Now here I am in my second year of triahtlon, just completing my first half iron distance event. I still think of myself as a new-trying to make sense of it all-runner. I figured I would come back to the well for some more expert advice, so here is my question for the runners out there:

At first I could do a 5k at about a 10+ min mile. By my first sprint tri I made it to about 9.5 minutes, and stayed there most of the season, up to my first Olympic tri. This year I started with a sprint and my 5k was about 8:30. We won't talk about the half, my run was sloooooooow, but I felt good finishing. I just did a benchmark 5k this morning and ran an 8:22. First mile was a 7:45, second was an 8 something, and so on. I really don't know what types of drills will really make me faster. I might do some strides, but that's about all I know. If I want to be competitive I've got to get to that 7 minute range at the least (I have a decent bike time, and swim is getting better). Any advice? I've already transitioned from being a heel striker to fore foot running, and I've brought my cadence from the mid 150s to about 180. Any advice would be most appreciated. I felt like my heart was coming out of my chest this morning, and according to the hrm by mile 2 I was nearing the top of my range. I am training mostly for sprints (5ks) now. I'll do more 1/2 training later, but my focus there is more endurance than speed.

Thanks in advance!