More Evidence That a Little Bit of Exercise Goes a Long Way

Since the early 21st century, numerous studies have identified a correlation between aerobic exercise and a wide range of neuroprotective benefits associated with changes to the structure and functional connectivity of various brain regions. Most widely cited has been the link between regular aerobic exercise and the growth of new brain cells in the hippocampus stimulated by exercise-induced brain-derived neurotrophic factor (BDNF) — which some refer to as “Miracle-Gro” for the brain because it can boost gray matter volume like fertilizer. (For more see, "Aerobic Activity Stimulates Neurogenesis (Birth of New Neurons)") Physical exercise has also been found to improve the integrity of myelin-covered white matter tracts that facilitate high-speed communication within and between different brain regions.

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Despite mountains of evidence showing a link between physical activity and better brain function, there’s still a lot of uncertainty about the exact “dose-response” related to how much time people should spend being physically active in their daily lives. And nobody is certain about what intensity (easy, moderate, vigorous, or intense) of physical exercise is ideal for optimizing brain structure and functional connectivity across a lifespan. When it comes to prescribing daily and weekly amounts of physical activity, the "dose-response" topic is hotly debated among experts in the field.

Odds are, even if we did know the exact dose-response of physical exercise that would be ideal for every individual in the vacuum of a laboratory, it would be difficult for many to adhere to this prescriptive in the real world. For a wide range of very legitimate reasons, most of us are unable to robotically move our bodies day-in and day-out at the exact intensity and duration that might be prescribed by a physician or public health advocate.

That being said, in a perfect world, my hope would be that everybody reading this would have the time, energy, and stamina to exercise for at least 30 minutes most days of the week at a moderate-to-vigorous level of intensity with occasional bursts of high-intensity interval training (HIIT) incorporated into his or her aerobic workouts.

Obviously, we don’t live in a perfect world. But if you're like most people on the planet who are unable to exercise for 150 minutes per week (as recommended by the World Health Organization) for whatever reason, there is good news! The latest research shows that a single 10-minute bout of very light (30% of VO2 Max) physical activity can increase the connectivity between brain regions linked to memory formation and storage.

This potentially groundbreaking study on the cognitive benefits of short periods of mild exertion activity (such as gentle yoga, tai chi, slow dancing, or playing bocce) was conducted by researchers at the University of California, Irvine (UCI) and the University of Tsukuba in Japan. Their paper, “Rapid Stimulation of Human Dentate Gyrus Function with Acute Mild Exercise,” was published September 24 in Proceedings of the National Academy of Sciences (PNAS).

As mentioned in the introductory paragraph, previous research has focused on how aerobic exercise promotes the generation of new brain cells and white matter integrity in people who exercise regularly. What makes this study unique is that the researchers have demonstrated a more immediate impact related to the strengthening of communication lines between memory-focused parts of the brain after a single 10-minute bout of light activity that wasn't aerobic.

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For this study, the researchers recruited 36 healthy young adults and had them perform 10 minutes of very easy physical movements such as tai chi or gentle yoga. Immediately after the brief session of physical movement was completed, each person’s brain was scanned using high-resolution functional magnetic resonance imaging (fMRI). In comparison to a control group that hadn’t done any physical activity, those who had gently moved their bodies for 10 minutes prior to the brain scan showed better connectivity between the hippocampal dentate gyrus as well as cortical areas linked to detailed memory processing and storage.

Interestingly, the neuroscientists found that higher levels of functional connectivity between the hippocampus and surrounding brain regions predicted the degree of memory recall enhancement.

Based on these findings, the researchers conclude that a single 10-minute period of mild exertion physical activity can yield considerable cognitive benefits. "The hippocampus is critical for the creation of new memories; it's one of the first regions of the brain to deteriorate as we get older — and much more severely in Alzheimer's disease," co-author Michael Yassa of the UCI Brain Initiative said in a statement. "Improving the function of the hippocampus holds much promise for improving memory in everyday settings."

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Future research by Yassa and colleagues will investigate the long-term effects of regular mild exercise on age-related memory loss in older adults. Yassa concluded, "Clearly, there is tremendous value to understanding the exercise prescription that best works in the elderly so that we can make recommendations for staving off cognitive decline."