Comparing Personal Records

One of the things I struggle with most when it comes to running races is knowing what pace I should target. When I'm sticking with races of the same distance, it's fairly simple to come up with a pace (generally I target a few seconds per mile faster than my last run or my PR). But when I jump between distances, it becomes harder. How do I know how fast I should try to run a half marathon when my last one was six months ago?

While determining what pace to run a half marathon right now is not something I have to worry about, I will soon need to figure out a plan for running a 10K. Can I use my recent 5Ks to predict a 10K time? How does my recent 5K PR compare to my 10K, 10 mile, and half marathon PRs from last year?

Roughly a year ago, a friend of mine told me about Jeff Galloway's Magic Mile. In short, the theory is that taking the time from running a good, hard mile every couple weeks can be used to predict one's performance in longer distance races assuming the runner has properly trained for the distance. I tried a couple of magic miles, but I ran into a similiar problem of not knowing what pace to target for the mile which resulted in an inconsistent pace.

Since then I have found a calculator on Runner's World that will translate a result into various other distances (1500 meters, 1 mile, 3K, 5K, 5 mile, 10K, 10 mile, half marathon, and marathon). So looking at my current PRs, how do they compare?

I think the easiest way to compare the PRs is to convert them to a consistent distance, and I think one mile makes the most sense. Here's how they stack up:

2014 Sacramento Zoo Zoom 10K	6:59
2014 Sac Credit Union 10 Mile Run	7:02
2014 Shamrock'n Half Marathon	7:07
2015 Sacramento Zoo Zoom 5K	7:11

Looking at this, although the speed in MPH of my recent 5K PR is the fastest, it is the slowest PR of the bunch. I'm not surprised by this: I didn't think I would be back to where I was yet. My 2014 PRs are in order by shortest to farthest run, but they are also in order of most recent to least recent. I'd like to think the recent factor plays a bigger role, but I do think my performance decreases in longer runs more than it does for most.

Doing a bit of further conversions, if I converted my 10K PR to 5K, the expectation would be that I'd finish in 23:12 (41 seconds faster than I finished on Sunday which is over 13 seconds per mile faster). If I convert my 5K PR to 10K, I'd expect to finish in 49:50 - nearly a minute and a half slower than my PR. That suggests that if I were to run a 10K tomorrow, that I should target 8:02 per mile. Hopefully by the time I decide to take on my first 10K of the year I will be able to do better than that (depending on the weather).