More on the Wilks Formula
Since I get regular requests from various people to please give
them the actual "formula" so that they can input it into their
programmable calculators to use at meets I have decided to put this
as a link on-line
where they can access it. I received the following
from Dave Bracken who received it from an IPF Committee member and
I cannot otherwise vouch for it. Try plugging some actual values in and
see if it produces the desired values.
The data used to determine the Wilks coefficient were the totals of all of
the first place lifters at all of the world championships since the beginning
of the IPF worlds. Men's data for the men's formula and women's data
for the women's formulas.
The formula is:
reduced total = total lifted *500/(a+b*x+c*x^2+d*x^3+e*x^4+f*x^5) Where x is the body weight of the lifter in kilograms The coefficients for men are: a=-216.0475144 b=16.2606339 c=-0.002388645 d=-0.00113732 e=7.01863E-06 f=-1.291E-08 The coefficients for women are: a=594.31747775582 b=-27.23842536447 c=0.82112226871 d=-0.00930733913 e=0.00004731582 f=-0.00000009054
Questions and Answers Regarding Wilks and Other
Handicapping Systems:
Q: What research and physiology science is there behind these
handicapping systems such as the Schwartz, Malone, and Wilks formulae?
***Generally, all that these folk have done is to use various regression
methods to fit a curve to the world's records for all bodymass divisions,
with no attempt to explain any underlying physiology.
Q: Are there published and peer-reviewed studies that explain the
methods used to construct the Wilks system? Where is the evidence that the
other systems are biased and that the Wilks corrects them?
***Siff's regressions and those of Sinclair have been
published in academic journals.
Q: How can USAPL (USA Powerlifting) meet directors and referees
explain coherently to second or third-placing lifters why the Wilks coefficients were used to rank them
as they did?
***Robert Wilks was a member of the International Powerlifting Federation
at the time the Wilks formula was adopted. The formmula developed
of the late Mel Cunningham Siff, a South African professor of civil engineering
who had a passionate interest in Olympic weightlifting and other strength sports,
had a coefficent of correlation between the actual data and the values of the
Siff formula values of better than 99.6 percent
which is far better than the other formulae, hence it has led to far fewer
conflicts in competition. There is a website which
compared our different formulae and here is link to the Siff Formulae.
Q: After one bench-press competition in which I officiated as a referee I was asked by a
150 lifter, who had lifted over twice his body-weight (315 lbs), to
explain to him why another lifter weighing 265 who pressed 500 got first
place in that competition when in fact that lifter had lifted less
than twice his bodyweight. I was at a real loss to explain to him why the
Wilks coefficients were such a reliable and reasonable way to compensate for
differences in bodyweight.
***The problem here is that the Wilks vales were developed for t-o-t-a-ls and not
for individual lifts. Therefore it is even more inappropriate to use any
of the systems for ranking anything but what they were determined for -
namely TOTALS. Therefore when the Wilks coefficients are applied to
single lifts different effects occur. Bench increases most with body weight
so when the Wilks coefficients are used to rank bench press meets this
greatly favors the heavier lifters. When the Wilks coefficients are used
on a single lift deadlift meet it greatly favors the lighter lifters since
deadlifts alone do not increase as fast with body weight as total does.
It may be appropriate for squats but it probably favors the lighter
lifters again if it is applied to single lift squats. A fit to individual
lift data is what is needed if individual lifts are compared. (Thanks to
Dr. Dave Bracken, an Los Alamos nuclear physicist and world champion powerlifter for this answer!)]
Q: In any case I would like to understand the science and methodology behind the Wilks system . . .
Siff; Now that I have seen the Wilks formulae, I have been able to compare my system with his by applying them to the current men's world records, as tabulated below. What I have done is compute the scores for both of our formulae so that they reflect a percentage of the mean of the world's best performances.
Q: Who are the world's best powerlifters according to the Wilks and Siff body-weight hanicapping formulae?
BMASS LIFTER RECORD SIFF SIFF WILKS WILKS Score Rank Score Rank 52 Andrzej Stanaszek 592.5 104.87 3 116.28 10 56 Hu Chun-Hsiung 637.5 100.53 7 116.07 11 60 Joe Bradley 707.5 102.17 5 120.68 6 67.5 Alexei Sivokin 800.0 102.58 4 123.36 4 75 Rick Gaugler 850.0 100.38 8 121.14 5 82.5 Mike Bridges 952.5 105.90 1 127.62 1 90 Mike Bridges 937.5 99.55 9 119.70 7 100 Ed Coan 1035.0 104.90 2 123.32 2 110 Alexey Gankov 1002.5 98.10 11 117.99 9 125 Kirk Kaworski 1045.0 98.36 10 119.10 8 125+ Bill Kazmaier* 1100.0 100.66 6* 122.94 3*
[Note by Andy Anderson: Kazmaier's total is set apart from the others, because Dr. Mel Siff who provided these results, did not know what his bodymass was when he achieved his 1,100 kg total - in his calculations, he estimated 140 kg as his body-mass, which yielded the values above. If that is anywhere close to his actual body-mass, then he would rank as shown.