Sympathetic and Parasympathetic Nervous System

Reclaim your vitality

What You’ll Learn About the Sympathetic and Parasympathetic Nervous System

  • How these two systems work together to balance performance and recovery.

  • Why nervous system flexibility is the foundation of resilience, focus, and sustained energy.

  • What influences your nervous system and practical ways to optimise it for health and high performance.

This post is part of a larger piece about nervous system training for stress and performance.

Click here for: The Complete Guide to Nervous System Training for Stress and Performance

Understanding the Sympathetic and Parasympathetic Nervous System

Keeping with the demands of modern-day life requires emotional regulation, mental acuity, and physical resilience, all of which depend on one key system: your nervous system.

Specifically, the sympathetic and parasympathetic branches of the autonomic nervous system (ANS) determine how your body responds to stress, recovers from exertion, and maintains performance under pressure. While most people associate the nervous system with stress or anxiety, it is involved in nearly every aspect of your health, from sleep, breathing and digestion to learning, memory, and even emotional intelligence.

Why Nervous System Flexibility Matters for Resilience and Performance

The ability to flexibly move between sympathetic (activating) and parasympathetic (restorative) states is essential for maintaining energy, focus, and resilience. Modern day lifestyles often demand prolonged states of sympathetic arousal, keeping us alert, mobilised, and focused on problem-solving, but without the counterbalance of parasympathetic activity, recovery, emotional balance, and cognitive performance can suffer.

Key processes influenced by the nervous system include:

  • Brain growth and development
  • Sensations (such as touch or hearing)
  • Perception (interpreting sensory information)
  • Thought and emotions
  • Learning and memory
  • Movement, balance, and coordination
  • Sleep
  • Recovery and rehabilitation
  • Stress and the body’s responses to stress
  • Ageing
  • Breathing and heartbeat
  • Body temperature
  • Hunger, thirst, and digestion
  • reproductive health, and fertility
sympathetic nad parasympathetic nervous system image

Each branch of the nervous system performs counterbalancing activities within the same organs, with sympathetic arousal preparing us for activity and parasympathetic activity bringing us back to balance after that action.

When these systems lose flexibility, you may experience overactivation, leading to anxiety, tension, racing thoughts and sleep difficulties or underactivation, expressed as mental fog, low motivation, or physical fatigue.

How the Sympathetic and Parasympathetic Nervous Systems Work

The ANS operates automatically, managing processes that don’t require conscious thought, such as heart rate, digestion, and emotional expression. It has two complementary branches:

  • Sympathetic Nervous System (SNS): Mobilises energy and prepares the body for action, triggering the fight-or-flight response. It is essential for focus, performance under pressure, and responding to challenges.

  • Parasympathetic Nervous System (PNS): Promotes rest, recovery, digestion, and repair. It helps bring the body back to baseline after stress and supports long-term resilience.

Optimal performance requires a dynamic interplay between these systems. Like a well-tuned engine, your body should naturally alternate between states of activation and rest, shifting gears and responding to challenges without remaining stuck in one extreme.

What Influences Activation of the Nervous System Branches?

Nervous system flexibility is shaped by a combination of genetic, environmental, and lifestyle factors, including:

  • Stress exposure and life pressures

  • Relationship conflicts

  • Physical workload and exercise demands

  • Quality of nutrition, digestion, and hydration

  • Breathing efficiency and cardiovascular health

  • Sleep patterns and circadian rhythm

  • Social connections and belonging

  • Tolerance for uncertainty

  • Past emotional experiences

  • Genetics

The vagus nerve, the main component of the parasympathetic nervous system, plays a pivotal role in restoring balance. Optimising vagus nerve function, through breathing patterns, optimising brain function, aerobic capacity and oxygenation, as well as lifestyle strategies, enhances your body’s ability to recover from stress and maintain high-level performance.

Integrating Nervous System Awareness Into Resilience and Performance

Understanding the sympathetic and parasympathetic nervous system is more than just scientific insight, it is a strategic tool for managing stress and remaining resilient. By recognising the signals of overactivation or underactivation, and applying evidence-based strategies to restore balance, you can:

  • Recover faster from stress or exertion

  • Maintain clarity, focus, and decision-making under pressure

  • Improve emotional regulation and resilience

  • Support long-term physical and cognitive health

Mastering the interplay between these systems is one of the three core pillars of the BodyMindBrain approach, helping high-performing individuals not just cope with stress, but thrive under it.

For a deeper dive into the parasympathetic nervous system and the critical role of the vagus nerve, explore our dedicated page on Vagus Nerve Function and Polyvagal Theory. Understanding and influencing this system is key for high-functioning performance and sustainable recovery.