Originally Posted by terrymorse

Inflammation, sounds good.

From a German abstract (translated):

"In the past few decades, many hypotheses have been developed to explain the aetiology of DOMS. Although the exact pathophysiological pathway remains unknown, the primary mechanism is currently considered to be the ultrastructural damage of muscle cells due to unfamiliar sporting activities or eccentric exercise, which leads to further protein degradation, apoptosis and local inflammatory response."