Fat-free Mass Characteristics of Muscular Physique Athletes
Purpose Simple body composition models, such as two-compartment models, employ assumptions which may be violated in specific athletic populations (e.g. the constancy of fat-free mass density [DFFM] and hydration [TBW:FFM]). The present analysis examined FFM characteristics of muscular physique athletes.
Methods Twenty-six athletes (16 M: 94.5±9.9 kg, 12.2±4.2 %fat; 10 F: 63.8±5.7 kg, 19.7±4.9 %fat) completed duplicate assessments of dual-energy x-ray absorptiometry (DXA), bioimpedance spectroscopy (BIS), and single- and multi-frequency bioelectrical impedance analysis (SFBIA; MFBIA). FFM was calculated via 5-compartment (5C) model, and FFM characteristics (i.e. DFFM, TBW:FFM, FFM mineral, FFM protein) were compared between sexes and between the sample and reference values (RV) from cadaver analysis. TBWBIS:FFM5C was designated as the reference TBW:FFM model, and alternate models were produced using BIS, MFBIA, SFBIA, impedance-based equations, and DXA output.
Results Males had lower TBW:FFM and FFM mineral, but higher FFM protein than females (p<0.05). DFFM was significantly lower than RV in males (1.096±0.006 g/cm3, RV: 1.103±0.013 g/cm3; p<0.001) and appeared higher in females (1.093±0.012 g/cm3, RV: 1.087±0.021 g/cm3; p=0.17). TBW:FFM did not differ from RV in females (75.3±4.0%, RV: 75.7±4.4%; p=0.74) or males (72.7±1.9%, RV: 72.7±3.1%; p=0.97). FFM mineral was lower than RV in males (5.5±0.4%, RV: 6.8±0.8%; p<0.001) and higher in females (6.5±0.5%, RV: 6.1±0.8%; p=0.04). FFM protein was significantly greater than RV in males (21.9±1.8%, RV: 20.6±2.6%; p=0.014), but the difference from RV in females was not statistically significant (18.3±4.1%, RV: 17.1±4.5%; p=0.39). Alternate TBW:FFM models varied substantially in their agreement with RV.
Conclusions FFM characteristics were shown to differ between male and female physique athletes. These results may have implications for optimal body composition assessment methods when atypical physique characteristics are present.
Autor / Fonte:Grant M Tinsley, Austin J Graybeal, M Lane Moore, Brett S Nickerson Medicine and Science in Sports and Exercise 2018 August 7