# What happens to RER during exercise?

## What happens to RER during exercise?

As the intensity of the exercise increases and carbohydrates become the dominant or primary fuel, the respiratory quotient and the RER increase to between 0.9 and 1.0. Because the respiratory quotient reflects tissue substrate use, it cannot exceed 1.0.

## What is the RER at max exercise?

Background. A maximal exercise respiratory exchange ratio (RERmax) ≥1.10 is commonly used as a criterion to determine if a “true” maximal oxygen uptake (VO2max) has been attained during maximal-effort exercise testing.

What is RER in exercise physiology?

Respiratory Exchange Ratio (RER) is the ratio between the volume of CO2 being produced by the body and the amount of O2 being consumed. This value of this ratio gives us an indication as to whether the body is operating aerobically or anaerobically.

### What does an RER above 1.0 indicate during a maximal exercise test?

This can be used as an indicator that the participants are nearing exhaustion and the limits of their cardio-respiratory system. An RER greater than or equal to 1.0 is often used as a secondary endpoint criterion of a VO2 max test.

### What causes an RER to exceed 1.0 during exercise?

Why does RER exceed ‘1’? This is due to the non-metabolic buffering of CO2 by bicarbonate as exercise intensity increases.

Why does RER increase during recovery?

The closer RER is to 0.70, the more fat is being oxidized, and the closer RER is to 1.00, the more carbohydrate is being oxidized. Under non-steady state conditions, such as during recovery from severe exercise or during hyperventilation, RER can exceed 1.00 due to increased CO2 being expired.

#### What does an RER of 0.85 mean?

An RER of 0.85 means that you are burning approximately 50 percent fat and 50 percent carbohydrate. As exercise intensity increases, your body must rely more and more on carbohydrates as a fuel source. An RER over 1.00 means you are burning primarily carbohydrates. LT typically corresponds with RER of 1.0.

#### How is RER used?

RER is calculated by dividing the volume of CO2 produced by the volume of O2 consumed. This is done by indirect calorimetry at rest or during exercise, using a spirometer (or another device to measure airflow or breath volume), and oxygen and carbon dioxide analyzers.

What does an RER above 1.1 mean?

The RER for protein is approx. 0.8 but as it plays a very small part in energy metabolism. A value between 0.7 and 1.0 indicates a mixture of fat and carbohydrate as the energy source. A value greater than 1.0 indicates anaerobic respiration due to more CO 2 being produced than O 2 consumed.

## What happens when RER goes above 1?

If R is near 1.0, then the body is using mostly carbohydrates for energy production. If R is above 1.0, then carbon dioxide is being produced by other means, usually from the buffering of lactic acid. This indicates that the person is working very hard, or that they are hyperventilating.

## What does an RER of 1.0 mean when achieved during a GXT?

RER at rest ranges from 0.75 to 0.85. At high levels of exercise (maximal exercise), CO2 production exceeds Oxygen Uptake, and an RER will exceed 1.0 to 1.2 that is often used to indicate that the subject is giving a maximal effort.

What does a lower RER mean?

The lower RER values mean that during submaximal exercise, trained subjects oxidized a greater proportion of lipids at higher workload than untrained subjects (Messonnier et al. The lower blood lactate concentrations means, that the trained subjects had a more active lipid oxidative metabolism.