Really I am gnashing my teeth at myself, I knew when I ran yesterday that I had serious soreness in the left thigh muscle and should not go and try to do run intervals today! However I was unwilling to abandon previous plan. It was quite uncomfortable immediately and grew more painful as I continued to run, so I stopped before the end of the 2nd of 4 sets, alas. Coach is wiser than I, I wanted to run the rest of the workout at slower speed but he pointed out that if it is actively painful, better to stop now and not end up having to take weeks off for an injury!
1 mile warmup + 400m additional warmup
4 x 200 on 1 min rest, 4 mins set rest, 3 x 200 on 1 min rest, bit of further walking
(It certainly was enough of a workout to give me the endorphins! But I won't try to run again for another couple days - this is not as painful as a grade 1 hamstring tear I had a few years ago, but it's definitely enough of something wrong that I shouldn't do things that exacerbate it!)