Over the past four decades, many scientific reports have examined the relationships between physical activity, physical fitness, and cardiovascular health.
Expert panels, convened by organizations such as the centers for disease control and prevention (Cdc), the American College of Sports Medicine (Acsm), and the American Heart Association (Aha),1–3 along with the 1.996 US Surgeon General’s Report on Physical Activity and Health, reinforced scientific evidence linking regular physical activity to various measures of cardiovascular health.
The prevailing view in these reports is that more active or fit individuals tend to develop less coronary heart disease (CHD) than their sedentary counterparts.
If CHD develops in active or fit individuals, it occurs at a later age and tends to be less severe.
As many as 250 000 deaths per year in the United States are attributable to a lack of regular physical activity.
In addition, studies that followed large groups of individuals for many years have documented the protective effects of physical activity for a number of noncardiovascular chronic diseases, such as non insulin-dependent diabetes, hypertension, osteoporosis, and colon cancer.
In contrast, we see a higher rate of cardiovascular events and a higher death rate in those individuals with low levels of physical fitness.
Even midlife increases in physical activity, through change in occupation or recreational activities, are associated with a decrease in mortality.
Despite this evidence, however, the vast majority of adults in the United States remains effectively sedentary; less than one-third of Americans meets the minimal recommendations for activity as outlined by the CDC, ACSM, and AHA expert panels.
The benefits of exercise?
A sedentary lifestyle is one of the five major risk factors (along with high blood pressure, abnormal values for blood lipids, smoking, and obesity) for cardiovascular disease, as outlined by the AHA.
Evidence from many scientific studies shows that reducing these risk factors decreases the chance of having a heart attack or experiencing another cardiac event, such as a stroke, and reduces the possibility of needing a coronary revascularization procedure (bypass surgery or coronary angioplasty).
Regular exercise has a favorable effect on many of the established risk factors for cardiovascular disease.
For example, exercise promotes weight reduction and can help reduce blood pressure.
Exercise can reduce “bad” cholesterol levels in the blood (the low-density lipoprotein [LDL] level), as well as total cholesterol, and can raise the “good” cholesterol (the high-density lipoprotein level [HDL]).
In diabetic patients, regular activity favorably affects the body’s ability to use insulin to control glucose levels in the blood.
Although the effect of an exercise program on any single risk factor may generally be small, the effect of continued, moderate exercise on overall cardiovascular risk, when combined with other lifestyle modifications (such as proper nutrition, smoking cessation,and medication use), can be dramatic.
Benefits of making exercise on cardiovascular risk factors
Increase in exercise tolerance : reduction in body weight and in blood pressure,reduction in bad (LDL and total) cholesterolm,increase in good (HDL) cholesterol,increase in insulin sensitivity.
There are a number of physiological benefits of exercise; two examples are improvements in muscular function and strength and improvement in the body’s ability to take in and use oxygen (maximal oxygen consumption or aerobic capacity).
As one’s ability to transport and use oxygen improves, regular daily activities can be performed with less fatigue.
This is particularly important for patients with cardiovascular disease, whose exercise capacity is typically lower than that of healthy individuals.
There is also evidence that exercise training improves the capacity of the blood vessels to dilate in response to exercise or hormones, consistent with better vascular wall function and an improved ability to provide oxygen to the muscles during exercise.
Studies measuring muscular strength and flexibility before and after exercise programs suggest that there are improvements in bone health and ability to perform daily activities, as well as a lower likelihood of developing back pain and of disability, particularly in older age groups.
Patients with newly diagnosed heart disease who participate in an exercise program report an earlier return to work and improvements in other measures of quality of life, such as more self-confidence, lower stress, and less anxiety.
Importantly, by combining controlled studies, researchers have found that for heart attack patients who participated in a formal exercise program, the death rate is reduced by 20% to 25%.
This is strong evidence in support of physical activity for patients with heart disease.
Although the benefits of exercise are unquestionable, it should be noted that exercise programs alone for patients with heart disease have not convincingly shown improvement in the heart’s pumping ability or the diameter of the coronary vessels that supply oxygen to the heart muscle.
How much exercise is enough?
In 1.996, the release of the Surgeon General’s Report on Physical Activity and Health provided a springboard for the largest government effort to date to promote physical activity among Americans.
This historic turning point redefined exercise as a key component to health promotion and disease prevention, and on the basis of this report, the Federal government mounted a multi-year educational campaign.
The Surgeon General’s Report, a joint Cdc/Acsm consensus statement, and a National Institutes of Health report agreed that the benefits mentioned above will generally occur by engaging in at least 30 minutes of modest activity on most, preferably all, days of the week.
Modest activity is defined as any activity that is similar in intensity to brisk walking at a rate of about three to four miles per hour.
These activities can include any other form of occupational or recreational activity that is dynamic in nature and of similar intensity, such as cycling, yard work, and swimming.
This amount of exercise equates to approximately five to seven 30-minute sessions per week at an intensity equivalent to 3 to 6 Mets (multiples of the resting metabolic rate*), or approximately 600 to 1.200 calories expended per week.
Note that the specific phrase “…30 minutes of accumulated activity…” is used in the above-mentioned reports.
It has been shown that repeated intermittent or shorter bouts of activity (such as 10 minutes) that include occupational and recreational activity or the tasks of daily living have similar cardiovascular and other health benefits if performed at the moderate intensity level with an accumulated duration of at least 30 minutes per day.
People who already meet these standards will receive additional benefits from more vigorous activity.
Many of the studies documenting the benefits of exercise typically use programs consisting of 30 to 60 minutes of continuous exercise 3 days per week at an intensity corresponding to 60% to 75% of the individual’s heart rate reserve.
It is not usually necessary, however, for healthy adults to measure heart rate diligently because substantial health benefits can occur through modest levels of daily activity, irrespective of the specific exercise intensity.
In fact, researchers estimate that as much as a 30% to 40% reduction in cardiovascular events is possible if most Americans were simply to meet the government recommendations for activity.
Recommendation for physical activity from the Cdc/Acsm consensus statement and surgeon general’s report
Every American adult should participate in thirty minutes or more of moderate intensity activity on most, and preferably all, days of the week.
Moderate activities : activities comparable to walking briskly at about 3 to 4 miles per hour; may include wide variety of occupational or recreational activities, including yard work, household tasks, cycling, swimming, etc.
30 of moderate activity daily equates to 600 to 1.200 calories of energy expended per week.
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