Heart Rate Variability (HRV) refers to the variation in time intervals between heartbeats. It is a measure of the autonomic nervous system's regulation of the heart, reflecting how well the body can adapt to stress and environmental changes. Higher HRV is often associated with better cardiovascular health and resilience, while lower HRV may indicate stress or potential health issues. HRV can be influenced by various factors, including exercise, sleep quality, and stress levels. Monitoring HRV is becoming popular in health and fitness communities, as it can provide insights into overall well-being and help individuals optimize their training and recovery strategies.