What’s all that swimming doing to your vascular system anyway?

Ed Coates attends Maters swim practice in Austin, Texas, as regularly as sunrise. When he misses a workout, his teammates at Longhorn Aquatics take note. So it was such a big deal when the 50-year-old human resources executive didn’t step foot on a pool deck for a fortnight in May 2002. “I swam well at Zones earlier that year but then had a hard time recovering,” he recalls. Coates remembers feeling tight in the chest, short of breath, lightheaded, and sluggish after the meet.

A disappointing result at his next swim event raised smoke signals. “For the first time in my life I started an open water swim and couldn’t finish it,” he says. A doctor visit turned up an abnormal EKG, which led to an angiogram and the discovery of 100-percent blockage in his right coronary artery. “I was two weeks away from a heart attack,” he says. Two stents and a few weeks later, Coates returned to the pool a changed man. “I knew I had to make some serious lifestyle improvements,” he says.

Coates was diagnosed with coronary artery disease, the most common type of heart disease and the leading cause of death for both men and women in the United States. More than 600,000 people in the United States will die from some kind of heart disease this year. High blood pressure, high cholesterol, and smoking are key risk factors for heart disease, though other medical conditions such as diabetes and obesity, genetics, and lifestyle choices can put people at higher risk.

Coates, who doesn’t smoke, knew he had high cholesterol and a family predisposition for heart trouble, but he had no idea how seriously ill he’d become. “Swimming saved my life because it told me I had a problem. I’d be dead if I hadn’t listened,” he says. His cardiologist put him on beta-blockers, blood thinners, and fish oil supplements, and ordered more fruits, vegetables, and fish. She also urged him to continue swimming—with no restrictions on training intensity.

Since then, Coates has eaten his salmon, swallowed his pills, and led his lane at swim practice like a metronome. “I swim better now than I did 14 years ago,” he says. “I can’t get my heart rate up anymore, so I don’t sprint,” he laughs. Still, he has more endurance today and posts faster times at swim meets. “I’ve become a different kind of swimmer. I’m a distance swimmer now,” he says.


Ed Coates thought he was healthy. He swam regularly. He took cholesterol medications. He maintained a healthy weight. But signs of trouble didn’t appear to him until it was nearly too late.

“It’s often the case that people with arterial disease have no symptoms,” says Hirofumi Tanaka, kinesiology professor and director of the Cardiovascular Aging Research Laboratory at the University of Texas at Austin. Tanaka, who studies the effects of swimming training on vascular function, says plenty of people have clogged arteries and no idea of it. “Eighty percent of heart disease is really arterial disease,” Tanaka explains, “and when we talk about vascular health, we’re talking about healthy veins and arteries.”

Arteries carry oxygen-rich blood to the organs; veins carry blood back to the heart. Healthy arteries have the elasticity of a rubber band, expanding with each heartbeat and contracting between them. Veins, less muscular than arteries, have valves that open and close to let blood through. Problems along this vast web of blood vessels—called the vascular system—can cause severe health problems and death.

Tanaka’s research on swimming and vascular function stands nearly alone. “There’s just not much of it out there,” he says. “It’s hard to conduct research in water, which means people don’t do it,” he notes. Luckily, he does do a good bit of it, and his studies have shown that regular swimming exercise can lower blood pressure and improve vascular function, particularly in previously sedentary older adults. These clinically significant findings make swimming a good alternative to walking or running when it comes to preventing and treating risk factors for cardiovascular disease. Land-based cardio exercises work the same magic, but Tanaka points to some key benefits unique to swimming: It’s isotonic and nonweight-bearing, and it has a low chance for heat-related illness. “Plus, it’s fun and people tend to stick with it,” he adds.


Experts measure vascular health by looking at endothelium function (the inner lining of blood vessels), arterial-wall thickness (plaque buildup), profusion (blood flow), and arterial stiffness (the ability of an artery to expand and contract based on the amount of blood flow). Arteries naturally stiffen with age, but overly stiff arteries can lead to hypertension, stroke, and kidney disease. Poor diet and an inactive lifestyle can also contribute to arterial stiffness. Tanaka’s research shows that regular swimming exercise can prevent and even reverse this stiffening process.

Most people don’t know it when their arteries lose flexibility. “You won’t feel anything or see a decrease in performance,” Tanaka says, “so you have to test for it.” Insurance companies tend not to pay for this expensive test, meaning doctors don’t do it regularly. Tanaka thinks they should. “They do it in Korea and Japan as a preventative measure,” he notes, “so why not here?” Doctors do, however, screen for plaque buildup in the arteries to assess risk for heart disease. They also routinely check blood pressure, though this measurement only gives information about arterial pressure, not function. Blood pressure readings above 120/80 mmHg should raise eyebrows and have doctors considering the possibility of other cardiovascular health problems.


High blood pressure poses a major public threat as the most prevalent vascular disease. The Centers for Disease Control and Prevention reports that about one in every three U.S. adults has hypertension—approximately 70 million people. Experts guess only half of them have their blood pressure under control. Many people don’t even know they have a problem. The numbers look nearly as bad for folks with prehypertension: higher-than-normal blood-pressure readings not yet in the danger zone. These statistics suggest a large swath of the population walks around with an asymptomatic medical condition that raises risk for stroke and heart disease. Americans pay dearly for it. The CDC says high blood pressure costs the nation $46 billion each year in healthcare services, medication costs, and lost productivity. Any way you look at it, hypertension is a big deal.

