Respiratory Exchange Ratio (RER)

The Respiratory Exchange Ratio (RER) is a measure used to assess how the body produces energy during exercise. It compares the amount of carbon dioxide (CO2) produced to the amount of oxygen (O2) consumed. An RER close to 0.7 indicates fat is mainly being used for energy, while an RER near 1.0 suggests carbohydrates are the primary fuel. This ratio helps determine which energy sources are being utilized, providing insights into metabolic processes and fitness levels during different levels of physical activity.