The total lactate/ lactic acid is reported as lactate which is confusing. The amount of total lactate / lactic acid is higher when anaerobic metabolism is producing lactic acid and proceeding faster than it is metabolized. It is the ratio of lactic acid to lactate as a base that reflects the pH.
Lactate is an anion so there has to be a cation in any system. We can have lactic acid which is lactate plus a proton or H+, We can have lactate paired with an inert cation such as a Na+ Sodium. Sodium Lactate is a basic substance whereas lactic acid is an acid. The ratio of lactic acid to lactate base is in equilibrium based on the pH but there is no “free” or unpaired lactate. When the pH is low there will be more lactic acid than lactate base. We don’t need evidence based medicine to test this hypothesis. An understanding of acid base chemistry is all that is needed.