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XC skiing and arthritis

April 18th, 2011

To be perfectly honest, I wasn’t thrilled to see the results of this study (tweeted by Amby Burfoot). But data is data*, and if you report the good news you can’t ignore the bad. Swedish researchers did a very cool analysis of 54,000 men and women who competed in the famous 90 km Vasaloppet classic-style nordic ski race between 1989 and 1998 (full text available here). What’s fascinating is that Sweden keeps meticulous records of all its citizens, including all the in-patient health care they receive, linked to a 10-digit identification number. So the researchers were able to link the names and finishing times of all the racers with their health records, census data (to check confounders like education, occupation and income), death records and emigration records.

The basic question they looked at was: does exercise (as represented by the number of times subjects raced the Vasaloppet in the 10-year window, and their fastest finish) correlate with severe osteoarthritis later in life (as indicated with having a knee or hip replacement due to arthritis). The answer, unfortunately, was yes. For example, those who completed five or more races and had a fast finish time were 2.73 times more likely to need a joint replacement in the following ~10 years than those who participated only once and had a slow finish time.

The results contrast with a string of recent studies that found that, if anything, longtime runners are less likely to develop arthritis than non-runners. So there are a few questions here. Does the skiing motion have some unique effects on joints, causing more stress and cartilage damage? Or is it more a question of degree: “moderate” exercise is good for the joints, but 90 km ski races (which took between four and 13 hours to finish) are a bit too extreme? I don’t know, but I suspect the latter is a factor.

One point worth noting. Compared to similar studies of the general population, the skiers as a group had exactly the same risk for knee replacement, and a slightly higher risk of hip replacement. That suggests that, while the elite athletes at the front of the pack were worse off than the general population, the “casual” exercisers toward the back of the pack were in fact better off than the general population (though “casual” isn’t really the right term for someone doing a 90 km ski race).

And a last point: the same group has made several other studies of the characteristics of Vasaloppet finishers. Even if their knees get creaky, they do live longer than their sedentary peers; and the more races they do, the longer they live. So that’s something, I guess!

[* I know, "data" is supposed to be plural. Hopefully people will overlook this transgression... :) ]

  1. April 19th, 2011 at 14:33 | #1

    How is the coldness influencing this? I moved to Sweden (and yes, now also registered for the Vasaloppet next march)and notice more sore joints after XC skiing and even running in the winter (but much less). My partner – 10 times Vasaloppet finisher, most below 5 hours)has the same problem and we had lots of discussions about it. An extra windcover helps, even if the temp is quite high (and temperaturewise not needed). That’s why we assume it is the coldness or the wind (or combi). Maybe even the lack of a good cooling down. In -12C and winds you are cooled down, the moment you stop skiing. In -24C i just want to run to a warm shower.

    An other theory we have, if the relativ static movement in cold temp. Vasaloppet has lots of double poling and double with a kick. A lot is about timing and the upperbody that is working. However, the less fast people use lots of diagnal.

    Interesting though!
    greetings

  2. AG
    April 19th, 2011 at 16:28 | #2

    Could it be that the thing that many thought was actually bad for you is actually good for you: the impact of running?

    I know cyclists are in danger of bone loss because of lack of impact. This is very interesting indeed.

  1. April 18th, 2011 at 17:34 | #1
  2. September 3rd, 2011 at 02:54 | #2