I find that being involved in fitness training, and in writing and speaking about those activities, is very stimulating for my brain. Along those lines, some extremely interesting data, and an associated article, have caught my attention. Earlier this month, a study was published in the Journal of Physiology, and a subsequent article was written in the New York Times, about the effect of distance running on hippocampal neurogenesis in rats.
In summary, the hippocampus is the part of the mammalian brain that is integral to learning and memory. Neurogenesis is the formation of new neurons, essentially the production of more cells. The study found that hippocampal neurogenesis was significantly increased in rats performing what would generally be considered low-level endurance running. A small increase was seen in rats doing a form of high-intensity interval training, and virtually no change was measured in a weight-training group, as well as a sedentary control group.
A possible reason for this result, while not referenced in the article, is the increased oxygenation that occurs in the aerobic exercise condition the distance running rats performed. There have been multiple studies showing this increase in brain O2 during and following aerobic exercise, and I presume that this is at least partially related to the neurogenesis mentioned above.
Back in the decade known as the (glorious and wonderful – but aren’t they all?) 80’s, I sort of stumbled upon this principle. It was a time period when I was in graduate school and was also competing in triathlons. My classmate, good friend, and training partner, Chris Culligan, and I came up with a system that allowed us to get some of our easier training miles in while combining the enjoyment of fellowship with the opportunity to study our class material. What we did was go out on some very easy submaximal runs (about 65% of max heart rate for effort) and carry a few index cards with key class notes on them. Remember, it was the 80’s and although the Walkman existed, the note card was adequate for our needs. We would just run along and discuss key bits of the material we needed to learn and would be tested upon. What we both found was that those “study” sessions were easy, fun, and highly effective. Our test scores and retention of the material that we studied under “movement learning” were consistently high. These days, I often find myself out on walks when my best ideas occur, and I’ve taken up the habit of carrying a small digital recorder (size of a pack of gum) that I can use to capture these inspirations.
But since this is my blog, I guess I’m allowed to pontificate a little. If you can stand it, just stay with me for a few sentences. Because we live in America, and the health, fitness, and nutrition industries are the most sensational, marketing-heavy, fad-driven businesses in existence, I want to offer up a few opportunities for introspection. First, there will be people who want to justify their way of training as superior and will say “See, you should run marathons and it’s better than everything else”. Or, well-intentioned enthusiasts will immediately take up a 10k training program and promptly exhaust or injure themselves. Whoa! Relax! Those rats in the study were not forced to run. They were given wheels and they self-selected to jog moderately for a few miles most days. That is practically an ideal “training” behavior.
The NYT article also suggested that while this particular study did not identify the potential benefits of high-intensity interval or weight training, the author did indicate that such training probably produces other benefits which were not identified in this specific study. I’ll jump in here with a bit of conjecture. Interval and strength training typically require high-force, coordination-intensive movements. My educated guess is that probably causes either hypertrophy (cell growth), or an increase in synaptic efficiency in the motor cortex of the brain. There is some data to support this thought but the definitive study has perhaps not yet been completed. This is the area where the brain recruits the specific muscle fibers needed to perform activity (how fast, how far, how much, etc.) and it’s certainly plausible that lifting, sprinting, and jumping enhance this control center. The challenge here is that I neither have the time nor the resources (probably can’t convince NIH to fund me and then get a bunch of athletes to submit to lobotomies) to test this scientifically. But maybe that’s the next article we’ll see!