Something to do with inhibiting certain inflamitory messengers that trigger muscle growth.
Listen, Ive been running 400mg Ibuprofin almost every day for a while now. Sometimes 800mg. Ive made great gains in strength and size both on and off cycle. I dont take it immedietly before or right after training.
If I take it in the evening, its 3-4 hours after working out. If I take it in the morning, its 6-8 hours before training. I dont think its affecting me that much, maybe 20% or something like that.
You have to look at the big picture. If your joints/tendons cant heal from your training sessions, you cant work out, so whats going to build more muscle - not working out or taking Ibuprofin and working out?