Chapter 0: Introduction to Exercise Physiology

By studying this chapter, you should be able to do the following:

1. Describe the scope of exercise physiology as a branch of physiology.

2. Describe the influence of European scientists on the development of exercise physiology.

3. Name the three Nobel Prize winners whose research work involved muscle or muscular exercise.

4. Describe the role of the Harvard Fatigue Laboratory in the history of exercise physiology in the United States.

5. Describe factors influencing physical fitness in the United States over the past century.

6. List career options for students majoring in exercise science or kinesiology.

• Brief History of Exercise Physiology 3

  • European Heritage 3

  • Harvard Fatigue Laboratory 4

• Physiology, Physical Fitness, and Health 6

• Physical Education to Exercise Science and Kinesiology 8

• Graduate Study and Research in the Physiology of Exercise 9

• Professional and Scientific Societies and Research Journals 11

  • Training in Research 11

• Careers in Exercise Science and Kinesiology 12

Does one need to have a “genetic gift” of speed to be a world-class runner, or is it all due to training? What happens to your heart rate when you take an exercise test that increases in intensity each minute? What changes occur in your muscles as a result of an endurance-training program that allows you to run at faster speeds over longer distances? What fuel—carbohydrate or fat—is most important when running a marathon? Research in exercise physiology provides answers to these and similar questions.

Physiology is the study of the function of tissues (e.g., muscle, nerve), organs (e.g., heart, lungs), and systems (e.g., cardiovascular). Exercise physiology extends this to evaluate the effect of a single bout of exercise (acute exercise) and repeated bouts of exercise (i.e., training programs) on these tissues, organs, and systems. In addition, the responses to acute exercise and training may be studied at high altitude or in extremes of heat and humidity to determine the impact of these environmental factors on our ability to respond and adapt to exercise. Finally, studies are conducted on young and old individuals, both healthy and those with disease, to understand the role of exercise in the prevention of or rehabilitation from various chronic diseases.

Consistent with this perspective, we go beyond simple statements of fact to show how information about the physiology of exercise is applied to the prevention of and rehabilitation from coronary heart disease, the performances of elite athletes, and the ability of a person to work in adverse environments such as high altitudes. The acceptance of terms such as sports physiology, sports nutrition, and sports medicine is evidence of the growth of interest in the application of physiology of exercise to real-world problems. Careers in athletic training, personal-fitness training, cardiac rehabilitation, and strength and conditioning, as well as the traditional fields of physical therapy and medicine, are of interest to students studying exercise physiology. We will expand on career opportunities later in the chapter.

In this chapter, we provide a brief history of exercise physiology to help you understand where we have been and where we are going. In addition, throughout the text a variety of scientists and clinicians are highlighted in a historical context as subject matter is presented (i.e., muscle, cardiovascular responses, altitude). We hope that by linking a person to a major accomplishment within the context of a chapter, history will come alive and be of interest to you.

The history of exercise physiology represents a global perspective involving scientists from many different countries. In this section, we begin with the impact European scientists have had on the development of exercise physiology. We then describe the role of the Harvard Fatigue Laboratory in the growth of exercise physiology in this country.

European Heritage

A good starting place to discuss the history of exercise physiology in the United States is in Europe. Three scientists, A. V. Hill of Britain, August Krogh of Denmark, and Otto Meyerhof of Germany, received Nobel Prizes for research on muscle or muscular exercise (13). Hill and Meyerhof shared the Nobel Prize in Physiology or Medicine in 1922. Hill was recognized for his precise measurements of heat production during muscle contraction and recovery, and Meyerhof for his discovery of the relationship between the consumption of oxygen and the measurement of lactic acid in muscle. Hill was trained as a mathematician before becoming interested in physiology. In addition to his work cited for the Nobel Prize, his studies on humans led to the development of a framework around which we understand the physiological factors related to distance-running performance (6) (see Chap. 19).

