Training-induced alterations of glucose flux in men.
We examined the hypothesis that glucose flux was directly related to relative exercise intensity both before and after a 10-wk cycle ergometer training program in 19 healthy male subjects. Two pretraining trials [45 and 65% of peak O2 consumption (VO2peak)] and two posttraining trials (same absolute and relative intensities as 65% pretraining) were performed for 90 min of rest and 1 h of cycling exercise. After training, subjects increased VO2peak by 9.4 +/- 1.4%. Pretraining, the intensity effect on glucose kinetics was evident with rates of appearance (R(a); 5.84 +/- 0.23 vs. 4.73 +/- 0.19 mg x kg(-1) x min(-1)), disappearance (R(d); 5.78 +/- 0.19 vs. 4.73 +/- 0.19 mg x kg(-1) x min(-1) x min(-1)), oxidation (R(ox); 5.36 +/- 0.15 vs. 3.41 +/- 0.23 mg x kg(-1) x min(-1)), and metabolic clearance (7.03 +/- 0.56 vs. 5.20 +/- 0.28 ml x kg(-1) x min(-1)) of glucose being significantly greater (P < or = 0.05) in the 65% than the 45% VO2peak trial. When R(d) was expressed as a percentage of total energy expended per minute (R(dE)), there was no difference between the 45 and 65% intensities. Training did reduce R(a) (4.63 +/- 0.25), R(d) (4.65 +/- 0.24), R(ox) (3.77 +/- 0.43), and R(dE) (15.30 +/- 0.40 to 12.85 +/- 0.81) when subjects were tested at the same absolute workload (P < or = 0.05). However, when they were tested at the same relative workload, R(a), R(d), and R(dE) were not different, although R(ox) was lower posttraining (5.36 +/- 0.15 vs. 4.41 +/- 0.42, P < or = 0.05). These results show 1) glucose use is directly related to exercise intensity; 2) training decreases glucose flux for a given power output; 3) when expressed as relative exercise intensity, training does not affect the magnitude of blood glucose use during exercise; 4) training alters the pathways of glucose disposal.
Friedlander
A L
AL
Department of Human Biodynamics, University of California, Berkeley 94720, USA. annef@uclink3.berkeley.edu
Casazza
G A
GA
Horning
M A
MA
Huie
M J
MJ
Brooks
G A
GA
D000293:Adolescent; D000328:Adult; D001786:Blood Glucose / Q000378:metabolism; D001823:Body Composition; D002395:Catecholamines / Q000097:blood; D004734:Energy Metabolism / Q000502:physiology; D005080:Exercise Test; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D008297:Male; D008657:Metabolic Clearance Rate / Q000502:physiology; D010084:Oxidation-Reduction; D010807:Physical Endurance / Q000502:physiology; D010809:Physical Fitness; D011659:Pulmonary Gas Exchange / Q000502:physiology
D001786:Blood Glucose; D002395:Catecholamines; D005947:Glucose