The Exercise Rabbit Hole

The practical pages in this section cover what most people need: why movement is non-negotiable, how the energy systems work, how to measure and improve your physical capacity across the ten domains, and how to train for a long, capable life. The Rabbit Hole is the other half: exploring specific topics, the hidden research, the practitioner-grade protocols, and the edge cases that don’t fit the practical pages but are worth the effort if you want to understand the field properly.

This is a working collection rather than a finished section. Posts go up as the research and writing get done. The architecture is essentially blog-format: individual essays on specific topics, each going deeper than the practical pages have room for.

The notes below represent topics queued for development. They’re organised into thematic clusters rather than presented as a flat list, partly so the structure of the field is visible, partly so readers interested in one strand can see what’s coming. Some of these are genuinely difficult topics where the popular framing runs miles ahead of the underlying research; others are specific findings that deserve more attention than they typically receive.

If a topic here interests you and you’d like to see it developed sooner, that’s worth knowing. The order in which things get written depends partly on what’s most useful to readers. The practical pages will also be updated based on the utility of that research. 

Topics in Development

Temperature as Performance Variable

Straightforward, practical insights from the contemporary exercise physiology literature. Much of the content in this cluster traces to H. Craig Heller’s lab at Stanford, popularised through Andrew Huberman’s Huberman Lab podcast. Heller is the primary researcher; Huberman has been the most effective popular communicator.

• Nerves and muscles: The brain and nervous system control behaviour through lower motor neurons (which live in the spinal cord and connect to muscles). These neurons fire when instructed by central pattern generators (collections of neurons that send information down the phrenic nerve). They tell lower motor neurons to make muscles contract at specific times. Upper motor neurons are responsible for sending signals that allow deliberate, voluntary movement. There’s no such thing as “muscle memory” in the literal sense. It’s the neurons that control muscles that learn patterns. Movement learning is neural learning.
• Heat is the enemy of performance: Heating up too much is bad for all tissue health, but particularly bad for neurons, which don’t grow back when killed. The body has multiple mechanisms to protect against hyperthermia. Cellular enzymes, including ATP synthesis machinery, get modified in heat; cells stop functioning and then die. Your will to exercise further is dependent on muscle temperature. ATP can only function within a very narrow temperature range (dropping off sharply around 39-40°C). Keeping muscle temperature in range allows greater performance.
• Arterio-venous anastomoses (AVAs): the heat-exchange superhighways. Blood normally moves from arteries to capillaries to veins back to the heart. In three regions specifically: the face, the palms of the hands, and the soles of the feet. We have AVAs, direct connections between small arteries and small veins with much larger inner diameters and muscular walls, plus adrenergic neural input. The radius of these vessels controls how much blood flows through. AVAs allow heat to leave the body much faster than other venous capillary beds. These three regions also lack the dense hair coverage that other body areas evolved (in our furred ancestors). They are essentially built-in radiators.
• Palmar cooling supercharges athletic performance: Heller’s lab demonstrated that cooling the palms between sets of resistance training allowed athletes to run longer and further, lift more weight, and complete more sets and reps. In some studies, the palmar-cooling group outperformed the anabolic-steroid group on work per unit time. Cooling the palms is a way to dissipate core heat without inducing the vasoconstriction that submerging the body in ice causes. Practical protocol: hold a can of cold soda, a bag of frozen vegetables, or a designated cooling device for 10-30 seconds between sets to reset muscle temperature without shocking the rest of the body.
• Ice baths can block training adaptation: Getting into an ice bath immediately after training blocks important inflammation pathways and also blocks mTOR signalling, short-circuiting hypertrophy adaptations. Cool the body just back to its resting temperature after training (palmar cooling, brief cold shower) for performance and recovery effects, but avoid cold exposure within 4 hours of training if your goal is muscle growth. For brown fat thermogenesis, mental resilience, or adrenaline-system training, longer cold exposure has its own benefits, but those benefits and hypertrophy goals trade off against each other.
• Cardiac drift and “I quit” points: Heating up increases heart rate and effort. As body temperature climbs, cardiac drift (gradual heart rate elevation at constant work output) accelerates. The willingness to keep going is shaped substantially by core temperature, not just fuel availability. Cooling the palms protects against hyperthermia, coma, nerve injury, and death, and substantially extends the work-output threshold before fatigue kicks in.
• Why ice baths submersion is suboptimal for cooling: When you submerge your body in cold water, you trigger vasoconstriction, which paradoxically traps heat in the core. The AVA pathway works better than submersion for actual cooling. Splashing the face with cold water, holding cold objects with the palms, or running cold water over the wrists is more effective per unit time than full-body immersion for performance recovery.
• Cooling for fat loss vs cooling for performance: different goals, different protocols. The cold exposure protocols for stimulating brown fat thermogenesis and converting beige fat (covered below in Fat Loss Neurochemistry) involve longer duration cold and deliberate shivering. The palmar cooling protocol for athletic performance is brief and targeted at AVA-mediated core temperature regulation, not metabolic adaptation. The same intervention done differently produces different outcomes.
• Stimulants and temperature: Caffeine and other stimulants pre-workout raise body temperature and limit the work you can do. If you’re caffeine-adapted and your heart rate doesn’t skyrocket, you may not vasoconstrict until after caffeine wears off (and may briefly vasodilate). Those who aren’t adapted will vasoconstrict and limit performance. The general principle: get the warm-up benefits of caffeine without overheating the muscles. Alcohol is a vasodilator and can cool you down post-training, but the negative effects outweigh the cooling benefit for almost any purpose. NSAIDs artificially lower body temperature but have side effects on the liver, kidneys, and electrolyte balance that make them a poor choice for performance support.

Growth Hormone Deep Dive

The hormonal cascade behind growth, repair, and metabolism. GHRH (growth hormone-releasing hormone) tells the pituitary to release growth hormone. GH then acts on tissues, muscles, and bone to increase metabolism and tissue repair. Insufficient GH produces short stature in development. Excess GH produces acromegaly. GH levels drop substantially across the lifespan; recovery from training slows in parallel.

• Natural GH triggers: Slow-wave sleep with low blood insulin is the foundational trigger. Eating too close to bedtime suppresses GH release; don’t eat within 2 hours of sleep if GH is a priority. Delta wave brain activity (correlated with SWS) triggers the neurons that release GHRH. During the day, you can theoretically access GH release by reaching delta wave states briefly (deep meditation, NSDR, certain hypnotic states).
• Low-dose melatonin supplementation (around 500 mcg) may aid the transition into delta wave sleep, indirectly supporting GH release. The dose matters; higher doses don’t produce the same effect and may have other consequences.

Specific exercise protocols that stimulate GH:

• Weight training or endurance training limited to 60 minutes
• Get warm (genuinely warm the body) before training to accelerate GH response
• High-intensity work not taken to absolute failure
• Sex differences in timing: women access IGF-1 and GH early in weight training (within the first 30 minutes); men need longer sessions to access the same response

The 6×10 testosterone protocol: 6 sets of 10 repetitions at approximately 80% of 1RM, with 2-minute rest between sets, on compound lifts. Drives both metabolic stress and mechanical load high enough to trigger acute testosterone elevation. 10×6 (same volume, different distribution) doesn’t produce the same effect because it doesn’t drive metabolic load as hard. 10×10 (extending volume) starts producing cortisol elevation that offsets testosterone benefits.

Heat protocols for GH release: GHRH neurons sit very close to the temperature-regulation neurons in the hypothalamus and may be intermixed. Temperature has a profound effect on GH increase. Sauna sessions at 80-100°C (176-215°F) for 20-30 minutes have been shown to increase GH by up to 16-fold (1,600%). Following sauna with a cooling period for 3 days in a row produces the largest effect. If you don’t have a sauna, wearing plastic or insulating layers can mimic some of the temperature effect, though with greater risk and lower effectiveness.

Supplements that elevate GH: Arginine (3-9g) and ornithine can increase GH levels, the prerequisite being low blood sugar. Arginine is also involved in vasodilation. Increasing arginine specifically to elevate GH will interfere with the exercise-induced increase; the effects aren’t synergistic. L-citrulline is metabolised differently and has greater vasodilation effects than arginine itself; it also lowers blood pressure. Power output increases, fatigue decreases, and blood sugar drops. Caveat for both: cold sores from herpes simplex can flare with arginine/citrulline supplementation, since the virus lives on neurons, and these amino acids feed.