Although Krogh received the Nobel Prize for his research on the function of capillary circulation, he had a major impact on numerous areas of investigation. Furthermore, like many productive investigators, his influence was due not only to his own work but to that of his students and colleagues as well. Krogh’s collaboration with Johannes Lindhard resulted in classic studies dealing with carbohydrate and fat metabolism during exercise, and how the cardiovascular and respiratory systems’ responses are controlled during exercise (4). Three students in Krogh’s lab, Erling Asmussen, Erik Hohwü-Christensen, and Marius Nielsen (called “the three musketeers” by Krogh), had a major impact on exercise physiology research throughout the middle of the twentieth century. These investigators, in turn, trained a number of outstanding physiologists, several of whom you will meet throughout this text. The August Krogh Institute in Denmark contains some of the most prominent exercise physiology laboratories in the world. Marie Krogh, his wife, was a noted scientist in her own right and was recognized for her innovative work on measuring the diffusing capacity of the lung. We recommend the biography of the Kroghs written by their daughter, Bodil Schmidt-Nielsen (see Suggested Readings), for those interested in the history of exercise physiology.

Several other European scientists must also be mentioned, not only because of their contributions to the exercise physiology but also because their names are commonly used in a discussion of exercise physiology. J. S. Haldane did some of the original work on the role of CO₂ in the control of breathing. Haldane also developed the respiratory gas analyzer that bears his name (16). C. G. Douglas did pioneering work with Haldane in the role of O₂ and lactic acid in the control of breathing during exercise, including some work conducted at various altitudes. The canvas-and-rubber gas collection bag used for many years in exercise physiology laboratories around the world carries Douglas’s name. A contemporary of Douglas, Christian Bohr of Denmark, did the classic work on how O₂ binds to hemoglobin. The “shift” in the oxygen–hemoglobin dissociation curve due to the addition of CO₂ bears his name (see Chap. 10). Interestingly, it was Krogh who did the actual experiments that enabled Bohr to describe his famous “shift” (4, 16).

Harvard Fatigue Laboratory

A focal point in the history of exercise physiology in the United States is the Harvard Fatigue Laboratory. Professor L. J. Henderson organized the laboratory within the Business School to conduct physiological research on industrial hazards. Dr. David Bruce Dill was the research director from the time the laboratory opened in 1927 until it closed in 1947 (19). Table 0.1 shows that the scientists conducted research in numerous areas, in the laboratory and in the field, and the results of those early studies have been supported over the years. Dill’s classic text, Life, Heat, and Altitude (15), is a recommended reading for any student of exercise and environmental physiology. Much of the careful and precise work of the laboratory was conducted using the now-classic Haldane analyzer for respiratory gas analysis and the van Slyke apparatus for blood-gas analysis. The advent of computer-controlled equipment in the 1980s has made data collection easier but has not improved on the accuracy of measurement (see Fig. 0.1).

The Harvard Fatigue Laboratory attracted doctoral students as well as scientists from other countries. Many of the alumni from the laboratory are recognized in their own right for excellence in research in the physiology of exercise. Two doctoral students, Steven Horvath and Sid Robinson, went on to distinguished careers at the Institute of Environmental Stress in Santa Barbara and Indiana University, respectively.

Foreign “Fellows” included the “three musketeers” mentioned in the previous section (E. Asmussen, E. Hohwü-Christensen, and M. Nielsen) and the Nobel Prize winner August Krogh. These scientists brought new ideas and technology to the lab, participated in laboratory and field studies with other staff members, and published some of the most important work in the exercise physiology between 1930 and 1980. Rudolfo Margaria, from Italy, went on to extend his classic work on oxygen debt and described the energetics of locomotion. Peter F. Scholander, from Norway, gave us his chemical gas analyzer that is a primary method of calibrating tank gas used to standardize electronic gas analyzers (19).

In summary, under the leadership of Dr. D. B. Dill, the Harvard Fatigue Laboratory became a model for research investigations into exercise and environmental physiology, especially as it relates to humans. When the laboratory closed and the staff dispersed, the ideas, techniques, and approaches to scientific inquiry were distributed throughout the world, and with them, Dill’s influence in the area of environmental and exercise physiology. Dr. Dill continued his research outside Boulder City, Nevada, into the 1980s. He died in 1986 at the age of 93.

