Micheletti P, Macchi G, Finulli P, Belleri M
Dipartimento di Scienze Biomediche e Biotecnologiche, Università di Brescia.
G Ital Cardiol. 1990 Feb;20(2):148-57.
The effect of exhausting isometric contraction (60% of the maximal voluntary contraction) on left ventricular function has been investigated using echocardiography (M and B mode) in 4 groups, each of 8 subjects (27 +/- 5 years; mean +/- SD): weight lifters, 2 years of training; amateur cyclists, 4 years of training; sedentary controls, and hypertensive subjects, 1st WHO class. Heart rate, arterial pressure, ventricular diameters (diastolic and systolic), wall thickness, wall stress and the double product (heart rate x arterial pressure) were determined at rest, at exhaustion and after 30, 90 and 180 s of recovery. Maximal voluntary contraction was 48 +/- 9 kg in weight lifters; 32 +/- 5 kg in amateur cyclists; 32 +/- 4 kg in sedentary control and 36 +/- 7 kg in 1st WHO class. Exhaustion time ranged from 80 s to 120 s. Our results showed that: 1) in all subjects at exhaustion, arterial pressure and heart rate increased significantly and the index of ventricular function was decreased but not significantly; 2) after 180 s of recovery both arterial pressure and heart rate returned to the pre-exercise value; 3) wall stress was significantly lower in weight lifters than in sedentary controls; 4) the double product (index of myocardiac oxygen consumption) resulted lower in amateur cyclists that in sedentary controls. The hypertrophy of the heart could justify the slight increase in wall stress observed in weight lifters during isometric exercise. However, the low index of myocardiac oxygen consumption in amateur cyclists probably reflects the changes in cardiovascular function due to the endurance training. In hypertensive subjects, the isometric contraction causes significant and substantial increase of the wall stress and the double product.
采用超声心动图（M型和B型）对4组受试者（每组8人，年龄27±5岁；均值±标准差）进行研究，观察力竭性等长收缩（最大自主收缩力的60%）对左心室功能的影响。这4组受试者分别为：有2年训练经验的举重运动员；有4年训练经验的业余自行车运动员；久坐不动的对照组；世界卫生组织I级高血压患者。分别在静息状态、力竭时以及恢复30秒、90秒和180秒后测定心率、动脉压、心室直径（舒张期和收缩期）、室壁厚度、壁应力以及心率与动脉压的乘积（双乘积）。举重运动员的最大自主收缩力为48±9千克；业余自行车运动员为32±5千克；久坐不动的对照组为32±4千克；世界卫生组织I级高血压患者为36±7千克。力竭时间为80秒至120秒。我们的研究结果显示：1）在所有受试者力竭时，动脉压和心率显著升高，心室功能指标降低，但降低不显著；2）恢复180秒后，动脉压和心率均恢复至运动前水平；3）举重运动员的壁应力显著低于久坐不动的对照组；4）业余自行车运动员的双乘积（心肌耗氧量指标）低于久坐不动的对照组。心脏肥大可能是举重运动员在等长运动时观察到的壁应力略有增加的原因。然而，业余自行车运动员较低的心肌耗氧量指标可能反映了耐力训练引起的心血管功能变化。在高血压患者中，等长收缩会导致壁应力和双乘积显著大幅增加。
