text: LDH is also regulated by the relative concentrations of its substrates.  LDH becomes more active under periods of extreme muscular output due to an increase in substrates for the LDH reaction.  When skeletal muscles are pushed to produce high levels of power, the demand for ATP in regards to aerobic ATP supply leads to an accumulation of free ADP, AMP, and Pi.  The subsequent glycolytic flux, specifically production of pyruvate, exceeds the capacity for pyruvate dehydrogenase and other shuttle enzymes to metabolize pyruvate.  The flux through LDH increases in response to increased levels of pyruvate and NADH to metabolize pyruvate into lactate.