Cortisol on Kokoda

3 Feb 2026 2:50 PM

One of the defining features of people stepping onto Kokoda isn’t weakness or lack of fitness it’s anticipatory load. Most arrive carrying stress or anxiety about what they’re about to face. Biologically, that shows up as elevated cortisol.

But cortisol isn’t “stress” in the way people think about it.
Cortisol is the hormone of uncertainty.

It spikes when the nervous system doesn’t know:

• what’s coming next
• how long this will last
• when it will end
• whether it has the resources to cope

Remove uncertainty, and cortisol drops, even if the task itself is still hard. That’s why simply talking with participants before Kokoda matters so much. We’re not calming them down with reassurance; we’re closing the unknowns. And biology responds immediately.

This is also why burnout feels endless. There’s no end signal. The brain never receives the message: “Threat resolved.” Cortisol stays elevated because, from a survival perspective, the job is unfinished.

The military understands this deeply. In genuine life-or-death contexts, there are disciplined post-event procedures, debriefs, routines, recovery protocols, not for psychology, but for biology. These processes close the loop and tell the nervous system the danger has passed.

Unfinished tasks keep cortisol high. The brain codes them as “threat unresolved.”
One of the simplest ways to shut this down is closure. Before rest, write down three things you completed today. Completion is a biological signal. It reduces cortisol faster than comfort, distraction, or positive thinking.

Physical techniques matter too, especially ones that don’t require cognition.
Isometric holds work exceptionally well:

• wall sits
• planks
• gripping a towel or bar hard for 20–30 seconds

Strong muscle tension sends a primal message upstream: “I handled the threat.”
The nervous system relaxes automatically. No reframing required.

Warmth also matters, more than people realise.
Warmth tells the nervous system: “Survival achieved.”
Cold does the opposite. Cold exposure reliably increases cortisol; warmth lowers it. Human biology evolved around fire, shelter, and heat, not ice baths. Cold can be a stressor you choose, but it is still a stressor.

Cortisol also hates randomness.
Predictability equals safety.

Consistent wake times, mealtimes, and sleep windows matter more than people want to admit. Even on Kokoda, simply holding the same bedtime measurably lowers cortisol. The body doesn’t crave freedom, it craves rhythm.

Where many people go wrong is trying to process emotions first. That’s backwards.

You stabilise the body before you stabilise the mind:

• Movement
• Breathing
• Food
• Sleep

Then words.

Trying to talk while cortisol is high doesn’t release stress, it locks the loop deeper. The biology has to settle first. Only then does reflection actually integrate rather than reinforce threat.

That’s not mindset work.
That’s how the nervous system works.

References

• Sapolsky, R. M. (2004). Why Zebras Don’t Get Ulcers. Holt Paperbacks.
  → Foundational text on cortisol, uncertainty, and chronic stress biology.
• McEwen, B. S. (1998). Protective and damaging effects of stress mediators. New England Journal of Medicine, 338(3), 171–179.
  → Introduced allostatic load and how unresolved stress keeps cortisol elevated.
• Herman, J. P., et al. (2003). Neural regulation of the stress response. Endocrine Reviews, 24(4), 513–536.
  → Explains how predictability and perceived control modulate cortisol output.
• Brosschot, J. F., Gerin, W., & Thayer, J. F. (2006). The perseverative cognition hypothesis. Psychosomatic Medicine, 68(1), 113–124.
  → Shows how unfinished tasks and rumination prolong physiological stress responses.
• Porges, S. W. (2011). The Polyvagal Theory. Norton.
  → Explains why muscle tension, warmth, and safety cues down-regulate threat physiology.
• Kivimäki, M., et al. (2019). Long working hours and stress response. The Lancet Psychiatry, 6(7), 553–565.
  → Links predictability, routine, and recovery signals to cortisol regulation.
• Tipton, M. J., et al. (2017). Cold exposure and stress responses. European Journal of Applied Physiology, 117(1), 1–10.
  → Demonstrates cortisol elevation with cold exposure.