I wonder if it is less that it gives you the strength, but more that it helps with pain blocking and reaction, but with the downside that you got to take it RIGHT before the fight, and that the aches and pains will still be there when it wears off. I don’t recall them mentioning that it had no side effects, so I would imagine that the side effects weren’t quite plot-relevant enough to devote time to, and were handled “off camera”, so to speak.