I've been doing the c25k on my treadmill in the garage. On Thursday I did wk4r1 and kinda thought it was easy....so seeing as ive signed up for a 5k at the end of march i thought id try doing w4r2 outdoors. So this morning i loaded up my ipod and off i went....problem was It didn't go as planned. I was EXHAUSTED by the end. It is so much harder to run outdoors than on a treadmill. So have decided i need to switch to doing the program outside and retire my treadmill sessions. I think i might have to extend and repeat week4 just to get up to speed. I really felt like i had not completed weeks1-3. I have to say...i enjoyed the session much more. Running outdoors is less boring...there is more to look at and it was just a beautiful morning...chilly but not freezing. I did enjoy it more. I guess im an outdoor convert!