Exercise 101

What is Exercise and What is the Point of it?

There’s something a little strange about the fact that we have to convince ourselves to exercise.

For nearly every other animal on the planet, physical activity is the price of staying alive. A lion that doesn’t hunt starves. A gazelle that doesn’t run gets eaten. Activity was the cost of survival, not a deliberate choice, fit into your lunch break between periods of sitting. The idea that you’d voluntarily exhaust yourself when there’s no immediate threat or reward would strike most species as either pointless or suspicious.

Daniel Lieberman, the Harvard evolutionary biologist, has spent his career working out why humans are a partial exception to this rule. His framing in Exercised is worth sitting with for a moment: humans evolved to move when necessary (foraging, hunting, travelling, escaping danger, raising children, building shelter) and to rest when possible because energy was scarce and rest was protection. The hunter-gatherer doesn’t go for a jog after a day of foraging because going for a jog would be a metabolic crime against their own survival. The fact that we, in industrialised societies, now have to reenact ancestral activity patterns through structured exercise deliberately is the consequence of living in an environment our biology was never designed for. We solved the problem of activity being required for survival, and in doing so, we created a different problem.

This is the conceptual entry point for everything in this section. Movement is what your body expects. Exercise is the structured supplement we need because modern life has stripped movement out of daily existence. Once you understand that, the rest of this section becomes much easier to navigate.

Exercise itself is typically thought of as the process of putting our bodies under controlled physical stress, for the purpose of improving overall health, sculpting our bodies to be more appealing to ourselves or a potential love interest, and increasing our physical strength. Some of us love it, some of us hate it, and some of us desperately “need” to exercise to feel ourselves. What makes this component of our lives more appealing is the near-endless list of physical activities and hobbies that one can use to receive many of the benefits that regular exercise provides.

The Common Health Benefits of Regular Exercise

Each of these has substantial primary-research support:

• Lowered risk of premature death from all causes
• Lowered risk of coronary heart disease and stroke
• Lowered risk of hypertension
• Lowered risk of type 2 diabetes and metabolic syndrome
• Lowered risk of colon cancer, breast cancer, and several other cancers
• Improved condition of the cardiovascular and circulatory system
• Improved muscular fitness and bone density
• Prevention of weight gain (with caveats covered in Energy Systems)
• Prevention of falling and fall-related injury in older adults
• Prevention and treatment of depression
• Improved cognitive function across the lifespan

The Lancet’s Global Burden of Disease studies have repeatedly identified physical inactivity as one of the top five modifiable risk factors for premature death globally, with effect sizes comparable to smoking and obesity. When researchers in Denmark followed the Copenhagen City Heart Study cohort over decades, men and women who averaged at least 30 minutes of exercise per day cut their risk of dying in half compared with sedentary participants. A similar finding emerged from large prospective studies in Australia, the United States, and across Europe. Herman Pontzer’s analysis of these datasets in Burn notes that people who got an hour or more of moderate and vigorous activity each day were roughly 80% less likely to die in a given period than the most sedentary participants.

The dose-response question (how much do you actually need?) has been studied extensively. A reasonable synthesis: the largest gains come from going from zero to any regular activity, with diminishing returns thereafter. The Ekelund analysis in The Lancet (2016) pooled data from over a million participants and found that approximately 60 to 75 minutes of moderate-intensity physical activity per day was needed to eliminate the increased mortality risk associated with prolonged sitting. That’s a substantial dose, and most of the population isn’t anywhere near it.

Sedentary Life Is Its Own Problem

One finding worth flagging because it took the field some time to absorb: exercise doesn’t fully cancel out sitting. Two people can both meet the recommended 150 minutes of moderate activity per week. If one of them spends the rest of their waking hours seated and the other spends those hours walking, standing, gardening, and otherwise moving in low intensity, the second person has substantially better health outcomes.

The work of researchers like Marc Hamilton (formerly Pennington Biomedical, now University of Houston), Peter Katzmarzyk at Pennington, and James Levine at Mayo Clinic established sedentary behaviour as an independent risk factor for cardiovascular disease, type 2 diabetes, and all-cause mortality. Sitting for prolonged periods produces measurable changes in lipoprotein lipase activity, glucose handling, and skeletal muscle gene expression that don’t reverse with a daily gym session.

The gym session is useful, but it isn’t sufficient. The total daily activity profile shapes long-term health, and the modern office-job-plus-evening-workout pattern produces measurable physiological costs that the workout doesn’t fully address.

Bodies that move throughout the day in low-intensity patterns (walking, standing, light manual work, climbing stairs) are doing something different from bodies that sit for nine hours and then do an hour of high-intensity training. Both are useful. Neither replaces the other.