Prescription GH and peptide therapeutics: Most prescription GH is synthesised. Anything exogenous shuts down endogenous production. Not advisable to take it forever. Peptides (strings of amino acids that resemble target hormones) are increasingly common in the longevity/performance underground; they’re substantially less well-studied than the basic exercise and dietary protocols. The Hollywood industry uses peptides aggressively for rapid physique changes; long-term safety data is limited.

Fat Loss Neurochemistry

The neural and hormonal control of fat loss, a topic that’s been substantially clarified by research over the past two decades, while popular framings have lagged behind.

• The first law of fat loss: Calories in vs calories out is the fundamental concept. Highly processed food can alter the way we utilise food and contribute to obesity in ways that bypass the conscious calorie-counting model, but caloric intake remains the major variable. The calories-burned side is influenced by hormones, thermogenesis, basal metabolism, thyroid function, and the neural innervation of body fat, which is where the conversation gets genuinely interesting.
• Neurons connect directly to fat: Body fat is innervated by sympathetic neurons that release norepinephrine directly into adipose tissue, triggering lipolysis (the breakdown of stored fat into fatty acids and glycerol for use elsewhere). This is a separate system from the adrenal glands releasing adrenaline systemically; the neural innervation is local, targeted, and far more responsive to specific stimuli. This explains many of the previously puzzling findings about why some interventions work for fat loss when general caloric reasoning suggested they shouldn’t.

The 5 pillars of metabolism:

1. Sleep, light exposure, and circadian timing: Covered exhaustively in Sleep & Circadian Rhythm. Foundational. Sleep deprivation produces measurable insulin resistance, leptin dysregulation, and hunger hormone elevation within days.
2. Essential fatty acids: Particularly EPA above 1,000 mg/day, ideally from fatty fish or grass-fed meat. Fish oil supplements are second-best. EPA has antidepressant effects, supports healthy metabolic function, and reduces inflammation.
3. Glutamine: For sugar cravings, the amino acid glutamine can interrupt the craving signal. It also assists with healing intestinal permeability (“leaky gut”). The caveat: glutamine alone can raise blood sugar, and certain cancers preferentially metabolise glutamine for fuel.
4. Microbiome: Eat fermented foods. Covered in detail in Microbiome Basics.
5. Thyroid function: If iodine, selenium, and thyroid levels are low, metabolic function won’t be optimal. Thyroid dysfunction is one of the most underdiagnosed causes of stubborn weight gain and chronic fatigue.

Mindset and beliefs about exercise matter measurably: A study found that simply being told that movement is good for you (specifically, that it can lead to weight loss and cardiovascular health benefits) led to more body fat loss and positive waist-to-hip ratio changes in subjects doing the same actual movement. How we think about a process changes physical results.

Lipolysis vs oxidation: Lipolysis is moving fat from storage cells, breaking the glycerol backbone from fatty acids using lipase enzymes. The fatty acids are released into the bloodstream and become potential fuel. The second step is oxidation: those fatty acids need to enter mitochondria and be burned. If not oxidised, they can return to body fat storage. The nervous system can be influenced to increase mobilisation, oxidation, or both. Many interventions that “should” cause fat loss fail because they trigger one step without the other.

The role of adrenaline from neurons, not adrenal glands: A common mistake in older literature: the adrenal glands’ release of adrenaline was thought to be what stimulates fat oxidation. The actual adrenaline driving fat oxidation comes from neurons that connect directly to fat tissue. It’s local, not systemic.

Fidgeting and shivering: One of the most powerful ways to stimulate neural adrenaline release into fat is shivering. Subtle forms of movement can substantially increase fat loss. People who fidget can overeat without proportional weight gain. Knee bouncing, head bobbing, pacing, standing-up-and-down patterns, and rapid staccato movements can burn 800-2,500 extra calories per day compared with sedentary controls. James Levine at Mayo Clinic coined the term NEAT (Non-Exercise Activity Thermogenesis) for this.

• NEAT works best for people who are slightly overweight and averse to formal exercise. For lean and already-active people, the marginal benefit is smaller. For sedentary overweight people, NEAT can be the most powerful single intervention available.

Shivering and brown fat. White fat is energy storage with few mitochondria. Brown fat is brown because it’s packed with mitochondria, which can take food energy, break it down, and convert it within the cell into heat (rather than ATP). Beige fat is intermediate – white fat that has become more brown-fat-like through cold exposure.

• Cold exposure triggers adrenaline release from the adrenals and norepinephrine from the neurons that connect to fat. This converts beige cells toward brown phenotype and increases thermogenic intensity in existing brown fat. The shivering itself releases succinate, which acts on brown fat to further increase the burn rate. Over time, this converts beige toward brown. Without the shiver, you don’t get the succinate effect.

Cold-shiver protocol for fat loss:

• Get into water that’s just uncomfortable subjectively (not so cold it shocks your heart), 1-5 times per week
• Get in until you genuinely shiver
• Get out for 1-3 minutes
• Re-enter and shiver again
• Repeat 3 times
• The cooling-to-rewarming point is where the shivering response usually kicks in

The protocols at thecoldplunge.com cover this in more detail. Don’t get hypothermic. Don’t shock your heart with overly cold water if you’re new to it.

Why babies can’t shiver: Newborns have substantial brown fat but lack the neural wiring to shiver. As they develop, the neurons connect up and shivering becomes possible. Brown fat reserves can be lost over a lifetime if cold exposure is absent.

Don’t apply ice to the back of the neck or wear “cold underpants” expecting fat loss: Use the minimum effective stimulus. More cold doesn’t produce more fat loss linearly; the dose-response curve is shallow at high doses. Sporadic, intentional cold exposure is more effective than chronic adaptation, which dampens the response.

Irisin is underwhelming; succinate is the real signal: Earlier popular framing emphasised irisin (a hormone released during exercise that supposedly converted white fat to brown). Subsequent research has shown succinate plays a larger role. Cold-adapted people release less epinephrine and succinate per unit cold exposure, which is part of why intermittent rather than chronic cold exposure produces better thermogenic effects.

Spot reduction may have some basis after all: Fat metabolism happens systemically, but evidence is emerging that targeted exercise can trigger neurons that innervate specific fat pads, increasing epinephrine release in those areas and accelerating local mobilisation. The effect is modest and easy to short-circuit through training adaptation. Novel forms of exercise that involve the target fat pad may produce small spot-specific effects. The popular “do crunches to lose belly fat” framing was wrong about the mechanism, but accidentally right that local activation can produce some local mobilisation.

Exercise modality and fat loss:

• SIT (Sprint Interval Training): 8-30 second all-out efforts followed by walking back. Dramatic glycogen depletion.
• HIIT: Submaximal (80-100% VO2 max) 60-240 second efforts with brief recovery
• MICT: Moderate-intensity continuous training (zone 2), 20-60 minutes at 40-60% VO2 max or 55-70% max heart rate

Insulin and fat oxidation: Insulin suppresses fat oxidation. However, glucose intake before training has mixed effects in the research on fat mobilisation. The interaction is more complex than the popular “fasted training burns more fat” suggests.

The 90-minute rule: At about 90 minutes of moderate-intensity training, fasted exercisers begin to burn more fat than fed exercisers. That’s a lot of exercise. Probably relevant for hikers, not for typical runners or swimmers.

If HIIT is done first, the fasting benefit arrives sooner: Following HIIT or very-high-intensity work for 20-60 minutes with zone 2 cardio for fat burning produces glycogen depletion that accelerates the fed-to-fasted crossover. This depends on starting glycogen stores and insulin levels.

Post-exercise metabolic increases: HIIT and sprints (anaerobic work) tap into glycogen stores more rapidly than moderate-intensity work. The percentage of fat burned after exercise is higher in HIIT subjects. Low-intensity exercise burns more fat during the session and produces higher glycogen afterwards. HIIT followed by moderate-intensity work appears to be the most efficient combination overall.

A protocol for exercise-induced fat loss: 3-4 times per week, HIIT followed by nothing or moderate-to-low-intensity work afterwards. Big movements deploy more adrenaline and norepinephrine from neurons signalling fat oxidation; low-intensity work doesn’t. Adrenaline is the effector and trigger.

