Lactic System


 * Source of Fuel-  The other system that does not require the presence of oxygen to resynthesise ATP in muscles is the lactic acid system, which is also known as anaerobic glycolysis. Following the initial 10 -12 seconds of maximal exercise, PC stores are exhausted and ATP still needs to be produced to provide energy. The body needs to find an alternate fuel and the lactic acid system becomes the dominant supplier of ATP. This system involves the partial breakdown of glucose to form lactic acid in a number of chemical reactions know as glycolysis. The glucose for this process comes from either glucose stored in the blood or from the breakdown of glycogen in the liver or muscle.
 * Efficiency of ATP production- The production of energy during this process is very efficient as there is a relatively quick supply of ATP; however it requires large amounts of glucose. Unfortunately, however, this process can yield only 5 per cent of the number of ATPs that are produced by the aerobic system, yet more than the ATP/PC system.
 * Duration of the system- The lactic acid system is an important energy system because it provides a very quick supply of ATP for intense, short bursts of activity (usually 30-60 seconds, but may last up to 3 minutes). The duration of the system depends upon the intensity of the activity, therefore the less intense the activity, the longer it will last.
 * Cause of Fatigue- Fatigue and exhaustion occurs when lactic acid accumulates in the muscle cells. This will usually cause the athlete to decrease the intensity of the activity, or to stop altogether. The speed of lactic acid production depends again on the exercise intensity. Very high levels of lactic acid prevent muscles fibres from contracting and hence a deterioration in performance. There are also suggestions that the accumulation of hydrogen ions, which brings about a decrease in pH and increases acidosis (an increase in the acidity of the blood), causes fatigue.
 * By products- Pyruvic acid/lactic acid is the main by-product of the lactic acid system.