Tschakovsky M E, Shoemaker J K, Hughson R L
Department of Kinesiology, University of Waterloo, Ontario, Canada.
Am J Physiol. 1996 Oct;271(4 Pt 2):H1697-701. doi: 10.1152/ajpheart.1996.271.4.H1697.
A rapid (within 0-5 s) increase in skeletal muscle blood flow has been demonstrated following muscle contraction, yet the mechanism remains unresolved. Recently, it was suggested that the entire rapid exercise hyperemia could be attributed to the mechanical muscle pump effect. Other evidence indicates that the muscle pump cannot increase arterial flow. We measured human forearm blood flow with the arm positioned above or below heart level during 1) simulation of rhythmic muscle pump function via repeated inflation/deflation of a forearm cuff to 100 mmHg to achieve mechanical emptying of forearm veins, and 2) 1-s single-cuff inflations, 1-s voluntary forearm contractions, and 1-s contractions performed within a cuff inflation. Rhythmic cuff inflation increased blood flow with the arm below heart level (P < 0.05) but not above. Flow following single contractions was higher than flow following cuff inflation within 2 s (P < 0.05). Peak flow increases due to a single mechanical venous emptying (7.7 +/- 0.7 ml.100 ml(-1) min(-1)) could account for 60% of the peak flow increase due to muscle contraction (12.8 +/- 1.0 ml.100 ml(-1).min(-1)) with the arm below heart level, whereas above heart level mechanical venous emptying accounted for 46% of the flow increase due to contraction (3.0 +/- 0.4 vs. 6.5 +/- 0.6 ml.100 ml(-1).min(-1)). We conclude that a functional muscle pump does exist in the human forearm in vivo, but that a rapid vasodilation detectable within 2 s also contributes to the early exercise hyperemia.
肌肉收缩后，骨骼肌血流量会迅速（0 - 5秒内）增加，但其机制仍未明确。最近，有人提出整个快速运动性充血可能归因于机械性肌肉泵效应。其他证据表明肌肉泵并不能增加动脉血流量。我们在以下两种情况下测量了人体前臂血流量：一是将手臂置于心脏水平之上或之下，通过反复将前臂袖带充气/放气至100 mmHg来模拟有节律的肌肉泵功能，以实现前臂静脉的机械性排空；二是进行1秒的单袖带充气、1秒的自主前臂收缩以及在袖带充气期间进行1秒的收缩。有节律的袖带充气使手臂位于心脏水平以下时血流量增加（P < 0.05），而在心脏水平以上时则不然。单次收缩后的血流量在2秒内高于袖带充气后的血流量（P < 0.05）。手臂位于心脏水平以下时，单次机械性静脉排空导致的峰值血流量增加（7.7 ± 0.7 ml·100 ml⁻¹·min⁻¹）可占肌肉收缩导致的峰值血流量增加（12.8 ± 1.0 ml·100 ml⁻¹·min⁻¹）的60%，而在心脏水平以上时，机械性静脉排空占收缩导致的血流量增加的46%（3.0 ± 0.4 vs. 6.5 ± 0.6 ml·100 ml⁻¹·min⁻¹）。我们得出结论，在人体前臂体内确实存在功能性肌肉泵，但在2秒内可检测到的快速血管舒张也有助于早期运动性充血。
