Multicomponent cross-validation of minimum weight predictions for college wrestlers

In 1998, the National Collegiate Athletic Association (NCAA) adopted a rule requiring that skinfolds (SF) or hydrostatic weighing (HW) be used to estimate minimum weight (MW) in college wrestlers. Purpose: To cross-validate the NCAA methods for estimation of MW using a multicomponent criterion (4C). Methods: Criterion MW was calculated from body density (BD), bone mineral content (BMC), and total body water (TBW) using the 4C equation of Lohman (1992). BMC was measured by dual energy x-ray absorptiometry (DXA), TBW by deuterium dilution, and BD by HW. Subjects were Division I athletes from the University of Wisconsin (mean +/- SD; N = 33, age = 19.5 +/- 1.3 yr, height = 177.3 +/- 7.8 cm, weight = 74.2 +/- 9.3kg). Results: There was no significant difference between mean MW from HW (69.6 +/- 8.5 kg) and SF (70.1 +/- 8.3 kg) (P = 0. 113), and between mean MW from HW (69.6 +/- 8.5 kg) and 4C (69.5 +/- 8.6 kg) (P = 0.46). A clinically small, yet significant difference was seen when comparing mean MW from SF to 4C (P = 0.013). The regression for the relationship between 4C and HW (y = 0.994 X HW + 0.294 kg, R-2 = 0.985) and 4C and SF (y = 1.019 X SF - 1.895 kg, R-2 = 0.979) did not significantly deviate from the line of identity. Pure error (PE) values of 1.04 kg and 1.35 kg were found for HW and SF, respectively. The difference between the methods was plotted as a function of the 4C criterion. The regression line for HW and 4C (y = -0.009x + 0.743, r = -0.07, P = 0.69) and SF and 4C (y = -0.038x + 3.259, r = -0.27, P = 0.13) suggest that no systematic differences in the prediction were associated with the size of the criterion. Conclusion: These data support the NCAA methods of HW and SF to predict MW when cross-validated using a 4C criterion in this sample.