Evaluation of body composition in athletes

The aim of this study is to evaluate bioimpedance (BIA) changes in a group of athletes in performing isometric training. BIA was evaluated in 10 competitive athletes (ATL, age 22.3+/-3.2 years; weight 75.0+/-7.5 kg; height 172+/-5 cm; BMI 25.4+/-1.6 kg/m(2)), and 10 young men (controls), not engaged in any specific physical activity (CTR: age 22.7+/-2.8 years; weight 73.4+/-10.0 kg; height 174+/-4 cm; BMI 24.4+/-3.9 kg/m(2)). BIA was assessed on the whole body (total BIA), and separately for upper and lower limbs and trunk (segmental BIA) for the following: a) phase angle (AF) to 50 kHz; b) impedance (Z) at 100 kHz and at 5 kHz, from which the Z100/Z5 ratio was calculated. BIA index (height(2)/Z at 50 kHz) was considered as the expression of total body water between intracellular and extracellular fluid. A significant increase in total body BI index and AF was observed, together with a decrease in the Z100/Z5 ratio. Segmental BIA showed analogous differences between the two groups, especially in relation to upper limbs. Despite the strong correlation between AF and Z100/Z5, the two qualitative parameters are not totally comparable for identifying intergroup differences. In conclusion, isometric exercise, with increased muscle tissue, typical of these athletes, yields significant variations in quantitative (BI index) and qualitative (AF and Z100/Z5) BIA which represent the increase in total body water and the intracellular water/extracellular water ratio, respectively.