Exercise
Diane Treat-Jacobson
Ulf G. Bronäs
Dereck Salisbury
Exercise is well recognized as a lifelong endeavor essential for energetic, active, and healthy living. In large, longitudinal studies in the United States and elsewhere it has been established that morbidity and mortality are reduced in physically fit individuals, compared with sedentary individuals (Samitz, Egger, & Zwahlen, 2011). Although the research supporting the benefits of exercise is substantial, it is often overlooked in the practice of conventional Western medicine.
Exercise, either alone or as an alternative or complementary therapy, has been linked to many positive physiological and psychological responses, from reduction in the stress response to an increased sense of well-being (Ehrman, Gordon, Visich, & Keteyian, 2008). Surprisingly, despite the tremendous benefits of exercise, it is an activity largely ignored by the general population. Indeed, in 1996 the U.S. Surgeon General issued a report identifying millions of inactive Americans as being at risk for a wide range of chronic diseases and ailments, including coronary heart disease (CHD), adult-onset diabetes, colon cancer, hip fractures, hypertension, and obesity. Since then, there have been numerous updates to that report. The U.S. Department of Health and Human Services (USDHHS) publication Healthy People 2020 (USDHHS-PAAC, 2008) continues to specify several objectives for improving health, including physical activity and exercise. These include reducing the percentage of adults who do not participate in any physical activity; increasing the percentage of adults who engage in moderate physical activity on most days of the week; and increasing the percentage of adults participating in vigorous exercise, as well as exercises to improve strength and flexibility. The physical activity
objectives in Healthy People 2020 reflect the strong state of science supporting the health benefit of exercise as indicated by the Physical Activity Guidelines Advisory Committee (USDHHS-PAAC, 2008). There are additional objectives related to physical activity and exercise habits of children and adolescents, including goals to increase participation in daily school physical education classes, increase physical activity in childcare settings, and reduce television and computer usage. The alarmingly low percentage of children participating in physical activity in school and outside of school (less than 27%) is reportedly contributing to the nation’s growing childhood obesity problem (National Research Council, 2011).
objectives in Healthy People 2020 reflect the strong state of science supporting the health benefit of exercise as indicated by the Physical Activity Guidelines Advisory Committee (USDHHS-PAAC, 2008). There are additional objectives related to physical activity and exercise habits of children and adolescents, including goals to increase participation in daily school physical education classes, increase physical activity in childcare settings, and reduce television and computer usage. The alarmingly low percentage of children participating in physical activity in school and outside of school (less than 27%) is reportedly contributing to the nation’s growing childhood obesity problem (National Research Council, 2011).
In 2007, the American Heart Association (AHA) and the American College of Sports Medicine (ACSM) issued several updates (Haskell et al., 2007; Nelson et al., 2007; Williams et al., 2007) to the Surgeon General’s 1996 guidelines. This was followed in 2008 by a report and revised guidelines from the USDHHS Physical Activity Advisory Committee (USDHHS-PAAC, 2008), and again in 2011 by the ACSM (Garber et al., 2011). These updated guidelines are based on new data from several largescale trials completed since the 1996 report. It is important to recognize the role of exercise as a component of good health. Exercise must be an integral part of one’s personal lifestyle if it is to have optimum effects. During the past few decades, there has been an increase in the popularity of non-Western styles of exercise and physical activity, such as Qigong and the related movements in yoga and Tai Chi. These forms of exercise and physical activity also build on meditative moments and, as such, may provide a more enjoyable form of physical activity for older adults than walking exercise.
Maintaining physical fitness should be enjoyable and rewarding for persons of all ages and can contribute significantly to extending longevity and improving quality of life. Nurses’ knowledge of exercise and its application in multiple populations will assist in the delivery of expert nursing care. This chapter discusses the definition, physiological basis, and application of exercise as a nursing intervention in a variety of populations, along with specific cultural applications.
DEFINITION
Physical activity is defined as “any bodily movement produced by skeletal muscles that results in caloric expenditure” (American College of Sports Medicine, 2006). Definitions of exercise are complex and vary according to scientific discipline; however, they all incorporate physical activity into their descriptions. Exercise is commonly considered to be a planned, recurring subset of physical activity that results in physical fitness, a term used to describe cardiorespiratory fitness, muscle strength, body
composition, and flexibility related to the ability of a person to perform physical activity (Thompson et al., 2003).
composition, and flexibility related to the ability of a person to perform physical activity (Thompson et al., 2003).
