MOTOR-UNIT DISCHARGE RATES IN MAXIMAL VOLUNTARY CONTRACTIONS OF 3 HUMAN MUSCLES
MOTOR-UNIT DISCHARGE RATES IN MAXIMAL VOLUNTARY CONTRACTIONS OF 3 HUMAN MUSCLES
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DOI：
10.1152/jn.1983.50.6.1380
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发表时间：
1983-01-01
影响因子：
2.5
通讯作者：
BIGLANDRITCHIE, B
中科院分区：
文献类型：
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作者：
BELLEMARE, F;WOODS, JJ;BIGLANDRITCHIE, B
使用钨微电极记录最大自主收缩时单个运动单位的放电率。4名受试者的300多个单位分别从3块肌肉中抽取。这些是二头肌、拇收肌和比目鱼肌，因为它们的纤维类型组成和收缩特性有已知的差异而被选中。在所有情况下，通过在自愿收缩期间提供单次超最大电击来确保收缩最大。如果没有产生额外的力量，所有的发动机单元都被认为是完全激活的。对于每一块肌肉，由最大的自愿努力引起的激发速率足以在每个运动单元中产生完全融合的破伤风。对于二头肌和拇收肌，平均放电率(.+-.SD)为31.1。+-。10.0和29.9+-。8.6赫兹，而比目鱼肌仅为10.7±-。2.9赫兹。各肌肉分布的放电率约为平均值的4倍。每块肌肉的平均放电率与它们各自的抽搐收缩和半放松时间大致成正比。这些测量二头肌和拇收肌收缩时间的结果与报道的人类快速抽动运动单位的平均值一致，而比目鱼肌的收缩时间测量结果则落在人类慢抽动单位的观察范围内。为了响应自愿的努力，每个机动单元池的放电率范围被限制在仅足以在每个机动单元中产生最大力的范围内。这一建议是基于在最大自主收缩时观察到的运动单位发射频率的范围、其收缩时间的范围和产生最大力量所需的刺激频率之间的关系。讨论了这一假设对运动控制的影响。
Single motor-unit firing rates were recorded during maximal voluntary contractions using tungsten microelectrodes. Over 300 units from 4 subjects were sampled from each of 3 muscles. These were the biceps brachii, adductor pollicis and soleus, chosen because of known differences in their fiber-type composition and contractile properties. In all cases the contraction maximality was assured by delivering single supramaximal shocks during the voluntary contractions. All motor units were deemed fully activated if no additional force resulted. For each muscle, the firing rates elicited by a maximal voluntary effort are sufficient to generate a fully fused tetanus in each motor unit. For the biceps brachii and adductor pollicis muscles, the mean firing rates (.+-. SD) were 31.1 .+-. 10.0 and 29.9 .+-. 8.6 Hz, respectively, while for soleus they were only 10.7 .+-. 2.9 Hz. The firing rates of each muscle distribution covered approximately a 4-fold range about the mean value. The mean firing rates for each muscle varied roughly in proportion to their respective twitch contraction and half relaxation times. These contractile time measurements for both biceps brachii and adductor pollicis agreed well with the mean values reported for human fast-twitch motor units, while those for soleus fell in the range observed for human slow-twitch units. In response to voluntary effort, the range of discharge rates of each motor-unit pool is limited to those only just sufficient to produce maximum force in each motor unit. This suggestion is based on the relationship between the range of motor-unit firing frequencies observed during maximum voluntary contractions, their range of contraction times, and the stimulation frequencies required for maximum force generation. The implications of this hypothesis for motor control are discussed.