Compounds and supplements for fat loss:

• Caffeine. Up to 400 mg can support fat oxidation through epinephrine elevation, if you’re caffeine-adapted. If not adapted, vasoconstriction lowers performance.
• Ephedrine and fenfluramine. Removed from the market due to overheating and cardiovascular safety concerns.
• GLP-1 agonists. Yerba mate triggers GLP-1 release naturally. GLP-1 is in the glucagon pathway; fat is mobilised and oxidised in the mitochondria for ATP. High insulin prevents this process; glucagon facilitates it through GLP-1 increases. Ingesting mate before exercise increases fat oxidation. You can reuse the mate tea to extract more compounds. Semaglutide (Ozempic, Wegovy) is a pharmaceutical GLP-1 analogue with substantially larger effects and substantially more side-effect risk. Guayusa tea leaves are sweeter than mate with similar effects.
• Berberine and metformin. Used for reducing blood glucose. Keeping insulin low facilitates fat oxidation. Berberine is the natural compound; metformin is the pharmaceutical. Both have ongoing research interests in longevity contexts (covered in Nutrition).
• Acetyl-L-carnitine. After fat is mobilised, it needs to be oxidised. GLP-1 and low insulin help. Acetyl-L-carnitine helps directly by transporting fatty acids into mitochondria for conversion to ATP. It also reduces ammonia, C-reactive protein, blood glucose, and total cholesterol, modifies the glucagon pathway, improves rates of pregnancy in both sexes, reduces blood pressure, and reduces fatigue.

Adherence beats optimality: As Christopher Gardner’s work at Stanford has demonstrated repeatedly, if you can’t stick with something, it isn’t worth doing. The most important variable is keeping insulin levels low enough to allow fat oxidation; the specific dietary approach to get there is less critical than consistency.

Resistance Training Deep Dive

The neural and mechanical biology of getting stronger, with substantial primary research from the Henneman lineage forward.

• Muscle is a slave to the nervous system: The nervous system manages movement through upper motor neurons, lower motor neurons, and central pattern generators. Muscles contract through the release of acetylcholine at the neuromuscular junction. It’s the nerve-to-muscle connection that triggers hypertrophy, not the muscle in isolation.
• Why our brains are so large: The human brain is so large in part because of its dedication to vision and movement. Engaging in diverse, complex, learnable movements. Other animals don’t have as many upper motor neurons to execute as many varied functions. Movement learning is one of the most metabolically expensive things the brain does, and one of the most distinctly human capacities.
• Flexors, extensors, and mutual inhibition: When a flexor is activated, the extensor is inhibited (reciprocal innervation, or mutual inhibition). Stabiliser muscles operate independently. This pattern is foundational to PNF stretching (covered below) and to antagonistic muscle group training (also below).
• How muscles use energy: Muscles run on glycolysis as the immediate fuel pathway. Available glucose is broken into two sets of 3-carbon pyruvates, generating small amounts of ATP. With sufficient oxygen, the pyruvate enters mitochondria, and 28-30 ATP are produced. Movement is metabolically expensive at the cellular level.
• The “burn” isn’t lactic acid: A common misunderstanding. Pyruvate is converted to lactate with the addition of a hydrogen ion. Lactate buffers acidity and acts as a fuel and a hormone. The burn is acidity, not lactate; lactate is present to suppress the burn while serving as additional fuel.
• Lactate as a brain signal: When you push hard enough to feel “the burn” for roughly 10% of your workouts, you trigger lactate accumulation that acts as a hormonal signal to the heart, liver, and brain. This influences function positively at all three sites. Lactate improves neuron function via astrocytes; breathing properly through the burn is what allows lactate to act (lactate’s beneficial effects require oxygen being present).
• Neurogenesis in humans is limited: Very little evidence supports enhanced neurogenesis (creation of new neurons) in humans through exercise. The cognitive benefits come primarily from hormonal signals (like IGF-1) and neural plasticity, not from adding new neurons. This is probably better for longevity; unlimited neurogenesis would create stability problems.
• Henneman’s size principle in detail: Elwood Henneman’s 1965 Journal of Neurophysiology paper established that we recruit motor units in a pattern that staircases from low threshold to high threshold as force demand increases. Conservation of energy in action. The more force required, the more (and larger) motor units come online. The high-threshold motor units that drive the largest growth and strength gains only activate when low-threshold units can’t meet the demand. Hence, the practical implication: either heavy loads (above ~70% 1RM) or near-failure efforts at lower loads.
• The 30-80% 1RM range covers most growth: Heavy weights can increase size and strength, but aren’t necessary for hypertrophy. For pure maximal strength, you need heavy loads; for hypertrophy, the load range is flexible as long as proximity to failure is sufficient.
• The three stimuli for growth – stress, tension, and damage: Myosin filaments thicken; the nerve tells muscle fibres to get stronger and bigger. Each stimulus contributes; maximal growth typically requires all three.
• Identifying your strength-and-growth-friendly muscles: Your ability to independently contract muscles to the point of cramping signals good upper motor neuron control of that muscle, which predicts good response to strength and hypertrophy training. Muscles where you struggle to even consciously contract them are unlikely to respond as well; they need more skill work before they can become heavy-loading targets.
• Distributed vs local effort – why getting stronger ≠ growing specific muscles: If you attach ankle weights to improve calf strength, the body takes the more efficient path and uses hip flexors instead. Getting better at compound exercises generally means avoiding isolating individual muscle contractions. The body will route around isolated muscle work unless you force it not to.
• How much resistance for most people: Once you know your rough 1RM with good form, the most beneficial range for general work is 30-80% of 1RM with varying rep ranges. Heavy work in the 80%+ range is needed specifically for maximal strength.
• Sets per week for muscle growth: For untrained individuals, the variable is enough sets per muscle per week. 2-20 sets per week per muscle group is the working range. 5 sets per muscle group taken close to failure is sufficient to maintain muscle. Going to actual failure on roughly 10% of sets is sufficient; the rest should end “near” failure with 1-3 reps in reserve.
• Number of sets is inversely related to ability to generate high-force contractions: The better you can generate a muscular contraction, the fewer sets you need. Sets and intensity trade off against each other.
• 45-60 minutes is a reasonable workout ceiling: Some individuals are so good at generating force that more volume is less effective than less. Quality matters more than duration at high training ages.
• Range of motion and movement speed: Learning to move weights as fast as you can under moderate loads improves speed and explosiveness; most of the effect comes from neural adaptations (changes in upper motor neuron firing patterns). For pure strength, slowing down the weight as things get harder is a key parameter for recruiting high-threshold motor units; don’t use momentum. For hypertrophy, as long as you aren’t moving too quickly (which would distribute load across muscles inefficiently), speed doesn’t substantially affect outcomes.
• Focal contractions between sets: Flexing the target muscle hard for 30 seconds between sets can build a stronger nerve-to-muscle connection, increasing stress, tension, and damage on subsequent sets. This won’t improve performance during your working sets, but it can amplify hypertrophy signals.
• The 6×10 testosterone protocol (the Duncan French interview content with Huberman): 6 sets of 10 reps at approximately 80% of 1RM with 2-minute rest between sets on compound exercises (squat, deadlift, bench, overhead press). The protocol drives both mechanical tension (intensity factor) and metabolic stress (volume factor) high enough to trigger acute testosterone elevation. 10×6 (same total volume but different distribution) doesn’t drive metabolic load as effectively. 10×10 starts producing excessive cortisol that offsets testosterone benefits. The 6×10 hits the sweet spot for natural testosterone elevation.
• Speed of reps doesn’t substantially affect hypertrophy: Half-second to 8-second rep speeds produce similar growth outcomes when proximity to failure is similar. If your goal is performance (strength), don’t flex between sets. For strength gains, more rest. Use palmar cooling to improve recovery between sets. For hypertrophy, you can target a specific muscle by pre-exhausting/isolating before compound work.
• Post-training parasympathetic downshift: After training, engage parasympathetic tools to accelerate recovery. The physiological sigh (covered in Breathwork Basics). Some people use physiological sighs between sets to recover their nervous system. After training, NSDR (non-sleep deep rest), meditation, or breathwork.
• Cold exposure timing: Using cold showers or ice baths less than 4 hours after training may interfere with inflammation pathways and block mTOR. Schedule cold exposure outside this window if hypertrophy is your goal.
• Antihistamines and anti-inflammatory drugs: Can block benefits of cardiovascular exercise and some benefits of resistance training by blocking mast cells. Muscle damage and inflammation are the signals for change. Painkillers block pain signals that you may need as physiological feedback.
• Foundational supplements for recovery: EPA (omega-3 fatty acids), vitamin D3, magnesium malate (helpful for DOMS and sleep). DOMS aren’t necessary for muscle growth. Massage, fascial release, and similar work can help relieve sore muscles without blocking adaptation.
• Sodium, potassium, and magnesium for nerve-to-muscle firing: Nerve cells communicate through ion movement (salt). How much salt you need depends on caffeine intake, water intake, and sweat losses.
• Creatine for strength and brain: For a 180-pound person, 5g per day is sufficient. It’s a fuel source for early bouts of high-intensity activity. No need to load. Performance-enhancing: increased power output, better hydration, reduced fatigue, improved cognition after traumatic brain injury. Can increase DHT, and some people experience accelerated hair-growth changes.
• Beta-alanine, beet juice; arginine and citrulline cautions: Beta-alanine (2-5g) supports slightly longer exercise capacity through carnosine synthesis. Beet juice (nitrate) supports longer-duration endurance. Arginine and citrulline can be useful but may trigger herpes simplex cold sores in people who carry the virus, since it lives on neurons these amino acids feed.
• Protein density and meal frequency: Caloric surplus of 10-15%. To support muscle synthesis, 700-3,000 mg of leucine per meal from whole foods is the target (covered in The Longevity Program and Macronutrient & Hydration Basics). Animal proteins have higher leucine density than plants. Eat 3-4 times per day; the old-school 6-7 meals per day recommendation isn’t necessary for muscle growth.
• Hard workouts and cognitive work: Hard bouts of exercise with focused muscular contractions can produce reduced cerebral oxygenation. Schedule hard mental work for times when your body expects physical training; the body and mind predict activity rhythmically.
• Time of day for resistance training: For hypertrophy and strength, time of day doesn’t substantially affect outcomes. Evidence for better performance in the afternoon exists, but doesn’t translate to better training adaptations.
• Maintaining muscle: At least 5 sets per muscle group per week of resistance training, trained near failure. 
• Duncan French notes from the Huberman interview:
  • How certain exercises increase testosterone. Mechanical stress response causes downstream regulation of testosterone at the gonads. Catecholamines signal the cascade through the HPA axis, releasing cortisol and influencing the adrenal medulla to release androgens.
  • Females have testosterone released primarily from the adrenal medulla rather than the gonads. To a lesser extent than males, but resistance training works as a stressor to elevate the anabolic state and drive consequent muscle tissue growth. In men, the field is divided about how much acute resistance training elevations contribute versus longitudinal habitual basal level elevations. Probably both.
  • Testosterone has growth effects on tendons, ligaments, neural tissue, and bone, wherever androgen receptors are present.
  • Cold exposure for mindset vs muscle growth. Cold clamps down on the vasculature, making the redistribution of circulation challenging. For mindset (mental resilience, stress tolerance), cold exposure is excellent because the body doesn’t distinguish between cold stress response and heavy weight training response. For muscle growth, however, an ice bath dampens mTOR and hypertrophy signalling. For recovery during competition periods when quality matters most, cold can be useful; for muscle-building phases, avoid cold immediately post-training.
  • Skill development. Rehearsal of accurate movements. Fatigue decreases neuronal potential. Shorter sessions at higher quality beat longer sessions at degraded quality.
  • Hard exercise and brain fog. Fueling the brain and muscles during hard training exhausts you and leaves little for hard mental work later. Skill work, specifically, can be very taxing.
  • Low-carb vs all-macronutrient diets for high-intensity athletes. French wouldn’t advocate ketogenic diets for high-intensity athletes. After events, ketones can refuel the brain and offset damage after head trauma. Cycling ketogenic periods may produce better metabolic management and efficiency while operating at lower intensity (using lipids and fats); his high-intensity athletes use a “keto-ish” diet but fuel sessions with carbohydrates (pre, during, post).
  • Metabolic efficiency and needs-based eating. Teach the body to use fat at lower intensity and carbohydrate at higher intensity. Don’t expend glucose stores early in long efforts.
  • UFC and MMA performance. Degrees of freedom in mixed martial arts are exponential. Fighters often don’t know who or when they’re fighting until a month prior, making training management challenging. Mental resilience is high in this field. Type-A personalities tend to struggle to excel because they don’t experiment patiently.
  • Heat, sweating, heat shock proteins. HSPs are driven by stress exposure. 15 minutes in a hot sauna (90°C/200°F) is a starting protocol. Building heat tolerance takes 8-10 weeks before a fight.
  • 12-week training programs. Regression or progression is determined after 12 weeks. Shorter cycles produce too much measurement noise.

