Department of Neurobiology, Poznań University of Physical Education, Poznań, Poland; and
Department of Neurobiology, Poznań University of Physical Education, Poznań, Poland; and.
J Appl Physiol (1985). 2017 Sep 1;123(3):664-673. doi: 10.1152/japplphysiol.00121.2017. Epub 2017 Jun 8.
Resistance training, with repeated short-term and high-intensity exercises, is responsible for an increase in muscle mass and force. The aim of this study was to determine whether such training induces adaptations in the electrophysiological properties of motoneurons innervating the trained muscles and to relate these adaptive changes to previous observations made on motor unit contractile properties. The study was performed on adult male Wistar rats. Animals from the training group were subjected to a 5-wk voluntary progressive weight-lifting program, whereas control rats were restricted to standard cage activity. Intracellular recordings from lumbar spinal motoneurons were made under pentobarbital anesthesia. Membrane properties were measured, and rhythmic firing of motoneurons was analyzed. Strength training evoked adaptive changes in both slow- and fast-type motoneurons, indicating their increased excitability. A shorter spike duration, a higher input resistance, a lower rheobase, a decrease in the minimum current required to evoke rhythmic firing, an increase in the maximum frequencies of the early-state firing (ESF) and the steady-state firing (SSF), and an increase in the respective slopes of the frequency-current (/) relationship were observed in fast motoneurons of the trained group. The increase in the maximum ESF and SSF frequencies and an increase in the SSF / slope were also present in slow motoneurons. Higher maximum firing rates of motoneurons as well as higher discharge frequencies evoked at the same level of intracellular depolarization current imply higher levels of tetanic forces developed by motor units over the operating range of force production after strength training. Neuronal responses to weight-lifting training can be observed in altered properties of both slow and fast motoneurons. Motoneurons of trained animals are more excitable, require lower intracellular currents to evoke rhythmic firing, and have the ability to evoke higher maximum discharge frequencies during repetitive firing.
抗阻训练，通过重复的短期高强度运动，导致肌肉质量和力量增加。本研究旨在确定这种训练是否会引起支配训练肌肉的运动神经元的电生理特性发生适应性变化，并将这些适应性变化与之前对运动单位收缩特性的观察结果联系起来。该研究在成年雄性 Wistar 大鼠中进行。训练组的动物接受了为期 5 周的自愿渐进举重计划，而对照组的大鼠则限制在标准笼中活动。在戊巴比妥麻醉下，从腰脊髓运动神经元进行细胞内记录。测量膜特性，并分析运动神经元的节律性放电。力量训练引起了慢肌和快肌运动神经元的适应性变化，表明其兴奋性增加。快肌运动神经元的动作电位时程缩短、输入电阻增加、阈强度降低、引起节律性放电所需的最小电流减少、早期放电（ESF）和稳态放电（SSF）的最大频率增加，以及频率-电流（/）关系的相应斜率增加。训练组的慢肌运动神经元也观察到 ESF 和 SSF 最大频率增加以及 SSF 斜率增加。运动神经元的最大放电频率增加以及在相同的细胞内去极化电流水平下诱发的放电频率增加，意味着在力量训练后，运动单位在产生力的操作范围内产生的强直力水平更高。运动神经元对举重训练的反应可以观察到慢肌和快肌运动神经元的特性发生改变。经过训练的动物的运动神经元更具兴奋性，需要较低的细胞内电流来诱发节律性放电，并且在重复放电期间具有诱发更高最大放电频率的能力。
