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 (Profile A, n = 55) is characterized by increased heart rate and decreases in RMSSD, SDNN, SampEn, and other vagally mediated HRV indices. A smaller subgroup (Profile B, n = 10) 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, providing a low-dimensional representation of the multivariate response structure. Hierarchical clustering and cluster quality measures indicate separation of the two response patterns in the current cohort, and as such these analyses do not represent an independent validation of cluster stability. 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. Wrestlers exposed to comparable training conditions may exhibit different cardiac autonomic responses. These findings support further investigation of longitudinal multivariate HRV profiling for characterizing interindividual cardiac autonomic responses in athletes. Its potential application to individualized athlete monitoring requires further validation against recovery, fatigue, training load, and performance outcomes.