Dr. Lorissa Segal: The Science Behind Outdoor Exercise
- Lorissa Segal
- Mar 15
- 7 min read
AMBASSADÖRK Lorissa wrote us a whopper of a blog explaining the research behind moving our bodies in the out-of-doors. Newsflash, it's important. Like, super super important for aging and growing brains alike.
With that, let's get to it.
ambassadörks
Lorissa: The Science Behind Outdoor Exercise
I’m writing from my perch here on a cozy couch in an old farmhouse on a high plateau in Northern Vermont: Highfields Farm. The room is sun-filled on this Winter day, windows facing both east and west, the air still outside, sun shining on the old maples lining the road and in front of the house, welcoming guests up the drive and to the front door.
It’s 2 below zero right now, at almost noon, but I’m warm here inside. The fireplace in front of me is not lit, but what I imagine to be an ancient, massive furnace down in the cellar is cranking away, throwing heat up through the old metal grates in the painted, wandering wood-planked floor of the living room.
I’m here for the 3rd Eastern Cup races at Craftsbury this weekend. Hundreds of racers are braving the cold to compete in 5 and 10 k individual start skate races yesterday, and a mass start classic of the same distances today. The wooded hills are rolling, and the course is tough, as to be expected. They’ve consolidated the races this weekend, instead of doing sprints and individual starts today, to limit time outside due to the intense cold.
What drives us to do these activities outdoors? Every day we are drawn to bundle ourselves up, buffs pulled up over our chins, ears tucked under our hats, big mittens threaded through our pole straps, clicking down our bindings and gliding out onto the tracks. Pulling away from the Nordic Center even as dusk settles many nights, headlamps flicked on, to ski into the woods.
And as soon as we do so, that first glide down that first little pitch away from the lodge, as that first stride sends us sailing down the trail, it’s as if our brains are cleared of all the weight and worry from the day. Like wood shavings blown off the work bench of our minds, stride by stride we gain clarity, loosen the muscles of our neck and upper back and jaw, and clear our minds.
Do you ever wonder what is happening in our brains when we’re swooshing down the tracks? I do.
We don’t yet understand most of the factors that lead to this magical transformation. Previously thought to be endorphin driven, it appears now that endocannabinoids are responsible for the euphoria experienced with moderate intensity exercise. We’ve found that endorphins don’t cross the blood-brain barrier well (meaning even though they are produced during exercise, they can’t effectively get in to the brain to enhance signaling). In addition we’ve learned that endorphins bind to opioid receptors in the brain, and when these receptors are blocked during exercise (with medications like naltrexone) the euphoric response to exercise is not blunted, showing that there must be another signal instead of endorphins causing our exercise-induced feelings. (1)
We’ve identified endocannabinoids as the likely messengers. These are made by muscle, fat, immune cells and brain cells when we exercise. These molecules look to be the source of decreasing sensations of pain and anxiety, and over time reduced incidence of depression in endurance exercisers.
As we spend more time indoors and on devices, and people try to understand not only what factors improve health, but also try to condense this into easily attainable nuggets, like taking a daily multivitamin, we are trying to quantify exactly what the benefits of being outdoors and exercising are. Can we replicate these somehow without actually exercising and going outside? It seems these are two very important activities in creating immediate and long-term brain health that there is no substitute for.
The Japanese coined the term Shinrin-yoku, or forest bathing (2), more than 20 years ago. In 2004 they established the Association of Therapeutic Effects of Forests which has spearheaded research regarding the benefits of “taking in the forest atmosphere.” Their research shows that after the intervention, subjects who sat in the forest versus an urban area, and who exercised in the forest versus an urban area have lower heart rate and blood pressure, lower salivary cortisol levels, increased parasympathetic (rest and digest) nerve activity, and decreased sympathetic (fight or flight) nerve activity.
Last year a British study evaluating 11-13 year olds showed children who exercised outdoors consistently performed better on cognitive testing (including accuracy and response time) than those who performed the same exercise (30 minutes including a warm up, basketball drills, brief game, and cool down) indoors. The study showed benefit at 5 and 45 minutes after exercise and findings were consistent in cross-over (the same children were studied again one week later but switched roles of exercising inside versus outside). This was the first study in adolescents showing a benefit in cognition after doing exercise outdoors compared to indoors.(3)
Teachers have known this for decades, but now we have evidence to support their efforts to get kids outside during the school day.
Outdoor exercise and specifically in “green” spaces benefits adults, too. A recent study in Spain of adults (average age 40) who exercise in outdoor green spaces versus those who exercise in indoor urban spaces showed better short term working memory in the “green exercise” group, as well as MRIs of their brains showing larger volumes in memory areas of the brains of the “green” group.(4)
The beneficial effects of exercise on the brain are long-lasting as well. A recent study shows that “brain age” (5) is improved with regular exercise. The study compared adults ages 26-58 years old, exercising at moderate to high intensity for 150 minutes per week (including two 60 minute supervised sessions per week) compared with adults who did not. VO2 max increased significantly in the exercise group, and decreased in the control group over the year. Whereas brain age in the control group continued to decline, the exercise group’s brain age actually improved (this is measured in brain volume specifically in critical areas of the brain including the grey matter, ventricles, and white matter hyperintensities (a marker of damaged brain cells)). Compared to the control group, the exercise group improved their brain age by about one year, after one year of exercise.
