Your Brain On Exercise: Rewarded With Testosterone and New Neurons

3d rendered illustration - hippocampus

Hippocampus (yellow) deep in the brain

More proof that exercise is good for your brain as well as your body. Recent Japanese research shows that exercise such as jogging floods your brain with testosterone and spurs growth in specific memory areas, the important hippocampus region.

Exercise is little less than a magic elixir for our health. It is not quite magic, though, in that we still have to earn these health rewards by actively exercising our bodies. When we do exercise by moving our bodies under our own power, especially moving them quickly so we breathe hard and start to sweat, astounding benefits take place in our bodies and brains.

A very long list of health benefits of exercise need not be repeated here. Most of the lifestyle related maladies most that strike down people in modern society stem, in good part, from insufficient exercise. Cardiovascular and strength exercises provide preventative, curative and restorative solutions to many of our modern health maladies.  All that and they make you strong and feel great too!

The Japanese research would indicate that as least part of the elation often felt during and after exercise may be explained by the increases in testosterone in the brain. Testosterone is called the “male hormone” and indeed it is associated with the gonads (and elsewhere) and occurs at levels around eight times higher in male than female animals, including humans. But all people produce testosterone. Not unlike the runner’s high, which has been associated with endorphins and endocannabinoids produced during exercise, testosterone provides an energized, pleasant feeling. All these enjoyable effects associated with exercise may provide evolutionary benefit, that is, rewarding physical activity that might help feed the family by encouraging hunting or other survival activity.

More than just feeling good, though, this new research shows that the dihydrotestosterone (DHT) produced causes actual new brain cell growth in the area we need it most, the hippocampus, deep down in our brains. This vital area is associated with memory and benefits greatly from new neurons coming on-line. A hippocampus refreshed by these new neurons can help retain memory, promote new learning, protect from depression, and generally help the brain operate more efficiently. DHT, earned through exercise, is necessary for this rejuvenating neurogenesis.

Do yourself and your brain a favor. Walk a lot, at least 10,000 steps a day. Try to raise your heart rate and break into a sweat for at least a few minutes each day.

Proc Natl Acad Sci U S A. 2012 Aug 7;109(32):13100-5. doi: 10.1073/pnas.1210023109. Epub 2012 Jul 17.

Mild exercise increases dihydrotestosterone in hippocampus providing evidence for androgenic mediation of neurogenesis.

Your brain on exercise: rewarded with dopamine by cannabinoid receptors.

Lack of enough physical activity is a huge problem in the obesity-plagued modern world. With much of physical activity removed from work and daily life, to be fit and not obese, we have to exercise for extended periods of time, in activities like jogging, fast walking, bike riding and other aerobic exercise. Our willingness to exercise in this way is really a cornerstone of our health, and our society’s health. Probably more than anything single factor, our health care system would benefit from people getting more exercise. New research now reports the crucial role of cannabinoid receptors and our endocannabinoid regulatory system in our motivation to keep moving.

Research out of France, reported in Biological Psychiatry shows how small protein cannabinoid receptors operating in the walls of nerve cells in the  brain reward exercise. This unlocks a key to voluntary exercise, and perhaps ways to promote it.  Also reported in ScienceDaily, the research reported that the endocannabinoid system, especially CB1 receptors in certain parts of the brain, reward our bodies and minds with pleasurable sensations. This research was with mice, not humans, but the physiology and responses are very similar. Lack (or blockage) of these receptors caused a sharp drop in the amount of exercise control mice were willing to do.

For us to continue to exercise, rather than stopping, depends a lot on how we feel. If tired and uncomfortable we might well stop; if exhilarated and “in the zone,” we continue. How we feel during exercise, it turns out, depends much on how much of the feel-good substance, dopamine, our brains produce and receive.  Our dopamine levels, this research shows, are controlled in part by our endocannabinoid systems and CB1 receptors in certain parts of the brain. CB1 receptors are activated by our natural endocannabinoids such as anandamide. They also fit like lock and key and are activated by plant cannabinoids, especially THC, from cannabis.

Dopamine is an organic chemical produced in several areas of the brain. Many brain functions involve dopamine, especially learning, voluntary movement, reward and motivation. We feel higher dopamine levels as enjoyment and are rewarded by the experience, making us want to continue or repeat. Drugs like cocaine increase and prolong dopamine levels. The Bordeaux, France researchers studied dopamine producing nerve cells in the brain’s ventral tegmental area (VTA) known to play an important role in motivation. By working with mice with CB1 receptors present or absent or blocked, they found marked difference in how much running wheel time the rodents would spend.

The researchers had previously found “that the endogenous stimulation of cannabinoid type-1 (CB1) receptors is a prerequisite for voluntary running in mice,” but did not understand the mechanisms. In experiments involving “in vivo electrophysiology, the consequences of wheel running on VTA dopamine (DA) neuronal activity” on mice with combinations of CB1 blockage and GABA blockage. GABA is an inhibitory neurotransmitter that reduces levels of dopamine produced by other neurons. Cannabinoid receptor activation in GABA neurons inhibits this inhibitory effect on dopamine. This “inhibition of inhibition” results in an increased level of dopamine produced in this motivation area of the brain.

Exercise promotes endocannabinoid activation of CB1 receptors and this activation encourages continued exercise. If we exercise enough to allow them, our bodies reward us for the physical activities that are so good for us.

Not mentioned in this research, the “runner’s high” is likely a function of endocannabinoids, along with the endorphins. For earlier evidence of the runner’s high association with the endocannabinoid system check Runner’s high – your body rewarding exercise.

Running speed and prevention of cardiovascular disease.

Running speed a great indicator of health.

Running speed a great indicator of health.

The key role of cardiovascular exercise in keeping healthy and hearty has been confirmed in a couple of important studies. They point out the amount of time it takes you to run a mile is a great indicator of cardiovascular health and your danger of heart attack and stroke.

Reported in Red Orbit and elsewhere, two studies of this behavioral indicator of cardiovascular health, showed that for middle-aged men, the length of time required to run one mile (1,609 meters) predicted heart attack and stroke better than did blood pressure or cholesterol levels.

Faster times predict fewer heart and brain attacks. A 55 year old male who requires 15 minutes to walk/run a mile (only 4 miles per hour) faces a 30% chance of suffering cardiovascular disease. A man of the same age who can run a mile in just 8 minutes (7.5 miles per hour) faces far lower danger of cardiovascular disease, less than 10 percent.

One way to increase running speed is with interval training, brief bursts at higher speed. After warm up jogging, a common interval is one minute slow jogging speed followed by one minute high intensity running, then repeating the sequence up to 10 times. This writer has been experimenting with slow jog/fast walk for 90 seconds, interspersed with 30 seconds high speed. This rhythm seems well suited for a non-punishing work-out made plenty intense with the periods at high speed. These high speed intervals quickly boost heart rate and sweating, both goals of a good conditioning, fat-burning workout.

High levels of physical activity such as running seem to correspond with activation of the endocannabinoid regulatory system, the receptor based system also activated by the THC in cannabis. Indeed, the fabled “runner’s high” might be the result of this system, rather than (or in addition to) to endorphins. More about this in a future post.

Caution: For those poorly conditioned, increasing activity and especially trying to push up maximum speed can present some dangers. A consultation with your (fit) medical practitioner and taking a stress EKG test is a good precaution.

Caution: Being poorly conditioned and not participating in physical activity presents an enormous risk of cardiovascular disease, along with obesity, diabetes and a host of other diseases.