standing of certain physiologic phenomena and the consequences following various forms of muscular activity.

CARDIAC EFFICIENCY IN RELATION TO EXERCISE

As it is clearly evident that the response of the cardiovascular system to muscular effort depends largely upon the integrity of the musculature of the heart, it follows that in approaching this subject the dividing line must be sharply drawn between individuals having abnormalities of the heart and arterial systems and those whose circulatory apparatus is intact.

Extreme caution should be exercised before permitting active muscular exertion and competitive exercise to individuals who are known to have cardiovascular and renal defects, and when permitted always should be under constant competent supervision. This does not mean that the presence of cardiac, renal and vascular defects, per se, preclude indulgence in all forms of sports and exercises; indeed the judicious employment of properly supervised and carefully adjusted muscular effort, including certain mild sports, should form a large part of the medical care of persons coming under this group.

Cardiac efficiency or cardiac effectiveness means cardiac muscle integrity, and this in turn implies not only an ability of the heart to supply the normal demands of everyday life, but also an ability to respond to extraordinary demands in such a manner that an adequate circulation will be maintained.

It is believed that the normal heart in youth with the body at rest, does not expend more than one-twelfth of its potential or reserve energy. Under ordinary conditions

of active life, involving moderate work, from one-fourth to one-third of reserve power is called out, while the full capacity is only demanded by the most severe forms of exercise demanding great endurance. This reserve or potential energy is closely related to the demands of the tissues and organs for additional blood. With the body at rest it is estimated that 60 c.c. of blood is expelled from the heart at each systole, at the rate of seventy-two times per minute. Upon demand this volume output may be increased sixfold, the increase in output being partly the result of an increased cardiac rate and partly an increased systolic capacity.

The whole question of cardiac efficiency hinges upon the presence of an adequate potential reserve or factor of safety, and the development of cardiac insufficiency is almost wholly dependent upon the degree of reduction in cardiac reserve as compared with the demands for the expenditure of excess energy. It is upon these two factors, cardiac reserve, and the demand for expenditure of energy that the degree of physical fitness depends.

Concerning the formulation of hard and fast rules, regulations and restrictions, for the guidance and control of individuals with such defects, very little can be said, as every case differs from every other and should be governed by mature judgment, based upon the results of careful physical examination, functional tests and experimental exercises.

Given an evident "pathologic fault," the most practical means at our disposal with which to corroborate and qualify the results of the physical examination are, an analysis of the urine and a study of blood-pressure, especially noting in the latter, variations in systolic, diastolic

and pulse pressures, and also pulse rate under changing conditions of rest and exercise. The so-called functional tests (see Chapter XIX, page 331) should be applied to all except adolescents and youths. A pathologic urinary finding will, of course, be given its proper value, and be collated with the other evidence at hand.

Valvular defects alone have little effect upon normal blood-pressure values, especially in the young, excepting those with aortic regurgitation, and in those past middle life, whose reserve has become reduced and where vascular and renal degenerative changes contribute to the circulatory instability.

Concerning the pure forms of cardiac hypertrophy, such as occur in the absence of valvular lesions or the history of previous disease, Barach1 is of the opinion that when subjected to strain they differ very little from normal hearts, as in a series of observations on 50 youths he noted only the usual transitory dilatation following overstrain from long-distance running.

Continued indulgence in athletics is generally essential to good health in this class, as exercise tends to delay the onset of degenerative changes which would follow the development of sedentary habits of life.2

The discovery of an abnormal blood-pressure value (see Chapter XVI, page 246, for discussion of causes) while not a cause for eliminating all exercise, will tend to move such individual's age limit forward and so reduce the amount of exercise to be safely indulged.

Arteriosclerosis even without hypertension suggests the

1 Jour. A. M. A., Oct. 29, 1910, lv, 18, p. 1581.
2 Robert E. Coughlin, Med. Rec., Apr. 2, 1910.

same caution, except where the arterial change is purely local and evidently limited to the superficial vessels, as in those accustomed to manual labor without any renal lesion.

For the detection of myocardial degeneration and insufficiency recourse must be had to the functional tests, as advocated by Graupner,1 Boardman Reed,2 and others.

Graupner and others, who have investigated the question of the rise and fall of systolic pressure during and after exercise, have found that normal hearts, those with wellcompensated valvular lesions, and neurotic hearts, respond to exercise by a rise in pressure; whereas myocardial cases either fail to show a rise or respond by a lessened tension varying from 3 to 15 mm.

E. Masing advises a careful study of the effect of exercise upon the normal relation between systolic and diastolic pressure, i.e., the effect of exercise upon the pulse pressure. Thus a normal circulatory system will yield a disproportionate rise in systolic pressure as compared with diastolic, thereby producing temporarily an increased pulse pressure, while with a defective circulation, even if there occurs a rise in systolic and diastolic pressures, the two tend to approximate and thus the pulse pressure becomes smaller.

Age in Relation to Athletics.—In order to study the effect of exercise upon the normal individual and the amount of energy expended in relation to blood-pressure variation and to the margin of cardiac safety, Coughlin found it

1 Berl. klin., 1902, xv, 174.

2 South. Calif. Pract., August, 1910.
Deut. Arch. f. klin. Med., 1902, lxxiv.

convenient to group the athletic age of man under four divisions,1 viz.:

1. Early life, including infancy, childhood and youth, up to twenty-one years.

2. Manhood, from twenty to forty years.

3. Middle age, from forty to fifty-five years.
4. Beyond middle life, up to old age.

1. Early Life to Young Manhood.—Of first importance at the approach of what may be called the threshold of athletic life is the determination of the presence or absence of cardiovascular or renal abnormalities which might subject the individual to grave danger if not discovered before active athletics are indulged in.

Parents of growing children are beginning to appreciate the value of more definite information concerning their children's physical condition, both to determine the presence of possible abnormalities, and also to avoid the development of future physical defects and weaknesses, through a knowledge of the character and amount of exertion that may be safely indulged in.

The problem is frequently brought to the physician for solution, by a question somewhat like the following: "Doctor, my boys are going to boarding school this fall and I am anxious to know whether their physical condition is such that they may indulge in track work, football, basketball, etc."

The solution of this problem is not so easy as it appears and to give a definite reply is to shoulder a great responsibility.

1 R. E. Coughlin, Med. Rec., Apr. 2, 1910.