title: High rates of exogenous carbohydrate oxidation from a mixture of glucose and fructose ingested during prolonged cycling exercise.
abstract: 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, exogenous CHO oxidation rates during the last 90 min of exercise were approximately 50% higher (P<0.05) in GLU+FRUC compared with GLU (1.49 (SE 0.08) and 0.99 (SE 0.06) g/min, respectively). The results demonstrate that when a mixture of glucose and fructose is ingested at high rates (2.4 g/min) during 150 min of cycling exercise, exogenous CHO oxidation rates reach peak values of approximately 1.75 g/min.
authors.affiliation: Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston B15 2TT, UK.
authors.forename: Roy L P G
authors.initials: RL
authors.lastname: Jentjens
authors.forename: Asker E
authors.initials: AE
authors.lastname: Jeukendrup
mesh_terms: D000328:Adult; D000704:Analysis of Variance; D001642:Bicycling; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000378:metabolism*; D005632:Fructose / Q000008:administration & dosage / Q000378:metabolism; D005947:Glucose / Q000008:administration & dosage / Q000378:metabolism; D006801:Humans; D007553:Isotope Labeling; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010807:Physical Endurance
chemical_list: D004040:Dietary Carbohydrates; D005632:Fructose; D005947:Glucose