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Determining Natural Bodybuilding Potential

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Can you determine natural bodybuilding potential? Is it possible to determine if a lifter is a natural or steroid user? The answer is generally yes to both questions.

The formula. The following equation is derived scientifically, studying approximately 300 winning drug-free strength training athletes and bodybuilders from 1947-2007. For more information please visit Casey Butt’s article, Your Maximum Muscular Bodyweight and Measurements.

H = Height in inches

W = Wrist circumference located at the hand side of the bony lump on the wrist (known as the styloid process)

A = Ankle circumference at the smallest measurement

BF% = The bodyfat percentage at which the ankle and wrist circumferences were taken

Determining Natural Bodybuilding PotentialThe information. Again, for more information on this subject, please visit Casey Butt’s Weightrainer.net.

Potential Variance. The natural bodyweight potentials listed below are derived using a wrist circumference of 7.5 inches, and an ankle circumference of 9.5 inches. These numbers are reasonable for the heaviest of natural lifters. (Note: the author’s wrist circumference is 8.0 inches, and ankle circumference is 10.0 inches at a bodyweight of 280 pounds. So you can see that for a natural lifter under 220 pounds, 7.5 and 9.5 are very reasonable numbers)

For a 0.5 differential in BOTH numbers (a lifter’s wrist is 8.0 inches and ankle is 10.0 inches instead of 7.5 and 9.5), the weight variance using the formula would be an additional 5.2 pounds of lean mass. In simple terms, for every additional inch of circumference (from either ankle, wrist, or both combined) above the potentials listed below, a lifter could have an additional 5.2 pounds of lean mass.

Again, keep in mind that the numbers used to derive natural potential (7.5 wrist circumference and 9.5 ankle circumference) are at the high end of normal for a natural bodybuilder with under 20% bodyfat. Therefore, a reasonable maximum potential variance for natural lifters from the below numbers would be plus 3 pounds. For smaller wrist/ankle boned lifters, the numbers could be smaller by up to 10 pounds.

The numbers. Using the above formula, and inserting 7.5 wrist inches and 9.5 ankle inches, we derive the following natural bodyweight lean body mass potentials for a 6% bodyfat percentage. Again, the derived numbers below are lean bodyweight, which means total bodyweight less fat. It is not total competition bodyweight including the 6% bodyfat.

The reduced formula with wrist and ankle circumferences and a 6% bodyfat percentage is…

H^1.5 (0.31037632)

Height, 66 inches = 166.4 lean body mass potential. Competition weight = 177.0 pounds

Height, 67 inches = 170.2 lean body mass potential. Competition weight = 181.1 pounds

Height, 68 inches = 174.0 lean body mass potential. Competition weight = 185.1 pounds

Height, 69 inches = 177.9 lean body mass potential. Competition weight = 189.3 pounds

Height, 70 inches = 181.8 lean body mass potential. Competition weight = 193.4 pounds

Height, 71 inches = 185.7 lean body mass potential. Competition weight = 197.6 pounds

Height, 72 inches = 189.6 lean body mass potential. Competition weight = 201.7 pounds

Height, 73 inches = 193.6 lean body mass potential. Competition weight = 206.0 pounds

Height, 74 inches = 197.6 lean body mass potential. Competition weight = 210.2 pounds

Height, 75 inches = 201.6 lean body mass potential. Competition weight = 214.5 pounds

Height, 76 inches = 205.6 lean body mass potential. Competition weight = 218.7 pounds

Bottom line. It is possible for a natural lifter to exceed these numbers by a very small percentage. But, it is virtually impossible for a natural lifter to exceed their potential by more then a few pounds. Based on ankle and wrist circumference, I think it is safe to say that a lifter who exceeds their natural potential by more than 5-10 pounds lean mass is certainly suspect.



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  1. I know this is an old article, but I have just one quick question and may have missed it somewhere.
    For BF% I’m heavy at 29.5% So should I use 29.5 in the formula or 0.295? One gives me 183 as max lean mass and the other gives me 162. I’m 66″ tall with a 7″ wrist and 10″ ankle. My current lean mass is 161, so I’d assume that I should be using the larger number. Just wanting some confirmation.

