I have read a few articles around the subjects and i thought the finding were interesting.
When you’ve had a hard workout you may experience muscle pain and the odd adage is telling you that this pain is caused by the buildup of lactic acid in the muscle.
DOMS is not caused by lactic acid buildup in the muscle. This is the myth that refuses to die. Within one hour after exercise, most, if not all, of the lactic acid produced is removed and recycled.
The lactic acid myth was passed fro the scientific community to mainstream because scientist genuinely believed for a long time that lactic acid was the cause of pain.
“It’s one of the classic mistakes in the history of science,” Dr. Brooks said.”
Its origins lie in a study by a Nobel laureate, Otto Meyerhof, who in the early years of the 20th century cut a frog in half and put its bottom half in a jar. The frog’s muscles had no circulation — no source of oxygen or energy.
Dr. Myerhoff gave the frog’s leg electric shocks to make the muscles contract, but after a few twitches, the muscles stopped moving. Then, when Dr. Myerhoff examined the muscles, he discovered that they were bathed in lactic acid.
A theory was born. Lack of oxygen to muscles leads to lactic acid, leads to fatigue.

So what does cause muscle pain ?
Studies show that the vast majority of pain associated with DOMS is caused by the action of stretching muscles ‘Eccentric’, in which the muscle fibers are lengthened as force is applied to them.

Lactic acid is actually a fuel. Muscles make it deliberately, producing it from glucose, and they burn it to obtain energy. The reason trained athletes can perform so hard and so long is because their intense training causes their muscles to adapt so they more readily and efficiently absorb lactic acid.