“They call it the silent killer because it has no warning signs,” says cardiologist Craig Siegel, who swims Masters at Longhorn Aquatics six days a week. He firmly believes swimmers should have an annual physical to screen for underlying medical conditions. “People ought to know their blood pressure, cholesterol, and resting heart rate,” says Siegel, who has a penchant for using car analogies to explain himself. “Is your car idling too fast?” he says, inquiring about a racing pulse. Going years without a medical visit is no pride point to him. “Do you take your car in for a regular oil change?” he asks. “Then why not your body?” Go see your doctor.

And it’s good advice: Just ask Karin Stokes, 55, who learned during a routine doctor visit that her blood pressure had inched up. She’s a project manager in Windham, N. H., and swims with the Granite State Penguins workout group of New England Masters. “Initially, I tried to control the problem on my own by losing weight and eating better,” she says. “I’m not a big medication person.” Stokes lost 25 pounds and her blood pressure dropped. But eventually, long hours at a stressful job sent the scale and her blood pressure back up to unhealthy levels. “My doctor told me I would hurt my organs if I didn’t go on meds,” she says. A low dose of hydrochlorothiazide—a diuretic commonly prescribed for hypertension—stabilized her blood pressure within three months. Then Stokes made another bold move: She started swimming again. Twenty years had elapsed since her gruelling college-swimming days had ended and she swore off pace clocks forever. “It was completely different this time around,” she says. The workouts helped her release stress and lose weight. “Swimming made me a happier, more well-rounded person,” she adds. Although Stokes agrees that medication helped control her blood pressure, she doesn’t give it all the credit. “I’ve never once had to increase my meds, which I attribute to swimming,” she says.


Stokes’s story helps explain why Siegel, the Austin cardiologist, spends considerable time talking to his patients about diet and exercise. “It’s easier to control blood pressure if you’re eating well and staying active,” he says. Even with medication, what goes into the body still matters. So does quality sleep, at least six hours of it, and daily movement.

“The less we do to stay active, the harder it becomes to be active,” he says. Siegel may feel partial to swimming exercise—he swam for two years at Harvard—but he’s also read Tanaka’s research linking the sport to vascular health. He believes, too, that swimming poses no risk to people who control their blood pressure with medication. Siegel tries to make his patients understand that they don’t need to be elite athletes to feel the benefits of exercise. “There’s a training effect at any level,” he says. “You can swim Masters or swim a few laps—just do something!”

Siegel highlights another important point. “There’s a gender bias in medicine,” he warns. Studies have shown that when men and women complain of pain indicative of heart disease, doctors take women less seriously. Several reasons account for the bias. Society, culture, and gender roles have played their part; until recently, researchers largely made medical breakthroughs by studying Caucasian males and extrapolating the data onto females. Another reason is that men have more early heart attacks, meaning doctors may overlook complaints from less-commonly symptomatic younger women.

Though more and more medical research targets women and a range of ethnicities, the initial slant towards men has left its mark. “We just don’t know as much about heart disease when it comes to women,” Siegel says. And women, when diagnosed, have more advanced heart disease than men, possibly because they tend to get diagnosed later. Doctors do know that symptoms of heart disease manifest differently in the two sexes. Consider, for example, a heart attack. Men typically have the classic chest and arm pain before a heart attack. Women tend to feel jaw and back pain or a burning sensation in the chest, rather than pain or pressure, and sometimes shortness of breath, fatigue, or nothing at all. Siegel raises the matter of gender differences not to create controversy but to help swimmers interpret important signs. Tuck away this information and hope you never need it poolside someday.

Hypertension, heart disease, and other vascular problems need not leave Masters swimmers on dry land. Keeping tabs on health can lead to a longer swimming life and a more robust vascular system. And small steps make big differences. Check your blood pressure between doctor visits with a home device and properly fitting cuff. Schedule regular physicals. Know your cholesterol level. Watch your saturated fat and sodium intake. Get enough rest. A little locker room peer pressure can help teammates hold each other accountable along the way. “In the men’s room we say, ‘Hey, have you had your colonoscopy yet?’” Siegel laughs. But it works. Then, the good doctor can’t resist one more automotive quip: “Swimmers look at their bodies like race cars,” he says, “so they have to be in the best possible shape.”



Blood pressure is measured using two numbers. The first number, called systolic blood pressure, measures the pressure in your blood vessels when your heart beats. The second number, called diastolic blood pressure, measures the pressure in your blood vessels when your heart rests between beats.

If the measurement reads 120 systolic and 80 diastolic, you would say “120 over 80” or write “120/80 mmHg.”

The chart below shows normal, at-risk, and high blood pressure levels. A blood pressure less than 120/80 millimeters of mercury is normal. A blood pressure of 140/90 mmHg or more is considered too high. People with levels in between 120/80 and 140/90 have a condition called prehypertension, which means they are at high risk for high blood pressure.

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