Exercise is commonly classified according to the rate of energy expenditure, which is expressed in either absolute terms as metabolic equivalents (METs) or in relative terms according to what percentage of maximal heart rate or maximal oxygen consumption is achieved (Astrand, Rodahl, Dahl, & Stromme, 2004; Thompson et al., 2003). Exercise is aerobic when the energy demand by the working muscles is supplied by aerobic ATP (adenosine triphosphate) production as allowed by inspired oxygen and mitochondrial enzymatic capacity (Astrand et al., 2004). In general, aerobic exercise increases demand on the respiratory, cardiovascular, and musculoskeletal systems. Sustained periods of work require aerobic metabolism of energy at a level compatible with the body’s oxygen supply capabilities (i.e., oxygen uptake equals oxygen requirements of the tissues). Anaerobic exercise is exercise during which the energy demand exceeds what the body is able to produce through the aerobic process or when the body is performing short bursts of high intensity exercise (Astrand et al., 2004).
SCIENTIFIC BASIS
Better understanding of exercise physiology and the body’s response to various stages of physical activity will assist in the development of exercise programs appropriate for the individual and the goal of the exercise. The response of the body to exercise occurs in stages. The initial response to acute exercise is a withdrawal of parasympathetic stimulation of the heart through the vagus nerve. This results in a rapid increase in heart rate (HR) and cardiac output. The sympathetic stimulation occurs more slowly and becomes a dominant factor once HR is above approximately 100 beats per minute. Sympathetic stimulation is fully completed after approximately 10 seconds to 20 seconds, during which time a large sympathetic outburst occurs and the heart overshoots the rate needed, but then returns to the rate required for increased activity.
The brain stimulates the initial cardiovascular response together with impulses from muscles being exercised, and these impulses are sent to the brain; an increase in HR is initiated and the blood flow is shunted toward the exercising muscles (Astrand et al., 2004). During this phase, there is a sluggish adjustment of respiration and circulation, resulting in an O2 deficit; the initial energy needed by the exercising tissue is mainly fueled by the anaerobic metabolism of creatine phosphate and anaerobic glycolysis (glucose) (Jones & Poole, 2005).
As exercise continues, oxygen consumption (VO2) increases in a linear fashion in relation to the intensity of exercise. The increase in VO2 is caused by an increase in oxygen extraction by the working muscles and an
increase in cardiac output. Oxygen extraction by the working muscle tissues is approximately 80% to 85%, or a threefold increase from rest, in sedentary and moderately active individuals. This is caused by an increase in the number of open capillaries, thereby reducing diffusion distances and increasing capillary blood volume (Fletcher et al., 2001). Cardiac output is increased to meet the increased O2 demands of the working muscle. The increase in cardiac output is caused by increased stroke volume, which is due to an increase in ventricular filling pressure brought on by increased venous return and decreased peripheral resistance offered by the exercising muscles. Together with the withdrawal of parasympathetic stimulation and increases in sympathetic stimulation, the increase in HR further accentuates the increase in cardiac output as well as increased myocardial contractility (from positive inotropic sympathetic impulses to the heart) (Astrand et al., 2004). In normal individuals, cardiac output can increase four to five times, allowing for increased delivery of O2 to exercising muscle beds and facilitating removal of lactate, CO2, and heat. Respiration increases to deliver O2 and to allow for elimination of CO2. Blood pressure increases as a result of increased cardiac output and the sympathetic vasoconstriction of vessels in the nonexercising muscles, viscera, and skin. During this “steady state” exercise phase, O2 uptake equals O2 tissue requirement, aerobic metabolism of glucose and fatty acids occurs, and there is no accumulation of lactic acid.
increase in cardiac output. Oxygen extraction by the working muscle tissues is approximately 80% to 85%, or a threefold increase from rest, in sedentary and moderately active individuals. This is caused by an increase in the number of open capillaries, thereby reducing diffusion distances and increasing capillary blood volume (Fletcher et al., 2001). Cardiac output is increased to meet the increased O2 demands of the working muscle. The increase in cardiac output is caused by increased stroke volume, which is due to an increase in ventricular filling pressure brought on by increased venous return and decreased peripheral resistance offered by the exercising muscles. Together with the withdrawal of parasympathetic stimulation and increases in sympathetic stimulation, the increase in HR further accentuates the increase in cardiac output as well as increased myocardial contractility (from positive inotropic sympathetic impulses to the heart) (Astrand et al., 2004). In normal individuals, cardiac output can increase four to five times, allowing for increased delivery of O2 to exercising muscle beds and facilitating removal of lactate, CO2, and heat. Respiration increases to deliver O2 and to allow for elimination of CO2. Blood pressure increases as a result of increased cardiac output and the sympathetic vasoconstriction of vessels in the nonexercising muscles, viscera, and skin. During this “steady state” exercise phase, O2 uptake equals O2 tissue requirement, aerobic metabolism of glucose and fatty acids occurs, and there is no accumulation of lactic acid.
