Background
Body composition (BC) and its changes over time may influence performance in soccer players. BC assessment techniques are mainly based on quantitative evaluation, originating from model-based indirect estimates of Fat-Free Mass and Fat Mass. DXA, particularly the advanced iDXA technology, is considered to be precise enough for this kind of assessment. On the other hand, Bio Impedance Vector Analysis (BIVA) allows the direct assessment of athletes’ body composition from impedance vector (Z vector), irrespective of body weight, prediction models or hydration assumptions and may classify qualitative changes in soft tissues hydration. The objective of this study was to investigate, compare, and integrate seasonal variations of soft tissues (assessed with DXA and BIVA) in elite soccer players, playing in the Italian top level championship (national major league).