We know from numerous studies that heart rate variability (HRV) can be an important indicator of physical and mental health. It is also an objective measure of physical fitness, including during sports.

This is influenced by factors such as diet, sleep, stress levels, and psychological factors. HRV can also provide information about the status of the immune system and susceptibility to disease.

HRV is also referred to as a measure of neurovegetative activity and reflects the autonomous function of the heart. It shows the temporal change from heartbeat to heartbeat (the so-called RR interval). This can be determined very well using a 24-hour ECG measurement.

Neurovegetative activity is influenced by the autonomic nervous system and thus by two antagonists that should maintain balance: the parasympathetic nervous system (deactivating) and the sympathetic nervous system (activating).

When the autonomic nervous system is in balance, both calming and stimulating signals are sent to the heart by the opposing forces. This results in fluctuations in heart rate, known as heart rate variability (HRV).

If HRV is high, this indicates a balanced response to the parasympathetic and sympathetic nervous systems and thus an adequate adaptation to stress factors (e.g., exercise, stress).

Low HRV is counterproductive to the body's health in the long term and is a sign of a lack of recovery phases. This can be caused by factors such as overexertion during sports or at work. An imbalance in electrolytes, fluids, and nutrition can also be a contributing factor.

The goal should then be to improve HRV again. The following measures are particularly recommended for this purpose:

• A circadian rhythm with sufficient sleep
• Optimization of nutrition and fluid balance
• Avoidance or reduction of risk factors (stress, alcohol, lack of exercise)
• Heart rate-controlled endurance training

For proper endurance and strength endurance training, it is recommended to undergo a sports medical examination with lactate measurement in order to determine the aerobic heart rate range that contributes to optimizing HRV.

One measurement for HRV is the SDNN value (standard deviation of RR intervals). It provides information about the overall variability of heartbeats. In cardiology, it is an important parameter for monitoring progress after cardiovascular events such as myocarditis or a heart attack.

Various tables with SDNN standard values are provided in the literature (e.g., “Herzratenvariabilität” [Heart Rate Variability] by Dr. Doris Eller-Berndl). Here, too, the basis for the calculation is a long-term ECG over at least 24 hours with approximately uniform activity.

Sources:

• Task Force of The European Society of Cardiology and The North American Society of Pacing and Electrophysiology(ESC/NASPE)
• 1996;94:2850–2855
• Source: Herzratenvariabilität, Doris Eller-Berndl, Seite 30
• Image: Pexels.com