Recovery diagnostics:

1. HRV at a medium level (not too high or too low). Both extremes indicate something is off.
2. Grip strength testing in the morning. Squeeze your fist or a grip tool, or squeeze a floor scale. If you’re about 10% lower than normal, you may need more recovery.
3. CO2 tolerance test.
4. Tap a table with two fingers as fast as you can in 15 seconds and compare to your normal baseline. 

Endurance Deep Dive

The four kinds of endurance:

1. Muscular endurance. The ability for muscles to perform work over time. Failure is muscular fatigue, not cardiovascular. Examples: 12-100 repetitions of bodyweight exercise. Improves posture, sustained-effort movements, resilience. Training: 3-5 sets of 12-100 reps, 30-180 seconds rest. No major eccentric component (eccentric loading causes DOMS; jumping is unsuitable; kettlebell swings work). Pushups, planks, sleds, wall sits.
2. Long-duration endurance (12+ minutes). One set, less than 100% VO2 max, dependent on efficiency of movement and fuel utilisation. Builds mitochondrial density and the capillary beds in muscle and brain. Glycogen used first; ruminating burns neural glucose and epinephrine, which is part of why mental endurance and physical endurance correlate. Important: builds capillary beds in muscle and brain, which is the underlying reason aerobic exercise enhances cognitive function over time.
3. Anaerobic HIIT. 3-12 sets, work:rest ratios of 3:1 or 1:3. Reps performed at whatever speed allows good form. 30 seconds hard pedaling or squats, 10 seconds rest. Timing depends on whether movement quality is intact. Don’t injure yourself or execute bad movement patterns. Quality matters more if weights are involved.
4. Aerobic HIIT. 3-12 sets at 1:1 work:rest ratio. Improves all energy systems. Run 7 minutes, rest 7 minutes. Better practice for marathon running than excessive endurance volume. Engages nerve-to-muscle firing, improves ATP and mitochondrial function in muscles, allows blood to deliver more oxygen to muscle and brain, allows the heart to deliver more overall. Only 2-3 times per week because of intensity. At least 24 hours of rest between aerobic HIIT sessions.

The kinds of endurance, with substantial input from Andy Galpin (Cal State Fullerton) and Huberman’s synthesis of the broader exercise physiology literature.

• The 5 things that allow us to persist or quit: Neurons, muscles, blood, heart, and lungs. Endurance limitations come from one or more of these systems. Knowing which one is your limiter at a given moment is the practical question.
• Why you quit, it is in your mind, but it’s biological: A class of neurons in the brain shuts off when we quit. The locus coeruleus releases epinephrine; when it reaches threshold, glia (support cells in the nervous system) notice and shut down the system to protect against damage. Manipulating the visual environment can trick people into believing they’re making progress or going nowhere (like being in a current), substantially changing their endurance performance. If you could extend the time before glia shut down epinephrine release by releasing more epinephrine, you could postpone quitting.
• The “90% mental” myth: Doesn’t make sense as a claim. Performance is 100% neural and 100% physiological; they aren’t separate systems, and both require nervous system function.
• Carbohydrates and electrolytes: Nerves need glucose (unless keto-adapted) and electrolytes (sodium, potassium, magnesium). Performance is also pH-dependent. Muscles use the phosphocreatine system initially, then glucose, then glycogen.
• Phospho-creatine, glycogen, pH, temperature: Phosphocreatine is short-lived and found in muscle. Glycogen is stored carbohydrate in muscles. pH is important for muscular contraction. Temperature is important for sustained contractions (covered in Temperature as Performance Variable).
• Using blood, heart, and lungs to go longer, further, harder: Glucose in the blood, fatty acids, oxygen. The heart moves blood and oxygen to provide fuel to the muscles and the brain. Lungs provide oxygen. The liver provides carbohydrates as an additional fuel source.

When asking what’s limiting your performance, the question is: nerves, muscles, blood, heart, or lungs?