What is happening in the brain to improve cognition? Immediately with exercise the brain, and specifically the hippocampus (memory forming center of the brain), sees a 10-12% increase in blood flow (6). It appears that immediately released norepinephrine and dopamine activate neurons in the hippocampus. Other factors released from muscle (lactate) and the liver (beta-hydroxybutyrate) during exercise cross the blood-brain barrier and signal increased production of BDNF (brain derived neurotropic factor). With consistent exercise, BDNF acts to improve memory over the long term and helps to prevent age-related cognitive decline.(7)
I hope I haven’t lost you too much in the trees of understanding this forest of benefit of exercise, and specifically “green” exercise. We can clearly measure the benefits of exercising outdoors by looking at immediate bio-markers like heart rate, blood pressure and cortisol levels, as well as the benefits in cognitive testing including cognitive accuracy and cognitive speed. We can also measure the benefits of exercising outside over time including younger brain age, higher brain volumes in executive function and memory centers, and improved cognitive testing results. We’re beginning to understand some of the pathways in our bodies that mediate these changes. Some of them are surprising, like the apparent benefits of lactic acid on the brain.
Thus far, we’re not approaching a pill to replace going outside and getting your heart rate up, so bundle up and get out there for your ski!
Authors Note: I'm so psyched to help represent the awesomeness of Nordic skiing by working with Nordjork this year. My passions include a good challenge including ice cream sundae eating contests and biking the elevation of Everest in one month, being far from civilization, yummy food, art, my sweater collection, and my family. I spend my time working as a town doc, biking, running, and skiing. When not helping the good humans of Woodstock, Dr. Lorissa can be found doing more things outside than staring at the grid.
the closer
What We're Thinking About.
That we wish Dr. Lorissa was our small-mountain-town doc, because dang was this a read. But also? This might be the last time we use the trainer when the trails of Colorado are calling.
1) Siebers M., Biedermann S.V., Bindila L., Lutz B., Fussa J. Exercise-Induced Euphoria and Anxiolysis Do Not Depend on Endogenous Opioids in Humans. Psychoneuroendocrinology. 2021;126:105173. doi: 10.1016/j.psyneuen.2021.105173.
2) Park BJ, Tsunetsugu Y, Kasetani T, Kagawa T, Miyazaki Y. The physiological effects of Shinrin-yoku (taking in the forest atmosphere or forest bathing): evidence from field experiments in 24 forests across Japan. Environ Health Prev Med. 2010 Jan;15(1):18-26. doi: 10.1007/s12199-009-0086-9. PMID: 19568835; PMCID: PMC2793346.
3) Grace Walters, Karah J. Dring, Ryan A. Williams, Robert Needham, Simon B. Cooper,
Outdoor physical activity is more beneficial than indoor physical activity for cognition in young people. Physiology & Behavior, Volume 295, 2025, 114888, ISSN 0031-9384
4) Antonio Baena-Extremera, Cristina Martín-Pérez, Andrés Catena, Julio Fuentesal-García, Green exercise versus indoor urban exercise: Related frontal brain thickness and cognitive performance, Mental Health and Physical Activity, Volume 27, 2024, 100649, ISSN 1755-2966,
5) Lu Wan, Cristina Molina-Hidalgo, Mary E. Crisafio, George Grove, Regina L. Leckie, Thomas W. Kamarck, Chaeryon Kang, Mia DeCataldo, Anna L. Marsland, Matthew F. Muldoon, Mark R. Scudder, Javier Rasero, Peter J. Gianaros, Kirk I. Erickson, Fitness and exercise effects on brain age: A randomized clinical trial, Journal of Sport and Health Science, Volume 15, 2026, 101079, ISSN 2095-2546,
6) Steventon JJ, Foster C, Furby H, Helme D, Wise RG, Murphy K. Hippocampal Blood Flow Is Increased After 20 min of Moderate-Intensity Exercise. Cereb Cortex. 2020 Mar 21;30(2):525-533. doi: 10.1093/cercor/bhz104. PMID: 31216005; PMCID: PMC7703728.
7) Rubén Fernández-Rodríguez, Celia Álvarez-Bueno, Isabel A. Martínez-Ortega, Vicente Martínez-Vizcaíno, Arthur Eumann Mesas, Blanca Notario-Pacheco,
Immediate effect of high-intensity exercise on brain-derived neurotrophic factor in healthy young adults: A systematic review and meta-analysis, Journal of Sport and Health Science, Volume 11, Issue 3, 2022, Pages 367-375, ISSN 2095-2546
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