Physical activity is body movement that raises the energy that a person uses above a baseline level. Exercise is a form of physical activity that is done to maintain and improve health. By contrast, continued physical inactivity places a person at risk of such conditions as heart disease, diabetes, cancer, and strokes. In fact, the term physical inactivity is used to describe the lifestyle of individuals who are at activity levels below a recommended level to maintain good health. For instance, the American Heart Association recommends that American adults get from 30 to 60 minutes of aerobic exercise three to four times each week. If an individual, for example, is identified as only getting 15 minutes of aerobic exercise twice each week, then that person would not meet this stated recommended level and would be described as physically inactive.
The Chinese philosopher Confucius, who lived in the fifth and fourth centuries BCE, recognized the relationship between regular physical activity and good health. He saw the connection between inactivity and conditions then known as organ malfunctions and internal stoppages. In the modern medical community, those conditions are recognizable as heart disease and diabetes, respectively.
In the twenty-first century, the relationship between exercise and activity is widely accepted. However, for various reasons, many people are inactive and overweight or obese (excessively overweight).
The National Health Interview Survey, 2015 was conducted by the National Center for Health Statistics (HCHS), a part of the Centers for Disease Control and Prevention (CDC). As of December 2016, only earlyrelease data were available from the survey. The following data had been released:
The 2008 Guidelines recommend that children do at least 60 minutes of aerobic physical activity each day. However, according to the 2009 Survey (the 2015 early-release Survey did not contain data for children), only 18% of students in grades nine through 12 met that recommendation in 2007. Although daily, quality physical education in schools could help students meet that goal, just 3% of students attended daily physical education classes, according to the CDC.
Physical inactivity is among the factors that place individuals at risk of obesity-related diseases and conditions, according to the National Heart, Lung, and Blood Institute. Other risk factors include high blood pressure and the waist circumference. If most of the fat is around the abdomen instead of the hips, there is a risk for heart disease and type 2 diabetes. This risk increases when the waist size is greater than 35 in. (88.8 cm) for women and greater than 40 in. (101.6 cm) for men.
The body mass index (BMI) is generally used to determine if a person is overweight or obese. The BMI is based on a formula that takes into account a person's height and weight. An underweight adult has a BMI below 18.5; the normal weight ranges from 18.5 to 24.9; a person with a BMI of 25.0 to 29.9 is overweight; and an individual with a BMI of 30.0 or higher is obese. Weight gain is caused when people consume more calories than they use for activities. Calories from food provide the energy that the body uses for all activities, including exercise. Unused calories accumulate in the body and are stored as fat.
Obesity is considered an epidemic in the United States, where the condition is overtaking smoking as the leading cause of preventable death. According to 2013–2014 data provided by the CDC (and updated in 2016), in the United States,
Physical inactivity is often referred to as a sedentary lifestyle, one in which a person does little or no physical activity. Life in the twenty-first century often means that adults work long hours; however, oftentimes those hours are spent sitting behind a desk or at other stationary activities.
Many children are less physically active than their parents were at the same age. Some schools cut physical education programs, and only athletes who play team sports have the opportunity to exercise. Whereas at one time, children habitually walked to and from school; now more typically, they are driven in a school bus or a parent's car.
In addition, children and adults may be exhausted when they get home. They may not realize that exercise helps to energize them. Instead, they may feel that they do not have the energy or free time to exercise.
Children between the ages of eight and 18 years spend an average of 7.5 hours each day using entertainment media such as TV, computers, video games, cell phones, and movies. Television viewing accounts for 4.5 hours of that time, according to the CDC. In addition, children between the ages of six months to less than six years watch TV or videos for about one hour and 57 minutes each day.
The rise in inactivity and obesity prompted the HHS to publish the 2008 Physical Activity Guidelines for Americans. The Guidelines included recommendations for time spent doing moderate-intensity and vigorous-intensity physical activities.
Intensity was defined in the Guidelines as absolute and relative intensities. The Guidelines defined moderate-intensity physical activity on the absolute scale as an activity performed at 3.0 to 5.9 times the intensity of rest. On the relative scale, moderate-intensity physical activity usually ranked a 5 or 6 on the scale of 0 to 10.
The absolute intensity of aerobic exercise was usually measured as the rate that energy was expended. Methods of measuring this include the calories per minute expended or by the metabolic equivalent (MET). The baseline of 1 MET is the rate of energy used when the person is at rest. Another way to measure this amount is by the rate of an activity such as walking two miles (3.2 kilometers) in an hour or running four miles (6.4 kilometers) in an hour.
Resistance activity or exercise can be expressed as the amount of weight lifted or moved.
Relative intensity is based on the person's exercise capacity. For aerobic exercise, this can be expressed as a percent of a person's aerobic capacity or as a percent of the individual's measured or estimated maximum heart rate. It also can be expressed subjectively as an index of how hard individuals feel they exercised.
Most federal recommendations for physical activity are issued by age group.
CHILDREN AND ADOLESCENTS. Children and adolescents between the ages of six and 17 years should do one hour or more of physical activity every day. Most of the hour should involve moderate- or vigorousintensity aerobic physical activity. Children and adolescents should do a vigorous-intensity activity on at least three days in a week and muscle-strengthening and bone-strengthening activity on at least three days.
Children and adolescents with disabilities should meet the guidelines for their age group or do as much activity as their condition allows.
