Localized bioelectric impedance parameters can predict quadriceps muscle strength, but not independently from lean soft tissue in young adults.

OBJECTIVE

To verify the relationship between muscular strength, determined by an isokinetic dynamometer, and the parameters of whole-body and localized bioelectrical impedance analysis (WB-BIA and L-BIA) in young adults of both sexes.

METHODS

This is a cross-sectional study involving 66 university students (ages 18 to 30, 41 women). Dual-energy X-ray absorptiometry (DXA) was used to determine lean soft tissue (LST in kg). Resistance (R), reactance (Xc), and phase angle (PhA) were assessed both for whole-body and localized (thigh) measurements using a 50 kHz tetrapolar unifrequency BIA device. Isometric and isokinetic peak torque (PT) and mean peak torque (PTM) during knee extension were measured using an isokinetic dynamometer.

RESULTS

LST was the variable that best explained muscular strength in both sexes (adjusted R2: ≥0.60; p < 0.001). In males, the variables WB-R, WB-Xc, and thigh Xc showed the strongest relationships with muscular strength indicators (adjusted R2: 0.25 to 0.45; p < 0.05). In females, WB-R and thigh R were the BIA parameters that showed the strongest relationships with muscular strength indicators (adjusted R2: 0.25 to 0.46; p < 0.05). Thigh R was the only parameter that independently and significantly explained the isometric PTM (β: -0.292; p = 0.029), whereas all other BIA parameters, whether whole-body or thigh-related, demonstrated dependent relationships with LST. When comparing the tertiles of LST, it was observed in both sexes that the amount of LST influenced muscular strength and the whole-body and thigh BIA parameters (p < 0.05).

CONCLUSION

In our sample, although both whole-body and localized BIA parameters showed significant relationships with muscular strength in both sexes, only thigh R in the female group was an independent predictor of LST in isometric PTM.