The autonomic nervous system

As athletes, we constantly move between phases of intense exertion, peak performance, excitement, and focused concentration, as well as times of recovery, relaxation, and regeneration. This ability to achieve physical and mental peak performance, then recover and gain training effects, is enabled by our autonomic nervous system (ANS). The ANS controls vital functions such as heartbeat, breathing, digestion, and metabolism—all critical elements for athletic performance. Emotional aspects such as well-being, balance, or stress also originate there. It is an essential player and mediator in the interaction between body and mind, between consciousness and subconscious.

The “autonomy” of this system means that it automatically regulates and adjusts biological processes in the body without our conscious control. However, we can influence it indirectly, as we will see. Functionally and anatomically, the ANS is divided into two main parts: the sympathetic and parasympathetic systems. These work mainly antagonistically. The sympathetic system primarily sends performance-enhancing signals, while the parasympathetic system transmits recovery-promoting signals via the vagus nerve.

For optimal athletic performance, we need a strong and flexible nervous system. This allows us to remain capable and focused while regenerating in a balanced way. Flexibility means that the nervous system adapts to current demands and recovers afterward. This also applies to changing demands within a training session or competition. Sustained peak performance is impossible without this flexibility.

Sympathetic and parasympathetic systems do not work like an on/off switch but like sliders adjusted according to the situation. Under resting conditions, sympathetic activity is minimal or absent in healthy individuals. However, during various disease states and physical and mental stress, it is high. After training, a quick return to higher parasympathetic activity levels is desirable as this correlates with performance readiness, higher training status, and better self-regulation. Particularly in well-trained athletes, ANS recovery occurs faster regardless of training intensity.

To find the balance, we need not only reduce sympathetic activity but also actively reactivate and strengthen the parasympathetic part. Cardiac parasympathetic activity is suggested as a global marker for athlete recovery and can be indirectly measured by heart rate variability (HRV).

In recent years, HRV has established itself as a qualitative index of “sympathovagal balance.” The HRV phenomenon describes fluctuations in the intervals between successive heartbeats and heart rates, reflecting our heart’s ability to respond appropriately and flexibly to various demands. The more variable the heartbeat, the better the heart can respond to challenges and calm down afterward, providing insights into vagal regulation.

The foundation lies in the nervous intertwining of our heart, as heart rate and rhythm are largely controlled by the autonomic nervous system. The parasympathetic influence on heart rate is mediated by acetylcholine release through the vagus nerve. The sympathetic influence on heart rate occurs through the release of adrenaline and noradrenaline. However, vagal activity can affect the heart much faster than sympathetic activity, likely due to faster signal transduction and acetylcholine receptor kinetics, allowing it to delay the immediate heartbeat. High-frequency HRV fluctuations are mainly mediated parasympathetically, while low-frequency HRV fluctuations are mediated both sympathetically and parasympathetically.

Various studies in recent years demonstrate the relevance of HRV as a marker positively correlated with health, well-being, self-regulation, and athletic performance. No wonder HRV is now routinely implemented in tracking tools and fitness watches.

The positive effects of breathing on physiological and mental processes have been known for centuries. Only in recent years have we gained a better understanding of the underlying mechanisms, allowing us to use breathing techniques systematically to influence performance, recovery, and well-being.

The brainstem and core regions of the hypothalamus contain the main control loops for all components of the sympathetic and parasympathetic systems, serving as essential control centers for autonomic nervous system functions. This means that both parts of the autonomic nervous system are under the control of central breathing centers. Inhalation is stimulated by the sympathetic system, exhalation by the vagus. This is reflected in respiratory sinus arrhythmia: our heart beats slightly faster during inhalation and slower during exhalation.

Based on the close connection between breathing, consciousness, and autonomic arousal, two essential arguments support focusing on breathing:

• Automatic and Control: Breathing occurs automatically and to some extent unconsciously. However, specific parameters, such as breathing faster, slower, shallower, or deeper, can be consciously controlled. Breathing thus lies at the interface between our conscious and unconscious behavior. The cortex influences breathing through direct neural pathways to the brainstem, where these signals are integrated with autonomic controls of the hypothalamus. This allows both automatic regulation of breathing and conscious control through higher brain functions.
• Feedback: The ANS not only determines the vital function of breathing but breathing also directly affects the nervous system. It can both activate and calm the nervous system, controlling essential physical (e.g., breathing rate, heart rate, blood pressure) and mental processes (e.g., brain perfusion, nerve sensitivity, neurotransmitter release). During conscious inhalation, we influence the sympathetic system more, while during conscious exhalation, we influence the parasympathetic system more.

