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Old 11-05-2007, 07:24 AM   #1
Jared Ashley
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Cool Scaling Idea!

First off, I discovered crossfit a month ago after 3 years of big-box-type working out... I love it! After initial huge gains I've been stuck for over a year, and 1 month on crossfit has already changed everything.

Anyway, I see a lot of questions about scaling, and I though I'd share a method that I haven't seen come up on this site yet.

Everyone knows the 1RM type tests favor the big guys... at 135 lbs I max bench at 185; not bad, but my 240 lb roommate who never works out can do half a dozen reps at 185. The typical solution is to use "% of bodyweight", but I think that has the opposite problem, and skews it in favor of the little guy. My proof is that I could do 14 consecutive strict pull-ups before I ever lifted a barbell... find me a big guy who can claim that! So how do you scale fairly?

Here's the hypothesis: First, that strength is proportional to muscle cross-section, and second, that as body size increases, weight will increase as a cube while cross-section increases as a square. Thus, in theory, 1RM strength should increase as a 2/3 power of weight. The mathematically minded should follow this, for everyone else you don't really need to understand it, just to know how to use it.

So here's how to use it: crossfit assumes the standard man is 175 lbs, so each person calculates a correction based on that. The formula is:

Correction = 100*(your weight/175)^(2/3)

So, my correction = 100*(135/175)^(2/3) = 84%
My roomie's correction = 100*(240/175)^(2/3) = 123%

So for the 225 lb deadlifts in "Diane" I would scale down to 84% (189 lbs), while he would scale UP to 123% (277 lbs).

For the ladies, since healthy men are typically in the 10% bodyfat range while healthy women are closer to 20%, I could see an additional 10% weight reduction:

For 135 lb woman, 84% * 90% = 76% = 171 lb "Diane"

This might sound like a lot of math, but it really isn't... once you've calculated your correction, you never have to again unless your bodyweight changes... for those making large gains/losses, re-calculating once a month would be enough. I can use my 84% correction for EVERY exercise where a specific weight is given.

For those who are interested, I got this formula from here:

http://academic.udayton.edu/PaulVand...%20Reprint.pdf

Thoughts?

For the record, I don't plan on stopping at my 84% mark I'll keep working until I can do the WOD as rx'd... this just gives a good benchmark since 21x225 deadlifts or 30x135 cleans sounds a LONG way off! for the super-strong big guys, this gives you a new challenge since some of those numbers were probably easy to get to.
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Old 11-05-2007, 10:13 AM   #2
James Napier
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Re: Cool Scaling Idea!

My scaling method for metcon wods is to use 1RM/2 but that usually wipes me out; this got me to thinking that I should be a little closer to 1RM/3.
As my 1RM goes up, so do all of my scaled loads.
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Old 11-05-2007, 10:55 AM   #3
David Wood
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Re: Cool Scaling Idea!

Jared: great first post, especially for the math geeks like me! I like the approach . . . but ultimately, yes, work toward "as Rx'd". I'm 155 pounds, and can do most WODs as specified (except for the overhead pressing stuff; shoulder injuries). You can get there.

Also, please make sure to affirmatively designate any links you post as "work and family safe" (usually abbreviated as w/fs), or not. You don't have to post only safe links, but you do have to designate them as safe or not, every time.

That link was fine (safe), and we cut newbies a lot of slack on this, so don't worry.

Welcome!!
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