Evans C M, Fellows S J, Rack P M, Ross H F, Walters D K
J Physiol. 1983 Nov;344:483-502. doi: 10.1113/jphysiol.1983.sp014953.
Ankle joints were subjected to sinusoidal movements at a range of amplitudes and frequencies. Records were made of electromyograms (e.m.g.s) in calf muscles, and of the forces at the joints. When the leg is relaxed, the ankle joint resists an imposed sinusoidal movement with a small approximately sinusoidal force. It is stiffer in its resistance to small movements than to large ones, and this resistance is greater when the joint is dorsiflexed than when it is plantarflexed. If the subject exerts a steady mean flexing force, the imposed sinusoidal movement generates reflex activity which may be recorded as a modulation of the gastrocnemius and soleus e.m.g.s. The e.m.g. response to the sinusoidal movement occurs later in cycles of movement at high than at low frequencies, as one could expect of a reflex pathway that involves a delay. The results suggest that this delay is between 50 and 60 ms, and we conclude that under these circumstances spinal stretch reflexes are playing the important part. The relation of the resisting force to the movement has been displayed as a vector. As the frequency changes, this vector describes the circular path that is characteristic of a system which includes delays or lags; this path enables one to draw conclusions about the amplitude and timing of the reflex resistance to the movement. When a subject exerts a moderate flexing force against the sinusoidal movement for some minutes, the reflex response becomes progressively potentiated. A subject whose reflex responses are normally slight may then exhibit a vigorous reflex response to the movement of that ankle. This enhancement of spinal reflex activity was accompanied by an increase in the myotatic reflex response at the ankle. Reflex responses to sinusoidal movement were most clearly seen when the subject exerted a mean flexing force that amounted to about one-fifth of his maximum. Very small movements (+/- 0.5 degrees) generated little or no reflex response. With large amplitudes of movement there was more reflex activity, but at some amplitude (which varied from subject to subject and from time to time) the reflex mechanism appeared to 'saturate', and further increases in amplitude were not accompanied by comparable increases in the reflex response. With movements at 10-15 Hz the e.m.g. response often became large in alternate cycles, with less activity in the intervening cycles.(ABSTRACT TRUNCATED AT 400 WORDS)
踝关节在一系列振幅和频率下进行正弦运动。记录小腿肌肉的肌电图（e.m.g.s）以及关节处的力。当腿部放松时，踝关节以一个小的近似正弦力抵抗施加的正弦运动。它对小幅度运动的抵抗比大幅度运动更僵硬，并且当关节背屈时这种抵抗比跖屈时更大。如果受试者施加稳定的平均弯曲力，施加的正弦运动会产生反射活动，这可以记录为腓肠肌和比目鱼肌肌电图的调制。对正弦运动的肌电图反应在高频运动周期中比在低频运动周期中出现得更晚，正如人们对涉及延迟的反射通路所预期的那样。结果表明这种延迟在50到60毫秒之间，并且我们得出结论，在这些情况下脊髓牵张反射起着重要作用。阻力与运动的关系已表示为一个向量。随着频率变化，这个向量描绘了一个包含延迟或滞后的系统所特有的圆形路径；这条路径使人们能够得出关于对运动的反射阻力的幅度和时间的结论。当受试者对正弦运动施加适度的弯曲力几分钟时，反射反应会逐渐增强。一个反射反应通常很轻微的受试者可能随后会对该踝关节的运动表现出强烈的反射反应。脊髓反射活动的这种增强伴随着踝关节处肌紧张反射反应的增加。当受试者施加相当于其最大值约五分之一的平均弯曲力时，对正弦运动的反射反应最明显。非常小的运动（±0.5度）几乎不产生或不产生反射反应。运动幅度大时反射活动更多，但在某个幅度（因受试者和时间而异）反射机制似乎“饱和”，幅度进一步增加时反射反应不会相应增加。在10 - 15赫兹的运动中，肌电图反应常常在交替周期中变大，中间周期活动较少。（摘要截选至400字）
