Assessment of body fat proportion by means of bioelectrical impedance in athletic boys aged 7 to 18 years with respect to specific types of instruments

BACKGROUND: Bioelectrical impedance (BIA) seems an appropriate method for basic diagnostics of body composition in a practical environment. This is a non-time consuming non-invasive method that provides a high degree of response relevance. However, the values identifi ed by the BIA method are susceptible to a number of factors, which need to be taken into account during the investigation stage and interpretation of the results. One of the signifi cant factors infl uencing the outcomes of measurement is the instrument factor.<br />OBJECTIVE: The objective of the present comparative survey was to analyse the proportions of body fat by means of the BIA hand-to-leg method and BIA leg-to-leg method in a sample of athletic individuals aged 7 to 18 years.<br />METHODS: The survey included a total of 178 ice-hockey players aged 7 to 18 years. The proportion of body fat analysed by means of the BIA hand-to-leg method was measured by the Tanita BC-418 MA instrument. For the purposes of the BIA leg-to-leg method the Tanita BF-350 instrument was used (Tanita, Japan). Both instruments work at a frequency of 50 kHz.<br />RESULTS: The percentage of body fat established by the BIA leg-to-leg method (M = 13.5%; SD = 4.8) indicated signifi cantly lower values of fat percentage than the values measured by the BIA hand-to-leg method (M = 17.1%; SD = 4.3). The overall diff erence represents an average value of 3.6% (standard mode; p &lt; .001; d = 0.8). Regarding the monitored age categories the observed diff erences are in the range of 3.1&#8211;4.7% (p &lt; .001; d = 0.7&#8211;1.2).<br />CONCLUSION: The present study compares the proportions of body fat by means of the BIA leg-to-leg method and BIA hand-to-leg method in athletic boys aged 7 to 18 years. The results measured by the BIA leg-to-leg method signifi cantly undervalue the proportion of body fat in comparison with the BIA hand-to-leg method. The instrument factor and age factor represented signifi - cant variables infl uencing the results of the measurement. The present fi ndings can be used in medical and sports practice in selecting economically more accessible instruments for assessing body composition by the BIA leg-to-leg method. For research purposes the authors rather recommend the a pplication of the BIA hand-to-leg multi-frequency instruments