The effect of dead weight on top swimming speed

This article seeks the answer to a big question to most of us.  How much of an effect does our weight have on performance?  Should we strive to be muscle bound brutes or purge ourselves to become lean machines?  You need muscles to move through the water, but they are dense and heavy.  What if you had to swim with extra weight (like a barbell or rock strapped to your back for example), knowing that it neither helps in strength or buoyancy, how much slower would you expect to go? 

This question is one that can be quantified in a simple experiment.  The author (Duane Dobko) swam a bunch of 25yard all-out sprints with normal body weight (quantity-4), then acquired some dead weight and swam the same quantity-4 all-out sprints.  The difference in time and weight was used to approximate a time loss per pound of weight.

Practical reasons ruled out the use of a barbell or rock strapped to the chest or back.  Any such device would have to be long, thin and heavy to work.  Otherwise, it would create more resistance on the water and make the results more dependent on drag than weight.  Thus, the method of applying weight in this experiment was… food!!!  In between the first and second set of sprints, the author took a 2-hour break and went to Denny’s Diner to eat the breakfast of a lifetime.  A half dozen eggs, hash browns, grits, pastries and two chocolate shakes, I was ready to rock.  And yes, this setup is as dumb as it sounds.

It may sound funny to add weight in this manner.  But it was effective as it was entertaining.  I managed to gain 3 pounds by the time I got back to the pool (even though I probably ate 4 pounds and got a little sick).  All that weight was tucked away in my stomach, thus having no effect on water drag/resistance and limited effect on my center of gravity.  As it was food and water in my gut, I could assume that it was non-buoyant.  And the food wasn’t in my gut long enough to convert to any muscle.

Disclaimer/warning:  As you might expect, the second set of sprints was extremely painful.  I do not recommend anyone perform a similar exercise.  With hindsight of course being 20/20, I would have come up with a different way to get this done had I known how bad this experiment would hurt.  First of all, pool facilities have to close down if you puke in the water.  Fortunately, I got my business done before I got on deck.  But more importantly, it is hazardous.  Swimming with that much food in the gut made my arms feel like jelly, which could pose a drowning risk for people with limited swimming experience.  Don’t try it yourself – fortunately I have all the data you need!

The results are shown in the charts below.  As expected, swimming with dead weight resulted in slower times that were significant to 95% confidence.  The time difference over 25yards (at a quarter of a second) doesn’t sound like much but really adds up over triathlon swim distances.  For an Olympic distance swim, you can expect to go 28 seconds slower in time for every pound of dead weight you carry.  Thus, if you carry three extra pounds, a 25 minute swim split could have been 23 and half minutes.  At Iron distance, you will go almost a minute and a half slower per pound.  This is a significant chunk of time for any competitor, beginner or advanced.

It is important to note that these results apply to dead weight only.  This can be anything that is not buoyant (like bone, muscle, your watch, your racing uniform, etc).  But the results do not readily apply to fat or a wetsuit.  As fat and neoprene possess some buoyancy, the time loss associated with weight gain is partially offset by the increase in flotation.  How much of an effect this can have cannot be determined from the data in this experiment.

I hope you can use the results of this article to tailor your swimming regimen to optimal performance.  Many athletes have pondered whether it is better to gain muscle weight versus stay lean and light.  The results of this experiment suggest that an extra pound of muscle weight must make you about 0.7% faster just to break even in your swim time.   If that added muscle gives you less gain, it may slow you down.  A pound of muscle can do a lot of great things, but only if it is muscle that you will actually use while swimming.