I've done all my Couch to 5K running in the gym on a treadmill at 1% incline (for easier transition to trail running later). I've been planning to complete the C25K on the treadmill and then switching over to trail running outside when the weather is nice. I know that even with the incline, it will be an adjustment though.
I completed C25K Week 3 Day 1 yesterday, now it my leg day on the weights tonight.