To become more aware of this connection, the following exercise can help: place one hand on the chest and the other on the belly while breathing, and breathe a few times into the chest, then into the belly. You will likely find that belly breathing feels more relaxed and calming. This is because the sympathetic nerves originate in the chest area, and the parasympathetic nerves in the lower abdominal area. In stressful situations (sympathetic), we breathe more through the chest, while in more relaxed moments (parasympathetic), we automatically breathe through the belly.

Breathing techniques, particularly slow-paced breathing (SPB), are gaining popularity among athletes due to their potential to improve physical and mental performance. SPB means slowing down spontaneous breathing, which at rest comprises about 12-20 breaths per minute. There is strong scientific evidence that SPB leads to a parasympathetic balance and an increase in vagus activity in healthy individuals. Practicing slow breathing can improve optimal sympathovagal balance, with the ideal HRV typically observed at a breathing rate of about 6 breaths per minute (0.1 Hz).

Breathing at this so-called resonance frequency has been shown to increase autonomic adaptability and resilience to physical and mental stress, improving relaxation during and after training or competition. It allows for optimizing physiological parameters related to health and athletic performance, such as cardiovascular functions (e.g., blood pressure), respiratory functions (e.g., pH optimization), and cardiopulmonary functions (e.g., synchronization of blood flow and heart rhythm).

Breathing is our strongest ally in mental training, as the Greek origin of the word “spirit” (pneuma), meaning “breath,” shows. Breathing lies at the interface between our conscious and unconscious behavior. Through breathing, the brain controls its own excitability and mental state, either consciously or unconsciously. It is known that breathing has the potential to regulate psychological effects such as mood, emotions, mental resilience, relaxation, pain, awareness, and focus.

No wonder breathing is referred to as the central gateway to our consciousness. Through conscious breathwork, we can influence our inner experience. We use breathing as a direct access to our consciousness and focus on breathing as a means to focus the mind. Through concentrated and conscious breathing, we can control the mind, calm it, focus it, and bring it into a state of concentration and alertness. As breathing becomes more balanced, so do we. As breathing becomes more focused, so do we.

Studies show that just a few minutes of slow breathing are enough to achieve positive effects. For athletes, the question arises of how effective these techniques are before, during, and after training sessions or competitions. Research results confirm the effectiveness of conscious slow breathing: an improved HRV can be observed during the breathing exercise, immediately after, and long-term after several sessions. More pronounced effects are observed in longer-term interventions, indicating a strong dose-response relationship.

For athletes, it is therefore advantageous to integrate conscious slow breathing into their training routine. Here’s an approach to experience its effectiveness:

• Practice Slow Breathing: Reducing the breathing rate may feel unfamiliar at first. Get used to slow breathing by gradually increasing the duration of a complete breath from 5 to 10 seconds. If this is not yet possible, stay at your achieved frequency. The important thing is to breathe slower than usual. The length of inhalation should match that of exhalation; it is generally okay to exhale slightly longer than inhale.
• Conscious Slow Breathing in Everyday Life: Breathe consciously slowly about 6 times per minute (or your individual frequency) throughout the day for a total of 20 breaths (about 3 minutes). Whether sitting, lying down, or during light activity, focus on your breath. A quiet environment helps initially; later, you can integrate it into everyday situations.
• Connect Breathing with Training: Take a few minutes (about 20 breaths) before and after training for conscious slow breathing. Use it to tune into your training and wind down afterward.
• Slow Breathing During Training: Experiment with slow breathing during your training. Use short breaks or low-intensity phases. Even if you don’t reach the 6 breaths per minute due to exertion, try to breathe as slowly as possible without feeling uncomfortable breath hunger.

If you wear a heart rate monitor, you can directly observe the effect on your heart rate. This combines slow breathing with biofeedback, ensuring the correct breathing pattern is maintained.