Identification and Longitudinal Monitoring of Physiological Response Profiles in Wrestlers Using Multivariate Heart Rate Variability Analysis

Heart rate variability (HRV) is a noninvasive marker of cardiac autonomic regulation, suitable for use in monitoring training adaptation and recovery in athletes. Group-level analyses may mask significant interindividual variability in responses to the same training stimulus if changes are divergent. This study investigated whether competitive wrestlers exposed to a standardized training protocol exhibit different multivariate patterns of cardiac autonomic response. Their evolution during a four-month training period was also investigated. Holter recordings were obtained before and immediately after training, with assessments performed at five measurement points. Temporal, frequency, nonlinear, and fractal parameters of HRV were analyzed. Individual percent changes before and after training were assessed using inferential and correlation analysis, principal component analysis (PCA), and hierarchical clustering. Two distinct physiological response profiles were identified. The predominant profile is characterized by increased heart rate and decreases in RMSSD, SDNN, SampEn, and other vagally mediated HRV indices. A smaller subgroup shows the opposite response pattern with preserved or increased variability. The profiles are differentiated by changes in RMSSD, SDNN, and LF/HF. The first two principal components explain 80.53% of the total variance. Hierarchical clustering and cluster quality indicators support multivariate separation. Longitudinal assessment shows that contrasting profile-specific directions of response remain distinguishable during the four-month training period. The magnitude of several acute HRV responses is observed to change over time. Identical training stimuli can elicit different cardiac autonomic responses among wrestlers. The study supports longitudinal HRV profiling as a complementary approach for individualized athlete monitoring and training response assessment.