Adams Gregory R, Cheng Daniel C, Haddad Fadia, Baldwin Kenneth M
Department of Physiology and Biophysics, University of California Irvine, Irvine, CA 92697-4560, USA.
J Appl Physiol (1985). 2004 May;96(5):1613-8. doi: 10.1152/japplphysiol.01162.2003.
Movements generated by muscle contraction generally include periods of muscle shortening and lengthening as well as force development in the absence of external length changes (isometric). However, in the specific case of resistance exercise training, exercises are often intentionally designed to emphasize one of these modes. The purpose of the present study was to objectively evaluate the relative effectiveness of each training mode for inducing compensatory hypertrophy. With the use of a rat model with electrically stimulated (sciatic nerve) contractions, groups of rats completed 10 training sessions in 20 days. Within each training session, the duration of the stimulation was equal across the three modes. Although this protocol provided equivalent durations of duty cycle, the torque integral for the individual contractions varied markedly with training mode such that lengthening > isometric > shortening. The results indicate that the hypertrophy response did not track the torque integral with mass increases of isometric by 14%, shortening by 12%, and lengthening by 11%. All three modes of training resulted in similar increases in total muscle DNA and RNA. Isometric and shortening but not lengthening mode training resulted in increased muscle insulin-like growth factor I mRNA levels. These results indicate that relatively pure movement mode exercises result in similar levels of compensatory hypertrophy that do not necessarily track with the total amount of force generated during each contraction.
肌肉收缩产生的运动通常包括肌肉缩短和延长的阶段，以及在无外部长度变化情况下的力量发展（等长收缩）。然而，在抗阻训练这一特定情况下，训练动作往往是特意设计来强调其中一种模式的。本研究的目的是客观评估每种训练模式在诱导代偿性肥大方面的相对有效性。利用电刺激（坐骨神经）收缩的大鼠模型，将大鼠分组，在20天内完成10次训练。在每次训练中，三种模式下的刺激持续时间相同。尽管该方案提供了相同的占空比持续时间，但单次收缩的扭矩积分随训练模式有显著变化，即延长收缩＞等长收缩＞缩短收缩。结果表明，肥大反应与扭矩积分并不相关，等长收缩的肌肉质量增加了14%，缩短收缩增加了12%，延长收缩增加了11%。所有三种训练模式均使肌肉总DNA和RNA有相似增加。等长收缩和缩短收缩模式训练而非延长收缩模式训练使肌肉胰岛素样生长因子I mRNA水平升高。这些结果表明，相对纯粹的运动模式训练会导致相似程度的代偿性肥大，且这种肥大不一定与每次收缩产生的总力量相关。