Cognitive Benefits of Exercise

• Exercise increases the volume of grey matter in the brain: Particularly in areas crucial for memory and executive function. The work of Kirk Erickson at the University of Pittsburgh, published in PNAS in 2011, was a landmark: a randomised trial of one year of moderate aerobic exercise in older adults produced a 2% increase in hippocampal volume, effectively reversing the typical 1-2% annual age-related decline. The control group, which did stretching, showed a continued decline. The Erickson group went on to demonstrate that the hippocampal changes correlated with improvements in spatial memory and were mediated in part by exercise-induced increases in brain-derived neurotrophic factor (BDNF).
• Exercise has emerged as one of the most reliable non-pharmaceutical treatments for depression: The SMILE trial, conducted by James Blumenthal’s group at Duke and published in Psychosomatic Medicine in 2007, found that aerobic exercise (3 x 45 minutes per week) was approximately as effective as sertraline (Zoloft) for treating major depressive disorder over 16 weeks, with substantially fewer side effects and better durability of effect at follow-up. Subsequent meta-analyses have generally supported this finding, with the caveat that the absolute effect sizes for both exercise and SSRIs in depression are more modest than the original framing implied. Exercise probably acts through multiple mechanisms (BDNF elevation, inflammation reduction, reward system normalisation, autonomic regulation, improved sleep), which is part of why the effect is robust across different depression subtypes.
• BDNF is one of the key molecular players: Brain-derived neurotrophic factor is a protein that supports neuron survival, growth, and synaptic plasticity. Aerobic exercise is one of the most powerful natural stimulants of BDNF expression. Carl Cotman at UC Irvine, working with rodents in the 1990s and 2000s, established the basic neurobiology: voluntary running upregulates BDNF in the hippocampus within days, the BDNF increase correlates with improved learning on standard tasks, and blocking BDNF blocks the cognitive benefits. High-intensity work produces larger BDNF spikes than moderate-intensity work, but the moderate work is more sustainable and produces larger long-term effects through cumulative stimulus.
• Long-term potentiation (LTP): the cellular basis of learning and memory, is enhanced by exercise. Henriette van Praag’s work at the Salk Institute and later at NIA demonstrated that wheel running in mice increased neurogenesis in the hippocampus and enhanced LTP in the dentate gyrus. The human applicability has been demonstrated indirectly through cognitive testing in trials like Erickson’s; we can’t easily measure LTP in living human brains, but the cognitive improvements that exercise produces are consistent with enhanced synaptic plasticity.
• The “runner’s high” mechanism has been substantially revised: For decades, the popular story credited beta-endorphins (the body’s natural opioids) for the euphoria some people experience during sustained aerobic exercise. Endorphins don’t cross the blood-brain barrier effectively, so peripheral endorphin elevations probably don’t produce central nervous system effects. The more current research, particularly from David Raichlen at the University of Arizona and University of Southern California, points to the endocannabinoid system (anandamide and related compounds) as the more likely mediator. Raichlen’s work demonstrated that anandamide levels rise substantially during moderate-intensity aerobic exercise in both humans and dogs (who run for similar evolutionary reasons), but not in ferrets (who don’t). The endocannabinoid pathway also explains why the runner’s high tends to emerge at moderate intensity and longer durations rather than during sprints. Anandamide takes time to accumulate.
• Strength training has its own cognitive effects: The Erickson group and others have shown that resistance training in older adults improves executive function and increases functional plasticity in the prefrontal cortex. The mechanism is less well-characterised than the aerobic-BDNF pathway, but probably involves growth factors (particularly IGF-1), improved cerebral blood flow, and metabolic effects on glucose handling.
• Exercise reduces the risk of neurodegenerative disease: Multiple large cohort studies have found that regular physical activity is associated with a 30-40% lower risk of Alzheimer’s disease and Parkinson’s disease. The mechanisms probably overlap with the general cognitive benefits (BDNF, neurogenesis, cerebral perfusion, glymphatic clearance during sleep) plus exercise-specific effects on amyloid clearance and alpha-synuclein handling that are still being worked out.
• For children, the case is particularly strong: The work of Charles Hillman at the University of Illinois and others has documented that aerobic fitness in children is associated with measurably larger hippocampal and basal ganglia volumes, improved attention and executive function, and better academic performance, particularly in mathematics and reading comprehension. The development of a child’s brain, nervous system, and cognitive function depends on regular and varied physical activity. The trend toward eliminating recess, physical education, and free play in favour of more classroom time has the empirical support of approximately no one in the developmental neuroscience field.

