It has been found that fast twitch fibers generally produce more lactate than slow twitch.
If a person has a preponderance of fast-twitch muscles there is no chance of him or her becoming a world-class marathoner.
The perfect Olympic sprinter has legs bursting with fast-twitch muscle fibers that work without much oxygen.
They are a combination of the two not fully fast twitch or fully slow twitch.
In other words, fast-twitch fibers were primarily responsible for the huge upswing in blood lactate.