Effect of carbohydrate ingestion on glucose kinetics during exercise in the heat
Journal of applied physiology
Angus, Damien J., Mark A. Febbraio, David Lasini, and Mark Hargreaves. Effect of carbohydrate ingestion on glucose kinetics during exercise in the heat. J Appl Physiol 90: 601-605, 2001.-Six endurance-trained men [peak oxygen uptake (V O 2 ) ϭ 4.58 Ϯ 0.50 (SE) l/min] completed 60 min of exercise at a workload requiring 68 Ϯ 2% peak V O 2 in an environmental chamber maintained at 35°C (Ͻ50% relative humidity) on two occasions, separated by at least 1 wk. Subjects ingested either a 6% glucose
... er a 6% glucose solution containing 1 Ci [3-3 H]glucose/g glucose (CHO trial) or a sweet placebo (Con trial) during the trials. Rates of hepatic glucose production [HGP ϭ glucose rate of appearance (R a ) in Con trial] and glucose disappearance (R d ), were measured using a primed, continuous infusion of [6,6-2 H]glucose, corrected for gut-derived glucose (gut R a ) in the CHO trial. No differences in heart rate, V O 2 , respiratory exchange ratio, or rectal temperature were observed between trials. Plasma glucose concentrations were similar at rest but increased (P Ͻ 0.05) to a greater extent in the CHO trial compared with the Con trial. This was due to the absorption of ingested glucose in the CHO trial, because gut R a after 30 and 50 min (16 Ϯ 5 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 ) was higher (P Ͻ 0.05) compared with rest, whereas HGP during exercise was not different between trials. Glucose R d was higher (P Ͻ 0.05) in the CHO trial after 30 and 50 min (48.0 Ϯ 6.3 vs 34.6 Ϯ 3.8 mol ⅐ kg Ϫ1 ⅐ min Ϫ1 , CHO vs. Con, respectively). These results indicate that ingestion of carbohydrate, at a rate of ϳ1.0 g/min, increases glucose R d but does not blunt the rise in HGP during exercise in the heat.