Cold & heat exposure
Dr. Susanna Søberg
Metabolism researcher · Huberman Lab
A calm, honest field guide
Biohacks, without the hype.
Most of “biohacking” is noise. A few things genuinely move the needle, and most of those are simple, old and free: heat, cold, light, movement and sleep. This is our slowly-growing library of the protocols worth knowing, written plainly, with the experts who study them and no health claims attached.
- Protocols, not promises
- Cited to real researchers
- Updated as we go
How it compares
How it stacks up.
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What the library covers
Heat, cold, light, movement, sleep.
Five levers the library keeps coming back to.
Heat · Field guide
The sauna, properly: infrared vs traditional, and the small details nobody mentions
The sauna is a Nordic habit, so we take it seriously. Traditional Finnish saunas heat the air to roughly 80 to 100°C; infrared cabins run cooler and warm you directly. Both have a following. The honest answer is that the bulk of the long-term population research, including the well-known Finnish studies, is on the traditional hot, dry sauna, so that is where the evidence is deepest.
- 01
Protect your hair. Dry heat is hard on hair. A wool sauna hat (a Nordic staple) keeps your head and hair cooler and more comfortable.
- 02
Cool down with intent. The contrast matters. A cool shower or fresh air between rounds is part of the ritual, not an afterthought.
- 03
Timing for women. Heat tolerance can shift across the menstrual cycle; many find gentler sessions sit better at some phases. Listen to your body rather than a fixed rule.
- 04
The Bryan Johnson take. The longevity-obsessed founder runs a hot, dry sauna near 90°C for around 20 minutes, several times a week, an enthusiast’s version of the same protocol the population studies describe.
20 guides so far
The library.
A growing set of short, honest guides. Each one keeps to what the protocol is and what the research investigates, never a claim about what any drink or supplement does for you.
Light
Light
Morning light: sunlight in your eyes, and why you skip the sunglasses
Getting outside light early is one of the simplest levers for the whole day. Why the first minutes are better without sunglasses, and how little it takes.
Read article
Movement
Walking
The walk: the most underrated protocol there is
Where the 10,000-step number really came from, why the benefit curve flattens earlier than you think, and the five minutes after a meal that do the most work.
Read article
Cold
Cold exposure
The cold plunge: how cold, how long, how often
A practical primer on deliberate cold. The widely-cited weekly threshold, why the gasp reflex matters, and how to start without overdoing it.
Read article
Heat
Heat
The sauna, properly: infrared vs traditional
What the Finnish cohort data actually shows, how infrared differs from a traditional bastu, and the details for men and women that rarely get mentioned.
Read article
Contrast
Heat & cold
Contrast therapy: hot then cold, and when the order matters
Sauna then plunge feels superb and has modest evidence. But there is one situation where finishing in cold works directly against what you just trained for.
Read article
Light
Evening light
Blue light at night: what actually matters, and what is marketing
The melatonin biology is solid. The consumer fix is the weak part. What the e-reader study found, and the two levers that beat any pair of orange glasses.
Read article
Nutrition
Eating window
Fasting and the eating window: the honest state of the evidence
What the TREAT trial found when calories were left uncontrolled, where an early window genuinely helps glucose, and who should leave fasting alone entirely.
Read article
Breath
Breath
Nasal breathing: the free upgrade you are probably not using
What the nose does that the mouth cannot, the nitric oxide story, and why the mouth-taping trend needs a serious caveat before you try it.
Read article
Intensity
Movement
HIIT: what the intervals actually buy you
Intervals raise VO2max faster per minute than steady cardio. They also have a ceiling, and crossing it makes the very things you trained for worse.
Read article
Movement
Cardio
Zone 2 and the focus dividend of moving
Easy, conversational-pace movement is dull to talk about and powerful in practice. Why steady cardio earns its place in any routine.
Read article
Strength
Movement
Strength training: the longevity protocol nobody markets
Grip strength predicted mortality better than blood pressure in a study of 140,000 people. The dose needed is smaller than you think: two sessions a week.
Read article
Nervous system
Breath
Breathwork, downshifted: Wim Hof, box breathing and the slow exhale
A slow exhale is the fastest free tool for a busy nervous system. The two opposite styles, and the one safety rule that is not optional.
Read article
Supplements
Supplementation
Targeted supplementation: why a stack beats a single active
The case for formulating rather than collecting. What a full clinical dose means, why proprietary blends hide behind the word blend, and how to read a label.
Read article
Measurement
Testing
Blood work: the biohack that tells you if the others are working
The markers worth discussing with your doctor, why a normal reference range is not a target, and why ordering every test available creates problems of its own.
Read article
Recovery
Sleep
Sleep is the original biohack
Before any gadget or supplement, there is sleep. A simple, boring, effective routine, and why consistency beats every clever trick.
Read article
Nutrition
Blood sugar
Blood sugar and steady energy: flatten the curve, keep the focus
The spike-and-crash pattern behind most afternoon slumps, what actually flattens it, and the order you eat things in.
Read article
Stress
Stress
Cortisol is not the enemy: how stress chemistry really works
The hormone everyone wants to lower is also the one that gets you out of bed. What the curve should look like, and what actually flattens it in the wrong way.
Read article
Hydration
Hydration
Hydration and focus: the boring fix that actually works
Mild dehydration measurably degrades attention and mood before you feel thirsty. What the trials show, and how much is actually enough.
Read article
Mind
Connection
Connection: the longevity variable that cannot be bought
The largest effect size in the whole longevity literature comes from other people. Comparable to quitting smoking, and the item optimisation culture quietly squeezes out.
Read article
Start here
Mindset
Biohacking for skeptics: what actually moves the needle
The honest starting point. The handful of basics that earn their reputation, and the expensive gadgets you can safely ignore.
Read article
From the people who study this
A short video library on heat, cold and protocols.
Independent researchers and broadcasters discussing the protocols above, in their own words, on their own channels. Videos load from YouTube only when you press play. We are sharing the conversation, not borrowing a verdict.
Heat & cold
Swipe for moreSauna, cold plunge & the science
Dr. Susanna Søberg & Tim Spector
ZOE Science & Nutrition
A daily sauna protocol
Bryan Johnson
Blueprint · the longevity founder
Dopamine, effort & protocols
Dr. Andrew Huberman
Huberman Lab · on building drive
These are third-party discussions of general protocols, not endorsements of Thunder Honey. The speakers and channels are independent of us and are talking about heat, cold and habits in general, not our product. Videos are loaded from YouTube only when you choose to play them. Nothing here is a health claim, and none of these protocols is a statement about what Daylight does for you.
The ritual
Small habits, stacked.
A warm, no-added-caffeine ritual sits naturally alongside the basics: light, movement, heat, cold and sleep. Developed in Sweden.