Brain Benefits from an hour of exercise per week

“Strenuous physical activity (e.g., exercise) is the most accessible, effective, pluripotent, and safe intervention to improve and maintain health, as well as treat most modern chronic diseases.” This quote is the enticing opening line to a recent review article from the Journal of Cerebral Blood Flow and Metabolism. The authors go on to explain several mechanisms by which exercise prevents physical and cognitive decline, especially pointing out its ability to ward off dementia in older age by improving cerebral perfusion and metabolism (brain gets more blood flow). Ultimately, the authors recognized that despite the miraculous curative potential of breaking a sweat, few of us bother to do so on a regular basis (or at all, if we can help it).

Based on survey data, the number-one impediment to exercising is a “lack of time”. Thus, the authors look to the potential of high-intensity interval training to replace traditionally longer workouts. High-intensity interval training is like sprinting up a hill and then walking down and repeating five times. The whole workout delivers similar metabolic benefits to a longer continuous workout but in a third of the time. It would seem that these scientists are on the verge of overcoming people’s time constraint to deliver maximum cerebral perfusion in an optimized, efficient workout. So what could be wrong with getting more bang for your buck?

The fatal flaw in the authors’ reasoning is that one can’t fix “lack of time” through increased efficiency, but only through modified priorities. Let me take a step back and explain the exercise parameters for this study: intensity, frequency, mode, and duration. The problem with prescribing high-intensity interval training based on these parameters is that we’re leaving out the parameter of “enjoyment.” How many people will prioritize sprinting up a hill for some abstract future benefit if they don’t enjoy it? Rather than finding the single most efficient exercise possible, individuals should find the physical activity that they enjoy enough to prioritize over sedentary entertainment. For some people this will mean sprinting up a hill, but for most it will be something more traditional and playful.

Trying to tailor exercise to maximize cerebral perfusion sounds good, but that is the equivalent of eating megadoses of synthetic vitamins rather than an actual vegetable. You end up with a lot of one thing that we know is good for health, but miss out on all of the more nuanced benefits of having a truly active lifestyle.


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