Fat vs. Fast

There’s an old saying about cold-water marathon swimming:

Either be fat, or be fast.

Is it oversimplified? Probably. Crass? Definitely. But there’s a kernel of truth worth examining. Thin swimmers have made it across the English Channel, but they’re usually fast. Slow swimmers have made it across the Channel, but they’re usually… carrying a healthy layer of bioprene.

The common factor: Core temperature must be preserved. Either generate heat, or retain it. Fast swimmers are good at generating heat. Fat swimmers are good at retaining it.

In the English Channel (from what I gather), it’s considered prudent for non-overweight swimmers to put on some weight, even if they’re “fast.” A Channel attempt is expensive and, unless your name is Petar Stoychev, just getting across is the main priority. Bioprene increases the probability of success.

But at what cost? How much does the extra weight slow you down? Swimming is a gravity-less activity, so obviously it matters less than in running or uphill cycling. Further, the flotational benefits of fat may improve your body position in the water.

In running, the rule of thumb is 2 seconds (faster) per mile per pound (lost). Is there a similar rule of thumb for swimming?

Out of curiosity, I asked Coach AB to estimate the benefit of losing 10 pounds of body fat on threshold pace per 100m (assuming stable fitness & muscle mass). He said 2-3 seconds per 100m. Some quick conversions: 32-48 seconds per mile, 10-16 minutes per 20-mile channel swim. Or, for an apples-to-apples comparison with running: 3.2-4.8 seconds per mile, per pound.

And actually… that accords fairly well with my own experience. I do a lot of threshold (a.k.a. CSS) training – so I’m intimately familiar with my basic pace per 100m. Also, my weight has fluctuated a bit in the past couple years – giving me some data to draw on.

Can we do better than a rule of thumb? Scientists being scientists, it turns out someone has actually studied this question. In a paper published in the Journal of Strength and Conditioning Research, Ilka Lowensteyn and two colleagues artificially varied the body fat of competitive swimmers by fitting them with weighted latex pads under a spandex triathlon suit. The swimmers were timed at 50-yard sprints at various weights.

Lowensteyn et al. estimated the swimmers were slowed by 0.2 seconds per 50 yards, per pound. That’s 4 seconds per 100, per 10 pounds – not far off Coach AB’s estimate. And it makes sense there would be a larger effect in a sprint (compared to threshold pace), because in water, drag increases exponentially with speed.

Bottom line: Let’s say you gain 20 pounds for your English Channel attempt. You might be looking at about an extra half-hour in the water. Given the thermal-protective benefits of those 20 pounds, though, it seems like a small price to pay.

A business idea: Super Swedes

These are swedish goggles:

swedish goggles

Swedes are only goggle I’ve worn since 1992, and are among the most iconic swim gear ever. Their sleek, minimalist esthetic transcends both time and nationality. Their simple construction renders them both disposable and indestructible. Here’s an interesting history of swedes (the goggles, not the people) from Malmsten AB.

So popular are swedes among competitive swimmers that Speedo was forced to offer Speedo-branded swedes (with original Malmsten lenses, naturally) so their sponsored athletes could wear swedes at the Olympics without being in breach of contract!

Swedes’ functional minimalism cuts both ways, though. They’re cheap goggles. The lenses scratch easily. The latex straps rarely last through more than a month of regular chlorine exposure (I opt for an after-market bungee strap).

On the other end of the spectrum, there’s this:

blueseventy carbon fiber goggles
Blueseventy carbonRZR goggles

The ultimate in superfluous luxury. Carbon-fiber frames? Anti-scratch polycarbonate lenses? It can be yours for $100 – same price, incidentally, as 25 pairs of swedes. There’s an appealing sort of geek cachet to goggles made from the same material as an airplane fuselage. I’d never buy them, though. I can’t stand rubber gaskets.

But what about souped-up swedish goggles? High-quality anti-scratch lenses; chlorine-resistant straps; a nice carrying case? I might actually pay up for something like that.


Super-Swedes. It just might be the best idea since the Jump to Conclusions Mat.

Watch and Learn

Chris Derks is a pretty OK swimmer — course-record holder and four-time winner of the Tampa Bay Marathon Swim, 2004 MIMS champion, competitor in numerous pro races, and owner of an 8:32 English Channel crossing in 2001.

Yesterday Chris posted a video of his English Channel swim to the Marathon Swimmers Forum. It’s a quirky video – 30 minutes long, with random cuts to other races, and ending in the middle of a conversation (apparently Chris plans to upload the rest separately) – but I enjoyed it quite a lot. Chris is one of the best in the business, and it’s a rare treat to see him in action. Also, I dig his taste in music.

