Alaimo M A, Smith J L, Roy R R, Edgerton V R
J Appl Physiol Respir Environ Exerc Physiol. 1984 Jun;56(6):1608-13. doi: 10.1152/jappl.1984.56.6.1608.
Transformations of slow-twitch fibers to the fast-twitch type following spinal cord transection are thought to be related to a substantial decrease or virtual absence of neuromuscular activity. In this experiment, spontaneous activity levels in spinalized and normal cats, raised under similar conditions, were assessed by integrated electromyography (I-EMG) recorded for 240 min over 24 h from the slow-contracting soleus (SOL) and the fast-contracting lateral gastrocnemius (LG). In the SOL of the spinalized cats, there was a 75% reduction in total I-EMG and a 66% reduction in the total duration of muscle activity. Conversely, the LG showed no significant change in total I-EMG, but there was a 66% reduction in the total duration of muscle activity. Based on muscle property data published in companion studies, there was no significant correlation between the SOL total I-EMG and the reduction in contraction times or the decrease in the percentage of slow-twitch fibers determined histochemically. We conclude that transformations of slow-twitch fibers following spinal transection may be regulated by several factors, among which is the total level of spontaneous daily activity.
脊髓横断后慢肌纤维向快肌纤维类型的转变被认为与神经肌肉活动的大幅减少或几乎缺失有关。在本实验中，通过在24小时内从收缩缓慢的比目鱼肌（SOL）和收缩快速的外侧腓肠肌（LG）记录240分钟的积分肌电图（I-EMG），评估了在相似条件下饲养的脊髓损伤猫和正常猫的自发活动水平。在脊髓损伤猫的SOL中，I-EMG总量减少了75%，肌肉活动总时长减少了66%。相反，LG的I-EMG总量没有显著变化，但肌肉活动总时长减少了66%。根据同期研究发表的肌肉特性数据，SOL的I-EMG总量与收缩时间的缩短或组织化学测定的慢肌纤维百分比的降低之间没有显著相关性。我们得出结论，脊髓横断后慢肌纤维的转变可能受多种因素调节，其中包括每日自发活动的总体水平。
