Kukulka C G, Clamann H P
Brain Res. 1981 Aug 24;219(1):45-55. doi: 10.1016/0006-8993(81)90266-3.
Experiments were designed to assess the relative contribution of rate coding and motor unit recruitment to force production in two muscles of different fiber composition and function. Single motor unit action potentials were recorded during steady isometric contraction in biceps brachii, a large proximal limb muscle of mixed fiber composition, and adductor pollicis, a small hand muscle comprised mainly of type I muscle fibers. Action potential spike trains were obtained over the entire force range in each muscle. The results suggest that these two muscles are controlled in different ways. In biceps brachii, recruitment was observed from 0 to 88% maximum voluntary contraction (MVC). In adductor pollicis, no motor unit was observed to be recruited at forces greater than 50% MVC, with the majority of recruitment occurring below 30% MVC. On the average, motor units in adductor pollicis discharged at higher rates, with less regularity, and with a greater frequency of occurrence of short interspike intervals (intervals less than or equal to 20 msec) than those in biceps brachii. Such findings suggest that rate coding plays a more prominent role in force modulation in adductor pollicis, while recruitment plays a more important role throughout the contractile force range in biceps brachii.
实验旨在评估频率编码和运动单位募集对不同纤维组成和功能的两块肌肉力量产生的相对贡献。在肱二头肌（一种纤维组成混合的近端大肢体肌肉）和拇收肌（一种主要由I型肌纤维组成的小手部肌肉）的等长收缩过程中记录单个运动单位动作电位。在每块肌肉的整个力量范围内获取动作电位脉冲序列。结果表明这两块肌肉的控制方式不同。在肱二头肌中，从0到最大自主收缩（MVC）的88%观察到运动单位募集。在拇收肌中，在力量大于50%MVC时未观察到运动单位募集，大多数募集发生在30%MVC以下。平均而言，拇收肌中的运动单位放电频率更高，规律性更低，与肱二头肌中的运动单位相比，短峰间间隔（间隔小于或等于20毫秒）出现的频率更高。这些发现表明频率编码在拇收肌的力量调节中起更突出的作用，而募集在肱二头肌的整个收缩力量范围内起更重要的作用。