Progress toward understanding any issue in exercise physiology transcends time, national origin, and scientific training. Solutions to difficult questions require the interaction of scientists from diverse disciplines and professions such as physiology, biochemistry, molecular biology, and medicine. We recommend Exercise Physiology—People and Ideas (see the Suggested Readings) to further your understanding of important historical connections. In this book, internationally known scientists provide a historical treatment of a number of important issues in exercise physiology, with an emphasis on the cross-continent flow of energy and ideas. We highlight several scientists and clinicians with our “Ask the Expert” boxes throughout the text, both to introduce them to you and for them to share their current ideas. In addition, A Look Back—Important People in Science is used to recognize well-known scientists who have influenced our understanding of exercise physiology. In this context, you will get to know those who have gone before and those who are currently leading the charge.

Physical fitness is a popular topic today, and its popularity has been a major factor in motivating college students to pursue careers in physical education, exercise physiology, health education, nutrition, physical therapy, and medicine. In 1980, the Public Health Service listed “physical fitness and exercise” as one of 15 areas of concern related to improving the country’s overall health (32). This was far from a new idea. Similar interests and concerns about physical fitness existed in this country more than 100 years ago. Between the Civil War and the First World War (WWI), physical education was primarily concerned with the development and maintenance of fitness, and many of the leaders in physical education were trained in medicine (14) (p. 5). For example, Dr. Dudley Sargent, hired by Harvard University in 1879, set up a physical training program with individual exercise prescriptions to improve a person’s structure and function to achieve “that prime physical condition called fitness—fitness for work, fitness for play, fitness for anything a man may be called upon to do” (35) (p. 297).

Dr. Sargent was clearly ahead of his time in promoting health-related fitness. Later, war became a primary force driving this country’s interest in physical fitness. Concerns about health and fitness were raised during WWI and WWII when large numbers of draftees failed the induction exams due to mental and physical defects (18) (p. 407). These concerns influenced the type of physical education programs in the schools during these years, making them resemble premilitary training programs (40) (p. 484). Interestingly, whereas stunted growth and being underweight were major reasons for rejecting military recruits in WWII, obesity is the major cause for rejecting recruits today (see “Still Too Fat to Fight” at http://www.missionreadiness.org/2012/still-too-fat-to-fight/).

The present interest in physical activity and health was stimulated in the early 1950s by two major findings: (1) autopsies of young soldiers killed during the Korean War showed that significant coronary artery disease had already developed and (2) Hans Kraus showed that American children performed poorly on a minimal muscular fitness test compared to European children (40) (p. 516). Due to the latter finding, President Eisenhower initiated a conference in 1955 that resulted in the formation of the President’s Council on Youth Fitness. The American Association for Health, Physical Education, and Recreation (AAHPER) supported these activities and in 1957 developed the AAHPER Youth Fitness Test with national norms to be used in physical education programs throughout the country. Before he was inaugurated, President Kennedy expressed his concerns about the nation’s fitness in an article published in Sports Illustrated, called “The Soft American” (24):

During Kennedy’s term, the council’s name was changed to the “President’s Council on Physical Fitness” to highlight the concern for fitness. The name was changed again in the Nixon administration to the “President’s Council on Physical Fitness and Sports,” which supported fitness not only in schools but also in business, industry, and for the general public. The name was most recently changed by President Obama to the “President’s Council on Fitness, Sports, & Nutrition” to focus more attention on the obesity epidemic (see www.fitness.gov). Items in the Youth Fitness Test were changed over the years, and in 1980, the American Alliance for Health, Physical Education, Recreation, and Dance (AAHPERD) published a separate Health-Related Physical Fitness Test Manual (1) to distinguish between “performance testing” (e.g., 50-yard dash) and “fitness testing” (e.g., skinfold thickness). This health-related test battery is consistent with the direction of lifetime fitness programs, being concerned with obesity, cardiorespiratory fitness, and low-back function. A parallel fitness test, Fitnessgram, was developed by The Cooper Institute in 1982, including software to support the scoring and printing of reports (see https://www.cooperinstitute.org/youth/fitnessgram). The President’s Council now recommends that the Fitnessgram be used to evaluate fitness in children. For readers interested in the history of fitness testing in schools, we recommend Morrow et al.’s review in the Suggested Readings.

