Lactic Acid Removal

As lactic acid has detrimental effects on exercise performance, it is important to consider the factors which effect its removal from the blood stream. The rate at which lactic acid leaves the muscle and enters the blood stream is determined by the rate at which blood flows through the tissues. Lactic acid may then be taken up by the heart or other skeletal muscles and converted back into pyruvic acid and further metabolized in order to generate energy in the form of ATP. Some of the lactic acid not consumed in this manner is, in the period immediately after exercise, converted back into glycogen by the liver.

At the completion of an exercise session, or between repetitions during interval training, one has the choice of employing and active or a passive recovery. An active recovery involves exercising at a low intensity whilst the passive mode of recovery involves total rest.

If lactic acid accumulates during exercise there is a distinct advantage to employing an active recovery because the blood flow, and therefore the lactic acid dispersal from muscle, is greater than that during a passive recovery. Furthermore, the rate at which lactic acid is utilized as an energy source by the heart and skeletal muscle is greater during low intensity exercise than at rest.

The optimal exercise intensity for active recovery depends on each subject's fitness level, but for most individuals it occurs at heart rates of approximately 15-30 beats per minute below that of the anaerobic threshold.

Even with an active recovery it may take as long as 30 minutes for 95% of the accumulated lactic acid to be removed after extremely intense anaerobic exercise. However, lactic acid concentrations may remain elevated above resting levels for 60 minutes or more if a passive recovery is employed.

It is obviously inappropriate to wait for lactic acid to completely disperse before completing another repetition during an interval training session. However, lactic acid levels do drop quite significantly in the first few minutes of recovery and it may take as little as five minutes of active recovery for 50% of the accumulated lactic acid to be removed from the blood stream. As a result a significant recovery occurs when five to 10 minutes are taken between intervals.