Big Shoulders Stats: Come on down, ladies!

How ’bout some more fun with stats? In yesterday’s post we saw Big Shoulders’ explosive growth over the years. How does this break down by gender?

Historically, more men than women have taken the plunge, but the gap has narrowed in recent years. In 2009, women were 43% of the total participants.

Stormy, Husky, Brawling

Less than 3 weeks ’til Big Shoulders! This race has a special place in my heart: It was at Big Shoulders ’09 where I caught the open-water bug. Without which, this summer wouldn’t have been nearly as awesome.

Little did I realize that Big Shoulders would soon be my hometown race. And I’m happy to see it prosper: In its 20th year, it reached the maximum registration of 800 swimmers for the first time. That’s an eightfold increase since 1998, the first year for which results are available on the web.

To facilitate analysis across years, I aggregated these 12 years of results (1998-2009) into a single CSV file. This is what you might call a picture of success:

— Notes —

  • 1999: first year that a 2.5K race was offered
  • 2005: 2.5K race was the USMS 1-3 mile national championship
  • All data-slinging, number-crunching, and picture-making performed with the assistance of R and ggplot2.

Elite vs. Masters in the open water

What’s the difference between Masters open-water races and elite FINA or USA-S open-water races? I would argue, it’s not so much the absolute swimming speeds (1:10 per 100m for 10K, compared to 1:20 to win almost any Masters 10K), but the variability of swimming speeds.

Masters races have a much wider spread of abilities. In this year’s USMS 10K at Morse Reservoir, the top 10 finishers were separated by 9 seconds per 100m, and the winner was a full 29 seconds per 100m faster than the median finisher. What this means is, most people are swimming most of the race by themselves.

In FINA races, the spread in abilities from top to bottom is (I would guess) less than 5 seconds per 100m. What that means is: lots of pack swimming. In order to successfully break away from an open-water peloton, a swimmer will not only have to swim faster than the others in the pack, but fast enough to break out of the peloton’s draft.

As a result, elite races are characterized by 8-9K of conservative, highly tactical swimming followed by 1-2K of balls-out sprinting. In contrast, Masters races – especially those over an hour (for the winner) – more closely resemble “time trials.”

As an exhibit, here are the 2K splits (with 100m paces) from the June 2010 USA-S 10K National Championship, provided by Powerhouse Timing:

A Gemmell (M-3)
J Kinderwater (M-6)
0:23:22.69 0:01:10.13 0:23:21.75 0:01:10.09
0:23:43.88 0:01:11.19 0:23:43.41 0:01:11.17
0:23:52.90 0:01:11.64 0:23:54.31 0:01:11.72
0:23:46.10 0:01:11.31 0:23:46.10 0:01:11.31
0:22:30.27 0:01:07.51 0:22:35.97 0:01:07.80
C Sutton (F-1)
C Jennings (F-2)
0:23:49.27 0:01:11.46 0:23:49.27 0:01:11.46
0:23:59.33 0:01:11.97 0:24:00.26 0:01:12.01
0:24:12.62 0:01:12.63 0:24:13.78 0:01:12.69
0:23:35.20 0:01:10.76 0:23:28.99 0:01:10.45
0:23:42.40 0:01:11.12 0:23:48.06 0:01:11.40

These were the only four swimmers for whom all 5 splits were recorded. For the men, Gemmell and Kinderwater finished 3-6 (negligibly behind the winner), and for the women, Sutton and Jennings finished 1-2. Interestingly, the splits were almost identical through 8K, for both men and women. In the last 2K, the men seemed to find a new gear – almost 4 seconds/100m faster – while the women maintained their previous pace.