Background <p>The evaluation of bio impedance analysis-derived data is gaining attention as a safe, practical, and noninvasive method. Although phase angle (PhA) calculated from bio impedance analysis has been reported to be associated with performance in various sports, and a cross-sectional study has demonstrated differences in PhA between injured and uninjured athletes, no prospective studies focusing on the association between PhA and muscle injuries in American football players have been identified. The aim of this study was to investigate the association between PhA and muscle injury in university American football players. Through this study, we will examine the potential of PhA as a potential associative marker of the risk of muscle injury.</p> Methods <p>This study included male players from Kyoto University’s American football team. In the preseason period in July 2024, whole-body PhA and segmental PhA, upper limb, trunk, and lower limb were measured using InBody 770. A prospective study of limb muscle injuries was conducted over the subsequent 2&#xa0;months. The players were divided into injury (13) and non-injury (26) groups. The mean PhA values were compared between the two groups, and cutoff values were calculated for parameters showing significant differences.</p> Results <p>The injury group had significantly lower whole-body PhA, upper limb PhA, and lower limb PhA values than the non-injury group (<i>p</i> &lt; 0.05). Receiver operating characteristic analysis yielded cutoff values for whole-body PhA at 7.4° (Area under the curve; AUC = 0.738), upper limb PhA at 6.55° (AUC = 0.759), and lower limb PhA at 7.7° (AUC = 0.711).</p> Conclusion <p>Whole-body PhA, upper limb PhA, and lower limb PhA were associated with lower limb injuries in college American football players. PhA has demonstrated potential as a useful tool for the exploratory indicator for understanding and prevention of lower limb muscle injury.</p>