• Building a stronger heart and better brain: Breathing hard with the heart working hard circulates blood faster and increases oxygen utilisation in muscles. The amount of blood returning causes additional work and eccentric loading on the left ventricle, thickening the cardiac muscle so it can pump more strongly. More work per stroke means a lower resting heart rate. Cognitive function improves with greater vasculature and oxygen delivery.
• Resistance and weight training and the brain: Strength and hypertrophy work, especially getting into “the burn,” produces positive brain effects. Less research because mice don’t easily do resistance training. Endurance training has greater positive effects on the brain through oxygenation.
• The strength-endurance tradeoff: Just weight training produces strength but not the oxygenation benefits of cardio. Combine both for full benefit. At least 1-2 rest days per week. Use the CO2 tolerance test to check recovery.
• Breathing during endurance, explosive, and weight training: Oxygen delivery to muscles and brain determines performance. Nasal breathing is more efficient. Nasal breathing as much as possible; mouth breathing is useful for strong exhale.
• Intercostals and diaphragmatic breathing: Warming up intercostal muscles before endurance work allows deeper breathing and greater oxygenation. Expanding the chest with breathing exercises pre-workout primes the intercostals.
• Eliminating the side cramp with physiological sighs: Shallow breathing can produce phrenic nerve referred pain (the “side stitch”). Relief: a double inhale through the nose followed by a long sigh exhale through the mouth.
• Accelerating through “the wall” Different muscle fibres use energy differently. Increasing speed shifts muscles to a different fuel source. If completely depleted, this isn’t an option. Athletes now ingest ketones during long efforts alongside carbohydrates instead of relying purely on carbs.
• Hydration: the Galpin equation:
  • Body weight in pounds/30 = fluid to drink in ounces every 15 minutes of exercise.
  • Or roughly: divide your body weight in kg by 28 to get fluid in ml every 15 minutes. We need water and electrolytes for nerves to function. The amount required is 1-5 pounds of water per hour of training, depending on temperature. Once you lose 1-4% of body weight in water, work capacity drops 20-30%, and mental function declines. Urine colour gives an indication. Turn up hydrated.
  • Gastric emptying is hindered above 70% of VO2 max. You can train the body to relax abdominal muscles during higher-intensity work to allow fluid consumption.
• Boosting mitochondrial density with cold: Wait at least 6 hours between cold exposure and training to prevent interference. Cold exposure separated from training appears beneficial for mitochondrial biogenesis.
• Accelerating recovery with 5-minute parasympathetic downshift: NSDR, meditation, breathwork. Slow, pure nasal breathing. Mellow out for 5-20 minutes after training.
• Leveraging the visual system during effort: Vision contraction triggers neurons in the thalamus to activate alertness systems. Focusing on a single point makes effort feel easier than picking out many milestones. Dilating vision in between milestones can relax the nervous system, taking less mental and visual effort during longer efforts.
• The physiological basis of your “extra gear” When somebody runs to the finish line by using a visual target (a focus point), they tap into a different energy system and trigger epinephrine release. Steve Prefontaine’s famous late-race surges had a biological basis: visual targeting plus epinephrine.

The CO2 Tolerance Test

A measurement of your capacity to engage the parasympathetic nervous system and consciously control your diaphragm. Useful for assessing recovery state across training.

The protocol:

1. Inhale deeply through the nose
2. Exhale through the mouth
3. Repeat 4 times
4. On the 5th inhale, expand the lungs as much as you can
5. Set a timer
6. Release the exhale as slowly as you can through your mouth (CO2 blow-off)
7. Stop the timer once you run out of air

Interpretation:

• 2+ minutes: heroic level, you have excellent diaphragmatic control
• 30 seconds: typical
• 20 seconds: relatively fast/poor
• Less than 25-20 seconds: probably not recovered
• 30-60 seconds: green zone for additional training work
• Above 60 seconds: nervous system fully ready

Diagnostic use:

If your numbers are starting to drop by 15-20% from your baseline, you’re veering toward incomplete recovery. Pause training, lower intensity, or add recovery days. This is more sensitive than HRV for some people and complements HRV nicely as a dual-marker recovery check.

Stretch Protocol Deep Dive

From Huberman’s Neural Network Newsletter synthesis of the stretching research, building on primary work from Wyon et al. on microstretching, Bandy et al. on static stretching duration, and Palma et al. on stretching frequency.

• Benefits of stretching: Increasing flexibility contributes to general health: improved balance and stability, better posture, smoother gait, elevated physical performance, and reduced pain. Stretching can reduce inflammation. Some data in animal models suggest it may even reduce the risk of cancer.
• No need to stretch intensely (or for very long): Wyon et al. showed that microstretching (30-40% intensity, where 100% would be slightly painful) is more effective than aggressive stretching for long-term flexibility gains. Whatever stretching routine you adopt, you don’t need to push to the point of pain. Consistency and frequency are the variables that produce long-term flexibility, not intensity.
• Static stretching is the most effective for long-term flexibility: While dynamic and ballistic stretching (involving swinging limbs and momentum) can be helpful before performance-based activity and sports, a routine built on static stretching is the most effective at increasing long-term flexibility.

Bandy et al. found that 30 seconds is the minimum threshold for flexibility benefit per static hold. Palma et al. found that a minimum stretching frequency of 5 times per week, with a total stretching time of 5 minutes per muscle group per week, was optimal.

Static stretching protocol basics:

• 2-4 sets of 30-second static holds per muscle group
• 5 days per week
• Minimum 5 minutes total per muscle group per week
• Alternative: 60-second holds with reduced frequency

Note: The goal of 5 minutes per muscle group per week can be achieved with longer holds (60 seconds instead of 30) and reduced frequency (every other day instead of 5 times per week). The research shows consistency beats duration and intensity.

PNF stretching (Proprioceptive Neuromuscular Facilitation).

• The nervous system and muscles are in constant communication to keep joints within a safe range. Intrafusal spindle fibres communicate muscle stretch to the spinal cord and brain. If a stretch becomes excessive, spindle fibres activate motor neurons that cause the associated muscle to rapidly contract, bringing joints back to a safe range.
• Golgi tendon organs (GTOs) sense load or tension on a muscle. If GTOs sense too high a load, they communicate to the spinal cord and inhibit the motor neuron’s ability to contract the muscle, preventing potential injury.
• PNF stretching (also called “contract-relax stretching”) leverages these mechanisms to increase flexibility. PNF combines stretching and contracting of muscles to increase joint range of motion and, in some cases, contractile strength.

Antagonistic muscle group training

• Alternating exercises of antagonistic muscle groups can improve overall performance. If you alternate rows or pull-ups with bench presses or shoulder presses, the chest, shoulders, and triceps get a period to “relax” while biceps and back are engaged, and back and biceps relax during pushing exercises. There’s crossover activation, but the alternating push-pull pattern is effective.
• When the biceps contract, the triceps experience reciprocal inhibition through spindle fibres releasing while GTOs are activated. Autogenic inhibition is the contraction of one muscle group, “relaxing” the antagonistic group.

Overtraining Hypotheses

The mechanistic models for why overtraining produces the symptoms it does. Drawn from the broader exercise physiology and endocrinology literature. None of these is mutually exclusive; overtraining likely involves several of them simultaneously, with the dominant mechanism varying by athlete and training context.

Hypotheses for the cause of overtraining:

• Glycogen hypothesis: Low reserves manifesting as fatigue. Inability to replenish glycogen between training sessions produces an accumulated deficit.
• CNS fatigue: Crucial factor being serotonin and its dysregulation. The central nervous system progressively loses the ability to drive intense effort.
• Glutamine hypothesis: Low glutamine levels in food and the body are predisposing factors for infections and chronic fatigue.
• Oxidative stress hypothesis: High oxidative stress, silent inflammation, muscle fatigue, and muscle soreness. The body’s antioxidant defences can’t keep up with the rate of free radical production.
• ANS hypothesis: Imbalance of the sympathetic and parasympathetic nervous systems. Evident from HRV analysis.
• Hypothalamus hypothesis: Changes in the HPA (hypothalamic-pituitary-adrenal) axis and HPG (hypothalamic-pituitary-gonadal) axis affect levels of cortisol, ACTH, testosterone, and other hormones. A low ratio of cortisol to testosterone may indicate the shift.
• Cytokine hypothesis: Continuous hard training and insufficient rest cause a chronic state of inflammation and cytokine storm (IL-1β, IL-6, TNF-α). High levels may cause decreased appetite, sleep disorders, depression, and a general feeling of illness.

