## Saturday, July 21, 2012

### Mount Diablo Time Trial: the denominator problem

As I was standing at the finish of the Mount Diablo Time Trial, I suddenly remembered that I'd left a pack of Gu in my pocket. Gu was sponsoring the race and there had been a box of peanut butter Gu's at registration. I'd taken one and put it in my back pocket, intending to leave it with the backpack I had stashed at the start line. But I'd forgotten... would have been better to push it under the leg of my bib shorts where I'd be less likely to overlook it.

All of this seems like a lot of fuss over a little Gu, but Gu packs are 30 grams each. That's around 0.5 seconds extra climbing time for the course, which consists of the first half of the climb to Diablo summit from the north (formula for estimating this sort of thing). Sure, usually 0.5 seconds doesn't matter, but sometimes it does. As it turns out, I ended up 5th in my age group, 1.9 seconds out of 4th, 5.0 seconds out of 3rd. So 0.5 seconds alone didn't make a difference. But people spend a lot of money to save 30 grams: Anyone going with a top-end group because it's lighter is spending around \$120 for each 30 grams saved. So it's important to save weight where one can.

Of course, it's important to not lose sight of the big picture, and the dominant factor in weight is the weight of the rider. And here was the real problem: right now I'm around 3.2 kg heavier than when set my Old La Honda PR back in December. In fact, I don't think I've ever raced as heavy as I am right now.

Body mass is always a balance between input and output. So it's important to look at both sides.

On the input side, the obvious approach is to identify some relatively calorie dense choices I tend to make and replace them with less calorie dense options. For example, when I ride in I tend to stop for one or even two oat cakes at a coffee place near work, which is in a car-dominated wasteland of very limited choices. I need to come up with a better alternative to these dense bricks of oats and sugar.

But on the output side, I need to start running again. I am convinced regular running promotes a lower steady-state mass than cycling generally does. One can hypothesize all one wants about why this might be, but whatever the reason, I have observed that when I run I'm lighter than when I don't, and participants in running races seem to be generally leaner than participants in cycling events. Even racers have a tendency for a bit of a gut, something I simply don't see at the typical trail run. On a microscopic level, there's always the calories-in, calories out argument. But few of us count our calories: we eat to a point of satiation, driven by hunger and/or perceived weakness. There's something different between running and cycling in the way these activities stimulate hunger and promote metabolism.

Ah, yes... Diablo. My time wasn't that bad, actually, but there was a bit of a tail wind this year, and I think times were generally strong. I can say for sure I wasn't climbing at the level I was last fall. On the positive side, my power seems fine, but gravity has the irrefutable property that retarding force is proportional to mass, so power alone doesn't get you up a hill. I know plenty of riders with impressive power who don't climb as well as they should because of issues with the denominator rather than the numerator of W/kg.

3.2 kg should have been worth around 52 seconds which would have had me within 20 seconds of Carl Nielson, solidly in third.

In any case, I'm registered for the California International Marathon in December, so I need to start running again in any case, and sooner rather than later. It will be interesting to see if this helps resolve my denominator problem.