Phase angle as an indicator of health and fitness in patients entering an exercise referral scheme

The loss of function as we age may be related to changes at the cellular level. Recently, attention has been given to measurement of the phase angle (PhA); a noninvasive simple measure using bioelectrical impedance analysis (BIA). Indeed, PhA is considered a valuable indicator of cellular health and, as it is derived purely from electrical properties of the tissue, it avoids typical concerns associated with BIA using prediction equations. PhA is calculated from the arctangent of the ratio between the resistance and reactance from BIA, and a number of studies have evidenced its associations with age and sex, lean body mass, and strength.