ISSUES IN YOUTH FITNESS

JOHN J. MCNAMARA, M.D. M.P.H. Bureau of Maternal and Child Health,

California State Department of Public Health, Berkeley, California

Fitness in American youth is a concern of educators, physicians and parents. It must become an ongoing concern of young men and women. The question of fitness is central to the major unsolved problem i n medicine; namely, prevention of disease. In this article I will examine the question of fitness or health in American youth; outl ine the tradit ional approaches to the measurement of negative health status and the inherent inadequacies of these measures; indicate the need for the development of measures of positive health status; look at the problem of health screening; examine some of the epidemiological risk factors for cardiovascular disease in adults, the principal cause of mortality i n this age group; indicate the problem of decision-making and program development in a situation of uncertainty; consider some of the philosophical, economic and social constraints to program development; and finally look at some of the challenges to preventive programs for school age children.

American youth is basically healthy. This statement is certainly true if’one looks at the relatively affluent white majority. American youth is well clothed, well housed, well fed and well educated. However, superficial examination of mortality and morbidity data tends to dispute this statement. Mortality data and morbidity or illness data are frequently employed measures of health status, emphasizing, of course, deviation from Health.

The infant mortality rate in the United States compares unfavorably to many other nations. In 1968,’ the U.S. ranked thirteenth in comparison to other nations, with an infant mortality rate of 21.7 deaths per thousand live births. Sweden had an infant mortality rate of 12.9 deaths per thousand live births. The Scandinavian countries, Japan, the U.K., Australia, New Zealand, France and East Germany had lower rates than the United States. While the analysis of the problem of infant mortality is complex, in this country the

problems of poverty, race and access to medical care seem to be dominant over questions of “intrinsic” fitness or a quality of medical care received.

In New York City the marked local differences in this health status measure are clearly evident. In a relatively affluent section of the city, Maspeth-Forest Hills, Queens, the infant mortality rate in 1966-1967 was 13.0 per thousand. However, only 0.8 percent of the births were to Puerto Rican women and only 1.7 percent of the births were to nonwhite mothers. Only 7.4 percent of the deliveries were to women with late or no prenatal care. However, in Central Harlem the infant mortality rate was 41.5 per thousand. 93.5 percent of the mothers were nonwhite and 36.3 percent had late or no prenatal care. “Unsolved social rather than purely medical components may well be responsible for the current stagnation in the high rates of infant mortality in the United States.”’ The rates in more affluent areas, therefore, are seen to compare favorably with the best rates attainable in the world.

After the first year of life even average mortality rates compare favorably in all developed countries. The second year age-specific death rate in Sweden is 0.9 per thousand population. In the USA the rate is 1.6 per thousand population, which is very comparable to other European n a t i o n s bu t c o n t r a s t s marked ly with underdeveloped nations such as Egypt where the rate is 107 per thousand. The problem of severe malnutrition in these underdeveloped areas is the major factor responsible for this difference.

Looking at morbidity data, the traditional causes of childhood illness and death, namely infectious diseases, have declined to quite low levels through immunization and improvement in social conditions. The major cause of death and disability in children over 1 year is now due to accidents. This again emphasizes the social nature of disease in the U.S. Fifteen thousand children

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under age 15 die each year from accidents in the United StatesJ Many more are injured less severely. Congenital malformations, respiratory diseases and cancer form the other leading causes of death and disability. In general, many specific causes of disability such as rheumatic fever have shown decreasing overall trends. Overall death rates decline to a low of 0.4 deaths per thousand persons in the 5-14 year age group. They rise slightly in young adulthood. Starting i n the mid- ~ O ’ S , however, a marked rise in the death rate becomes noticeable, doubling over 1 0-year intervals subsequently. It should be emphasized that the average 35-year-old man is not ill. He may consult his physician and find that he has no sign of disease. In many individuals, pre-morbid cardiovascular disease is often already well established. Data collected from autopsies on combat soldiers illustrate the extent of this problem. Both in KoreaS and Vietnam heathly combat troops killed in action were found to have a high incidence of coronary heart disease. Postmortem examination of 105 U.S. soldiers killed in Vietnam6 showed that 45 percent had some evidence of coronary atherosclerosis and 5 percent had gross evidence of severe coronary atherosclerosis. This is not symptomatic or clinically evident. The mean age of these soldiers at death was 22.1 years.

It is evident that traditional negative measures of health status, namely mortality and morbidity data, do not adequately reflect the health of the population. Measures which indicate pre- symptomatic states and preferably measures which get at positive health or fitness are needed.

The major causes of death in adults are heart disease, cancer and stroke. Pre-morbid states are known to exist in the principal type of heart disease, namely coronary atherosclerosis. However, early identification of the pre-morbid s t a t e has r e s i s t ed s o l u t i o n . A r e c e n t Czechoslovakian study on screening for Ischaemic Heart Disease concluded “the most significant tool for screening is shown to be the use of questionnaires, searching for symptomatic forms of Ischaemic Heart Disease.” ’ Clearly such an approach is at best an early detection of already existing disease states coupled with rehabilitation and is not a preventive approach.

