At Pinnacle Fitness, The effect of NSAIDs such as aspirin, ibuprofen, and acetaminophen on muscle growth:
A group in 2001, however, using eccentric contractions in human subjects to induce muscle damage, showed that post-exercise NSAID use drastically reduced the increase in protein synthesis normally seen in response to muscle damage. This study is relevant to real workouts because the researchers used a model for muscle damage that is very similar to what what happens during a normal weight training workout and the doses of NSAIDs used in the study were normal therapeutic doses, not unlike those that most people would take for a headache or after a tough workout for soreness
Also read the piece at Again Faster, via which I found the link above.