Factors that promote the onset of overtraining syndrome:

• Increased training load without adequate rest
• Lack of diversity in exercise (chronic repetitive stress on the same systems)
• Excessive competing
• Trouble sleeping
• Low energy intake from food, micronutrient deficiency
• Social and emotional stress factors (family, work, relationships)
• Previous illness
• Exposure to high altitudes
• Heatstroke
• Severe physical impact or shock, particularly in the head area

Laboratory tests for confirming overtraining:

• Immunological markers to check the immune state
• Cortisol and testosterone (saliva for cortisol and DHEA; urine for cortisol metabolites; ratio of cortisol to cortisone)
• Thyroid hormones (TSH, T4, T3, reverse T3, autoimmune antibodies if needed)
• Creatine kinase (reflects muscle breakdown)
• Iron balance (ferritin, transferrin saturation, serum iron, transferrin)
• Oxidative stress (FRAS test)
• Energy metabolism and mitochondria function (amino acids, fatty acids, organic acids, vitamins and minerals, oxidative stress, citric acid cycle, methylation)

Overtraining syndrome is the logical extension of the constrained daily energy budget covered in Energy Systems. When training exceeds what the body can recover from, other functions get progressively suppressed, and once enough are suppressed for long enough, the cascade produces the overtraining presentation. The treatment is rest, not more training.

Greenfield’s Boundless Programme

Ben Greenfield’s Boundless contains a substantial practitioner-grade programme that synthesises the longevity training research from a hands-on perspective. We touched on the Alternative Longevity Programme summary in The Longevity Program; this section covers the full two-week sample programme and the beginner/intermediate/advanced exercise progressions in the detail Greenfield originally presented.

Greenfield’s commercial relationships with multiple supplement and equipment manufacturers warrant a sceptical reading of specific product recommendations throughout Boundless. The “detox” protocols he sometimes includes (clay masks, coffee enemas, specific cleansing recommendations) aren’t evidence-based in the way the training protocols are; engage critically. The training programming itself is reasonably conservative and well-thought-out; the surrounding biohacker scaffolding is the part that benefits from filtering. With those caveats, here’s the programme.

The Boundless Two-Week Sample Programme

Week 1:

Cold Thermogenesis (throughout the week): A 5-minute showering protocol in a fasted state: 10 seconds of warm water followed by 20 seconds of cold water, 10 times through. In addition, choose one day for either a 10-minute ice-cold shower or 15-20 minutes of full-body cold-water immersion.

Day 1

• Foundation Training: Complete the exercises from Dr. Eric Goodman’s True to Form: How to Use Foundation Training for Sustained Pain Relief and Everyday Fitness. Go through each of the ten foundation exercises in the book once (10-15 minutes), focusing on perfect form.
• Tabata Sets: Perform a 10-15 minute warm-up, then complete 8 rounds of 20 seconds of a single exercise (burpees, jumping jacks, mountain climbers, kettlebell swings, squats, treadmill running, cycling, rowing) with 10 seconds of rest between rounds. Go at an all-out pace each round. Cool down with nasal breathing and easy aerobic movement for 5-10 minutes.

Day 2

• Morning Fasted Fat Burning: Before breakfast, perform 20-30 minutes of light cardio (yoga, fast walking, cycling, elliptical, swimming, hiking). The goal is to burn fat and lean up. Plain black coffee or tea before is fine; no calories until you’re done. If you can’t perform this cardio in the morning, do it after dinner and don’t eat afterwards.
• Swim Hypoxic Sets (optional): A 500-metre warm-up. Then 12 rounds of 25 metres each. During each round, don’t breathe or keep breathing to a minimum. Recover for 10 seconds, then repeat. Swim as smoothly as possible; don’t sprint. See what changes in technique conserve energy and oxygen.
• The 7-Minute Workout: Each exercise 30 seconds with 10 seconds rest between. One round takes about 7 minutes; if time allows, 2-3 rounds. Use good form on each exercise.
  • Jumping jacks
  • Wall sits
  • Push-ups
  • Crunches
  • Step-ups
  • Squats
  • Dips
  • Planks
  • Running in place with high knees
  • Lunges
  • Push-ups with rotation
  • Side planks

Day 3

• Metabolic Mobility (The Ultimate Foam Roller Routine): 20-30 passes with the foam roller on each step. Making one pass means going up the muscle group and back down.

1. 10 burpees. Foam-roll Achilles tendon and calf on right leg.
2. 10 burpees. Foam-roll Achilles tendon and calf on left leg.
3. Foam-roll right hamstring. 20 forward and backward high leg swings with right leg.
4. Foam-roll left hamstring. 20 forward and backward high leg swings with left leg.
5. 10 burpees. Foam-roll outside of right hip.
6. 10 burpees. Foam-roll outside of left hip.
7. Foam-roll IT band on right leg. 20 side-to-side leg swings with right leg.
8. Foam-roll IT band on left leg. 20 side-to-side leg swings with left leg.
9. 10 burpees. Foam-roll adductors on right leg.
10. 10 burpees. Foam-roll adductors on left leg.
11. 50 jumping jacks. Foam-roll back from bottom to top.
12. 50 jumping jacks. Foam-roll entire right shoulder complex.
13. 50 jumping jacks. Foam-roll entire left shoulder complex.
14. 10 burpees. Foam-roll neck (back, left side, right side).
15. 10 burpees. Foam-roll front of both quads.

Day 3

• Tabata Sets: As Day 1.

Day 4

• Morning Fasted Fat Burning: As Day 2.
• Super-Slow Routine: (Greenfield references the super-slow strength session covered earlier in Boundless; we cover the same protocol in Training Specificity and Testing.)

Day 5

• Tabata Sets: As Day 1.
• Sauna: 20-40 minutes (as long as you can tolerate) in a dry sauna. Focus on deep breathing, box breathing (4 count in, 4 hold, 4 out, 4 hold), occasional yoga moves, and stretches. Drink water in moderation. Finish with a cold shower.

Day 6

• Morning Fasted Fat Burning: As Day 2.
• Mitochondrial and Metabolic Sprints: All-out maximum-intensity sprint on a rowing machine, bike, or elliptical (or kettlebell swings, lunge jumps, squat jumps as substitutes) for 4 rounds of 30 seconds with 4 minutes of active rest. Finish with five 4-second all-out sprints with 20 seconds rest between.

Day 7

• Deep Breathing & Yoga: Deep, nasal belly breathing during a morning yoga routine, ideally 45-60 minutes. Try to do this in sunshine to amplify vitamin D levels. Focus on breath. No power or calorie-blasting yoga.
• Morning Fasted Fat Burning: As Day 2.
• Hot-Cold Contrast: Alternate between a 5-minute cold shower, cold soak, or easy cold-water swim (water must be 55°F / 13°C or less) and a 10-minute dry sauna or wet sauna session. Cycle for as long as possible, ideally 30-45 minutes (2-3 cycles).

Week 2:

Cold Thermogenesis (throughout the week): The 5-minute showering protocol as Week 1.

Day 1

• Tabata Sets: As Week 1 Day 1.
• Foundation Training: As Week 1 Day 1.

Day 2

• The 7-Minute Workout: As Week 1 Day 2.
• Morning Fasted Fat Burning: As Week 1 Day 2.
• Swim Hypoxic Sets (optional): As Week 1 Day 2.

Day 3

• Tabata Sets: As Week 1 Day 1.
• Metabolic Mobility: As Week 1 Day 3.

Day 4

• Super-Slow Routine: As Week 1 Day 4.
• Morning Fasted Fat Burning: As Week 1 Day 2.

Day 5

• Tabata Sets: As Week 1 Day 1.
• Sauna: As Week 1 Day 5.
• Foundation Training: As Week 1 Day 1.

Day 6

• 4-Minute HIIT with 4-Minute Rest for VO2 Max: Five rounds of intense 4-minute intervals at maximum sustainable pace. 4-minute easy active-recovery period between rounds. Run, bike, swim, elliptical, or row.
• Morning Fasted Fat Burning: As Week 1 Day 2.

Day 7

• Hot-Cold Contrast: As Week 1 Day 7.
• Morning Fasted Fat Burning: As Week 1 Day 2.
• Deep Breathing and Yoga: As Week 1 Day 7.

