Leyk D, Hoffmann U, Essfeld D, Baum K, Stegemann J
Physiologisches Institut, Deutschen Sporthochschule Köln.
Z Kardiol. 1994;83 Suppl 3:61-5.
The dynamics of external gas exchange during exercise is influenced by pulmonary, cardiovascular, and metabolic factors. During rest-exercise transitions the interaction of these factors is more complex than during exercise-exercise transients. In the present study, we directly compared oxygen uptake (VO2) and cardiac output (CO) responses to step changes in exercise intensity. Nine students performed the following step changes on a bicycle ergometer in upright body position: rest-20W, 20W-80W, 20-140W. VO2 was measured breath-by-breath while CO was determined beat-by-beat by means of a Doppler device. The probe was positioned in the suprasternal notch and directed towards the aortic root. When starting from the 20 W baseline the VO2 responses showed a first, mainly cardio-vascular component over the first 30 s, followed by a second, metabolic component at constant CO. The rest-exercise transients displayed two additional early features. First, there was a very rapid VO2 increase during the initial breathing cycles of the on-transient. This was probably caused by events in the lungs or the pulmonary circulation. Second, the CO attained its steady-state level in about 10 s. This suggests a sudden increase in venous return. The present results generally show that both the VO2 and CO kinetics are faster when exercise in the upright body position is started from rest.
运动期间外部气体交换的动力学受肺、心血管和代谢因素的影响。在从静息状态到运动状态的转换过程中，这些因素之间的相互作用比在运动强度不变的运动过程中更为复杂。在本研究中，我们直接比较了运动强度阶跃变化时的摄氧量（VO₂）和心输出量（CO）反应。九名学生在直立位的自行车测力计上进行了以下强度阶跃变化：静息-20W、20W-80W、20-140W。逐次呼吸测量VO₂，同时通过多普勒装置逐搏测定CO。探头置于胸骨上切迹并指向主动脉根部。从20W的基线开始时，VO₂反应在最初30秒内显示出第一个主要为心血管成分，随后在CO恒定的情况下出现第二个代谢成分。从静息到运动的转换显示出另外两个早期特征。首先，在运动开始的最初呼吸周期中，VO₂迅速增加。这可能是由肺部或肺循环中的事件引起的。其次，CO在约10秒内达到其稳态水平。这表明静脉回流突然增加。目前的结果总体上表明，当从静息状态开始进行直立位运动时，VO₂和CO的动力学都更快。
