Phase Angle Is More Strongly Associated with Peak Oxygen Uptake than Skeletal Muscle Mass Percentage in Healthy Young Adults: A Cross-Sectional Study

Regular assessment of aerobic capacity is important in sports medicine and preventive health; however, cardiopulmonary exercise testing (CPX) is often impractical in field or clinical settings. Phase angle (PhA), derived from bioelectrical impedance analysis (BIA), has been proposed as a practical indicator of cellular health and membrane integrity; however, its relevance to aerobic capacity relative to skeletal muscle mass percentage (SMM%) in healthy young adults remains unclear. This cross-sectional study investigated the independent associations of PhA and SMM% with peak oxygen uptake (VO2peak) and oxygen uptake at the anaerobic threshold (VO2AT). Forty-one adults underwent same-day BIA and CPX using a cycle ergometer. VO2peak was obtained from 37 participants who achieved maximal effort, while VO2AT was identified in all. In multiple regression analyses adjusted for sex, PhA was independently associated with both VO2peak and VO2AT, whereas SMM% showed no independent association. These findings indicate that PhA may serve as a stronger determinant of aerobic capacity than SMM% in healthy young adults and highlight its potential utility in settings such as routine health check-ups or preliminary screening of aerobic capacity when CPX is impractical.