228 THE PHYSIOLOGY OF MUSCULAR WORK 



THE EFFECTS OF MUSCULAR EXERCISE UPON THE HEART 

 AND CIRCULATION 



There is little doubt that the heart is the organ which is most 

 easily damaged by exercise unsuited to the weak and untrained. 

 Trainers of both men and animals rightly attach the greatest im- 

 portance to the condition of the heart, and a vast medical literature 

 upon cardiac strain, the athlete's heart, and the soldier's heart 

 bears witness to the importance of the subject to the medical man. 



It will be well therefore to indicate the most practical methods 

 for the examination of the heart in relation to the effects of exercise. 

 There is no question here of a consideration of a heart in a con- 

 dition of disease, and nothing will be said about inspection, palpa- 

 tion, percussion, and auscultation, which are recognised methods 

 in an ordinary clinical examination. In order to test the capacity 

 of a heart to bear the strain of muscular work the most useful 

 method appears to be a comparison of the rate of cardiac con- 

 traction at rest, directly after moderate exercise of a few minutes' 

 duration, and again after periods of five, ten, or more minutes' rest. 

 The effect of exercise is an augmentation of the rate ; during the 

 rest which follows the work the beats rapidly decrease in the case 

 of a strong well-trained heart, but slowly in the case of a weak 

 and untrained one. The following example of such an observa- 

 tion ( 24 ) will show the contrast : 



The exercise lasted thirty seconds, and consisted in running 

 down and up stairs. 



In some special cases examination of the heart by means of the 

 Rontgen rays may elucidate certain questions, but the method is of 

 limited application and is beset with sources of error. The same 

 remarks apply to the cardiograph, the records of which may be 

 so complicated as to be misleading. 



The pulse, not only furnishes information on the rate and force 

 of the beat of the heart, but also on the condition of the peripheral 

 circulation. The sphygmograph affords a graphic record of the 



