Although it is no bigger than your clenched
fist, your heart is able to pump more than two thousand gallons of blood
through sixty thousand miles of blood vessels each day. To do this, your heart
beats more than one hundred thousand times each and every day of your life. Your
heart is incredibly strong, but exercise training will make it stronger and
more durable. A healthy heart pumps about five quarts of blood a minute while
you are resting quietly. When you dash to make that bus, your heart rate may
double or even triple, and the remarkable little muscle will pump out up to
twenty quarts of blood a minute. Diseased hearts can't match this performance,
but exercise-trained hearts can do much more. At maximum effort, an athlete's
heart can pump up to forty quarts of blood a minute, and it can sustain a high
workload for much longer than the unconditioned heart can.
How does regular exercise help your heart?
Like your other muscles, your heart muscle gets larger and stronger with
exercise. Exercise also makes the heart muscle more efficient, so it needs less
oxygen for itself. Exercise training helps human hearts resist arrhythmias,
including the abnormal pumping rhythms that can lead to sudden death. And
moderate exercise will earn all of these heartfelt improvements for you.
For poets, the heart symbolizes emotion,
for soldiers, courage, and for lovers, romance. But for physiologists, the
heart is simply a pump. Its job is to pump oxygen- and nutrient-rich blood to
all your body's tissues; your arteries provide the delivery system that makes it
possible. Doctors used to think of arteries as passive conduits for blood,
working for your body the way a garden hose works for your lawn. Wrong! In
fact, arteries are complex structures with crucial regulatory functions, and
they are in the front line of the battle for cardiovascular health.
Every artery has three layers in its wall.
New research has focused on the inner layer, which is composed of a thin layer
of endothelial cells that are in direct contact with the bloodstream.
Endothelial cells have a crucial role in vascular health, and exercise training
has an important effect on them. Among other things, endothelial cells produce
nitric oxide, which has two crucial functions. It keeps the arterial lining
smooth and slippery, preventing damaging inflammation and artery-blocking blood
clots. In addition, it relaxes the smooth muscle cells of the artery wall's
middle layer, preventing spasms and keeping arteries open. Even in health, age
takes a toll on endothelial cells, reducing nitric oxide production so that
arteries become stickier, stiffer, and narrower. Exercise training boosts
nitric oxide production, keeping arteries supple and young. And here's more
good news: you don't have to start young or push yourself hard to get these
benefits. For example, when scientists from the University of Colorado
Exercise will help keep you and your heart
and arteries young. It will also keep your heart and arteries healthy. The
inner and middle layers of the artery wall are the battlegrounds of
atherosclerosis, the disease responsible for heart attacks, most strokes, and
many cases of kidney failure and for peripheral artery disease, which can lead
to gangrene and amputations, usually in the legs and feet. As you'll soon see,
exercise fights atherosclerosis, protecting you from heart attacks and strokes
of many cardiovascular diseases.
