In February 2016, researchers at the University of Jyvaskyla in Finland published results of a remarkable study on exercise they had just completed using laboratory rats. Their study showed that aerobic exercise such as jogging helped create new cells in adult rats' brains. This finding was remarkable because, not long ago, scientists believed that adult brains could not generate new cells.
Doctors have long known that physical exercise is good for the brain as well as the rest of the body. They were unsure, however, if specific exercises benefited the brain more than others, and if so, in what way. They could demonstrate that certain kinds of exercises aided cognitive ability by carrying out "before and after" tests, but were unclear about what was happening at the microscopic level of brain cells.
The scientists in Finland, in collaboration with scientists in other parts of the world, tested the effects of different types of exercise on rats' brains. They divided a large group of adult male rats into subgroups. Running wheels were placed in one subgroup's cages so that they could jog whenever they felt like it. These animals liked to jog, so no coercion was needed. Another subgroup did the equivalent of high-intensity training. They were placed on treadmills and induced to sprint for three minutes and allowed to relax for two minutes, after which the process was repeated. Three such sets were done in each test session.
The third subgroup did resistance training, in which they had to climb walls with small weights attached to their tails. A control subgroup did no exercise.
Before the tests began, the rats were injected with a substance that would mark any new brain cells. After seven weeks of testing, the scientists examined each rat's hippocampus under a microscope (the hippocampus is the area of the brain most involved in memory and learning). The scientists discovered that the number of neurons created in the hippocampi of the rats that exercised by jogging on running wheels doubled, or in some cases tripled, compared with rats that didn't exercise. Those that ran the longest distances overall generated the most new neurons.
The subgroup that performed the high-intensity training generated more neurons than the control group, but significantly fewer than the number generated by the running group. Those that did the resistance training became noticeably stronger, but did not generate any more new neurons than the control group.
Though the Finnish study is based on experiments with laboratory rats, it is significant for humans because most experts in this field of research believe that aerobic exercise has a similar effect on human brains. Their confidence is based on the knowledge that doing exercises like jogging regularly is particularly effective at stimulating the production of brain-derived neurotrophic factor (BDNF) in both humans and other mammals. BDNF is known to stimulate the production of neurons and synapses in the mammalian brain.
Medical and fitness experts have long known that aerobic exercises like jogging slowed age-related muscle loss and promoted cardiovascular health in humans and animals. With neurogenesis added to the benefits, humans now have at least three compelling reasons to don their shorts and head out for a 30-minute jog each day.