New insights in the field of sports physiology, and especially about the role and function of lactic acid, clearly show that these need to be reviewed. Lactic acid is not the waste product with a number of harmful side-effects for which it was held for many years. On the contrary. Read the three chapters that were published about it on this blog about. In short, it means that the formed lactic acid is recycled to pyruvate which is then aerobically decomposed releasing energy. SO LACTIC ACID IS AN IMPORTANT SOURCE OF ENERGY.

The ability to recycle lactic acid is for the one athlete larger than for the other, and moreover, the ability to recycling increased by aerobic training. From my sport practice, I remember a few well-trained cyclists who never came out over a lactic acid value of 5 mmol / L during a maximal exercise test on a cycle ergometer, while achieving a maximal performance during the test. The explanation is the well-developed recycling mechanism. Some well trained athletes have an anaerobic threshold lower than 4 mmol/l. These athletes are well trained and they have a very high percentage of type I fibers, the aerobic fibers. LACTIC ACID IS LARGELY RECYCLED TO PYRUVATE.

During anaerobic effort lactic acid and Hydrogen is being formed in the muscle cells. Hydrogen is responsible for the acidification, and also partly to the feeling of fatigue and not lactic acid, like was assumed for many years. The side effects caused by acidification are not caused by lactic acid but by Hydrogen. With increasing acidification the lactate levels increases proportionally. Therefore, it seems there is not so much change, and the lactate values can continue to be used, to objectify to the intensity of the effort and to continue to express training commands in the height of the heart rate or in Wattage. LACTIC ACID IS NOT RESPONSIBLE FOR THE ACIDIFICATION.

For now it seems it is still able to use lactate tests to optimize training advice. But the future will tell whether this is justified. Point is that well-trained endurance athletes have a much better developed recycling mechanism by which their lactate values make a correct interpretation difficult. It will take years before the myths about lactate disappeared from the scene. Now there are still many coaches, trainers, sports physiologists and academics who maintain all the misinterpretations about lactate. Keep that in your mind when you hear all that stories about lactate.


When the intensity of the effort continues to increase at some point the oxygen system cannot handle it anymore. The demand for energy is then supplemented by the anaerobic combustion of carbohydrates. In that situation the lactate level increases in the working muscles. So does the amount of hydrogen in the muscles. And it is hydrogen, and not lactate or lactic acid, which causes the acidification. The energy supply that goes along with high acidification is a makeshift.

Glucose + ADP → ATP + lactic acid

Increase in the intensity of the effort goes at some point accompanied by an increase in production of lactic acid. The intensity of the effort is at that level such high that anaerobic energy supply has been playing an important role.

A characteristic of an increase in acidification of the muscles is pain in the legs for the cyclist or the runner or pain in the arms for a rower. Through this pain and the concomitant sense of powerlessness effort can no longer be sustained at the same level.

If the cyclist or runner cannot follow the pace of the race the cause is often a strong acidification in the muscles. The athlete who is able to postpone the moment of acidification the longest will generally be the best and win the race. Energy supply that goes along with high lactic acid levels is a stopgap. Acidification, which the athlete can feel good, can have important negative consequences.

By the anaerobic energy supply carbohydrates will only be used as fuel. That can be seen as a kind of emergency system that will enter into force when crossing for every individual a different level of intensity. It leads, depending on the degree of overshoot and the athlete’s physical condition, within a time frame of several tens of seconds to several tens of minutes, until forced to stop of the effort or drastically reducing the intensity of the effort. The cause why an athlete is not able to maintain the effort at this level is the accumulation of lactic acid *, and the associated muscle fatigue.

* It is not the accumulation of lactic acid which causes acidification and fatigue arises. The true cause of acidification is the accumulation of hydrogen (H+) that causes acidosis. Lactic acid has no negative effects on an intensive sporting cyclist. Training associated with acidification may actually be detrimental.

Lactate level at the beginning of an effort


  • For short-term high-intensive activities like the 100-, 200-, 400- and 800-meter runs and other very intensive efforts lasting two to three minutes. During a 1500-meter run is the energy supply 50% aerobic and 50% anaerobic.
  • At the beginning of an effort, regardless of the intensity, the energy supply is always anaerobic lactic. It takes always several minutes for the oxygen transport system is started up and fully functioning. Respiration, heart rate and the transport of oxygen through the circulatory system need time to get going. During that time, at the beginning of the effort, the lactic acid system delivers the necessary energy.
  • During increases in speed  during endurance exercise, which are too much for the aerobic energy supply, such as sprints, climbs and breakaways.
  • During increases in speed in   the final sprint, after a prolonged effort, for example, at the finish of a marathon or during a final sprint of a cycling race.
  • In efforts above the anaerobic threshold, lactic acid system supplies a portion of the energy. The proportion of the lactic acid to energy supply system increases as more of the anaerobic threshold is exceeded or, in other words, if the intensity of exercise continues to increase.
  • Anaerobic efforts just above the anaerobic threshold, by trained individuals, because of the excessive acidity, but 40 to 60 minutes, be sustained. Anaerobic efforts may well above the anaerobic threshold because of the hefty acidification only briefly, at most a minute or two, be sustained.
The lactate levels at the end of various races; from 100-meters sprint to the final sprint in the 10,000 meters. The proportion of the anaerobic energy supply is greatest at the 400-meter race.


In general, with a rest recovery – that is to say, no physical activity during the recovery period – of 25 minutes half of the accumulated lactic acid will be removed from the body. After 1 hour and 15 minutes, 95 percent of the lactic acid, arise after maximum load, is removed during rest recovery. It has been shown that the removal of lactic acid from blood and muscle is considerably faster to be carried out during the recovery in light physical work instead of total resting. This is the so-called active recovery active in nature and is in fact the cool-down activity that most athletes already applying for years. By active recovery, through or out jogging, the lactic acid is broken down rapidly. During the restoration the best activity is a light continuous workout rather than a light interval workouts.

During active recovery the removal of lactic acid from muscle and blood is significantly faster.