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SEVERE EXERCISE INDUCED GLYCOGEN DEPLETION CHANGES DUAL X-RAY ABSORPTIOMETRY AND BIOELECTRICAL IMPEDANCE ON BODY COMPOSITION

Abstract

Leah Stone1, Hannah Smiles1, Jake Hammond1, and Brian Snyder1

1Truman State University, Kirksville, Missouri

Dual x-ray absorptiometry (DXA) is considered one of the most accurate methods to measure body composition when completed with careful standardized protocols. Bioelectrical impedance (BIA) devices are also commonly used to assess body composition measurements in athletic settings. Recent evidence suggests that glycogen and hydration status affects body composition measurement, indicating a need to standardize the pre-measurement period in order to improve reliability of repeat measurements. PURPOSE: This investigation aimed to test the accuracy of DXA and BIA devices before and after a glycogen depleting severe exercise bout. METHODS: Ten moderately trained male athletes (VO253.1 ± 4.7 ml/kg/min, age 23.6 ± 6.8) undertook a test-retest assessment of body composition measurements using a DXA, a handheld BIA device, as well as a BIA foot device before and after completion of an established glycogen lowering protocol, strength testing, and 5k time trial on a treadmill as part of a separate study. Pre and post body weight and urine specific gravity were also assessed. RESULTS: The severe exercise bout produced significant (p<0.05) changes in DXA and both BIA assessments tools as follows: (mean ± SD pre, post;) BIA Hand: 13.3% ± 3.9, 11.4% ± 4.2, BIA foot: 11.2% ± 3.2, 9.0% ± 2.7, and DXA: 18.1% ± 4.9, 17.6% ± 4.9. Pre-Post urine specific gravity values were not significantly different. Participants lost a statistically significant amount of weight from the exercise protocol 79.4 kg ± 8.6, 78.3 kg ± 8.6. The average difference between pre-post hand and foot BIA were not significantly different from each other but were significantly different than DXA. CONCLUSION: The significant changes in body fat percentages illustrate variability between pre and post measures which are not reflective of fat mass or muscle changes from the exercise bout per se. The ability to accurately measure body composition for athletes can be crucial for accurate interpretation.

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