By Drew Maffett
Current Master’s Degree Student, Sports and Health Sciences
If you’ve ever wondered why one person finishes a workout feeling calm and accomplished while another walks away feeling anxious, exhausted, or completely overwhelmed, the answer may be less related to fitness and more related to how efficiently their nervous system is functioning. Exercise isn’t just a challenge for your muscles; it’s also a stressor that your brain has to interpret and overcome.
For a well-regulated nervous system, stress is usually viewed as safe. When the body’s heart rate rises, the respiratory rate increases, there are adrenaline spikes and the muscles begin working harder. The brain recognizes these changes as a normal response to exercise.
Once the workout is over, the body settles back into recovery. Over time, this process builds resilience and the nervous system. The nervous system learns how to transfer back and forth from “fight or flight” mode to “rest and digest” mode.
When the nervous system becomes dysregulated from chronic stress, anxiety, trauma or panic disorder, those same physiological changes feel like danger instead of exercise. Heart rate, respiratory rate, and adrenaline levels may increase and decrease in less coordinated ways. Consequently, that makes exercise feel uncomfortable, overwhelming and much more difficult than it would for someone with a well-regulated nervous system.
What Is Nervous System Dysregulation?
Your autonomic nervous system (ANS) is the part of your nervous system responsible for regulating the body’s automatic functions and processes that occur without conscious thought. Each heartbeat, breath, blood pressure adjustment, digestive movement, and change in body temperature is continuously regulated by the autonomic nervous system to maintain homeostasis and help you respond to your environment.
The autonomic nervous system is made up of two primary branches: the sympathetic nervous system (SNS) and the parasympathetic nervous system (PNS). Although these systems are often presented as opposites, they are both essential components of the autonomic nervous system and work together to keep the body functioning efficiently.
Most people know the sympathetic nervous system as the “fight-or-flight” response because it prepares the body for action. During exercise, this system increases heart rate, respiratory rate, blood pressure and blood flow to working muscles so your body can meet the increased physical demand of exercise.
The parasympathetic nervous system is often called the “rest-and-digest” system. This system slows the heart rate, supports digestion, restores energy and promotes recovery once the physical challenge of exercise has passed.
Neither of these two nervous systems are good or bad; you need both in order to function and survive. Exercise is actually intended to activate the sympathetic nervous system, so the goal isn’t to avoid sympathetic activation, but to transition back toward parasympathetic recovery once the workout is over.
A healthy nervous system moves between these states relatively seamlessly. Dysregulation doesn’t simply mean the sympathetic nervous system is activated; it means the autonomic nervous system has difficulty adapting to changing demands.
As a result, the body may become “stuck” in a heightened state of stress or have difficulty returning to a state of safety and recovery after the stressor has ended.
The Polyvagal Theory and Nervous System Regulation
Polyvagal theory expands on the traditional understanding of the autonomic nervous system by explaining how the sympathetic and parasympathetic nervous systems are regulated, based on our perception of safety or threat. Rather than functioning like an on-and-off switch, the autonomic nervous system continuously evaluates cues from both the internal and external environment, which is called neuroception.
When the brain perceives safety, the ventral vagal branch of the parasympathetic nervous system supports social engagement, emotional regulation, efficient movement and recovery. As perceived threat increases, sympathetic activation mobilizes the body for action through the fight-or-flight response.
If the nervous system determines that the threat cannot be escaped or overcome, the dorsal vagal branch of the parasympathetic nervous system may trigger a shut-down response characterized by:
- Emotional numbness
- Dissociation
- Fatigue
- Withdrawal
This model helps explain why people with PTSD or chronic stress often don’t simply experience “too much” sympathetic activation. Instead, they may fluctuate between hyperarousal and hypoarousal, making exercise feel energizing one day, intolerable the next, and completely exhausting after that.
Understanding these autonomic responses allows exercise professionals to recognize that exercise tolerance isn’t determined solely by cardiovascular fitness or muscular strength. The ability to exercise is also influenced by how the nervous system interprets and regulates physiological stress.
How Breathing Affects Nervous System Regulation
One of the fastest ways the nervous system responds to stress is through breathing.
With every breath, there is an exchange of oxygen for carbon dioxide (CO₂) in the lungs. Oxygen is carried by hemoglobin to working muscles and organs, while carbon dioxide is transported back to the lungs to be exhaled.
Although carbon dioxide often gets a bad reputation, your body depends on it. Carbon dioxide helps regulate blood pH, influences when you feel the urge to breathe and even affects how efficiently oxygen is delivered to your tissues.
During periods of stress or panic, breathing often becomes faster than the body’s metabolic demands. In this event, carbon dioxide is being breathed off faster than it should be (hyperventilation).
Hyperventilation can lead to respiratory alkalosis, causing dizziness, tingling and chest tightness. It also creates the sensation that you can’t catch your breath, even when oxygen levels remain normal.
It’s also important to note that the presence of hyperventilation can be expected during aerobic exercise. With people suffering from nervous system dysregulation, hyperventilation can occur prematurely, causing a panic attack or an increased perception of perceived threat. These symptoms can be frightening because they closely resemble a medical emergency.
Imagine beginning a run as someone with a dysregulated nervous system. Your breathing naturally becomes heavier and shallow, and you start blowing off high levels of carbon dioxide, reaching for increased oxygen levels.
