ESTIMATION OF BODY FAT AND MUSCLE MASS IN ELITE YOUNG SOCCER PLAYERS

Abstract

925 This study was designed to analyse the validity of selected field methods to estimate muscle mass (MM) and body fat (BF) in elite young soccer players. Subjects were 19 players of the Portuguese National Team (age, 16.0 ± 0.18 yrs; height, 174.5±4.8 cm; weight, 67.5±6.3 kg; training experience, 5.9 ± 1.9 yrs; weekly training, 7.9±1.4 hours). Dual energy x-ray absorptiometry (DXA, Hologic 1500, Waltman, USA, pencil beam mode, software version 5.67) was used as the criterion method for MM and BF assessment. MMDXA was computed according to the Heymsfield et al (1990) method. The field methods to estimate MM and BF were the Martin et al (1990) and Slaughter et al (1988) models, respectively. Forearm, midthigh and calf circumferences, and triceps, midthigh, and calf skinfolds were measured to be included in the prediction models. As assessed by a regression analysis, the relationship between MMDXA and MMMartin was defined by the following calibration equation Y(MMDXA)=9.65+0.525(MMMartin) R2=0.68 (p<0.05) and SEE=1.7 kg, while the FMDXA and FMSlaughter relationship was specified as Y(FMDXA)=1.61+0.835 (FMSlaughter) R2=0.90 (p<0.05) and SEE=0.97 kg. As assessed by a paired t-test, the differences between MMDXA and MMMartin (32.5±2.94 vs. 43.6±4.6 kg) and between BFDXA and BFSlaughter (5.92±2.99 vs.9.01±3.49 kg) were statistical significant (p<0.01). With a Bland & Altman analysis, there was poor agreement between MMDXA and MMMartin (mean difference of −11.1±1.96 SD −5.7 to −16.5 kg), and BFDXA and BFStaughter (mean difference of −3.1±1.96 SD −0.9 to −5.2 kg). Thus compared to DXA, both field methods substantially overestimated MM and BF. In order to estimate MM and FM in elite young soccer players, other practical alternatives need be developed and validated.