Sprint Length (By Time)

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.

Sprint Heat Time Trends

Since I’m starting to accumulate a reasonable collection of heat times from World Cup sprint races, I thought it might be interesting to compare general trends between the few seasons I have data on.

The biggest trends that you can typically see are the differences in tactics between the men and women. Generally what I’ve seen is that the women will ski qualification fairly conservatively and then the heat times will get progressively faster with each round, although possibly tailing off slightly in the finals. The men are generally more “tactical” in that they tend to really hammer qualification and then get a bit more cagey during the heats.

I was curious if these characteristics had changed much over the short time period I have data:

The units on the y axis aren’t in seconds, since I have to standardize the time differences to compare values from different races. But larger values are slower, smaller values are faster, and everything is relative to the median heat time for the entire day, which is pegged at zero.

You can see that the general impressions that I outlined above were strongly influenced by what I saw in the data during the 2010-2011 season, which was where these trends were most stark. This most recent season was mostly similar for the men, although somewhat more variable (shaded region indicates, roughly, variability). Interestingly, though, the women’s data changed pretty dramatically this past season. The qualification round times were in general quite a bit faster relative to later rounds than they have been in the past, and the later rounds became slightly slower, or more “tactical” perhaps.

Do Europeans Race Slower In North America?

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. Read more

WJC Qualification Follow-Up

In a post last week I talked about how I felt that a single early season result wasn’t necessarily a great predictor of how someone will tend to ski (on average) during the rest of the season. I feel like most people would accept that this is, in principle, generally true. Just because you pop a great race in November doesn’t mean you’ll be killing it in February.

A commenter pointed out, though, that while that person with a single great early season result might have worse results in an absolute sense for the rest of the season, they might still do better than everyone else. And that’s really all that matters if you’re selecting people for an event. That’s a good point, so I went for a somewhat more specific comparison and found that my statistical intuition wasn’t quite as correct as I had thought.

The following plot shows the the ranks of the minimum FIS point result versus the rank of the median FIS point result for US juniors:

So the people with the best minimum early season FIS point race really do tend to have the best median late season FIS point results. I was not expecting these to line up nearly this well at all.

Of course, there’s still some variability here that means it’s not perfect. (What in life is?) So you can see several instances where the person with the best FIS result in the early season only had the 4th-5th best median FIS point races for the rest of the season. But it’s much more highly correlated than I would have thought based solely on my mathematical intuition. Chalk one up for my commenters!

How Useful Is A Single Good Result?

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.

New FIS Point Criteria for WJC Qualification

As often happens, FasterSkier gifted me with a handy topic for a few posts to kill time with over the summer by publishing a summary of USSA’s new criteria for automatic qualification for WJCs/U23s.

For WJCs, the FIS point cutoff has been lowered to 50 for both men and women (it used to be higher for women than for men) and it can come from any FIS sanctioned race between Nov 1st and Dec 31st.

Generally, I’m skeptical of the wisdom of allowing people to automatically pre-qualify based on a single race (albeit a good one). But I’ll come back to that issue in a subsequent post. For the moment, I was curious where US juniors might be able to find races with penalties under 50 during that time of year (excluding WC races, of course). So here’s a summary of all such races that fit that bill for recent seasons:

This is showing the number of FIS races in each country within those dates with a penalty less than 50. (Of course, this doesn’t reflect how many skiers in that race broke 50 points, just that someone did.) I wasn’t expecting there to be such a big disparity between the distance and sprint races, to be honest. Part of me is wondering if this rule change will favor juniors who make the effort to get over to Europe during the fall in the hopes of popping a great race. Now that I write that, it occurs to me that encouraging juniors to “go to Europe for their points” might be part of the intent here, but that’s just speculation.

Performance Trends In US Alpine Skiing

This is just a quick note as I sift through some of the alpine skiing data. I’ve made similar plots as these for XC skiing in the past, so these are just the same idea but for the US alpine folks. First a look at the men:

This is tracking the results (per race) for US men over all WC, OWG and WSC races in these events for each season. Since in alpine skiing you routinely have final results with barely more than 30 skiers, I dropped the ‘Top Thirty’ category. The Bode Miller effect is fairly evident, particularly in the speed events (Downhill and Super-G). The GS results have been generally pretty stable over the last decade, with the usual ups and downs from year to year. Slalom has probably been the weakest event, although it’s interesting to note as a XC fan that they’re still pulling down a top ten result fairly regularly.

And here’s a look at the women: Read more

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