Lactic Acid Build-Up
Fast glycolysis arises during phases of reduced oxygen obtainability in the muscle cells and results in the development of the end-product lactate, which can be changed into lactic acid. Muscular weakness experienced during exercise has been connected with high muscle tissue quantities of lactic acid, but the fatigue is more likely an outcome of reduced tissue acidity from many sources of acid, as well as the intermediates of glycolysis. In general, there is a low concentration of lactate in blood and muscle.
The described normal range of lactate concentration in blood is between 0.5 to 2.2 millimoles per litre at rest. Lactate fabrication escalates with increasing exercise intensity and seems to depend on muscle fibre type.
The larger rate of lactate fabrication by type II muscle fibres may mirror motion of glycolytic enzymes that is higher than that of type I muscle fibres. It has been stated that blood lactate concentrations customarily return to pre-exercise quantities within an hour after physical activity. Light activity during the post-exercise phase has been demonstrated to increase lactate clearance speeds, and trained individuals (both anaerobic and aerobic) have faster lactate clearance rates than inexperienced individuals.
Peak blood lactate concentrations ensue roughly five minutes after the termination of exercise, a delay often attributed to the time necessary to shuttle lactate from the tissue to the blood. The exercise intensity or comparative intensity at which blood lactate initiates a sudden increase above the baseline concentration has been labelled the lactate threshold (LT). The LT signifies an increasing dependence on anaerobic mechanisms. The LT characteristically begins at 50% to 60% of maximal oxygen uptake in inexperienced individuals and at 70% to 80% in trained people. A second escalation in the rate of lactate build-up has been noted at higher comparative intensities of exercise. This second point, called the onset of blood lactate accumulation (OBLA), usually occurs when the concentration of blood lactate is near 4 millimoles per litre. It has been proposed that training at intensities near or directly above the LT or OBLA alters the LT and OBLA so that lactate accumulation transpires at a higher exercise intensity.
Kreisberg, R.A. 1980. Lactate homeostasis and lactic acidosis. Annals of Internal Medicine 92 (2): 227-237.
Mazzeo, R.S., G.A. Brooks, D.A. Schoeller, and T.F. Budinger. 1986. Disposal of blood lactate in humans during rest and exercise. Journal of Applied Physiology 60 (10):
Rozenek, R., L. Rosenau, P. Rosenau, and M.H. Stone. 1993. The effect of intensity on heart rate and blood lactate response to resistance exercise. Journal of Strength and Conditioning Research 7 (1): 51-54.
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