Statistical Skier

By request, we’re looking at how the length of World Cup sprints has changed over time. Specifically, since the length in time of the effort is really more meaningful than the length of the course in terms of distance, that’s what we’ll consider.

So the following graph shows the average of the top five qualification times for each World Cup (and Olympic and WSC) sprint race for the past six seasons or so:

The races in red are all, roughly speaking, short courses. Many are city sprints. The actual cutoff I used wasn’t exactly 1km, but you get the idea. I was just trying to highlight the fact that there’s a set of sprint courses that are quite a bit different than the rest. But snow conditions, weather and hilliness can create a fair bit of variation themselves, as well.

The trend line in blue represents the median time per season (excluding the shorter courses in red).

I’d say that the women’s freestyle sprints got a bit longer last season, but other than that things are mostly unchanged. In fact, it seems like they have the men’s freestyle sprint courses pretty well dialed in at 2.5-3 minutes or so. The men’s classic courses look like they got a hair longer in 2009 and 2010, but have come back down on average.

Three minutes seems like a reasonable length to me (although I’d be curious what racers and coaches feel like is the “optimal” length for a sprint race effort), and we’re certainly in that general ballpark. Perhaps the women’s classic courses could be shortened slightly, but that’s the only adjustment I’d make, I think, assuming the women’s freestyle times drop back down again next season.

Whether or not you like the really short courses is an entirely different matter, of course.

Travel is a big issue for cross country skiers, particularly those of us living in North America.  Flying back and forth to Europe can be both time consuming and exhausting for athletes.  Obviously, this can have some serious effects on performance.  Of course, this works both ways.  Presumably it’s difficult for Europeans to travel to World Cups in North America as well.

Let’s see if we can see any general trends in the data. Continue reading ›

Following up from last time, we’re still discussing the recent USSA rule changes for qualifying for WJC/U23s. Now, it’s not like USSA has a ton of options here, but I would like to point out a few difficulties with pre-qualifying an athlete using only a single result.

Being a stats guy, I always think about things in terms of variability. So when I think about a skier’s performance, I visualize it as having a distribution. An athlete’s best races come from one extreme end of that distribution, but they are necessarily fairly rare. So to my way of thinking, a skiers best race isn’t a good estimate of how well they’re likely to ski. Rather, it’s a good (-ish) estimate of how well they might ski, if we’re really lucky.

To give you some context on this, I took all the FIS point results for Americans since 2006. Then I counted up how often each skier matched (or bettered) their best FIS point race from the early season (11-01 to 12-31) during the rest of the season. I counted this separately for men/women and sprint/distance and only kept folks who had at least 4 early season results, and at least one result from the remainder of the season. Here’s what we have:

I’m not quite so interested in the sprint numbers, since FIS points are such a dicey way to measure performance for sprinting. But if you look at the men’s distance panel, what this is saying is that they ski as well (or better) than their best early season result at most once more that season around 60% of the time. The drop-off is a bit less dramatic for the women, but still it is much more likely that you aren’t going to see a race with FIS points that low for the rest of the season.

And this trend is even more stark when we focus in on just the group of skiers who’ve managed a sub-50 point race during the early season:

Granted, this simple method of counting the number of results at a certain level may obscure some things. For instance, maybe folks don’t race quite that fast ever again, but they come pretty close fairly often. That will require a different sort of analysis that we’ll delve into next week.