Tetanic electrical stimulation of human muscle

脊髓损伤后，损伤部位以下的肌肉会恶化。肌肉质量的下降包括质量和最耐疲劳的肌肉纤维的损失。电刺激在克服这些问题方面取得了一些成功，但也有局限性。传统的刺激通过皮肤上的电极激活肌肉中幸存的运动神经，从而引起收缩。这会激活疲劳最快的肌肉纤维，使抗疲劳纤维相对不活跃。最近，我已经证明，通过以更高的频率和更宽的脉宽进行刺激，除了直接肌肉刺激之外，还会产生额外的收缩。这些“额外的”收缩是由信号通过反射通路往返于脊髓而产生的。这会以一种更自然的方式激活肌肉纤维，最耐疲劳的肌肉纤维首先被激活。因此，有可能利用这种脊髓机制来激活传统电刺激不能激活的抗疲劳肌肉纤维以及快速疲劳纤维，从而提高刺激的有效性，以改善肌肉质量。这份提案描述了旨在确定这些修改后的刺激参数是否将比目前使用的方案更有效地维持肌肉质量和产生康复收缩的实验。具体目标是：1.确定传递到大脑的信号在多大程度上导致额外的收缩。2.确定对神经或肌肉的刺激是否通过不同的机制产生收缩。3.在一组脊髓损伤受试者中，比较改良刺激参数和传统刺激方案在产生功能性运动和克服肌肉萎缩方面的有效性。研究结果将为进一步研究这项技术在脊髓损伤后维持肌肉质量的应用提供一个框架。

After a spinal cord injury muscles below the injury deteriorate. This decline in muscle quality includes a loss of mass and of the muscle fibers that are the most resistant to fatigue. Electrical stimulation has had some success in overcoming these problems but there are limitations. Conventional stimulation evokes contractions by activating the surviving motor nerves to the muscles through electrodes on the skin. This activates the muscle fibers that fatigue most rapidly, leaving the fatigue resistant fibers relatively inactive. Recently, I have shown that by applying stimulation at higher frequencies and with wider pulse widths, extra contractions develop, beyond that due to the direct muscle stimulation. These "extra" contractions are generated by signals traveling through reflex pathways to and from the spinal cord. This activates muscle fibers in a more natural manner, with the most fatigue-resistant being activated first. Thus, it may be possible to utilize this spinal mechanism to activate the fatigue-resistant muscle fibers, which are not activated by tradition electrical stimulation, as well as the fast-fatigable fibers thus improving the effectiveness of the stimulation for improving muscle quality. This proposal describes experiments designed to establish whether these modified stimulation parameters will be more effective at maintaining muscle quality and generating contraction for rehabilitation than presently used protocols. The specific aims are; 1. Identify the extent to which signals travelling to the brain contribute to the extra contractions. 2. Determine if stimulation applied over a nerve or muscle generates contractions through different mechanisms. 3. Compare the effectiveness of the modified stimulation parameters with traditional stimulation protocols in producing functional movement and overcoming muscle atrophy in a group of spinal cord injured subjects. The results will provide a framework upon which to base further research into the applications for this technique to maintain muscle quality after a spinal cord injury.