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Study Suggests Light Exercise Helps Memory

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Fitness group doing tai chi in park

Credit: iStock/Wavebreakmedia

How much exercise does it take to boost your memory skills? Possibly a lot less than you’d think, according to the results of a new study that examined the impact of light exercise on memory.

In their study of 36 healthy young adults, researchers found surprisingly immediate improvements in memory after just 10 minutes of low-intensity pedaling on a stationary bike [1]. Further testing by the international research team reported that the quick, light workout—which they liken in intensity to a short yoga or tai chi session—was associated with heightened activity in the brain’s hippocampus. That’s noteworthy because the hippocampus is known for its involvement in remembering facts and events.

Brain scans of the participants after the light exercise also revealed stronger connections between the hippocampus and cerebral cortex, which plays an important role in detailed memory processing. What’s more, the level of heightened connectivity in a person’s brain after exercise predicted the degree of their memory improvement.

These results come from the labs of Michael Yassa, University of California, Irvine, and Hideaki Soya, University of Tsukuba, Japan. Soya’s team had conducted earlier studies in rodents that found increased activity in the hippocampus and improved performance on tests of spatial memory after a light-intensity run on a controlled treadmill [2]. Intriguingly, more intense exercise didn’t offer the same memory boost.

In the new study, partly funded by NIH and published in Proceedings of the National Academy of Sciences, the researchers extended those earlier findings to people. They did it by coupling very light intensity exercise with computerized memory tests and high-resolution functional magnetic resonance imaging (fMRI) of the brain. Here’s how the study was conducted:

  • Participants came in on two separate occasions.
  • During each visit, participants either took part in 10 minutes of light-intensity biking or they sat quietly on the same bike for 10 minutes. The biking regimen was calibrated to 30 percent of each person’s maximum rate of oxygen consumption during exercise. That meets the definition of “very light” exercise by the American College of Sports Medicine.
  • In another round of testing, participants completed a memory test while researchers captured their brain activity by fMRI.

Following the biking regimen and also after sitting on the bike, each participant was administered two computerized tests. For the first, they were shown 196 different images of everyday objects, such as a coffee cup, flashlight, or eyeglasses. Participants answered whether each object represented an indoor or outdoor item. Unbeknownst to participants, their answers on this test weren’t important. This first phase was designed simply to hold their attention on the images.

In the second test, administered 45 minutes later, participants were shown 256 images of everyday objects. For each photo, they were asked whether the object was new, identical to one seen in the first test, or just similar. This test was designed to detect even subtle differences in an individual’s memory performance.

Participants made fewer errors on the image recognition test after they completed 10 minutes of very light exercise than when they only rested on the bike. Similar to the previous work in rodents, the subsequent brain scans of people during memory testing further showed that improved memory performance was accompanied by increased activity and connectivity in the brain.

Many questions remain. For example, the observed benefits of just 10 minutes of very light exercise were seen in healthy young adults. But will light exercise also help people who already have memory problems? And would longer periods of exercise, perhaps at a higher intensity level, work even better? The researchers are already trying to find the answers.

The NIH is funding a number of other promising studies and consortia that aim to optimize the health benefits of exercise. A particularly exciting one is the Molecular Tranducers of Physical Activity Consortium (MoTrPAC). The MoTrPAC effort will develop a comprehensive map of the molecular changes that arise with physical activity and lead to improved performance of multiple body systems. There’s no doubt that exercise is good for us. But it’s been much less clear how and why exercise changes our bodies and leads to better physical and mental health. The MoTrPAC project will be a big help in starting to clarify the process.

One of the most encouraging aspects of this latest study is it suggests that light intensity exercise, which is accessible to most people, comes with real benefits for the brain. As we learn even more about the underlying biology of exercise and memory, the goal is to enable doctors, personal trainers, and all those interested in enhancing health to make more precise exercise recommendations that are tailored to the specific needs and abilities of each person.

References:

 [1] Rapid stimulation of human dentate gyrus function with acute mild exercise. Suwabe K, Byun K, Hyodo K, Reagh ZM, Roberts JM, Matsushita A, Saotome K, Ochi G, Fukuie T, Suzuki K, Sankai Y, Yassa MA, Soya H. Proc Natl Acad Sci U S A. 2018 Sep 24. [Epub ahead of print]

[2] Long-term mild exercise training enhances hippocampus-dependent memory in rats. Inoue K, Hanaoka Y, Nishijima T, Okamoto M, Chang H, Saito T, Soya H. Int J Sports Med. 2015 Apr;36(4):280-285.

Links:

Exercise and Physical Activity (National Institute on Aging/NIH)

Molecular Transducers of Physical Activity in Humans (Common Fund/NIH)

Dr. Francis Collins on MoTrPAC (Common Fund)

Yassa Lab (University of California, Irvine)

Soya Lab (University of Tsukuba, Japan)

NIH Support: National Institute on Aging; National Institute of Mental Health