Petrofsky Jerrold S, Suh Hye Jin, Gunda Shashi, Prowse Michelle, Batt Jennifer
Department of Physical Therapy, School of Allied Health Professions, Loma Linda University, Loma Linda, CA 92350, USA.
Med Eng Phys. 2008 Sep;30(7):931-6. doi: 10.1016/j.medengphy.2007.12.007. Epub 2008 Feb 20.
There is variability between individuals in the current needed to elicit a contraction in human muscle with surface electrodes. To understand what might be causing some of this variability, 25 subjects whose average age was 24.4+/-2.3 years, whose height was 165.5+/-9.5 cm, and whose average weight was 70.3+/-21 kg were examined. Electrical stimulation was applied above the motor point of the quadriceps, biceps, and lateral gastrocnemius muscles. To assess body fat, 2D ultrasound was used with a 1cm stand off. Electrical stimulation was applied with sine wave stimulation at 100 micros pulse width and at a frequency of 30 Hz. To alter skin blood flow, aside from the natural difference in skin blood flow at rest, hot packs and cold packs were used for 5 min. The average fat thickness below the quadriceps and gastrocnemius muscles was 0.75+/-0.13 cm and under the biceps was 0.48+/-0.16 cm. Without the use of hot or cold packs, the currents for the quadriceps and gastrocnemius muscles were significantly higher than that of the biceps (p<0.01). While there was some relationship between stimulation current and blood flow without the application of hot or cold packs, when hot packs were applied, skin blood flow increased as did the current required to stimulate muscle to threshold. When cold packs were applied, there was a decrease in the current required to stimulate these muscles. In conclusion, there is a causal relationship between skin blood flow, the thickness of the fat layer below the skin, and the current required to stimulate the muscle.
使用表面电极刺激人体肌肉引发收缩时，个体之间存在差异。为了解造成这种差异的原因，对25名受试者进行了检查，他们的平均年龄为24.4±2.3岁，身高为165.5±9.5厘米，平均体重为70.3±21千克。在股四头肌、肱二头肌和腓肠外侧肌的运动点上方施加电刺激。使用距离为1厘米的二维超声评估体脂。以100微秒的脉冲宽度和30赫兹的频率施加正弦波电刺激。为改变皮肤血流，除了静息时皮肤血流的自然差异外，还使用热敷袋和冷敷袋5分钟。股四头肌和腓肠肌下方的平均脂肪厚度为0.75±0.13厘米，肱二头肌下方为0.48±0.16厘米。在不使用热敷袋或冷敷袋的情况下，股四头肌和腓肠肌的电流显著高于肱二头肌（p<0.01）。在不使用热敷袋或冷敷袋时，刺激电流与血流之间存在一定关系，当使用热敷袋时，皮肤血流增加，刺激肌肉达到阈值所需的电流也增加。当使用冷敷袋时，刺激这些肌肉所需的电流减少。总之，皮肤血流、皮肤下方脂肪层的厚度与刺激肌肉所需的电流之间存在因果关系。
