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Physical Activity and Disease Prevention: Past, Present, and Future

2003; Lippincott Williams & Wilkins; Volume: 31; Issue: 3 Linguagem: Inglês

10.1097/00003677-200307000-00001

1538-3008

William L. Haskell,

Cardiovascular and exercise physiology

To commemorate a year of celebration for its 50th Annual Meeting in May 2003 and its 50th anniversary as an organization in 2004, the American College of Sports Medicine and Exercise and Sport Sciences Reviews is pleased to publish personal historical perspectives from leading sports medicine and exercise science professionals. This article is one in a series of articles based on the impact ACSM and ESSR has had on the fields and disciplines covered in this journal. Over the 50-year history of the American College of Sports Medicine (ACSM), the discipline of physical activity and health has grown from a relatively minor consideration within the health and medical professions to becoming a major component of chronic disease prevention and treatment. Although we know that a sedentary way of life can lead to numerous negative health consequences, there is still a great deal to learn about the benefits and risks of various activity regimens for specific populations and how best to reverse the technology-driven reductions in daily activity that continue to occur. The following commentary on the development of the discipline of physical activity and health and its relationship to the evolution of ACSM are my personal musings and are not intended as a historical treatise on this topic. Also, not included here is a discussion of the substantial conceptualization and research on exercise training, exercise physiology, and health benefits of exercise that occurred before the early 1950s. The development of exercise physiology and physical performance research that has occurred over the past 50 years will be covered in future issues of this publication by several very able colleagues. At about the same time that ACSM was being established, Professor Jeremy Morris in England published the first series of systematic studies presenting and supporting the hypothesis that vigorous physical activity, such as walking up and down the stairs of the double-decker buses in London, contributed to a lower mortality from coronary heart disease (CHD). Morris and colleagues followed these initial reports with other quantitative analyses supporting this hypothesis, and confirming reports from other occupational studies began to appear in the medical literature. During this same period, investigators involved with ACSM were studying health-related outcomes derived from exercise training in healthy youths and adults. Most studies were of short duration (10 to 12 wk—no longer than a university quarter or semester) involving college students performing vigorous exercise. Also, it was discovered that after acute myocardial infarction, patients did better clinically with "arm chair" exercise than bed rest. This was the era of Dr. Hans Kraus and his campaign against "hypokinetic" diseases. In the 1960s, additional epidemiologic observations were published demonstrating that more active men had lower CHD or cardiovascular disease (CVD) mortality rates than their sedentary counterparts. Important observations included those on San Francisco longshoremen, college alumni, and U.S. railroad workers. ACSM members and their colleagues were reporting the effects of exercise training on cardiovascular risk factors such as cholesterol, blood pressure, and cardiovascular function. It was during the 1960s that visionaries, such as Herman Hellerstein and Nanette Wenger, began carefully to exercise patients who had experienced myocardial infarction and to develop inpatient and outpatient cardiac rehabilitation programs. A 3-year physical activity and ischemic heart disease planning grant in the late 1960s funded by the U.S. Public Health Service (USPHS) provided a national forum for developing research protocols to investigate physical activity and CHD prevention. The Aerobics exercise program was developed for the U.S. Air Force and general public. By the early 1970s, sufficient research data and clinical experience had been obtained about the cardiovascular benefits of exercise for the American Heart Association to publish guidelines on exercise for both the general public as well as patients with CVD (1975). Data from observational and experimental studies continued to help define the various health benefits of exercise. A number of investigators published data from cross-sectional and exercise training studies on CVD risk factors such as plasma lipids and lipoproteins. At Washington University in St. Louis, John Holloszy, along with a very productive group of postdoctoral fellows, was conducting highly innovative research on skeletal muscle function and structure, especially in the area of carbohydrate metabolism. This research contributed to our understanding of the potential role of exercise in the prevention and treatment of insulin resistance and type 2 diabetes. Also at this time, interested members of ACSM began to meet to develop a certification program for exercise professionals involved in exercise testing and training. This effort was headed