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.
A sedentary (inactive) lifestyle is one of the top risk factors for heart disease. Fortunately, it’s a risk factor that you can do something about. Regular exercise, especially aerobic exercise, has many benefits. It can:
- Strengthen your heart and cardiovascular system.
- Improve your circulation and help your body use oxygen better.
- Improve your heart failure symptoms.
- Increase energy levels so you can do more activities without becoming tired or short of breath.
- Increase endurance.
- Lower blood pressure.
- Improve muscle tone and strength.
- Improve balance and joint flexibility.
- Strengthen bones.
- Help reduce body fat and help you reach a healthy weight.
- Help reduce stress, tension, anxiety and depression.
- Boost self-image and self-esteem.
- Improve sleep.
- Make you feel more relaxed and rested.
- Make you look fit and feel healthy.
What Are the Benefits of Exercise?
A sedentary lifestyle is one of the 5 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 Regular Exercise on Cardiovascular Risk Factors
- Increase in exercise tolerance
- Reduction in body weight
- Reduction in blood pressure
- Reduction in bad (LDL and total) cholesterol
- Increase in good (HDL) cholesterol
- Increase in insulin sensitivity
There are a number of physiological benefits of exercise; 2 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 1996, 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 3 to 4 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 1200 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.
Physical Fitness and Mortality
One need not be a marathon runner or an elite athlete to derive significant benefits from physical activity. In fact, the Surgeon General’s physical activity recommendations seem surprisingly modest.
One reason for this is that the greatest gains in terms of mortality are achieved when an individual goes from being sedentary to becoming moderately active. Studies show that less is gained when an individual goes from being moderately active to very active.
In a study performed among US veterans, subjects were classified into 5 categories according to fitness level.
The largest gains in terms of mortality were achieved between the lowest fitness group and the next lowest fitness group. The researchers studied 6213 men over a 6-year period and compared the risks of death (after allowing for age adjustment) by gradients of physical fitness.
The Figure shows the relative risks associated with the different categories (1 to 5, lowest to highest) of fitness measured.
Healthy adults who are the least fit have a mortality risk that is 4.5 times that of the most fit. Surprisingly, an individual’s fitness level was a more important predictor of death than established risk factors such as smoking, high blood pressure, high cholesterol, and diabetes.
This study, along with others, underscores the fact that fitness and daily activity levels have a strong influence on the incidence of heart disease and overall mortality.
What Are the Risks of Exercise?
During exercise, there is a transient increase in the risk of having a cardiac-related complication (for example, a heart attack or serious heart rhythm disorder). However, this risk is extremely small.
.For adults without existing heart disease, the risk of a cardiac event or complication ranges between 1 in 400 000–800 000 hours of exercise.
For patients with existing heart disease, an event can occur an average of once in 62 000 hours.2,3 Importantly, the risk of a cardiac event is significantly lower among regular exercisers.
Evidence suggests that a sedentary person’s risk is nearly 50 times higher than the risk for a person who exercises about 5 times per week. Stated simply, individuals who exercise regularly are much less likely to experience a problem during exercise.
Moreover, contrary to popular view, the majority of heart attacks (approximately 90%) occur in the resting state, not during physical activity.
Exercise is therefore considered to be extremely safe.
Nevertheless, it is a good idea to be aware of the warning signs or symptoms that may indicate a problem: chest discomfort (pain or pressure in the chest, jaw, or neck, possibly radiating into the shoulder, arm, or back), unusual shortness of breath, dizziness or light-headedness, and heart rhythm abnormalities (sensations of heart beat skipping, palpitations, or thumping).
If one of these symptoms occurs, medical attention should be sought immediately.
Before starting an exercise program, talk to your doctor about:
- Medication changes. New medications can greatly affect your response to exercise; your doctor can tell you if your normal exercise routine is still safe.
- Heavy lifting. Make sure that lifting or pushing heavy objects and chores such as raking, shoveling, mowing, or scrubbing aren’t off limits. Chores around the house can be tiring for some people; make sure you only do what you are able to do without getting tired.
- Safe exercises. Get the doctor’s approval before you lift weights, use a weight machine, jog, or swim.
What Type of Exercise Is Best?
Exercise can be divided into three basic types:
- Stretching: slow lengthening of the muscles. Stretching the arms and legs before and after exercising helps prepare the muscles for activity and helps prevent injury and muscle strain.
Regular stretching also increases your range of motion and flexibility.
- Cardiovascular or aerobic: steady physical activity using large muscle groups. This type of exercise strengthens the heart and lungs and improves the body’s ability to use oxygen.
Aerobic exercise has the most benefits for your heart. Over time, aerobic exercise can help decrease your heart rate and blood pressure and improve your breathing.
- Strengthening: repeated muscle contractions (tightening) until the muscle becomes tired. For people with heart failure, many strengthening exercises are not recommended
How Should You Begin if You Want to Become More Physically Active?
First, if you currently have heart disease or are over 45 years of age and have 2 or more risk factors (immediate family member with heart disease before age 55, cigarette smoking, high blood pressure, abnormal cholesterol levels, diabetes, sedentary lifestyle, or obesity), you should consult your physician before starting any type of exercise.
Clearly, most people can derive significant benefits from integrating a half hour of moderate activity into their day. If you know you simply cannot or will not set aside a half hour of activity on a given day, then try to work more activities into the day by taking the stairs rather than the elevator, or try walking rather than driving a short distance to the store.
Try to work several shorter periods of activity, such as 10 minutes, into your schedule. The most important thing is to get started.
There is mounting evidence in the scientific literature that physical activity and physical fitness have a powerful influence on a host of chronic diseases, a fact underscored by the recent Surgeon General’s report on Physical Activity and Health.
Reducing the risk of heart disease through greater physical activity could have an enormous impact on health in the United States.