We’ve known for a while that exercise is good for the brain. You’ve experienced this anecdotally plenty of times — recall your mental state during and after a recent workout session. The energy you had, the clarity you felt. It’s like you were awake and alert for the first time all day.
Unfortunately, the flip side is also true. Remember the grogginess you endured following a period of prolonged lethargy, say after Sunday’s Netflix binge? Energy and motivation were nowhere to be found.
Why does our mental state vary drastically depending on our physical activity, or lack thereof? What are the mechanisms at play?
Brain chemistry improves
When engaging in aerobic or anaerobic exercise, oxygenated blood flow to the brain increases, stimulating a region known as the dentate gyrus to produce a protein called brain-derived neurotrophic factor, or BDNF.
BDNF is basically fertilizer for your neurons, electrically excitable brain cells that process and transmit information throughout the nervous system. Neurons are the fundamental units of the brain, responsible for receiving sensory input from the external world, sending motor commands to our muscles, and relaying the electrical signals at every step in between.
BDNF works to keep neurons healthy and elastic, while facilitating proper neuron to neuron connection. BDNF also encourages neurogenesis, the formation of new neurons in the brain.
In addition, exercise jumpstarts production of a powerful molecule known as Irisin, which helps to activate genes associated with memory and learning, along with other neuro-protective effects.
Through experiments conducted on mice, investigators led by Dr. Bruce Spiegelman of the Dana-Farber Cancer Institute and Harvard Medical School found that irisin levels become elevated in the brain through endurance exercise.
The science is in — through a series of complex processes, exercise kicks off a chain reaction that drastically improves brain function.
So then: What does all this actually mean for us?
Focus sharpens
Renowned neuropsychiatrist Dr. John Ratey surmises that exercise promotes a plethora of cognitive improvements, most notably mental clarity and focus, for as long as three to four hours post-workout. In other words, get an exercise session in before your big work presentation or speaking engagement.
Long term, this helps stave off degenerative diseases like Alzheimer’s and Dementia. Due to increased blood flow and elevated levels of BDNF and Irisin, the ability of the brain to improve and recover (just a like a muscle) improves.
Memory improves
Your brain remembers more during activity due to stimulation of the dentate gyrus, which we touched on above. The dentate gyrus region resides in the hippocampus, the area of the brain most responsible for short-term memory.
In an experiment published by the journal of the American College of Sports Medicine, students were asked to memorize a string of letters, and were then allowed to run, lift weights, or sit quietly. The students who ran were quicker and more accurate when they were tested than students who chose the other two options.
Preparing for a big exam? Cramming sales figures and talking points for the board meeting tomorrow? Get a workout in. It may make the difference.
One caveat: don’t overdo it
There is a limit to the amount of BDNF and Irisin we can produce. In fact, with too much exercise, we can do more harm than good. Justin Rhodes, Ph.D, a neuroscientist at Oregon Health and Science University found that mice who ran all day and night actually began to fail at their task, which in this experiment was navigating a maze. The mice became oversaturated, overtired, and thus unable to complete a task they were able to complete earlier in the experiment.
His research discovered that the best performing mice tended to run two or three miles at a time — similar to how it seems best for humans to manage small to medium spurts of exercise in favor of drawn-out workout sessions.
This is one major reason why High Intensity Interval Training, a training protocol that focuses on intense bursts of activity interspersed with regular rest periods, has become so popular.
The jury is out, people. Exercise has just as many positive cognitive effects as physical effects.
Be safe, be strong, be well.
Scott Mayer is a runner, thinker, curious observer and certified personal trainer.
Photo courtesy of Unsplash