Key takeaways
All four BIA devices overestimated bodyfat percentage (BF%) compared with the Bod Pod reference, but the size of the error differed by brand.
InBody 120 and 270 showed the strongest relative agreement (ICC = 0.94 and 0.93), while the Accuniq BC310 was the least consistent (ICC = 0.88).
Measurement error was wide (±7–10 percentage points)—big enough to misclassify very lean athletes near the 7 % (boys) or 12 % (girls) eligibility cutoffs.
Two devices (Accuniq BC310, InBody 270) showed proportional bias, overestimating BF% in the leanest wrestlers and underestimating it in heavier peers.
Regulators should vet each device individually before approving it for weight certification programs; “one-size-fits-all” assumptions are risky.
Why the study matters
Since 1998, weight-management rules have slashed wrestling-related deaths, but they depend on accurate preseason body composition tests. DXA and hydrostatic weighing are precise yet expensive and immobile. Bioelectrical impedance analysis (BIA) scales are cheap and portable, so 27 U.S. state federations already allow at least one model. This study asked whether four readily available BIAs are trustworthy replacements for the Bod Pod (air displacement plethysmography, ADP) in 14 to 18-year-old wrestlers.
What the researchers did
A mixedgender sample of 134 adolescent wrestlers (mean 15.6 y) reported to the lab hydrated and fasted. Each athlete completed Bod Pod testing plus sequential assessments on four BIAs—Accuniq BC310, InBody 120, InBody 270, and Tanita TBF300WA plus—all within 90 minutes. Reliability (ICC) and error (SEM, BlandAltman limits) were calculated against the Bod Pod benchmark.
What the discussion means for coaches & clinicians
Precision vs. safety tradeoff: High ICCs (>0.88) look impressive, yet a ±7–10 % error band can blur the line between legal and illegal weight classes. A male wrestler truly at 6 % BF might test at 8 % on one device and be cleared to lose more weight, increasing health risk.
Devicespecific vetting is essential. The two InBody units performed similarly and acceptably, but the Accuniq’s larger bias and dispersion argue against blanket approval of “any BIA.” Governing bodies should demand validation data for the exact model they intend to use.
Proportional bias complicates lean athletes’ assessments. Because Accuniq BC310 and InBody 270 overestimate BF% most in the lightest wrestlers, they may falsely reassure coaches that an athlete has “room to cut.” Conversely, heavier wrestlers may be allowed an unrealistically low target weight.
ADP is not flawless either. Its own error range overlaps those of the BIAs, reminding practitioners that all indirect methods carry uncertainty. Multiple assessments or confirmation with a different technique may be warranted for borderline cases.
Practical recommendations
Use the InBody 120 (or 270) if ADP or DXA isn’t feasible, but build a ±8 % safety cushion into eligibility decisions.
Retest lean athletes (<9 % boys; <14 % girls) on a second day or with a different method before certifying weight loss goals.
Train staff to interpret limits of agreement, not just average bias, so they understand why a single number can mislead.
Advocate for ongoing validation studies as new BIA firmware and algorithms appear.
Bottom line: BIA technology offers a convenient gateway to safer weight management in scholastic wrestling—but only when coaches and regulators respect its builtin uncertainty and select devices backed by solid, modelspecific evidence.
Full Article:
Montgomery, M., Marttinen, R., Galpin, A. (2017). Comparison of body fat results from 4 bioelectrical impedance analysis devices vs. air displacement plethysmography in American adolescent wrestlers. International Journal of Kinesiology and Sports Science, 5(4), 18-25. http://dx.doi.org/10.7575/aiac.ijkss.v.5n.4p.18
This blog post was written with the assistance of AI to support clarity and accessibility. It is intended to help disseminate and discuss research findings with a broader audience. However, for the most accurate and reliable information—including conclusions and practical applications—please refer to the original peer-reviewed publication on which this blog is based. The peer-reviewed article remains the most authoritative source.