Effects of an Eight-Week Mindfulness-Based Intervention on Serum Cortisol Levels in Female University Basketball Players: A Quasi-Experimental Study

Abstract

Background: Cortisol, the primary glucocorticoid secreted via the hypothalamic-pituitary-adrenal (HPA) axis, serves as a well-established biomarker of physiological stress in competitive athletes. Female university basketball players are particularly susceptible to chronic stress owing to the convergence of intensive training demands, competitive pressures, and academic obligations. Objective: This study examined whether an eight-week structured mindfulness-based intervention (MBI) would significantly reduce morning serum cortisol levels in female university basketball players. Methods: Employing a quasi-experimental pre-test/post-test control group design, 30 female university basketball players (aged 18–25 years) were randomly allocated to an Experimental Group (n = 15) that received the MBI alongside regular training, and a Control Group (n = 15) that continued routine training only. Serum cortisol was assayed at 08:00 h at both assessment points using the Elecsys Cortisol II immunoassay analyzer (Roche Diagnostics). Within-group changes were evaluated via paired-samples t-tests; between-group post-intervention differences were assessed using independent-samples t-tests (α = 0.05). Results: The Experimental Group demonstrated a statistically significant reduction in serum cortisol from pre-test (M = 10.50 nmol/L, SD = 1.89) to post-test (M = 8.35 nmol/L, SD = 1.54), representing a 20.5% decline (t(14) = −11.422, p < .001). The Control Group exhibited no meaningful change over the same period (t(14) = 1.139, p > .05). Post-intervention between-group comparisons confirmed significantly lower cortisol concentrations in the Experimental Group relative to controls (t(28) = −2.361, p < .05). All values remained within the established morning reference range (6.2–19.4 nmol/L). Conclusion: An eight-week mindfulness-based intervention produced measurable, biologically meaningful reductions in physiological stress among female university basketball players. These findings support the integration of structured mindfulness training into university-level sports programs as a cost-effective strategy for optimizing athlete wellbeing and recovery.