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  2. When it comes to the human body and nature, nothing is predictable, and nothing can ever fit perfectly into a formula or equation. In math, numbers are always numbers and they work out precisely every time, as long as you know what you are doing. For the past thirteen years I have been a natural bodybuilder and my weight gets up to 228 lbs. at 5’11”. Around ten to thirteen percent BF. When I grow I can always see my top four abs clearly. When I shred I usually get down to 212-216 lbs. with my lower abs, obliques, intercostals and serratus clearly defined. I haven’t measured my wrists or ankles but they appear very thin compared to my calves and forearms. Don’t give a shit about non-believers cause I’m looking sexy as shit, according to my plethora of sexy fitness women hanging on my arm. Formulas are for fools, the human body is more unique and complex than numbers.

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    • Bullcrap. Post a picture in the forum. I guarantee your body fat percentage is way off. “Nothing is predictable” = faery tale. Keep believing you can overcome human physiology 101 if you only try hard enough. These formulas are based on natural champions, and you have the balls to state you are the best ever. Post a pic.

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  3. Something is wrong with the equation. My wrist=6,7″, ankle 9,45″ and my height 70″
    When I try to do the math as presented above, I get 34,30 as a result =)
    And no, I’m not an idiot, but let me still present this once:
    Height x 1,5 = 105
    Wrist cf squared and then divided by the weird number given above (22,6670) = 0,1141
    Ankle cf squared and then divided by the other weird number above (17,0104) = 0,1807
    The last two added together = 0,2948
    Body fat % 24,3 divided by 224, after which 1,0 is added = 1,1084
    So 105 x 0,2948 x 1,1084 = 34,3094
    Apparently the weird numbers didn’t belong there. I just don’t know what does =)

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    • Dude it’s not height x 1.5 it’s height to the power of 1.5. Example – 10x 1.5 = 15. 10^1.5 = 31.6

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  4. So, I’m currently 225 lbs, 20% bf, wrist = 7.25″ and ankle is 9.5″, height 70″…if I calculated correctly, I should max at around ~193 lbs of LBM…and at my weight and BF% I’m at ~180 lbs of LBM….which means I have a while before I max out…and I have a lot of growing to go…sweet…

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  5. Anything is possible, I have already passed my LBM potentional 12+ pounds and havent even been lifting for 1.5 years. Wouldnt even know how to use steroids either. The human body is capable of amazing things.

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  6. This is pretty sweet.

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  7. hey…..This is one of the best blog for Nature body building.You given maths wise description its good for easy learn.thanks …..

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  8. Casey, I have changed some of the wording a bit in this article to leave it a tad bit more open ended. Thanks for your insight and inspiration.

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  9. Hi Steve,

    I think that while these equations very well could be used to spot steroid users, they shouldn’t be the final word. After all, however UNLIKELY it is that someone naturally surpasses the predictions it would be very limiting and demoralizing to suspect every legitimate natural who does approach the predictions. In fact, that would probably guarantee that no competitor ever even tries to surpass them for fear of persecution …which would create a self-fulfilling prophecy.

    I think the equations should be applied to competitors and, based on the results, further blood tests, etc, could be applied afterward — though this would not detect drug users who haven’t yet reached even their natural potentials.

    I do, however, think equations of these forms should replace the BMI. Especially in medical fields where classifications of overweight, diet recommendations, drug dosages, etc are based on height and weight, but usually completely ignore the impact of bone structure. It’s a very simple adjustment to fit the lean body mass equation to the general untrained population for the sake of such things.

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  10. No, they don’t use it as an indicator for natural competitions. But as a bystander, if someone is 10 pounds over their potential, you can pretty much know for sure that they have used something at some point.

    Nice looking website, btw.

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  11. Hey this article was very interesting. I have often wondered if there was a way to tell potential. Do they use this in testing for natural vs. non natural bodybuilders?

    They person that came up with that sure has a brain to come up with that formula.

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