Understanding VO2 Max: Measuring Fitness Part IV
VO2 Max may or may not mean anything to you, depending on your exercise and fitness background. If you're a person who is just starting an exercise program or has been exercising casually, the term might be new. If you’re a current or retired athlete, you probably already know VO2 Max is an important number that reflects how efficient your cardiovascular system is.
VO2 Max Background
The most reliable way to obtain your VO2 Max results is by having a Max Test done. Commonly conducted in an academic lab by an Exercise Physiologist like myself, the Max VO2 test measures the volume and content of each breath while exercising at maximum intensity. The test defines the upper limits of your cardiovascular function, measuring variables such as your ventilation, maximum breathing capacity, oxygen uptake and carbon dioxide produced.
Intensity and Energy Source
The coolest part about the VO2 Max Test is that it can determine which macronutrient substrate (fat, protein, carbohydrate) your body is using for fuel during physical activity based on intensity. Carbohydrates, fat and protein are all necessary in energy metabolism. The macronutrient used for energy at a given time, depends on the intensity of the exercise and changes from person to person.
The VO2 Max test allows us to estimate which particular fuel (carbohydrate, fat or protein) is being oxidised by calculating the Respiratory Exchange Ratio (RER). RER is the ratio of carbon dioxide produced to oxygen consumed, and is known as the Respiratory Quotient. An RER of .7 indicates that fat is the main source of energy, and an RER of .85 indicates that the protein substrate is being used, and finally, an RER of 1.0 indicates that carbohydrates are the main source of energy.
Understanding your limits and main sources of energy to fuel those limits can be critical for performance. If you have any questions about where your limit lies and what your body uses for fuel it, reach out to me. I’d love to help.
