Association between Handgrip Strength and Raw BIA Variables in Adolescents Aged 14-17 Years

Raw BIA (bioelectrical impedance analysis) variables such as phase angle (PhA) or impedance ratio (IR=the ratio between impedance-Z at high frequencies and Z at low frequencies), are both thought to be a proxy of muscle quality in terms of water distribution (ECW/ICW ratio), body cell mass and cellular integrity. So far, few studies have tested the relationship between handgrip strength (HGS) and body composition in adolescents. Our study aimed to analyze the variability in raw BIA variables and their association with HGS in 117 male (age 15.7 +/- 0.8 years, stature 171.8 +/- 7.3 cm, body weight 65.8 +/- 10.6 kg, standardized body mass index=BMI-SDS +0.57 +/- 0.9) and 130 female adolescents (age 16.0 +/- 0.7 years, stature 160.8 +/- 5.6 cm, weight 57.3 +/- 8.0 kg, BMI-SDS +0.38 +/- 0.9). BIA was performed for the whole body and separately for upper limbs and lower limbs, while HGS was measured to assess the isometric strength of upper limbs. HGS was significantly correlated (r>0.500) with whole-body IR and PhA, and this association was even stronger with upperlimb IR and PhA. In addition, a quite strict correlation emerged between HGS and whole-body BI index at 250 kHz (index of fat-free mass). In multiple regression analysis BI indexes along with IRs or PhAs were independent predictors of HGS, whereas gender and age were not. In conclusion, this study gives some information about the use of HGS and raw BIA variables in the first two decades of life, suggesting a new approach to assess nutritional status in prevention and public health nutrition.