From The Desk Of Clarence Bass
“Exercise training may be effective because it appears to improve the function
of virtually every cell in the cardiovascular system.”
Marvelous Mechanisms of the Heart
Strength Training’s Unique Benefits
Heart disease is a major cause of disability and death especially as we grow older. The more we know about the heart the better able we are to care for ourselves in a time of uncertain health care.
The National Institute on Aging (NIA) has produced a fact filled, recently updated, five chapter booklet entitled Aging Hearts and Arteries: A Scientific Quest. Age being the major risk factor for cardiovascular disease, it is important to understand what is happening in the heart and arteries during normal aging. “This understanding has moved forward dramatically in the past 30 years,” the booklet begins. It tells about the progress and explores some of the most important findings.
We’ll focus on how the heart works—the details take are breathtaking—and how exercise makes the heart and arteries function better at any age.
The first chapter begins with these awe-inspiring heart facts: It is scarcely as big as the palm of your hand yet it sustains life, pumping up to 5 quarts or more of blood per minute to the body’s organs, tissues, and cells. In a typical day, it beats 100,000 times. And in a lifetime, it beats more than 2.5 billion times. Even as you rest, your heart is working twice as hard as your leg muscles would if you were running at full speed.
The mechanics that make that possible read like science fiction coming true as our understanding grows. One area where we know more now than we did even a decade ago, is how the heart changes with age. To understand those changes—and how to combat them—we start with the normal, healthy heart.
“The heart is a marvel of coordination and timing,” the booklet begins.
Almost completely composed of a distinct form of endurance muscle called myocardium, the heart is essentially two pumps in one. The right side pumps blood to the lungs to dispose of carbon dioxide and load up on oxygen. The left side pumps oxygen-rich blood to all parts of the body.
The atria are the receiving chambers of the heart and the ventricles are the pumping chambers. The right atrium receives the body’s spent blood and passes it into the right ventricle. The right ventricle pumps the blood into the lungs for reoxygenation. The left atrium receives the freshly oxygenated blood and passes it into the left ventricle, which pumps the oxygen loaded blood to all parts of the body.
To accomplish these tasks, the heart depends on a precise sequence of contractions involving the two upper chambers—the right and left atria—and the two lower chambers, the right and left ventricles. Between these chambers are two valves. One valve separates the right atrium and the right ventricle. Its counterpart separates the left atrium and the left ventricle. A third valve controls blood flow out of the right ventricle to the lungs where it picks up oxygen. Finally, the aortic valve controls the flow of oxygenated blood out of the left ventricle into the body. Normally these valves let blood flow in just one direction.
This cardiac cycle is regulated by electrical impulses, generated by the heart's internal pacemaker, a small bundle of specialized cells located in the right atrium. These impulses cause the heart to beat. Once generated, the impulses spread in a coordinated fashion across the heart muscle in less than a quarter of a second. As they travel, the impulses are relayed through switching stations at precise intervals, eventually causing millions of interlocked cells to contract in near unison.
Then the cycle begins again, over and over, for up to 100 years or more.
Yes, but wait until you hear about the curve ball that aging, normal aging, chucks into the perpetual motion of the heart.
“Aging, it turns out, brings not a simple slowing down of heart function, as one might expect, but a set of intricate alterations: a slowing here, an enhancement there, a minor adjustment elsewhere,” says the NIA booklet. “In various ingenious, important ways, the heart at age 65 has adapted to meet the needs of the 65-year-old body.”
Unfortunately, these alterations have a downside. In recent years, gerontologists have learned that some changes in the structure and function of the aging cardiovascular system, even in a healthy older person, can increase the risk of developing cardiovascular disease, including high blood pressure, atherosclerosis, and heart failure. In fact, these normal changes can create the nearly perfect setting for the onset of severe cardiovascular disease in some healthy older people.
Gerontologists are intensely studying new ways to prevent and treat cardiovascular disease in older people. They are learning much more about how physical activity (along with diet and other lifestyle factors) influences the "rate of aging" in the healthy heart and arteries.
Exercise: Your Heart's Best Friend
The NIA booklet begins a sidebar on exercise with a delightful quip from comic Ellen DeGeneres: My grandmother started walking five miles a day when she was 60. Now she's 97 years old and we don't know where the heck she is.
Funny, yes. But regular physical exercise is no joke. “It may be the most important thing a person can do to fend off heart disease, stroke, and other age-associated diseases” the NIA authors counsel. “Emerging scientific evidence suggests that people who exercise regularly not only live longer, they live better.”
Scientists have long known that regular exercise causes certain changes in the hearts of younger people: Resting heart rate is lower, heart mass is higher, and stroke volume is higher than in their sedentary counterparts. These differences make the heart a better pump. Evidence now suggests these changes occur even when exercise training begins later in life. You don't outlive the ability to improve your physical condition.
“Exercise training may be effective because it appears to improve the function of virtually every cell in the cardiovascular system,” the NIA authors declare expansively. For example, exercise preserves the health of the endothelial cells which line the heart and blood vessels. “Endothelial cells are the prima donnas within the blood vessels,” says Edward Lakatta, MD, Chief of the Laboratory of Cardiovascular Science at the NIA. “They control almost every activity that occurs in the vessels, and they’re fundamentally altered with age.”
