Have had lower back pain since I did my Park Run on Saturday, nothing too painful but just a nagging. So checked it out on the internet (like you do) and apparently I am leaning forwards (yes I think I do) and what with doing more training than normal last week and a Park Run I just think it's taken it's toll. Solution apparently is to change the way you run and to improve your core stability (easier said than done I thought).
Well although my back was sore decided I would try my first long slow run as described in my running magazine. These are done at a slower pace, so you get used to increasing your distance. So off I went on the treadmill at 4.2 mph, chest stuck out so I wasn't leaning forwards. I did almost come flying off the treadmill when my son came home from school - must remember not to turn around to talk.
So it was the first long slow run I'd done, it was the longest distance of 4 miles I had achieved and the longest I had run without stopping just under 1 hour. In addition my back is fine, in fact it hurts less now than before I did the run. Did give it a good stretch out afterwards.