Disadvantages of Lactic Acid in Human Performance Disadvantages of lactic acid in human performance – counterpoint article Lamb 2006; Robergs 2004; Bangsbo 1996.

Increase abundance of H+ ions can change the pH level. Lactate is produced as a result of ATP formation via non oxidative energy system – glycolysis Increased lactate concentrations in the blood have been observed, resulted in decreased athletic performance Increase abundance of H+ ions can change the pH level. Negative effects of lactic acid could be multi- factorial With high intensity exercise, immediate and non oxidative energy systems are used to produce energy (ATP). Studies have shown that as lactate levels increase in the blood as a result of high intensity exercise, performance levels have been observed to decrease The utilization of glucose via glycolysis can cause a change in the pH due to an increase abundance of H+ in the muscle cell Changes in pH levels and the accumulation of lactate could be multifactorial leading to acidosis and decreased athletic performance

Graph – open circles represent control group performing exercise to point of exhaustion with no lactate build up in blood Darkened circles represent exhaustion point when lactate already present in blood via UE exercise and subjects were asked to perform a LE leg extension exercise Y axis on left – represents blood lactate levels Y axis on right side – muscle pH. Notice that as muscle pH level decrease as of lactate formation in blood, the potential for exhaustion is sooner.

H+ could depress Ca 2+ activation of actin myofilaments Increased levels of lactate and H+ ions could impair SR Ca 2+ release channels H+ could depress Ca 2+ activation of actin myofilaments H+ induces a reduction of the Ca 2+ reloading into the SR Studies have shown that the handling of intracellular Ca2+, through increases in lactate levels and H+ions may induce an impairment to the SR Ca2+ release channels This may have an effect of the actin myofilament during muscle contraction H+ions could reduce the amount of Ca2+ that is available for reloading in the SR

Additional controversies: Difficulty in extrapolating the results to in vivo conditions – exercise performance in humans Studies based on isolated, non contracting muscle and skinned muscle fibers resulting in artificial non exercise related conditions Positive correlation between transport capacity and performance, suggesting that lactic acid accumulation is a disadvantage. Although high levels of lactic acid & low pH are not primary cause of fatigue, it appears to contribute to fatigue during intense exercise Studies were mainly conducted on animals hard to infer results to humans. Experiments conducted on resting muscle of animals Positive correlation btwn transport capacity and lactic acid accumulation. (higher LA, less capacity to transport) Although high LA & low pH levels are not the primary cause of fatigue in humans, it appears that it contributes to fatigue particularly when performing intense exercise.