by several leaders in ACSM and has been one of its most influential and successful programs over the past 30 years. This committee was responsible for development of the ACSM Guidelines for Exercise Testing and Prescription that have been instrumental in setting standards for use of exercise in health promotion and disease management throughout the world. The sixth edition of these guidelines was published in 2000. Another major contribution by ACSM was the publication of the first position stand on physical activity and health (1978). This document formed the basis of most health-oriented exercise training recommendations for the general public for the next decade. This document was revised in 1992 and again in 1998. In the 1980s, research examining the effects of physical activity on health-related outcomes rapidly expanded. Epidemiologists continued to demonstrate that both inactivity and low levels of cardiorespiratory fitness were associated with increased mortality from CVD and all other causes. A series of important papers from the College Alumni Study and the first of a large number of valuable publications on fitness and health were published using the Aerobics Center Longitudinal Study database. The risks of exercise, especially regarding its potential to precipitate sudden cardiac death, were a concern and a topic of substantial consideration by clinicians and the public. However, various studies demonstrated that, by using guidelines published by ACSM and AHA, exercise training by patients with CHD was safe. Also, several community-based studies demonstrated that during vigorous exercise such as jogging, sudden cardiac death was substantially increased but the net benefit of such exercise was an overall lower CVD risk. In 1988, a landmark consensus conference on exercise, fitness and health was held in Toronto that produced a comprehensive review of available scientific evidence on this topic. Major shifts in the paradigm from one of "exercise training for enhancing performance" to that of "physical activity for enhancing health" begin to take place in the early 1990s. In 1992, the American Heart Association added "sedentary lifestyle" to cigarette smoking, hypertension, and hypercholesterolemia as a major risk factor for CHD. Several meetings hosted by the CDC and ACSM led to the publication of new public health recommendations for physical activity and health in 1995. These recommendations encouraged adults to perform moderate intensity exercise for 30 min or more on most, and preferably all, days. The idea of "accumulation" was introduced in these recommendations, indicating that the goal of 30 or more min of daily exercise could be met by performing multiple bouts of exercise, each being at least 8 to 10 min in duration. These and other recommendations by the National Heart, Lung, and Blood Institute (NHLBI) and the Surgeon General also moved the promotion of physical activity for health from a "clinical" model to more of a "public health" model, where less clinical screening was recommended as well as less medical monitoring of the activity. Reducing the intensity component of the recommendations and increasing the frequency component facilitated this shift. These recommendations raised a number of issues about the required exercise regimen needed for various health outcomes and has resulted in a significant amount of new research being published on issues of dose response. Much of this research has supported the general recommendations made in 1995. However, the shape of the dose-response relations throughout the full range of exercise intensity and the amount of exercise required for specific health outcomes is still open to question. During this period, a number of studies were published establishing an inverse relationship between the amount of habitual activity performed and the development of type 2 diabetes, osteoporosis, and mortality from selected site-specific cancers for women as well as men. Over the past decade, the importance of obesity as a major public health problem has received substantial attention. The contribution that a reduction in exercise-induced caloric expenditure has played in this obesity epidemic appears to be important but not well understood. Despite recent guidelines directed at obesity prevention and weight loss published by the World Health Organization, National Institutes of Health, and the National Academy of Sciences, much research is needed on the biology and psychology of physical activity and obesity. In addition to the role of physical activity in obesity prevention and weight loss, consideration needs to be given to the numerous health benefits derived from physical activity and physical fitness independent of any weight loss effects. Very important have been the recent series of studies showing that persons at high risk of developing type 2 diabetes can reduce their risk by more than 50% by very achievable changes in physical activity, nutrition, and body weight. As we move forward, investigators working together in all the exercise-related sciences will continue to contribute to our understanding of the causal links between activity and health, the benefits of specific activity profiles, and the determinants of a physically active lifestyle.