Lactate History

Discovered in Sour Milk

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. He showed this by comparing the RER or respiratory exchange ratio (see definition from Wikipedia below) and lactate in the blood with oxygen consumption.

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. Place Cursor here for a chart which shows the results of their testing. Notice that the RER and lactate levels seem to increase at the same level of VO2 consumption.

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. Many people still have this misconception 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. But because it is a specific point there was and still is a belief that it represented something important for training.

But there was already research available that described the phenomenon that Wasserman observed. However, it was in German and the main researcher was Wildor Hollmann of the German Sports University in Cologne. In 1959 Hollmann presented a paper on what he called "point of optimal ventilatory efficiency" at the Third Pan American Congress of Sports Medicine. The presentation was based on the author's hypothesis that the ventilatory and lactic acid threshold exists and how to determine each. The work on this had started in the late 1940's and developed some novel ways to measure VO2 consumption and lactate levels in the blood. At first they tried to measure pyruvate but there were such small amounts of it that it did not correlate with physical activity. Then they decided to measure lactate instead and they realized that there was much higher levels of lactate in the blood than pyruvate whihc is why we now have the lactate threshold and not the pyruvate threshold. Place cursor here to see some of their results

They eventually determined that arterial blood lactate was the best place to measure lactate but because it was dangerous to use arterial blood, they experimented with other sources. Eventually they recommended that blood lactate be measured in the ear lobe as this correlated highly with arterial lactate. Lactate in the blood from the finger tip also highly correlated with arterial lactate. Venous lactate was not considered a good source for lactate because much of the lactate was being removed from resting muscles.