Training your nervous system and expanding your 'window of tolerance'

Starting to understand daily impacts on your nervous system

Two years ago, I knew nothing about my nervous system and had no idea that it was something I could or should try to influence. I was oblivious to how daily activities impacted my nervous system and unaware that I could deliberately train it to be more resilient to stress.

Today, after spending significant time reading, learning and experimenting with nervous system science, I’ve come to appreciate just how powerful our nervous systems are.

What is the nervous system & why it matters

The nervous system is the body’s command centre, operating like a thermostat that constantly scans for threats and adjusts our internal states. It works by sending signals between our brain and all other parts of our body. While there are many components (many I'm still learning about), two of the most critical parts of our autonomic nervous system are:

· Sympathetic Nervous System (‘Fight or Flight’): Our stress response system. Heart rate up, cortisol flowing, ready for action.

· Parasympathetic Nervous System (‘Rest and Digest’): Our recovery system. Heart rate down, digestion working, feeling calm and clear.

We fluctuate between these systems throughout our day depending on stimulus. What I find fascinating is something called your window of tolerance - the range of stress you can handle while keeping your nervous systems in balance. Think of it as your stress bandwidth.

Small window = constant overwhelm

If your window is narrow, minor or modest stressors push you into fight-or-flight mode. A difficult email, running late, or an unexpected meeting sends your nervous system into overdrive.

Large window = consistent calmness

With a wide window, you can handle significant pressure while maintaining clarity and composure. Things that derail others barely register for you.

So how do you know how wide your window is, and how do you expand it?

1. Get to know where you stand

I don't believe self-awareness alone is the best approach for understanding your nervous system state. While important, you need objective data or a 'baseline' to measure from.

The morning pulse check (basic level)

Every morning upon waking:

1. Find your pulse

2. Count heartbeats for 30 seconds

3. Multiply x 2 and record the number daily

Notice the trend - if your pulse is consistently higher than yesterday, your nervous system may still be processing stress. Lower than yesterday? A good sign that you've recovered and adapted well.

Heart Rate Variability (the gold standard)

I’ve had an Oura Ring for over 3 years and it’s been a game-changer. Heart Rate Variability (HRV) measures the subtle variations between heartbeats - a direct window into our nervous system's state and how we are responding to stress.

A higher HRV* generally indicates better stress resilience and recovery whilst a lower HRV might indicate your system is under strain.

*HRV can vary significantly between individuals, and what constitutes a ‘good’ HRV depends on many factors such as age, fitness level etc.

I use my monthly HRV average as my baseline to give me an indication of how well my nervous system is functioning daily.

Once you have a baseline (e.g., an average HRV of 40 or a morning pulse check), you can start experimenting.

2. Strategic stress exposure

Counterintuitively, to expand our ‘window of tolerance’ we often need to expose ourselves to more stress not less. But it needs to be the right kinds of stress (aka ‘hormetic stress’) - controlled with appropriate recovery.

The right kinds of stress vary depending on the individual, both in form and intensity. For example, chronic stress like financial hardship is likely detrimental to most people's nervous systems. But ice baths, another form of stress, could be incredibly beneficial for one person and highly detrimental for another (intensity matters too).

Some stressors I’ve experimented with include:

• Exercise: Strength training, cardio

• Cold exposure: Ice baths, cold showers

• Heat therapy: Saunas, hot yoga

• Breathwork: Controlled breathing exercises

• Hyperbaric oxygen chambers

How to experiment

1. Establish your baseline: E.g. Track your heart rate or HRV daily for 2-3 weeks

2. Isolate variables: Test one stressor at a time

3. Measure response: How does your HRV or heart rate change the next day?

4. Adjust intensity: Find your sweet spot

For example, I am currently experimenting if I respond well to hot and cold or just one – and at what intensity. Instead of doing contrast therapy (sauna + ice bath) every day, I have been spending weeks testing ice baths only and tracking results. Before that, I tested saunas only, skipping the cold. Each day I do it, I observe the impact it has on my baseline the following day.

Finding a formula

Everyone responds differently. I might thrive on cold exposure but struggle with heat. You might be the opposite. It's also challenging to isolate particular stressors - so many daily events impact your nervous system.

Intensity matters - an ice bath at 0°C hits very differently than 10°C.

I can usually tell if I have pushed it too hard based on recovery. If I feel energised, alive and light afterwards, I've likely responded well to that stress. If I’m feeling fatigued, exhausted and depleted in the days after, I probably pushed it too far.

3. Recovery

Recovery is the most critical part and where most people fail. After any significant stressor - workout, cold exposure, high-pressure presentation - you must actively downregulate your nervous system. Why? Downregulating tells your brain and body it's safe and helps you return to a balanced nervous system.

I can’t tell you how many times I’ve smashed it at the gym, showered and walked straight out to work. I’ve now learnt that downregulation is crucial to my nervous system health, so after doing anything stressful, I do:

• 5 minutes of coherence breathing: 5 seconds in, 5 seconds out

• a meditation or mindfulness practice; or

• intentional transition time between activities

For example, when I facilitate in front of a group all day, I take 10 minutes in the car to meditate and calm the nervous system before driving home. Or if I push it at the gym, I do coherence breathing on the drive home, so I’m settled by the time I arrive.

Think of it as switching from the accelerator to the brake pedal. Without this step, you're asking your nervous system to stay in overdrive, which can lead to burnout.

The long game: building sustained resilience

If we don't expose ourselves to various stressors, our window of tolerance will shrink and we'll be in a constant state of fight-or-flight. Building nervous system resilience is not a quick fix - it's a lifestyle practice that compounds over months and years.

My HRV still fluctuates as I continue learning what works for my unique physiology and I still have some way to go to reach my optimal nervous system health. But by leaning into this work, I’ve felt empowered and in control. Through deliberate practice, I’ve been able to keep calm in stressful situations, handle multiple competing priorities without always feeling overwhelmed, tackle difficult physical challenges and recover quickly from physical and emotional stressors.

Our nervous system constantly adapts based on the inputs we give it. Give it chaos and unpredictability, and it will stay in chronic stress. Give it controlled challenges followed by intentional recovery, and it will build the resilience you need to thrive under all kinds of pressure.

Curiosity is key.