Precision Error in Dual-Energy X-Ray Absorptiometry Body Composition Measurements in Elite Male Rugby League Players

Abstract

Body composition analysis using dual-energy X-ray absorptiometry (DXA) is becoming increasingly popular in both clinical and sports science settings. Obesity, characterized by high fat mass (FM), is associated with larger precision errors; however, precision error for athletic groups with high levels of lean mass (LM) are unclear. Total (TB) and regional (limbs and trunk) body composition were determined from 2 consecutive total body scans (GE Lunar iDXA) with re-positioning in 45 elite male rugby league players (age: 21.8 ± 5.4 yr; body mass index: 27.8 ± 2.5 kg m(-1)). The root mean squared standard deviation (percentage co-efficient of variation) were TB bone mineral content: 24g (1.7%), TB LM: 321 g (1.6%), and TB FM: 280 g (2.3%). Regional precision values were superior for measurements of bone mineral content: 4.7-16.3 g (1.7-2.1%) and LM: 137-402 g (2.0-2.4%), than for FM: 63-299 g (3.1-4.1%). Precision error of DXA body composition measurements in elite male rugby players is higher than those reported elsewhere for normal adult populations and similar to those reported in those who are obese. It is advised that caution is applied when interpreting longitudinal DXA-derived body composition measurements in male rugby players and population-specific least significant change should be adopted.

Longitudinal Changes in Body Composition Assessed Using DXA and Surface Anthropometry Show Good Agreement in Elite Rugby Union Athletes

“…For this reason, anthropometry regression equations were not used to assess change, instead utilising the S7SF as a comparison measure. This study found strong linear associations between the methodologies when assessing change in FM, with the S7SF able to predict the direction of change 83% of the time, or 91% when DXA FM change >1kg, which is approximately the threshold for least significant change previously reported in a similar population (Barlow et al, 2015). Despite this, the relative changes estimated by S7SF will be 4.6-7.0% different in magnitude from those measured by DXA, potentially due to questions raised about the reliability of DXA for assessing FM, particularly in lean individuals (Prior et al, 2001;Toombs et al, 2012;Van Der Pleog et al, 2003;Williams et al, 2006).…”

“…The findings suggest that the LMI may not be able to detect small changes in FFM (<1.6% or ~1.5 kg in this population), and may be slightly less reliable for backs. However, in the majority of cases (83%) the LMI was able to indicate the change in direction of DXA FFM when changes were >1 kg, which is approximately the threshold for least significant change for DXA previously proposed in rugby union athletes (Barlow et al, 2015).…”

Effect of Hand Positioning on DXA Total and Regional Bone and Body Composition Parameters, Precision Error, and Least Significant Change

“…The precision error findings for total body lean and fat mass derived using both hand positioning protocols are within ISCD recommended ranges (12) and are similar to those reported by other studies in men athletes (LM 0.21 kg, 0.3%; FM 0.17 kg, 1.5 %) (18), senior rugby league players (LM 0.36 kg, 2.4%; FM 0.33 kg, 2.9 %) (19) and normal (LM 0.22 kg, 0.5%; FM 0.18 kg, 1.0%, LM 0.24 kg, 0.5%; FM 0.20 kg, 0.8%) (20,21). Precision error should be reported for both RMS SD and %CV though, highlighted by Carver and co-workers whose study in obese subjects reported similar %CV values (LM 1.0% and FM 0.9%), with reported RMS SD values at a factor of three higher than the studies cited above (22).…”

Validation of Field Methods to Assess Body Fat Percentage in Elite Youth Soccer Players

“…populations [1,3], DXA is now widely accepted as a practical criterion method for assessing fat mass in athletes [33]. However, there are logistical and financial costs associated with DXA measurements that might prevent its frequent use in sports settings.…”