W2R1 - lots of little niggles

[UKDana]

At the end of W1R3 I was convinced I'd not be able to manage running for 90 seconds but I've just completed W2R1 and managed every single one of the 90 second runs. They weren't easy and I was pretty close to stopping just as Laura said I could walk but I did them all (and it felt good-ish).

My problem is that even as I set out I could feel lots of little niggles. The middle of my back ached throughout, my groin, behind my knee, etc. Admittedly I did a lot of exercise last week but I've had two rest days between W1R3 and W2R1 where the most strenuous thing I did was walk around the supermarket. Is this just payback for last week? Could it be that I've slept awkwardly (my back was the biggest niggle of all - I don't generally suffer with backache)? Or is it just a sign of my age? I'm running on pavement and have a reasonable pair of trainers. Is the 5 minute brisk walk at the start enough of a warm up or should I be doing more stretching before I go out? Any help/advice greatly appreciated.