A comparative analysis of the accuracy of body fat measurements using spectrophotometry, bioelectrical impedance and anthropometric technique vs. air displacement plethysmography in a group of powerlifters

Abstract

Background. The analysis of athletes’ body composition is particularly important for planning nutrition and training loads. Reproducibility and precision of measurements are particularly important in strength sports, when there are fluctuations in the body mass and composition around training. Precise monitoring of these changes with an adequate method enables prediction of the effects of inadequate diet or workload. The aim of the study was to assess body fat (%Fat) measurements with spectrophotometry (NIR), bioelectrical impedance (BIA) and the anthropometric technique (SF) and to compare them with air plethysmography (BP) as a reference method in a group of powerlifters. Material and methods. The study was conducted simultaneously on a group of 49 men aged 19– 26 years, practising classic powerlifting. The body fat content was measured with the Bod Pod (BP method), FUTREX 6100A/ZL (NIR method), Tanita MC 780 MA (BIA method), whereas skin thickness was measured with a Harpenden skinfold calliper (SF technique). Results. The total measurement accuracy coefficient for %Fat was 100% with BIA, 94% with SF and 74% with NIR, as compared with the reference method. In the group with the body fat content ≤ 20% (L-Fat-P) and > 20% (H-Fat-P) the accuracy coefficients were respectively 117 vs. 86% (BIA), 105 vs. 82% (SF) and 84 vs. 63% (NIR). The total correlation coefficients between the methods under analysis and the reference method were significant: 0.70 (SF), 0.61 (BIA), 0.43 (NIR). In the L-Fat-P group there was a significant correlation between the BP and SF methods (0.52), and in the H-Fat-P group – between the BP and BIA methods (0.53). There were relative differences in the total group, L-Fat-P and H-Fat-P between the BP and NIR methods: –20.7% and –9.2% vs. –37.1%, the BIA method: 8.9% and 23.6% vs. –14.2%, and the SF technique: –0.6% and 9.8% vs. –17.1%, respectively. Conclusions. The results indicated the need to select carefully the techniques analysing athletes’ body composition. Fat percentage measurement with the anthropometric technique was the most accurate; it was moderately overestimated when the bioelectrical impedance method was applied, whereas the spectrophotometric method resulted in significant underestimation. The accuracy of the measurements depended on the body fat content. In the future it is necessary to conduct research on endurance athletes as well as people who do not practise sports.