Larsson S E, Larsson R, Zhang Q, Cai H, Oberg P A
Department of Orthopaedics, University Hospital, Linköping, Sweden.
Eur J Appl Physiol Occup Physiol. 1995;71(6):493-8. doi: 10.1007/BF00238550.
Mental stress was induced by the Stroop colour word task (CW task) and the effects on the microcirculation and electromyography (EMG) in the upper portion of the trapezius muscle were studied during a series of fatiguing, standardized static contractions. A lowered blood flow of the skin recorded continuously by laser-Doppler flowmetry (LDF) was used as a stress indicator in addition to an elevated heart rate. Muscle blood flow was recorded continuously by LDF using a single optical fibre placed inside the muscle, and related to surface EMG. A group of 20 healthy women of different ages was examined. Recordings were made during a 50-min period in the following sequence: a 10-min series of alternating 1-min periods of rest and stepwise increased contraction induced by keeping the arms straight and elevated at 30, 60, 90 and 135 degrees with a 1-kg load carried in each hand; a 10-min recovery period without load; a repeated contraction series with simultaneous performance of the CW task; a second 10-min recovery period, and a second contraction series without CW task. Signal processing was done on line by computer. The LDF and root mean square (rms)-EMG values were calculated, as well as the EMG mean power frequency (MPF) for fatigue. The CW-task added to the contraction series caused an increase in the heart rate accompanied by a decrease in the blood flow to the skin and a 30% increase in the blood flow in the exercising muscle. Both returned to normal during the subsequent recovery period and showed normal levels during the final contraction series without CW. The rms-EMG showed a 20% increase that persisted during the final contraction series performed without CW. There was no influence on MPF. This CW has previously been shown to evoke an increased secretion of adrenaline from the adrenal medullae to the blood. The increased blood flow in the exercising muscle would therefore appear to have been caused by beta-adrenoceptor vasodilatation, and the fall in the blood flow in the skin by alpha-adrenoceptor vasoconstriction. The findings may have implications for work situations characterized by repetitive static loads to the shoulder muscles and psychological stress.
通过Stroop色词任务（CW任务）诱发精神压力，并在一系列疲劳的标准化静态收缩过程中，研究其对斜方肌上部微循环和肌电图（EMG）的影响。除心率升高外，通过激光多普勒血流仪（LDF）连续记录的皮肤血流降低被用作压力指标。使用置于肌肉内的单根光纤通过LDF连续记录肌肉血流，并与表面肌电图相关联。对一组20名不同年龄的健康女性进行了检查。在50分钟内按以下顺序进行记录：10分钟的交替序列，包括1分钟的休息和通过双手伸直并抬高至30、60、90和135度且各手持1千克重物诱导的逐步增加的收缩；10分钟的无负荷恢复期；同时进行CW任务的重复收缩序列；第二个10分钟的恢复期；以及第二个无CW任务的收缩序列。信号处理由计算机在线完成。计算LDF和均方根（rms）-EMG值，以及用于评估疲劳的EMG平均功率频率（MPF）。添加到收缩序列中的CW任务导致心率增加，同时皮肤血流减少，运动肌肉中的血流增加30%。两者在随后的恢复期恢复正常，并且在无CW的最终收缩序列期间显示正常水平。rms-EMG显示增加了20%，在无CW的最终收缩序列期间持续存在。对MPF没有影响。先前已证明这种CW会引起肾上腺髓质向血液中分泌的肾上腺素增加。因此，运动肌肉中血流的增加似乎是由β-肾上腺素能受体血管舒张引起的，而皮肤中血流的减少是由α-肾上腺素能受体血管收缩引起的。这些发现可能对以肩部肌肉重复性静态负荷和心理压力为特征的工作情况具有启示意义。
