Le Bozec S, Maton B
Eur J Appl Physiol Occup Physiol. 1987;56(3):350-5. doi: 10.1007/BF00690904.
A comparison was carried out between the motor unit (MU) firing rate and the characteristics of the twitch and the fibre type composition of anconeus and triceps brachii. Fibre type composition (type I, type II) was determined in whole cross-sections of cadaver specimens. The proportion of type I fibre was 60%-67% in anconeus and 32-40% in the lateral head of triceps brachii. Reflecting these histochemical differences, the contraction time of anconeus and triceps was 92 +/- 9 ms and 68 +/- 9 ms respectively. It follows that anconeus can be classified as a slow muscle, as opposed to the lateral head of triceps. The relationship between MU firing rate and isometric force, tested at 90 degrees elbow flexion, differed between the two muscles for force values below 30% of maximal voluntary contraction. No significant increase in MU firing rate was found in anconeus at forces above 5% of maximal voluntary contraction. It is concluded that even within a single agonistic muscle group acting at a single joint there is an adaptation of MU firing rate to the contractile characteristics of each muscle.
对肱三头肌和肘肌的运动单位（MU）放电频率、抽搐特性以及纤维类型组成进行了比较。通过尸体标本的全横截面确定纤维类型组成（I型、II型）。肘肌中I型纤维的比例为60%-67%，肱三头肌外侧头中I型纤维的比例为32%-40%。反映出这些组织化学差异，肘肌和肱三头肌的收缩时间分别为92±9毫秒和68±9毫秒。由此可见，与肱三头肌外侧头相比，肘肌可归类为慢肌。在90度肘屈曲时测试的MU放电频率与等长力量之间的关系，在两种肌肉中，对于低于最大自主收缩30%的力量值有所不同。在肘肌中，当力量高于最大自主收缩的5%时，未发现MU放电频率有显著增加。得出的结论是，即使在作用于单个关节的单个主动肌组内，MU放电频率也会根据每块肌肉的收缩特性进行调整。
