Kamen Gary, Sullivan Ryan, Rubinstein Scott, Christie Anita
Department of Exercise Science, Totman 160A, University of Massachusetts - Amherst, 01003, USA.
J Electromyogr Kinesiol. 2006 Feb;16(1):25-31. doi: 10.1016/j.jelekin.2005.06.008. Epub 2005 Aug 15.
Motoneurons demonstrate a type of self-sustained firing behavior that seems to be produced by a prolonged period of depolarization caused by intrinsic long-term changes in the motoneuron. Such self-sustained firing behavior has previously been reported in human motor units. The purpose of the present study was to investigate the occurrence of self-sustained firing behavior in older adults. Eight young (mean age 24 yrs) and eight older (mean age 73 yrs) individuals participated in the investigation. While subjects produced light dorsiflexion contractions, a brief vibration stimulus was applied to the tibialis anterior muscle. Motor unit recordings were also obtained from the tibialis anterior muscle. Self-sustained firing behavior was evidenced by the appearance of new motor unit recruitment following vibration, even as the motor units that fired before the vibratory stimulus maintained a steady firing rate. The proportion of motor units exhibiting self-sustained firing activity was similar in both young and older adults (approx. 23% of trials). We conclude that self-sustained firing behavior is a ubiquitous phenomenon that does not seem to be affected by the aging process.
运动神经元表现出一种自我维持的放电行为，这种行为似乎是由运动神经元内在的长期变化引起的长时间去极化所产生的。此前在人类运动单位中已报道过这种自我维持的放电行为。本研究的目的是调查老年人中自我维持放电行为的发生情况。八名年轻人（平均年龄24岁）和八名老年人（平均年龄73岁）参与了这项研究。当受试者进行轻度背屈收缩时，对胫骨前肌施加短暂的振动刺激。同时也从胫骨前肌获取运动单位记录。自我维持的放电行为表现为在振动后出现新的运动单位募集，即使在振动刺激前放电的运动单位保持稳定的放电率。在年轻人和老年人中，表现出自我维持放电活动的运动单位比例相似（约占试验的23%）。我们得出结论，自我维持的放电行为是一种普遍存在的现象，似乎不受衰老过程的影响。
