Center for Medical Physics and Biomedical Engineering, Medical University of Vienna, Vienna, Austria.
School of Sport and Exercise Sciences, Liverpool John Moores University, Liverpool, United Kingdom.
PLoS One. 2018 Nov 20;13(11):e0207886. doi: 10.1371/journal.pone.0207886. eCollection 2018.
The influence of loading on muscular hypertrophy has previously been studied in rodents by removal of synergistic muscles or various weight-lifting regimes. We present a novel model, evoking hypertrophy in the rat's tibialis anterior (TA) muscle by means of an implanted single channel electrical nerve stimulator. The amount of load experienced by the TA was measured in acute experiments in anaesthetized rats with contractions over a range of stimulation frequency and amplitude. A novel electrode configuration allowed us to elicit concentric, isometric and eccentric contractions within the same setup. This was achieved by 'SpillOver' stimulation in which we adjusted the amount of co-activation of the stronger antagonistic plantarflexors by increasing the stimulus above the level that caused full recruitment of the dorsiflexor muscles. The effect of loading on hypertrophy of the TA was tested in 3-4 week stimulation experiments in two groups of freely-moving rats, with a protocol that resembles typical resistance-training in humans. One group performed concentric contractions with no antagonistic co-contraction (unloaded, UNL, n = 5). In the other group the TA was loaded by simultaneous co-contraction of the antagonistically acting plantarflexors (SpillOver, n = 5). The wet mass of the stimulated TA increased in both groups; by 5.4 ± 5.5% for the UNL-group and 13.9 ± 2.9% for the SpillOver-group, with significantly greater increase in the SpillOver-group (p<0.05). Our results correlate well with values reported in literature, demonstrating that SpillOver-stimulation is a suitable model in which to study muscular hypertrophy. Even higher gains in muscle-mass may be possible by optimizing and adjusting the stimulation parameters according to the principles of progressive resistance training.
加载对肌肉肥大的影响以前在啮齿动物中通过去除协同肌肉或各种举重方案进行了研究。我们提出了一种新的模型，通过植入的单通道电神经刺激器在大鼠的胫骨前肌（TA）中引起肥大。在麻醉大鼠的急性实验中，通过测量在刺激频率和幅度范围内的收缩，测量 TA 经历的负荷量。一种新的电极配置允许我们在同一设置中引发向心性、等长和离心收缩。这是通过“溢出”刺激来实现的，其中我们通过将刺激增加到引起背屈肌完全募集的水平以上，来调整更强拮抗的跖屈肌的共同激活量。在两组自由移动的大鼠中进行了 3-4 周的刺激实验，测试了加载对 TA 肥大的影响，该方案类似于人类的典型抗阻训练。一组进行无拮抗共同收缩的向心性收缩（未加载，UNL，n = 5）。在另一组中，通过同时拮抗收缩的跖屈肌来加载 TA（溢出，n = 5）。刺激 TA 的湿质量在两组中均增加；UNL 组增加 5.4±5.5%，溢出组增加 13.9±2.9%，溢出组增加显著（p<0.05）。我们的结果与文献报道的值很好地相关，表明溢出刺激是研究肌肉肥大的合适模型。通过根据渐进性抗阻训练的原则优化和调整刺激参数，甚至可以获得更高的肌肉质量增加。
