From Stress to Strength: Breathing Techniques for Running Resilience

Running is more than just building muscles, bones, or mileage—it’s a powerful way to support both physical performance and mental health. Beyond improving strength and endurance, running can act as moving meditation, helping reduce stress, ease anxiety, and boost mood. At the same time, the nervous system plays a critical role in how we move, recover, and adapt, and training it through breathing techniques for running—including breathwork and CO₂ tolerance—can expand our capacity to handle stress, improve oxygen efficiency, and shift the body into true recovery mode. By balancing purposeful stress with intentional recovery, you don’t just become a stronger runner—you become a more resilient, adaptable human.

Breathing Techniques for Running Are Really For the Nervous System

When we talk about training, we often think about muscles, bones, joints, or cardiovascular fitness. But the nervous system is the command center that coordinates all of it. It influences how safe your body feels when moving, how you breathe, how you respond to stress, and even how you recover (both from injuries and your regular training).

I shared a little bit about the nervous system’s role in injury recovery specifically in last week’s newsletter. In this example, pain and restriction aren’t always about physical limitations; they’re often rooted in nervous system guarding. The brain remembers the “danger” of a certain movement and can restrict range of motion, even when tissues are healing. Retraining your nervous system through gradual loading and movement helps your brain relearn safety and restore function.

AND we can train the nervous system directly! That’s what this article is all about.

Beyond injury, the nervous system plays a critical role in recovery. To heal and adapt from training, we must shift from the sympathetic “fight or flight” state into the parasympathetic “rest and digest” state. Without that shift, your body might struggle to repair, adapt, and get stronger.

Stress, Running, and the “Threat Bucket”

Running can be an incredible way to close the stress loop and channel energy. But stress is stress—whether it comes from training, work deadlines, lack of sleep, or emotional strain. If your overall stress load becomes too high, even running can feel overwhelming or lead to injury.

I often use the “threat bucket” analogy to explain this (credit goes to Missy Bunch for this one). Imagine a bucket where every stressor—an old ankle injury, increasing mileage, a sick child keeping you up at night, work projects, or conflict with a spouse—fills it up. Eventually, even something minor like bending over to pick up a laundry basket can “overflow the bucket” and trigger pain or setback.

The solution isn’t to remove all stress. Stress is necessary for growth. After all, training itself is a form of intentional stress. Instead, the goal is to build stress resilience: your capacity to empty the bucket or expand it. This means training your nervous system to recover more effectively and adapt to challenges- and breathing techniques for running can also benefit that.

The Physiology of Progress

At its core, training is about carefully applying stress to stimulate adaptation. You stress the system just enough to trigger remodeling, the body’s way of rebuilding stronger and more efficient. With too little stress, no adaptation occurs. With too much stress or inadequate recovery, the body becomes overwhelmed, increasing the risk of burnout and injury.

But here’s the nuance: training doesn’t exist in a vacuum. Life stressors can shrink your “window of tolerance” for training. What once fit comfortably within your capacity might suddenly push you past the threshold into injury or fatigue when layered on top of life’s demands.

This is why I tell my athletes to treat training plans as living documents. They must adapt to the reality of your life, not just exist on paper. The ability to flex, slowing down progression when needed, prioritizing recovery, or layering in stress management techniques, often makes the difference between sustainable progress and frustrating setbacks.

The key is understanding that the desired physiological adaptations from training happen while you rest!

One of the biggest mindset shifts runners need is understanding that rest is not simply a reward for working hard. Rest is the foundation that makes training effective. Without adequate recovery, training stress cannot convert into positive adaptation.

This is where nervous system training comes in and improves the efficacy of your regular training. By intentionally practicing techniques that both expand our tolerance to stress and help bring us into a parasympathetic state for recovery after said stress we can improve performance capacity and optimize recovery.

My favorite starting point? You guessed it! Breathwork. Breathing techniques for running are an absolute favorite of mine.

Breathing Techniques for Running: The Gateway to Nervous System Health

If you’ve followed my work, you know I use breathwork extensively. We mostly talk about it in the context of biomechanics (improving rib cage mobility, core coordination, and running efficiency), but also for its profound impact on the nervous system.

Breathing is mechanical and psycho-physiological. From a psycho-physiological perspective, how you breathe directly influences whether your body leans toward the sympathetic “fight or flight” mode or the parasympathetic “rest and digest” mode of your autonomic nervous system (a component of the peripheral nervous system that regulates involuntary physiologic processes including heart rate, blood pressure, respiration, digestion, and sexual arousal).

• Slow, rhythmic, diaphragmatic breathing with long exhales promotes parasympathetic activation, helping the body calm down and recover.
• Shallow, rapid, mouth-based breathing keeps you locked in a sympathetic state, useful in short bursts (like sprinting or certain training modalities) but detrimental if you stay stuck there chronically.

A Simple Breath Experiment

Try this quick experiment:

1. Find your pulse on your wrist.
2. Take a deep inhale through your nose, filling your lungs.
3. Slowly exhale fully through your mouth.
4. Repeat for a few cycles and notice your heart rate on the inhales compared to the exhales.
   
