Exercise is good for your physical health. We have known this for a long time. We also know that physical activity is good for the brain and alleviates depression and stress.
What’s more, training improves both memory and learning capacities. On the other hand, exaggerated exercise, when the body doesn’t have a chance to recover, has a negative effect, with fewer brain cells as a result. This is shown in a dissertation from the Sahlgrenska Academy at Göteborg University in Sweden. Moderation is best, in other words.
Biologist Andrew Naylor arrived at this by studying rats running in a treadmill. Rats that were allowed to run the treadmill for nine days acquired five times as many new stem cells in the part of the brain called the hippocampus compared with rats in a control group that did not run at all. Four weeks after their training, that is four weeks after the treadmill had been removed from the cage, about a third of the new cells were still there and had developed into functioning nerve cells.
The hippocampus is a part of the brain that is important for the regulation of stress reactions, but also for memory and learning. Andrew Naylor could confirm that these rats actually were better learners after their exercise by a running memory and learning test on them. The test had the rats swim in a round basin that had one place where they could get up out of the pool. The rats that had exercised learned more quickly than those who hadn’t where they should swim to get up out of the water.
A third group of rats were allowed to run on the treadmill as much as they wanted for 24 days. For some reason these rats increased their amount of running from six kilometers a day to as much as 20 km a day.
“Just why these rats ran more and more, I can’t say, but they seem to like it. Maybe they develop an addiction of some sort. I plan to study this in the future,” says Andrew Naylor. But even if the rats run a lot because they like it, this had no positive impact on the number of cells in the brain. On the contrary, they developed only half as many new cells in the hippocampus as the ones that didn’t exercise at all.
“What’s interesting is that if the over-exercising rats were left to rest for a few weeks, more than half of their newly-formed cells survived, which is more than twice as many as in rats who didn’t exercise. But since there were fewer new cells from the beginning in the over-exercised rats, the ultimate result was largely the same number of cells in both groups anyway. In other words, the brain seems to find a way to compensate for the fact that fewer cells are formed when rats run too much.”