Jeukendrup Asker E, Moseley Luke, Mainwaring Gareth I, Samuels Spencer, Perry Samuel, Mann Christopher H
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, United Kingdom.
J Appl Physiol (1985). 2006 Apr;100(4):1134-41. doi: 10.1152/japplphysiol.00981.2004. Epub 2005 Dec 1.
The purposes of this study were: 1) to obtain a measure of exogenous carbohydrate (CHO(Exo)) oxidation and plasma glucose kinetics during 5 h of exercise; and 2) to compare CHO(Exo) following the ingestion of a glucose solution (Glu) or a glucose + fructose solution (2:1 ratio, Glu+Fru) during ultraendurance exercise. Eight well-trained subjects exercised three times for 5 h at 58% maximum O2 consumption while ingesting either Glu or Glu+Fru (both delivering 1.5 g/min CHO) or water. The CHO used had a naturally high 13C enrichment, and five subjects received a primed continuous intravenous [6,6-2H2]glucose infusion. CHO(Exo) rates following the ingestion of Glu leveled off after 120 min and peaked at 1.24 +/- 0.04 g/min. The ingestion of Glu+Fru resulted in a significantly higher peak rate of CHO(Exo) (1.40 +/- 0.08 g/min), a faster rate of increase in CHO(Exo), and an increase in the percentage of CHO(Exo) oxidized (65-77%). However, the rate of appearance and disappearance of Glu continued to increase during exercise, with no differences between trials. These data suggest an important role for gluconeogenesis during the later stages of exercise. Following the ingestion of Glu+Fru, cadence (rpm) was maintained, and the perception of stomach fullness was reduced relative to Glu. The ingestion of Glu+Fru increases CHO(Exo) compared with the ingestion of Glu alone, potentially through the oxidation of CHO(Exo) in the liver or through the conversion to, and oxidation of, lactate.
1）测量运动5小时期间外源性碳水化合物（CHO(Exo)）的氧化及血浆葡萄糖动力学；2）比较超耐力运动期间摄入葡萄糖溶液（Glu）或葡萄糖+果糖溶液（2:1比例，Glu+Fru）后CHO(Exo)的情况。八名训练有素的受试者在摄氧量为最大摄氧量58%的情况下进行三次5小时的运动，期间分别摄入Glu或Glu+Fru（两者均提供1.5 g/min的CHO）或水。所使用的CHO具有天然高13C富集度，五名受试者接受了一次性静脉注射[6,6-2H2]葡萄糖的持续输注。摄入Glu后，CHO(Exo)速率在120分钟后趋于平稳，并在1.24±0.04 g/min达到峰值。摄入Glu+Fru导致CHO(Exo)的峰值速率显著更高（1.40±0.08 g/min），CHO(Exo)的增加速率更快，且CHO(Exo)氧化百分比增加（65-77%）。然而，运动期间Glu的出现和消失速率持续增加，各试验之间无差异。这些数据表明糖异生在运动后期发挥重要作用。摄入Glu+Fru后，步频（rpm）得以维持，且相对于Glu，胃部饱腹感的感知有所降低。与单独摄入Glu相比，摄入Glu+Fru可增加CHO(Exo)，这可能是通过肝脏中CHO(Exo)的氧化或通过转化为乳酸并氧化实现的。
