Dehydration observation

I don't suppose this post will be of interest to most of you, but since I'm reading Dr. Tim Noakes' newest book Waterlogged, I thought I'd explain some observations I've begun on myself regarding dehydration during marathon training.

Before I started reading Dr. Noakes' book, I'd heard from many sources that one should try during marathon racing to avoid dehydration of any kind; a 0% drop in body mass. Other sources have suggested a 2% limit. Almost all of them agree that dehydration in excess of 2% will yield a sharp decline in performance.

To put it shortly, from what I've read of Waterlogged so far, these figures are not actually true for many people. In fact, time-and-again the winner of most long-distance races is also the most dehydrated. For example, when Haile Gebreselassie broke the marathon world-record in 2008, he lost 7% of his body-mass in the endeavor. According to what many of us hear these days, his performance should have tanked once his water-deficit climbed above 2,3, and 4%. That it didn't should at least give us pause. I hope to have a much more detailed summary and discussion once I've finished Dr. Noakes' book, but until then we'll leave the topic there.

Bearing all this in mind, I decided to see how much weight I lost during this morning's marathon workout in the heat and humidity. Upon leaving the house today I weighed roughly 157.5 lbs, and upon returning weighed 154.0 lbs. That's 3.5 lbs, or 2.3% of my body weight. With that in mind, I should like to see how that number changes as the workouts become longer. Will a greater percentage-loss have a pronounced effect on performance? How much weight can I lose during a race or workout without it compromising my ability?

These are important questions, because it is very likely I will lose a lot of weight during the marathon race, and one adaptation I'll need may be to have a high dehydration tolerance. It's something to which I intend to pay closer attention, so we'll see what happens. In the mean time, I highly recommend checking out Dr. Noakes' book.

Happy Friday, friends :)