Hamann Jason J, Buckwalter John B, Clifford Philip S, Shoemaker J Kevin
Medical College of Wisconsin, Veterans Affairs Medical Center, Anesthesia Research 151, 5000 W. National Ave., Milwaukee, WI 53295, USA.
J Appl Physiol (1985). 2004 Jun;96(6):2146-52. doi: 10.1152/japplphysiol.00779.2003. Epub 2004 Feb 6.
Nine healthy volunteers performed a series of single handgrip isometric contractions to test the hypothesis that the blood flow response to a contraction is determined solely by the tension-time index (isometric analog of work). Contractions were performed in duplicate at 15, 30, and 60% of maximal voluntary contraction (MVC) at durations of 0.5, 1, and 2 s. Forearm blood flow (FBF) was measured beat by beat by using Doppler ultrasound. Peak FBF responded in a graded fashion to graded increases in peak tension with contraction time held constant (35, 56, and 90 ml/min for 15, 30, and 60% MVC for 1 s, respectively). When tension was kept constant, peak FBF responded in a graded fashion to graded increases in duration (77, 90, and 97 ml/min for 60% MVC for 0.5, 1, and 2 s). With a constant tension-time index, peak FBF responded in a graded fashion to graded increases in peak tension (48, 56, and 77 ml/min for 15% MVC/2 s, 30% MVC/1 s, and 60% MVC/0.5 s). Similar trends were also observed for total postcontraction hyperemia. Blood flow increased regardless of whether the change in tension-time index was accomplished by an increase in tension or duration of contraction. However, with a constant tension-time index, the change in blood flow was related to the peak tension developed. Our results suggest that the blood flow response to a single muscle contraction is not determined solely by the work performed (tension-time index) but also by the number of muscle fibers recruited.
九名健康志愿者进行了一系列单手等长收缩运动，以检验如下假设：对收缩的血流反应仅由张力 - 时间指数（功的等长类似物）决定。收缩分别以最大自主收缩（MVC）的15%、30%和60%重复进行，持续时间为0.5秒、1秒和2秒。使用多普勒超声逐搏测量前臂血流量（FBF）。在收缩时间保持恒定的情况下，峰值FBF随着峰值张力的分级增加而呈分级反应（1秒时，15%、30%和60%MVC对应的峰值FBF分别为35、56和90毫升/分钟）。当张力保持恒定时，峰值FBF随着持续时间的分级增加而呈分级反应（60%MVC时，0.5秒、1秒和2秒对应的峰值FBF分别为77、90和97毫升/分钟）。在张力 - 时间指数恒定的情况下，峰值FBF随着峰值张力的分级增加而呈分级反应（15%MVC/2秒、30%MVC/1秒和60%MVC/0.5秒对应的峰值FBF分别为48、56和77毫升/分钟）。收缩后充血总量也观察到类似趋势。无论张力 - 时间指数的变化是由张力增加还是收缩持续时间增加引起，血流量都会增加。然而，在张力 - 时间指数恒定的情况下，血流量的变化与所产生的峰值张力有关。我们的结果表明，对单次肌肉收缩的血流反应并非仅由所做的功（张力 - 时间指数）决定，还与募集的肌纤维数量有关。
