Haman François, Legault Stéphane R, Rakobowchuk Mark, Ducharme Michel B, Weber Jean-Michel
Biology Dept., Univ. of Ottawa, 30 Marie Curie, Ottawa, Ontario, Canada K1N 6N5.
J Appl Physiol (1985). 2004 Jan;96(1):41-9. doi: 10.1152/japplphysiol.00428.2003. Epub 2003 Aug 29.
The purpose of this study was to quantify how shivering activity would be affected by large changes in fuel metabolism (see Haman F, Peronnet F, Kenny GP, Doucet E, Massicotte D, Lavoie C, and Weber J-M, J Appl Physiol 96: 000-000, 2004). Adult men were exposed to 10 degrees C for 2 h after a low-carbohydrate diet and exercise (Lo) and after high-carbohydrate diet without exercise (Hi). Using simultaneous metabolic and electromyographic (EMG) measurements, we quantified the effects of changes in fuel selection on the shivering activity of eight large muscles representing >90% of total shivering muscle mass. Contrary to expectation, drastic changes in fuel metabolism [carbohydrates 28 vs. 65% of total heat production (Hprod), lipids 53 vs. 23% Hprod, and proteins 19 vs. 12% Hprod for Lo and Hi, respectively] are achieved without altering the EMG signature of shivering muscles. Results show that total shivering activity and the specific contribution of each muscle to total shivering activity are not affected by large changes in fuel selection. In addition, we found that changes in burst shivering rate ( approximately 4 bursts/min), relative contribution of burst activity to total shivering ( approximately 10% of total shivering activity), and burst shivering intensity ( approximately 12% of maximal voluntary contraction) are the same between Lo and Hi. Spectral analysis of EMG signals also reveals that mean frequencies of the power spectrum remained the same under all conditions (whole body average of 78 +/- 5 Hz for Lo and 83 +/- 7 Hz for Hi). During low-intensity shivering, humans are therefore able to sustain the same thermogenic rate by oxidizing widely different fuel mixtures within the same muscle fibers.
本研究的目的是量化燃料代谢的大幅变化如何影响寒颤活动（见哈曼F、佩罗内F、肯尼GP、杜塞特E、马西科特D、拉沃伊C和韦伯J - M，《应用生理学杂志》96: 000 - 000，2004年）。成年男性在低碳水化合物饮食和运动后（低组）以及高碳水化合物饮食且无运动后（高组），暴露于10摄氏度环境2小时。通过同时进行代谢和肌电图（EMG）测量，我们量化了燃料选择变化对代表超过90%寒颤肌肉总质量的八块大肌肉寒颤活动的影响。与预期相反，在不改变寒颤肌肉的肌电图特征的情况下，实现了燃料代谢的剧烈变化[低组和高组碳水化合物分别占总产热（Hprod）的28%和65%，脂质分别占53%和23% Hprod，蛋白质分别占19%和12% Hprod]。结果表明，总寒颤活动以及每块肌肉对总寒颤活动的特定贡献不受燃料选择大幅变化的影响。此外，我们发现寒颤爆发率的变化（约4次/分钟）、爆发活动对总寒颤的相对贡献（约占总寒颤活动的10%）以及寒颤爆发强度（约占最大自主收缩的12%）在低组和高组之间是相同的。EMG信号的频谱分析还表明，在所有条件下功率谱的平均频率保持不变（低组全身平均值为78±5赫兹，高组为83±7赫兹）。因此，在低强度寒颤期间，人类能够通过在同一肌纤维内氧化广泛不同的燃料混合物来维持相同的产热率。
