EVALUATION OF AIR DISPLACEMENT PLETHYSMOGRAPHY FOR ASSESSING BODY DENSITY AND BODY COMPOSITION IN FEMALE ATHLETES

Abstract

Body composition measures are important to female athletes and team personnel to assess training effectiveness and to monitor for adverse physiological changes. The use of multi-compartment models, which often require a measure of total body density (Db), are necessary to provide a more accurate measure of body composition in female athletes due to possible alterations in the densities and proportions of the fat-free masses. Traditionally, Db has been determined by hydrostatic weighing (HW). Recently, air displacement plethysmography (AP; Bod Pod; Life Measurement Instruments, Inc) has been proposed as an alternative technique for Db determination. PURPOSE: To compare AP measures of body volume (VbAP) and body density (DbAP) with HW measures of body volume (VbHW) and body density (DbHW), and to compare resulting 4-compartment model %Fat (4-Comp %Fat) measures when DbAP was substituted for DbHW in a group of female athletes. METHODS: Twenty-five female intercollegiate athletes completed AP, HW with residual volume measures, and additional body composition measures during a single testing session. Paired t-test were used to compare VbAP to VbHW, DbAP to DbHW, and 4-Comp %Fat measures. Regression analyses and total errors (TE) were used to assess the strengths of these relationships. RESULTS: Group mean comparisons (mean ± SE) showed that VbAP (62.09 ± 1.40 L) and DbAP (1.0455 ± 0.0023 g/cc) were significantly different (p < 0.01) from VbHW (61.37 ± 1.36 L) and DbHW (1.0584 ± 0.0021g/cc). Significant correlations were found for the Vb (r = 1.00) and Db (r = 0.84) measures. TE for Vb and Db were 0.83 L and 0.0143 g/cc, respectively. Further analysis revealed that 4-Comp %Fat (mean ± SE) using DbAP (24.8 ± 1.2%) was significantly (p < 0.01) greater than 4-Comp %Fat using DbHW (21.7 ± 1.2%). The correlation and TE between 4-Comp %Fat measures was r = 0.96 and 3.4%, respectively. CONCLUSION: These data show that AP systematically underestimated Db, and overestimated Vb and 4-Comp %Fat compared to HW measures in this group of female athletes.