It great to be able to run again. If indeed he was talking about lactic acid, he is a victim of misinformation. . . . Lactic acid is a normal byproduct of muscle metabolism. Karl King Larry asked about this and Jay responded. After 8 years or so of regular massage, I'm a big fan of it.
Massage is more effective if one does it daily or after each hard run.
A couple times a year I go to a professional who gets out the stuff I miss. It is normal to get very thirsty during the massage because the manipulation of the muscle tissue allows for more water to fill the interstitial spaces. So have a big glass of water after a thorough session. I've never gotten convincing answers to such questions. It can't be lactic acid left over from previous runs.