(41) THE ACCURACY OF A METHOD TO PREDICT BODY FAT PERCENTAGE FROM BODY MASS INDEX IN FEMALE WEIGHTLIFTERS.

Purpose: Body mass index (BMI) is the ratio of body weight to height and is a commonly used body composition metric. While BMI does not differentiate between fat mass and fat-free mass, equations have been developed to estimate body fat percentage (BF%) from BMI. However, the accuracy of these equations has been insufficiently studied, particularly in female weightlifters. The purpose of this study was to determine the accuracy of a BMI based equation for predicting BF% in female weightlifters. Methods: Twenty-four female weightlifters (age = 24.9±5.4 years, height = 163.8±6.4 cm, weight = 66.3±7.4 kg) participated in the study. Height and weight were taken for each subject to determine BMI, calculated as weight in kilograms divided by height in meters squared (kg^.m^-2). The following regression equation for estimating BF% based on BMI previously developed by Jackson et al. (JBMI-BF) was used in the study: Predicted BF% = (4.35 x BMI) – (0.05 x BMI²) – 46.24. Dual energy X-ray absorptiometry (DXA) was used to obtain the criterion BF% values. Results: The results showed no significant difference (p=0.28) in mean BF% values between the two methods (JBMI-BF = 30.2±5.1% versus DXA = 31.3±4.4%). The predicted JBMI-BF value was significantly correlated (r=0.42, p=0.04) to DXA and showed a standard error of estimate (SEE) of ±4.1%. Limits of agreement showed a 95% confidence interval (constant error±1.96 SD) of -1.1±10.0%. Conclusions: The JBMI-BF equation showed similar mean values of BF% compared to DXA. However, large SEE and limits of agreement suggest a wide range of individual error. Practical Applications: Due to the findings of this investigation, BMI could potentially be utilized within a field setting to predict mean BF% for an entire group of female weightlifters but would not be appropriate for predicting BF% for individuals. Therefore, extreme caution must be taken when using BMI-based BF% equations to estimate BF% in female weightlifters. Acknowledgements: None