High oxidation rates from combined carbohydrates ingested during exercise.
Studies that have investigated oxidation of a single carbohydrate (CHO) during exercise have reported oxidation rates of up to 1 g x min(-1). Recent studies from our laboratory have shown that a mixture of glucose and sucrose or glucose and fructose ingested at a high rate (1.8 g x min(-1)) leads to peak oxidation rates of approximately 1.3 g x min(-1) and results in approximately 20 to 55% higher exogenous CHO oxidation rates compared with the ingestion of an isocaloric amount of glucose.


OBJECTIVE
The purpose of the present study was to examine whether a mixture of glucose, sucrose and fructose ingested at a high rate would result in even higher exogenous CHO oxidation rates (>1.3 g x min(-1)).


METHODS
Eight trained male cyclists (VO2max: 64 +/- 1 mL x kg(-1) BM x min(-1)) cycled on three different occasions for 150 min at 62 +/- 1% VO2max and consumed either water (WAT) or a CHO solution providing 2.4 g x min(-1) of glucose (GLU) or 1.2 g x min(-1) of glucose + 0.6 g x min(-1) of fructose + 0.6 g x min(-1) of sucrose (MIX).


RESULTS
High peak exogenous CHO oxidation rates were found in the MIX trial (1.70 +/- 0.07 g x min(-1)), which were approximately 44% higher (P < 0.01) compared with the GLU trial (1.18 +/- 0.04 g x min(-1)). Endogenous CHO oxidation was lower (P < 0.05) in MIX compared with GLU (0.76 +/- 0.12 and 1.05 +/- 0.06 g x min(-1), respectively).


CONCLUSIONS
When glucose, fructose and sucrose are ingested simultaneously at high rates (2.4 g x min(-1)) during cycling exercise, exogenous CHO oxidation rates can reach peak values of approximately 1.7 g x min(-1) and estimated endogenous CHO oxidation is reduced compared with the ingestion of an isocaloric amount of glucose.
Jentjens
Roy L P G
RL
Human Performance Laboratory, School of Sport and Exercise Sciences, University of Birmingham, Edgbaston, United Kingdom.
Achten
Juul
J
Jeukendrup
Asker E
AE
D000328:Adult; D001642:Bicycling / Q000502:physiology*; D004040:Dietary Carbohydrates / Q000008:administration & dosage* / Q000097:blood / Q000378:metabolism; D041981:Gastrointestinal Tract / Q000503:physiopathology; D006801:Humans; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D011795:Surveys and Questionnaires; D006113:United Kingdom
D004040:Dietary Carbohydrates