09/10/2015 8:04 PM AEDT | Updated 15/07/2016 12:50 PM AEST

Exercise Can Dampen Stress Chemicals (And How To Motivate Yourself To Move)

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Sweaty, blond haired woman having a rest after hard workout on a sports field.

Exercise as a treatment for depression and anxiety has been steadily gaining support. Lena Dunham has preached that moving on a regular basis has calmed her obsessive thinking, and some doctors prescribe exercise in conjunction with medication to patients with depression.

But how does moving our bodies, upping our heart rate and breaking a good sweat actually dampen stress in our brain?

Neuroscientist Dr Zoltan Sarnyai, who focuses on the neurobiological mechanisms of stress and psychiatric disorders including depression, says exercise reduces the powerful stress chemicals-- cortisol and adrenalin -- in our brain.

Stress exists primarily in our body to protect us from danger.

"These chemicals increase our heartbeat, they increase delivery of blood (and with that more oxygen and nutrients) to vital organs (muscle, heart, brain) and more active energy metabolism to provide more fuel for cells under pressure,” Dr Sarnyai told The Huffington Post Australia.

When this happens other functions are suppressed to compensate.

“Such as defence against infection, reproductive functions and digestions as they are not absolutely necessary for the survival and they consume lots of energy, which the body wants to save under such circumstances,” he said.

It's important that these very powerful chemicals are switched off once a threat is over. “Otherwise they do damage to the body and the brain,” Dr Sarnyai said.

But in modern day life, our bodies and minds have begun to be inundated with chronic social stressors like work, deadlines, bills, and other social pressures.

"One of the overarching hypotheses of anxiety and depression is that stress plays a major role in their development,” Dr Sarnyai said.

Exercise, he explains, restores the shut-down of this stress response. When we go into survival mode at these everyday social triggers, we can avoid them going into harmful territory by moving our bodies.

Stress also threatens our brains in other ways, too. When cortisol is released it influences the function of our nerve cells allowing us to focus on the threat. Long term exposure to these powerful chemicals creates structural changes in our nerve cells and decrease production of new nerve cells in other areas of the brain.

While stress damages the growth and structure of our nerve cells, exercise promotes the growth of others. It helps to level us out.

Motivating Ourselves To Move

We know exercise is helpful, but people with symptoms of depression often find it difficult to motivate themselves to undertake routine tasks -- let alone working out.

Dr James Dimmock, psychology professor working across sports and health, says it depends on how you're motivated -- intrinsically or extrinsically.

If you’re intrinsically motivated that means you’re motivated by how exercise makes you feel; a likely reason people are happy to continue competing in social sports but refuse to go to the gym.

Dimmock explains extrinsic motivation as "doing something because you’re told to do it, you’ll get a reward if you do it or punished if you don’t do it".

But just because you don’t enjoy exercise, that doesn’t mean you can’t find a form of motivation that helps you stick to it.

"Adherence to exercise very much hinges on intrinsic motivation or not just intrinsic but positive extrinsic motivation," Dimmock told HuffPost Australia.

"You value exercise and the health benefit. Well that’s not intrinsic motivation because you still might not enjoy the activity but because you see it as important activity it’s still a good form of motivation. It’s extrinsic motivation because you’re doing the activity for contingency other than pleasure.

"One is not better than the other, one kind of motivation does not lead to another. You can have multiple motivations at the same time.”

So if you’re stressed, anxious or depressed, you can focus on the direct benefits exercise can have on your mood, and because you have internalised that benefit, you’re more likely to stick to regular workouts.

No easy task when you've likely already lost enjoyment in most everyday things. But with time, it is possible.

"What’s important is an overall sense of autonomy or volition we’re doing it because I personally enjoy it or I personally value the benefits or it’s personally important for my identity," Dimmock said.

"Those motivated where we’ve internalised the behaviour are much more preferable than those motivated where we feel we’re governed by external forces."

"It’s very much a self-regulation thing. You can actually choose to enjoy something if you want to. You may have to reframe certain tasks."

If you need help in a crisis, call Lifeline on 13 11 14. For further information about depression contact beyondBlue on 1300224636 or talk to your GP, local health professional or someone you trust.