Exercise can elevate mood. Sometimes in just two or three minutes. The research confirms this – and that exercise is an effective treatment for symptoms of anxiety and depression. On par with therapy and/or medication. But what's the mechanism? I'll share some research in a second but I want to give you a moment to think about how you'd answer this question. What’s your theory?
The practical part of me that thinks about personal training is less worried about why something works – just that it does work. However, the closer we get to first-principle thinking, the better we can build and test our own theories. Some researchers obviously agree, so they reviewed 32 articles covering more than 1,800 people with depressive symptoms. They looked at markers of stress, brain nourishment, inflammation, and VO₂ max, among other things. They also compared more conventional exercise with mind-body exercise, like Iyengar yoga and tai chi (well, T’ai Chi Chih®). One note and/or caveat here is that anything can be mind-body exercise; it’s more about how you do things.
Stress Hormone Regulation (Cortisol)
Cortisol buffers inflammation and increases energy-flow to organs. It actually does lots of helpful stuff, so I don’t like it when people talk about cortisol like it’s the enemy. Cortisol is our friend – and more like stress’s shadow or favourite hat. So, when you see stress or depression, you’ll probably see cortisol. Did exercise generally lower markers of stress? It sure did.
Brain Growth and Plasticity (BDNF)
Exercise often increased BDNF, a protein that supports the growth and survival of neurons in the brain. This might be one way exercise helps the brain “rewire” itself and into new ways of doing things. This is supported by stronger results via mind-body exercises, as opposed to literally going through the motions. If I had to theorize? Among other things, challenging coordination and disrupting default movement strategies drives up nourishment for the ole brain-space. From there, practicing new skills under stress becomes easier and more likely to stick via structural remodelling of the brain. It’s tough to look at brain-building AKA neurogenesis directly but the limited data they had (biochemical markers and brain scans) backed this up.
Inflammation Reduction
Mind-body exercises consistently lowered IL-6, an inflammatory marker associated with depression. Physical exercise (mostly running, some strength) results were mixed. I don’t want to get too nitpicky here but a lot of exercisers haven't mastered how to manage exercise volume and intensity. That stuff takes time. We've been teaching people to do just this for years – here in Toronto – and it's a skill that people don't always pick up automatically. It takes time. Working with a personal trainer, experienced exercise partner, or tracking your sense of exertion and subsequent fatigue can all help.
Better Fitness, Better Mood
Physical exercise reliably improved VO₂max (a good general indicator of cardiovascular fitness), and some studies found this improvement was linked to reduced depressive symptoms. That came down to the changes in brain volume (as mentioned above). It’s also mentioning that bringing aerobic function up from low to (at least) will improve your ability to recover from minor stressors.
TL;DR:
Exercise is deeply integrated process that literally changes your biology - including the structure of your brain.
What I imagine when I read the word, "neurotropic."
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