As exercise becomes more strenuous, there is a shift toward anaerobic metabolism of glucose, resulting in increased production of lactic acid. The anaerobic threshold is a point during exercise at which ventilation abruptly increases despite linear increases in work rate. As exercise goes beyond steady state, the O2 supply does not meet the oxygen requirement, and energy is provided through anaerobic glycolysis and creatine phosphate breakdown. This increases proton release and phosphate accumulation, increasing acidosis (Robergs, Ghiasvand, & Parker, 2004; Westerblad, Allen, & Lannergren, 2002). Shortly beyond the anaerobic threshold, fatigue and dyspnea ensue and work ceases, coinciding with a significant drop in blood glucose levels. Exercise at a level that allows for aerobic metabolism and reduces the need for anaerobic metabolism and reliance on glucose metabolism as the primary fuel may delay onset of these biochemical changes.
Following cessation of exercise, there is a period of rapid decline in oxygen uptake followed by a slow decline toward resting levels. This slow phase of oxygen uptake return is termed excess postexercise oxygen consumption (LaForgia, Withers, & Gore, 2006). During this period, the body attempts to resynthesize used creatine phosphate, remove lactate, restore muscle and blood oxygen stores, decrease body temperature, return to resting levels of HR and BP (blood pressure), and lower circulating catecholamines (Astrand et al., 2004). It is important to facilitate this phase of exercise by performing a 5- to 10-minute cool-down.
INTERVENTION
Healthy People 2020 is a continuing set of initiatives for the United States to achieve by the year 2020 through the use of the National Physical Activity Plan (NPAP). The NPAP aims to create a national culture that supports incorporation of physical activity throughout everyday life, with the objective of improving health, fitness, and quality of life. Updated guidelines from the ACSM and USDHHS-PAAC, affirming the Surgeon General’s 1996 report, specifically state that exercise is considered to be beneficial to health, with a class 1A (highest) evidence base, and that physical activity:
Decreases risk of premature death
Decreases risk of premature death from heart disease
Decreases risk of acquiring type 2 diabetes
Decreases risk of incurring high blood pressure
Decreases high blood pressure in hypertensive individuals
Decreases risk of acquiring colon cancer
Decreases feelings of uneasiness and despair
The updated report further confirms that exercise also
Aids in weight control
Helps in the strengthening and maintenance of muscles, joints, and bones
Assists older adults with balance and mobility
Fosters feelings of psychological well-being
In addition to these benefits, the ACSM (Garber et al., 2011) and the USDHHS-PAAC (USDHHS-PAAC, 2008) have published scientific statements summarizing evidence confirming physical activity as a significant factor in both primary and secondary prevention of cardiovascular disease. There is a relationship between lack of physical activity and development of coronary artery disease and increased cardiovascular mortality (USDHHSPAAC, 2008; Garber et al., 2011). Further, there is evidence that individuals who engage in regular exercise as part of their recovery postmyocardial infarction have improved rates of survival (Kwan & Balady, 2012).
Given that the benefits apply to all age groups across a broad spectrum of health and disease, it is important for nurses to recognize opportunities to promote exercise as a nursing intervention. There are countless activities included under the umbrella of exercise. Finding the activity that fits an individual’s capabilities and that meets the purposes for which exercise is prescribed is key to the success of the intervention. When prescribing an intervention, it is important to take into account the recommended or advisable exercise intensity for the patient population being served.
Evidence suggests that exercise is more likely to be initiated if the individual: (a) recognizes the need to exercise; (b) perceives the exercise to be
beneficial and enjoyable; (c) understands that the exercise has minimal negative aspects, such as expense, time burden, or negative peer pressure; (d) feels capable and safe engaging in the exercise; and (e) has ready access to the activity and can easily fit it into the daily schedule (USDHSS-PAAC, 2008).
beneficial and enjoyable; (c) understands that the exercise has minimal negative aspects, such as expense, time burden, or negative peer pressure; (d) feels capable and safe engaging in the exercise; and (e) has ready access to the activity and can easily fit it into the daily schedule (USDHSS-PAAC, 2008).
