Sartorio A, Jubeau M, Agosti F, De Col A, Marazzi N, Lafortuna C L, Maffiuletti N A
Istituto Auxologico Italiano, IRCCS, Divisione Malattie Metaboliche 3 and Laboratorio Sperimentale di Ricerche Auxo-Endocrinologiche, 28921 Verbania, Italy.
Eur J Endocrinol. 2008 Mar;158(3):311-6. doi: 10.1530/EJE-07-0775.
It is well established that repeated GHRH administration or repeated voluntary exercise bouts are associated with a complete blunting of GH responsiveness when the administration of the second stimulus follows the first one after a 2-h interval.
To evaluate GH responses to neuromuscular electrical stimulation (NMES) in healthy adults.
Six volunteers (mean age+/-s.d. 31.7+/-5.5 years) were studied before and after two consecutive bouts of NMES exercise (a series of 20 contractions at the maximum of individual tolerance, frequency: 75 Hz, pulse duration: 400 mus, on-off ratio: 6.25-20 s) administered at a 2-h interval.
Baseline GH levels (mean: 0.3+/-0.2 ng/ml) significantly increased after the first NMES (peak: 4.2+/-3.7 ng/ml), with a complete normalization after 120 min (0.3+/-0.3 ng/ml). The administration of the second bout of NMES of comparable characteristics also resulted in a significant GH increase (peak: 5.2+/-3.2 ng/ml), which was comparable with that observed after the previous one. GH net incremental area under the curve after the first and second bouts of NMES were not significantly different (155.1+/-148.5 and 176.9+/-123.3 ng/ml per h, P=0.785).
Unlike repeated pharmacological stimuli and voluntary exercise bouts, subsequent sessions of NMES administered at a 2-h interval appear to circumvent feedback mechanisms and to re-induce the GH responses, thus indicating a possible different underlying mechanism elicited by different GH-releasing stimuli.
众所周知，当在2小时间隔后给予第二次刺激时，重复给予生长激素释放激素（GHRH）或重复进行自愿性运动发作与生长激素（GH）反应性的完全减弱有关。
评估健康成年人对神经肌肉电刺激（NMES）的GH反应。
对6名志愿者（平均年龄±标准差31.7±5.5岁）在连续两次NMES运动发作（一系列20次收缩，达到个体最大耐受程度，频率：75赫兹，脉冲持续时间：400微秒，开-关比：6.25 - 20秒）前后进行研究，两次发作间隔2小时。
第一次NMES后，基线GH水平（平均：0.3±0.2纳克/毫升）显著升高（峰值：4.2±3.7纳克/毫升），120分钟后完全恢复正常（0.3±0.3纳克/毫升）。给予具有相似特征的第二次NMES发作也导致GH显著升高（峰值：5.2±3.2纳克/毫升），与前一次观察到的结果相当。第一次和第二次NMES发作后GH曲线下净增量面积无显著差异（分别为155.1±148.5和176.9±123.3纳克/毫升·小时，P = 0.785）。
与重复的药物刺激和自愿性运动发作不同，以2小时间隔给予的后续NMES疗程似乎能规避反馈机制并再次诱导GH反应，从而表明不同的GH释放刺激引发了可能不同的潜在机制。
