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 generally 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 can provide insights into overall well-being and help individuals manage their health more effectively. It is often measured using specialized devices or apps that track heart rate patterns.