老年人和年轻人比目鱼肌H反射增益：身体位置引起的调节
Soleus H-reflex gain in elderly and young adults: modulation due to body position.
作者信息
Angulo-Kinzler R M, Mynark R G, Koceja D M
机构信息
Department of Kinesiology, Indiana University, Bloomington, USA.
出版信息
J Gerontol A Biol Sci Med Sci. 1998 Mar;53(2):M120-5. doi: 10.1093/gerona/53a.2.m120.
BACKGROUND
The control of posture and balance in the elderly is a primary health concern. Postural instability directly leads to a greater incidence of falling in the elderly population. One important neuromuscular mechanism instrumental in the control of posture and balance is the reflex system. The purpose of this study was to examine the gain of the soleus H-reflex in young and elderly adults in two different body positions: standing and prone.
METHODS
Eighteen neurologically healthy volunteers were categorized by age in two groups: young (n = 9, mean age = 23.3 yr) and elderly (n = 9, mean age = 71.7 yr). In each position, the resting H-max/M-max ratio was determined. The gain of the reflex was also assessed by instructing the subject to perform voluntary contractions of 10, 20 and 30% of their maximum voluntary contraction, using real-time EMG biofeedback. Data were sampled on-line using custom designed software (sample rate = 2 kHz). Dependent variables included the average background EMG of the soleus muscle (40 ms window prior to stimulation) and the peak-to-peak amplitude of the elicited soleus H-reflex. To examine the gain of the reflex, the peak-to-peak amplitude of the H-reflex was plotted against the background EMG activity for each contraction intensity.
RESULTS
Results indicated the following: young subjects significantly depressed the H-max/M-max ratio when standing (69.3% prone, 55.1% standing), whereas elderly subjects increased the ratio (36.1% prone, 54.5% standing). Also, the young subjects modulated the gain of the reflex from prone to standing (3.30 prone, 3.68 standing), and the elderly subjects demonstrated no gain modulation in the different body positions (2.23 prone, 1.91 standing). In both body positions the young subjects demonstrated significantly higher gain that the elderly subjects.
CONCLUSIONS
The results demonstrate different control strategies for young and elderly subjects between prone and standing body positions.
背景
老年人的姿势和平衡控制是主要的健康关注点。姿势不稳直接导致老年人群中跌倒发生率更高。在姿势和平衡控制中起重要作用的一种神经肌肉机制是反射系统。本研究的目的是在两种不同体位（站立和俯卧）下，检查年轻人和老年人比目鱼肌H反射的增益。
方法
18名神经功能健康的志愿者按年龄分为两组：年轻组（n = 9，平均年龄 = 23.3岁）和老年组（n = 9，平均年龄 = 71.7岁）。在每个体位下，测定静息时的H最大值/M最大值比值。还通过指导受试者使用实时肌电图生物反馈进行最大自主收缩的10%、20%和30%的自主收缩，来评估反射增益。使用定制设计软件（采样率 = 2 kHz）在线采样数据。因变量包括比目鱼肌的平均背景肌电图（刺激前40毫秒窗口）和诱发的比目鱼肌H反射的峰峰值幅度。为了检查反射增益，针对每个收缩强度，将H反射的峰峰值幅度与背景肌电图活动作图。
结果
结果表明：年轻受试者站立时显著降低了H最大值/M最大值比值（俯卧时为69.3%，站立时为55.1%），而老年受试者则增加了该比值（俯卧时为36.1%，站立时为54.5%）。此外，年轻受试者从俯卧到站立时调节了反射增益（俯卧时为3.30，站立时为3.68），而老年受试者在不同体位下未表现出增益调节（俯卧时为2.23，站立时为1.91）。在两种体位下，年轻受试者的增益均显著高于老年受试者。
结论
结果表明年轻人和老年人在俯卧和站立体位之间存在不同的控制策略。
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