De Ruiter C J, De Haan A, Sargeant A J
Department of Muscle and Exercise Physiology, Faculty of Human Movement Sciences, Vrije Universiteit, Amsterdam, The Netherlands.
Acta Physiol Scand. 1995 Apr;153(4):313-24. doi: 10.1111/j.1748-1716.1995.tb09869.x.
Rat medial gastrocnemius (GM) muscle is a compartmentalized muscle. The functional properties and fibre type composition of the most proximal and most distal compartment were studied in in situ preparations. The proximal compartment contained predominantly fast twitch oxidative fibres. The distal compartment was mainly composed of fast twitch glycolytic fibres. With the use of two small electrodes placed around the primary nerve branches, both compartments could be separately stimulated within the same muscle. The length-force relationship was less broad and maximal twitch and tetanic forces were obtained at lower muscle lengths for the proximal compartment. The differences (mm) were 0.9 +/- 0.2 and 1.2 +/- 0.2 for maximal twitch and tetanic force (120 Hz) production, respectively (P < 0.001). The shortening velocity for maximal power production was lower (P < 0.001) for the proximal compartment (proximal: 57.1 +/- 2.7 mm s-1, distal: 73.1 +/- 3.0 mm s-1). During a standard fatigue test the fatiguability was significantly lower for the proximal compared with the distal fibres. Our findings suggest that the proximal compartment is likely to be activated in vivo during activities requiring relatively low power outputs for longer time periods. In contrast the distal compartment is probably recruited only during high power demanding short lasting activities. The presented model makes it possible to study fatigue related changes in power production of the 'red' and 'white' areas of the GM separately in a way that is probably meaningful with respect to in vivo function.
大鼠腓肠肌内侧头（GM）是一种具有分区的肌肉。在原位制备中研究了最近端和最远端分区的功能特性和纤维类型组成。近端分区主要包含快肌纤维氧化型纤维。远端分区主要由快肌纤维糖酵解型纤维组成。通过在主要神经分支周围放置两个小电极，可以在同一块肌肉内分别刺激两个分区。近端分区的长度 - 力关系范围较窄，并且在较低肌肉长度时获得最大抽搐力和强直收缩力。最大抽搐力和强直收缩力（120Hz）产生时的差异（mm）分别为0.9±0.2和1.2±0.2（P < 0.001）。近端分区产生最大功率时的缩短速度较低（P < 0.001）（近端：57.1±2.7mm s -1，远端：73.1±3.0mm s -1）。在标准疲劳试验中，近端纤维的疲劳性明显低于远端纤维。我们的研究结果表明，在需要相对低功率输出较长时间的活动中，近端分区可能在体内被激活。相反，远端分区可能仅在高功率需求的短暂活动期间被募集。所提出的模型使得能够以一种可能与体内功能相关的有意义的方式分别研究GM“红色”和“白色”区域功率产生中与疲劳相关的变化。
