What Is a VO2 Max Test?

A VO2 Max test involves a graded exercise test on a treadmill or on your bike. The test begins at a very light intensity and gets slightly harder each minute until maximum exertion.  The subject wears a mask and we measure the volume of air expired along with the percentages of oxygen and carbon dioxide in the expired air.  From this data, we determine the following:

Aerobic Threshold:

Aerobic threshold is the optimal intensity (wattage, running speed and/or heart-rate) for developing endurance.  At aerobic threshold intensity, the body is recruiting almost all of the slow-twitch muscle fibers, but not yet recruiting any of the fast twitch fibers.  Most athletes, without the benefit of physiological testing, overestimate this intensity.  Using optimal intensity for basic endurance training maximizes fat burning and minimizes recovery time and injury risk.  Most athletes perform basic endurance workouts at an intensity that is too high.  Conducting basic endurance workouts at optimal intensity is much more efficient, enabling increased training volume as well as greater frequency and better quality speed workouts.  Aerobic threshold is the intensity of the stage highlighted in yellow highest on the page of the sample test.

Lactate Threshold:

Known as the red-line to endurance athletes, this threshold is the highest intensity at which the body can recycle lactic acid as quickly as it is produced. Just below lactate threshold (LT), an athlete is working hard and acid levels are moderately high, but it does not accumulate. Speeding up just a little will cause lactic acid accumulation. Knowing this precise threshold enables an athlete to work out most efficiently.

Lactate threshold is the intensity of the stage highlighted in yellow lower on the page of the sample test.

Lactic acid is a byproduct of exercise which makes the muscles burn and may contribute to fatigue.  Athletes during exercise, even at low intensity, are always producing lactic acid.  Their muscles are also constantly burning lactic acid and using it as a fuel.  At low intensity the muscles easily recycle as much acid as is produced.  The higher the intensity is, the more acid is produced by the muscles.  At lactate threshold intensity, the muscle is able to recycle the acid as quickly as it is produced.  If the athlete speeds up just slightly, the muscles produce more acid than it can recycle and acid accumulates, causing fatigue and damaging the muscles.

VO2 Max:

VO2 Max is the volume of oxygen the body uses during one minute of maximal exercise.  This data tells your potential for endurance athletics. While aerobic and lactate thresholds are the best predictors of current endurance performance, VO2 Max is one indicator of an athlete's potential.  VO2 max is the number highlighted in yellow near the bottom of the page on the sample test.

VO2 Max Testing on Bicycle

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