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News Briefs

Exercise Science: More Questions Than Answers

Joyner, Michael J.

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Exercise and Sport Sciences Reviews: October 2005 - Volume 33 - Issue 4 - p 155-156
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OVERVIEW

For the past six years, the News Briefs section of ESSR has tried to highlight emerging ideas in exercise science and occasionally take a look back at the roots of our field. As my term as editor of this section comes to a close, it seems reasonable to take the liberty (or perhaps license) and make a few comments about where exercise science might be headed.

A number of News Briefs over the past six years have focused on issues that are broadly related to exercise (physical activity) and public health. Two general and related topics standout for continued attention. First, we live in an aging society and exercise and physical activity are among the most effective measures available to slow, reverse, and help humans adapt to the loss of physiological function with aging. Second, we live in a world that is experiencing a rapid decline in its overall “metabolic health.” In developed countries there is an epidemic of obesity and the attendant problems with glucose and lipid metabolism along with vascular disease. In developing countries, rapid industrialization is causing the public health nightmares of starvation and infectious disease to be replaced by “Western style” diseases like type II diabetes. As is the case with aging, exercise and physical activity are among the most effective measures available to deal with these problems (2,3).

Along these lines, it seems that a key question that needs more and continued attention is how do we get the average human in the developed world living the average life to increase their daily “dose” of physical activity? Perhaps the message of personal responsibility will only go so far and public health experts, architects, planners, and others will need to work more closely with exercise scientists to begin to build low- and moderate-level physical activity back into everyday life. On an impressionist level, data from highly successful antismoking and traffic safety efforts seem to indicate that approximately one third of the improvements in these areas have been because of “personal responsibility,” and approximately two thirds have been because of more passive measures that have been “built into” the larger public health effort. For example, getting people to wear seat belts has played a critical role in improved traffic safety, but building safer cars and roads has perhaps played a larger role. Likewise, antismoking campaigns directed at individuals have been very helpful, but the banning of cigarette vending machines in many areas has made it more difficult for teenagers to start smoking in the first place. What lessons can be learned from these experiences that will help society win the battle over physical inactivity? Can the “mistakes” that have been made in developed countries be avoided in rapidly developing countries?

A number of News Briefs over the past six years have focused on issues that are broadly related to the basic science of exercise. In this area there are ongoing challenges related to the acute and chronic effects of exercise on issues like muscle blood flow, control of breathing and gas exchange, cardiovascular reflexes, metabolic regulation, muscle fatigue, muscle plasticity, and motor control (to name a few areas). However, it seems to me that in the past few years several newer areas have emerged.

First, there is mounting evidence that skeletal muscle is an “endocrine” organ and that contracting muscles can release factors that have important effects throughout the body. In the past 10 or 20 years, cardiac muscle (largely in response to mechanical stimulation) has been shown to release many factors that have effects on the kidney, blood vessels, and central nervous system. Is skeletal muscle next? What substances might it release and what organs other than muscle are targeted (5)?

Second, it increasingly appears that in humans a number of genetic factors in combination with the level of habitual physical activity (including exercise training) determine how humans respond to these stresses. This general idea is of course intuitive and obvious to anyone who has ever conducted a simple training study. Some participants show dramatic changes, whereas others show minimal effects. However, in the coming years, candidate genes and other factors that might contribute to the magnitude of the adaptive responses to exercise and physical activity will continue to emerge. New technology will make it relatively easy (at least conceptually) to test many of these candidate genes in animal models and “prove” their potential role in the biological responses to exercise. Likewise, epidemiologic approaches will make it possible to “associate” a particular genetic variant or combination of variants with a given phenotype. However, will it be possible to perform physiologically mechanistic studies in humans with traditional deterministic hypotheses in the “genomic” era (7)?

A number of News Briefs over the past six years have also focused on issues that are broadly related to applied exercise science and human performance. Although insights into basic physiological mechanisms are frequently generated by studies of human performance, it is perhaps part of our basic human nature to be curious about why some people are exceptionally fast, strong, and skilled. Likewise, it is perhaps part of our basic human nature to want to understand just how far and hard we can push ourselves on both an individual basis and as a species. In this context, there are a number of areas that will continue to be of importance in studies of human performance: 1) what is the optimal frequency, intensity, and duration of training to achieve optimal performance (4)?, 2) what is the best use of nutritional and environmental strategies to achieve optimal performance (6)?, and 3) how can exercise science be used to prevent and eliminate doping in competitive sport?

SUMMARY

In closing, it has been a privilege and pleasure to edit the News Briefs section of ESSR for the past six years. Exercise science has emerged as one of the most interesting and intellectually challenging areas of study for those interested in integrative biology. The opportunities in public health, basic science, and applied studies highlighted make it seem likely that this trend will continue for the foreseeable future. As the great Danish physiologist Erling Asmussen once remarked, “There is no danger of running out of work for those engaged in the study of physical exercise” (1).

References

1. Asmussen, E. Exercise: general statement of unsolved problems. Circ. Res. 20:12–15, 1967.
2. Booth, F.W., M.V. Chakravarthy, S.E. Gordon, and E.E. Spangenburg. Waging war on physical inactivity: using modern molecular ammunition against an ancient enemy. J. Appl. Physiol. 93:3–30, 2002.
3. Chakravarthy, M.V., and F.W. Booth. Eating, exercise, and “thrifty” genotypes: connecting the dots toward an evolutionary understanding of modern chronic diseases. J. Appl. Physiol. 96:3–10, 2004.
4. Coyle, E.F. Very intense exercise-training is extremely potent and time efficient: a reminder. J. Appl. Physiol. 98:1983–1984, 2005.
5. Pedersen, B.K., and M. Febbraio. Muscle-derived interleukin-6-A possible link between skeletal muscle, adipose tissue, liver, and brain. Brain. Behav. Immun. 19:371–376, 2005.
6. Stray-Gundersen, J., R.F. Chapman, and B.D. Levine. “Living high-training low” altitude training improves sea level performance in male and female elite runners. J. Appl. Physiol. 91:1113–1120, 2001.
7. Wolfarth, B., M.S. Bray, J.M. Hagberg, L. Perusse, R. Rauramaa, M.A. Rivera, S.M. Roth, T. Rankinen, and C. Bouchard. The human gene map for performance and health-related fitness phenotypes: The 2004 update. Med. Sci. Sports. Exerc. 37:881–903, 2005.
©2005 The American College of Sports Medicine