Emily A. Buck, Michael J. Saunders, Elizabeth S. Edwards, FACSM, Christopher J. Womack, FACSM. James Madison University, Harrisonburg, VA.

BACKGROUND: Acute fluid ingestion causes an increase in estimated body fat percentage (BF%) measurements by single frequency (SF-BIA) and multi-frequency bioelectrical impedance analyses (MF-BIA). However, it is unknown if MF-BIA accurately measures total body water (TBW) and BF% after chronic fluid retention. Creatine supplementation causes fluid retention, and resultant increases in TBW and body mass. The present study sought to determine if MF-BIA can detect fluid retention secondary to creatine supplementation. METHODS: 13 male and 14 female subjects (18-22 y) completed one week of creatine monohydrate (Creapure) or maltodextrin supplementation at a dose of 0.3 g/kg body weight. Subjects completed pre-supplementation and post-supplementation measurements of body composition including dual-energy x-ray absorptiometry (GE Lunar iDXA), SF-BIA (OMRON Handheld Fat Loss Monitor), and MF-BIA (InBodyUSA 770) to measure BF%, fat free mass (FFM), and fat mass (FM). These dependent measures were analyzed using repeated measures ANOVAs. Additionally, intracellular water (ICW), extracellular water (ECW), and TBW were estimated by MF- BIA and analyzed using repeated measures ANOVAs. Post-hoc testing was performed using contrasts via SPSS statistical software. P < 0.05 was considered statistically significant for all tests. RESULTS: Creatine resulted in a 2% increase (p < 0.05) in TBW between pre- and post-supplementation measured by MF-BIA (40.4 ± 9.5 to 41.2 ± 9.6 kg). FFM increased significantly more in the creatine group compared to the placebo group measured by all body composition modes (1.2 kg, 1.9 kg, and 1.1 kg increase for SF-BIA, MF-BIA, and DEXA respectively). CONCLUSIONS: One week of creatine supplementation caused an increase in TBW that was detected by MF-BIA. Changes in body composition that occurred due to the increase in TBW were detected as an increase in FFM measured by SF-BIA, MF-BIA, and DEXA. These findings support the idea that the use of MF-BIA devices could allow individuals supplementing with creatine to better understand if increases in FFM are due to changes in TBW or muscle mass.

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