Is there a link between keeping fit and being smarter? Is it possible to increase our mental capacity and acuity by following a rigorous exercise plan? Well, if we're anything like laboratory mice, then high levels of physical exertion could make our brains significantly more agile and responsive.
Researchers at the National Cheng Kung University in Taiwan have found that allowing mice to run as often as they like improves their brainpower. If the mice are forced to run even harder than normal, their thought processes improve even further.
The study, which is due to go online in May 2010, took two groups of laboratory mice and had them swim through a water maze. In a separate trial, the mice were made to endure an unpleasant stimulus in order to determine how fast they would figure out how to avoid it. During the following four weeks, one group of mice were allowed to run in their wheels while the other group was made to run on mini-treadmills whose speed and duration were controlled by the researchers. The two groups were then tested again to determine their learning abilities and memory. Although both groups of mice were able to improve their ability to navigate the water maze, the treadmill mice performed better in the avoidance task, something that requires more cognition.
When analysed under the microscope, the brains of the mice who ran on the mini-treadmills showed evidence of changes at the molecular level in various areas. The wheel-runners on the other hand only showed changes in a single area of the brain. "Our results support the notion that different forms of exercise induce neuroplasticity changes in different brain regions," said Chauying J. Jen, professor of physiology at the University of Taiwan, one of the authors of the study.
A related discovery ten years ago by researchers at the Salk Institute in California found that exercise promotes the creation of new brain cells. The question remained though as to whether exercise had to be strenuous or aerobic in order to be beneficial to the brain and whether these improvements in brain function where temporary or permanent.
The University of Illinois conducted an experiment, which was published in the Journal of the American College of Sports Medicine, with 21 students who were asked to memorize a sequence of letters that they then had to pick out from a list that was flashed at them. The participants were then required for the next half hour to either sit quietly, lift weights, or run on a treadmill after which they tested again. The students then rested for an additional 30 minutes after which they were given the test again. The participants alternated activities on subsequent days, one day lifting weights, the next sitting quietly, and so on.
By the end of the experiment, it was noticed that those students who took to the treadmill were faster and more accurate on the retest than those who had taken either of the other two options and even after the rest period they performed better than the other groups. Charles Hillman, one of the authors of the study and associate professor in the department of kinesiology at the University of Illinois said, "There seems to be something different about aerobic exercise."
A similar study by researchers at the University of Illinois analyzed elderly subjects who were given a six-month exercise plan consisting of either stretching exercises or brisk walking. The subjects who were assigned to stretching did not show improvements in cognition tests whereas the subjects who were assigned to brisk walking showed measureable improvements.
According to Henriette van Praag, a researcher at the Laboratory of Neurosciences at the National Institute on Aging, "It appears that various growth factors must be carried from the periphery of the body into the brain to start a molecular cascade there," creating new neurons and brain connections. For that to happen, "you need a fairly dramatic change in blood flow." Aerobic exercises such as running, swimming, or cycling all trigger major changes in heart rate, pressure and flow. Even though weight lifting raises heart rate and pressure for short periods of time, unlike aerobic exercise it doesn't consistently maintain this high level over a significant period. Says van Praag, weight lifting stimulates production of "growth factors in the muscles that stay in the muscles and aren’t transported to the brain."
It is worth noting that not all of the mice in the Taiwan study showed improvements. Those mice that ran on their wheels showed little improvement in terms of fitness, muscle strength and better aerobic capacity. The reason for this may be that mice on running wheels don't really strain themselves as it is actually an enjoyable exercise for them. The mice that were placed on the mini-treadmills however were required to really push themselves and the intense workout promoted increased muscle strength and aerobic capacity. These improvements then were passed on to the brain.
Researchers caution against directly applying this to humans since human physiology does not work exactly like that of rats.. However, "it would be fair to say that any form of regular exercise should be able to maintain or even increase our brain functions" as long as it's aerobic, said Jen.