Cahill N S, O'Brien M, Rodahl A, Allen J F, Knight D, Dolphin C
Br J Sports Med. 1979 Sep;13(3):122-9. doi: 10.1136/bjsm.13.3.122.
Left ventricle dimensions and wall stress were measured echocardiographically before and immediately after exercise in 14 athletes and 7 control subjects. Our findings suggest that afterload is an important determinant of cardiac performance and wall hypertrophy in athletes. In spite of major changes in heart rate and blood pressure, left ventricular wall stress remains unchanged following submaximal exercise, in trained and untrained hearts. It would appear that the changes in heart size during exercise are to a large extent limited in untrained ventricles, as smaller left ventricular dimensions are required, to "normalise" wall stress. This results in a lower stroke volume for a given stroke dimensional change. Consequently cardiac output is a function of heart rate rather than stroke volume in untrained subjects. The effect of increased muscle mass in athletes, is to permit larger left ventricular dimensions for a given afterload, thus stroke volume can be augmented. The increase h/R ratio suggests that afterload is more important than preload in the development of left ventricular hypertrophy in rowers and swimmers.
在14名运动员和7名对照受试者中，于运动前及运动后即刻采用超声心动图测量左心室尺寸和壁应力。我们的研究结果表明，后负荷是运动员心脏功能和心肌肥厚的重要决定因素。尽管心率和血压发生了重大变化，但在经过训练和未经训练的心脏中，次极量运动后左心室壁应力仍保持不变。在未经训练的心室中，运动期间心脏大小的变化在很大程度上似乎受到限制，因为需要较小的左心室尺寸来使壁应力“正常化”。对于给定的搏出量维度变化，这会导致较低的每搏输出量。因此，在未经训练的受试者中，心输出量是心率的函数而非每搏输出量。运动员肌肉质量增加的作用是，在给定后负荷的情况下允许更大的左心室尺寸，从而可以增加每搏输出量。h/R比值的增加表明，后负荷在划船运动员和游泳运动员左心室肥厚的发生中比前负荷更重要。
