The benefits of lactic acid accumulation in muscle cells has been recently debated. Scientists arguing that lactic acid is “the latest performance-enhancing drug” have drawn false conclusions by over interpretation of their data (Lindinger). In “Point:Counterpoint: Lactic acid accumulation is an advantage/disadvantage during muscle activity” a series of debates took place within the Journal of Applied Physiology in search of the truth behind the benefits of Lactic acid accumulation. Jens Bangsbo and Carsten Juel of Copenhagen Muscle Research Center and the University of Copenhagen argue that “, the negative consequences of lactic acid accumulation far exceed any positive effects” (Lindinger). Multiple studies on lactic acid production in humans have linked elevated lactate levels to higher pH in muscle cells. In one study, after completing an arm exercise, subjects were able to perform a subsequent leg exercise at about 75% compared to controls (Lindinger). In experiments with animal models, muscles incubated in lactic acid that underwent repeated exhaustive stimulation showed faster fatigue development (Lindinger). In an experiment with isolated dog muscle, lactate ion perfusion reduced muscle twitch force by 15% (Lindinger). Most experiments conclude that lactate acid effects are associated to the function of the muscle membrane and not the skinned muscle fibers. Other studies have linked lactic acid formulation with impaired performance of Ca2+ release channels (Lindinger).
Evidence also suggests lactic acid production plays a role in conveying fatigue related information to the brain (Ishii). In one study eleven healthy adults performed hand grip exercises at varying intensities for 120 seconds. The exercises caused significant fatigue while their brain activity increased at 30% and 50% maximal voluntary contraction (Ishii). Blood lactate and flow rates also increased during the study; most notably at these percentages. The authors through analysis were able to conclude that these two factors may convey load intensity to the brain during fatigue (Ishii).
Ishii, Hideaki, and Yusuke Nishida. “Effect of Lactate Accumulation during Exercise-induced Muscle Fatigue on the Sensorimotor Cortex.” Journal of physical therapy science vol. 25,12 (2014): 1637-42. doi:10.1589/jpts.25.163
Lindinger, Michael Ivan. “Lactic Acid Accumulation Is an Advantage/Disadvantage during Muscle Activity.” Journal of Applied Physiology, vol. 100, no. 6, 2006, pp. 2100–2102., doi:10.1152/japplphysiol.00213.2006.
