Hair cortisol is a physiological indicator of training stress for female footballers.

Purpose: Chronic physical stress in female athletes can reduce mental health and athletic performance. Therefore, a chronic physical stress assessment method is required.

Methods: This study examined whether hair cortisol concentration (HCC) predicted chronic physical stress changes in female university football players. We took measurements in August and December, just before the Japan college national tournament.

Results: Self-reported training load was significantly positively correlated with HCC. Self-reported training load had no significant relationship with fatigue as measured by the Profile of Mood States 2nd Edition or with the stressors from the Stressor Scale for College Students. HCC was negatively correlated with reaction time in the spatial Stroop task, although the repeated correlation analysis showed no significant relationship.

Conclusion: These results suggest that the chronic physical stress experienced by female footballers cannot be predicted by psychological indicators; however, they can be predicted by HCC, which could be used to prevent overtraining in these athletes.