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Stressed Out? The Simple Science Behind Stress

Stressed Out? The Simple Science Behind Stress


Stress that is left unchecked can lead to a wide range of mental and physical health problems. We all know stress can contribute to high blood pressure, cardiovascular disease, and headaches, but did you know that stress has also been linked to diabetes, and some studies even suggest a possible link to cancer? Let’s take a brief look at some of the science behind stress. Next month we’ll look at how we can change our body’s response to stress via physical activity.

What is Stress Anyway?
In a nutshell, stress is a physical, mental, or emotional reaction to change. This often occurs when we believe a situation is “too much” and is endangering our well-being. At the heart of all stress is the feeling of a loss of personal control – even if the change is a positive one.

Stress contributes to illness by causing our mind and body to become exhausted, worn down, and damaged; by weakening immunity; and by motivating unhealthy behaviors to deal with the stress (while also inhibiting healthy behaviors). Inflammatory hormones are released when we are stressed. This increases the risk of disease, among other issues.

What’s Behind this Stress?
Have you ever stopped to consider what’s actually going on in your body when stressed? Even if science isn’t your thing, you may find the physiology of stress fascinating. And understanding what’s going on inside your body may help motivate you to take steps to reduce your stress.

Our natural reaction to stress is to run away/avoid (flight), confront (fight), or play dead (freeze). In the flight or fight mode, you may feel like you have superhuman survival powers. This is because adrenaline is released, which:

  • elevates heart rate and blood pressure (to provide more blood to muscles)
  • constricts the blood vessels of the skin (to limit bleeding if wounded)
  • dilates the pupil of the eye (to let in more light, thereby improving vision)
  • increases activity in the reticular formation of the brain (to increase the alert, aroused state)
  • liberates glucose and free fatty acids from body storage sites (to make energy available to the muscles, brain, and other tissues and organs)
  • activates certain immune cells to prepare to defend the body if wounded

The freeze response is also a survival response to a stressor, but involves the conservation of energy and immobilization designed to lessen the impact caused by the stressor. Physiologically, this involves:

  • loss of skeletal muscle tone (to create disinterest in a predator or to maintain blood flow to the brain if wounded)
  • a drop in blood pressure (to reduce blood loss from wounds)
  • tightening of the larynx (to inhibit vocalization)

Each of the flight-fight-freeze responses can be productive or counterproductive. Running from fire? Productive. Running from a deadline? Not so much.

A lesser known response to stress is activation of our HPA axis (hypothalamic pituitary adrenal axis), which is our central stress response system. In an immediate (acute) response to stress, cortisol – the primary stress hormone – is released by the adrenal glands. Cortisol increases levels of glucose in the bloodstream, enhances the brain’s use of glucose, and increases the availability of substances that repair tissues. This is a healthy and essential response to a stressor.

But here’s the thing. The flight-fight-freeze response and activation of the HPA axis are designed for short-term (minutes to hours) management of a stressful situation. This is healthy. When interaction with the stressor is prolonged, we enter the extended (chronic) phase of stress. This is not healthy. As a matter of fact, in this phase, the elevated level of cortisol alters metabolism (contributing to overweight and Type 2 diabetes), suppresses the immune system (increasing susceptibility to infections and disease), weakens bones, impairs memory, and can worsen depression. At this point, the person often becomes ill and exhausted.

There is sometimes a delay between when the stressful event or period occurs and when the body’s resistance is fully exhausted and the illness appears. This is why the effects of stress are sometimes not fully experienced until after the stressful period has passed. You recall times when you made it through a stressful situation only to fall sick days later? That’s the effect of chronic stress.

With all that we know about stress, shouldn’t we prioritize stress relief – or even stress prevention – a little more? I think so. Next month, we’ll discuss some steps you can take to reduce your stress. In the meantime, consider what your current stress level is like, and how you tend to respond to stressful events. There are several online inventories that may help. Until next month, deep breaths!

Alison Jones is a group fitness instructor at Merritt Clubs Eldersburg, a certified personal trainer, and a certified health and wellness coach. Alison will be helping lead the 12 Weeks to Wellness program at Merritt Eldersburg beginning February 2, 2020.