I tried itrain #19 this morning and I about died. This workout is tough. I definately know my weak areas are sprinting uphill. Just 60 seconds on those hills sprinting killed me. I wasnt rested up like I was when I did #13 so maybe that is why but man I am drenched from head to toe. It kicked my butt, thanks for recommending it! I am determined to take on this challenge. she recommends not doing this workout more than 2x week and says it will make you faster. I hope so. Right now I am only doing the itread workouts 1x week because I run outside the other 2days a week. Do you think that is enough to see a difference in pace? thanks gayle!