Exercise
More than 28 percent of Americans are completely sedentary (they engage in no physical activity), with an additional 60 percent being inadequately active (engaging in less than 30 minutes of activity per day). For those who strive to achieve and maintain a high quality of health, it must be recognized that physical activity is vital to optimal health. This is reaffirmed by numerous studies that have found an association between physical activity, health, longevity, and an improved quality of life. In addition, the number of deaths related to sedentary living or obesity is approximately a half-million per year. Physical activity may impact quality of life in several ways: it can be used to improve self-image and self-esteem, physical wellness , and health.
Participation in physical activity can be beneficial for anyone and can be started during any stage of life. One goal of Healthy People 2010, a set of national health objectives established by the U.S. Department of Health and Human Services, is to increase the number of people who participate in daily physical activity. This activity can take many forms, ranging from a regimented exercise program to daily life activities such as house or yard work, walking a pet, or walking around town to complete errands.
Definition of Terms
Physical activity is a broad term that encompasses all forms of muscle movements. These movements can range from sports to lifestyle activities. Furthermore, exercise can be defined as physical activity that is a planned, structured movement of the body designed to enhance physical fitness. Regimented or purposeful exercise consists of a program that includes twenty to sixty minutes of activity at least three to five days a week. Some examples of this type of activity include walking, running, cycling, or swimming.
Exercise may be classified in one of two categories, anaerobic and aerobic , depending on where energy is derived from. There is a distinct difference between the two, and specific training techniques are used to enhance both. Anaerobic exercise does not require oxygen for energy. This is due to the intensity and duration of anaerobic events, which typically are high intensity and last only a few seconds to a minute or two. These activities range from a tennis serve to an eight-hundred-meter run.
Aerobic exercise does require oxygen for energy. This is observed during exercise that is less intense but of longer duration. This energy system is primarily used during events lasting longer than several minutes, such as a two-mile run or the Tour de France bicycle race. The potential does exist that one can use both systems, as in soccer, where a match requires ninety minutes of continual activity with short intense bursts of effort.
Benefits of Exercise
The American College of Sports Medicine (ACSM), the Centers for Disease Control and Prevention (CDC), and the Surgeon General have all issued statements that recommend placing an emphasis on adopting physical activity into one's lifestyle. Their intention is to make the public more aware of the health benefits associated with increased physical activity, as well as to
![Female rugby players form a lineout, waiting for the ball to be thrown. Rugby can improve both aerobic and anaerobic fitness because, like many sports, it requires steady activity as well as frequent bursts of exertion. [© Kevin Fleming/Corbis. Reproduced by permission.]](../images/nwaz_01_img0088.jpg)
There are numerous benefits associated with regular participation in an aerobic exercise program, including improved cardiovascular and respiratory functioning, reduced coronary artery disease (CAD) risk, and increased quality of life. Beneficial improvements in cardiovascular and respiratory function include an increased ability of exercising muscles to consume oxygen, lowered resting and exercise heart rates, increased stamina, resistance to fatigue , more effective management of diabetes , reduced bone-mineral loss, decreased blood pressure , and increased efficiency of the heart. Although it is recognized that specific exercises can be used for the purpose of increasing strength, muscular endurance, and flexibility, it is important to recognize that cardiovascular exercise has the most dramatic effect on the body. This is because cardiovascular exercise engages large muscle groups in an aerobic manner.
Role of Exercise in Disease Prevention
Studies have shown that exercise can have a direct effect on preventing heart disease , cancer , and other causes of premature death. Furthermore, participation in regular physical activity may reduce the rate of occurrence of these maladies. An inverse relationship exists between disease and exercise, meaning that with increased levels of physical activity there is a decreased prevalence for certain diseases. Currently, there is strong evidence that exercise has powerful effects on mortality, CAD (including blood lipid profiles), and colon cancer. Research has also confirmed that aerobic exercise can reduce high blood pressure , obesity, type II diabetes, and osteoporosis . In addition, stroke and several types of cancer (such as breast, prostate , and lung cancer) can also be reduced with regular physical activity.
Even more important, several of these factors are interrelated. For example, when an individual lowers his or her high blood pressure, the risk for heart disease, stroke, and kidney disease is also reduced. Another example is that exercise favorably alters blood lipid profiles. These profiles include measurements of total cholesterol (TC, complete count of all cholesterol in the blood), high-density lipoprotein cholesterol (HDL-C, the "good" cholesterol), low-density lipoprotein cholesterol (LDL-C, the "bad" cholesterol), and triglycerides (TRG, storage form of energy), which reduce the risk of plaque buildup in the coronary arteries, a sign of CAD.
