i'm positive stretching is not the problem because i do the same thing as you. before, during, and sometimes after, i like to get a light sweat before workingout also. but yes i'm on tbol right now but i have never experienced this before on any oral i have ever taken including tbol. i'm fairly certain they are back pumps but i'm just trying to make sure. it's hard to tell because i did back last night with no problems and decided to wait for the tbol to clear out the active stuff before i took more this morning to see if it would go away. it definitely wasn't as bad but still there from working it out last night. i'll do the same thing tomorrow morning and see what's up...