Check it out:

A few of my favorite parts:

  • 0:35 – Cool postcard shot of the marathon swimmer and… is that a battleship?!
  • 0:50-3:37 – Interview with Chris. Background & motivations. “I still want to race against kids who are half my age, and beat them…beat them hard.”
  • 3:38-5:47 – Nearly indecipherable interview with his coach. Chris is training in the end lane (a.k.a. the traditional “animal lane” for old-school distance swimmers).
  • 3:53-5:08 – That was a 1:15 LCM split!
  • 6:16 – In Dover. Spectacular usage of The Who’s “Eminence Front”
  • 8:03 – The pre-Maxim era?
  • 8:47 – “On the morning of the swim, the weather was good, and the water was glass.”
  • 10:20 – Chris agrees with me that running into the water is the best way to begin a channel swim.
  • 10:55 – “Mötley Crüe’s ‘Kick Start My Heart’ provided the necessary adrenaline to keep Chris psyched for a long day ahead.”
  • 13:00 – Master class on feeding from a boat. The gold standard.
  • 18:19 – “Give me fuel, give me fire, give me that which I desire!” Great channel song.
  • 19:57 – How to feed from a kayak in less than 4 seconds. Watch and learn, people! (From the Tampa Bay Marathon Swim.)
  • 21:53 – Chris Greene Lake cable swim. Wow, he’s a lot faster than those Masters swimmers.
  • 22:40 – Meanwhile, back in the Channel…

Beauty is in the Eye of the Beholder

Besides Chris’ spectacular feeding technique, I also want to briefly discuss his stroke. There’s some good multi-angle footage from about 15:22 to 15:45, going into and out of a feed.

It’s not a symmetrical stroke. He breathes unilaterally to the right; he rotates slightly more in this direction, resulting in a slight swinging motion on his left (non-breathing) arm; he splashes a bit on his hand entry; his kick is a sort of raggedy four-beat; his tempo a metronomic 67 strokes per minute.

It’s not a pretty, dainty stroke. But make no mistake: It’s a devastatingly effective stroke for open water and marathon distances. A powerful stroke — a rhythmic stroke. As far as I’m concerned, it’s a thing of beauty.

Some schools of swim technique aim for grace, symmetry, smoothness, and lack of splashing. And I get why some people value these things – especially beginners. But they have little to do with speed or endurance – and those are the things I value.

I’m not saying you should imitate Chris’ stroke. Chris’ stroke is precisely adapted to his own body, his own strengths – even his own personality. Chris Derks swims like Chris Derks. Sun Yang swims like Sun Yang. Janet Evans swims like Janet Evans. Your mileage may vary.

For what it’s worth, I swim quite a lot like Chris. Check it out. Unilateral breathing to the right; arm-swing on the left; raggedy 4-beat kick. It’s uncanny, actually.

Announcement: The Marathon Swimmers Forum

Donal Buckley and I are pleased to announce a new online community: marathonswimmers.org.

marathon swimmers forum

After a brief “quiet launch,” the forum already counts some of the most accomplished and knowledgeable marathon swimmers on the planet among its members. Whether you’re a current marathon swimmer, an aspiring one, a retired one – or just curious – we invite you to join their ranks.

Ask questions (there are no dumb ones). Discuss the latest exploits – from Dover, Manhattan, L.A., and Hawaii… to Perth, Wellington, Tarifa, and the Sea of Japan. Announce your friends’ swims and cheer them on.


2012 will, in all likelihood, be the most historic, exciting year in the history of marathon swimming. Follow it on The Marathon Swimmers Forum.

Freshwater Swimmer… in print!

When I cracked open the latest (February/March) issue of H2open Magazine a few days ago, I did a bit of a double-take when I got to page 15:

h2open magazine, page 15

My humble, minimally-marketed, emphatically anti-populist marathon swimming blog is one of H2Open’s “favourite” OWS websites! Many thanks to Simon Griffiths and his team for this recognition. I’m truly hono(u)red.

Here’s a zoomed-in view:

Freshwater Swimmer in H2open magazine

And for good measure, here’s the front cover of the magazine.

h2open magazine

If you’re not already subscribed to this excellent publication, I urge you to get on that – stat.


Water temperature in the Catalina Channel

There are 14 years of publicly available data on the surface water temperature in the Catalina (a.k.a. San Pedro) Channel – via NOAA and CDIP. Unfortunately, that’s all it is – data. No summary statistics, no long-term charts – nothing particularly useful if you’re just looking for a simple, big-picture view of trends and cycles in sea temperature (perhaps to inform your upcoming swim across the channel).

So I decided to make one myself:

Catalina Channel water temperature, 1998-2012

NOAA buoys take readings every 30 minutes. Over 14 years, that works out to almost 239,000 observations. Don’t try this on an old computer! For a smoother line, I calculated a weekly average. Same data – just prettier.

If you really need more detail, I also made an interactive chart with daily-level resolution (5,044 observations). Keep in mind, Javascript is required to view the chart, and it probably won’t look good on mobile devices. If you’ve ever used Google Finance to view stock prices, the chart format will look familiar.

Summary Statistics by Day of Year

Sea temperature varies by season, but there are also year-to-year variations. In 2010, for example, the Catalina Channel was unusually cool (even in summer). In 2006 it was unusually warm. Perhaps you’ve wondered: What is the typical water temperature on a given day of the year? If your swim is scheduled for August 15, what is the average water temperature on August 15, averaged across all years?

To answer that question, I made this chart (click to enlarge):

Most Catalina swims take place in summer and early fall (not winter or spring), so here’s a zoomed version of the same data, for the swim season only:

So, water temps in the Catalina Channel tend to peak around August 1, and remain more or less steady through the first week of September. But even in early June and late October, the water is still “warm” by English Channel standards.

Note: It’s important to remember that surface water temps in Southern California tend to drop a few degrees as one approaches the coast, due to upwelling from the steeply sloping ocean bottom. My understanding is that this tends to happen about 3 miles from shore. So, if the buoy reading (6.5 miles offshore) is 63 degrees, the actual surface temp might actually be sub-60 during the last part of your swim.