ADULTS. Each week, adults between the ages of 18 and 64 years should do two hours and 30 minutes of moderate-intensity or one hour and 15 minutes of vigorous-intensity aerobic physical activity. Another option is to do an equivalent combination of moderate- and vigorous-intensity activity. Aerobic activity should be performed in episodes of at least 10 minutes. It is preferable to spread this activity through the week.
Additional health benefits are gained by increasing the weekly schedule to five hours of moderateintensity aerobic activity, two hours and 30 minutes a week of vigorous-intensity activity, or an equivalent combination of both intensities.
Adults should also do muscle-strengthening activities two or more days each week. These should involve all major muscle groups.
Adults with disabilities follow the adult guidelines. If this is not possible, these persons should be as physically active as their disability allows.
OLDER ADULTS AGE 65 YEARS AND OLDER. Older adults follow the adult guidelines. If this is not possible because of a health condition, older adults should be as physically active as possible. Older adults should do exercises that maintain or improve balance as they are typically at risk of falling.
PREGNANT AND POSTPARTUM WOMEN. Healthy pregnant and postpartum women who do not already engage in vigorous-intensity physical activity should get at least two hours and 30 minutes of moderateintensity aerobic activity each week. It is preferred to spread the amount of exercise throughout the week. Women who regularly engage in vigorous-intensity aerobic activity or high amounts of activity may continue their activities unless advised not do so by their doctor. Women should consult their healthcare provider about their activity level throughout their pregnancy.
Individuals can lose weight by reducing the calories consumed, but regular exercise is necessary for functions that include heart health and building and maintaining bones and muscles. Different types of physical activities, weight-bearing, aerobic, and musclestrengthening exercises, provide specific benefits to the body. Some activities such as walking and dancing are both weight-bearing and aerobic exercises.
Bones grow from birth through early adulthood, and weight-bearing exercises contribute to bone health. Exercises such as walking, jogging, dancing, and climbing help to build strong bones and maintain bone density (thickness) in adults. When individuals stop exercising, bones begin to thin. Bone mass decreases as a person ages, and exercising helps prevent bone loss and the risk of osteoporosis.
Aerobic exercise involves repetitive movements of large muscles, including those in the legs. The movements are of a specific intensity and are done for a specific amount of time. The intensity and time exercising force the heart and lungs to work harder during activities such as walking briskly, running, bicycling, and swimming.
One measure of the intensity is the target heart rate. This is the rate that the heart should pump during exercise to achieve the maximum cardiovascular benefit. The rate is based on a percentage of the maximum heart rate, and the maximum is based on various factors, including age and fitness level.
Muscle-strengthening exercises are also known as muscle toning, strength training, and resistance training. Muscles can be exercised by individuals doing push-ups and other exercises that use the body weight or using equipment such as hand-held weights, resistance bands, and weight machines.
These activities increase muscle strength, power, endurance, and mass. When a person gains muscle, the body burns more calories, which makes it easier to control excess body fat.
The exercises also help to strengthen bones and reduce the risk of injury. Other benefits include better control of balance, which becomes an issue as people age. Aging also brings a loss of muscle mass, and weight-training exercises help to preserve muscle.
The numerous health benefits associated with regular physical activity and maintaining a healthy weight include reducing the risk for a heart attack and conditions such as diabetes, high blood pressure, stroke, and some cancers. Physical activity also lowers the risk of an early death.
Diabetes is a chronic (lifelong) condition involving high levels of sugar in the blood. Type 1 diabetes usually develops in children and adolescents. It occurs when the pancreas produces little or no insulin. Type 2 diabetes occurs typically in adults when the pancreas fails to make enough insulin or does not use the insulin correctly.
Blood pressure refers to the force of blood pushing against the walls of the arteries as the heart pumps blood. The pressure is measured as systolic and diastolic. Systolic is the blood pressure when the heart beats while pumping blood. Diastolic is the pressure when the heart is at rest between beats. The measurements are expressed with the systolic reading above the diastolic. A reading of 120/80 is just above normal and is classified as prehypertension. Hypertension, high blood pressure, is defined as 140/90. High blood pressure increases the risk for a heart attack, stroke, and kidney and eye damage.
A heart attack is caused when blood flow to the heart muscle is blocked. This may be caused by a blood clot. Depending on the duration of the blockage, the muscle is damaged or dies. A stroke is the interruption of the blood supply to any part of the brain.
Cancer is characterized by the abnormal growth of cells. There are more than 100 types of cancer, and physical activity helps reduce the risk of breast and colon cancers.
See also Body mass index ; Calories .
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American Council on Exercise, 4851 Paramount Dr., San Diego, CA, 92123, (888) 825-3636, http://www.fitness.gov .
National Coalition for Promoting Physical Activity, 1150 Connecticut Ave. NW, Ste. 300, Washington, DC, 20036, http://www.ncppa.org .
President's Council on Fitness, Sports & Nutrition, 1101 Wootton Pkwy., Ste. 560, Rockville, MD, 20852, (240) 276-9567, Fax: (240) 276-9860, email@example.com, http://www.fitness.gov .
Shape America (Society of Health and Physical Educators), 1900 Association Dr., Reston, VA, 20191-1598, (703) 476-9527, (800) 213-7193, http://www.shapeamerica.org .
Revised by William A. Atkins, BB, BS, MBA