Exercise is one of the most reliable, lowest-cost, lowest-side-effect interventions for cognitive function across the lifespan that human medicine has ever identified. It works in children, in adults, in older adults, and probably in people with existing neurological conditions. The dose for cognitive benefit appears to be lower than the dose for cardiovascular benefit; even 20-30 minutes of brisk walking several times per week produces measurable cognitive effects in many studies.

Exercise Preference and Mental Resilience

Exercise preference is generally dependent on a person’s body type and their rate of recovery. Women typically take longer to recover from any given exercise stimulus, though the effect size is modest and substantially smaller than the variation within each sex. Age also slows recovery. Especially if your rate of movement has decreased over the years (use it or lose it). A person’s fitness level, training background, and the development of various physical characteristics will have a greater effect on recovery than gender or age alone.

If you’re struggling to decide what type of exercise you should participate in, it is often best to start with something your body is better suited for and that you actually enjoy doing. I know we fetishise the pain aspect of exercise and correlate that with progress, but the benefits of such are exaggerated. The ability to handle pain is excellent for building mental resilience and may push us past previously held beliefs about our physical limitations. In saying that, unless you are attempting to compete at the extreme end of some sort of sport or event, it is better to spend more time developing bodily awareness and improving your abilities instead of risking injury by training like a professional.

The “no pain, no gain” framing has done substantial damage in the fitness world. The actual research on training adaptation suggests that the optimal stimulus for most people is enough to drive adaptation but not so much that recovery and form suffer. The professional athlete model, where training is structured around an absolute willingness to break the body in pursuit of marginal gains, is exactly the wrong model for someone whose goal is to live longer and feel better. We’ll cover this in detail in Training Specificity and Testing.

Sex Differences in Exercise Physiology

The work of Stacy Sims (formerly Stanford, now AUT in New Zealand) has been the most influential in shifting the field’s approach to female exercise physiology. Her core argument, supported by a growing body of research, is that women are not small men, and training and nutrition recommendations derived primarily from male physiology don’t always transfer.

A few of the specific findings:

• Recovery times tend to be longer in women: Particularly during the high-hormone phase of the menstrual cycle (luteal phase)
• Carbohydrate utilisation patterns differ: Women rely on fat oxidation more during sustained exercise and may benefit from different fueling strategies than the standard recommendations
• Heat dissipation differs: Women tend to have lower sweat rates and may overheat more readily during high-intensity work in warm conditions
• Strength training response is robust: Women respond to resistance training with hypertrophy and strength gains that, when normalised to baseline muscle mass, are comparable to men
• Hormonal cycle effects on training: The “train with your cycle” framework has weak research support for most claims. Some training adaptations probably do interact with cycle phase, particularly recovery and high-intensity work tolerance
• Menopause produces substantial changes: The loss of estrogen affects bone density, muscle mass, recovery, and body composition in ways that warrant adjusted training approaches

The field is still catching up after decades of using male subjects as the default. Practical recommendations specific to female physiology are emerging, but not yet at the same evidence quality as the general training science. For most women, the basic principles (regular movement, adequate strength training, attention to recovery, fueling appropriately) still apply. The fine-tuning is where the sex-specific work becomes relevant.

Emotional and Social Benefits of Exercise

Regular exercise affects social behaviour. People who exercise regularly generally have healthier emotional lives and more confidence than those who lead a more sedentary life. Exercise has also been shown to improve the social skills of children. Exercising in a group invokes team spirit and may improve communication skills, depending on the type of activity and the quality of the group morale.

Even spectator sports have measurable physiological effects. Experiencing an intense sporting achievement with others, who are also supporting the same team or player, may strengthen social relationships between spectators. Those on the side of the winning team show measurable increases in both testosterone and oxytocin levels. This effect is greater for men than for women. As a side note, the increased levels of oxytocin that help men to bond have also been shown to make them more antagonistic to those who support the other team. Oxytocin is sometimes characterised in popular discourse as a “love hormone”, but its actual function is closer to “in-group cohesion hormone,” which involves out-group hostility as part of the same biological system.

The social dimensions of exercise are probably underrated in most popular discussions. Robert Sapolsky and others have argued that the health benefits of exercise are partly mediated by the social contexts in which exercise typically takes place (the running club, the basketball game, the yoga class, the hiking group). Disentangling the “exercise” effect from the “social connection while moving” effect is methodologically difficult, but a reasonable inference is that exercise in social contexts is meaningfully better than exercise in isolation for most people. We cover the social biology more directly in Connection (forthcoming).

