Experimenting with Speed (Pace?)

Today one of my running buddies wanted to try running a little faster than normal to see what sort of pace might be possible to aim for in our half marathon next weekend. We run an average pace of about 10:30 min/mi. She thought it would be fun to see if we could get under 10 min/mi. I thought that would be a fun challenge. We often kind of sit back on our haunches, running conservatively at the beginning, so we have enough energy to keep up the whole distance, and we finish very strong. This is really good for our long runs, but I think on our shorter 5 mile runs, we often save a bit too much at the beginning (of course we also have to get warmed up, which takes a while!). Today we started off much faster than usual, with our first mile taking about 10:16 rather than 10:50 ish, and by the end of our 5 mile run, our overall pace was down to 9:31 min/mi! This is not impressive to fast runners, but as a mediocre runner, I am thrilled! I've only done that once before, back in December when I went out running by myself and I was trying to get my first 5k below 30 minutes to accomplish a goal I'd set for myself at the beginning of the year. This time around, it felt much easier than back in December--I only got super tired at the very end, in the last 1/2 - 1/4 mile or so when we picked up the pace even more. Overall, the run was more difficult, of course. But it was fun! Go us!