Why you don't use NSAIDS for exercise induced muscle soreness
A commonly misunderstood phenomenon, muscle soreness has absolutely nothing to do with lactic acid. I've already elaborated on this in my hub "Delayed Onset Muscle Soreness".
That said, I won't go further into those mechanisms. The point of this article is to show why non steroidal anti inflammatories and antipyretics (acetaminophen) should not be used for muscle pain from training. These drugs all work through the same mechanism. They inhibit prostaglandins. While prostaglandins do in fact cause you to feel the pain from muscular exertion, they have many roles. For instance, NSAIDS cause stomach upset because they mitigate prostaglandin 1. Prostaglandin 1 helps protect the stomach lining.
Prostaglandins are also responsible for dilating blood vessels in the kidneys. People with kidney problems should not use NSAIDS.
Many of these prostaglandins are responsible for anabolism in muscle tissue. Inhibiting them will only limit your muscular gains. They have no healing properties, so the use of NSAIDS should be avoided altogether by persons who train hard. This isn't just important for weight lifters, but for any athlete.
Another reason not to use them, nor any pain reliever/pain killer is the body's own mechanism for repairing that damage.
Pain signals trigger the release of mucophages. These mucophages are charged with delivering IGF-1 (insulinlike growth factor) to the site of the damage. IGF-1 is a very powerful growth factor, and is metabolized from human growth hormone in the liver.
Okay, say that's not enough reason to avoid them. As if that weren't problematic enough, NSAIDS can also cause the destruction of stem cells. These "blank canvas" cells can take the form of virtually any material in the human body. Of course, that's important to the repair of any tissue. Stem cells circulate freely throughout the bloodstream. There are certain types of stem cell therapy where your own blood is used to extract these cells. Blood is placed in a centrifuge and spun down. The stem calls are then harvested and placed in the area trying to be repaired.