VO2max testing is designed to fully tax the aerobic system. A person is put on a treadmill or bike trainer a mask is then fitted over the face to monitor oxygen and carbon dioxide. The test is designed to be run until failure or at least until oxygen consumption remains steady despite an increasing in workload.

The interesting parts about the VO2max test are less about the VO2max value itself, but how it can be used with other data gathered during the test to tell a story about metabolic efficiency. One can discern the ideal heart rate, effort level and amount of calories to carry when competing in an endurance sport.

1. Respiratory Quotient (RQ) – This is the CO2 exhaled over O2 consumed. Based on RQ levels one can determine levels of fat versus glycogen being burned. A RQ of .7 is 100% fat burning. An RQ score of 1 is burning 100% glycogen.
2. The Crossover Point – When an athlete crosses over from burning primarily fat to primarily carbohydrates. I’m particularly interested in finding my own heart rate value and % of VO2 max associated with this. Most athletes crossover at 35-65% of their VO2 max.
3. Peak Fat Oxidation – Low carb athletes can burn over 1g of fat per minute or 540 calories per hour. Getting a more specific value can be beneficial to determine how much fuel to carry. The current high end of fat burning is 1.8g of fat per hour which is came out of the FASTER study.

Sources:

• Peter Attia – How a low carb diet affected my athletic performance

• Ultrarunning Magazine – The Emerging Science on Fat Adaptation