There have been numerous studies of the epidemiology of coronary heart disease. The longitudinal study in Framingham, Massachusetts has elucidated many of the risk factors associated

with the development of coronary heart disease. Seven risk factors were identified:

1. Age 2. Serum cholesterol 3. Systolic blood pressure 4. Relative weight 5. Hemoglobin 6. Cigarette smoking 7. Electrocardiographic disturbances

A multi-variate analysis looking at the simultaneous effect of many risk factors on incidence of disease shows the striking combined effect of these factors. “The difference in incidence between the highest and lowest decile of risk is thirtyfold for men and seventyfold for women.” a The most important single risk factors were found to be cholesterol level, cigarette smoking, ECG abnormalities and blood pressure.

Other studies have found similar results. A retrospective study of coronary heart disease victims and behavior affecting health during college, noted the adverse effect of cigarette smoking, high blood pressure and body weight. A protective effect was noted from varsity athletics.

Another var iable is tha t of exercise. Occupations associated with physical exercise seem to be protective against coronary heart disease. Sedentary occupations are associated with increased risk of coronary heart disease. The classic research on London busmen lo in which the drivers and the conductors, the former largely sedentary, the latter more active, were contrasted with respect to the incidence of coronary heart disease showed a lower incidence in the conductors. Some studies have shown that as the amount of heavy work done increased in populations able to vary their diet, the amount of dietary fat consumed increased.” The benefit of exercise is cancelled by the change in diet. In controlled settings, which of course would be impossible to achieve under normal living conditions, exercise is seen to dissipate increased calories eaten in the form of fat and not result in a rise in blood lipids.l2 In other experiments, under more normal conditions, little change in serum cholesterol has been observed with exercise.IJ While these studies are not conclusive because of the inability to control other life factors, they are suggestive that exercise as well as diet may be major factors in the control of coronary heart disease.

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Clearly, all the answers are not in with respect to cardiovascular disease. Program development must proceed under conditions of some uncertainty. However, enough data is available to support the development of programs which may have significant beneficial effects, especially if these programs are well evaluated.

Given the early and insidious onset of this disease, it would seem that any preventive program should be aimed at the elementary school child. The major risk factors such as serum cholesterol and blood pressure are generally normal in this age group. Obesity and cigarette smoking may be a problem. The exercise that children get is extremely variable.

School examinations which focus on disease and defects usually find no pathology. Also fitness tests may or may not measure cardiovascular fitness." Some may measure skill; others measure agility. There may be little or no correlation between results obtained on different fitness tests. At present, the best measure of cardiovascular fitness seems to be maximum oxygen uptake. This is the amount of oxygen the body can take up under increasing workloads as measured on a tread mill, or on a bicycle ergometer. Studies have been done on the work capacity and oxygen uptake of children in the United States and Europe, and in general a similar degree of fitness is f o ~ n d . ' s - ~ ~

A number of critical questions remain unanswered. The relationship between the performance on this test and illness in general is unclear. Certain kinds of cardiovascular disease and anemia are known to result in poor performance.2' However, the relationships between performance on this test and general disability and school absenteeism is unknown. Also, the critical question of the relationship between performance on this task and the future development of coronary heart disease is unknown.

It is known that aerobic conditioning programs will improve work capacity and oxygen uptake of individuals.21 It is also known that traditional PE programs have no effect on increasing oxygen uptake.23 In a situation such as this, the weight that can be attached to physical exercise as a preventative for coronary heart disease is unknown. While top class athletes have been known to be less afflicted with coronary heart disease, the minimum amount of exercise that would be pro tec t ive is unknown. The

development of coronary heart disease is related to diet and yet, the effect of a high fat diet may be more easily ameliorated by exercise in youth than in adulthood. The measure of fitness, namely oxygen uptake, is a measurement of fitness at one point in time only. Repeated measurements over time will be of more significance than single measurements. Repeated poor performers may be the ones who go on to develop the ful l constellation of risk factors associated with the development of cardiovascular disease.

What are the implications of this for program development? Full implementation of a school program in health education which covers among other things relationships between nutrition and health; discussion of body growth and deterioration; and the implications of this in a sedentary, urbanized, nonactive society is imperative.

Full implementation of physical education programs which focus on aerobic conditioning in elementary school children, with assessment of performance is necessary.

A full school health program which stresses preventive aspects of disease and personal responsiblity for one's own health, will complete the program and also establish sources of referral for identified problem children. The problem$ of implementation in a society dedicated to open discussion and local choice are obvious. It is, however, important to address the question of economic priorities when these conflict with programs of potential benefit to all children. Also, it is imperative to insure that in our increasingly urbanized environment, adequate provision is made for parks and recreational facilities. Without a physical enviornrnent conducive to health, program development will founder.

