Legs of a young man runningIntroduction:
Regular exercise exerts a powerfully positive effect on mood. Tensions, depressions, feelings of inadequacy, and worries diminish greatly with regular exercise. Exercise alone has been demonstrated to have a tremendous impact on improving mood and the ability to handle stressful life situations.  Simply stated, people who participate in regular exercise have higher self-esteem and are happier.

Background Data:
Numerous studies have documented the stress busting effects of regular exercise. These studies have shown that participation in exercise, sports, and physical activities is strongly associated with decreased symptoms of anxiety (restlessness, tension, etc.), depression (feelings that life is not worthwhile, low spirits, etc.), and malaise (rundown feeling, insomnia, etc.).

Regular exercise has been shown to increase powerful mood elevating substances in the brain known as endorphins. These compounds exert similar effects to morphine, although much milder. In fact, their name (endo = endogenous, -rphins = morphines) was given to them because of their morphine-like effects. There is a clear association between exercise and endorphin elevation, and when endorphins go up, mood follows.

New Data:
Physical exercise is known to reduce anxiety. Researchers at Princeton University recently discovered  another mechanism responsible for this effect. They examined the effects of exercise on the ventral hippocampus – an area of the brain that has been linked to anxiety regulation.

For some time, scientists studying exercise have been puzzled by physical activity’s two seemingly incompatible effects on the brain. On the one hand, exercise is known to prompt the creation of new and very excitable brain cells. At the same time, exercise can induce an overall pattern of calm in certain parts of the brain.

The researchers also took adult mice and injected them with a substance that marks newborn cells in the brain and for six weeks allowed half of them to run at will on little wheels, while the other mice sat quietly in their cages.

Afterward, the scientists determined each group’s baseline nervousness. When the mice were given access to cages with open, well-lighted areas, as well as shadowy corners, the running mice were more willing to cautiously explore and spend time in open areas compared to the sedentary mice. Exploring and spending more time in open areas is an indication that the physically fit mice were more confident and less anxious than the sedentary animals.

The researchers also checked the brains of some of the runners and the sedentary mice to determine how many and what varieties of new brain cells they contained. As expected, the runners’ brains contained more new new and excitable neurons brain cells. They also contained greater number of new neurons specifically designed to release the neurotransmitter GABA, which promotes feelings of calmness with greater mental focus and clarity.

They next looked at the effects of stress (a cold water swim) on the hippocampus of sedentary and runner mice and found that while stress increases expression of the protein products linked to anxiety in sedentary mice, it has no such effect in runners.

They further showed that running produced local mechanisms in the hippocampus that can block feelings of anxiety.

The bottom line from all of this research is that it indicates that the center of the brain that controls feelings of anxiety is vastly different in physically active animals compared to sedentary animals. Presumably the same is true for humans as well given the clinical effects of physical activity in relieving feelings of anxiety.

Schoenfeld TJ, Rada P, Pieruzzini PR, Hsueh B, Gould E. Physical exercise prevents stress-induced activation of granule neurons and enhances local inhibitory mechanisms in the dentate gyrus. J Neurosci. 2013 May 1;33(18):7770-7.

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