Substrate utilization during prolonged exercise with ingestion of (13)C-glucose in acute hypobaric hypoxia (4,300 m).
Energy substrate oxidation was measured using indirect respiratory calorimetry combined with tracer technique in five healthy young male subjects, during a 80-min exercise period on ergocycle with ingestion of 140 g of (13)C-labelled glucose, in normoxia and acute hypobaric hypoxia (445 mmHg or 4,300 m), at the same relative [77% V(.-)((O)(2)(max))] and absolute workload (161+/-8 W, corresponding to 77 and 54% V(.-)((O)(2)(max)) in hypoxia and normoxia). The oxidation rate of exogenous glucose was not significantly different in the three experimental situations: 21.4+/-2.9, 20.2+/-1.2 and 17.2+/-0.6 g over the last 40 min of exercise at approximately 77 and approximately 54% V(.-)((O)(2)(max)) in normoxia and in hypoxia, respectively, providing 12.5+/-1.5, 16.8+/-1.1 and 14.9+/-1.1% of the energy yield, although ingestion of glucose during exercise resulted in a higher plasma glucose concentration in hypoxia than normoxia. The contribution of carbohydrate (CHO) oxidation to the energy yield was significantly higher in hypoxia (92.0+/-2.1%) than in normoxia for both a given absolute (75.3+/-5.2%) and relative workload (78.1+/-1.8%). This greater reliance on CHO oxidation in hypoxia was entirely due to the significantly larger contribution of endogenous glucose oxidation to the energy yield: 75.9+/-1.7% versus 66.6+/-3.3 and 55.2+/-3.7% in normoxia at the same relative and absolute workload.
Péronnet
F
F
Département de kinésiologie, Université de Montréal, H3C 3J7, Montreal, QC, Canada.
Massicotte
D
D
Folch
N
N
Melin
B
B
Koulmann
N
N
Jimenez
C
C
Bourdon
L
L
Launay
J-C
JC
Savourey
G
G
D000328:Adult; D001273:Atmosphere Exposure Chambers; D001274:Atmospheric Pressure; D001786:Blood Glucose / Q000032:analysis; D002153:Calorimetry, Indirect; D002247:Carbon Isotopes; D015444:Exercise / Q000502:physiology*; D005080:Exercise Test; D005947:Glucose / Q000378:metabolism*; D006801:Humans; D006985:Hyperventilation / Q000503:physiopathology; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption / Q000502:physiology; D011659:Pulmonary Gas Exchange / Q000502:physiology
D001786:Blood Glucose; D002247:Carbon Isotopes; D005947:Glucose