Kirwan J P, O'Gorman D J, Cyr-Campbell D, Campbell W W, Yarasheski K E, Evans W J
Noll Physiological Research Center, Penn State University, University Park, PA 16802, USA.
Med Sci Sports Exerc. 2001 Sep;33(9):1517-23. doi: 10.1097/00005768-200109000-00015.
To determine whether eating a breakfast cereal with a moderate glycemic index could alter substrate utilization and improve exercise duration.
Six active women (age, 24 +/- 2 yr; weight, 62.2 +/- 2.6 kg; VO(2peak), 46.6 +/- 3.8 mL x kg(-1) x min(-1)) ate 75 g of available carbohydrate in the form of regular whole grain rolled oats (RO) mixed with 300 mL of water or water alone (CON). The trials were performed in random order and the meal or water was ingested 45 min before performing cycling exercise to exhaustion (60% of VO(2peak)). Blood samples were drawn for glucose, glucose kinetics, free fatty acids (FFA), glycerol, insulin, epinephrine (EPI), and norepinephrine (NE) determination. A muscle biopsy was obtained from the vastus lateralis muscle before the trial and immediately after exercise for glycogen determination. Glucose kinetics (Ra) were determined using a [6,6-(2)H] glucose tracer.
Compared with CON, plasma FFA and glycerol levels were suppressed (P < 0.05) during the first 120 min of exercise for the RO trial. Respiratory exchange ratios (RER) were also higher (P < 0.05) for the first 120 min of exercise for the RO trial. At exhaustion, glucose, insulin, FFA, glycerol, EPI, NE, RER, and muscle glycogen were not different between trials. Glucose Ra was greater (P < 0.05) during the RO trial compared with CON (2.36 +/- 0.22 and 1.92 +/- 0.27 mg x kg(-1) x min(-1), respectively). Exercise duration was 5% longer during RO, but the mean times were not significantly different (253.6 +/- 6 and 242.0 +/- 15 min, respectively).
Increased hepatic glucose output before fatigue provides some evidence of glucose sparing after the breakfast cereal trial. However, exercise duration was not significantly altered, possibly because of the sustained suppression of lipid metabolism and increased carbohydrate utilization throughout much of the exercise period.
确定食用具有适度血糖生成指数的早餐谷物是否会改变底物利用并延长运动持续时间。
六名活跃女性（年龄，24±2岁；体重，62.2±2.6千克；峰值摄氧量，46.6±3.8毫升·千克⁻¹·分钟⁻¹）分别食用75克以普通全谷物燕麦片（RO）形式存在的可利用碳水化合物并混合300毫升水，或仅饮用300毫升水（对照组）。试验按随机顺序进行，在进行骑自行运动至力竭（峰值摄氧量的60%）前45分钟摄入餐食或水。采集血样以测定血糖水平、葡萄糖动力学、游离脂肪酸（FFA）、甘油、胰岛素、肾上腺素（EPI）和去甲肾上腺素（NE）。在试验前以及运动结束后立即从股外侧肌获取肌肉活检样本以测定糖原。使用[6,6-(²)H]葡萄糖示踪剂测定葡萄糖动力学（Ra）。
与对照组相比，在RO试验中运动的前120分钟内，血浆FFA和甘油水平受到抑制（P<0.05）。在RO试验中运动的前120分钟内，呼吸交换率（RER）也更高（P<0.05）。在力竭时，各试验组之间的血糖、胰岛素、FFA、甘油、EPI、NE、RER和肌肉糖原无差异。与对照组相比，RO试验期间的葡萄糖Ra更高（P<0.05）（分别为2.36±±0.22和1.92±0.27毫克·千克⁻¹·分钟⁻¹）。RO试验期间运动持续时间长5%，但平均时间无显著差异（分别为253.6±6和242.0±15分钟）。
疲劳前肝脏葡萄糖输出增加为早餐谷物试验后葡萄糖节约提供了一些证据。然而，运动持续时间没有显著改变，这可能是由于在大部分运动期间脂质代谢持续受到抑制以及碳水化合物利用增加所致。
