Fuel selection during prolonged arm and leg exercise with 13C-glucose ingestion.
OBJECTIVE
To compare fuel selection during prolonged arm (AE) and leg exercise (LE) with water or glucose ingestion.


METHODS
Ten subjects (VO2max: 4.77 +/- 0.20 and 3.36 +/- 0.15 L x min(-1) for LE and AE, respectively) completed 120 min of LE and AE at 50% of the mode-specific maximal power output (353 +/- 18 and 160 +/- 9 W, respectively) with ingestion of water (20 mL x kg(-1)) or 13C-glucose (2 g x kg(-1)). Substrate oxidation was measured using indirect respiratory calorimetry corrected for urea excretion and 13CO2 production at the mouth.


RESULTS
The contribution of protein oxidation to the energy yield (%En) was higher during AE than LE (approximately 8% vs approximately 4%) because of the lower energy expenditure and was not significantly modified with glucose ingestion. With water ingestion, the %En from CHO oxidation was not significantly different during LE and AE (64 +/- 2% and 66 +/- 2%, respectively). Glucose ingestion significantly increased the %En from total CHO oxidation during AE (78 +/- 3%) but not during LE (71 +/- 2%). Exogenous glucose oxidation was not significantly different in AE and LE (56 +/- 4 and 65 +/- 3 g, respectively), but the %En from exogenous glucose was higher during AE than LE (30 +/- 1% and 24 +/- 1%) because of the lower energy expenditure. When glucose was ingested, the %En from endogenous CHO oxidation was significantly reduced during both AE (66 +/- 2% to 48 +/- 3%) and LE (64 +/- 2% to 47 +/- 3%) and was not significantly different in the two modes of exercise.


CONCLUSIONS
The difference in fuel selection between AE and LE when water was ingested was modest with a slightly higher reliance on CHO oxidation during AE. The amount of exogenous glucose oxidized was lower but its %En was higher during AE because of the lower energy expenditure.
Tremblay
Jonathan H
JH
Department of Kinesiology, University of Montreal, Montreal, Canada. jonathan.tremblay@umontreal.ca
Péronnet
François
F
Lavoie
Carole
C
Massicotte
Denis
D
D000328:Adult; D001132:Arm / Q000502:physiology*; D002153:Calorimetry, Indirect; D004305:Dose-Response Relationship, Drug; D005518:Food Preferences; D005947:Glucose / Q000008:administration & dosage*; D005948:Glucose Dehydrogenases / Q000378:metabolism; D006801:Humans; D007866:Leg / Q000502:physiology*; D008297:Male; D010084:Oxidation-Reduction; D010101:Oxygen Consumption; D005082:Physical Exertion / Q000502:physiology*; D011506:Proteins / Q000378:metabolism; D011792:Quebec; D014867:Water / Q000008:administration & dosage; D055815:Young Adult
D011506:Proteins; D014867:Water; D005948:Glucose Dehydrogenases; D005947:Glucose