In the sports science domain, heart rate variability (HRV) is termed a potentially valuable tool for monitoring the activity of the autonomic nervous system (ANS) and optimizing the performance of athletes. This chapter offers a thorough discussion of HRV assessment strategies for optimal performance intervention. By interpreting the HRV data, athletes and coaches can modify training loads, enhance recovery, and improve overall performance. Based on recent research, we describe practical guidelines for implementing HRV-based training programs into practice. It includes both the physiological and methodological aspects related to HRV monitoring.