I've just finished week 4 today and while I did all the runs, I did find it quite tough. Just wondering if I should repeat week 4 before moving on to week 5. I had to repeat week 3 as I was out for a week after putting my back out. When I started the programme, I was extremely unfit although not overweight and had never seriously exercised, apart from walking years ago. I'm determined to get to week 9 but don't want to rush it. Advice anybody?