Swimming gives your brain a boost – but scientists don’t know yet why it’s better than other aerobic activities

 

Swimming offers a host of beneficial effects on the brain. Stanislaw Pytel/Stone via Getty Images

It’s no secret that aerobic exercise can help stave off some of the ravages of aging. But a growing body of research suggests that swimming might provide a unique boost to brain health.

Regular swimming has been shown to improve memory, cognitive function, immune response and mood. Swimming may also help repair damage from stress and forge new neural connections in the brain.

But scientists are still trying to unravel how and why swimming, in particular, produces these brain-enhancing effects.

As a neurobiologist trained in brain physiology, a fitness enthusiast and a mom, I spend hours at the local pool during the summer. It’s not unusual to see children gleefully splashing and swimming while their parents sunbathe at a distance – and I’ve been one of those parents observing from the poolside plenty of times. But if more adults recognized the cognitive and mental health benefits of swimming, they might be more inclined to jump in the pool alongside their kids.

New and improved brain cells and connections

Until the 1960s, scientists believed that the number of neurons and synaptic connections in the human brain were finite and that, once damaged, these brain cells could not be replaced. But that idea was debunked as researchers began to see ample evidence for the birth of neurons, or neurogenesis, in adult brains of humans and other animals.

Now, there is clear evidence that aerobic exercise can contribute to neurogenesis and play a key role in helping to reverse or repair damage to neurons and their connections in both mammals and fish.

Research shows that one of the key ways these changes occur in response to exercise is through increased levels of a protein called brain-derived neurotrophic factor. The neural plasticity, or ability of the brain to change, that this protein stimulates has been shown to boost cognitive function, including learning and memory.

It’s tempting for adults to watch kids splash from the poolside, but research shows it’s worth jumping in alongside them. Povozniuk/iStock via Getty Images Plus

Studies in people have found a strong relationship between concentrations of brain-derived neurotrophic factor circulating in the brain and an increase in the size of the hippocampus, the brain region responsible for learning and memory. Increased levels of brain-derived neurotrophic factor have also been shown to sharpen cognitive performance and to help reduce anxiety and depression. In contrast, researchers have observed mood disorders in patients with lower concentrations of brain-derived neurotrophic factor.

Aerobic exercise also promotes the release of specific chemical messengers called neurotransmitters. One of these is serotonin, which – when present at increased levels – is known to reduce depression and anxiety and improve mood.

In studies in fish, scientists have observed changes in genes responsible for increasing brain-derived neurotrophic factor levels as well as enhanced development of the dendritic spines – protrusions on the dendrites, or elongated portions of nerve cells – after eight weeks of exercise compared with controls. This complements studies in mammals where brain-derived neurotrophic factor is known to increase neuronal spine density. These changes have been shown to contribute to improved memory, mood and enhanced cognition in mammals. The greater spine density helps neurons build new connections and send more signals to other nerve cells. With the repetition of signals, connections can become stronger.

But what’s special about swimming?

Researchers don’t yet know what swimming’s secret sauce might be. But they’re getting closer to understanding it.

Swimming has long been recognized for its cardiovascular benefits. Because swimming involves all of the major muscle groups, the heart has to work hard, which increases blood flow throughout the body. This leads to the creation of new blood vessels, a process called angiogenesis. The greater blood flow can also lead to a large release of endorphins – hormones that act as a natural pain reducer throughout the body. This surge brings about the sense of euphoria that often follows exercise.

Most of the research to understand how swimming affects the brain has been done in rats. Rats are a good lab model because of their genetic and anatomic similarity to humans.

Rats serve as a useful laboratory model for understanding the effects of swimming on memory formation and brain health. irin717/iStock via Getty Images Plus

In one study in rats, swimming was shown to stimulate brain pathways that suppress inflammation in the hippocampus and inhibit apoptosis, or cell death. The study also showed that swimming can help support neuron survival and reduce the cognitive impacts of aging. Although researchers do not yet have a way to visualize apoptosis and neuronal survival in people, they do observe similar cognitive outcomes.

