Lactate production is not related to oxygen deficit but rather to the increase of the glycolysis flux. 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 turnover of lactic acid during exercise is several times greater for a given blood lactate level than at rest. 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. Of significance to coaching is the concept itself. Most activities do not require all body parts to be involved in an activity at the same intensity level.