Report on Blood Clots during Exercise - Current Comments
IMPACT Exercise has
both increases and decreases the risk of blood clot formation. People
who do not exercise regularly increase their tendency to form clots
during exercise. On the other hand, people who exercise regularly
increase their ability to dissolve clots. This helps protect active
people from exercise-induced heart attacks and is probably one of the
reasons that being active decreases the risk of having a heart attack
during exertion. Sedentary individuals with cardiovascular disease have
a greater increase in thrombus formation during exercise compared to
healthy individuals, but this increase is not balanced with a larger
increase in fibrinolysis. This can lead to increased risk of stroke or
heart attack during exercise for this population. Adaptations To Exercise
One potential way to improve fibrinolysis and
decrease risk of a thrombus is to engage in a regular aerobic exercise
program. Several studies indicate that sedentary individuals have worse
fibrinolysis than individuals who exercise. In addition, sedentary
individuals who begin a regular exercise program show improvements in
fibrinolysis, both at rest and during physical stress. So the best way
to decrease risk of having a cardiovascular event during exercise is to
exercise regularly! Also, the hormonal environment can change, making
it less conducive to increasing muscle mass and strength
Written for ACSM by Christopher J. Womack, Ph.D.
ACSM Current Comment
may be little one can do about age or genetics, both risk factors for
poor fibrinolysis. However, regular exercise, sound nutrition, and
smoking cessation can go a long way toward improving fibrinolysis.
Because cardiovascular events during exercise relate to both the
intensity and duration of exercise, start slowly and conservatively at
the beginning of any exercise program. Walking and stationary cycling
are two conservative aerobic exercises, done in moderation. Remember to
consult your physician and an ACSM-certified fitness professional prior
to participating in any exercise program for the best advice to
increase your fitness efficiently and safely.
Blood Clots During Exercise An ACSM Report Although
exercise reduces heart attacks and deaths from heart disease, vigorous
exertion can also provoke or "trigger" a heart attack in persons with
silent atherosclerosis. This is a rare event. For example, there is
only one death during exercise per year for every 18,000 healthy
middle-aged men (Siscovick) and only one death per 700,000 hours of
exercise (Thompson). These cardiac events, heart attack and sudden
death, are most often produced by a blood clot or thrombosis that
blocks one of the heart's arteries.
Blood Coagulation As A Risk Factor
heart attacks or strokes are associated with a blocked artery. In some
cases a blood clot may cause or complete the blockage, leading to a
cardiovascular event. People with cardiovascular disease typically have
an increased tendency to form blood clots, and a decreased ability to
dissolve clots before they can do any damage.
ability to dissolve clots (known as fibrinolysis) has been associated
with risk of heart attack, stroke, and overall mortality and is
therefore an important but less recognized risk factor. In fact, some
persons with fairly advanced atheroclerosis manage to escape having a
heart attack or stroke possibly because of their ability to dissolve
blood clots. This points out the importance of normalizing this risk
factor for all populations.
Factors That Affect Blood Coagulation And Fibrinolysis
like other cardiovascular disease risk factors, impaired fibrinolysis
is not only linked with the disease, but with other risk factors. Age,
high blood pressure, cholesterol levels, diabetes, smoking, and obesity
are all cardiovascular risk factors associated with impaired
fibrinolysis. In addition, post-menopausal women have impaired
fibrinolysis, partly explaining the increased risk for cardiovascular
events in this population. Heavy alcohol consumption can adversely
affect fibrinolysis, thereby increasing the likelihood of a blood clot.
Finally, much like other cardiovascular disease risk factors, genetics
or inherited predisposition has a large influence on fibrinolysis.
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