There is a scientific reason why you don't feel the pain of a workout until the day after. It's called "delayed onset muscle soreness," or "DOMS." Follow BI Video: On Twitter More from Science ...
Lactate isn't the reason you're sore a few days after upping your weights or exercising after a long break. So, if it's not lactic acid and it's not lactate, what is causing all that muscle soreness?