Technique
An aerobic exercise session should involve three phases: warming up, aerobic exercise, and cooling down. These phases are designed to allow the body an opportunity to sustain internal equilibrium by gradually adjusting its physiological processes to the stress of exercise and thus maintaining homeostasis. It should be noted that the new guidelines have explicitly stated that, to achieve optimal health benefits, the exercise should be in addition to activities of daily living that are not of moderate intensity or lasting 10 minutes or longer. Further, although resistance training will not be discussed in depth here, the new guidelines recommend that resistance training should be performed on at least 2 nonconsecutive days per week, and should involve 8 to 10 of the major muscle groups and one set of 8 to 12 repetitions at a resistance that causes significant fatigue (ACSM, 2009; USDHHS-PAAC, 2008; Garber et al., 2011).
Warm-Up Phase
The goal of the warm-up is to allow the body time to adapt to the rigors of aerobic exercise. Warming up results in an increase in muscle temperature, a higher need for oxygen to meet the increased demands of the exercising muscles, dilatation of capillaries resulting in increased circulation, adjustments within the neural respiratory center to the demands of exercise, and a shifting of blood flow centrally from the periphery, resulting in increased venous return (Bishop, 2003). In addition, a good warm up increases flexibility and decreases or prevents arrhythmias and ischemic electrocardiographic changes.
Warming-up exercises should be done for 10 minutes, involve all major body parts, and achieve a heart rate within 20 beats per minute of the target HR for the subsequent aerobic exercise. In addition, a good warm-up should incorporate stretching exercises. Stretching exercises are done at a slow, steady pace and help maintain a full range of motion in body joints while strengthening tendons, ligaments, and muscles.
Aerobic Exercise Phase
The aerobic phase of exercise is also known as the stimulus phase. It consists of four essential components: intensity (which is usually measured as the relative percentage of maximal aerobic capacity), frequency, duration, and mode of exercise. The combination of these components determines
the effectiveness of the exercise and is known as the activity dose. The mode of exercise should involve rhythmic, continuous movement of large muscle groups—walking, jogging, cycling, swimming, or cross-country skiing. The frequency should be 5 days per week, with a duration of at least 30 minutes for health benefits, 60 minutes for prevention of weight gain, and 60 minutes to 90 minutes for aiding in weight loss and preventing weight regain following weight loss. The new guidelines explicitly state that achieving weight loss by exercise alone is difficult and therefore recommends that a weight-loss regimen should be a combination of calorie restriction and increased physical activity.
the effectiveness of the exercise and is known as the activity dose. The mode of exercise should involve rhythmic, continuous movement of large muscle groups—walking, jogging, cycling, swimming, or cross-country skiing. The frequency should be 5 days per week, with a duration of at least 30 minutes for health benefits, 60 minutes for prevention of weight gain, and 60 minutes to 90 minutes for aiding in weight loss and preventing weight regain following weight loss. The new guidelines explicitly state that achieving weight loss by exercise alone is difficult and therefore recommends that a weight-loss regimen should be a combination of calorie restriction and increased physical activity.
The updated guidelines further reaffirm that the duration of exercise is cumulative and can be achieved by exercising three times for a minimum of 10 minutes. The intensity can be either moderate or vigorous. If the exercise performed is vigorous, the duration can be shortened to 20 minutes. Moreover, the 2011 guidelines clarify that the moderate and vigorous exercise can be combined to achieve the recommended activity dose per week (Garber et al., 2011). To simplify this concept, the new guidelines recommend using the activity dose of MET x minutes to meet the minimum physical activity recommendations of approximately 500 MET-minutes per week, with a recommended weekly target of 500 MET-minutes to 1,000 MET-minutes per week. To find the specific MET that each activity requires, the reader is encouraged to visit the University of South Carolina’s Prevention Research Center website (prevention.sph.sc.edu/tools/compendium.htm). For individual determination of intensity, the HR range can be used. For most people, physical fitness improvements may be gained with an intensity of exercise sufficient to achieve 55% to 75% of maximal HR. However, the updated guidelines recommend using the MET-minutes method for determination of activity dose (USDHHS-PAAC, 2008; Haskell et al., 2007).
Stay updated, free articles. Join our Telegram channel
Full access? Get Clinical Tree
