Purpose: Because maximal strength varies with body mass, the International
Powerlifting Federation (IPF) has adopted a method of adjusting powerliftin
g events (bench press, BP; squat, SQ; deadlift, DL, and total lift (the sum
of BP, DL, and SQ), TOT) by body mass. This method, the Wilks formula, mul
tiplies one's lift by an index based on body mass so that lifters of differ
ent size can be compared on the same event. The Willis formula is not, howe
ver, based on published data and has yet to be critically evaluated. The pu
rpose of this investigation, then, was to validate the Wilks formula. Metho
ds: This was performed by 1) examining residuals bias to verify that the ad
justed score does, in fact, lead to no systematic bias based on body mass a
nd 2) by applying a more theoretically supportable allometric model to the
same data and comparing the fit with the Wilks approach. Subjects were the
current mens and women's world record holders as well as the top two perfor
mers for each event in the IPF's 1996 and 1997 World Championships (a total
of 30 men and 27 women for each lift). Results: Results of data analysis r
egarding the Wilks formula indicate that: 1) there is no bias for men's or
women's BP and TOT; 2) there is a favorable bias toward intermediate weight
class lifters in the women's SQ with no bias for men's SQ; and 3) there is
a linear unfavorable bias toward heavier men and women in the DL. Furtherm
ore, the allometric approach indicated a bias against light and heavy men a
nd women which may be considered acceptable given that half as many lifters
are found in the lightest and heaviest weight classes as in the intermedia
te weight classes. Conclusion: As used currently (BP and TOT only), the Wil
ks formula appears to be a valid method to adjust powerlifting scores by bo
dy mass.