G. Perle-Jones, E. Logsdon, K. Hopkins, A. Kuhn, M. Lockard

Willamette University, Salem, OR

Air displacement plethysmography (ADP) is a widely used method in body composition analysis which relies on the principles of air compressibility. In the ADP chamber, variations in seated posture can affect trapped air pockets and exposed skin surface area; therefore, the changing the compressibility of the adjacent air which may affect calculated body composition results. PURPOSE: To analyze the effect of various seated postures on body fat composition results using air displacement plethysmography. METHODS: 24 college- aged students were recruited from Willamette University. Body composition was assessed using an ADP chamber. Four positions were tested, seated normally, seated with an arched back, seated while leaning forward, and a maximal surface exposure condition in which subjects positioned their body to maximize airflow around them. A repeated-measures ANOVA with Bonferroni correction and pairwise post hoc analysis assessed the effect of posture on body composition. RESULTS: Posture had a significant impact on body composition (p<0.0001). Compared to the normal posture, the leaning forward posture had a 0.97% lower average body fat result (p=0.002), arched had a 1.42% higher reading than bent posture (p<0.001) and arched was 0.16% higher than maximize (p=0.015). There was no difference between normal and either the arch or maximize postures (p=0.96, p=0.4 respectively). Finally, there was no difference between leaning forward and maximize posture(p=1.00). CONCLUSION: ADP is sensitive to changes in seated posture, resulting in variations in body composition results, likely due to changes in air compressibility. These significant differences indicate a need to further research which postural position is the most accurate and create a standardized protocol for posture in air displacement plethysmography chambers.

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