This study compared a commonly used multifrequency BIA device (InBody 770), with dual x-ray absorptiometry (iDXA), to compare total and regional body composition variables in a group of Division 1 football players. The purpose was to evaluate the accuracy and between position reliability of the data for both Total and Regional measurements. 

Methods: Players were measured on both devices minutes apart using standard protocol for DXA (normal hydration status, etc.).

Analyses: Within the whole population we compare the mean values for each total and regional body compositions measurement between each method and also examine average error between devices and whether that error was consistent across a wide range of body types. Finally we compared the regional mean differences and the range of differences between position groups.

Results: Compared to a Gold Standard method such as DXA, mfBIA significantly underestimated total and regional fat mass and over estimated Fat Free Mass (primarily muscle but also bone). Importantly there was a significantly wide range of error both within and between positions, suggesting that the values are not consistently biased. The range of overestimation was over 20 lbs for some regional measurements.

Conclusions: The accuracy of total and regional body composition measured by BIA is low suggesting that comparisons should not be made between players, even at the same position. Given the wide range of bias within and between positions, if significant weight changes have occurred it is possible that the data may be less reliable for the same person. Caution should be used when using mfBIA for tracking body composition within football players. The large body types compared to a normal population likely influences this variance.

Key take home messages:

• Multifrequency BIA does not appear to provide an accurate measurement of total and regional body composition in Football Players. 
• The total measures were slightly more accurate than the regional measurements, with significantly high over and underestimation within and between players.
• There appears to be a bias in the assessment with larger inaccuracies (in each direction) as players get larger.
• The wide range in differences between devices, even within position, suggests that mfBIA data should not be used to compare players to other players. It also suggests that if there is a significant change in weight the data (change over time) may be less reliable.

Practical Implications:

BIA is a widely used method for assessing body composition, because of its quick measurement time. However, caution should be take with interpretation of the data. The accuracy across a variety of body types is low for both the total, but in particular the regional measurements. Values should not be compared between players even at the same position. Future studies should evaluate the accuracy in other athletes.

Limitations: This study had a relatively small number of players at each position, which likely influenced the statistical significance of some of the comparisons. Additionally we do not have multiple measurements over time to assess the reliability of the methods in this population. However, given the influence of body size on the accuracy, large changes in mass may not be as reliable as those with little to no weight gain.

The full article can be obtained from the link below: