Thanks Eric. Again, I'm not sure why I've got the curiosity - it isn't like I'm likely to go out and score some juice just to gain some endurance.
Besides, trumpet playing isn't about brute strength - it's about finesse and balance, although strength does play a small part in the overall picture, unless of course someone has evidence to the contrary.
From what I have read, certain steroids have an overall effect on a person, not only in strength and muscle gain, but also in a feeling of well being and confidence, and those things can affect your playing too.