Exercise builds brawn — and brains

Got an exam coming up? Head to the gym. It won’t just tone muscle and keep you fit. It could also rev up your memory.

Plenty of research has shown that moving the body — whether jogging, lifting weights or even playing fitness video games — helps the mind. However, many of those studies reported mental benefits only after participants exercised regularly for months or years. Now there’s hope for couch potatoes: Just one 20-minute session of simple leg exercises can give the brain a lift, a new study finds.

Its lead scientist, Audrey Duarte, works in the Memory and Aging Laboratory at the Georgia Institute of Technology in Atlanta. As a neuroscientist, she’s interested in why memory starts slipping as people age. And she suspected exercise might slow that decline. “We wanted to find simple things people can do to boost their memory, even just a little bit,” she told Science News for Students.

Many earlier studies had asked volunteers to really move around. They assigned people to do various types of aerobic exercise, such as walking for an hour three times a week. Aerobic exercise makes the heart and lungs work hard. That helps to build muscle and improve blood flow. Duarte’s team set the bar far lower. They assigned participants to do leg lifts — a type of resistance exercise. Such exercises rely on the contraction of muscles to build strength in particular tissues. Leg lifts have a second benefit: ease. “Anyone can do a 20-minute bout of moving their legs up and down,” Duarte says.

Indeed, these leg lifts would be easy enough for grannies to do — even patients with dementia. However, for its initial study, Duarte’s group worked with college students. Recruiting them for research tends to be easier. The researchers didn’t want gym rats or athletes, though. They wanted to see if a single session of leg lifts might benefit even people who don’t exercise regularly.

Before, during and after the leg exercises, the researchers measured heart rate and blood pressure in each of their 46 young recruits. They also took a small sample of saliva from each. From that they could measure an enzyme called amylase. This enzyme helps to digest starch. It also increases during times of short-term stress — such as keeping your hand submerged in cold water or getting filmed while giving an impromptu speech.

Research subjects in prior studies have faced those very stressors. The result? Increased stress hormones and higher amylase levels — but better memory.

The leg lifts were performed using weights that targeted the quadricep muscles. The weight lifted was adjusted to match each person’s maximal ability. Just 20 minutes of leg lifts produced amylase boosts similar to those produced during short-term stress, Duarte’s team found. (Half the participants served as the control group. They moved their legs up and down on the same machine. Here, though, a researcher lifted each person’s legs instead of relying on a recruit’s muscles to do it.)

Before doing lifts, each recruit viewed a series of 90 pictures. Then they went home with the instruction to do no more exercise. Two days later, they returned to the lab for a test. A researcher showed each person 180 photos — half from the initial set — and then asked the subjects to indicate which ones looked familiar. The group that had done leg lifts scored about 10 percent higher than the control group.

“What we found was on par with studies looking at how psychological stress can benefit memory in the short term,” says Duarte. She thinks the magic happens during the “consolidation” phase. That takes place after learning. It’s when memories are getting laid down in the brain.

Other scientists who study exercise and brain activities find the new results compelling. “Aerobic training has taken center stage as the type of exercise for improving brain health,” says Teresa Liu-Ambrose. She’s a cognitive scientist at the University of British Columbia in Vancouver, Canada. She notes, however, that “resistance training is emerging as an equally good option… and you can reap the benefits quite quickly.”

Eelco van Dongen is a neuroscientist at Radboud University in Nijmegen, the Netherlands. He finds the new paper “very impressive.” To his knowledge, it’s the first time researchers have shown that a single round of resistance training can boost memory.

The regimen’s simplicity “will make it easier to apply in daily life or to use with people suffering memory problems,” van Dongen says. He is currently running a similar study with young adults in the Netherlands. It will test if memory can improve with a single session of interval training on a stationary bike. That’s a type of workout with alternating periods of high- and low-intensity exercise. His study has recruited people who already had been exercising regularly.

In the future, Duarte’s team plans to test if the leg regimen can improve brain power in older people. The group also would like to check if the benefits last longer than 48 hours — and if doing the exercises several times a week might yield a bigger boost.

Power Words

aerobic exercise     Typically this includes periods of swimming, running, jumping, or stair climbing. This exercise gets its name from making the heart and lungs work to not only build muscle but also to improve the heart and respiratory system.

amylase     An enzyme that breaks starches down into the sugars from which they had been made.

cognition    The mental processes of thought, remembering, learning information and interpreting those data that the senses send to the brain.

cognitive science    A field that studies mental activities, such as thinking, learning, remembering and solving puzzles.

consolidate    To bring together or merge.

control     (in a study’s design) A part of an experiment where nothing changes. The control is essential to scientific experiments. It shows that any new effect must be due to only the part of the test that a researcher has altered. For example, if scientists were testing different types of fertilizer in a garden, they would want one section of to remain unfertilized, as the control. Its area would show how plants in this garden grow under normal conditions. And that give scientists something against which they can compare their experimental data.

couch potato    Slang for people who get very little exercise, often because they spend much of their leisure time sitting around, usually watching television.

dementia    A type of mental disorder caused by disease or injury that causes people to gradually lose all or part of their memory. It may start out temporary and build to a permanent condition where the ability to reason also is impaired.

enzymes   Molecules made by living things to speed up chemical reactions.

neuroscience  Science that deals with the structure or function of the brain and other parts of the nervous system. Researchers in this field are known as neuroscientists.

quadricep muscles    A large muscle group on the front of the thighs that includes four principle muscles — hence the name quad, for four. These muscles are often simply referred to as the quads.

resistance    A type of rather sedentary exercise that relies on the contraction of muscles to build strength in localized tissues.

sedentary    Not physically active; an adjective for activities done largely while sitting.

stress  (in biology) A factor, such as unusual temperatures, moisture or pollution, that affects the health of a species or ecosystem.