One of the more enticing questions is how, specifically, swimming enhances short- and long-term memory. To pinpoint how long the beneficial effects may last, researchers trained rats to swim for 60 minutes daily for five days per week. The team then tested the rats’ memory by having them swim through a radial arm water maze containing six arms, including one with a hidden platform.

Rats got six attempts to swim freely and find the hidden platform. After just seven days of swim training, researchers saw improvements in both short- and long-term memories, based on a reduction in the errors rats made each day. The researchers suggested that this boost in cognitive function could provide a basis for using swimming as a way to repair learning and memory damage caused by neuropsychiatric diseases in humans.

Although the leap from studies in rats to humans is substantial, research in people is producing similar results that suggest a clear cognitive benefit from swimming across all ages. For instance, in one study looking at the impact of swimming on mental acuity in the elderly, researchers concluded that swimmers had improved mental speed and attention compared with nonswimmers. However, this study is limited in its research design, since participants were not randomized and thus those who were swimmers prior to the study may have had an unfair edge.

Another study compared cognition between land-based athletes and swimmers in the young adult age range. While water immersion itself did not make a difference, the researchers found that 20 minutes of moderate-intensity breaststroke swimming improved cognitive function in both groups.

Kids get a boost from swimming too

The brain-enhancing benefits from swimming appear to also boost learning in children.

Another research group recently looked at the link between physical activity and how children learn new vocabulary words. Researchers taught children age 6-12 the names of unfamiliar objects. Then they tested their accuracy at recognizing those words after doing three activities: coloring (resting activity), swimming (aerobic activity) and a CrossFit-like exercise (anaerobic activity) for three minutes.

They found that children’s accuracy was much higher for words learned following swimming compared with coloring and CrossFit, which resulted in the same level of recall. This shows a clear cognitive benefit from swimming versus anaerobic exercise, though the study does not compare swimming with other aerobic exercises. These findings imply that swimming for even short periods of time is highly beneficial to young, developing brains.

The details of the time or laps required, the style of swim and what cognitive adaptations and pathways are activated by swimming are still being worked out. But neuroscientists are getting much closer to putting all the clues together.

For centuries, people have been in search of a fountain of youth. Swimming just might be the closest we can get.

Seena Mathew, Assistant Professor of Biology, University of Mary Hardin-Baylor

This article is republished from The Conversation under a Creative Commons license.

Poison ivy can work itchy evil on your skin – here’s how

 

Be on the lookout for poison ivy’s three leaves on a reddish stem. raksybH/iStock via Getty Images Plus

A patient recently came in to our dermatology clinic with a rash and a story similar to so many others. He had been out camping with friends a few days earlier and helped carry some logs to stoke the fire. Little did he know he was going to pay for lending a helping hand. A couple days later, red patches appeared on his forearms and chest, which soon began to itch miserably and form water blisters.

If you have ever spent any time outdoors – in the woods, working in the yard, even at the edges of a playground – maybe you’ve experienced something similar after encountering poison ivy. It’s not easy to forget.

Encounters with a botanical irritant

Poison ivy is found everywhere in the continental U.S., mostly in Eastern and Midwestern states. Unfortunately for us humans, it is a hardy plant that can grow under many different conditions. Its favorite places are in wooded areas, gardens and roadsides with partial shade or full sunlight.

And despite being a nuisance to people, poison ivy is an important member of the ecosystem. Its leaves, stems and berries are food for animals, and its vines can be shelter for small animals like toads and mice, even helping them climb trees. Climate change is turning out to benefit poison ivy, allowing for larger and more irritating plants.

You can usually spot poison ivy by its infamous three dull or glossy green leaves coming off a red stem. Sometimes there are flowers or fruits coming off the end of a branch.

