Kelyn Soong
THE WASHINGTON POST – Stress surrounds us every day in subtle and substantial ways. Although we can’t eliminate stress from daily life, research shows that by intentionally stressing our bodies through exercise, we can change how we respond to stress and boost our resilience.
Resilience is the ability to bounce back from adversity – a career setback, a relationship breakup or any of the big and small disappointments of daily life – and grow from the experience so that we handle difficult situations even better the next time. Much of the research on resilience focusses on building the skill in childhood, but resilience can be strengthened at any age.
Resilience is essentially an emotional muscle, but a growing body of research shows that stressing our physical muscles by exercise is one way to increase our capacity to cope with daily stress.
“We want to experience manageable stressors so that we can develop stress resilience and not react with a big stress response every time something unexpected happens,” said professor of psychiatry Elissa Epel at the University of California at San Francisco and the author of The Stress Prescription: Seven Days to More Joy and Ease.
“Our body not only can handle acute stress but loves it, and expects it when it’s short-term and manageable.”
The amount and intensity of exercise needed to improve stress resilience depends on the person, according to associate professor of biological sciences Tinna Traustadóttir at Northern Arizona University and the senior author of a 2021 study on the effects of exercise training on physiological stress resilience in adults.
In the study, the researchers randomly assigned 40 sedentary women and men, about half of them young adults and the rest aged 60 and older, to either eight-weeks of aerobic exercise training or a non-exercise control group.
Three times a week for eight weeks, the exercising volunteers pedalled, jogged or stair-climbed at a gym, their workouts focussing on prolonged, moderate intensity sessions on some days and shorter, high-intensity intervals on others. Intensity was based on heart rate relative to each person. The sessions progressively lengthened, from 30 minutes at the start of the study to 50 minutes by the end.
The goal of the study was to test whether regular exercise improved the individual’s response to stress, so the researchers had to come up with a way to re-create stress. They settled on a physiological stressor, inflating a blood pressure cuff to restrict blood flow in the forearm, which is considered a mild stressor mimicking what happens during a heart attack. Blood tests measuring the oxidative stress response followed.
At the end of the study, not surprisingly, the exercisers had improved their fitness, including a 15 per cent gain, on average, in their aerobic capacity.
“This is just an eight-week, not a very long exercise intervention,” Traustadóttir said. “And we were able to show differences that after the exercise training, there was less of an oxidative stress.”
Traustadóttir also found that those in the exercise group had less oxidative stress than those in the control group who were not exercising. And the more a person had improved their fitness, the lower the stress response, whatever someone’s age.
One of Traustadóttir’s takeaways is that to build resilience, it’s not so much about what particular exercises are done, but doing them consistently.
“It’s whatever people will enjoy and will therefore do on a regular basis,” she said.
WHY EXERCISE CAN BOOST RESILIENCE
Studies of stressed-out mice offer clues to why exercise can help us cope better with stress and become more resilient.
In one series of experiments, researchers at Emory University studied the stress response in mice, some of which were allowed to run to their heart’s content on exercise wheels while others were kept inactive.
After three weeks, the scientists checked for markers of a brain chemical called galanin, which is known to increase with exercise and is associated with mental health. (People with variants in galanin-related genes are at higher risk for depression and anxiety disorders.)
As expected, the running mice showed higher levels of galanin. In fact, the more a mouse had run, the more of the brain chemical it had.
To induce stress, the researchers subjected the mice to mild shocks on their paws. All the mice were stressed by the experience, but the running mice bounced back sooner, returning to normal mouse behaviour. Meanwhile, the non-running rodents continued to cower, still overwhelmed by stress.
The study suggested that for the running mice, exercise had increased galanin levels and helped them become more resilient.
Exercise “has profound effects on the way that your brain functions and how the neurons function”, said professor of human genetics David Weinshenker at Emory University and the senior author of the study. “It can actually change the neurochemistry in your brain and promote general brain health.”
EVEN WALKING CAN CHANGE THE BRAIN
Professor of neuroscience Philip Holmes at the University of Georgia, defines stress resilience as the “ability to adapt to stress in a way that’s not deleterious”.
Part of his research deals with the neurobiological mechanisms responsible for stress resilience and the neurobiological effects of exercise. The most significant impact that exercise has on brain function is to promote neuroplasticity, Holmes said. “That really just means changeability, literally a building of connections in the brain,” he said. “And one thing that we found that exercise does is it promotes these connections in the prefrontal cortex, which is a critical area for emotion regulation.”
Holmes’ research on rats and mice shows that even moderate exercise can activate the locus coeruleus, a small brainstem nucleus that is important for attention, arousal, motivation and cognitive function.
The exercise Holmes studied in rodents is analogous to brisk walking by humans.
The locus coeruleus neurons make substances called trophic factors, which promote the building of neural circuits. The stress-resilient parts of the brain get better, healthier circuits while activated, Holmes said.
“So, every time we walk around the neighbourhood, you’re making more of these trophic factors, building more of these circuits,” he said. “It may just be a little bit, but that will be beneficial.”
Weinshenker agrees that moderate exercise can change the neurochemistry in our brains and says any aerobic exercise that gets your heart rate up can be beneficial for stress resilience.
“It doesn’t even have to be vigorous exercise. It could be something just as simple as walking for 20 or 30 minutes a day,” he said. “It could be walking, running, biking, swimming. People play a lot of pickleball now.”
Epel calls the short, concentrated bursts of acute stress to our bodies, such as the stress we experience during exercise, “hormetic stress”.
The term hormetic, she explained in her book, refers to “something that in a larger dose would be harmful, but in a smaller dose is quite beneficial”.
“Hormetic stress works almost like a vaccine,” Epel wrote. “You receive a micro-dose of the ‘virus’ (stress), and then, later, when you face a large, intense similar stressor, you’re essentially inoculated against it.”
