The effect of the stimulation pattern on the fatigue of single motor units in adult cats.
The effect of the stimulation pattern on the fatigue of single motor units in adult cats.
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刺激模式对成年猫单个运动单位疲劳的影响。
DOI：
10.1113/jphysiol.1992.sp019076
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发表时间：
1992
期刊：
影响因子：
--
通讯作者：
Stuart,DG
中科院分区：
文献类型：
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作者：
Bevan,L;Laouris,Y;Reinking,RM;Stuart,DG
1. 本研究的主要目的是研究两种微妙不同的刺激模式对猫后肢肌肉在控制（预疲劳）和疲劳收缩期间快速抽搐、疲劳运动单元所产生的力的影响。2. 在360秒疲劳试验中，测量了5只深度麻醉的成年猫胫骨后肌19个高疲劳（FF）运动单元和3个中疲劳（FI）运动单元的峰值力和力-时间积分响应。3. 疲劳试验包括两种刺激模式的伪随机交替。一种模式（规则）由一系列脉冲间隔恒定的刺激组成，设定为每个单位抽动收缩时间的1.8倍（间隔范围，27 - 51毫秒），并提供500（或400）ms.对于总的（FF + FI）运动单位样本，平均（+/‐sd）刺激频率为26 +/‐4 Hz（范围，19 - 37 Hz）。另一种刺激模式（优化后的）包括三个脉冲间隔较短（10毫秒）的初始刺激，随后是一个恒定的脉冲间隔序列（间隔范围为29 - 62毫秒；频率为23 +/ - 5赫兹；频率范围为16 - 36赫兹），使整个序列具有与常规序列相同的脉冲数量、平均频率和持续时间。4. 刺激序列以1秒1的速度持续360秒，每种模式使用三个训练序列，随机交替进行。选取每个序列中第三列的响应进行力测量。随后，将疲劳试验获得的力分布分解为两个分布：一个归因于常规刺激，一个归因于优化刺激。5. 在疲劳试验的初始响应中，优化后的刺激模式产生的力明显大于常规的刺激模式。对于FF单元，峰值力的平均增加（141%）明显大于力-时间积分的增加（59%）。6. 所有运动单元在常规刺激模式下均表现出峰值力的初始增强，而在优化模式下，峰值力单调下降。相比之下，对于规则和优化的刺激模式，力-时间积分在前30秒增强。7. 在疲劳测试期间，每个运动单元对优化刺激的力响应都保持增加，最大的相对增加发生在测试开始后120秒左右，在增强效应消退后很长时间。（摘要删节为400字）
1. The main purpose of this study was to examine the effects of two subtly different stimulus patterns on the force developed by fast‐twitch, fatiguable motor units in a cat hindlimb muscle during control (pre‐fatigue) and fatiguing contractions. 2. The peak force and the force‐time integral responses of nineteen high fatigue (FF) and three intermediate fatigue (FI) motor units of the tibialis posterior muscle in five deeply anaesthetized adult cats were measured at selected times during the course of a 360‐s fatigue test. 3. The fatigue test involved a pseudo‐random alternation of two patterns of stimulation. One pattern (regular) was composed of a train of stimuli with constant interpulse intervals, set at 1.8 x the twitch contraction time of each unit (interval range, 27‐51 ms), and delivered for 500 (or 400) ms. For the total (FF + FI) motor‐unit sample, the mean (+/‐ S.D.) stimulation frequency was 26 +/‐ 4 Hz (range, 19‐37 Hz). The other stimulus pattern (optimized) consisted of three initial stimuli with short (10 ms) interpulse intervals, followed by a constant interpulse‐interval train that was adjusted (interval range, 29‐62 ms; frequency, 23 +/‐ 5 Hz; frequency range, 16‐36 Hz) such that the total train had the same number of pulses, and the same average frequency and duration as the regular train. 4. The stimulus trains were delivered at 1 s‐1 for 360 s, using three‐train sequences of each pattern, randomly alternating with one another. The response of the third train in each sequence was selected for the force measurements. The force profile obtained from the fatigue test was subsequently decomposed into two profiles: one attributable to regular and one to optimized stimulation. 5. During the initial responses to the fatigue test, the optimized stimulus pattern produced significantly more force than the regular stimulus pattern. For FF units, the mean increase in peak force (141%) was significantly greater than the increase in the force‐time integral (59%). 6. All motor units exhibited an initial potentiation of peak force with the regular stimulation pattern, whereas peak force declined monotonically with the optimized pattern. In contrast, the force‐time integral potentiated in the first 30 s for both regular and optimized stimulus patterns. 7. Each motor unit maintained an increased force response to optimized stimulation during the fatigue test, with the greatest relative increase occurring about 120 s into the test, well after the potentiation effect had subsided.(ABSTRACT TRUNCATED AT 400 WORDS)