Endurance training decreases plasma glucose turnover and oxidation during moderate-intensity exercise in men.
To assess the effects of endurance training on plasma glucose kinetics during moderate-intensity exercise in men, seven men were studied before and after 12 wk of strenuous exercise training (3 days/wk running, 3 days/wk cycling). After priming of the glucose and bicarbonate pools, [U-13C] glucose was infused continuously during 2 h of cycle ergometer exercise at 60% of pretraining peak O2 uptake (VO2) to determine glucose turnover and oxidation. Training increased cycle ergometer peak VO2 by 23% and decreased the respiratory exchange ratio during the final 30 min of exercise from 0.89 +/- 0.01 to 0.85 +/- 0.01 (SE) (P less than 0.001). Plasma glucose turnover during exercise decreased from 44.6 +/- 3.5 mumol.kg fat-free mass (FFM)-1.min-1 before training to 31.5 +/- 4.3 after training (P less than 0.001), whereas plasma glucose clearance (i.e., rate of disappearance/plasma glucose concentration) fell from 9.5 +/- 0.6 to 6.4 +/- 0.8 ml.kg FFM-1.min-1 (P less than 0.001). Oxidation of plasma-derived glucose, which accounted for approximately 90% of plasma glucose disappearance in both the untrained and trained states, decreased from 41.1 +/- 3.4 mumol.kg FFM-1.min-1 before training to 27.7 +/- 4.8 after training (P less than 0.001). This decrease could account for roughly one-half of the total reduction in the amount of carbohydrate utilized during the final 30 min of exercise in the trained compared with the untrained state.
Coggan
A R
AR
Department of Medicine, Washington University School of Medicine, St. Louis, Missouri 63110.
Kohrt
W M
WM
Spina
R J
RJ
Bier
D M
DM
Holloszy
J O
JO
D000328:Adult; D001786:Blood Glucose / Q000378:metabolism*; D050260:Carbohydrate Metabolism; D002245:Carbon Dioxide; D004734:Energy Metabolism; D006801:Humans; D007773:Lactates / Q000097:blood; D019344:Lactic Acid; D050356:Lipid Metabolism; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D010806:Physical Education and Training; D010807:Physical Endurance / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology
D001786:Blood Glucose; D007773:Lactates; D002245:Carbon Dioxide; D019344:Lactic Acid