PUMPING IRONY: This Is Your Brain on Exercise?

I’m not one to obsess over the occasional malfunctioning of my septuagenarian brain. Stuff happens at this age — plaque accumulates, neurons misfire, cells misbehave — and I’m content to navigate as best I can amid the elusive memories and evasive words. I understand why people constantly strive to identify a cause and manufacture a cure, but why stress about something you can’t control?

Still, when evidence happens to emerge suggesting that we may have some influence over our cognitive capabilities as we grow old, it’s hard not to pay attention — even when the findings produce more confusion than clarity.

A trio of recent studies focusing on exercise and brain health challenges us to keep moving if we want to maintain some semblance of lucidity in our dotage, but the way researchers measure physical activity varies, as do the neural mechanisms by which that activity may promote cognitive function. The amount and intensity of exercise they recommend differs from study to study, as well. Indeed, one of the reports argues that the amount of exercise we do may not matter at all.

Researchers at the National Institute on Aging fired the first salvo back in January, arguing that cardiovascular fitness correlated with higher volumes of salutary white matter in the brain. They recruited 125 cognitively healthy participants between the ages of 22 and 94 and determined their fitness levels by measuring the maximum volume of oxygen the body can use at one time (VO₂ Max) while they ran on a treadmill. After scanning their brains with an MRI, researchers found a link between VO₂ Max and levels of myelin, a fatty sheath that protects nerve cells in the brain from toxins.

Maintain good cardio fitness, they note, and your brain will be insulated from harm. “This study provides evidence of an interconnection between cardiorespiratory fitness and cerebral myelination and suggests therapeutic strategies for promoting brain health and attenuating white-matter degeneration,” the authors write in Proceedings of the National Academy of Sciences.

Before you head for the gym and an all-out sprint on the first available treadmill, however, you might want to consider the findings of a more recent study that cautions against pushing yourself too hard when exercising for brain health. Reporting earlier this month in the journal Health Data Science, a Chinese research team asserts that it’s moderate physical activity that is most conducive to slowing the brain’s aging process.

For the study, Chenjie Xu, MD, and her colleagues analyzed health data from nearly 17,000 participants tracked in the UK Biobank. Researchers compared participants’ physical activity (PA) levels, measured by wrist-worn accelerometers during a seven-day period, with the relative volume of white matter in their brains. They concluded that both high and low levels of exercise intensity tended to hasten brain aging when compared with a more moderate regimen.

“Our study not only confirms a nonlinear relationship between objectively measured PA and brain aging in a large population but also provides actionable insight: More exercise isn’t always better — moderation is key,” notes Xu.

But the cognitive benefits that even moderate exercise may yield can be negated by too much sitting around, according to the results of a study published last month in the journal Alzheimer’s & Dementia. Researchers reviewed data on just over 400 seniors who had enrolled in the Vanderbilt Memory and Aging Project. The participants were free of cognitive dysfunction at the beginning of the seven-year monitoring project, and their levels of physical activity, as measured by accelerometer readings over a 10-day period, were described as moderate to vigorous.

But those accelerometers also tracked their leisure time, and those participants reporting the most sedentary behavior displayed faster hippocampal shrinkage (a precursor to dementia) and poorer results on cognitive tests than their less sedentary counterparts — regardless of how intensely they exercised. And these seniors were more vigorous than most: On average, they spent about an hour per day engaged in moderate-to-vigorous movement and spent about 13.5 hours relaxing (not including sleep time). As salutary as all that exercise may be, though, it’s the relaxing that caused the cognitive troubles, the study’s authors concluded.

“This finding suggests that mechanisms underlying the negative impacts of greater sedentary behavior may be operating independently of the mechanisms underlying the positive impacts of physical activity, and perhaps physical activity does not mitigate all the harmful effects of being sedentary,” they write.

Taken together, this latest round of studies leaves me wondering whether those brainy researchers maybe need to get out of the lab a little more often and get some exercise. Not too much, mind you. And not too little. Just enough to sharpen their already razor-sharp cognitive faculties. Also, limiting their couch time might be helpful.

Meanwhile, the rest of us will calmly await the scientific breakthroughs that are sure to follow.