Finally, some of the unanswered research questions must be tackled. At present, the California State Department of Public Health is engaged in a joint study with the Department of Physical Education at the University of California at Davis to look at the relationships between fitness measurements, health status, school absenteeism, attitudes toward physical exercise and activity levels in elementary school children. Longitudinal studies should also be undertaken to look at the long-term effects of conditioning programs.

In summary, the benefits to be achieved by physical exercise in relation to the prevention of

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cardiovascular disease remain problematic. The national epidemic of cardiovascular disease, resulting in premature death, long-term disability and great financial hardship for the American adult population, does require a concerted preventive program for school-age children. Carefully designed programs which will give answers to some of the questions that have been raised here deserve the support of schools, parents and young people themselves.

REFERENCES I . U.S. Govt. Profiles of Children. The 1970 White

House Conference on Children. Superintendent of Documents, U.S. Govt. Printing Office, p. 90.

2. Erhardt. C.L. et al. An Epidemiological Approach to Infant Mortality. Arch Environ Health, 20:756, June 1970.

3. Gordon, J.E. et al. The Second-Year Death Rate in Less Developed Countries. Amer J Med Sci, 254:365, September 1967.

4. fbid. Number 1, p. 28. 5. Enos, W.F. et al. Primary Disease Among United

States Soldiers Killed in Action in Korea. Preliminary report. JAMA. 152:1090-1093, 1953.

6. McNamara, J.J. et al. Coronary Artery Disease in Combat Casualities in Vietnam. JA M A . 21 6: 1 1 85- 1187, May 1971.

7. Fodor, J. Screening for Ischaemic Heart Disease. In Sharpe CLEH and H. Keen, Presymptomatic Detection and E a r l y Diagnosis, A Cr i t ica l Appraisal, The Williams and Wilkins Co., Baltimore, 1968, p. 293.

8. Truett, J. et al. A Multivariate Analysis of the Risk of Coronary Heart Disease in Framingham. J Chronic Dis, 20:s 1 1-524. 1967.

9. Paffenbager, R.S., Jr. et al. Chronic Disease in Former College Students 11. Methods of Study and Observations on Mortality from Coronary Heart Disease. Am J of Pub H, 56:962-971, June 1966.

10. Shaper, A.G. et al. The London Busmen. I n Larsen, O.A. and R.O. Malmborg, ed., Coronary Heart Disease und Physical Fitness. Proceedings of

'

a Symposium, Copenhagen, September 1970, University Park Press, Baltimore.

11. Keys, A. et al. Styles in Populations Differing in Serum Cholesterol, J Clin Invest, 391 173-1 181, July 1956.

12. Mann. G.V. et al. Exercise in the Disposition of Dietary Calories; Regulation of Serum Lipoprotein and Cholesterol Levels in Human Subjects. New Eng J Med, 253:349-355. September 1955.

13. Montoye, H.J. et al. The Effects of Exercise on Blood Cholesterol in Middle-Aged Men. Amer J Clin Nutr, 7:139-145, March 1959.

14. Fowler, W.M. e t al. The Relation of Cardiovascular Tests to Measures of Motor Performance and Skills. Pediutrics, 32:778-789, October 1963.

15. Ostrand, P.O. Experimental Studies of Physicul Working Cupacity in Relution to Sex and Age. Egner Monksgaard, Copenhagen, 1952.

16. Rodahl, K. et al. Physical Work Capacity, A Study of Some Children and Young Adults in the United States. Environmental Heulth. 2:499-5 10, May 1961.

17. Kramer, J.D. et al. Maximal Exercise Tests in Children. American Journal of Diseases of Children, 108:283-297. September 1964.

18. Adams, F.H. et al. The Physical Working Capacity of Normal School Children, I. California. Pediutrics, 2855-64. July 196 1.

The Physical Working Capacity of Normal School Children, 11. Swedish City and Country. Pediutrics, 28:243-257, August I96 1.

20. Bengtsson. E. Working Capacity in Normal Children, Evaluated by Sub-Maximal Exercise on the Bicycle Ergometer and Compared with Adults. Actu Med Scun, 154:91-109, 1956.

21. Duffie, E.R. The Use of the Working Capacity Test in Children With Congenital Heart Disease. Pediutrics. 32:757-768, October 1963.

22. Roskamm, H.R. General Circulatory Adjustment to Exercise in Well-Trained Subjects. In Coronury H w r t Diseuse und Physicul Fitness, Larsen and Malmborg ed., Copenhagen, September 1970. University Park Press, Baltimore.

23. Cumming, C.R. et al. The Failure of School Physical Education to Improve Cardio-respiratory Fitness. Cunud Med Ass Joumul. 101:69-73, July 1969.

19.

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