Bodyweight fluctuations and swim speed

evmoevmo SydneyAdmin
edited February 2018 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.


  • KarenTKarenT Charter Member
    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 SydneyAdmin
    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 Scottsdale, AZCharter 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 La Jolla CA USACharter 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.
  • Kate_AlexanderKate_Alexander Spring Lake, MichiganSenior Member
    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 Santa Barbara CACharter 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 Pittsburgh, PennsylvaniaCharter 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 SydneyAdmin
    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!
  • ttriventtriven Senior Member

    I have noticed something similar in the pool, however, I am not sure it would put 15 minutes on your channel swim time, because we float more in seawater. At least that's what I am telling myself.

  • HollyTHollyT Member

    Last year I lost about 10 pounds very rapidly at the end of a marathon (running) training cycle. My pool time trials showed me getting progressively slower and I felt like I was sinking in the pool. We aren't sure though if it was that I was slower because I was less buoyant, or if I was just getting tired at the end of the training cycle.... Kinda of hard to figure that one out.

  • andissandiss Senior Member

    I met Stephen Redmond last weekend down Lough Hyne - he has lost 5stone - huge difference - but I still thinks he pretty much swims at the same speed as before

    He found it funny I was shaking after my swim - it was roughly 12C - I'm 5'11 and roughly 178lb - not really carrying any excess fat but at the same time I'm not triathlon skinny...

  • lakespraylakespray Senior Member

    I think weight versus speed is most notable on pool swimming times and shorter open water races, 10K or under. My weight and training regimens changes with the swimming goals I had. I usually try to lose weight if my goals are something like a 5K USMS championship, a La Jolla Rough water etc. I train for those much like I'd train for the pool 1500 meters which means allot of strong and tight intervals etc. versus long endurance swims of last years MIMS. In my case when it comes to a pool standard of 10 x 100 meters I'm about 5% faster or more in both pace and interval when I'm 20 pounds lighter then my cold marathon swim body. Is it the chicken or the egg, does swimming long slow twitch swims kill your speed or is the weight? I think it's both, most Masters swimmers I've coached and known over the years are generally faster at lower body fat percentages.

  • ssthomasssthomas DenverCharter Mem​ber

    I definitely think that weight makes a difference in speed.

    When I was training for Catalina in 2010, I was the lightest I’d been since high school, at about 145. That was also the fastest I’ve been since college. I recall doing a 15k pool swim and crushing the last 1000, holding about 1:20s, long course.

    I gradually gained weight for the English Channel in 2012 and did notice a slowing of speed between 2010 and 2012. I had a hard time losing the EC weight, and at some point quit trying. In 2013 and 2014, I was training for very long and cold swims, so the weight gain didn’t bother me too terribly much. I did notice a drop in my pool speed. However, it’s hard to determine if my speed slowed down because of the weight gain OR because my focus shifted from pool training to very long open water training swims. I firmly believe that if you want to swim fast, you have to do interval work in the pool- but that’s another conversation.

    I will say, that I have been very focused this spring on losing weight and regaining speed. I’ve already noticed the difference in my pool training in the last two weeks, as my weight has dropped and my time in the pool has increased. My pool intervals are already faster now than they were in 2013 and 2014, by about a few seconds/100 and I’ve dropped about 10 pounds in the last 2 months. I’m still heavier than in 2010 (170 at last weigh-in) and my speed isn’t where it was in 2010, either. On the 15k pool swim I did this past Sunday, I was consistently holding 1:28s for 100 meters, long course, increasing speed a little more toward the end. (Side note, it is early in my training, so my fitness is also not where it was during the 15k in 2010, mentioned above. It’s not a perfect comparison, but something to start from.)

    I’ll keep conducting the experiment to see what happens to my weight and intervals as I try to drop more weight and gain more speed over the summer. (Though, somewhere, someone might yell at me for dropping weight before attempting Loch Ness in August…but hey, I’m going to try out the theory that good cold water training and sprinting for 12 hours will work out ok for me.)

