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Lactate, Lactic Acid and Acidosis

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With respect to exercise, what do you think of when I say, “Lactic Acid?” Legs burning? Acidosis? Horrible stuff that slows me down? Lactic acid and lactate typically get a bad rap from athletes, but what if I said that rather than slowing you down, lactate production enables high-intensity exercise? Well, it does. Lactate vs. Lactic Acid      First, let’s discuss the compound itself. Lactate is not lactic acid. Lactate is a carboxylate, whereas lactic acid is a carboxylic acid. This means the carboxyl group of the lactate molecule is deprotonated and cannot contribute further to acidosis.  The image below shows the difference between the two molecule types.      The reason lactate does not exist as it's protonated acid form in the body is because the pKa of lactate is a low 3.9. This means is that in a solution with a pH higher than 3.9, the compound will exist as the deprotonated carboxylate, lactate.  As shown below, in Table I from Cairns ( 2006 ), the
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Fractional Utilization, Low Carbohydrate Diets and Running Performance

Fractional utilization refers to the fraction of VO2max that an athlete sustains during an event. It varies between events and between athletes. An athlete can sustain a greater percentage of VO2max for a shorter duration (5000m vs. 10,000m). Fractional utilization is sometimes referred to as lactate threshold. While the concepts are related, they are not the same. Consider an athlete with a VO2max of 70 ml/kg/min: If we find that he can average 90% of VO2max over the course of a 5000m run, he averages 63.0 ml/kg/min for the race. If he averages 86% of VO2max during a 10,000m run, he averages 60.2 ml/kg/min. Athletes may train for years, increasing fractional utilization. By increasing fractional utilization, an athlete will be able to complete a distance at a greater percentage of VO2max. For example, if that same athlete increases his fractional utilization during the 5000m to 93%, he can now average 65.1 ml/kg/min. That 2.1 ml/kg/min increase in utilization means more O2 is cons
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Relationship between aerobic and anaerobic metabolism

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Some coaches will speak of the elements of performance as exclusive concepts. Aerobic and anaerobic metabolism for example. Traditionally, the two could be separately defined, but we've known for some time now that the two are essentially bound in a symbiotic relationship. They're both a piece of the pathway that creates ATP. A typical physiological response from high intensity intervals, sprints, a finishing kick or a high intensity (<30 min) race is an accumulation of lactate and H+ ions. We know an accumulation of H+ ions (acidosis) will decrease performance capacity. The table below from Cairns, 2006 lists some proposed mechanisms through which acidosis inhibits performance. If only there were a mechanism in place to remove these pesky ions... Then, we could perform at a higher intensity for a longer period of time. But wait, there is! Oxidative phosphorylation, more commonly known as the electron transport chain or "aerobic metabolism," consum
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