Lactic acid is formed when an athlete exercises, if he or she is doing so at a level where more oxygen is being used than can be replenished to their system.

As this builds up, it gradually forces the body to slow down - it is the body's way of telling you that you can’t carry on as you are.

What lactic acid tolerance training will do for you is make your body more efficient at reprocessing the waste products of exercise, transporting oxygen to your blood and allowing you to run nearer to maximal speed for a longer period of time.

400m and 800m runners in particular will have a need to do this particular sort of training. Sessions that involve a lot of lactic acid being produced can be anything from 200m to 600m repetitions where the speed of the run is no more than about 10-15% slower than would be achieved for a race over the distance.

The recoveries between runs will vary considerably, but a good guide would be about two minutes for each 100m just run. At this stage the athlete should have recovered their breath from the previous run and their pulse rate will have dropped considerably, but they will still be fatigued from the previous exertion(s). If the blood lactate levels were measured at this point we would see that they were still elevated significantly.