return to baseline, and it does not affect them negatively. However, for others, cortisol levels remain high and do not come down to a normal level because the body is in a state of constant stress or chronic stress. Chronic elevated cortisol may be responsible for a lot of poor health outcomes.
A paper published in the journal Cells in 2023 showed that chronic stress with high cortisol levels could lead to neurodegenerative diseases such as Alzheimer’s and Parkinson’s disease and psychological disorders such as major depressive disorder. It also said that abnormal cortisol levels can cause chronic pain, with increased pain sensitivity and susceptibility11. Another study published in 2019 in the Journal of Endocrinology and Metabolism showed that elevated cortisol for extended periods may be a cardiovascular risk factor12.
So, what is cortisol exactly? Cortisol is a hormone produced by the adrenal glands found sitting on the kidneys. This hormone is usually higher in the morning and then declines throughout the day. Cortisol is responsible for different bodily functions such as maintaining circadian rhythm, blood pressure, metabolism and blood sugar. It is also needed to keep inflammation levels low, and when you face a stressful situation, it helps prepare your body for stress by redirecting blood flow and increasing heart rate and blood pressure. The stress response relating to cortisol is the most known reason we need cortisol. When we undergo a stressful event, our cortisol levels spike. For many people, after that spike in cortisol, a few hours later, it returns to baseline or normal. But this is not the case for others, as stress keeps accumulating, not allowing cortisol levels to decrease.
Picture yourself taking a peaceful walk in a forest. The sky is blue with a few clouds, the temperature is just right, and the sun is hitting you in a perfect position when suddenly you are spotted by a bear. You freeze and make eye contact with the bear. You see it, and it sees you. You quickly turn around and start running back the way you came, as fast as you can. The bear is chasing you, but you suddenly have a boost in energy, and you outrun the bear, making it safely into your car, where you quickly drive away. Unfortunately, the beautiful walk in the forest turns out to be a terrifying encounter with a bear, and even though you are safe in your car, driving away, you still can feel your heart beating fast, and your breathing is still not at its normal rhythm. This stressful event caused a quick spike in cortisol, more than your body usually makes. This stress response is often known as fight or flight. It is a normal reaction to a stressful event. Just imagine, though, that after that encounter, your body is still in flight mode when you hit a traffic jam on the freeway you must take to get home.
You must be home by a specific time because you have a service repair person coming to your home that you cannot miss. You feel stress rise in your body as you sit in bumper-to-bumper traffic. Your normally ten-minute trip home takes an entire hour. The traffic jam was caused by someone not securing their load. Furious, you drive past the vehicle that lost the load, making sure you give the driver a scathing look of disapproval. You get home five minutes late and find the repair person sitting in their vehicle, ready to leave. You run after the vehicle, and although you know they saw you running after them, they still drive away. You find a note on your door saying that they would try again since you were not home, but the wait time is two weeks. You get inside and slink to your couch, where you turn on the television and watch a few episodes of an action/mystery show you like. You have nothing prepared for dinner, so you snack on chips and eat out of a tub of ice cream while drinking wine. You are doing what you can to forget about almost being eaten by a bear, being stuck in traffic, and missing the repair person. You notice you got lost in time, and it was late, much later than your bedtime. It’s funny because you don’t even feel tired after such a stressful day, but you go to bed anyway.
You fall asleep quickly but wake up a few times during the night; the next day, you feel awful. Stressed, tired, and cranky. The following week is full of other stress, deadlines, meetings, a job you don’t like, bill payments, more traffic, and waiting for the repair person to come back to fix an appliance you rely on. The following week, you have a doctor’s appointment, and not only did you gain ten pounds over the past year, but your blood pressure also increased. Your doctor also requested blood work. You are even more stressed about what those results will show since you can’t seem to stop eating junk food. Unfortunately, although we need cortisol, for some people who have chronic stress, those levels of cortisol never drop back to baseline. It is one stressor after another, keeping those cortisol levels elevated.
Although getting chased by a wild animal is not typical, you may find yourself in a HIIT workout. Although HITT has a lot of benefits, your body may have a similar response when doing a HIIT workout to that of being chased by a bear in the wild. In both cases, cortisol levels increase, giving your body the best chance of survival if that situation arises. Your nervous system responds to the HITT workout similarly as if it were in flight from the bear. That’s why practicing meditation after your workout is highly beneficial. Not only is meditation important after a HITT workout, but it is also essential every day to ensure you bring your cortisol level back to baseline and keep the correct balance of cortisol levels in the blood.
Meditation practices have existed for thousands of years, but they have only recently been studied, and the benefits of meditation are becoming more well-known. Meditation is an efficient, quick, and easy way to reduce cortisol levels13. Not only does meditation reduce cortisol levels, but it has also been found that it can reduce blood pressure, heart rate, triglycerides, and inflammatory responses14. Meditation brings your body into balance, helping you better face challenges that may come your way.
This is why my HIIT workouts include a 10-minute meditation practice. It is a winning combination. You get the benefits from doing a HIIT workout followed by meditation, which brings your body back into balance. Whether you choose to do the HIIT workout daily or not, look at getting meditation in as often as you can. You can find free meditations in my free content section on my website or look for apps that lead you through meditation.
