Critically discuss the use of gas exchange (Vt1, VT2) and blood lactate threshold (LT, LTP) in the evaluation or pedicted perfor - Essay Example For a long time it was believed that peak oxygen uptake or power (VO2 max) is the best indicator of the shape and physical condition. The level of peak oxygen uptake is a measure of the ability of the organism to transport and use oxygen. It is calculated in absolute levels liters per minute (l/min) or a relative measurement of usage of oxygen per kilogram per minute (ml/kg/min) (Bassett and Howley 2000). Nevertheless some new studies have suggested that the so called anaerobic threshold is much more reliable method for evaluating the physical endurance and fitness (McArdle, Katch and Katch 1996). In order to understand this we must first talk about the metabolism that is involved during physical exercise. The main systems of energy production during exercise are ATP system, anaerobic system or glycolisis and aerobic system or mitochondrial respiration. However we must understand that they are not separate but are simply all part of one chain of events that eventually leads to production of ATP, which is the main source of energy in human organism. During the low level exercises which doesnâ€™t require much energy muscle fibers almost exclusively use aerobic mitochondrial production of energy. This is much slower source of energy compared to anaerobic glycolisis but much more effective because from one molecule of glucose produces 29 to 30 molecules of ATP, instead glycolisis produces only 2 molecules of ATP from 1 molecule of glucose. It is estimated that mitochondrial respiration is 19 times more efficient than glycolisis. This is why during low level exercise our body tends to use mitochondrial respiration as a source of energy. However in the metabolism of glycosis - the main energy source used by muscles is conducted through both aerobic and anaerobic metabolism. In the anaerobic metabolism glycosis is converted to pyruvate. This molecule is then further metabolized to oxalate and eventually to CO2 and water in the mitochondrial aerobic metabolism. In a case of sub-maximal endurance physical involvement muscles almost exclusively use mitochondrial aerobic metabolism and pyruvate is almost completely metabolized. This is why at rest and low level exercises blood levels of lactate are normal. But in a case of extensive exercise there is a demand for more energy and therefore more glucose is metabolized to pyruvate. There is a point where the mitochondria are no longer able to metabolize all the pyruvate that is produced and some of it is converted to lactate which enters the blood and muscles. This lactate is than utilized by the liver (and converted to glucose) or heart or kidneys. The point at which at physical exercise the blood concentrations of lactate start to rise is called lactate threshold point (Bassett and Howley 2000). Actually some authors differentiate two distinct lactate thresholds or aerobic and anaerobic lactate threshold. The first, aerobic threshold is the point in the intensity of the physical exercise when the blood lactate levels start to rise. The second, or anaerobic lactate threshold is the point when the concentration of lactate reaches the maximal steady state of concentration (MSSL), when the concentrations of lactate in the blood and muscles reaches maximal stabile values (that can be maintained for some time without further incensement) and it is estimated that in different people ranges between 3.1 and 5.54 mmol.1-1,
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