Too much stress can feel exhausting. Not only does it leave you mentally drained, but it can also physically tax your body. This is why many of us turn to running as a way to cope with day-to-day stressors. But ironically enough, running is also a stressor — which just proves that not all stress is harmful and a little bit can actually help your health and performance.

“Sometimes [stress] gets a bad rap, like if you have a presentation at work, are dealing with traffic, or have an interpersonal conflict — those things can be bad, but a little bit of stress can actually be good,” says Professor Sarah Lyle, associate professor of psychology and director of the health and wellbeing lab at Eckerd College. The Yerkes-Dodson law, which states a certain level of stress is needed to reach optimal performance, supports this idea. For example, you need to experience some level of stress on the body leading up to race day, so it can make adaptations and lead to a winning performance — it’s just that too much of it can bring you down, Lyle explains.

Oftentimes, stress is misunderstood, but the better you understand it and how it affects your body, the better you can manage it. Here, we break down what stress is, as well as explain the relationship between physical and mental stress, and how it affects your runs.

What is stress?
According to the National Institute of Health (NIH), any physical or psychological stimuli that disrupts your baseline state of stability results in a stress response. Stress can stem from any event or thought and leads to feelings of emotional or physical tension. Exercise itself is considered a stressor, but so is financial hardship, relationship issues and work deadlines.

Although stress may show up in our lives in different ways, there are two types of stress: acute and chronic.

Acute stress is short-lived, and might be triggered when you’re running late for work, if a dog barks at you unexpectedly, or even when you go for a run. Any type of stress that persists for a long period of time, like marriage problems, moving into a new home, or caring for a newborn baby could fall into the chronic category.

“Acute stress is a single exposure to stress that typically remits quickly and a person can typically meet the demands quickly and adjust,” says Dr Matthew Stults-Kolehmainen, Ph.D. in kinesiology and health education, ACSM-credentialed exercise physiologist, and adjunct associate professor at Columbia University.

Chronic stress, on the other hand, is long-term unremitting exposure to stress that has more harmful consequences. For example, it may lead to higher blood pressure or increased inflammation, which can weaken your immune system and make you more susceptible to colds, says Stults-Kolehmainen. It could also lead to mental health challenges.

How does your body regulate stress?
Regardless of the stressor, your body processes it the same way. “The body only has one stress response for all types of stressors and that’s true for the physical stresses of exercise, but also psychological stressors,” says Professor Jennifer Heisz,  associate professor and director of the NeuroFitLab at McMaster University and author of Move the Body, Heal the Mind.

This is why you experience similar symptoms of both physical and mental stress — increased heart rate, heavy breathing, and sweating when you exercise, just as you would when you feel excited, angry, or nervous during a tough conversation or situation.

The amygdala, which is located in the brain, sets off your stress response, triggering various organ systems to help you prepare for a threat. In some ways, it acts as a threat-detection centre for your body, constantly scanning the environment for possible threats, says Heisz. Once a potential threat is detected, the amygdala activates the hypothalamus (a part of the brain that produces hormones responsible for things heart rate and mood), which triggers the release of stress hormones, adrenaline and cortisol.

“The adrenaline helps to activate the body — increase heart rate, increase breathing rate — and cortisol helps to liberate stored energy from the liver and fat tissue. So the stress response was really designed to help us get away from danger,” explains Heisz.

Essentially, this is the activation of your sympathetic nervous system, also known as your “fight or flight” response. Once this is triggered, you might start to experience typical symptoms of stress like some of those mentioned by Heisz (sweating and muscle tension), among other side effects. Once the stressor is over, your parasympathetic nervous system (the “rest and digest” response) will take over and you start to feel a sense of calm or reprieve, Heisz explains.

Again, this is how the body reacts to all different types of stress in our lives, no matter how big or small of a threat, or even in circumstances where there’s no threat at all, like when you exercise.

How does stress affect exercise and vice versa?
“Acutely, stress can energise you, that’s the whole point of the fight or flight response,” says Stults-Kolehmainen. However, when you experience chronic stress, it can sometimes be debilitating to the point where you don’t want to do anything, he explains. Overall, your ability to manage stress will affect your energy levels.

However, there are some exceptions to the advantages of exercise for easing tension. For example, if you’re doing a new or complicated workout, mental stress can make it harder to concentrate, says Stults-Kolehmaimen. This is why it’s beneficial to stick with the workouts you know best when you’re already feeling overwhelmed.

On the flip side, stress can also mess with your exercise performance. Research suggests chronic stress can interfere with your motivation to move, and also your rate of perceived exertion (RPE), which is how hard you feel you’re working.

One study published in the International Journal of Sports Physiology and Performance suggests high levels of mental fatigue, which can stem from stress, can negatively affect RPE. To reach this conclusion, the two-part study examined the effects of mentally exhausting tasks on 16 men and women before both weightlifting and aerobic exercise. Researchers found that the workouts felt harder when the participants performed them after the demanding tasks, compared to when they didn’t have a mentally challenging task beforehand.

“Stress definitely impacts our perceptions,” says Stults-Kolehmaimen. It can lower your pain tolerance, for example, and make you feel like you’re exerting more energy, even if you’re doing something that doesn’t typically require that much. This may mean you’re unable to work out at the same level you once could because your energy systems are drained, he explains.

Also, research links chronic stress to chronic inflammation, making rest and recovery even more important to runners who face high stress levels. Too much inflammation has been linked to negative health outcomes, such as cardiovascular disease, metabolic disorders, and even musculoskeletal problems, says Lyle. That’s why you need to make sure you have enough rest after your workouts, and you pay attention to your mental stress levels before jumping into a bout of exercise, especially intense physical activity.

For runners who use their workouts as a way to cope, research suggests increased stress levels can lead you to exercise more, which can lead to injury if you don’t give your body enough downtime to deal with both the stress of your exercise regimen and your mental fatigue.

How can you measure and manage your stress levels?
There are a few different ways you can monitor your stress levels on a day-to-day basis.

One way that has become more well-known with the rise of fitness trackers: monitoring changes in heart rate variability (HRV), which is a measurement of the variations of time between each heartbeat. Overtime, this metric can be used to help you better understand your overall health, training readiness, and stress levels. Most experts would agree that HRV signifies how well your parasympathetic nervous system responds to stressors (that rest and digest state).

“Oftentimes, when you experience chronic stress, your parasympathetic nervous system never quite takes over,” says Lyle. Meaning your body never truly reaches a state of calm. The general concept is if you have a higher HRV, your body is better at managing stress, whereas a lower one can indicate the opposite, says Lyle.

This is why monitoring your HRV and RHR can be a good way to monitor your stress levels. Just avoid comparing these metrics to others, and instead monitor yours over time. If you notice declines in HRV, higher RHR, plus you’re not sleeping well, and you’re skipping workouts, then it can indicate something is wrong, says Stults-Kolehmaimen. That means it’s time to evaluate your lifestyle and see if there are areas in which you can pay more attention to stress levels and find outlets for relief.

Journaling is another way to monitor your stress levels. Lyle suggests using an app or writing down your stress symptoms, like headaches and digestive issues, to keep track of your tension and to make connections between what happened on days when stress spikes. This can help you recognize and then address those stressful factors and bring your body back to baseline.

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