Rethinking Exercise

I’m sure there are no arguments from the other side of the computer screen so far, right? We’ve heard it all before. The problem that most of us tend to have with committing to a continuous exercise plan is the motivation to start and keep moving. We’ll often use excuses like “I don’t know what I’m doing,” or “I can’t afford a gym membership,” and even “I don’t have the time.” Occasionally, we’ll lie to ourselves about our activity levels and overall well-being, so we may protect our egos and avoid the pressure of change (common in those who are under considerable mental stress). Resulting in procrastination and the inevitable physical health decline of the individual.

Now, I don’t blame those who are “too busy” or “too tired” for refusing to take advantage of what I consider to be one of the greatest panaceas available. What I do believe to be one of the major causes of our current sedentary pandemic is the public perception of what the purpose of exercise actually is. One of the many consequences of living in a society that rewards individualism is the packaging of exercise for financial gain and the distorted motivational drivers that have been associated with exercise, in order to increase that financial gain. In other words, we’ve forgotten that movement is a fundamental process tied into the very fabric of our identity, and have begun to treat it as a pathway to climbing the social hierarchy.

What does exercise have to do with the social hierarchy?

Alright, bear with me for this one. Seeing as we have so recently dissolved our societal model of tribal living, which took millions of years to evolve, suddenly we have all these unfulfilled emotional attachment needs as a result of being convinced that the individual’s pursuit of happiness was superior to the collective needs of said “tribes.” By taking advantage of one of our most basic measures of sexual selection, physical fitness, we’ve been conditioned to believe that we need to spend excessive amounts of time and money to artificially develop sexually appealing bodies (using photoshopped, rich, and famous individuals as unrealistic targets), to attract a mate. While it is true that one of the first measures of sexual selection is physical fitness, we’ve taken this desperate desire for love a little too far.

I’ll be the first to admit that obsessive physical activity is certainly one of the better addictions to have. Motivating ourselves to achieve greatness by using high performers as an example results in producing some of the most inspiring sports stars of our time. However, the belief that we need a purpose for activity, or that there is no point in performing exercise unless we can be the best, appears to have detached us from the necessity of movement. When we view exercise as a route to obtaining the fitness or bodies of those at the extreme ends of the human physical spectrum, we are less likely to appreciate movement as an opportunity to understand our bodies on a personal level. Which brings us to the real issue with using weight loss stories, athletes, and models as inspiration: when our results don’t match our overinflated expectations, our motivation plummets dramatically. Either that, or we push ourselves to work out and diet at an unsustainable and longevity-declining rate. If we can’t post our “inspiring” weight loss results on social media to improve our peers’ opinions of us, what’s the point of going through all that pain?

What’s the solution?

I suggest that we undergo a momentary perspective reframe of exercise. A rebranding of sorts. The benefits of exercise are due to an evolutionarily adaptive response to our expected physical requirements. A consequence of living and exploring the wild, not purely as the result of fighting to become the best caveman bodybuilder or athlete in the tribe. Seeing as we no longer live the same lifestyle or inhabit the same type of environment that we once evolved for, we need to keep in mind that our bodies still expect movement stimuli and will decline in functionality if deprived of them. Use it or lose it.

Exercise should once again return to being a form of exploration and play. I view the way we move as the ultimate demonstration of self-expression. Your body and its subsequent movements subtly communicate to those around you who you are, your lifetime of experience, and the purity of your intentions. This doesn’t mean we need to demonise the pursuit of vanity and performance-based training. It just means we should reassess our motivations and goals for pursuing these endeavours when they begin to feel like they are no longer serving us. As a consequence, I hope this would lead to less bodily shame and obsession for both the high performers and those who feel defeated before they even start. Resulting in movement becoming as essential as eating, drinking, or breathing, which would lead to our global health outcomes improving dramatically.

What Counts as Movement

If movement (not exercise) is the requirement, what does that look like in modern life?

The research community has converged on a useful concept here: NEAT, or Non-Exercise Activity Thermogenesis, coined by James Levine at Mayo Clinic in the early 2000s. NEAT captures everything that isn’t sleeping, eating, or formal exercise: walking, standing, fidgeting, climbing stairs, gardening, cooking, cleaning, playing with kids, carrying groceries. Levine’s work demonstrated that variation in NEAT can account for 2,000+ calories per day of energy expenditure difference between sedentary and active people, vastly exceeding what most exercise sessions contribute.

The Hadza data from Pontzer’s group is informative here, too. The Hadza, a hunter-gatherer population in Tanzania, average roughly 100-150 minutes per day of moderate-to-vigorous activity (mostly walking, foraging, and digging), with substantial additional low-intensity movement throughout the day. The total daily activity profile is dramatically different from that of a typical office worker who might log 90 minutes of moderate-to-vigorous activity per week. The Hadza don’t “exercise.” They move because their lives require it.

