Yesterday Open Water Source hosted a fascinating web-presentation by Peter Attia, a physician and Catalina Channel solo swimmer. The topic: Nutrition for Open-Water Swimming. Right up my alley, to say the least! There’s good news and bad news.
Bad news first: The webinar was oversubscribed so, despite pre-registering a week ahead of time, I got locked out. The good news: I was able to obtain the audio and slides, and “listen in” after the fact. (Friendly suggestion to the good folks at Open Water Source: Please don’t overbook your webinars. I realize they’re free, but still…)
The even-better news: The webinar was excellent. Though, somewhat different than I expected. A few weeks ago a friend sent me a whitepaper authored by Dr. Attia, entitled “Swimming in the Intensive Care Unit.” The gist of the paper is that a marathon swim is enormously stressful on the body, producing physiological symptoms not unlike those of a patient in the ICU with a traumatic injury.…
How many calories should you consume in a marathon swim?
According to an article on the ”Nutrition Demands of Open Water Endurance Swimming,” swimming burns 2.93 calories per mile, per pound. The author, Don Macdonald, did the math and figured that he burns approximately 15,000 calories during a 24-mile swim. Later in the article, Macdonald goes on to say:
As you can imagine, it is difficult to eat 15,000 calories over a 13-hour period without training the stomach to handle this input.
Leaving aside the reasons (discussed previously) that the above formula is probably bogus, let’s think about this: eating 15,000 calories in 13 hours. That’s 1,154 calories per hour. Burning this many calories is one thing. You might be able to do it for an hour; probably not for 13 hours straight.…
In the last post I bemoaned the lack of credible science about marathon swimming. One is reminded of the William Goldman quote about the movie industry: Nobody knows anything.
Here’s a good example. A few days ago a Facebook friend linked to an intriguing-looking article. Published on a science-y looking website (“Your one-stop resource for longevity, health, exercise, nutrition, and scientific articles all to help you live a longer, fuller life”), the article is authored by marathon swimmer Don Macdonald.
One section seemed of particular interest: “Nutritional Demands of Open Water Endurance Swimming.” An excerpt:
Nutritional endurance demands biochemical changes of your body. The basic calculation for the amount of calories burned while swimming is 2.93 calories per mile, per pound. I weigh 207 pounds, and therefore burn 14,556 calories in a 24-mile swim, (2.93 calories x 24 miles x 207 pounds = 14,556 calories).
In marathon swimming, there’s very little in the way of credible science – that is, methodologically rigorous, experimentally controlled, peer-reviewed science. It’s not hard to understand why: Open-water swimming, especially the marathon variety, is a tiny market compared to land-based endurance sports. Market size is related to the potential for making money, and the potential for making money is, in turn, related to funding and motivation for scientific research. Even in triathlon (an enormous, lucrative market), swimming is often seen merely as a warm-up to the bike and run, so there’s little effort to understand it.
As a result, marathon swimmers are left with approximately four strategies for acquiring knowledge about their sport – specifically, the physiological demands of long-distance swimming, and the nutrition required to fulfill those demands:
- Figuring out what is known, scientifically, about land-based endurance activities, and applying it to swimming.