Empowering you to be the best version of you possible, with love and gratitude,
Evette
References:
1Peng, Y., Ou, Y., Wang, K., Wang, Z., & Zheng, X. (2023). The effect of low volume high-intensity interval training on metabolic and cardiorespiratory outcomes in patients with type 2 diabetes mellitus: A systematic review and meta-analysis. Frontiers in Endocrinology, 13. https://doi.org/10.3389/fendo.2022.1098325.
2Batacan, R., Duncan, M., Dalbo, V., Tucker, P., & Fenning, A. (2016). Effects of high-intensity interval training on cardiometabolic health: a systematic review and meta-analysis of intervention studies. British Journal of Sports Medicine, 51, 494 – 503. https://doi.org/10.1136/bjsports-2015-095841.
3Gallo-Villegas, J., Castro-Valencia, L., Pérez, L., Restrepo, D., Guerrero, O., Cardona, S., Sánchez, Y., Yepes-Calderón, M., Valbuena, L., Peña, M., Milán, A., Trillos-Almanza, M., Granados, S., Aristizábal, J., Estrada-Castrillón, M., Narvaez-Sanchez, R., Osorio, J., Aguirre-Acevedo, D., & Calderón, J. (2021). Efficacy of high-intensity interval- or continuous aerobic-training on insulin resistance and muscle function in adults with metabolic syndrome: a clinical trial. European Journal of Applied Physiology, 122, 331 – 344. https://doi.org/10.1007/s00421-021-04835-w.
4Khodadadi, F., Bagheri, R., Negaresh, R., Moradi, S., Nordvall, M., Camera, D., Wong, A., & Suzuki, K. (2023). The Effect of High-Intensity Interval Training Type on Body Fat Percentage, Fat and Fat-Free Mass: A Systematic Review and Meta-Analysis of Randomized Clinical Trials. Journal of Clinical Medicine, 12. https://doi.org/10.3390/jcm12062291.
5Gibala, M., & McGee, S. (2008). Metabolic Adaptations to Short-term High-Intensity Interval Training: A Little Pain for a Lot of Gain? Exercise and Sport Sciences Reviews, 36, 58-63. https://doi.org/10.1097/JES.0b013e318168ec1f.
6Alzar-Teruel, M., Aibar-Almazán, A., Hita-Contreras, F., Del Carmen Carcelén-Fraile, M., Martínez-Amat, A., Jiménez-García, J., Fábrega-Cuadros, R., & Castellote-Caballero, Y. (2022). High-intensity interval training among middle-aged and older adults for body composition and muscle strength: A systematic review. Frontiers in Public Health, 10. https://doi.org/10.3389/fpubh.2022.992706.
7Costa, E., Hay, J., Kehler, D., Boreskie, K., Arora, R., Umpierre, D., Szwajcer, A., & Duhamel, T. (2018). Effects of High-Intensity Interval Training Versus Moderate-Intensity Continuous Training On Blood Pressure in Adults with Pre- to Established Hypertension: A Systematic Review and Meta-Analysis of Randomized Trials. Sports Medicine, 48, 2127-2142. https://doi.org/10.1007/s40279-018-0944-y.
8Edwards, J., Deenmamode, A., Griffiths, M., Arnold, O., Cooper, N., Wiles, J., & O’Driscoll, J. (2023). Exercise training and resting blood pressure: a large-scale pairwise and network meta-analysis of randomised controlled trials. British Journal of Sports Medicine, 57, 1317 – 1326. https://doi.org/10.1136/bjsports-2022-106503.
9Dote-Montero, M., Carneiro-Barrera, A., Martínez-Vizcaíno, V., Ruiz, J., & Amaro-Gahete, F. (2021). Acute effect of HIIT on testosterone and cortisol levels in healthy individuals: A systematic review and meta‐analysis. Scandinavian Journal of Medicine & Science in Sports, 31, 1722 – 1744. https://doi.org/10.1111/sms.13999.
10Ph.D., N., & Ph.D., A. (2022). Effect of High Intensity Interval Training on Plasma Cortisol Level in Women with Abdominal Obesity. The Medical Journal of Cairo University. https://doi.org/10.21608/mjcu.2022.257363.
11Knezevic, E., Nenic, K., Milanovic, V., & Knezevic, N. (2023). The Role of Cortisol in Chronic Stress, Neurodegenerative Diseases, and Psychological Disorders. Cells, 12. https://doi.org/10.3390/cells12232726.
12Manenschijn, L., Schaap, L., Schoor, N., Pas, S., Peeters, G., Peeters, G., Lips, P., Koper, J., & Rossum, E. (2013). High long-term cortisol levels, measured in scalp hair, are associated with a history of cardiovascular disease. The Journal of clinical endocrinology and metabolism, 98 5, 2078-83. https://doi.org/10.1210/jc.2012-3663.
13Koncz, Á., Demetrovics, Z., & Takacs, Z. (2020). Meditation interventions efficiently reduce cortisol levels of at-risk samples: a meta-analysis. Health Psychology Review, 15, 56 – 84. https://doi.org/10.1080/17437199.2020.1760727.
14Pascoe, M., Thompson, D., Jenkins, Z., & Ski, C. (2017). Mindfulness mediates the physiological markers of stress: Systematic review and meta-analysis. Journal of psychiatric research, 95, 156-178. https://doi.org/10.1016/j.jpsychires.2017.08.004.
