# A new estimation equation to assess body composition in an athletic population

## TL;DR

This study creates a new equation to more accurately estimate body fat percentage in athletes using air displacement measurements.

## Contribution

A novel estimation equation for body fat percentage in athletes using body density from air displacement plethysmography.

## Key findings

- The new equation explained 90.5% of the variance in body fat percentage.
- The new equation produced body fat estimates not significantly different from DXA measurements.
- The equation showed strong reliability with high interclass correlation coefficients.

## Abstract

Research has shown air displacement plethysmography (ADP) to be a valid and reliable alternative to dual-energy X-ray absorptiometry (DXA) in the general population; however, its validity and reliability indicate conflicting evidence in an athletic population. The purpose of this study is to develop a novel estimation equation using body density obtained from ADP in an athletic population to assess body fat percent (BF%) more accurately.

One hundred and thirty (males, n = 69; females, n = 61) National Collegiate Athletic Association Division I athletes participated in this study. Thirty athletes were randomly withheld for the hold-out sample, and the remaining 100 athletes were used in the development of the equation. Body composition was evaluated using ADP and DXA. Linear regression was used to develop a new prediction equation (Equation 1) with body density (ADP) as the independent variable and BF% (DXA) as the dependent variable. Repeated measures analysis of variance was used to identify differences between ADP–Brozek, DXA, and Equation 1. Interclass correlation coefficients (ICCs) were assessed to evaluate the reliability of the equation.

Significance was set to p < 0.05. Linear regression was conducted to create Equation 1, which explained 90.5% of the variance. ADP–Brozek reported lower BF% than Equation 1 (p < 0.001) in the development and hold-out samples; however, BF% from Equation 1 and DXA were not different from each other (p = 0.999). ICCs were strong in both samples (original sample: ICC = 0.975, p < 0.001; hold-out sample: ICC = 0.964, p < 0.001).

The newly proposed equation may be used with ADP measurements to interpret BF% in an athletic population.