Van Hall, G. (2009). Lactate in whole body exercise: An anaerobic end product and an aerobic substrate. A paper presented at the 14th Annual Congress of the European College of Sport Science, Oslo, Norway, June 24-27.

"Lactate has been considered a dead end waste product of glycolysis due to hypoxia and a major cause of fatigue. The produced lactate thought to be cleared by the liver for gluconeogenesis. However, it has become clear that skeletal muscle continuously produces lactate, and during exercise without an apparent lack of oxygen. The increase of lactate production with exercise is dependant on the acceleration of glycolysis causing an increase in pyruvate and NADH concentration that will shift the equilibrium enzyme lactate dehydrogenase to lactate formation. Moreover, during exercise the active muscles are by far the most important tissue for lactate uptake and subsequent oxidation. Thus, the muscle net lactate release, and to a large extent the systemic lactate concentration, depends on the balance between the active muscle lactate production and simultaneous utilization. This concept becomes very clear during diagonal stride roller skiing at about 75% VO2max. A relative small increase in arterial lactate (~2.5 mmol/L) occurs despite a very high whole body lactate production (~14.1 mmol/min) caused by the large release of lactate by the arms and legs. However, the legs take up and oxidize substantially more lactate than they produce. Thus, due to the large leg muscle mass and energy requirements for contraction, the legs are able to clear and oxidize most of the lactate that is produced during diagonal stride roller skiing keeping systemic lactate concentrations low. In addition, the arms are equally efficient in lactate utilization per kg of muscle than the legs, however, the arms produce far more lactate than they consume, that is, they are more glycolytic than the legs. These findings imply that systemic lactate levels are no measure for aerobic/anaerobic capacity of athletes in different sport disciplines. Moreover, in sports that use both the arms and the legs, such as rowing, swimming, and cross-country skiing, lactate levels will depend on the relative utilization of arms versus legs. This implies that blood lactate levels cannot be used to evaluate training status or technique."

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