It is well established that endurance exercises such as hiking, swimming, and biking increase stamina and improve the health of your heart, lungs, and circulatory system. While the NIA booklet notes that strength training builds muscle, bone density, and self-reliance, it is silent about the effect on the heart and blood vessels. For that we must look to other sources.
Combination Training Best
We often forget the part skeletal muscles play in moving blood around the body. Blood travels back to the heart by way of the veins. Since veins cannot contract they rely on the muscles of the body to help transport the blood. When muscles contract it propels the blood along. Muscles also challenge—and strengthen—the heart. The more active muscle fibers we have the better.
The muscle fibers affected by endurance and strength training are different: endurance training activates the slow twitch fibers, while strength training activates both the slow- and fast-twitch fibers. Dr. Edward Coyle, Department of Kinesiology and Health Education at the University of Texas, Austin, has written that moderate intensity endurance exercise as typically prescribed for endurance and health leaves half of the muscle fibers unused and untrained. Importantly, Coyle added that fast and slow fibers are equally responsive in their ability to increase oxygen processing activity. Both fiber types contribute to cardiovascular health and efficiency.
Endurance training alone is like pulling a two-horse wagon with one horse.
Research has shown that both endurance and strength training contribute to heart and artery fitness.
An October 2010 study from Germany found that endurance training and resistance training produce different types of adaptation in the heart. “The volume load in endurance training leads to thickening of the ventricular wall and cavity dilatation [expansion], whereas the pressure load in resistance training induces…increased myocardial [heart muscle] mass and wall thickness, without a substantial change in cavity size,” the researchers wrote.
“The cardiac adaptations in the [athletes] we studied were characterized by a balanced increase in left and right ventricular muscle mass, wall thickness, dilation [expansion] and diastolic function,” the authors related. These adaptations reflected both endurance and strength components, they explained. (See our article # 282)
More of the details were filled in by Erica L. Robinson, a student at the Canadian College of Naturopathic Medicine, in a recent article on Active.com. Amplifying Dr. Coyle’s observations, Robinson explained that more working muscle means more blood flow and blood volume returning to the heart. That means a greater adaptation when both slow and fast fibers are working.
“Strength training exercise works the heart in a completely different way,” Robinson wrote. In addition to more muscle fiber activation, strength training constricts blood flow through the muscles. “This leads to increased blood pressure in the rest of the body and the heart has to fight against a stronger force to push blood out,” she explained.
As noted earlier, the heart adapts by increasing the muscle thickness of the ventricular wall. Both Robinson and the German researchers call this a healthy adaptation.
Robinson contrasts this to the thickness brought on by chronic high blood pressure. The difference, she says, is that the healthy heart has to work under pressure during strength training, while chronic high blood pressure makes the heart work harder around the clock. “The second heart may exhaust, whereas the healthy heart becomes stronger with a lower resting heart rate,” she explained.
In closing, Robinson explained that exercise creates more places for blood to flow, which results in more efficient blood flow. “Cardiovascular exercise increases the number of new blood vessels while resistance training increases the size of those blood vessels,” she wrote. (Resistance training also builds new muscle with new blood vessels.)
Expanding on this, a study reported in the November, 2010, issue of The Journal of Strength and Conditioning Research compared blood flow after the two forms of training—finding another unique benefit of resistance training. Again, the two forms of exercise are complementary.
Researchers led by Scott R. Collier, PhD, Appalachian State University, Boone, NC, compared blood vessel response following 30 minutes of moderate intensity stationary cycling and after upper and lower body weight training. They found that resistance training increased blood flow to the limbs, while causing a small increase in central artery (aortic) stiffness. In contrast, aerobic exercise lessened central artery stiffness—but without an increase in blood flow. The two forms of training balanced one another, producing a favorable effect greater than either alone. (Measurements were taken before and 40 and 60 minutes after the two forms of exercise.)
Interestingly, resistance training also led to a longer lasting drop in blood pressure after exercise, compared to aerobic exercise—alleviating concern that resistance training may worsen hypertension.
“The present study indicates that an acute bout of resistance exercise shows many favorable cardiovascular benefits and…could be implemented as [a] companion to an aerobic training regimen,” Dr. Collier and his colleagues concluded.
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Learning about the heart makes you want to do all you can to keep yours going strong. Science is showing us that exercise holds an important key. Having exercised regularly since my teens—mostly weights early on and a combination of weights and aerobics over the last 40 or so years—I can attest to the power of regular exercise. My primary care doctor tells me that it’s a pleasure to listen to a healthy heart in someone my age. (Now 76)
Carol took my waking pulse a few days ago at 52. That means my heart pumps significantly more blood with each stroke than the healthy person with a resting heart rate 20 beats higher. My blood pressure sitting comfortably at my desk averages about 105/65, when my doctor at the Cooper Clinic says a healthy goal is less than 140 over 85.
Using computed tomography angiography (CTA), Dr. John S. Ho, a nuclear cardiologist at the Cooper Clinic, twice found my coronary arteries to be “very large.” At the time of the second CTA, he gleefully told his staff that I am a sterling example of the power of exercise.
I intend to do all I can to keep these wonderful doctors happy for many more years.
Here’s to a strong and healthy heart for everyone!
For many more details on the aging heart, you can read the NIA booklet online: http://www.nia.nih.gov/health/publication/aging-hearts-and-arteries/chapter-1-host-interconnections
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