Blood Lactate

Blood lactate is the form that lactic acid takes in our blood stream and lactic acid is a by-product of anaerobic metabolism.  Anaerobic metabolism is a chemical process used to produce energy within our bodies and is most often used during sprinting, weight lifting and any other activities of high intensity and short duration.  Most of us are very familiar with the burning sensation we feel in our muscles during these types of exercises.  This burning sensation is due to an increase in the acidity of the muscular environment as a result of high rates of energy production.  Blood lactate is a good indicator of the rate of energy production from the anaerobic energy system and it can be used to monitor intensity and adaptation to exercise. 

At low levels of exercise intensity, blood lactate is low but as exercise intensity increases, lactate increases exponentially.  The point where lactate rapidly increases is termed the lactate threshold and is often used by elite athletes to monitor their training.  In the figure above, you can see that an athlete improved his conditioning from August of 2000 (blue line) to May of 2002 (pink line).  At each heart rate the athlete's blood lactate was lower in 2002.  This indicates that the muscles are operating more efficiently and are able to meet the demands of exercise more readily.