Rowland T, Garrison A, Delulio A
Department of Pediatrics, Baystate Medical Center, Springfield, MA 01199, USA.
Int J Sports Med. 2003 Oct;24(7):512-7. doi: 10.1055/s-2003-42016.
The influence of body position on cardiac responses to progressive exercise was examined in 13 healthy circumpubertal boys. The subjects (mean age 12.5 +/- 1.4 y) performed a progressive cycle test with an identical protocol in the sitting and supine positions. Stroke volume and left ventricular dimensions were assessed with Doppler and two-dimensional echocardiography, respectively. During supine exercise, no changes were seen in stroke volume or left ventricular preload (end-diastolic dimension) with increasing exercise intensity. At rest, mean values for stroke volume and cardiac output were 16.4 % and 27.1 % lower, respectively, with subjects upright compared to supine. With upright exercise these variables rose to become insignificantly different than supine values. Stroke volume while cycling upright rose by 29 % by the second workload but remained stable at higher work intensities. The initial increase in stroke volume observed only when cycling upright presumably reflects mobilization of dependent blood in the lower extremities. The mechanisms governing cardiac responses to exercise when supine and upright are otherwise identical.
在13名健康的青春期男孩中研究了体位对心脏对渐进性运动反应的影响。受试者（平均年龄12.5±1.4岁）在坐姿和仰卧位以相同方案进行渐进性自行车测试。分别用多普勒和二维超声心动图评估每搏输出量和左心室尺寸。在仰卧位运动期间，随着运动强度增加，每搏输出量或左心室前负荷（舒张末期尺寸）未见变化。休息时，与仰卧位相比，受试者直立时每搏输出量和心输出量的平均值分别低16.4%和27.1%。在直立运动时，这些变量上升至与仰卧位值无显著差异。直立骑车时，每搏输出量在第二个工作量时增加了29%，但在更高的工作强度下保持稳定。仅在直立骑车时观察到的每搏输出量的初始增加可能反映了下肢下垂血液的动员。仰卧位和直立位时控制心脏对运动反应的机制在其他方面是相同的。
