Physiology at Firstbeat
Why is Heart Rate Variability Important?
Studying the heart provides us with a vast amount of information about our body. From beat to beat, heart rate is constantly changing to meet the needs of life. Heart rate variability (HRV) means the variation in time between consecutive heartbeats. It is universally accepted as a non-invasive marker of autonomic nervous system (ANS) activity. A variety of physiological phenomena affect HRV, including:
- Inhalation and exhalation, control of breathing
- Autonomic Nervous System (ANS) adjustments
- Hormonal reactions
- Metabolic processes and energy expenditure
- Physical activity, exercise and recovery from physical activity
- Movements and changes in posture
- Cognitive processes and mental load
- Stress reactions, relaxation, and emotional reactions
Making sense of HRV
Heart rate variability increases during relaxing and recovering activities and decreases during stress. Accordingly, HRV is typically higher when the heart is beating slowly and decreases as the heart beats more quickly. In other words, heart rate and HRV have a generally inverse relationship.
HRV changes from day to day based on activity levels and amount of work-related stress. In addition to these external stress factors, internal stress factors cause variation daily HRV levels. Internal stress factors include poor nutrition, alcohol use, illness, etc.
Higher fitness levels usually results in increased HRV compared to people with lower fitness levels. High HRV is commonly viewed as an indicator of a healthy heart.
HRV can be measured with for example time and frequency domain methods for evaluating sympathovagal balance (i.e., the balance between sympathetic and parasympathetic activity).