  • emkhowleyemkhowley Boston, MACharter Member

    I'm in much the same boat, er, lake, as @ssthomas with regard to the weight/speed thing and current training goal. All told, I've lost close to 50 pounds from my height when I attempted the North Channel in 2013. (I wasn't trying to lose weight, I just had some changes in my life that amounted to a big drop over the past year or so.) In any event, my pool times are significantly faster than they were when I was heavier-- 5 to 10 seconds per 100 depending on the day. (And climbing stairs or going for a little run no longer makes me want to cry.)

    I've moved up to a faster lane during pool workouts, and I can hang with some of the faster kids I haven't been able to keep up with since 2007, when the weight first started creeping on (again, I hadn't intended to gain the weight in the first place, it just sort of happened.) I'm now within about 10 pounds of where I was when I graduated from college and swimming faster than I have since I was a sophomore in college (my fastest year).

    I do worry about the big drop in advance of a cold swim like Loch Ness this summer, but I am banking on three things to be in my favor: 1) Experience-- muscle and body memory has to kick in sometime, right? I mean, this ain't my first cold rodeo, so that has to count for something. 2) Peer pressure-- people know about this swim and knowing that Craig and Sarah are still in there is going to push me to try to hang with them; and 3) Adrenaline-- after I sailed through my ice mile in 2012, I learned never to underestimate the power of adrenaline. Oh and 4) WARM FEEDS!

    Wish me luck. And for the record, I just had 2 beers AND a generous bowl of ice cream after dinner. :-)


    Stop me if you've heard this one...
    A grasshopper walks into a bar...

  • phodgeszohophodgeszoho UKSenior Member

    Over the winter and summer seasons both my body mass and swim times seem to fluctuate but unfortunately there doesn't seem to be any correlation between the two. I just seem to be pretty random on both... :-/

  • TheoTheo Oxnard, CAMember

    In the pool weight for me is a huge factor. A couple of years ago when I was 30 lbs lighter I was averaging 5 seconds per hundred faster and had greater endurance. In saltwater it has been less notable. But I have always had a big difference in the ocean vs pool. When I joined the masters team several of the swimmers were expecting much more out of me in the pool because they had only swam open water with me.

    Bottom line added weight in the pool no bueno. In the ocean not quite as noticeable. Won't be swimming any pool events unless I find the willpower to lose at least 60 lbs.

  • smithsmith Huntsville, AlabamaSenior Member

    Great topic.

    As an older swimmer (51), I've experimented a lot with weight. I don't lift weights, but do a lot of core work and spend a lot of time on the bike.Being that folks my age naturally lose muscle over time, I believe weight can be cut pretty quickly as long as you're not too sedentary and adhere to a strict diet. As we know, that can be a significant challenge.

    Started swimming again in late 2010 after about a 25 year break. Weight was around 195 at that time, but had been heavier for much of the 25 year break.

    Swimming actually made me hungry. Lol. Weight for first 5k in 2011 was about 200. Water temp about 76-77. No issues. However, instinctively knew I could improve.

    Swam at 188 - 194 in 2012. Felt strong, and stamina was good. Able to train in 60 - 62 degree water, but only if air temps were above around 55 degrees. If it was a cold morning at or around 40 degrees, I was out of my element.

    Dropped weight in 2013. Repeats much faster at 178 - 182 pounds. Not as physically strong, but better stamina. No cold water swimming. Did come down to 172 before one swim. Repeats were a bit faster, but no resilience. Actually cramped up in an open water race at that weight.

    Trained well at 180 - 185 pounds in 2014. At one point, I was around 192-194 during that winter, and felt much worse than I did in 2012.

    Around 190 right now, mostly due to being more lax about my diet. Don't feel that great in the water. On the plus side, I'm fairly adept at juking my metabolism, and don't foresee any issues hitting 182 by the end of the month. Not planning any OWS events until August.

    In sum, cold(ish) water swims should be around 188 pounds, and I should probably be around 178-182 if I want to swim well in warm water.


    Keep moving forward.

  • helengheleng Hertfordshire, EnglandMember
    edited June 2015

    I have done 2 swims over 30km and on each occasion I gained 10% weight (138lbs to 152lbs approx). It turned out not to be necessary for Catalina last year due to the abnormally warm waters in October but I wasn't taking any chances! After 5 years of open water swimming I have noticed the extra 10% weight makes a huge difference to my cold tolerance, especially for early season training in Dover.

