Lactic Acid is the by-product of anaerobic metabolism.
When lactate is produced faster than the ability of the muscles or tissues to remove it, it is then dumped into the blood, where the concentration can then be determined.
Lactic acid levels are quite low during slower-paced exercises and as the intensity increases, so does the concentration of lactic acid in the blood.
During a lactate threshold test, an athlete runs on a treadmill while the speed is gradually increased.
The athlete runs for about 6 minutes and then gets e.g. 30 seconds for recovery between each stage.
During the break, heart rate will continue to be monitored and a drop of blood will be taken from the athlete's earlobe (or finger).
Between each stage, a blood sample will be taken and the concentration of lactic acid calculated.
This test is to determine when an athlete reaches their lactate threshold, which means the lactate removal fails to keep up with the rate of lactate production.
Anaerobic threshold is reached with a result of 4mmol per liter blood.
Based on the different heart rate levels and the lactic acid results at a certain stage or speed determined by the test, one can base one's training on one's pulse.
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VICSYSTEM suggests instead of running several stages between 2½ to 3 minutes long, run longer stages starting from 6 minutes. After every stage, there is a designated 30-second break to take the blood samples. During shorter stages, one's pulse and lactic acid levels are still in the process of rising and a steady-state not yet reached.
In VICSYSTEM, lactate threshold tests are voluntary because runners who run on a regular basis and keep improving, will have to conduct the tests frequently.