In my high school days I was a track/cross coutry star, and you couldn't wear me out. Now I'm 25 and noticing my endurance is going to shit! After a few good work sets at the gym my body is shot. I leave sometimes thinking I didnt do enough even though I'm worn out. I dont do ANY real cardio now because I'm trying to gain weight and I feel cardio will hurt my gains. Am I wrong? What pre/during workout drink can I take to give me an xtra boost? thanks