The purpose of this study was to investigate whether the voluntary neural drive and the excitability of the reflex arc could be modulated by training, even in old age. To this aim, the effects of a 16-wk strengthening program on plantar flexor voluntary activation (VA) and on the maximum Hoffman reflex (H_max)-to-maximum M wave (M_max) ratio were investigated in 14 elderly men (65–80 yr). After training, isometric maximum voluntary contraction (MVC) increased by 18% ( P < 0.05) and weight-lifting ability by 24% ( P < 0.001). Twitch contraction time decreased by 8% ( P < 0.01), but no changes in half relaxation time and in peak twitch torque were observed. The VA, assessed by twitch interpolation, increased from 95 to 98% ( P < 0.05). Pretraining VA, also evaluated from the expected MVC for total twitch occlusion, was 7% higher ( P < 0.01) than MVC. This discrepancy persisted after training. The interpolated twitch torque-voluntary torque relationship was fitted by a nonlinear model and was found to deviate from linearity for torque levels >65% MVC. Compared with younger men (24–35 yr), the H_max- to M_max ratio and nerve conduction velocity (H index) of the older group were significantly lower (42%, P < 0.05; and 29%, P < 0.001, respectively) and were not modulated by training. In conclusion, older men seem to preserve a high VA of plantar flexors. However, the impaired functionality of the reflex pathway with aging and the lack of modulation with exercise suggest that the decrease in the H_max- to M_maxratio and H index may be related to degenerative phenomena.

To evaluate predictors of non-alcoholic fatty liver disease (NAFLD) in obese children. Cross-sectional study. Two hundred and sixty-eight obese children not consuming alcohol and without hepatitis B or C were consecutively studied at an auxology clinic. Alanine aminotransferase (ALT), aspartate aminotransferase (AST), gamma-glutamyl-transferase (GGT), cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, triglycerides, uric acid, glucose, glucose during oral glucose tolerance testing (OGTT), insulin, insulin during OGTT, insulin resistance as estimated by homeostasis model assessment (HOMA), C-reactive protein (CRP), and systolic and diastolic blood pressure were measured. Fatty liver was diagnosed by ultrasonography using standard criteria. Univariable and multivariable logistic regression was used to evaluate predictors of NAFLD. All predictors except gender and pubertal status were modeled as continuous variables. NAFLD was detected in 44% of obese children. At univariable analysis, male gender, Z-score of body mass index (BMI) (Z-BMI), ALT, AST, GGT, triglycerides, uric acid, glucose, glucose during OGTT, insulin, insulin during OGTT, HOMA, CRP and systolic blood pressure were predictors of NAFLD, whereas HDL-cholesterol and late-pubertal status were predictors of the normal liver. At multivariable analysis, however, only Z-BMI, ALT, uric acid, glucose during OGTT and insulin during OGTT were independent predictors of NAFLD. Z-BMI, ALT, uric acid, glucose during OGTT and insulin during OGTT are independent predictors of NAFLD in Italian obese children, with most of the prediction explained by ALT and Z-BMI. Centro Studi Fegato and Progetti di Ricerca Corrente, Istituto Auxologico Italiano.

Objective: To measure body water distribution and to evaluate the accuracy of eight-polar bioelectrical impedance analysis (BIA) for the assessment of total body water (TBW) and extracellular water (ECW) in severe obesity. Design: Cross-sectional study. Setting: Obesity clinic. Subjects: In all, 75 women aged 18–66 y, 25 with body mass index (BMI) between 19.1 and 29.9 kg/m² (ie not obese), 25 with BMI between 30.0 and 39.9 kg/m² (ie class I and II obese), and 25 with BMI between 40.0 and 48.2 kg/m² (ie class III obese). Methods: TBW and ECW were measured by ²H₂O and Br dilution. Body resistance (R) was obtained by summing the resistances of arms, trunk and legs as measured by eight-polar BIA (InBody 3.0, Biospace, Seoul, Korea). The resistance index at a frequency of x kHz (RI_x) was calculated as height ²/R_x. Results: ECW : TBW was similar in women with class III (463%, means.d.) and class I–II obesity (453%) but higher than in nonobese women (393%, P<0.05). In a random subsample of 37 subjects, RI₅₀₀ explained 82% of TBW variance (P<0.0001) and cross-validation of the obtained algorithm in the remaining 38 subjects gave a percent root mean square error (RMSE%) of 5% and a pure error (PE) of 2.1 l. In the same subjects, RI₅ explained 87% of ECW variance (P<0.0001) and cross-validation of the obtained algorithm gave a RMSE% of 8% and a PE of 1.4 l. The contribution of weight and BMI to the prediction of TBW and ECW was nil or negligible on practical grounds. Conclusions: ECW : TBW is similar in women with class I–II and class III obesity up to BMI values of 48.2 kg/m². Eight-polar BIA offers accurate estimates of TBW and ECW in women with a wide range of BMI (19.1–48.2 kg/m²) without the need of population-specific formulae. Sponsorship: Progetti di Ricerca Corrente, Istituto Auxologico Italiano.