The Boundless Exercise Program (Beginner/Intermediate/Advanced Progressions)

The beginner programme gives maximum results with the minimum effective dose. The intermediate programme adds elements for sports performance, mobility, fat loss, and muscle maintenance. The advanced programme is for athletes preparing for serious events.

Complex Exercises

Upper Body Push:

• Machine chest press
• Barbell or dumbbell bench press
• Incline barbell or dumbbell bench press
• Standing overhead press
• Standing cable press
• Loaded push-up with weighted vest, or super-slow push-up with body weight

Upper Body Pull:

• Machine pull-down
• Bent barbell or dumbbell row
• Weighted or super-slow pull-up
• Weighted or super-slow horizontal pull-up
• Fast single-arm cable or dumbbell row
• Lat pull-downs
• Seated row

Full Body Moves:

• Man Maker
• Turkish get-up
• Bear complex (power clean, front squat, push press, back squat, second push press)
• Dead lift to overhead press
• Overhead squat

Lower Body Push:

• Leg press
• Barbell squat
• Goblet squat
• Front squat
• Single-leg squat
• Front lunge
• Reverse lunge
• Barbell or dumbbell step-ups

Lower Body Pull:

• Back extension machine
• Dead lift
• Suitcase dead lift
• Romanian dead lift
• Hexbar dead lift

Mobility:

• Torso twists
• Cat/cow
• Birddogs (opposite arm-leg extensions)
• Yoga Sun Salutation series
• Banded side-to-side walks
• Mountain climbers
• Foam rolling
• Bridging
• Banded side-walks
• Lunging mobility exercises

Power Exercises

Upper Body Push:

• Overhead push press
• Explosive or clap push-up
• Medicine ball chest throw or overhead throw
• Snatch
• Burpees

Upper Body Pull:

• Jumping pull-up
• Explosive horizontal pull-up
• Battle rope
• Fast single-arm cable or dumbbell row
• Muscle-ups

Lower Body Push:

• Jump squat
• Lunge jumps
• Explosive step-ups

Lower Body Pull:

• Power clean
• Hang clean
• Clean and jerk
• Kettlebell swing
• Medicine ball slam

Core/Carry/ Move

• Lunge jumps
• Box jumps
• Fast farmer’s walk
• Sled push
• Explosive stair climbs
• Explosive torso twists
• Medicine ball side throw
• Rowing machine
• Bicycle
• Treadmill or other sprint
• Banded side-to-side walks
• Mountain climbers
• Burpees
• Muscle-ups

Daily Habits

15 minutes of Morning Movement:

• Beginner: Walk for 15 minutes, preferably in sunshine.
• Intermediate: 15 minutes of yoga warrior poses and sun salutations, ELDOA stretches, foam rolling and deep tissue work, sunshine walks with deep nasal breathing and box breathing, mini-trampoline rebounding or vibration platform, or Foundation Training (Goodman’s True to Form).
• Advanced: Any intermediate routine, plus 20-30 minutes of fasted aerobic cardio later in the morning. Preferably finish with a 2-5 minute cold shower.

Low-Level Physical Activity Throughout the Day:

• Beginner: If you work indoors, use a standing or treadmill workstation. Walk and use stairs as much as possible.
• Intermediate: Beginner protocol, but stop every hour for 100 jumping jacks.
• Advanced: Continue beginner and intermediate, but throughout the day every 30-60 minutes, take quick Pomodoro-style breaks for burpees, kettlebell swings, jumping jacks, high-knees running, stairs, mountain climbers, or 1-2 minute bursts of any explosive activity. On three days of the week, slip away for a single Tabata set.

In addition, practice hypoxia during any of the day’s activities. For example, during rebounding, hold your breath for the first 15 seconds of every minute. During sauna or yoga, breath holds during certain movements. During the last few reps of a resistance exercise, breath holds. Otherwise, attempt to breathe through the nose using abdominal belly breathing for every activity, unless gasping or lightheaded.

Weekly Programming

Monday

Super-Slow Strength:

This is performed in late afternoon or early evening, at least 3 hours prior to bedtime.

• Beginner: Warm up with 5-10 minutes of aerobic exercise. Complete each exercise very slowly, with an 8-10 second count up and 8-10 second count down. Keep muscles tight and tense for each rep; don’t rest between reps. Complete a single round of the entire circuit. Each exercise: machine chest press, machine pull-down, machine shoulder press, machine seated row, leg press. Each set is a single set to complete failure, taking minimum 90 seconds and ideally 2-2½ minutes.
• Intermediate: Warm up with 1-2 sets of 3-6 fast explosive reps for each exercise. Finish each super-slow set with as many fast explosive partial-range reps as possible.
• Advanced: Warm up 5-10 minutes, preferably with gymnastics, Animal Flow, or Foundation Training. Choose one upper-body push, one lower-body push, one upper-body pull, one lower-body pull, and one full-body move from the Strength categories above. Pair each with one core/mobility movement. Complete 3-5 sets of each strength move paired with the core/mobility move, with the same alternating pattern. Cool down with deep breathing, box breathing, sauna, or walking.

Hot and Cold Thermogenesis:

• Beginner: Hot-cold contrast shower morning and/or evening (20 seconds cold, 10 seconds hot, repeated).
• Intermediate: Hot-cold contrast shower plus 15-30 minutes in dry or infrared sauna, then 2-5 minute cold shower or soak.
• Advanced: Exercise in the sauna if possible (Foundation, mobility, meditation in heat). Combine with detox strategies. Optionally use Cool Fat Burner / Cool Gut Buster gear for 20-60 minutes, or lie in the sauna for a 60-minute holotropic breathwork routine.

Tuesday

Functional Fitness:

Performed late afternoon or early evening.

• Beginner: The 7-minute workout from the section above. If time allows, 2-3 rounds.
• Intermediate: 2-3 rounds of the 7-minute workout. If possible, use blood flow restriction or Kaatsu bands. Start or finish with a mitochondrial training set: 4 rounds of 30-60 seconds all-out, followed by 4 minutes active recovery. Use cycling, treadmill, elliptical, rowing.
• Advanced: Intermediate routine, plus 3-5 rounds of full-body kettlebell training: 5 Turkish get-ups per side, 30 swings split into 3 sets of 10, 5 goblet squats, 30 snatches per side split into 3 sets of 10, 5 bottoms-up presses per side, 60 seconds of walking with two kettlebells racked or held farmer’s style. Use hypoxia during the hard cardio (Training Mask or LiveO2 if available).

Wednesday

Morning Detox Session:

• Beginner: 5-15 minutes of tai chi shaking, rebounding on mini-trampoline, or vibration platform work.
• Intermediate: Clay mask. While drying, 5-15 minutes of rebounding or vibration platform. Rinse off, then 20-30 minutes in sauna with full-body dry skin brushing and yoga movements. Finish with 2-5 minute cold shower. Apply topical magnesium or take a magnesium salt bath later.
• Advanced: Clay mask. Coffee enema (this is Greenfield’s recommendation; we flag this with the honest caveat that coffee enemas are part of Greenfield’s broader “detox” framing rather than an evidence-anchored intervention). Rinse off mask, then sauna as intermediate. Finish with cold shower/soak.

Cross Train:

• All levels: Free day for a hobby of your choice that challenges brain and body. If sore, try easy paddle boarding, new yoga class, hiking on a new trail, frisbee golf, golf. For more challenge: tennis, basketball, ultimate frisbee, soccer, kickboxing, jujitsu.

If you want a structured workout instead, do the Functional Movement / Animal Flow routine: bodyweight and functional movements including crawling, carrying, lunging, hanging, traversing, swimming. 30-60 minutes total. Examples:

1. Riding a bike to a river or lake to swim
2. Bodyweight or functional CrossFit WOD like “Fat Amy”
3. Brisk walking on nature trail with stops at park benches for dips, push-ups, squats, hanging from tree branches, pull-ups
4. Circuit: 20m farmer walk, 10m bear crawl, 60-second asymmetrical carry (swap sides at 30 seconds), 10m frogger, single-hand overhead walk (swap at 10m), 10m duck. Repeat 5 rounds.

Brain Training:

• All levels: Choose any new skill or hobby, or a new technique for an existing skill. Cook a new recipe. Play a new board or card game. Learn a musical instrument. Create a watercolour or oil painting. Anything on your bucket list. You can also use brain aerobics exercises.