For most people, these are the expected signs of exercise. For someone whose nervous system already associates those sensations with panic, those same physiological responses may be interpreted as danger.
Why Exercise Feels Harder for Some People
Exercise is one of the most effective non-pharmacological tools for improving mental health, reducing stress and building resilience. However, people living with Post-Traumatic Stress Disorder (PTSD) and panic disorder are consistently more likely to avoid exercise than the general population.
The problem is not that they’re less motivated; it’s because exercise is more difficult for them. These barriers to exercise are rooted in physiology, psychology and neurobiology.
According to a group of Russian and American researchers writing for the International Journal of Molecular Sciences (IJMS), regular physical activity has also been shown to increase brain-derived neurotrophic factor (BDNF). BDNF is a protein that supports neuroplasticity, learning, memory, and the growth and survival of neurons.
In people living with PTSD, chronic stress can impair neuroplasticity and contribute to structural and functional changes in brain regions. Increased BDNF from exercise may help support recovery of these brain regions over time.
Research suggests that nervous system dysregulation is related to reduced heart rate variability, heightened sensitivity to changes in carbon dioxide, and alterations in brain networks responsible for processing emotion and threat. The amygdala often becomes hyper-responsive to perceived threats, and the regions of the prefrontal cortex responsible for inhibiting fear responses may become less effective.
At the same time, chronic activation of the hypothalamic-pituitary-adrenal axis can disrupt cortisol regulation, making it more difficult for the body to recover after periods of stress. The IJMS article researchers also noted that some studies also suggest differences in dopamine signaling in these populations, meaning the rewarding feelings many people experience after exercise may be less pronounced.
In other words, exercise may initially feel much harder for someone with nervous system dysregulation (both physically and emotionally), even though it remains one of the most beneficial interventions over time.
Teaching the Nervous System That Movement Is Safe
The good news is that the nervous system is remarkably adaptable. Through neuroplasticity, the brain continuously strengthens and reorganizes neural pathways based on repeated experiences. Exercise is one of the most powerful stimuli for this process, partly because it increases BDNF, helping the brain build and reinforce healthier patterns of responding to stress.
For individuals with PTSD or chronic stress, the goal isn’t to push through overwhelming discomfort. It’s to gradually teach the brain that an elevated heart rate, heavier breathing and physical exertion are safe.
Every workout becomes reassociated as an opportunity to replace fear-based stimuli with experiences of safety, competence and recovery. Working with a trauma-informed coach, physical therapist or exercise physiologist can make this process more effective.
Trauma-informed exercise emphasizes gradual progression and psychological safety. It allows the body to meet the nervous system where it is, rather than forcing it beyond its capacity.
Sports psychology also shows that long-term habits are more sustainable when they become part of your identity. Rather than saying, “I tried to run,” begin to think, “I am a runner.” Instead of saying, “I’m trying to work out,” think, “I’m an active person who prioritizes my health.”
Identity creates intrinsic motivation, causing the behavior becomes an expression of who you are instead of something you must convince yourself to do, an approach that is scientifically proven to increase exercise adherence.
I like to think of it this way: be the thermostat, not the thermometer. A thermometer simply reflects its environment, while a thermostat sets it.
Your nervous system is dynamic and may have difficult days, but your commitment to exercising doesn’t have to change with it. When your actions align with who you believe you are, consistency becomes easier, even when your motivation fluctuates.
Exercise Trains Both the Body and the Nervous System
Exercise gains aren’t only muscular; you are also training your nervous system. The way the body responds to movement is influenced by far more than cardiovascular fitness or strength.
Your brain is constantly deciding whether the physical sensations of exercise represent growth or danger, and that interpretation shapes everything from your breathing and heart rate to your motivation and recovery. For people living with chronic stress, trauma, PTSD or panic disorder, those responses aren’t a sign of weakness, but a reflection of how the nervous system has adapted to past experiences.
The encouraging part is that the nervous system is capable of great change. With consistent movement, gradual exposure, and an approach that prioritizes both physical and psychological safety, the brain can learn that an elevated heart rate, heavier breathing, and physical exertion are not threats. Instead, they are evidence that you’re becoming stronger. Progress isn’t measured by never feeling challenged; it’s measured by repeatedly showing your nervous system that it’s safe to recover.
Every bout of exercise is a new opportunity to build resilience, strengthen the connection between mind and body, and remind yourself that your past doesn’t have to dictate how your body responds in the future. Exercise won’t solve every challenge, but over time it can help reshape the way your nervous system experiences the world.
About the Author
Drew Maffett is a certified exercise physiologist (ACSM-EP) based in New York City and a current graduate student at American Military University, part of American Public University System. She is currently pursuing a master’s degree in sports and health sciences with a concentration in human performance.
Drew holds a B.S. in exercise physiology from Ohio University and is a U.S. Army combat medic veteran. Her work focuses on making complex exercise physiology accessible and practical, with a particular interest in the physiology of stress, nervous system regulation, and the relationship between trauma and exercise.
Her passion for this work extends into her practice, where she provides trauma-informed exercise physiology sessionsthat help people better understand their physiological responses to exercise and build confidence in what their bodies can do. Drew is passionate about reducing barriers to science and translating complex concepts into information people can actually understand and apply.
Learn more about her work, educational resources, and individualized sessions at www.drewxphys.com.
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