measurement of body composition has become an important component in the diagnosis of health, physical conditioning and nutritional status. The aim of this study was to compare two methods of detecting body composition, bioelectrical impedance and air displacement plethysmography for athletes and non-athletes. Specifically, we compared the parameters as fat mass, fat free mass and the value of basal metabolic rate. A sample size of 52 men (age 26.2 ± 5.4 years) that included a group of mixed martial arts (MMA) fighters (n = 31, age 27.2 ± 5.5 years) and a group of the non-athletes (n =21, age 24.6 ± 5.1 years). Both groups were measured by bioelectrical impedance and air displacement plethysmography. Significant differences in % body fat (p<0.05) and fat-free mass (p<0.05) were noted between bioelectrical impedance and air displacement plethysmography of non-athletes, but there were no significant differences for athletes. Furthermore, there was a significant difference (p<0.001) of basal metabolic rate between bioelectrical impedance and air displacement plethysmography, but the correlation with fat free mass was very strong for both methods. Therefore, the use of bioelectrical impedance and air displacement plethysmography may be useful for detecting changes in body composition, but their accuracy is controversial and for this reason we recommend using only one method and not combining them.
KEY WORDS: Body composition; Bioelectrical impedance; Plethysmography; Body fat; Basal metabolic rate.