   

You’ll likely observe that your heart rate quickens slightly on the inhale and slows on the exhale. That slowing on the exhale is your nervous system tapping into parasympathetic recovery mode. Deep diaphragmatic breathing like this also has a profound effect on heart rate variability (HRV). Just look at the little hug each exhale gives to your heart!!

MRI from the Max Plank Institute for Biphysical Chemistry 

Breath also affects gas exchange. While oxygen gets much of the attention, carbon dioxide (CO₂) is equally critical. Without enough CO₂ in your system, your red blood cells can’t efficiently release oxygen to the tissues that need it. Over-breathing or hyperventilation floods the body with oxygen but strips away CO₂, impairing oxygen utilization.

This sets the stage for our next layer of discussion: allow for training CO₂ tolerance as a way to build both performance capacity and stress resilience.

Why CO₂ Tolerance Matters

Carbon dioxide is far more than just “waste gas.” It plays four key roles in performance and recovery:

1. Triggers breathing: CO₂ buildup, not lack of oxygen, is what tells your body to breathe.
2. Opens airways: CO₂ relaxes smooth muscle cells in your airways, improving airflow.
3. Improves circulation: It relaxes blood vessel walls, enhancing blood flow.
4. Unlocks oxygen: CO₂ helps hemoglobin release oxygen from red blood cells to the muscles that need it.

From a performance stand point: We need CO2 around to actually use the oxygen we breathe in.

This system is tightly controlled by CO2 sensors in the brain stem. Periods of stress or over-breathing (either chronic or acute) can make this system hypersensitive to CO2. Meaning your body will initiate increased respiration BEFORE it’s really necessary. 

Here’s the kicker: Sped up respiration, speeds up respiration.

When this feedback loop goes unchecked, we are breathing in more oxygen without actually being able to use it. This is the opposite of what we want when we are talking about improving our performance and metrics like VO2 max.

When this feedback loop goes unchecked, our body interprets this as a stress response - anxiety. In a state of increased stress response, the body will struggle to recover from the work you are putting in with your workouts. It will also likely become hypersensitive to ALL the things. For me, my first signal is noise, every little noise my kids make drives me up the wall.

From a recovery standpoint: When your body is hypersensitive to CO₂ (something that happens after chronic stress or trauma) it can activate fight-or-flight prematurely, keeping you stuck in a stressed state while spending less time in the rest-digest-recover parasympathetic state.

Training your CO₂ tolerance dampens those alarm bells, improves oxygen efficiency, and builds resilience in your autonomic nervous system. There is also a large overlap between these pieces on the biomechanical side. In this blog, I break down the connection between chronic stress and hip pain.

Testing and Improving Your CO₂ Tolerance

This blog post includes some simple ways to test and improve your CO2 tolerance. 

Low CO₂ tolerance often shows up in more ways than a low score on that CO2 tolerance test. Some signs include:

• Frequent headaches
• Shoulder and neck tightness
• Anxiety, worry, or fear
• Low back pain
• Heartburn or GI issues
• Brain fog or lethargy
• Sports performance plateaus
• Excessive cramping in calves, hands, or feet

These issues often stem from inefficient oxygen use and staying stuck in that sympathetic state. Improving your tolerance takes time and consistency. This process may take months or even years. Be patient because it’s worth it! Improvements in CO₂ tolerance are cumulative and long-lasting.

Balancing Stress and Recovery

Training is purposeful stress. Recovery is where adaptation happens. Breathwork and CO₂ tolerance training give us the tools to expand our window of tolerance, use oxygen more efficiently, and recover more fully.

To thrive (in training and in life), we must be able to move fluidly between stress and recovery. As my friend JPB says:

“The goal is to be able to move back and forth between adversity, risk, excitement, and back to calm, balancing between all states of being human.  [This is] Homeostasis.”

By training our nervous system, we don’t just become better runners, we become more adaptable, balanced humans. If you’re ready to dive deeper into these strategies along with purposeful strength training, streamlined running programming so that you can truly become the expert in your own body and training, keep an eye out for my Women’s Running Academy 12-Week Intensive. Enrollment will open mid-September, and we’ll kick off at the end of September.

In the meantime, if you found this blog post helpful, please pass it along to a fellow runner. You can also subscribe to receive future emails here.

PS. If you’ve been around for a while you know a bit about the Compatible with Life 5k. We started it a little over 3 years ago when I was pregnant with our daughter Charlotte. This virtual event helps raise money, awareness, and advocacy for trisomy 13 and 18.

We originally named the race the “Compatible with Life” 5K because many parents, including us, were introduced to their child's diagnosis as “incompatible with life.” We believe, while this diagnosis is in fact life limiting, these babies are compatible with life and worthy of celebration. And now the American Academy of Pediatrics agrees with us!

​This report came out last month with new guidelines around trisomy 13 and 18. They are no longer considered “uniformly lethal” and they are advocating for more equitable and individualized care of children with trisomy 13 and 18. This is a huge milestone!

Advances like this are what make advocacy and awareness and continuing to talk about it so important. We’d love for you to join us for this year's event! Click here to learn more and sign up.

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