Lactate is produced constantly, not just during hard exercise. It may be the most dynamic metabolite produced during exercise since its appearance exceeds that of any other metabolite studied. The constancy of the blood lactate level means that entry into and removal of lactate from the blood are in balance. The turnover of lactic acid during exercise is several times greater for a given blood lactate level than at rest. For a given blood lactate level, lactate removal is several times greater in trained than in untrained persons.
Several factors are responsible for the lactate inflection point during graded exercise.
Contraction stimulates glycogenolysis and lactate production. Hormone recruitment affects both glycogenolysis and glycolysis. Recruitment of glycolytic fast-twitch fibers increases lactate production. The practice of attributing any observed lactate-test differences, no matter how small, to training effects or as revealing the trained state is extremely dubious at best. There are more profitable and useful activities for athletes and coaches to be engaged in.