(68) COMPARING NOVEL AND TRADITIONALLY CALCULATED SYMPATHETIC HRV MARKERS BEFORE AND AFTER MAXIMAL EXERCISE

Purpose: Heart rate variability (HRV) is a valuable tool for assessing autonomic nervous system function and recovery processes in athletes. The Poincaré plot indices, including the standard deviation of instantaneous beat-to-beat variability (SD1) and the standard deviation of long-term RR interval variability (SD2), are used to calculate the stress score (SS) and sympathetic-to-parasympathetic ratio (SPS), which reflect sympathetic activity and autonomic balance, respectively. However, deriving these indices requires specialized software and extended recording periods, limiting their practicality in field settings. This study aimed to 1) develop a modified stress score (MSS) and a modified sympathetic-to-parasympathetic ratio (MSPS) using ultrashort time-domain HRV metrics as proxies for SS and SPS and 2) evaluate their responses to acute maximal exercise in competitive athletes. Methods: Twenty male collegiate athletes (age = 21.2 ± 2.1 yrs, height = 183.6 ± 8.9 cm, weight = 79.2 ± 10.3 kg, VO2max = 52.0 ± 8.6 ml.kg-1.min-1) performed a maximal graded treadmill exercise test (GXT). Heart rate and rhythm were assessed using electrocardiography (ECG) for 10 minutes before and 30 minutes after each GXT. SD1 and SD2 were derived at minutes 5–10 pre-exercise (PRE), minutes 5–10 post-exercise (POST1), and minutes 25–30 post-exercise (POST2). These values were used to calculate SS and SPS. Ultrashort time-domain HRV metrics, root mean square of successive differences (RMSSD) and standard deviation of normal-to-normal intervals (SDNN) were extracted from the first minute of each of the above mentioned 5-minute epochs to calculate MSS and MSPS. Results: SS and MSS were positively correlated at PRE (r = 0.94, p < 0.001), POST1 (r = 0.92, p < 0.001), and POST2 (r = 0.87, p < 0.001). Similarly, SPS and MSPS were positively correlated at PRE (r = 0.94, p < 0.001), POST1 (r = 0.92, p < 0.001), and POST2 (r = 0.93, p < 0.001). Both the traditional (SS and SPS) and modified (MSS and MSPS) metrics followed similar trends over time, with values increasing from PRE to POST1 (p < 0.05), decreasing from POST1 to POST2 (p < 0.05), yet remaining significantly higher than PRE (p < 0.05).
Conclusions: The results indicate that ultrashort time-domain HRV indices serve as convenient proxies for the Poincaré plot method in assessing sympathetic overdrive in response to maximal exercise. Practical Applications: The simplified acquisition methods of MSS and MSPS make them valuable for daily recovery assessments and training readiness evaluations. This modified approach enhances real-time athlete monitoring and informs training decisions in applied settings. Acknowledgements: None