In anaerobic respiration, lactic acid is a byproduct. Lactic acid can cause muscles to cramp.
Anaerobic respiration can not be sustained over a long period. Is this because the production of lactic acid cramps muscle and therefore slows the process of anaerobic respiration, or is there another reason?
We learned in the study of anaerobic respiration that 2 ATP are required to initiate anaerobic respiration and that a (maximum) of 4 ATP are produced. This is not very energy efficient. We know that the resultant net ATP produced will only be 2 ATP per molecule of glucose and that the resultant product ‘pyruvate’ - will be converted initially to pyruvic acid then to either alcohol in plants or lactic acid in animals - both toxic byproducts. Cells, however, will immediately lose these toxins and this will not be the cause of a halt to anaerobic respiration - in fact for some cells that only rely on anaerobic respiration such as prokaryotes, they will necessarily continue with respiration for the length of life.
In human or mammal cells, the reasons for cessation of anaerobic respiration are many - glycogen reserves beside each muscle cell deplete quickly, especially during the energy expensive anaerobic process, and unless oxygen (and glucose in blood) are provided to allow aerobic respiration to occur, the glucose supply is not great enough. Hence athletes ‘carbo loading’ to increase glycogen storage prior to endurance events. Just as importantly though, is the loss of electrolytes from athletes through excessive sweating - these electrolytes tell us a lot. The production of ammonia due to anaerobic exercise, inhibits neuron firing and service of essential signals to muscles. ADP accumulation means that free phospate ions can then inhibit calcium ion release that affects the contractile mechanisms of muscle fibrils. Potassium ions also accumulate - this lowers the osmotic and gradation potential across membranes (interestingly - a major cause of altitude sickness) making muscle cells less excitable ( or we could say - more fatigued) and the potassium inhibits calcium ion travel across the membrane causing major metabolic imbalances.
All very interesting - but also at the edge of the research world (definitely above L2 of NCEA!), but in a world where the cure for muscle fatigue is a hot topic and the answer is elusive.