Oxidation of combined ingestion of glucose and fructose during exercise (original) (raw)
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British Journal of Nutrition, 2005
A recent study from our laboratory has shown that a mixture of glucose and fructose ingested at a rate of 1·8 g/min leads to peak oxidation rates of approximately 1·3 g/min and results in approximately 55 % higher exogenous carbohydrate (CHO) oxidation rates compared with the ingestion of an isocaloric amount of glucose. The aim of the present study was to investigate whether a mixture of glucose and fructose when ingested at a high rate (2·4 g/min) would lead to even higher exogenous CHO oxidation rates (>1·3 g/min).Eight trained male cyclists (VO2max: 68±1 ml/kg per min) cycled on three different occasions for 150 min at 50 % of maximal power output (60±1 % VO2max) and consumed either water (WAT) or a CHO solution providing 1·2 g/min glucose (GLU) or 1.2 g/min glucose+1·2 g/min fructose (GLU+FRUC). Peak exogenous CHO oxidation rates were higher (P<0·01) in the GLU+FRUC trial compared with the GLU trial (1·75 (se 0·11) and 1·06 (se 0·05) g/min, respectively). Furthermore, exo...
Oxidation of independent and combined ingested galactose and glucose, during exercise
Journal of Applied Physiology
Co-ingestion of glucose and galactose has been shown to enhance splanchnic extraction and metabolism of ingested galactose at rest; effects during exercise are unknown. This study examined whether combined ingestion of galactose and glucose during exercise enhances exogenous galactose oxidation. 14 endurance-trained male and female participants (age, 27 (5) years; V̇O2peak, 58.1 (7.0) ml·kg-1·min-1) performed cycle ergometry for 150 min at 50% peak power on 4 occasions, in a randomized counterbalanced manner. During exercise they ingested beverages providing carbohydrates at rates of 0.4 g.min-1 galactose (GAL), 0.8 g.min-1 glucose (GLU) and on two occasions 0.8 g.min-1 total galactose-glucose (GAL+GLU; 1:1 ratio). Single-monosaccharide 13C-labelling (*) was used to calculate independent (GAL, GLU, GAL*+GLU, GAL+GLU*) and combined (GAL*+GLU*, COMBINE) exogenous-monosaccharide oxidation between during exercise. Plasma galactose concentrations with GAL+GLU (0.4 mmol.L; 95%CL 0.1, 0.6)...
Respective oxidation of 13C-labeled lactate and glucose ingested simultaneously during exercise
Journal of applied physiology (Bethesda, Md. : 1985), 1997
The purpose of this experiment was to measure, by using 13C labeling, the oxidation rate of exogenous lactate (25 g, as Na+, K+, Ca2+, and Mg2+ salts) and glucose (75 g) ingested simultaneously (in 1,000 ml of water) during prolonged exercise (120 min, 65 +/- 3% maximum oxygen uptake in 6 male subjects). The percentage of exogenous glucose and lactate oxidized were similar (48 +/-3 vs. 45 +/- 5%, respectively). However, because of the small amount of oral lactate that could be tolerated without gastrointestinal discomfort, the amount of exogenous lactate oxidized was much smaller than that of exogenous glucose (11.1 +/- 0.5 vs. 36.3 +/- 1.3 g, respectively) and contributed to only 2.6 +/- 0.4% of the energy yield (vs. 8.4 +/- 1.9% for exogenous glucose). The cumulative amount of exogenous glucose and lactate oxidized was similar to that observed when 100 g of [13C]glucose were ingested (47.3 +/- 1.8 vs. 50.9 +/- 1.2 g, respectively). When [13C]glucose was ingested, changes in the pl...
Physiological reports, 2017
This study compared the effects of coingesting glucose and fructose on exogenous and endogenous substrate oxidation during prolonged exercise at altitude and sea level, in men. Seven male British military personnel completed two bouts of cycling at the same relative workload (55% Wmax) for 120 min on acute exposure to altitude (3375 m) and at sea level (~113 m). In each trial, participants ingested 1.2 g·min(-1) of glucose (enriched with (13)C glucose) and 0.6 g·min(-1) of fructose (enriched with (13)C fructose) directly before and every 15 min during exercise. Indirect calorimetry and isotope ratio mass spectrometry were used to calculate fat oxidation, total and exogenous carbohydrate oxidation, plasma glucose oxidation, and endogenous glucose oxidation derived from liver and muscle glycogen. Total carbohydrate oxidation during the exercise period was lower at altitude (157.7 ± 56.3 g) than sea level (286.5 ± 56.2 g, P = 0.006, ES = 2.28), whereas fat oxidation was higher at altit...
European Journal of Applied Physiology
Purpose This study aimed to investigate whether carbohydrate ingestion during 3 h long endurance exercise in highly trained cyclists at a rate of 120 g h−1 in 0.8:1 ratio between fructose and glucose-based carbohydrates would result in higher exogenous and lower endogenous carbohydrate oxidation rates as compared to ingestion of 90 g h−1 in 1:2 ratio, which is the currently recommended approach for exercise of this duration. Methods Eleven male participants (V̇O2peak 62.6 ± 7 mL kg−1 min−1, gas exchange threshold (GET) 270 ± 17 W and Respiratory compensation point 328 ± 32 W) completed the study involving 4 experimental visits consisting of 3 h cycling commencing after an overnight fast at an intensity equivalent to 95% GET. During the trials they received carbohydrates at an average rate of 120 or 90 g h−1 in 0.8:1 or 1:2 fructose-maltodextrin ratio, respectively. Carbohydrates were naturally high or low in 13C stable isotopes enabling subsequent calculations of exogenous and endog...