Despite its name, poison ivy is not poisonous. It carries an oily sap on its leaves and stems called urushiol, which is irritating to most people’s skin. In fact, 85% to 90% of people are allergic to poison ivy’s urushiol to some degree, while the rest lack sensitivity to this oil. You can occasionally see the urushiol oil as black spots on poison ivy leaves. Urushiol is what gives poison oak and poison sumac their evil power, too.

Touching poison ivy directly is obviously a bad idea. You can even get into trouble by touching clothing, pets or anything else that has brushed against the plant and picked up some of the urushiol. If a contaminated object isn’t cleaned, the urushiol will remain lying in wait – it can still cause a rash after hours, days or even years. Another danger is smoke from burning poison ivy, which can also affect your skin, as well as your nose, mouth, windpipe and lungs if you breathe it in.

It’s a myth that the fluid from inside a blister can spread the rash. EzumeImages/iStock via Getty Images Plus

From oil to rash

Poison ivy’s rash can come in many forms, from small, red bumps to blisters or red patches. Whichever way it shows up, it is almost always mindbogglingly itchy.

When you get “poisoned,” you won’t know right away. It can take anywhere from four hours to 10 days for the rash to appear, depending on how much urushiol gets on your skin, how sensitive you are to it and how many times you have been exposed to poison ivy previously.

Between exposure and itchy anguish, your body goes through a complex identification and reaction process. When the oil gets into your skin, your immune system’s sensor cells recognize urushiol as foreign to your body. These sensor cells then call in protector cells to the area, warning them of the invasion. The protector cells defend your body against the intruder by attacking the urushiol in the skin. Unfortunately, some of your body’s normal skin cells are casualties of this war, which is what leads to the itchiness and swelling of a poison ivy rash.

Your protector cells will then sit near the skin for many years and stand guard for urushiol if it ever shows up again. If it does, they remember having encountered this bad guy before, and their response is often faster and more powerful than the first time.

This rash is a type of allergic contact dermatitis – in the same family as the rashes some people get from wearing jewelry or metal belt buckles or from using certain fragrances or cosmetics.

Learning what poison ivy looks like so you can avoid it is a crucial part of your defense. Onfokus/E+ via Getty Images

What to do once the damage is done

The saying “leaves of three; leave them be” highlights the best strategy to prevent poison ivy: avoidance. But if you do happen to come into contact with poison ivy, the first step should always be to remove and wash any clothing that has touched the plant. Gently but thoroughly wash your skin immediately with soap and water. It can also help to clean under your fingernails and cut your nails short to prevent the urushiol from spreading if you scratch your skin.

Allergic contact dermatitis from poison ivy almost always results in a rash that usually lasts two to three weeks before it completely goes away.

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It will eventually clear up on its own, but you can try some over-the-counter and home remedies to keep the itchiness and spread of the rash at bay. The blisters that form are not infected and do not normally require antibiotics. If you scratch though – and it can be very hard to resist – open skin can get infected.

To reduce itchiness, cool, wet compresses can help, as can a soak in a cool bath with baking soda or oatmeal bath products. Calamine lotions or creams containing menthol can also cut the itch a bit. Over-the-counter cortisone cream or ointment can be used for the first several days after contact with poison ivy to quiet down your body’s reaction and keep the rash from getting severe. Taking antihistamines like diphenhydramine at night can slightly reduce itchiness and it has the benefit of helping you sleep better.

Seeing your doctor usually is not necessary for a poison ivy rash unless it spreads over large areas, becomes infected, lasts more than three weeks or is a rare extreme case that affects your breathing.

The best offense is a good defense. When you’re in the great outdoors, be careful what you touch and, when in doubt, if it has leaves of three, leave them be.

Arthur Samia, Postdoctoral Research Fellow in Dermatology, University of Florida and Marjorie Montanez-Wiscovich, Clinical Assistant Professor of Dermatology, University of Florida

This article is republished from The Conversation under a Creative Commons license.