How does the blood lactate threshold arise?

Lactate production markedly increases as exercise intensity increases. A possible reason for this occurrence is that fast-twitch muscle fibers become increasingly involved in muscle contraction as heavy workloads arise. These muscle fibers increase the production of lactate much more than slow-twitch (aerobic) muscle fibers do. As a result, blood lactate markedly increases because the athlete can not clear the lactate from the blood as fast as it is being produced. This point at which lactate is being produced at a faster rate than it can be cleared is the blood lactate threshold. When graphed, a sharp rise in the blood lactate level of the athlete is noticed.