- Seena Mathew
- The Conversation*
It’s no secret that aerobic exercise can help prevent some of the effects of aging.
But a growing body of research suggests that swimming may provide a unique boost to brain health.
Swimming regularly improves memory, cognitive function, immune response and mood.
Swimming can also help repair stress damage and forge new neural connections in the brain.
But scientists are still trying to figure out how and why this particular activity produces these beneficial effects on the brain.
As a brain physiology neurobiologist, fitness enthusiast, and mother, I spend hours at the local pool during the summer.
It is not unusual to see children splashing and swimming happily while their parents sunbathe in the distance. Even I have been one of those mothers many times.
But if more adults understood the mental health and cognitive benefits of swimming, they would jump into the pool with their children.
New and improved brain cells and connections
Until the 1960s, scientists believed that the number of neurons and synaptic connections in the human brain was finite and that, once damaged, these brain cells could not be replaced.
But that idea was debunked when researchers began to see extensive evidence for neuron birth, or neurogenesis, in the adult brains of humans and other animals.
There is now clear evidence that aerobic exercise can contribute to neurogenesis and play a critical 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 (DCFN).
Neural plasticity, or the brain’s ability to change, caused by this protein has been shown to stimulate cognitive function, including learning and memory.
Studies in people found a strong relationship between levels of FNDC circulating in the brain and an increase in the size of the hippocampus, the region of the brain responsible for learning and memory.
Increased levels of brain-derived neurotrophic factor have also been shown to sharpen cognitive performance and help reduce anxiety and depression.
In contrast, researchers observed mood disturbances in patients with lower concentrations of FNDC.
Aerobic exercise also stimulates the release of specific chemical messengers called neurotransmitters.
One of them is the serotonin which, when present at high levels, reduces depression and anxiety and improves mood.
In fish studies, scientists observed changes in the genes responsible for increasing levels of FNDC, as well as increased development of dendritic spines (protrusions on dendrites or elongated portions of nerve cells) after eight weeks of exercise compared to with the controls.
This complements studies in mammals where FNDC is known to increase the density of the neuronal spine. These changes were shown to help improve memory, mood, and cognition in mammals.
The higher density of the spine helps neurons build new connections and send more signals to other nerve cells. With repeating signals, connections can become stronger.
But what is special about swimming?
Researchers do not yet know what the secret behind swimming could be. But they are getting closer to figuring it out.
Swimming has long been recognized for its cardiovascular benefits.
And this is because the activity involves all the major muscle groups and the heart has to work very hard, increasing blood flow throughout the body. This leads to the creation of new blood vessels, a process called angiogenesis.
The increased blood flow can also lead to a large release of endorphins, hormones that act as a natural pain reliever throughout the body. This increase causes the feeling of euphoria that often follows exercise.
Most of the research to understand how swimming affects the brain was done in rats. They make a good laboratory model due to their genetic and anatomical similarity to humans.
In a study in rats, swimming was shown to stimulate brain pathways that suppress inflammation in the hipocampo and they inhibit apoptosis or cell death.
The study also showed that swimming can aid neuron survival and reduce the cognitive impacts of aging.
Although researchers don’t yet have a way to visualize apoptosis and neuronal survival in people, they do see similar cognitive outcomes.
One of the most fascinating questions is how, specifically, swimming improves short-term and long-term memory.
To determine how long the beneficial effects may last, the researchers trained rats to swim for 60 minutes a day for five days a week.
The team then tested the rats’ memory by having them swim through a special apparatus called a radial arm maze that contains six arms, including one with a hidden platform.
The rats had six attempts to swim freely and find the hidden platform.
After just seven days of swimming training, the researchers observed memory improvements both short and long term, based on a reduction in the mistakes rats made each day.
Scientists suggest that this boost in cognitive function could provide a basis for using swimming as a way to enhance learning and repair memory damage caused by neuropsychiatric diseases in humans.
Although the gap between the rat and human studies is substantial, research in people is generating similar results that suggest a clear cognitive benefit of swimming at all ages.
For example, a study that looked at the impact of swimming on mental acuity in the elderly found that swimmers had improved mental speed and attention compared to non-swimmers.
However, this study has a limited research design, as the participants were not randomized and therefore those who were swimmers prior to the study may have had an advantage.
Another study compared cognitive function between athletes exercising outside of water and swimmers in the young adult age range. While immersion in water itself didn’t make a difference, it was found that 20 minutes of breaststroke swimming of moderate intensity improved cognitive function in both groups.
Children and swimming
The brain-enhancing benefits of swimming also appear to boost learning in children.
Scientists examined the link between physical activity and how children learn new vocabulary.
The researchers taught the 6 to 12-year-olds the names of unfamiliar objects. They then tested their accuracy in recognizing those words after doing three activities: coloring (rest activity), swimming (aerobic activity), and an exercise similar to CrossFit (anaerobic activity) for three minutes.
They found that children’s performance was much higher for words learned after swimming compared to coloring and anaerobic activity, resulting in the same memory level.
This shows a clear cognitive benefit of swimming versus anaerobic exercise, although the study does not compare swimming with other aerobic exercises.
These findings imply that swimming even for short periods of time is very beneficial for young developing brains.
The details of swimming time, swimming style, and cognitive adaptations and pathways activated by swimming are still being studied. But neuroscientists are getting closer and closer to gathering all the clues.
During centuries, people have been searching for a fountain of youth. Swimming could be as close as we can get.
*The author is an assistant professor of Biology at the University of Mary Hardin-Baylor (Texas, USA).
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Eddie is an Australian news reporter with over 9 years in the industry and has published on Forbes and tech crunch.