Resumen de Fuel Selection during Prolonged Arm and Leg Exercise with 13C-Glucose Ingestion

Jonathan H. Tremblay, François Péronnet, Carole Lavoie, Denis Massicotte

• Purpose: To compare fuel selection during prolonged arm (AE) and leg exercise (LE) with water or glucose ingestion.

  Methods: Ten subjects (V[spacing dot above]O2max: 4.77 +/- 0.20 and 3.36 +/- 0.15 L[middle dot]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[middle dot]kg-1) or 13C-glucose (2 g[middle dot]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 (~8% vs ~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.