Lee C F, Katsuura T, Harada H, Kikuchi Y
Department of Ergonomics, Graduate School of Science and Technology, Chiba University.
Appl Human Sci. 1995 May;14(3):111-7. doi: 10.2114/ahs.14.111.
The purpose of the present study was to evaluate the different behavior of forearm blood flow (FBF) during intermittent isometric handgrip (IIHG, 6 seconds contraction +6 seconds relaxation) in a thermoneutral versus a hot environment. Six healthy men performed three times of 5-minute period IIHG at three different work loads (10%, 20% and 30% MVC). The IIHG was performed with the right hand. The experiments of IIHG were performed at two different air temperatures (25 degrees C and 40 degrees C, RH: 50%), and an experiment without work was also carried out at 40 degrees C (RH: 50%). The physiological responses measured involved heart rate (HR), cardiac output (CO), mean arterial blood pressure (MBP), FBF, and skin blood flow (SBF). HR, CO and SBF showed higher values during IIHG at 40 degrees C than at 25 degrees C. MBP had a tendency to increase with the intensity of work load at both 25 degrees C and 40 degrees C. Since intramuscular pressure might increase during contraction periods at 20% MVC and 30% MVC at 25 degrees C, FBF was significantly higher during relaxation periods than during contraction periods. FBF showed similar values between contraction and relaxation periods at 10% MVC at both temperatures. The present study suggested that FBF was sufficient for active muscles during IIHG at 10% MVC. FBF of contraction periods was close to that of relaxation periods at 40 degrees C due to the modulation of the sympathetic outflow to the muscles and/or the decreased efficiency of the muscle pump. It was suggested that FBF showed different behaviors during HHG at 25 degrees C versus at 40 degrees C.
本研究的目的是评估在热中性环境与热环境下，间歇性等长握力（IIHG，6秒收缩+6秒放松）过程中前臂血流量（FBF）的不同表现。六名健康男性在三种不同工作负荷（10%、20%和30%最大随意收缩力，MVC）下进行了三次5分钟的IIHG。IIHG用右手进行。IIHG实验在两种不同的气温（25摄氏度和40摄氏度，相对湿度：50%）下进行，并且在40摄氏度（相对湿度：50%）时还进行了一次无工作的实验。测量的生理反应包括心率（HR）、心输出量（CO）、平均动脉血压（MBP）、FBF和皮肤血流量（SBF）。在40摄氏度下进行IIHG时，HR、CO和SBF的值高于25摄氏度时。在25摄氏度和40摄氏度时，MBP都有随工作负荷强度增加的趋势。由于在25摄氏度下，20%MVC和%MVC收缩期肌肉内压力可能会升高，因此FBF在放松期显著高于收缩期。在两个温度下，10%MVC时FBF在收缩期和放松期的值相似。本研究表明，在10%MVC的IIHG过程中，FBF足以满足活跃肌肉的需求。由于交感神经向肌肉的输出调节和/或肌肉泵效率降低，40摄氏度时收缩期的FBF接近放松期的FBF。研究表明，25摄氏度与40摄氏度下HHG期间FBF表现不同。