Paralleling this interest in the physical fitness of youth was the rising concern about the death rate from coronary heart disease in the middle-aged American male population. Epidemiological studies of the health status of the population underscored the fact that degenerative diseases related to poor health habits (e.g., high-fat diet, smoking, inactivity) were responsible for more deaths than the classic infectious and contagious diseases. In 1966, a major symposium highlighted the need for more research in the area of physical activity and health (33). In the 1970s, there was an increase in the use of exercise tests to diagnose heart disease and to aid in the prescription of exercise programs to improve cardiovascular health. Large corporations developed “executive” fitness programs to improve the health status of that high-risk group. While most Americans are now familiar with such programs and some students of exercise physiology seek careers in “corporate fitness,” such programs are not new. In fact, as early as 1923, textbooks such as McKenzie’s Exercise in Education and Medicine (27) showed businessmen participating in a dance exercise class. In short, the idea that regular physical activity is an important part of a healthy lifestyle was “rediscovered.” If any questions remained about the importance of physical activity to health, the publication of the Surgeon General’s Report in 1996 and the appearance of the first U.S. Physical Activity Guidelines in 2008 put them to rest (see “A Closer Look 0.1”).

Undergraduate academic preparation in physical education has changed over the past five decades to reflect the explosion in the knowledge base related to the physiology of exercise, biomechanics, and exercise prescription. This occurred at a time of a perceived reduced need for school-based physical education teachers and an increased need for exercise professionals in the preventive and clinical settings. These factors, as well as others, led some college and university departments to change their names from Physical Education to Exercise Science or Kinesiology. This trend is likely to continue as programs move further away from traditional roots in education and become integrated within colleges of arts and sciences or allied health professions (38). There has been an increase in the number of programs requiring undergraduates to take one year of calculus, chemistry, and physics, and courses in organic chemistry, biochemistry, anatomy, physiology, and nutrition. In many colleges and universities, little difference now exists between the first two years of requirements in a pre-physical therapy or pre-medical track and the track associated with physical education/kinesiology professions. The differences among these tracks lie in the “application” courses that follow. Biomechanics, physiology of exercise, fitness assessment, exercise prescription, strength and conditioning, and so on belong to the physical education/kinesiology track. However, it must again be pointed out that this new trend is but another example of a rediscovery of old roots rather than a revolutionary change. Kroll describes two 4-year professional physical education programs in the 1890s, one at Stanford and the other at Harvard, that were the forerunners of today’s programs (25) (pp. 51–64). They included the detailed scientific work and application courses with clear prerequisites cited. Finally, considerable time was allotted for laboratory work. No doubt, Lagrange’s 1890 text, Physiology of Bodily Exercise (26), served as an important reference source for these students. The expectations and goals of those programs were almost identical to those specified for current kinesiology undergraduate tracks. In fact, one of the aims of the Harvard program was to allow a student to pursue the study of medicine after completing two years of study (25) (p. 61).

While the Harvard Fatigue Laboratory was closing in 1947, the country was on the verge of a tremendous expansion in the number of universities offering graduate study and research opportunities in exercise physiology. A 1950 survey showed that only 16 colleges or universities had research laboratories in departments of physical education (21). By 1966, 151 institutions had research facilities, 58 of them in exercise physiology (40) (p. 526). This expansion was due to the availability of more scientists trained in the research methodology of exercise physiology, the increased number of students attending college due to the GI Bill and student loans, and the increase in federal dollars to improve the research capabilities of universities (12, 38).

“The scholar’s work will be multiplied many fold through the contribution of his students.” This quote, taken from Montoye and Washburn (28, 29), expresses a view that has helped attract researchers and scholars to universities. Evidence to support this quote was presented in the form of genealogical charts of contributors to the Research Quarterly (29). These charts showed the tremendous influence a few people had through their students in the expansion of research in physical education. Probably the best example of this is Thomas K. Cureton, Jr., of the University of Illinois, a central figure in the training of productive researchers in exercise physiology and fitness. The proceedings from a symposium honoring Dr. Cureton in 1969 listed 68 Ph.D. students who completed their work under his direction (17). Although Dr. Cureton’s scholarly record includes hundreds of research articles and dozens of books dealing with physical fitness, the publications of his students in the areas of epidemiology, fitness, cardiac rehabilitation, and exercise physiology represent the “multiplying effect” that students have on a scholar’s productivity. For those who would like to read more about Dr. Cureton, see Berryman’s article (7).

