Hung J, Goldwater D, Convertino V A, McKillop J H, Goris M L, DeBusk R F
Am J Cardiol. 1983 Jan 15;51(2):344-8. doi: 10.1016/s0002-9149(83)80063-0.
The mechanisms responsible for the decrease in exercise capacity after bed rest were assessed in 12 apparently healthy men aged 50 +/- 4 years who underwent equilibrium gated blood pool scintigraphy during supine and upright multistage bicycle ergometry before and after 10 days of bed rest. After bed rest, echocardiographically measured supine resting left ventricular end-diastolic volume decreased by 16% (p less than 0.05). Peak oxygen uptake during supine effort after bed rest was diminished by 6% (p = not significant [NS]), whereas peak oxygen uptake during upright effort declined by 15% (p less than 0.05). After bed rest, increases in heart rate were also greater during exercise in the upright than in the supine position (p less than 0.05). Values of left ventricular ejection fraction increased normally during both supine and upright effort after bed rest and were higher than corresponding values before bed rest (p less than 0.05). After bed rest, increased left ventricular ejection fraction and heart rate largely compensated for the reduced cardiac volume during supine effort, but these mechanisms were insufficient to maintain oxygen transport capacity at levels during upright effort before bed rest. These results indicate that orthostatically induced cardiac underfilling, not physical deconditioning or left ventricular dysfunction, is the major cause of reduced effort tolerance after 10 days of bed rest in normal middle-aged men.
对12名年龄在50±4岁、看似健康的男性进行了研究，以评估卧床休息后运动能力下降的机制。这些男性在卧床休息10天前后，于仰卧位和直立位多级自行车测力计运动期间接受了平衡门控血池闪烁扫描。卧床休息后，超声心动图测量的仰卧位静息左心室舒张末期容积减少了16%（p<0.05）。卧床休息后仰卧位运动时的峰值摄氧量减少了6%（p=无显著性差异[NS]），而直立位运动时的峰值摄氧量下降了15%（p<0.05）。卧床休息后，直立位运动时心率的增加也大于仰卧位运动时（p<0.05）。卧床休息后，仰卧位和直立位运动时左心室射血分数值均正常增加，且高于卧床休息前的相应值（p<0.05）。卧床休息后，左心室射血分数和心率的增加在很大程度上补偿了仰卧位运动时心输出量的减少，但这些机制不足以将氧运输能力维持在卧床休息前直立位运动时的水平。这些结果表明，体位性诱发的心脏充盈不足，而非身体机能减退或左心室功能障碍，是正常中年男性卧床休息10天后运动耐力降低的主要原因。
