Exercise

The concept of exercise encompasses an expansive list of possible activities. In general, exercise may be defined as purposeful physical exertion that significantly increases the activity level in key physiologic systems (i.e., cardiovascular, pulmonary, and skeletal muscle). Exercise is quantified and prescribed by four key parameters: frequency, intensity, time, and type of activity. Although the term exercise is commonly the preferred descriptor of a structured training program (e.g., aerobic or resistance training), any physical exertion that causes a meaningful increase in physiologic activity of the aforementioned systems for a sustained period of time may be considered exercise. In this context, an infant who is crawling and an 85-year-old who is taking a walk in the park are both partaking in exercise. Exercise, or sustained physical movement [Page 808]involving large muscle groups, is achievable across the life span. Another phrase commonly used to describe exercise is physical activity, which, for example, is used by the U.S. government and American Heart Association to describe exercise goals that all should strive to achieve. In this context, exercise and physical activity may be considered interchangeable terms. This entry explains the nature of aerobic and resistance activities and their respective benefits of regular exercise for maintaining and enhancing health and well-being. Next, the alarming worldwide increase in the incidence of noncommunicable diseases (NCDs) such as diabetes and heart failure is described. This entry concludes with a discussion of the need for a health-care system oriented primarily toward preventing chronic NCDs rather than implementing a care plan only after a patient is at serious risk, or already manifesting acute symptoms, of disease.

Maximal exercise capacity characterizes an individual’s highest ability to perform physical work, which can be divided into aerobic (e.g., walking, running, cycling) and resistance (e.g., leg press, bench press) activities. The maximal amount of oxygen that can be consumed during activities such as running or cycling defines aerobic exercise capacity. The maximal amount of force that can be generated by a muscle group during activities such as a bench press or leg press defines strength. There are also submaximal measures of exercise performance from both an aerobic and muscular perspective. These are quantified as the ability to perform exercise for a sustained period of time. As an aerobic example, submaximal performance may be quantified as the time an individual can run on a treadmill at a given speed and incline. An individual’s anaerobic threshold (i.e., a key transition point in muscle metabolism) during this type of exercise dictates submaximal aerobic performance capabilities. From a resistance perspective, submaximal performance may be quantified as the number of repetitions performed on—for example—a leg press at a given resistance. All types of exercise capacity and performance are important to one’s overall health and wellness.

In general, individuals who participate in a regular exercise training program have a higher exercise capacity compared to those who do not. The frequency, intensity, time, and type of exercise training will strongly influence the degree of improvement in exercise capacity. For example, a person who runs 5 times per week at approximately 60% of their maximal capacity generally attains greater improvements in aerobic exercise capacity and submaximal sustained performance compared with someone who runs 3 times per week at 40% of their maximal capacity. There is also a specificity to training; aerobic exercise training improves aerobic exercise performance while resistance training improves muscle strength (i.e., one repetition at a maximal given load) and endurance (i.e., several repetitions at a submaximal load). In healthy individuals, genetic profile, sex, and age are nonmodifiable factors that influence all types of exercise capacity and performance. Genetic profile in combination with exercise training habits determines which individuals have the potential to become elite athletes. In general, exercise capacity peaks in early adulthood and declines as age progresses. The decline in exercise capacity with aging can be significantly attenuated through participation in a lifelong exercise program. In fact, it has been proposed that an individual’s age be categorized by the aerobic exercise capacity of the individual according to established normative values. Recently, the Fitness Registry and the Importance of Exercise: National Database (FRIEND Registry) proposed normative aerobic capacity values across the adult life span in the United States.

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