Loeb G E, Hoffer J A, Pratt C A
J Neurophysiol. 1985 Sep;54(3):549-64. doi: 10.1152/jn.1985.54.3.549.
The naturally occurring activity patterns of anterior thigh muscle spindle afferents were recorded during unrestrained treadmill locomotion by means of floating microelectrodes chronically implanted in the fifth lumbar dorsal root ganglion. Conduction velocity of units from primary and secondary endings was determined by spike-triggered averaging of the signals from a chronically implanted nerve cuff. Activity from knee extensor muscle spindles generally occurred during periods of muscle lengthening, but was often greater for small stretches when the muscle was active (during stance phase of walking) than for larger stretches when the muscle was passive (swing phase), indicating fusimotor enhancement of spindle sensitivity in phase with extrafusal muscle recruitment. Activity from spindles in biarticular muscles acting across the knee and hip was more variable and complex than that seen in the pure knee extensors, and frequently included activity during rapid muscle shortening (swing phase) indicative of strong static fusimotor input. Changes in speed of gait caused changes in the range and velocity of muscle length excursions monitored by chronically implanted length gauges, but such changes were accompanied by only modest changes in spindle afferent activity, suggesting concurrent and compensatory changes in fusimotor influence on spindles. Activity from spindle secondary endings was generally lower, more regular, and less velocity dependent than that from primary endings, consistent with their lack of input from the dynamic fusimotor apparatus. The activity of all spindle afferents studied was similarly well modulated during extrafusal activity of the parent muscles, regardless of the kinematic conditions of muscle length and velocity during which this muscle work occurred. This suggests that the fusimotor apparatus is well orchestrated to regulate the static and dynamic sensitivity of primary spindle afferents at levels appropriate to the anticipated motion.
通过长期植入第五腰段背根神经节的漂浮微电极，在无约束的跑步机运动过程中记录大腿前侧肌梭传入纤维的自然活动模式。通过对长期植入的神经袖套信号进行触发脉冲平均，确定来自初级和次级末梢的单位传导速度。膝伸肌肌梭的活动通常发生在肌肉拉长期间，但当肌肉处于活动状态（步行站立期）时，小幅度拉伸时的活动往往比肌肉处于被动状态（摆动期）时大幅度拉伸时的活动更大，这表明肌梭敏感性的肌动运动增强与梭外肌募集同步。跨越膝关节和髋关节的双关节肌中肌梭的活动比单纯的膝伸肌更具变化性和复杂性，并且在快速肌肉缩短（摆动期）期间经常包括活动，这表明有强烈的静态肌动运动输入。步态速度的变化导致长期植入的长度测量仪监测到的肌肉长度变化范围和速度发生变化，但这种变化仅伴随着肌梭传入活动的适度变化，这表明肌动运动对肌梭的影响同时发生了补偿性变化。肌梭次级末梢的活动通常比初级末梢的活动更低、更规律且对速度的依赖性更小，这与其缺乏来自动态肌动运动装置的输入一致。无论肌肉工作发生时肌肉长度和速度的运动学条件如何，在所研究的所有肌梭传入纤维的活动在其母肌肉的梭外活动期间都同样受到良好的调节。这表明肌动运动装置经过精心编排，以在适合预期运动的水平上调节初级肌梭传入纤维的静态和动态敏感性。
