Respiratory Exchange Ratio (RER)

# Respiratory Exchange Ratio (RER)

## Respiratory Exchange Ratio (RER)

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##### Presentation Transcript

1. . w The ratio between CO2 released (VCO2) and oxygen consumed (VO2) . . . w RER = VCO2/VO2 Respiratory Exchange Ratio (RER) • The RER value at rest is usually 0.78 to 0.80, indicating the body is primarily metabolizing fat; e.g., oxidation of palmitate: C16H32O2 + 23O2→ 16CO2 + 16H2O + 129 ATP Thus, RER = 16/23 = 0.70 Oxidation of glucose: C6H12O6 + 6O2 → 6CO2 + 6H2O + 38 ATP Thus, RER = 6/6 = 1.00 • during intense exercise the RER may be 1.00 or above, indicating the body is primarily metabolizing carbohydrate.

2. Respiratory Exchange Ratio (RER) • The RER value can be used to determine energy substrate used at rest and during exercise, with a value of 1.00 indicating CHO and 0.70 (0.71) indicating fat. % fat contribution = 100 x (1 − RQ)/0.29 e.g., if RER = 0.75, the % fat contribution to metabolism would be 86%

3. Energy % kcal RER kcal/L O2 Carbohydrates Fats 0.71 4.69 0.0 100.0 0.75 4.74 15.6 84.4 0.80 4.80 33.4 66.6 0.85 4.86 50.7 49.3 0.90 4.92 67.5 32.5 0.95 4.99 84.0 16.0 1.00 5.05 100.0 0.0 Caloric Equivalence of the Respiratory Exchange Ratio (RER) and % kcal From Carbohydrates and Fats