Convertino V, Hung J, Goldwater D, DeBusk R F
Circulation. 1982 Jan;65(1):134-40. doi: 10.1161/01.cir.65.1.134.
The cardiorespiratory response to 10 days of continuous recumbency was assessed in 12 healthy men, age 50 +/- 4 years, who underwent supine and upright graded maximal exercise testing before and after bedrest. The decrease in peak oxygen uptake after bedrest was greater during upright exercise (15.1%, p less than 0.05) than during supine exercise (6.1%, NS): from 25.8 +/- 5.2 to 21.9 +/- 4.5 ml/kg/min and from 24.6 +/- 5.2 to 23.1 +/- 4.8 ml/kg/min. The decrease in submaximal work was also greater in the upright than in the supine position ( p less than 0.05). Ventilation volume was significantly elevated (p less than 0.05) after bedrest during maximal and submaximal effort in both the supine and upright positions. After bedrest, peak heart rate increased 5.7% and 5.9% during supine and upright testing, respectively (p less than 0.05). The increases in rate-pressure product after bedrest were significantly larger (p less than 0.05) during upright than during supine exercise. These results indicate that orthostatic stress is the most important factor limiting exercise tolerance after bedrest in normal middle-aged men. This mechanism also increases the myocardial oxygen demands during submaximal effort after bedrest. Intermittent exposure to gravitational stress during the bedrest stage of hospital convalescence may obviate much of the deterioration in cardiovascular performance that follows myocardial infarction.
对12名年龄在50±4岁的健康男性进行了评估，以观察他们在连续卧床10天后的心肺反应。这些男性在卧床休息前后分别进行了仰卧位和直立位分级最大运动测试。卧床休息后，直立运动时的最大摄氧量下降幅度（15.1%，p<0.05）大于仰卧运动时（6.1%，无显著性差异）：从25.8±5.2降至21.9±4.5 ml/kg/min，以及从24.6±5.2降至23.1±4.8 ml/kg/min。次最大运动量的下降在直立位也大于仰卧位（p<0.05）。在仰卧位和直立位的最大和次最大运动时，卧床休息后通气量显著升高（p<0.05）。卧床休息后，仰卧位和直立位测试时的最高心率分别增加了5.7%和5.9%（p<0.05）。卧床休息后，直立运动时的心率-血压乘积增加幅度显著大于仰卧运动时（p<0.05）。这些结果表明，直立位应激是限制正常中年男性卧床休息后运动耐力的最重要因素。这种机制还会增加卧床休息后次最大运动时的心肌需氧量。在医院康复的卧床阶段间歇性地暴露于重力应激下，可能会避免心肌梗死后心血管功能的大部分恶化。