    It is very difficult to tell if the weight slows me down, because whilst I am gaining the weight I am also increasing the intensity of my training so the 2 probably counteract one another. I normally increase my weight over a relatively short period of time and I presume most of it initially goes on as fat and doesn't have a chance to be converted to muscle so is more likely to slow me down and put extra strain on muscles which are already in intensive training. I have had a lot of shoulder issues over the last year and I believe the weight fluctuations may have been a contributing factor.
    It is probably better to keep the weight on or gain gradually so that the muscles can adapt to pulling the extra weight. Furthermore, keeping the weight on I guess means that the extra weight can be converted to muscle and therefore will allow an increase in speed (however, I'm not sure muscle is quite as effective for insulation as fat). The effect on speed is surely dependent on whether the extra weight is muscle (by which I mean useful muscles that help propel you through the water), or whether it is fat (for insulation purposes).

    Anyway, I have grown tired of weight fluctuations for cold swims, so have chosen a warm swim this year and will be keeping the weight off. I am hoping that I will see a slight improvement in speed as I increase my training intensity unlike in previous years where the extra weight may have slowed me down :-)

  • SuirThingSuirThing Carrick-on-Suir, IrelandMember

    Doing a lot of pool sprinting lately and the weight has come down Have even been to a couple of Masters galas (US: "meets"). Down 7kg myself, I'd have to go along with the 3 secs/100m/10lbs lost suggestion.

    Would any of you speedsters put a number on time gained from a full body shave? Saw a stat recently from a wind tunnel study on time saved by a cyclist shaving his legs and it was a BIG difference

    I tried to convince myself, but, orange flavour electrolyte, mixed with hot chocolate,
    tastes nothing like Terry's Chocolate Orange ....

  • NoelFigartNoelFigart Lebanon, NHSenior Member
    edited February 2016

    I'm heavier than I was a year ago. I'm also about 13 sec/100 faster than I was a year ago. (That's general cruising speed. My PBs are much more dramatic, but I think they shouldn't count as it's cruising speed that's important over long distance)

    I'm probably not great to go on, though. A year ago, I'd only been serious about trying to improve my speed and technique for about six months after a two year hiatus from any serious exercise.

  • KarenTKarenT Charter Member

    @SuirThing - might it not also be that 'doing a lot of pool sprinting' has improved your sprinting?

  • JSwimJSwim western Maryland, USSenior Member

    "The Effect of Varying Body Composition on Swimming Performance" reports a study with 10 swimmers, where artificial fat was "added" and many 50 yard freestyle times taken. The authors are very cautious with their conclusions, and discuss why the relationship between percentage body fat and swimming speed is complex. There is also a good discussion of the types of drag and the References section is interesting.

    The raw results were that 50 yard free times (~27 secs) were about 0.8 seconds slower with the addition of about 1.5 kg (~3.25 lbs) of "fat". Extrapolating and rounding, that's roughly 1 second slower per 25 yards per 10 pounds. That extrapolating is all my doing, not in the paper.

    Very much, Your Mileage May Vary, but useful anyway, I think.

    "Swimmers - Is Fatter Faster?" is a general summary.

    Life begins at the end of your comfort zone. --Neale Donald Walsch

  • FlowSwimmersFlowSwimmers Polson, MontanaMember

    I'm really interested in this thread, and next week, I have my first actual "race" since losing 25lbs. over the last year -- 237 to 212.

    I've always said to myself that the easiest way for me swim faster would be to lose some weight, and next week, I'll test my own theory. My training regimen has been pretty much the same, so it will be interesting to see how the lighter weight impacts my times.

    On a related note, whenever I am preparing for a cold water swim, there's a trigger in my brain telling me to eat more, and I don't think I'm consciously aware of it.

  • SuirThingSuirThing Carrick-on-Suir, IrelandMember
    edited February 2016

    @KarenT the improvement in speed I refer to is not confined to improving my sprint times, but rather my average speed over an hour for example. My 100m time hasn't improved by 3 secs/10lbs lost. It does hold true from 400m up to 4km. Haven't tested over further.


    I tried to convince myself, but, orange flavour electrolyte, mixed with hot chocolate,
    tastes nothing like Terry's Chocolate Orange ....

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