Associations of cardiac autonomic modulation and urinary adrenal hormones with marathon finishing time in middle-aged male athletes

Background The autonomic nervous and endocrine systems are involved in the physiological adaptation to exercise, and in experimental settings both the sympathovagal balance and the adrenal function are associated with athletic performance. In this real-life field study, the association between non-invasive markers of cardiac autonomic modulation, urinary adrenal hormone levels, and marathon finishing time in middle-aged Caucasian male athletes was investigated. Methods A prospective study was conducted in male marathon runners aged ≥30 years. Continuous single-lead electrocardiographic (ECG) recordings were obtained using a wearable chest device from the day before the marathon until after its completion. Urinary adrenal hormone levels were measured before and after the race. Univariate linear regression analyses were performed to correlate general characteristics, nocturnal heart rate variability (HRV) parameters, and hormonal parameters with marathon finishing time. A multivariable model was then applied including age, body mass index (BMI), and training hours. Results 104 athletes were enrolled in the study and 73 (median age 48 years, interquartile range = 16) had adequate data quality for the final analysis. Several HRV parameters correlated with better performance at univariate analysis; lower minimum nocturnal heart rate and vagal predominance, expressed as higher 2 Like Variations (2LV) values remained independently associated with shorter finishing time. Among hormonal variables, the post-/pre-race ratio of urinary normetanephrine hourly output and cortisol/cortisone ratio remained significant at multivariable analysis. Only BMI, but not age and training history, remained significant in a model integrating HRV and hormones. Conclusions Under real-world marathon conditions, specific HRV indices and endocrine markers showed promising value as indicators of physiological readiness with endurance exercise in male master athletes.