Studies in animals and humans have shown that physical activity generally increases brain volume and can reduce the number, and size, of age-related holes in the brain’s white and gray matter.
Exercise also augments adult neurogenesis. Neurogenesis is the creation of new brain cells in an already mature brain. In studies with animals, exercise, in the form of running wheels or treadmills, has been found to double or even triple the number of new neurons that appear afterward in the animals’ hippocampus, a key area of the brain for learning and memory, compared to the brains of animals that remain sedentary. Scientists believe that exercise has similar impacts on the human hippocampus.
This new study, published in the peer-reviewed Journal of Physiology, reported not once, but twice in the New York Times, found very different levels of neurogenesis, depending on how each animal had exercised.
Those rats that had jogged on wheels showed robust levels of neurogenesis. Their hippocampal tissue teemed with new neurons, far more than in the brains of the sedentary animals. The greater the distance that a runner had covered during the experiment, the more new cells its brain now contained.
There were far fewer new neurons in the brains of the animals that had completed high-intensity interval training. They showed somewhat higher amounts than in the sedentary animals but far less than in the distance runners.
And the weight-training rats, although they were much stronger at the end of the experiment than they had been at the start, showed no discernible augmentation of neurogenesis. Their hippocampal tissue looked just like that of the animals that had not exercised at all. The title of the scientists’ paper is, “Physical exercise increases adult hippocampal neurogenesis in male rats provided it is aerobic and sustained.”
Evidence tends to suggest that sustained aerobic exercise might be most beneficial for brain health also in humans, as appears to be the case in animals.
Just why distance running was so much more potent at promoting neurogenesis than the other workouts is not clear, although there is speculation among the authors that distance running stimulates the release of a particular substance in the brain known as brain-derived neurotrophic factor (“B.D.N.F.”) that is known to regulate neurogenesis. The more miles an animal runs, the more B.D.N.F. it produces.
These results do not mean, however, that only running and similar moderate endurance workouts strengthen the brain. Those activities do seem to prompt the most neurogenesis in the hippocampus. But weight training and high-intensity intervals probably lead to different types of changes elsewhere in the brain. They might, for instance, encourage the creation of additional blood vessels or new connections between brain cells or between different parts of the brain.
So if you currently weight train or exclusively work out with intense intervals, continue. But perhaps also build in an occasional run or bike ride for the sake of your hippocampal health. This “Long Slow Distance’ (or “LSD”) might not only improve your aerobic capacity and endurance, but it may also help with brain growth and neurological health.