Rowlands David S, Thorburn Megan S, Thorp Rhys M, Broadbent Suzanne, Shi Xiaocai
Institute of Food, Nutrition, and Human Health, Massey Univ., Wellington, New Zealand.
J Appl Physiol (1985). 2008 Jun;104(6):1709-19. doi: 10.1152/japplphysiol.00878.2007. Epub 2008 Mar 27.
The ingestion of solutions containing carbohydrates with different intestinal transport mechanisms (e.g., fructose and glucose) produce greater carbohydrate and water absorption compared with single-carbohydrate solutions. However, the fructose-ingestion rate that results in the most efficient use of exogenous carbohydrate when glucose is ingested below absorption-oxidation saturation rates is unknown. Ten cyclists rode 2 h at 50% of peak power then performed 10 maximal sprints while ingesting solutions containing (13)C-maltodextrin at 0.6 g/min combined with (14)C-fructose at 0.0 (No-Fructose), 0.3 (Low-Fructose), 0.5 (Medium-Fructose), or 0.7 (High-Fructose) g/min, giving fructose:maltodextrin ratios of 0.5, 0. 8, and 1.2. Mean (percent coefficient of variation) exogenous-fructose oxidation rates during the 2-h rides were 0.18 (19), 0.27 (27), 0.36 (27) g/min in Low-Fructose, Medium-Fructose, and High-Fructose, respectively, with oxidation efficiencies (=oxidation/ingestion rate) of 62-52%. Exogenous-glucose oxidation was highest in Medium-Fructose at 0.57 (28) g/min (98% efficiency) compared with 0.54 (28), 0.48 (29), and 0.49 (19) in Low-Fructose, High-Fructose, No-Fructose, respectively; relative to No-Fructose, only the substantial 16% increase (95% confidence limits +/-16%) in Medium-Fructose was clear. Total exogenous-carbohydrate oxidation was highest in Medium-Fructose at 0.84 (26) g/min. Although the effect of fructose quantity on overall sprint power was unclear, the metabolic responses were associated with lower perceptions of muscle tiredness and physical exertion, and attenuated fatigue (power slope) in the Medium-Fructose and High-Fructose conditions. With the present solutions, low-medium fructose-ingestion rates produced the most efficient use of exogenous carbohydrate, but fatigue and the perception of exercise stress and nausea are reduced with moderate-high fructose doses.
与单碳水化合物溶液相比，摄入含有不同肠道转运机制的碳水化合物溶液（如果糖和葡萄糖）可产生更高的碳水化合物和水分吸收。然而，当葡萄糖摄入量低于吸收 - 氧化饱和速率时，能实现外源性碳水化合物最有效利用的果糖摄入速率尚不清楚。十名自行车运动员以峰值功率的50%骑行2小时，然后进行10次全力冲刺，同时摄入含有以0.6 g/min的速率的（13）C - 麦芽糊精并分别以0.0（无果糖）、0.3（低果糖）、0.5（中果糖）或0.7（高果糖）g/min的速率摄入（14）C - 果糖的溶液，使得果糖与麦芽糊精的比例分别为0.5、0.8和1.2。在2小时骑行过程中，低果糖组、中果糖组和高果糖组的平均（变异系数百分比）外源性果糖氧化速率分别为0.18（19）、0.27（27）、0.36（27）g/min，氧化效率（=氧化量/摄入速率）为62 - 52%。中果糖组的外源性葡萄糖氧化最高，为0.57（28）g/min（效率98%），而低果糖组、高果糖组、无果糖组分别为0.54（28）、0.48（29）和0.49（19）；相对于无果糖组，只有中果糖组有显著的16%的增加（95%置信区间±16%）较为明显。中果糖组的总外源性碳水化合物氧化最高，为0.84（26）g/min。尽管果糖量对整体冲刺功率的影响尚不清楚，但在中果糖组和高果糖组条件下，代谢反应与较低的肌肉疲劳感和体力消耗感知以及减轻的疲劳（功率斜率）相关。就目前的溶液而言，低 - 中果糖摄入速率能实现外源性碳水化合物的最有效利用，但中等 - 高果糖剂量可减轻疲劳以及运动应激和恶心的感知。
