Are you revising for exams? Or maybe following a course? Or do you usually work until deep in the night at your PC or at the drawing board to meet a deadline? Why not plan a short but intensive training session for times like these? According to physiologists at Texas Tech University, your brains function better after physical exertion.
A key factor in a well functioning brain is brain-derived neurotrophic factor, or BDNF for short [spatial formula shown below], a hormone that helps brain cells to make new connections with each other. In the 1990s neurologists discovered that lab animals produced more BDNF as a result of doing physical activity.
Since then neurologists, gerontologists and psychologists have been studying the effect of physical exercise on cognitive abilities. They discovered, for example, that the brains of people in their seventies who walk for more than half an hour each day are 'younger' than those of people who are not physically active; that intensive exercise reduces the risk of developing Parkinson's and that three sessions of cardio exercise per week results in growth of critical parts of the brains in the over-sixties.
The Texans wanted to know whether exercise also has directly observable positive effects on the brains of young people, so they devised an experiment with 15 healthy – but not super-fit – students. The researchers got the students to cycle twice for 20 minutes.
On one occasion the students cycled at moderate intensity: 20 percent below their ventilatory threshold [point at which they would start to pant] and at 56 percent of their maximal oxygen uptake [VTh-20%]. On the other occasion the students cycled more intensively: at 10 percent above their ventilatory threshold at 75 percent of their maximal oxygen uptake [VTh+10%].
Before and after the tests the researchers used the Strooptest to assess the students' cognitive abilities. This is a test that measures how good your brain is at dealing with information. The students performed equally well on the two easiest parts of the test after both sessions. But for the most difficult part of the test the students only performed better after the intensive exercise session, according to the figure below.
After the intensive exercise session the students had significantly higher levels of BDNF in their blood, but after the moderately intensive exercise session this was not the case. The more lactic acid the students produced, the higher the production of BDMF.
"It is tempting to speculate that repeated pulses of exercise-induced BDNF are key phenomena in the neurological and cognitive improvements that occur as a function of regular chronic exercise", the researchers write. "Future studies should examine the effect of chronic exercise training on the interplay between cardiovascular fitness, resting levels of BDNF, and cognitive function in human subjects."
Med Sci Sports Exerc. 2007 Apr;39(4):728-34.