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Exercise
Boosts Clot-Dissolving Protein
A
half hour of minimal exercise can give people with hardening of
the arteries in their legs or arms a boost in protection from
a heart attack or stroke, a study finds.
The study
found walking boosted levels of a natural clot-dissolving chemical
called tissue plasminogen activator, known as TPA. The body makes
TPA, and genetically engineered versions are used as drugs to
treat heart attack and stroke.
The study
examined people with peripheral arterial disease, a condition
similar to the narrowed vessels in coronary artery disease. In
either case, blood clots can develop in the constricted arteries.
If a clot travels to the heart, the result is a heart attack.
If it travels to the brain, the result is a stroke.
The study,
which was published in the February issue of the American College
of Sports Medicine journal, Medicine and Science in Sports
and Exercise.
The study
done at the University of Maryland looked at eight men and one
woman with an average age of 70. The condition is more common
as people get older, and more common among men than women, said
lead author Christopher J. Womack, now at Michigan State University.
All nine
hurt if they walked too far. The disease reduces blood flow to
the legs, leading to cramping and fatigue, although their symptoms
subsided with rest. No patient had been an exerciser before taking
part in the study.
The researchers
had the nine walk for 30 minutes each, not including any rest
breaks. The pace would have been gentle for a healthy person,
but it was tough for the patients because of the pain it generated,
Womack said.
The scientists
measured changes in TPA and another chemical, plasminogen activator
inhibitor, PAI-1, which binds to TPA and neutralizes it. The balance
between TPA and PAI-1 helps to regulate the ability to clot.
Before exercise,
the patients had only 80 percent of normal TPA levels, so their
ability to dissolve clots was reduced, Womack said.
After exercise,
however, TPA levels were about the same as those in a non-exercising
person of the same age with peripheral arterial disease, the study
found. Levels of PAI-1 fell at the same time. And the changes
in both remained significant for at least an hour after the walk,
the report said.
"An increase
in TPA is good for you, and a decrease in PAI-1 is good for you,"
commented researcher Anna Carter of the University of Leeds in
England, who was not a part of the study. "High levels of PAI-1
have been related to heart disease, and low levels of TPA have
been related to heart disease."
The changes
were strong enough potentially to reduce the risk of an artery
blockage, and the findings add to evidence that should encourage
people with peripheral arterial disease to be physically active,
Womack said.
Other studies
have shown that aerobic activity improves the ability of patients
to perform activities of daily life, and trains them to go farther
without feeling pain.
There is a
risk that exercise can jar loose a clot -- causing what the exercise
program was aimed at preventing, Womack conceded. But the risk
of this is very small, and the benefits of exercise are large,
so the benefits generally outweigh the risk, he said.
Reference
Source 99
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