So how long was that nationals swim, anyway?

We all know that an accurately measured swim course in a triathlon is about as rare as a liquor store in Lubbock. I happen to think I've been pretty lucky with swim courses so far, though, usually coming in within a minute or two of expectations. Given all that can go wrong in an open water swim, currents, pack dynamics, run up to transition, that is pretty much as well as one can hope for. But nationals was a different story, with all time goals going out the window when I came out of the water and saw my swim time.

That's why I think it's important to emphasize, especially to those coming from swim and track programs, that there is a difference when you go to open water swims and variable difficulty courses. In the pool or on the track, your time is your time, whereas in triathlon, it's all about who you beat compared to last time.

That being said, can we determine how long the swim at nationals was? Fortunately, about a month before nationals, many of the same athletes competed at lake Havasu which I feel was pretty spot-on in terms of swim distance. So, I took a sample of all men and women that competed at both Havasu and nationals, and started looking at statistics. First, the correlation (r=0.947) was very good and tells us that the havasu time was a very good predictor of nationals time. The average time difference was 5 minutes, but this can't be applied across the board because, assuming the swimmer swam at the same speed for both courses, the slower swimmer will have a greater time differential, since the time to swim the same incremental distance will be longer.



Instead, the ratio of nationals to havasu times should be the best indicator of course length. Using this metric, on average nationals times were 19.3% slower than Havasu, with a standard deviation of 5.5%. This gives a course length (assuming Havasu = 1650 yds) of 1968 yds, plus or minus 90 yards. So to get your 'real' swim time, divide by 1.193.

There are a couple of factors this analysis doesn't account for. First, swim paces should slow when swimming a longer distance. However, I don't think this is too big of a factor because a triathlon swim is usually not done at the 100% effort (to save for the bike and run), so when a course ends up being long by a bit, it should not be necessary to slow down. Another factor is the impact of tapering from havasu to nationals, meaning that most athletes should be faster at nationals than at havasu. This might explain some of the lower percent differentials from havasu to nationals, the lowest of which was 11%, and could bias the distance correction to be a little short. Use of wetsuit was also not controlled for, but should be a minor factor since I think most people that had wetsuits in havasu had the same wetsuit at nationals.