Training for kokoda can become a threat, How Overreaching Can Wire Stress into the Nervous System

23 Feb 2026 11:50 AM

We’re often told that growth lives outside the comfort zone.

Push harder.
Go further.
No pain, no gain.

And sometimes that’s true.

But there’s a line — and when exercise moves too far beyond current capability, it can stop being adaptive stress and start becoming neurological threat.

When that happens, the body remembers.

And not in the way we hope.

The Brain Doesn’t Separate “Challenge” from “Danger”

At the centre of this response sits the amygdala.

The amygdala plays a key role in detecting threat and activating protective responses through the hypothalamic–pituitary–adrenal (HPA) axis. When it perceives danger, it increases sympathetic nervous system activity and cortisol release (LeDoux, 2000; McEwen, 2007).

Importantly, the brain does not neatly categorise stress as “physical” or “psychological.” If physiological strain exceeds perceived coping capacity, the amygdala may tag the experience as threat rather than growth.

That distinction matters.

When training load is interpreted as manageable challenge, we see adaptive responses — improved mitochondrial function, neuromuscular efficiency, and cardiovascular capacity (Hawley et al., 2014).

When it is interpreted as threat, the response shifts toward protection — elevated cortisol, increased inflammatory markers, and reduced recovery capacity (Meeusen et al., 2013).

The Difference Between Overload and Overtraining

Exercise adaptation relies on progressive overload followed by adequate recovery. This model is well established in sport science (Kreher & Schwartz, 2012).

However, when recovery is insufficient, participants may enter:

• Functional overreaching (short-term fatigue, performance rebounds with rest)
• Non-functional overreaching (longer performance decline, mood disturbance)
• Overtraining syndrome (persistent performance impairment, autonomic dysregulation)

Research shows overtraining is associated with altered HPA-axis regulation, increased sympathetic activity, mood disturbance, and impaired sleep (Meeusen et al., 2013).

What’s often missed is that these states are not purely muscular.

They are neurobiological.

Stress Conditioning: When the Body Learns to Brace

The nervous system learns by association.

Repeated pairing of a context with excessive stress can create conditioned responses — a process first described in classical conditioning research (Pavlov, 1927).

In training environments, this may look like:

• Elevated heart rate before warm-up
• Anxiety before high-intensity intervals
• Avoidance of certain training modalities
• Reduced intrinsic motivation

Neuroimaging research shows the amygdala becomes sensitised following repeated stress exposure, increasing future reactivity (Roozendaal et al., 2009).

In simple terms: if sessions repeatedly overwhelm capacity, the brain begins preparing for threat before the load even arrives.

Stress Stacking: The Allostatic Load Effect (a critical understanding for kokoda)

Exercise does not occur in isolation.

The concept of allostatic load — introduced by McEwen & Stellar (1993) — describes the cumulative burden of chronic stress on the body.

When a participant is already carrying:

• Sleep deprivation
• Emotional stress
• Nutritional insufficiency
• Work or academic pressure

Their baseline physiological stress markers are elevated.

Layering excessive training or challenge on top can push the system toward chronic sympathetic dominance, reduced heart rate variability, and impaired recovery (Plews et al., 2013).

The issue is not intensity alone.

It is total load relative to teh ability to adapt.

When Challenge such as kokoda Builds Resilience — and When It Doesn’t

Stress exposure can build resilience when:

• The stressor is time-limited
• The individual has sufficient recovery
• The challenge is within a stretch zone
• Mastery is experienced

This aligns with stress inoculation theory (Meichenbaum, 2007) and hormesis research in physiology (Radak et al., 2008).

But when stress becomes overwhelming and uncontrollable, it increases risk for dysregulation rather than adaptation.

Resilience grows at the edge of capacity.

Not miles beyond it. this is critical for the kokoda Trek Leader to understand, so adjustments if needed can be made.

Recalibrating the Nervous System

If stress conditioning on Kokoda has occurred, the research suggests the solution is not complete avoidance — but graded exposure paired with recovery (Sapolsky, 2004).

Practical applications:

1. Temporarily reduce intensity and volume.
2. Rebuild “successful completion” sessions.
3. Prioritise sleep and nutritional restoration.
4. Use paced breathing to downregulate sympathetic activation.
5. Progress load gradually.

Repeated experiences of “hard but manageable” help recalibrate amygdala reactivity over time.

The nervous system is plastic.

It learns safety the same way it learned threat.

Final Thought

True performance is not built by overwhelming the system.

It is built by applying stress that the organism can adapt to. Kokoda trek leaders need to understand this by creating a flexible schedule if required. 

When training respects capacity, the brain encodes confidence.

When it repeatedly exceeds it, the brain encodes defence.

The art is not pushing harder.

It is pushing wisely.

References

Hawley, J. A., et al. (2014). Integrative biology of exercise. Cell, 159(4), 738–749.

Kreher, J. B., & Schwartz, J. B. (2012). Overtraining syndrome: A practical guide. Sports Health, 4(2), 128–138.

LeDoux, J. (2000). Emotion circuits in the brain. Annual Review of Neuroscience, 23, 155–184.

McEwen, B. S. (2007). Physiology and neurobiology of stress and adaptation. Physiological Reviews, 87(3), 873–904.

McEwen, B. S., & Stellar, E. (1993). Stress and the individual: Mechanisms leading to disease. Archives of Internal Medicine, 153(18), 2093–2101.

Meeusen, R., et al. (2013). Prevention, diagnosis and treatment of the overtraining syndrome. European Journal of Sport Science, 13(1), 1–24.

Meichenbaum, D. (2007). Stress inoculation training. In Principles and Practice of Stress Management.

Pavlov, I. (1927). Conditioned Reflexes.

Plews, D. J., et al. (2013). Training adaptation and heart rate variability in elite endurance athletes. European Journal of Applied Physiology, 113(2), 365–373.

Radak, Z., et al. (2008). Exercise, oxidative stress and hormesis. Ageing Research Reviews, 7(1), 34–42.

Roozendaal, B., et al. (2009). Stress, memory and the amygdala. Nature Reviews Neuroscience, 10, 423–433.