How much does body weight effect swimming speed?

There's certainly alot of good arguments here, and it is a good discussion. I don't know if we'll ever come up with anything concrete or a good way of measuring but it's a good discussion nonetheless. I’m not sure that there’s any way to really measure how losing weight will or will not affect time. In my case, I’ve dropped weight and time over the last year. I’m around 6’1”. I swam at the New England Yards championship in both 2009 and 2010, though in 2009 I was 25 or so pounds heavier (I’m around 200 now). I was about two and a half seconds faster in the 100 (this year 58 high) and about 15 seconds faster in the 500 (5:34) in 2010. I think that the weight loss contributed to those declines, but I’m not sure how much. The swims were comparable—same meet, same pool, rested for both, wore a bodysuit at each (though a better one in 2010), etc. However, I can think of at least two other reasons that would explain the time drops aside from weight loss. I worked a lot on technique in the intervening year. Also, I only started racing in the pool in 2008, and it seems to me that more racing experience has helped me mentally prepare better. There may also be other reasons--and those two alone could explain all of the time drops in themselves. That said, this is an interesting topic. And as long as we are coming up with theories about how weight loss can or cannot affect speed, I think that drag is only part of the equation. I have two more thoughts, though those ideas may be more related to distance swimming as opposed to sprinting. First, as others have said, I noticed with the weight loss that I have more energy. I’m able to train harder and more than I did before—and, intuitively at least, it seems like that should indirectly translate into faster times, though maybe more for a distance event than a sprint. Second, there’s a lot of talk these days about intra-abdominal fat. I understand it to be fat on the inside of the abdominal muscles (as opposed to the beer belly fat on the outside). Others may have a better understanding of what it is and how it works, but I thought I'd throw out a possible theory about it. I wonder, but do not know, if that type of fat can intrude upon the space for expanding lungs, etc. and lead to performance declines. If it does (or if that fat has a different but equally detrimental type of metabolic cost), then losing that particular type of fat could lead to speed gains irrespective of the drag issues.

If you believe that being large makes you faster, consider gaining weight and see what happens to your time. See you at the drive-thru! I've never postulated that being heavy makes one faster. And I HAVE gained weight and gotten slower. What I'm trying to figure out though... is the speed loss i'm noticing related more to lack of training or the weight itself? Certainly weight change can be attributed to training or lack of it... and speed would be effected the same way in regards to training. I don't think anyone is arguing the effects of training on speed and weight. But how swimming speed, specifically sprints in my case, is effected by just weight itself? That's what I'm trying to figure out. There's certainly alot of good arguments here, and it is a good discussion. I don't know if we'll ever come up with anything concrete or a good way of measuring but it's a good discussion nonetheless.

Dolphins aren't exactly skinny, even Cesar has some fat around his waist. Fast aquatic animals that are skinny are usually smaller, like the barracuda. Maybe world class swimmers aren't round not as a requirement to go fast, but due to the nutritional demands of training and the age of peak performance where we don't put on pounds as fast. Anyway, I have very low body fat but I can't even get below 30 seconds in the LCM 50, perhaps I should try another stroke like fly.

Hi Michael, (qbrain) The power needed to overcome drag is proportional to the cube of velocity so the velocity drop off with a larger cross section is not as large as if you just multiply the velocity by the ratio of areas. I think it works out that with the same power the larger swimmer would finish in about 24 sec versus the 21.7 for the slimmer swimmer. Of course I'm notoriously bad at simple arithmetic so best to double check. v(large) ^3 = v(slim) ^3 / ratio_of_areas. Going purely on memory I believe surface drag is relatively insignificant, despite the prominence with which suit manufacturers advertise reductions thereof.

Hi Michael, (qbrain) The power needed to overcome drag is proportional to the cube of velocity so the velocity drop off with a larger cross section is not as large as if you just multiply the velocity by the ratio of areas. I think it works out that with the same power the larger swimmer would finish in about 24 sec versus the 21.7 for the slimmer swimmer. Of course I'm notoriously bad at simple arithmetic so best to double check. v(large) ^3 = v(slim) ^3 / ratio_of_areas. Going purely on memory I believe surface drag is relatively insignificant, despite the prominence with which suit manufacturers advertise reductions thereof. Sorry, I took your proportional comment incorrectly and didn't think through my 40%. I came up with 24.3s so I think you did the math right, and I came up with the same formula that you did. This still bothers me. fmracing should be no faster than 24.3s, and my area estimates were conservative, since fmracing is built more like a circle now and probably more like a rectangle at 200lbs. This would increase the ratio_of_areas and make the estimated fat time even slower. Fat Man, I am probably not the first to tell you this, but you are too fast. Something is missing. I fully expect an idealized model to predict a Master swimmer to be faster than they actually are based on their college times, unless the Master's swimmer is in similar shape they were in during college. The physics of drag does not account for age and decreased training. I am trying to use less math in my posts.

The cross sectional area increases from weight gain I think are overestimated. The 200lb swimmer depending on height has their largest cross sectional area made up of shoulders, chest and head. The 200lb swimmer's chest is probably around 42-46 inches. If the 270 pound swimming has a 42" waist, the waist is still less then the chest size. The weight gain may however also increase chest and shoulder size. The stomach will also probably stick out a bit so it will add some cross sectional area. The drag from increased surface area will also not be too high. I think surface drag is about 10%. The main drag is from the cross sectional area and the wake drag which is what creates waves.

the estimated fat time Awesome phrase! Haha. :applaud: Fat Man, I am probably not the first to tell you this, but you are too fast. Haha. I have been called world's fastest fat man but I never believed there wasn't someone fatter that could school me ;) :cane: Something is missing. I fully expect an idealized model to predict a Master swimmer to be faster than they actually are based on their college times, unless the Master's swimmer is in similar shape they were in during college. The physics of drag does not account for age and decreased training. I fully assume I am in worse shape now than I was then. Certainly the weight is a big indicator, but I also only train 2-3 times a week at 2300m, and I don't lift weights anymore. If your calcs are really correct, then it'd imply the weight really is substantial when it comes to speed ? If it's really true what your numbers are... then I'm salivating at the thought of losing the rest of the weight and going PB times 12 years later. Seems too good to be true though, as you said something has to be missing. ^^Or maybe I just sucked at sprinting at my "peak"?

It concludes that the worst thing, in the terms of a physical capability, for a man is to have fat on his belly (at the front, not the sides). Welp - time to go for another run! :bolt:

Dolphins aren't exactly skinny, even Cesar has some fat around his waist. Fast aquatic animals that are skinny are usually smaller, like the barracuda. Maybe world class swimmers aren't round not as a requirement to go fast, but due to the nutritional demands of training and the age of peak performance where we don't put on pounds as fast. This research topic is which body related factor affects our physical capabilities the most while we are aging. Thus, it is not appropriate to compere 60 y.o. swimmer with dolphin, or even Cesar, and expect to get practical advice how to slow down aging.

I fully assume I am in worse shape now than I was then. Certainly the weight is a big indicator, but I also only train 2-3 times a week at 2300m, and I don't lift weights anymore. If your calcs are really correct, then it'd imply the weight really is substantial when it comes to speed ? If it's really true what your numbers are... then I'm salivating at the thought of losing the rest of the weight and going PB times 12 years later. Seems too good to be true though, as you said something has to be missing. The math is right, the science is wrong. There is something important missing. There is not a skinny guy waiting inside you to go sub 21 on weight loss alone, sorry :)