There’s been a lot of good science that establishes the cognitive benefits of exercise. In the New York Times, Gretchen Reynolds reports on a new study that finds that “Brain Benefits of Exercise Diminish After Short Rest.”

This study asks, okay, so what happens when people stop exercising? Do the physiological benefits that exercise provides the brain diminish? And is there a measurable difference in performance on tests of cognitive function? In this study, the researchers went to a local running club, and recruited 50-80 year-olds who had been running regularly for at least fifteen years.

At the start of the experiment, the runners visited the researchers’ lab for tests of their cognitive skills. They also had a special brain M.R.I. that tracks how much blood is flowing to various parts of the brain.

The researchers were particularly interested in blood flow to the hippocampus, a portion of the brain that is essential for memory function.

Then the athletes sat around for 10 days. They did not run or otherwise exercise and were asked to engage in as little physical activity as possible….

After 10 days of being sedentary, the erstwhile runners returned to the lab to repeat the earlier tests, including the M.R.I. scan of their brains.

The results showed striking changes in blood flow now. Much less blood streamed to most of the areas in the runners’ brains, and the flow declined significantly to both the left and right lobes of the hippocampus.

The good news, though, is that “the volunteers did not perform noticeably worse now on the tests of cognitive function than they had at the start.” So taking a break from running 35 miles a week is not going to cause a “Flowers for Algernon“-type event.

Here’s the abstract from the original article:

While endurance exercise training improves cerebrovascular health and has neurotrophic effects within the hippocampus, the effects of stopping this exercise on the brain remain unclear. Our aim was to measure the effects of 10 days of detraining on resting cerebral blood flow (rCBF) in gray matter and the hippocampus in healthy and physically fit older adults. We hypothesized that rCBF would decrease in the hippocampus after a 10-day cessation of exercise training. Twelve master athletes, defined as older adults (age ≥ 50 years) with long-term endurance training histories (≥15 years), were recruited from local running clubs. After screening, eligible participants were asked to cease all training and vigorous physical activity for 10 consecutive days. Before and immediately after the exercise cessation period, rCBF was measured with perfusion-weighted MRI. A voxel-wise analysis was used in gray matter, and the hippocampus was selected a priori as a structurally defined region of interest (ROI), to detect rCBF changes over time. Resting CBF significantly decreased in eight gray matter brain regions. These regions included: (L) inferior temporal gyrus, fusiform gyrus, inferior parietal lobule, (R) cerebellar tonsil, lingual gyrus, precuneus, and bilateral cerebellum (FWE p < 0.05). Additionally, rCBF within the left and right hippocampus significantly decreased after 10 days of no exercise training. These findings suggest that the cerebrovascular system, including the regulation of resting hippocampal blood flow, is responsive to short-term decreases in exercise training among master athletes. Cessation of exercise training among physically fit individuals may provide a novel method to assess the effects of acute exercise and exercise training on brain function in older adults.

I think I’ll get off the laptop and go to the gym now.