Athlete-specific Prediction Equations For Appendicular Upper And Lower Body Lean Soft Tissue With BIA

Abstract

Given sport specific physiological demands, knowing the distribution of lean soft tissue among the body segments is of relevance for optimizing athletic performance, monitoring response to specific training regimens, as well as for evaluating potential injury risk. Bioelectrical impedance (BIA) is a widely used portable, low cost, and easy technique to assess body composition. However, most equations used by BIA to predict lean tissue are not specific for the athlete population. PURPOSE: The aim of this investigation was to develop and cross-validate prediction equations to estimate dual-energy X-ray absorptiometry (DXA)-derived appendicular lean soft tissue (LST) of the arms and legs based on whole body BIA in a population of athletes. METHODS: Two-hundred sixty-five athletes (age 22.2 ± 4.6 yrs) from a variety of sports had LST of the arms and legs assessed by DXA and whole-body reactance (Xc) and resistance (R) measured by BIA. Using measures of height, the resistance index (RI=height2/R) was calculated. Prediction equations were established using a cross validation method where 177 athletes (2/3 of the sample) were used for equation development and the remaining 88 athletes (1/3 of the sample) were used for equation validation. RESULTS: The developed prediction equations were as follows: arm LST=0.940*sex (0=male; 1=female) + 0.042*total body weight (kg) + 0.080*RI + 0.024*Xc – 3.927; leg LST= 1.983*sex(0=male; 1=female) + 0.154*total body weight (kg) + 0.127*RI - 1.147. Both equations cross-validated very well for the arms (mean difference=0.11 kg, R2=0.89, SEE=0.61) and for the legs (mean difference=0.05 kg, R2=0.81, SEE=1.95 kg). There were no differences (p >0.05) in the mean values for both arm and leg LST equations and LST assessed with DXA. CONCLUSION: The developed BIA-based prediction equations seem to provide a valid estimation of upper and lower body LST in athletes.