An example of a major university program that can trace its lineage to the Harvard Fatigue Laboratory is found at the Laboratory for Human Performance Research (Noll Laboratory) at Pennsylvania State University (see “A Look Back—Important People in Science”). However, it is clear that excellent research in exercise and environmental physiology is conducted in laboratories other than those that have a tie to the Harvard Fatigue Laboratory. Laboratories are found in physical education/kinesiology departments, physiology departments in medical schools, clinical medicine programs at hospitals, and in independent facilities such as the Cooper Institute for Aerobics Research. The proliferation and specialization of research involving exercise is discussed in the next section.

It should be no surprise that the major issues studied by researchers in exercise physiology have changed over the years. Table 0.2, from Tipton’s look at the 50 years following the closing of the Harvard Fatigue Laboratory, shows the subject matter areas that were studied in considerable detail between 1954 and 1994 (38). A great number of these topics fit into the broad area of systemic physiology or were truly applied physiology issues. Although research continues to take place in most of these areas, Tipton believes that many of the most important questions to be addressed in the future will be answered by those with special training in molecular biology. Baldwin (5) supported Tipton’s viewpoint and provided a summary of important questions dealing with exercise and chronic disease whose answers are linked to functional genomics and proteomics, important new tools for the molecular biologist. However, he also noted the need for increased research to address physical activity and chronic diseases at the lifestyle and behavioral levels. This “integrated” approach, crossing disciplines and technologies, should be reflected in the academic programs educating the next generation of kinesiology students. We recommend the chapters by Tipton (38) and Buskirk and Tipton (12) for those interested in a detailed look at the development of exercise physiology in the United States.

The expansion of interest in exercise physiology and its application to fitness and rehabilitation resulted in an increase in the number of professional societies in which scientists and clinicians could present their work. Prior to 1950, the two major societies concerned with exercise physiology and its application were the American Physiological Society (APS) and the American Association of Health, Physical Education, and Recreation (AAHPER). The need to bring together physicians, physical educators, and physiologists interested in physical activity and health into one professional society resulted in the founding of the American College of Sports Medicine (ACSM) in 1954 (see Berryman’s history of the ACSM in the Suggested Readings). The ACSM now has more than 20,000 members, with 12 regional chapters throughout the country, each holding its own annual meeting to present research, sponsor symposiums, and promote sports medicine. ACSM’s impact also has been enhanced by its regular publication of Guidelines for Exercise Testing and Prescription (2), which reaches a very diverse audience.

The explosion in exercise physiology research over the past 60 years has been accompanied by a dramatic increase in the number of professional and scientific societies and research journals communicating research findings. Table 0.3 provides a brief summary of research journals that publish research in exercise physiology.

Training in Research

One of the clear consequences of this increase in research activity is the degree to which scientists must specialize to compete for research grants and to manage the research literature. Laboratories may focus on neuromuscular physiology, cardiac rehabilitation, or the influence of exercise on bone structure. Graduate students need to specialize earlier in their careers as researchers, and undergraduates must investigate graduate programs very carefully to make sure they meet their career goals (23).

This specialization in research has generated comments about the need to emphasize “basic” research examining the mechanisms underlying a physiological issue rather than “applied” research, which might describe responses of persons to exercise, environmental factors, or nutritional factors. It would appear that both types of research are needed and, to some extent, such a separation is arbitrary. For example, one scientist might study the interaction of exercise intensity and diet on muscle hypertrophy, another may characterize the changes in muscle cell size and contractile protein, a third might study changes in the energetics of muscle contraction relative to cellular enzyme activities, and a fourth might study the gene expression needed to synthesize that contractile protein. Where does “applied” research begin and “basic” research end? In the introduction to his text Human Circulation (34), Loring Rowell provided a quote from T. H. Huxley that bears on this issue:

Solutions to chronic disease problems related to physical inactivity (e.g., type 2 diabetes, obesity) will come from a range of scientific disciplines—from epidemiologists on the one hand (39) to cell biologists on the other (8). We hope that all forms of inquiry are supported by fellow scientists so that present theories related to exercise physiology are continually questioned and modified. Last, we completely agree with the sentiments expressed in a statement ascribed to Arthur B. Otis: “Physiology is a good way to make a living and still have fun” (36).

