Lactate production retards, not causes, acidosis: a theoretical approach for physical education students.

Resumo

The  widespread  belief that intense  exercise causes the  production  of lactic  acid that contributes to acidose is erroneous.  This belief, carried  out by physical  education  and other  professionals,  interferes on methods of training and raise the opinion that muscle lactate is the vilain of exercise fatigue.  For a theorical  approach  we show a structural illustration of all the glycolysis reactions  with enphasis  to phosphoglycerate kinase reaction  wich envolves a simple phosphate transfer  from the  first carbon  of1,3 bisphosphoglycerate to  ADP,  forming  ATP.  The  carboxyl  group  of 3 phosphoglycerate remains unprotonated for the remaining  intermediates of glycolisis. From this biochemical fact it is impossible the production of acid lactic causing the release of a proton.  Actually,  glycolysis releases 2 protons  and lactate formation  consumes 2 protons.  After this biochemical explanation we present three  illustrated exercises situations: low intensity, anaerobic threshold  and high intensity exercise. From this point the students can understand that the protons  came mainly  from the ATP  hydrolysis  and when the ATP demand  for muscle contraction is met by mithocondrial respiration, there  is no proton  accumulation in the  cell as protons  are  used  by mithocondria to  maintain the  proton  gradient in the  intermem- branous  space.  When the ATP  hydrolysis exceeds mithocondria buffering capacity  and ATP  demand is supplied  by nonmithocondrial sources,  protons  increase  inside  the  cell causing  acidoses.   Lactate production  increases  under  these  cellular  conditions  to  prevent  pyruvate accumulation and  supply the  NAD+  for glycolysis.  Lactate also retards the acidoses by the  symport with protons  (from ATP hydrolysys  not  from lactate production) mediated  by Lactate Transporters (MCT).  Thus,  increased blood  lactate detection  is the  effect  not  the  cause  of acidosis.   The  students  must  understand that if muscles do not  produce  lactate, acidoses and fatigue  would accour faster,  impairing  high intensity exercise performance.  This information must be considered  in their  training schedules.