Exercise Prescription
Adequate physical activity is dependent on having a well-rounded program that encompasses all aspects of improving health and preventing disease. A well-rounded program includes cardiovascular fitness, muscular strength and endurance, flexibility, posture, and maintenance of body composition.
Components of Physical Fitness
Cardiovascular Fitness
The ability of the body to perform prolonged, large-muscle, dynamic exercise at moderate to high levels of intensity. This is dependent on the ability of the heart and lungs to deliver oxygen to the working muscles. As fitness levels improve, the body functions more efficiently and the heart can better withstand the strains of everyday stress.
Muscular Strength
The maximal amount of force a muscle can exert with a single maximal effort. Strong muscles are important for carrying out everyday tasks, such as carrying groceries, doing yard work, and climbing stairs. Muscular strength can help to keep the body in proper alignment, prevent back and leg pain, and provide support for good posture.
Muscular Endurance
The ability of a muscle or group of muscles to perform repetitive contractions over a period of time. Endurance is a key for everyday life activities and operates with muscular endurance to help maintain good posture and prevent back and leg pain. In addition, endurance can enhance performance during sporting events, as well as help an individual cope with everyday stress.
Flexibility
This refers to the range of motion in a joint or group of joints, correlated with muscle length. This component becomes more important as people age and their joints stiffen up, preventing them from doing everyday tasks. Additionally, good range of motion will allow the body to assume more nautral positions to help maintain good posture. Stretching is therefore an important habit to start, as well as continue, as one ages.
Body Composition
The relative proportion of fat-free mass to fat mass in the body. Fat-free mass is composed of muscle, bone, organs, and water, whereas fat is the underlying adipose tissue. Excessive fat is a good predictor of health problems because it is associated with cardiovascular disease, high cholesterol, and high blood pressure. Higher proportions of fat-free mass indicate an increase in muscle, and thus an increased ability to adapt to everyday stress.
The most effective way to participate in a well-rounded program is by following a simple mnemonic device called FITT (Frequency, Intensity, Time, Type). The FITT principle includes how many times a week one should exercise (frequency), how intense the workout should be (intensity), how long the workout is (time), and what modality to use (type of exercise). Modality is dependent primarily on what an individual prefers. This exercise prescription in based on an individual's fitness level when entering the exercise program, and ultimately upon the goals of the individual. For example, an untrained individual who wants to lose weight and likes to walk would be placed on a program of treadmill or outdoor walking (type), for thirty minutes a day (time), three to five times per week (frequency), and of light to moderate intensity (intensity).
A good example of an exercise program would include three stages. The first stage is a warm-up, where one should complete light calisthenics to activate and warm the muscles, immediately followed by stretching, which helps to maintain flexibility. The second stage is the conditioning stage, which consists of cardiovascular work to enhance the function of the heart and lungs and a resistance-training regimen to strengthen and tone major muscle groups, such as the quadriceps, hamstrings, chest, biceps, triceps, back, and abdominals. The final stage consists of a cool down, or reduction in heart rate to resting levels, as well as stretching again, since the greatest modification in flexibility comes from post-exercise stretching.
Maintenance of physical activity is important to maintain a healthy lifestyle. In addition, it is important to follow an exercise regime that will start slow and gradually increase as fitness level and exercise tolerance increases. The key is to complete at least thirty minutes of activity most days of the week in the form of activities that one enjoys, such as walking, jogging, swimming, aerobic dance, biking, skateboarding, or participating in a sport. This will enable an individual to reach the goals of Healthy People 2010, which include improving the quality of life through fitness with the adoption and maintenance of regular exercise and physical activity programs.
SEE ALSO Sports Nutrition .
Robert J. Moffatt Sara A. Chelland
Bibliography
American College of Sports Medicine (2000). ACSM's Guidelines for Exercise Testing and Prescription, 6th edition. Philadelphia: Lippincott, Williams & Wilkins.
Corbin, Charles B.; Lindsey, Ruth; and Welk, Greg (2000). Concepts of Physical Fitness and Wellness: A Comprehensive Lifestyle Approach, 3rd edition. Boston: McGraw-Hill.
McArdle, William D.; Katch, Frank I.; and Katch, Victor L. (2001). Essentials of Exercise Physiology. Philadelphia: Lea & Faber.
Robbins, Gwen; Powers, Debbie; and Burgess, Sharon (2002). A Wellness Way of Life, 5th edition. Boston: McGraw-Hill.
United States Department of Health and Human Services (1996). Physical Activity and Health: A Report of the Surgeon General. Atlanta: U.S. Department of Health and Human Services, Centers for Disease Control and Prevention.
Wallace, Janet P. (2001). "Health Benefits of Exercise and Fitness." In Foundations of Exercise Science, ed. Gary Kamen. Philadelphia: Lippincott, Williams & Wilkins.