Over the past 30 years, there has been a sustained growth in career opportunities for those with academic training in exercise science and kinesiology.

These include

• Personal fitness training in private, commercial, worksite, and hospital settings

• Strength and conditioning in commercial, rehabilitative, and sport-related environments

• Cardiac rehabilitation

• Athletic training

• Massage therapy

• Traditional allied health professions (e.g., physical or occupational therapy)

• Medicine (e.g., physician assistant, physician)

For those interested in careers in fitness and cardiac rehabilitation, coursework is not enough—students must develop the requisite skills needed to perform the job. That means that students should be completing practicum and internship experiences under the direction of a professional who can pass along what cannot be taught in a classroom or laboratory. Students should make contact with their advisors early in the program to maximize what can be gained from these experiences. Interested students should read the article by Pierce and Nagle on the internship experience (31). However, more may be needed to realize your career goal.

Those interested in cardiac rehabilitation and athletic training usually pursue graduate study (though there are exceptions) to realize their goals. If that is the case for you, apply early because there are limited spaces in most graduate programs. It is important to note that passing an appropriate certification exam is a normal part of the process to being welcomed into the community of professionals. This is simple within athletic training because there is only one official exam (offered by the National Athletic Training Association’s Board of Certification). In the fitness area, it is much more complicated given the number of certification exams available. If a certification exam requires a one-day workshop with little or no formal coursework and results in a high pass rate, the certification is worthless from a professional’s point of view. It is important to pass the most rigorous and respected certification exams that have, at a minimum, a formal education requirement in an appropriate field. Check out the American College of Sports Medicine (www.acsm.org) and the National Strength and Conditioning Association (https://www.nsca.com/certification/) websites for additional information for certifications that are recognized as being of high quality. If you are interested in a career in physical therapy, as many of our students are, be prepared for stiff competition for the limited number of available seats in these programs. Some undergraduate students even delay applying until they work for a year or do graduate study in an area related to physical therapy. See A Look Back—Important People in Science for someone who was a pioneer in physical therapy and whose journey began in physical education.

Over the past few years, a special initiative, Exercise Is Medicine (http://exerciseismedicine.org), was developed by the American College of Sports Medicine and the American Medical Association to encourage those working in the medical and the allied health professions to routinely promote physical activity to their patients. In addition to that goal, these health professionals need to know where to refer patients when they need more formal support for their physical activity program. For example, physical therapists need to know where to direct their patients after the mandated maximum number of rehabilitation sessions have been completed. Extensive resources for healthcare providers, fitness professionals, the public, and so on are available at the aforementioned website.

Last, but not least, if you are interested in pursuing a career in research so that you can teach and do research at a college or university, you should become involved in research while you are an undergraduate. You might volunteer as a subject for another student’s research project, take course credit to assist your professor in his or her research, or use a summer break to work in a researcher’s lab at another institution. If a particular area of research interests you, do a PubMed search to see who is currently active in the area; this will help you narrow down potential graduate programs. Finally, you also need to get online and determine what the requirements are for admission to the graduate programs you are interested in; this will give you time to take appropriate coursework to meet those requirements.

1. If you are interested in finding new research articles about a topic, for example, “resistance training in women athletes,” don’t use Google. Instead, go to PubMed (www.ncbi.nlm.nih.gov/pubmed) and click PubMed Quick Start Guide to get the basics. Now, insert the phrase in the search box and click Search.

   Finally, select three references that might be of interest to you and send them to your e-mail address using the Send To pull-down menu.

2. Now that you know how to look up research articles on a particular topic, find out where the scientists who did that research are employed. Go to those university (departmental) websites and see what the graduate program requires for admission. If you are interested in pursuing that line of research, contact the professor and see if research or teaching assistantships are available.

3. Go to the Bureau of Labor Statistics Occupational Outlook Handbook (http://www.bls.gov/ooh/) and search on your career interest(s) to obtain estimates of salary, projected needs, degrees required, and so forth. Then, locate the office at your college or university that provides advising support for your interest.

4. Identify the primary scientific meeting your professors attend. Find out if the organization that sponsors that meeting has a membership category for students, how much it costs, and what you would receive (e.g., journals) if you joined.