Sinclair Coefficients

The Sinclair Coefficients are a means to compare different weight classes in Olympic weightlifting.

There are eight bodyweight categories for male athletes: 56kg, 62kg, 69kg, 77kg, 85kg, 94kg, 105kg and +105kg, and seven for female athletes: 48kg, 53kg, 58kg, 63kg, 69kg, 75kg and +75kg.There are also two types of lifts: snatch, and clean and jerk. However, at the championships, medals are presented in both lifts separately, and in total (the combined result of the best snatch and the best clean and jerk).To compare and rank the results, especially between bodyweight categories, the International Weightlifting Organization uses the Sinclair Coefficients which are derived statistically and calculated for one Olympic cycle (for four years, starting in the Spring of each Olympic year).

The total for each bodyweight category is a projection of the Total for that weightlifter if he/she were a competitor in the heaviest bodyweight category with the same level of ability. It is done in four body weight categories for the males (56kg, 69kg, 77kg, +105kg). For the other four categories (62kg, 85kg, 94kg, 105kg) the Sinclair Total represents the World Standard because nobody as of March 2008 has lifted the predicted total. Those projections using the Sinclair Total are shown below.

The Sinclair Coefficient is $10^\{A(\{log\_\{10\}\{(x/b))^2\}$ if "x"<"b" where x is the weightlifter's bodyweight, b is the world record holder's bodyweight (in the heaviest category) and A is the coefficient for this Olympic cycle, or 1.0 if "x"≥"b".

Then, the Sinclair Total is simply the obtained total multiplied by the Sinclair Coefficient.

For example, in 2008, a calculation of the Sinclair Coefficient might look like this:

A=0.845716976 for malesA=1.316081431 for femalesb=168.091kg for malesb=107.844kg for females

Assume that we are assessing a male weightlifter weighing 56kg with a total of 305kg.Then, x=56kg, and we haveX=log10(x/b)=log10(56/168.091)=-0.477356434A(X^2)=0.845716976*(-0.477356434)^2=0.845716976*0.227869165=0.19271282110^(A(X^2))=10^0.192712821=1.558521584

Sinclair Total = Actual Total x S.C. = 305 kg x 1.558521584 = 475.349kg

To understand the whole idea, here is the chart with all male bodyweight categories (in kg) and its world record Totals, Sinclair Coefficients, and Sinclair Total. By looking at the Sinclair Total we can determine the RANK. * denotes a World Standard rather than a world record.The same is done for the seven female body weight categories.