Borg J
Muscle Nerve. 1981 Sep-Oct;4(5):429-34. doi: 10.1002/mus.880040513.
The axonal conduction velocity and voluntary discharge properties of single motor units of the extensor digitorum brevis were studied in elderly subjects. The results were compared with the findings of a previous study of younger subjects. The range of the axonal conduction velocities differed only slightly between the age groups, the elderly subjects having velocities of 25-52 m/sec and the younger subjects 30-54 m/sec. In both age groups, motor units firing tonically within the range of 10-30 Hz had axonal conduction velocities below 45 m/sec, and motor units firing mainly phasically within the range of 20-60 Hz had axonal conduction velocities above 40 m/sec. Motor units with an intermediate type of discharge pattern were more frequently seen in the elderly. In the elderly subjects, these motor units had axonal conduction velocities distributed within the whole range, while in the younger subjects, they had axonal conduction velocities in the middle of the range. An autopsy study showed an increased proportion of muscle fibers with intermediate characteristics of ATPase staining in the elderly subjects. It is suggested that the decreased differentiation of the muscle fiber histochemistry might be secondary to the decreased differentiation of the motoneuron firing properties.
对老年受试者趾短伸肌单运动单位的轴突传导速度和随意放电特性进行了研究。将结果与先前对年轻受试者的研究结果进行了比较。轴突传导速度范围在两个年龄组之间仅略有差异，老年受试者的速度为25 - 52米/秒，年轻受试者为30 - 54米/秒。在两个年龄组中，在10 - 30赫兹范围内持续放电的运动单位，其轴突传导速度低于45米/秒，而主要在20 - 60赫兹范围内相位性放电的运动单位，其轴突传导速度高于40米/秒。具有中间型放电模式的运动单位在老年人中更常见。在老年受试者中，这些运动单位的轴突传导速度分布在整个范围内，而在年轻受试者中，它们的轴突传导速度处于该范围的中间。一项尸检研究表明，老年受试者中具有ATP酶染色中间特征的肌纤维比例增加。有人认为，肌纤维组织化学分化的降低可能继发于运动神经元放电特性分化的降低。
