I want to tell you about Andrew Martin.

Andrew is a firefighter in Canada, which already puts him several levels above the average physiology dork pontificating about “resilience” from a climate-controlled office with a laptop, an Oura ring, and the emotional intensity of damp toast.

He’s been collecting heart-rate data during actual emergencies.

Not lab-coat pageantry on a moving belt.

This was not a simulation cooked up in a lab with ethics forms, safety rails, and some intern holding a clipboard like it’s a sacred text.

Real fires, smoke, and rooms full of heat, chaos, and the possibility that somebody inside needs to be dragged back into the land of the living before the whole place turns into a furnace with walls.

During one structure fire, his heart rate hit 190 bpm while searching for victims.

One ninety.

That is not “a bit elevated from physical exertion.”

That is the sympathetic nervous system kicking the saloon doors off the hinges and yelling, “Everything is live now, you poor bastard.”

And when that happens, the whole system gets called to fight.

Temperature regulation gets thrown into a street fight under heavy gear inside a building trying to impersonate the inside of the sun.

pH control starts eating punches from anaerobic demand, rising acid load, and the kind of effort that makes your favorite Concept2 interval look like a lazy paddleboat ride for Q-tips at a retirement resort.

Fuel use turns feral.

Glucose, lactate, liver output, emergency reserves — whatever can be burned before the next ugly thing arrives.

Breathing turns nasty too.

Mask on.

Smoke everywhere.

CO2 pressure rising. Gas exchange reduced to a prison shank fight in a broom closet.

That is the point.

Under real stress, the systems do not stand politely in separate lines waiting for their turn like schoolchildren at a brownie sale.

They collide, overlap, and take the beating together.

That’s physiology in the wild.

Andrew looked at that data and did something rare.

He used it.

No beige-font wellness sermon with a side of “nervous system optimization” nonsense with herbal tea chaser and a ring light.

He trained the edge.

In another session, he dropped his heart rate by 60 beats per minute while spending more than five minutes under cold water below 8°C.

Then he went further and organized cold immersion, breathwork, and sauna sessions for 100 firefighters inside the actual station, next to an actual truck, in the same building where those men and women suit up to walk into scenes that would make most civilians need a nap, a therapist, and a large bourbon.

That is not biohacking.

That is not recovery culture.

This is professional preparation by someone smart enough to test the machinery before the machinery gets tested for him.

And that idea applies to you too, whether your daily life involves barbells, clients, sport, or just trying not to become a fragile houseplant with a Door Dash account.

Because most people spend their whole training life in the middle.

Comfortable temperatures.

Predictable meals.

Controlled breathing.

Moderate intensity.

Safe little lanes.

That works fine until the day life gets mean.

The middle builds capacity.

The edge reveals truth.

Lunt and colleagues showed that short cold-water sessions did more than build cold tolerance. They also improved the physiologic response to hypoxia.

Different stressor. Shared adaptation.

That is cross-adaptation.

One hard lesson, learned by the body once, then reused somewhere else when the lights start flickering.

Same story with S.H.I.T. training — Super High Intensity Training, for the spiritually healthy and physiologically curious.

Done correctly, it doesn’t merely raise your tolerance for lactate and misery. It also hits buffering, challenges fuel switching, and forces breathing regulation to matter while the work is still happening instead of afterward when everyone is lying on the floor questioning their life choices.

That spillover exists because the systems share plumbing whether the coach understands it or not.

And that is where most people still screw this up.

They program like temperature, pH, fuels, and breathing each live in their own little apartment with separate leases and no shared walls.

Cute theory.

Reality does not give 2 hoots about it.

Train one regulator hard enough and you often get carryover into the others.

Train all four on purpose and now you’re building something far more useful than isolated traits.

You’re building a machine that keeps functioning when conditions go sideways.

That matters even more as you age.

Human dynamic range (HDR) shrinks with disuse and age.

The rubber band gets shorter. Less snap. More brittleness.

A stress that used to be annoying becomes destabilizing.

Recovery that once cost you a day starts billing you for three like a deranged accountant working for our government.

And the usual answer people come up with is pathetic.

They try to protect the middle.

Stay comfortable.

Avoid extremes.

Train softer.

Shrink gracefully into biological bubble wrap because you nerfed all your physiology.

That strategy feels smart until life slaps you outside your narrowed range and the whole machine starts rattling like a shopping cart full of broken tools.

The better move is deliberate exposure in a controlled fashion.

No need to binge watch 4 David Goggins videos after snorting DMAA pre-workout off the side of the cold plunge tub.

Intelligently stress your system via:

Cold.

Heat.

CO2 pressure.

Lactate.

Fuel switching.

pH disruption.

The exact things that keep your range from collapsing into a sad little puddle of fragility.

Andrew’s firefighters who train that way at 45 years old will not handle the next fire the same way as the ones who don’t.

Neither will your athletes or you.

Different jobs. Same machinery.

That is exactly why I built the Phys Flex Cert.

Inside it, you get the full framework:

-exact protocols that work and have been tested with real hooomans
-progressions that make sense,
-an integration model for all four pilars
-and more than 40 explicit action steps you can actually use.

Zero vague theory or GooRoo smoke and mirrors .

No brittle "optimal" practices that collapse the second real stress arrives with a crowbar and bad intentions.

Just physiology with dirt under its fingernails ready to be unleashed.

Cart closes Monday, April 27 at midnight PST.

​https://miket.me/physflex <-- full details

Payment plans are live at checkout via Affirm and Klarna.

Much love and cross-adaptation,
Dr. Mike

PS — The Red Light Therapy Masterclass — 6 videos I built for Dr. Andy Galpin and Dan Garner at Biomolecular Athlete that were never released publicly — plus the Meathead Cardio Quick Start Guide both disappear when the cart closes Monday night. Enroll before then and they’re yours at no extra cost.

PPS — “The Phys Flex Cert has given many usable tools that are easily implemented.

The concepts are presented very clearly without the jargon. I would recommend it to my long suffering co-workers and friends that are dealing with life and work stress and all the concomitant damage that comes along with that.”
— Andy O’Brien, shift worker

​https://miket.me/physflex <-- closing soon

References

Lunt, H. C., Barwood, M. J., Corbett, J., & Tipton, M. J. (2010). 'Cross-adaptation': Habituation to short repeated cold-water immersions affects the response to acute hypoxia in humans. The Journal of Physiology, 588(18), 3605–3613.

Note: 32 male volunteers. The CWI group did six 5-minute immersions in 12°C water. The result was reduced catecholamine concentrations (adrenaline and noradrenaline) during hypoxic exercise — meaning the sympathetic response to a completely different stressor was attenuated by training cold. The mechanism is autonomic — the sympathetic nervous system pathway is shared between cold and hypoxia responses, so habituating one quiets the other.

_____________________

Mike T Nelson CISSN, CSCS, MSME, PhD
Associate Professor, Carrick Institute
Owner, Extreme Human Performance, LLC
Editorial Board Member, STRONG Fitness Mag

Mike T Nelson is a PhD and not a physician or registered dietitian. The contents of this email should not be taken as medical advice. It is not intended to diagnose, treat, cure, or prevent any health problem - nor is it intended to replace the advice of a physician. Always consult your physician or qualified health professional on any matters regarding your health.

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