Bodyweight fluctuations and swim speed

evmoevmo San FranciscoAdmin
edited April 2012 in General Discussion
I've been thinking recently about the effect of gaining/losing weight on swim speed. Last year I gained ~15 lbs in anticipation of cold water in the Catalina Channel. It ended up not being necessary, but hey, at least I was prepared.

However (as is surprisingly easy to do), I sort of "forgot" to lose the channel weight :)

Anyway, the reason it's been on my mind is that I'm doing a couple pool meets this spring, and am finding the extra weight somewhat inconvenient! This led me to wonder how much, exactly, it's slowing me down. My intuitive sense, based on my own pace times in training, is that it's somewhere around 2-3 seconds per 100m, per 10 pounds (all else being equal, which as @KarenT will point out, is almost never the case).

This extrapolates to around 10-15 minutes for a channel swim, which seems relatively minor. On the other hand, 30-45 seconds in a pool mile actually seems pretty significant to me.

I'm wondering if anyone has thoughts on this, or "data" from their own experience to enrich our understanding?

As swimmers we don't have to think about this as much as our land-based fellow athletes, but I find it an interesting issue nonetheless.


  • Thinking about this some more, and setting any other reservations aside, perhaps it makes more sense to talk about % of body weight increases / loss, rather than pounds....? 10 pounds added to a 200 pound individual has a very different embodied effect than on a 120 pound individual...
  • evmoevmo San FranciscoAdmin
    I agree, and along the same lines -- Perhaps it makes more sense to think of changes in swim speed in % terms, as well.

    2-3 seconds/100m is much different to a 1:20/100m swimmer than to a 2:00/100m swimmer.
  • I wonder if weight:speed would turn out to be a direct proportion or somewhat exponential over a range of weights.
  • WaterGirlWaterGirl Charter Member
    I have to assume that weight gain would affect men and women differently. Men tend to gain weight in the belly, whereas a woman's extra weight would be distributed more evenly throughout the body.

    The male weight-gain pattern seems less hydrodynamic than the female. But the added buoyancy would be a greater help to a man than a woman.
  • mmeadmmead Charter Member
    I'll never gain weight for a marathon swim again. I gained 20lbs for the English Channel and unfortunately for me, I'm not an "even-gainer." The only thing that has made an impact on my cold-tolerance was repeated exposure to cold and keeping myself in good enough shape to hold a fast pace.
  • ChickenOSeaChickenOSea Charter Member
    No even weight gain here! It ALL goes on my thighs and bum, which causes a huge diameter to be pulled through the water by my short little arms. Yuk. I'm trying to lose weight to see if I get back to the same speed as I was before I gained it all. I guess it's hard to compare though, as there are so many other factors involved.
  • AnneAnne Charter Member
    edited April 2012
    From my observations, few obstacles slow a swimmer down more than being cold. The best thing you can do to prepare is lots of cold water acclimation training, although if you are thin gaining a few pounds for a one-way swim is like buying insurance and will help you to be more comfortable. For multi-leg swims you'll need more of course. "Lots of ice cream, late at night" as one of my esteemed friends likes to say. I don't care how mentally tough you are, your physiology will take over at a certain point and there isn't much you can do about it once that starts. I've seen it - and been there myself - and it's not pretty.

    Question: what about the buoyancy of adipose tissue (fat)? Wouldn't that factor in? Swimmer floats higher, less resistance?

    Maybe we just don't want to be fat.
  • My increased weight has made me a better distance swimmer - I'm stronger, have more endurance. I gained some middle age spread about 8 years ago and it has definitely helped my OWS. The down side is that I chafe more though.
  • bobswimsbobswims Charter Member
    When I was training for a half Ironman triathlon I got down to 168 lb (very light for me). I raced in 60° water for a bit under 2 hours and went through a bit of a hard time after I got out. This summer I did 13 hours at 65° (60° for the last couple of miles) at 200 lb and never felt the cold, either in or out of the water. Surprisingly I was more fit for the first swim. I think the fat helped, but I may have done just as well at 190 -195.
  • ForeverSwimForeverSwim Charter Member
    The extra weight (in my opinion) is added protection for "inland" channel swimmers who do not have access to cold water during the late spring/summer months. When I am preparing for a sub-60 degree channel, and only have 85+ degree water to train in, I aire on the side of caution and add the LBs..

    For the English Channel (at 57-degrees) I did not get cold at all, however during the Catalina swim last summer, I did get cold(er) toward the end (could this possibly be because of less body fat than I had the summer prior in England?). If one has access to 55-60-degree ocean water for the majority of the year, then I do not believe adding as much weight is necessary (although I have no basis for this statement, so I will leave that up to the "ocean side" swimmers).

    At 225lbs, I like to think of myself as a tug-boat steaming along... :) Pittsburgh, Pennsylvania U.S.A.

  • evmoevmo San FranciscoAdmin
    Just to be clear: I'm definitely not disputing the benefits of a little bioprene for cold-water marathon swimming. I'm just wondering what the "cost" is in terms of swim speed. And, at least for me, there is a cost; I know this from my pool times.

    Runners have a rule of thumb: 2 seconds per mile (slower), per pound (gained). I'm curious if there's something similar for swimming (with the caveat that it's probably a more complicated equation than for running).

    I'm most intrigued by the comments of @WaterGirl and @Anne, that:
    - The typical male weight-gain pattern is less hydrodynamic than the typical female weight-gain pattern.
    - Being cold makes you slower - and therefore, to the extent that weight-gain makes you less-cold, the usual cost in swim speed may be somewhat counteracted in cold water.

    Very interesting stuff!
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