Sprint Performance By Length (Con’t)

Continuing on from last time, we’ll single out a handful of skiers who appear to do significantly better in shorter sprint courses. Same methodology as before led me to pluck out the following three skiers:

In general, the effects in this direction tended to be weaker and less dramatic, even at the extreme ends of the distribution. Speculating wildly, I’d venture a guess that given the endurance characteristics in skiing, you’re just more likely to have people with skill sets that lend themselves toward longer distances, all things being equal.

Manificat isn’t necessarily known for his sprinting, but he seems to have done better (in qualification, at the very least) on sprint courses closer to 1km. I find that kind of interesting because I generally think of him as being stronger in longer distance races (i.e. 30km+) though I haven’t looked at any data to check that.

It’s tempting to dismiss Simonlater’s trend as being the result of those three shorter races. But even if you exclude them, you can see a fairly abrupt break in performance right at 1.4km. It’s verging on being a step function, rather than a continuous change. Weibel’s trend is the most marginal, in my view.

Sprint Course Length Effects

The notion of an athlete preferring distance races of a particular length is pretty familiar, but what about sprinting? The differences between a 0.8km and a 1.8km sprint course may not seem like much compared to the differences between a 15km and 30km race. But (while I’m not a physiology expert) it seems likely to me that you could very well run into much more significant differences in the physiological demands at that smaller scale, in terms of what sorts of things your body needs to be efficient at.

That’s a long winded introduction to my having run through some simple linear mixed effects models that look at skiers who have a particular tendency to do better (or worse) in sprint races of different lengths. I’m going to start you off with the graph, which is fairly self-explanatory. But be warned, there will be quite a list of caveats…

The pool I’m drawing on here are folks who’ve done at least 10 major international (WC, OWG, etc.) sprint races. One tricky thing with sprints is what you use as your response variable. I’ve chosen four of the skiers who exhibited the strongest effect in one direction, towards better performance on longer courses. I’m using the final position (not qualification rank) here. In a lot of ways, looking only at qualification speed would be “cleaner”, but I wanted a measure that captured more than just one round of the event; a measure that reflected how well you actually performed in the sprint race as a whole.

Another big caveat here is that this graph represents all the athlete’s races, so we could be obscuring a confounding variable of changes over time. (I was particularly worried about that with Holly Brooks, but upon checking the raw data, that doesn’t seem to be the case.)

I’m going to start with Petra Majdic, because it’s a great opening into yet another factor that can be at play here. The effect of performing better on somewhat longer sprint courses for her is probably the weakest of the four. One interesting feature is the rather sharp cutoff at around 1.2km. Since Majdic is (was) one of the fields best sprinters, ever, how can we explain the apparent tendency to perform so much worse over shorter distances? Among many possible options, one things that comes to mind is that shorter courses will tend to make races more unpredictable. Being unlucky, in terms of crashes or stumbles, has a much larger effect. So we might expect less consistency from even the best skiers on shorter courses.

Holly Brooks is a somewhat dramatic example, particularly since so many of her results never went past qualification, so one could argue that we’re seeing something more directly reflective of her response to race effort length. On the other hand, our data for her are the most limited. Small sample size, and all that. The other two I’m not terribly familiar with.

On Thursday we’ll look at some folks with trends in the opposite direction…


Is Petter Northug Serious?

That’s an easy one: probably not. I’m referring, of course, to his recent pronouncements about the upcoming season, in which he claims that he will win 7 World Cups, the Tour de Ski overall title, as well as 3 golds at World Championships.

Obviously, given Northug’s history I’m not inclined to take this too seriously. He likes to make waves from time to time, which is why we love him so. But just for fun, let’s delve a bit into just how impressive a season that would be. As always, all the following comparisons will be for all seasons back to 1992 or so.

In that time, a skier has won at least 7 individual World Cup (sprint or distance) races a total of 15 times. Five times by Bjørgen, twice by each of Kowalczyk, Kuitunen and Skari Martinsen, and once each by Di Centa, Vaelbe, Majdic and…..Petter Northug. (In case you’re wondering, this metric is a little unfair to Bjoern Daehlie, who was in his prime at a time when there were somewhat fewer WC races on the schedule, and for much of that time was basically splitting the victories with Smirnov.)

So there’s at least some precedent for Northug’s 7 WC wins claim. Note that he’s the only male skier on that list!

But the real kicker is actually the three WSC golds. In the modern era (i.e. since 1992), who has won at least three golds at a single major championships (Olympics or WSCs)? That has happened a total of five times, by Bjørgen (of course), but then the list gets a little, shall we say, dubious. They rest are: Myllylae in 1999, Vaelbe in 1997, and then both Lazutina and Smirnov in the somewhat infamous 1995 World Championships.

That suggests, of course, that the only person to do both, win 7 individual WC events as well as 3 golds at a major championships in a single season is Bjørgen. (She did not race in the Tour de Ski that year.) And frankly, that season is shaping up to be a bit of an outlier even for her.

So there you have it. If Northug comes through on his promise, I will be the first to doff my cap…but I wouldn’t bet on it.

