I was able to do the first day work out even though it was hard. But I did repeat week one before moving to week 2. So I would recommend attempting to do the workout and if you need to back off some of the runs to a brisk walk and repeat the week until you have those 8 runs down. One thing I have found is that the first 2 runs and the last one are the hardest. The ones in between are the easiest because my body is all warmed up. This will increase your stamina. I have been a walker for exercise the past couple of years so this is quite challenging. I just did my week 2 day 1 and it wasn't as hard as I thought it would be.