I'm in a volunteer study on that right now. Just gave another quad muscle tissue sample yesterday (STAB----OUCH!!!). There will be an artilcle published at the end of the study, out of Cal State Northridge. It's a control group of a couple dozen guys age 16 to 55, and they're comparing how fast the lactic acid flushes out of muscle tissue, at what age, and with what kind of athletic history. It also will reveal how the muscles react to scar tissue from old injuries, and from other kinds of damage. I've been stabbed in the leg with an 11-ga, 3" needle 5 times now to snatch out a piece of muscle, and at least 8 more to go. My thighs look like I got hit with a sweep of an Uzi.
The study is going on until summer, and I think the paper will be written some time after that. I'll get a copy of it before it's released, and I'll post here.
Charles