Stephen’s Climb to the Castle Margin

Liz Stephen destroyed the women’s field this weekend in the annual Climb to the Castle rollerski race. The margin, just over 5 minutes in a race that took the leaders between 40-45 minutes is certainly impressive. But I think that margin doesn’t provide much useful information.

Time trials that are most useful as gauges of performance trends are the ones that have the most stable, repeatable conditions. I believe Climb to the Castle has everyone using identical roller skis (at least that’s my recollection) and that helps. But as noted in the coverage, road and weather conditions can pretty severely impact times. In that light, the fact that Stephen covered the course more than a minute faster than last year in worse conditions is certainly a more reliably good indicator.

But even then, it’s sort of crucial to note how the race dynamics played out. Stephen skied alone basically the whole way this year. Last year, it sounded like she skied alone for over half the race. That will tend to make those efforts more similar to those produced by a interval start race, which are easier to compare, I think. For example, it’s hard to read much into the fact that Sargent skied around 2.5 minutes slower this time around, since once Stephen was off the front it’s easy for “group racing” mentalities to take over common in mass start events that slow the pace.

Even if we ignore all that, consider than Sargent and Diggins were around 12.3% and 11.7% behind Stephen. Looks at their head-to-head results from recent history, it’s hard to believe that Stephen really is that much faster than Sargent and Diggins:

Diggins was actually frequently faster than Stephen last season, and even then it was unusual for the margin between them to be more than 2.5% in either direction. Even Sargent, who had somewhat of a rough season, was almost never more than 10% behind Stephen.

As a data guy, I’d love to see Climb to the Castle run as an interval start race, which would somewhat improve it’s use as a benchmark, but you’d still have a hard time accounting for differences in weather, particularly wind. But obviously, that’s logistically more complicated.

Minor Leagues

OPA Cup races (also known as Alpen Cup) and Scandinavian Cup races have acquired an informal reputation as a sort of “minor league” racing circuit, relative to the World Cup.  One question this leads me to ask is exactly how much movement is there between these two circuits?

To answer this question I took data from skiers who had started in at least one World Cup and at least one OPA or Scandinavian Cup race since the 2004-2005 season.  This yielded 543 men and 352 women.  This is a rather wide net, since I’m including skiers who may have done one WC race in 2005 and then only OPA Cups, or vice versa.

Here is a graph that shows the number of starts of each type for men and women:

Each dot represents a different skier.  The number of starts is the total (distance and sprint) over 6 seasons (04-05 to 09-10) and the points have been plotted with some alpha blending since many are directly on top of each other.  Darker areas correspond to more points being plotted.

As you can see, the overwhelming majority of skiers who have done both types of races have done fewer than 15 of each type.  Much of that racing is spread over 6 seasons.  The skiers who’ve done a ton of WC’s tend not to have done many OPA or Scandinavian Cups, which isn’t terribly surprising.

As we move away from each axis, we get the skiers who’ve come the closest to splitting their time between these two racing circuits.  As you can see, they exist, but not in huge numbers.  Most of the OPA Cup skiers are probably getting their WC starts as part of Nation’s Group starts, rather than being rotated back and forth within or between seasons.

Trends In Race Times: Biathlon

I haven’t posted anything looking at biathlon for a while, so…

Since biathlon has had much more consistent race formats over the years and since we don’t need to split up the data by technique, we should be able to get a clearer picture of any trends on the gun-happy side of things.

The graph below is too small to see.  You’ll have to click through for the full version, which ought to be fairly self-explanatory.

These are the top 10 times in each major race.  We can clearly see that race times have been falling.  In fact, if you look closely you’ll see that times have dropped quite a lot in some cases.

Some other things we can note: the mass start races, true to form, seem a bit slow for the distance, particularly for the women.  It’s so strange that people find it so hard (psychologically) to press the pace in a mass start race…

You can’t really see it in the sprint races, but the rest display a leveling of the time trends followed by an second dip.  The individual races seemed to plateau a bit between 1998-2003 while the mass start races appear to exhibit a similar trend between 2003-2007.  It could just be a fluke, I suppose.  In any case, I can’t think of any explanation for it at all.

Swedish Women By Individual

Following up from last time, we’ll look a little more closely at the individual trends among some of the top Swedish women in distance and sprint events.

First the distance skiers (click through for a larger version):

Not surprisingly, Charlotte Kalla is generally the top performer here. But notice that there’s a bit of a solid drop off after her and Anna Haag. Maria Rydqvist surprised many by coming back from a year off with some very solid results, but then seemed to hit a bit of a plateau last season. Sofia Bleckur took a large jump last season, but the move from 0.5-1 standardized percent behind the median skier to -0.5 to -1 standardized percent behind the median isn’t quite as challenging. The next jump will likely be orders of magnitude harder.

I believe I’ve commented on this before, but Anna Haag’s trend over the past three seasons is a bit worrying. The Swedish women had a very strong year in 2010, but both Kalla and especially Haag seem to have experienced a bit of “regression to the mean”. That makes me wonder whether Haag’s 2010 campaign (and to a certain extent even Kalla’s) was the best we’ll see from her.

As for the sprinters (again, click for full version): Read more

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