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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 bel...
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Muscle Damage and Running Economy (Part 2)

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"It's the economy, stupid."      The implications of muscle damage during endurance events presents a paradox - the very act of racing progressively reduces our ability to maintain race pace. But it's not as simple as just muscle damage leads to reduced running economy. While the data we collected in our research project described in Part 1 demonstrate acute effects of muscle damage, the real-world implications during long races like marathons and ultramarathons are more complex and potentially performance limiting.      During a marathon, muscle damage accumulates through the race. Unlike the controlled laboratory setting where damage is induced through a single session of eccentric exercise, race-day muscle damage is compounded by multiple factors: repeated eccentric loading from thousands of footstrikes, environmental conditions, terrain, and the high-intensity nature of racing. By mile 20, when many runners hit the proverbial "wall," they're not jus...
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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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