How exercise calms stress

According to a study performed at Princeton University in 2013, the calming effect of exercise is in the firing of the neurons within the ventral hippocampus which is known to control anxiety.  In this study done with mice, they found there are 2 types of neurons at work here along with an amino acid.  The neuron discovery starts with the firing of brand new, very excitable (meaning they fire often), baby (newly created) neurons which get stimulated at the drop of a hat . . . . any hat.  As they mature, they become less excitable.  The other neuron, in this battle of stress, is what scientists call “Inhibitor Neurons”.  When the inhibitor neurons fire they calm the effect of the new, baby neurons.  The amino acid involved in the study with these neurons is the neurotransmitter gamma-aminobutyric acid (GABA), which has a calming effect on firing neurons.  During stress, the new baby neurons are easily excited, then inhibitor neurons fire to calm the excitement of the babies and GABA is produced to further the calming process.

In the study, there were 2 groups of mice; one group was put into a brightly lit room for many hours through the day and given some open areas in which to roam, some hiding corners in which they could choose to sleep and a wheel with which they could exercise at their leisure.  The second group was given a similar set up but were kept in a dark room most of the time with no exercise wheel.  Both groups were found to have created the same number of new, baby neurons during the time of the study and have the same amount of GABA, the inhibitor neurons.

The group with no exercise soon exhibited introverted behavior, hiding in their corners much of the day. In these mice the baby neurons became very excited with stressors, the inhibitor neurons did not fire much, and the mouse produced less GABA.  And so, these baby neurons also stayed excited, keeping the mice stressed long after the stressors were removed because there was no way to calm them down.

The group with the option of exercise stayed in their open areas much of the day, indicating more confidence.  The interesting part is that when these mice were introduced to the same stressor (a bath of cold water) their baby neurons became less excited (firing less often) than the non-exercise group, their inhibitor neurons became much more excited than in the sedentary group, and the mouse produced more GABA which also kept the animal calm.  So the exercising mice were found to panic less, and they recovered from the stress much more quickly.

Then the researchers did some further testing.  Using chemical bicuculine, which is used in medical research to block GABA receptors, they were able to artificially block the effects of GABA in the active mice.  This proved that the active mice would become more agitated and the mice handled stress less well.

So the next time you are stressed at work, or fed-up at home, let everyone know you are going for a long walk.  By the time you get back you will feel much better, and may even have answer that eluded you before.