Thursday

Hot and Cold Thermogenesis:

• All levels: 10-30 minutes in dry, steam, or infrared sauna. Stay long enough to begin sweating, preferably long enough to be uncomfortably hot. Combine with Foundation Training, mobility, meditation, yoga, or brief workout if you want to save time. Finish with 2-5 minute cold shower or soak.

VO2 Max Training:

• Beginner: 4 rounds of 4 minutes intense intervals at maximum sustainable pace (with form intact), with 4 minutes easy aerobic active-recovery between rounds. Bike, treadmill, rowing, swimming, elliptical, or running outdoors.
• Intermediate: Beginner workout, but first 2 rounds wear a Training Mask during work efforts; next 2 rounds wear during recovery efforts.
• Advanced: Intermediate workout, or use a LiveO2 trainer set at hyperoxia for first 2 work rounds and hypoxia for recovery rounds, then reverse for next 2 rounds.

Friday

Super-Slow Strength: Repeat Monday’s routine.

Saturday

Foam Roller or Massage:

• Beginner: 30-90 minute full-body massage.
• Intermediate: 30-90 minute full-body massage, ideally on a PEMF or earthing device (Biomat, BodyBalance PEMF mat, Pulse Center’s Pulse XL Pro table) while listening to Michael Tyrell’s sound healing tracks.
• Advanced: Same intermediate massage, or do the full-body foam-roller workout described in the Metabolic Mobility section above. RumbleRoller and Training Mask spice things up. Bonus points for doing this in a dry or infrared sauna.

Adventure of Choice:

• All levels: Choose your own adventure, preferably outdoors. Hiking, skiing, snowboarding, road cycling, mountain biking, obstacle course. Not too epic in physical intensity. Use for nature therapy, brain challenge, novelty. 45 minutes to 3 hours. For added fat-burning effect, perform fasted.

Sunday

Social Sport:

• All levels: Any sport or activity that allows you to be with other people. Badminton, volleyball, tennis, frisbee golf, golf, group exercise class.

Brain Training:

• All levels: As Wednesday’s Brain Training.

Hot and Cold Thermogenesis:

• Beginner: Hot-cold contrast shower (20 seconds cold, 10 seconds hot, repeating).
• Intermediate: As Monday’s intermediate routine.
• Advanced: As Monday’s advanced routine, including the holotropic breathwork option if available.

The Boundless programme is dense, well-structured, and represents Greenfield’s full synthesis of contemporary practitioner thinking on health optimisation. The substantial caveat is that it’s calibrated for a person with substantial time, resources, and access to gear (sauna, infrared sauna, foam roller, kettlebells, training mask, LiveO2, PEMF mats, etc.). The principles can be extracted and applied with much less equipment; the full programme as written is for the dedicated practitioner with the budget to match.

For most adults, the simpler longevity programme in The Longevity Program (2-3 resistance sessions per week, 1-2 high-intensity sessions, easy aerobic activity most days, daily mobility, occasional sauna and cold exposure) captures the substantial majority of the benefit at a fraction of the time and equipment commitment. The Boundless programme is what’s available if you want to push further.

Future Topics for Development

• Movement as the ultimate art form: Art is the subjective and often abstract expression of experience. How we move communicates our lifelong experiences. Every step tells the viewer about your fitness, trauma, relationships, and confidence. The intersection of dance, athletics, and self-expression is a category of human movement that conventional fitness culture has largely abandoned.
• Mobility work as a discipline of its own: Mobility is a substantial field with its own practitioner traditions (Kelly Starrett’s Becoming a Supple Leopard, Jill Miller’s Yoga Tune Up, Ido Portal’s movement culture, the gymnastics body-flow tradition).
• Stretching variations: Banded, static, active, passive, isometric, dynamic, ballistic, PNF, loaded progressive, Active Isolated Stretching. Each has distinct neural and mechanical effects. The deeper taxonomic treatment of each.
• Martial arts:
  • Qigong for intention to movement and proprioception. The “carrying a plate” example, where you maintain equilibrium of an invisible plate while taking your body through extreme ranges of motion (facilitating healthy joint and fascial function).
  • Wing Chun for energy efficiency. Producing dull high-impact force without muscular tension.
  • Jiu Jitsu for training the body to maintain strength through a full range of motion, understanding biomechanics and levers of the body, while challenging yourself with unpredictable movement.
  • Striking arts (boxing, kickboxing, MMA, Muay Thai) for generating extreme force via improved bodily coordination and reflexes.
• Extreme examples: Wim Hof, David Goggins, Iron Cowboy, James Lawrence, ultra-endurance athletes pushing the digestive ceiling. The trade-offs they accept and what we can learn vs what we can’t usefully replicate.
• Top performers: The recurring patterns in elite athletes across disciplines: childhood activity, genetic gifts, environment, deliberate practice, sleep, nutrition, recovery, and the role of luck.
• Drug-assisted training: Anabolic steroids, peptides, and SARMs produce substantial muscle-building effects with substantial health trade-offs. The “if you want results, you have to do this” framing in some fitness communities reflects that pharmaceutical interventions produce results natural training simply doesn’t replicate. The cardiovascular risk, hormonal disruption (often persistent after discontinuation), psychiatric effects, and the difference between using grey-market sources without medical oversight versus working with knowledgeable medical professionals. Growth hormone and IGF-1 modulators with similar trade-offs. TRT is increasingly common in middle-aged men (and now surprisingly common in teenagers); legitimate medical use for confirmed clinical hypogonadism vs off-label performance use is contested territory. Long-term consequences include partial dependency.

Specific Research Topics

External research links preserved as starting points for individual essays.

Cardiovascular and longevity:

• Running and lower all-cause mortality: foundmyfitness.com/news/stories/vmfvpg
• The human heart is built to deal with regular bouts of moderate intensity endurance: foundmyfitness.com/news/stories/ksyios

Cognitive and brain effects:

• Cardio for gray matter: newsnetwork.mayoclinic.org/discussion/keep-exercising-new-study-finds-its-good-for-your-brains-gray-matter
• Protecting aging synapses: sciencedaily.com/releases/2022/01/220107100955.htm
• Aerobic exercise linked to enhanced brain function: sciencedaily.com/releases/2020/02/200203104450.htm
• High and low intensity exercise influences the brain differently: iospress.com/news/high-and-low-exercise-intensity-found-to-influence-brain-function-differently

Exercise and disease:

• Exercise for those with multimorbidities: inverse.com/mind-body/exercise-as-therapy-unexpectedly-benefits-this-group-of-people
• Exercise can reduce muscle loss during low-calorie diets via autophagy: mdpi.com/2072-6643/11/11/2824
• Gut microbiome determines exercise efficacy for diabetes: cell.com/cell-metabolism/fulltext/S1550-4131(19)30608-4

Timing and nutrition:

• Time-restricted eating increases motivation to exercise: foundmyfitness.com/news/stories/wzhrd4
• Exercising before breakfast better for fat loss, insulin sensitivity, and glucose uptake: foundmyfitness.com/news/stories/iqj2fy

Strength and hypertrophy:

• Henneman’s size principle: en.wikipedia.org/wiki/Henneman%27s_size_principle
• Chinese weightlifting techniques: chineseweightlifting.com/olympic-weightlifting-training-exercises

Stretching:

• Types of stretching reference: sportydoctor.com/types-of-stretching

A Note on Sources

The notes above draw from multiple researchers and practitioners. The substantial Huberman Lab content was developed from Andrew Huberman’s Huberman Lab podcast and Neural Network Newsletter; Huberman is a Stanford ophthalmology and neuroscience researcher as well as a popular communicator, with his framing grounded in solid neuroscience, even when specific protocols sometimes outrun the underlying research. H. Craig Heller’s lab at Stanford is the primary research source for the AVA and palmar cooling work. Andy Galpin at Cal State Fullerton is the primary source for the hydration equation and the integrated endurance taxonomy. Duncan French at the UFC Performance Institute is the primary source for the strength-and-power-for-combat content. Ben Greenfield’s Boundless is the source for the programming detail in the Boundless section, with the honest commercial relationship caveats applied.

The major peer-reviewed primary research bases (Henneman, Tabata, Gibala, Schoenfeld, Phillips, Pontzer, Seiler, Maffetone, San Millán, Tarnopolsky, Werner, Loenneke, and others covered through the main pages of this section) provide the underlying primary research anchor.

Where popularisers contributed accessible synthesis, they’re credited where they appear. Where their specific claims outrun the evidence, that’s flagged. The full citation network for the main pages lives on the Resources page.