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 body weight vs. race times
Rickshaw
Runworks 2005 5M Racer
San Francisco, CA
Joined: 26 Nov 2004
Posts: 1157

body weight vs. race times Posted: Sun Apr 30, 2006 8:13 pm 

While browsing Daniels' Running Formula this weekend, I noticed something about how to adjust VDOT for changes in body weight. It was in reference to compensating for weight gain after a period of time off, but I don't see why it couldn't be applied more generally.

Basically, Daniels says that your VDOT multiplied by body weight should equal a constant number. So for every 1% decrease in body weight, you should expect a 1% improvement in VDOT. That's actually a bigger effect than I would have expected. For a 160 pound runner at VDOT 46, that means shedding only 3.5 pounds would boost your to VDOT 47. That's the difference between a 3:25 and 3:21 marathon!

It probably wouldn't be smart to take this as a reason to diet and drop your weight to an unhealthy level. After all, we runners need calories! But for those of us who have a few extra pounds of flab to shed, the gain from dropping even a couple of pounds can be significant.


mfox

South Orange, New Jersey
Joined: 19 Dec 2004
Posts: 367

Re: body weight vs. race times Posted: Mon May 01, 2006 6:31 am 

That kind of makes sense. Don't the experts say that you should expect to improve your time just by wearing lighter racing flats. And in that case it's only a loss of a few ounces. So I can believe that a few pounds should have a significant impact over a long distance. Frankly, this is what I'm counting on to improve my marathon time. I don't think I've ever run a marathon at much less than 195 lbs and I'm hoping to improve my time significantly just by dropping another 20lbs.

Rickshaw
Runworks 2005 5M Racer
San Francisco, CA
Joined: 26 Nov 2004
Posts: 1157

Re: body weight vs. race times Posted: Mon May 01, 2006 7:45 am 

I think weight on your feet has a much bigger effect than general body weight. You need to spend energy to accelerate and deccelerate your foot with every stride, but weight elsewhere on your body, especially above your waist, will be moving along at more of a constant speed. I think the rule of thumb is that an ounce of shoe weight reduction will gain you 2 sec/mile. For runners around our weight and speed, the corresponding body weight conversion is about 1 pound reduction to gain 2 sec/mile. Big difference!

Mfox, if you've actually got 20 pounds to drop, I'm impressed. You'll be smoking us all!


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