Fig.1
Flow chart of the study participants included in the analysis.
Fig.2
The positions of the WIM electrodes on the left wrist and right hand during bioelectrical impedance measurement.
Fig.3
The hand-to-hand bioelectrical impedance scheme of the TTC model.
Table 1
Anthropometric, body composition and bioelectrical impedance data.
| Mean ± STD | Range | |
|---|---|---|
| Age, years | 27.02 ± 10.2 | 18 - 56 |
| TBM, kg | 69.56 ± 11.29 | 45.83 - 100.95 |
| Height, cm | 171.89 ± 8.86 | 156.0 - 196.0 |
| BMI, kg/m2 | 23.6 ± 3.97 | 18.17 - 38.87 |
| Total arms | 6109.06 ± 1505.04 | 3480.6 - 10970.2 |
| volume, cm3 | ||
| FFMDEXA, kg | 50.99 ± 10.94 | 34.51 - 86.59 |
| FMDEXA, % | 26.77 ± 9.34 | 8.32 - 48.39 |
| Re(Z)10_a, Ohm | 633.13 ± 136.83 | 366.43 - 1001.8 |
| Re(Z)10_b, Ohm | 559.43 ± 169.33 | 88.28 - 866.89 |
| Re(Z)10_c, Ohm | 627.71 ± 133.16 | 398.16 - 964.93 |
| Re(Z)50_a, Ohm | 592.86 ± 134.54 | 379.79 - 914.78 |
| Re(Z)50_b, Ohm | 551.97 ± 160.0 | 126.64 - 889.12 |
| Re(Z)50_c, Ohm | 562.21 ± 138.21 | 304.83 - 831.84 |
| Re(Z)100_a, Ohm | 571.13 ± 133.97 | 352.69 - 881.58 |
| Re(Z)100_b, Ohm | 553.53 ± 141.96 | 312.6 - 890.5 |
| Re(Z)100_c, Ohm | 527.9 ± 134.54 | 204.77 - 799.5 |
[i] * Re(Z)x_y= reactance of bioelectrical impedance measured at frequency of x kHz and with right hand position y shown in Fig. 2
Fig.4
Arm volume multiplied by TBM/FFM ratio approximates bioimpedance: (a) Approximation of InBody 230 arm impedance. (b) Approximation of real part of bioimpedance measured with WIM.
Table 2
Linear regression metrics for FFM estimation: two models (SC and TTC) and nine experimental conditions
| r2 | MAPE | Max. err. | r2 | MAPE | Max. err. | ||
|---|---|---|---|---|---|---|---|
| 10 | a | 0.656 ± 0.209 | 0.076 ± 0.016 | 15.732 ± 5.076 | 0.679 ± 0.211 | 0.075 ± 0.017 | 14.404 ± 4.756 |
| 10 | b | 0.605 ± 0.487 | 0.085 ± 0.023 | 15.088 ± 6.327 | 0.514 ± 0.37 | 0.096 ± 0.022 | 17.862 ± 6.684 |
| 10 | c | 0.777 ± 0.114 | 0.065 ± 0.012 | 12.463 ± 4.224 | 0.795 ± 0.112 | 0.064 ± 0.013 | 11.236 ± 3.888 |
| 50 | a | 0.763 ± 0.119 | 0.064 ± 0.014 | 12.493 ± 3.357 | 0.774 ± 0.125 | 0.062 ± 0.014 | 12.16 ± 3.456 |
| 50 | b | 0.479 ± 0.309 | 0.111 ± 0.309 | 27.447 ± 24.079 | 0.422 ± 0.338 | 0.119 ± 0.338 | 30.852 ± 25.537 |
| 50 | c | 0.876 ± 0.054 | 0.051 ± 0.009 | 8.623 ± 2.596 | 0.886 ± 0.051 | 0.052 ± 0.009 | 6.884 ± 1.283 |
| 100 | a | 0.752 ± 0.131 | 0.065 ± 0.014 | 12.883 ± 3.534 | 0.762 ± 0.14 | 0.064 ± 0.015 | 12.595 ± 3.507 |
| 100 | b | 0.698 ± 0.143 | 0.078 ± 0.015 | 13.653 ± 3.794 | 0.761 ± 0.133 | 0.07 ± 0.014 | 11.829 ± 2.888 |
| 100 | c | 0.482 ± 0.423 | 0.086 ± 0.02 | 20.076 ± 9.376 | 0.435 ± 0.461 | 0.094 ± 0.021 | 20.44 ± 10.855 |
Fig.5
(a) MAPE; (b) Coefficient of determination r2; (c) Maximal residual error. Distribution shapes were obtained during 100,000-sample bootstrap procedure. Bold lines show normal approximation curves; (d) The effect of sex and age variables on maximal residual error distribution for the single cylinder model.
Fig.6
Bland-Altman plots for WIM FFM estimate validation: (a) Single cylinder (SC) model: confidence intervals for the mean bias: (-0.874, 0.879) kg, for upper LOA: (4.380, 6.937) kg, for lower LOA: (-6.932, -4.375) kg; TTC model: for mean bias: (-0.920, 0.905) kg, for upper LOA: (4.547, 7.208) kg, for lower LOA: (-7.223, -4.562) kg. (b) Skinfold thickness calculations: confidence intervals for the mean bias: (-1.792, 0.955) kg, for upper LOA: (6.653, 10.651) kg, for lower LOA: (-11.488, -7.4918) kg.