Previous studies showed that conduit artery blood flow rapidly increases after even a brief contraction of muscles within the dependent limb. Whether this rapid hyperemia occurs within contracted skeletal muscle in humans has yet to be confirmed, however. We therefore used diffuse correlation spectroscopy (DCS) to characterize the rapid hyperemia and vasodilatory responses within the muscle microvasculature induced by single muscle contractions in humans. Twenty-five healthy male volunteers performed single 1-s isometric handgrips at 20%, 40%, 60% and 80% of maximum voluntary contraction (MVC). DCS probes were placed on the flexor digitorum superficialis muscle, and a skeletal muscle blood flow index (SMBFI) was derived continuously. At the same time, brachial artery blood flow (BABF) responses were measured using Doppler ultrasound. Single muscle contractions evoked rapid, monophasic increases in both SMBFI and BABF that occurred within 3 s after release of contraction. The initial and peak responses increased with increases in contraction intensity and were greater for BABF than for SMBFI at all intensities. BABF reached its peak within 5 to 8 s after the end of contraction. The SMBFI continued to increase after the BABF passed its peak and was decreasing toward the resting level and peaked about 10 to 15 s after completion of the contraction. We conclude that single muscle contractions induce rapid, intensity-dependent hyperemia within the contracted skeletal muscle microvasculature. Moreover, the characteristics of the rapid hyperemia and vasodilatory responses of skeletal muscle microvessels differ from that simultaneously evaluated in the upstream conduit artery.

中文翻译：

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人体收缩骨骼肌内的快速血管舒张：同时使用扩散相关光谱和多普勒超声的新见解

先前的研究表明，即使相关肢体中的肌肉短暂收缩，导管动脉的血流量也会迅速增加。但是，这种快速充血是否发生在人的骨骼肌收缩中尚待证实。因此，我们使用了弥散相关光谱法（DCS）来表征由人体中单个肌肉收缩引起的肌肉微脉管系统中的快速充血和血管舒张反应。25名健康的男性男性志愿者按最大自愿收缩（MVC）的20％，40％，60％和80％进行了一次1-s等距握把。将DCS探头放置在浅指屈肌上，并连续获得骨骼肌血流指数（SMBFI）。同时，使用多普勒超声测量肱动脉血流（BABF）反应。单肌收缩引起SMBFI和BABF的快速单相增加，这在收缩释放后3 s内发生。初始和峰值反应随收缩强度的增加而增加，并且在所有强度下，BABF均大于SMBFI。收缩结束后，BABF在5至8 s内达到峰值。在BABF超过峰值后，SMBFI继续增加，并朝着静止水平下降，并在收缩完成后约10至15 s达到峰值。我们得出的结论是，单个肌肉收缩会在收缩的骨骼肌微脉管系统内引起快速的，强度依赖性充血。此外，骨骼肌微血管的快速充血和血管舒张反应的特征与同时在上游导管动脉中评估的特征不同。