Whole body and regional phase angle as indicators of muscular performance in athletes

Bioelectrical impedance analysis (BIA)-derived phase angle (PhA) has been used to assess cellular health in various populations, but its usefulness as a tool for measuring muscular performance in adult athletes has not been extensively investigated. Our investigation examined the association of whole-body (WB) PhA with muscular performance in 117 adult athletes from different sports and additionally assessed whether regional PhA was a better indicator of muscular performance compared to WB, while accounting for lean soft tissue (LST). Muscular performance was assessed with handgrip strength and countermovement jump power. WB and regional PhA and LST were obtained by BIA and dual-energy x-ray absorptiometry, respectively. Multiple linear regression was used to model outcomes, while adjusting for LST. WB PhA was positively associated with relative power and relative and absolute strength (p < 0.05), irrespective of LST. Regional PhA measures explained similar amounts of variance in absolute and relative power and strength as that of WB PhA after accounting for age, sex, height, and sport type (lower limb adj R² = 0.42, 0.60 for power; upper limb adj R² = 0.38, 0.74 for strength; WB adj R² = 0.44, 0.63 and 0.38, 0.75 for power and strength, respectively). Only upper limb PhA was related with strength (p < 0.05) after accounting for upper limb LST. PhA may have the potential to be used as a marker of functional muscle mass, which is important when it comes to assessing muscular performance of athletes. Regional measures of PhA do not provide a better indicator of regional strength or power when compared to WB PhA.