I’ve determined that there’s a fairly linear relationship between my weight and my finishing time for any given distance.

10K Time (minutes) = .538 * Weight (pounds) – 39.573

My 10 K PR is 50.82 minutes, so my target weight to hit 50 (± 1) minutes is 166.5 (± 0.9) pounds (I was actually just under 172 lbs at the time, so I over-performed.). I’ve been trying to lose 1/2 lb per week since late January. So far I’m well ahead of schedule, but I’m sticking with the planned rate and not trying to force continued “excess” loss. Since I’m about 173.5 right now, that means I’m shooting for 167 on the day of the Great Race, 09/30.

Being the nerd I am, I also did a regression with both weight and distance predicting minutes/mile pace.

Pace (minutes/mile) = .142 * Distance (miles) + .063 * Weight (pounds) – 2.942

For a 10K race (6.2 miles) and a weight of 175, the prediction is 8.96 minutes/mile. I ran 8.63 minutes/mile on Sunday.

I’ve been weighing myself almost daily since mid-2003. I also have my race times dating back to 2005 recorded in a spreadsheet. I have multiple times and weights for each distance. For instance, I’ve run the Fathers Day 10K every year since 2007, Great Race 10K every year since 2005, and the Run around the Square 5K every year since 2006. I have an assortment of “one-off” race times at various distances, too.

All I did was feed a sheet with four columns to SPSS: weight, distance, total time, and pace. I ran two different linear regressions, one with weight, distance fixed to 10K, and total time; and the other with weight, distance, and pace. I let the regression routine handle the rest.

I ran the regressions in the first place because I began to suspect that improved fitness was having a negligible effect on my finishing times. The results seem to support that hypothesis. On the other hand, improved fitness helps me run farther and faster when training, leading to additional weight loss, and weight loss helps me run farther and faster in my training, so fitness can’t be ignored. No surprise there. What was surprising to me was just how strong the dependency on weight was.

Cool, huh? If only this counted toward my dissertation… 😉