Lactate Threshold - How to Measure

Origin of the term "threshold"

The term threshold first arose in exercise metabolism with an article by Karl Wasserman in 1964. Wasserman used VO2 measurements to show a change in the oxygen and CO2 curves that seemed to correspond with an increase in lactate in the blood. At a point on the curve, CO2 increased more than he expected. The subjects were producing more lactate than the muscles could consume; the buffering of this lactate was thought to cause the observed increase in CO2. Wasserman called this the anaerobic threshold because it was thought that the body was suddenly transitioning to anaerobic metabolism.

Some other researchers later pointed out that while excess lactate was being produced and it appeared in the blood stream, the body was in a steady state and no threshold that the body was passing through. Oxygen was still being used in ever greater amounts.  So while the lactate in the blood indicated a somewhat greater involvement of the anaerobic system, and CO2 increased confirming this, aerobic metabolism was still the main source of energy, was still increasing and was not near maximum. Thus, there was no change to anaerobic metabolism at this point and no reason to use the term "threshold."

But the term was born and has been with exercise physiology and athletic training ever since. Here are two quotes from the original Wasserman study:

• "The onset of anaerobic metabolism during exercise can thus be detected in three ways: (1) as an increase in the lactate concentration in blood, (2) as a decrease in arterial blood bicarbonate and pH and (3) as an increase in the respiratory gas exchange ratio (R)." 
  
  
• "Thus, it is possible for the examiner to detect the threshold of anaerobic metabolism during the work test"

He then went on and used the specific term, "anaerobic threshold" because he believed that this was where the anaerobic system took over.   He was wrong about this and that is what science is about. Discoveries like Wasserman's are what move the ball along but unfortunately his idea of a major abrupt change in anaerobic metabolism was wrong. This misconception persists till today with many people despite the fact that anaerobic metabolism occurs before this so-called threshold point, and aerobic metabolism continues after it.  And ironically the place on the gas curve he pointed out is not necessarily an important point for training for endurance sports.