Brain Research Institute, University of California, Los Angeles, Box 951761, 1320 Gonda Neuroscience and Genetics Building, Los Angeles, California 90095-1761, USA.
Muscle Nerve. 2011 Apr;43(4):489-99. doi: 10.1002/mus.21903. Epub 2011 Feb 8.
Functional overload (FO) of the fast plantaris muscle was studied in treadmill-exercised (FO-Ex) or sedentary (FO-Sed) adult cats.
Mechanical, phenotype, and kinematics analyses were performed.
Plantigrade vs. normal digitigrade posture was observed early post-FO. Relative plantaris mass was greater in FO-Sed (10%) and FO-Ex (60%) cats than in controls 12 weeks post-FO. Specific tension was similar across groups, indicating functional hypertrophy. Fiber size was greater, percent slow fibers higher, percent IIa myosin heavy chain (MHC) higher, and IIx MHC lower in FO-Ex than controls. Twitch and half-relaxation times were longer, and the frequency-tension curve shifted toward that observed in slow muscles. Electromyography (EMG) and tendon force amplitudes during stepping were larger, and the yield (lengthening) phase occurred at a longer muscle length before compared with after FO.
Reshaping the plantaris phenotype was highly dependent on the overload stimulus, indicating that electrical stimulation paradigms used during rehabilitation should be performed with the muscles under "loaded" conditions.
本研究旨在探讨在跑步机运动（FO-Ex）或久坐（FO-Sed）的成年猫中，快速跖肌的功能超负荷（FO）。
进行了机械、表型和运动学分析。
FO 后早期观察到跖行姿势与正常趾行姿势。FO-Sed（10%）和 FO-Ex（60%）猫的跖肌相对质量大于 FO 后 12 周的对照组。各组的比张力相似，表明存在功能性肥大。FO-Ex 组的纤维大小较大，慢纤维百分比较高，IIa 型肌球蛋白重链（MHC）百分比较高，而 IIx MHC 百分比较低。在 FO-Ex 组，比对照组的颤搐和半松弛时间更长，频率-张力曲线向慢肌观察到的曲线转移。在步态过程中，肌电图（EMG）和肌腱力振幅较大，与 FO 前相比，在较长的肌肉长度下发生屈服（延长）阶段。
跖肌表型的重塑高度依赖于超负荷刺激，这表明康复过程中使用的电刺激方案应在肌肉“受力”的情况下进行。