For modern people, the practical translation looks something like this:

• Walking as the foundation: The most consistently health-protective form of human movement across populations and historical periods is walking. A reasonable daily target for most adults is 7,000-10,000 steps per day, though the dose-response curve doesn’t flatten at 10,000 steps. Even 4,000-7,000 steps daily provides substantial mortality risk reduction compared to truly sedentary lifestyles, particularly in older adults. Walking is metabolically cheap, low-injury-risk, and integrates easily into daily life.
• Standing and movement breaks during sedentary work: The evidence on standing desks is mixed; standing all day produces its own problems. The better-supported approach is breaking up sitting with regular movement: 2-5 minutes of walking or light movement every 30-60 minutes of sitting produces measurable cardiometabolic benefits.
• Climbing stairs: A simple, high-leverage form of low-grade resistance and cardiovascular work. Several large cohort studies have found stair-climbing volume to be independently associated with reduced cardiovascular mortality.
• Carrying things: Loaded carrying (the “farmer’s carry” framing) is one of the most ancestrally relevant movements available to modern humans. Carrying groceries, kids, water, firewood, or weighted bags trains grip strength (one of the strongest mortality predictors in the medical literature), core stability, and metabolic conditioning simultaneously.
• Manual work and chores: Gardening, cleaning, cooking, and basic home maintenance involve squatting, bending, reaching, pushing, and pulling in patterns that gym training doesn’t replicate. The substantial decline in manual home labour across industrialised societies is part of the broader movement-stripping that modern life produces.
• Outdoor activity: The combination of movement plus sunlight (covered in Sleep & Circadian Rhythm) plus nature exposure (covered in Environment when we get there) produces additive effects beyond what any of the components produce alone.

A person who walks substantially, takes the stairs, carries their own groceries, plays with their kids, gardens on weekends, and breaks up sitting with regular movement is doing more for their long-term health than a person who does a single hard gym session in an otherwise sedentary day. Both can be true at once: structured exercise has benefits that a sedentary lifestyle can’t replicate, and structured exercise can’t fully replace a lifestyle with movement woven through it.

How Do We Start Moving?

As explained in the Biohacker’s Handbook, “Exercise should be thought of as natural, playful movement that takes place during the day, without forced performances, grimacing, and exhaustion.”

For someone starting from a sedentary baseline, beginning your exercise journey can be as simple as going for a walk at the park with friends or joining a sports or martial arts club. If you prefer to exercise by yourself, that’s totally fine, but you will be more likely to keep participating if good company is present.

The first thing I would advise is to start walking 20-30 minutes per day with friends. This serves the purpose of improving lymphatic flow, muscular and vascular tone, mental health and cognitive function, strengthening the heart and lungs, filling your social quota, and providing you with adequate sun exposure. The next step would be to try a new hobby, such as yoga, martial arts, surfing, swimming, callisthenics, rock climbing, etc. It doesn’t need to be as intense as these options, but choosing an activity that meets as many needs as possible will have a greater effect on your overall health and well-being. If you find an activity you absolutely love and want to take further, go for it. Just don’t lose sight of why you started doing it in the first place. Otherwise, the obsession with that exercise may result in a greater stress load and end up creating a deficit in your well-being status.

The Minimum Effective Dose

For someone who wants the simplest possible answer to “what’s the floor,” the synthesis from a substantial body of research looks roughly like this:

For cardiovascular and mortality benefits:

• 150 minutes per week of moderate-intensity activity (brisk walking, easy cycling, gardening) OR
• 75 minutes per week of vigorous activity (running, swimming, sport, HIIT) OR
• A combination of the two

For muscle and bone preservation, particularly with age:

• Resistance training 2 times per week, hitting all major muscle groups
• This need not be gym-based: bodyweight, resistance bands, kettlebells, or carrying loads all qualify

For cognitive function and mood:

• 20-30 minutes of moderate aerobic activity most days
• Generally consistent with the cardiovascular dose, both can be met with the same training

For longevity specifically:

• Add VO2 max work (high-intensity intervals) once or twice per week, as covered in detail in The Longevity Program

Most adults aren’t currently meeting it. The good news is that the marginal benefit of going from zero to meeting this floor is dramatically larger than going from meeting it to exceeding it. Get to the floor first; optimise afterwards.

The Biohacker Manifesto for Exercise

The Biohacker’s Handbook closes its exercise section with a manifesto that captures the framework’s general position as well as any short formulation could:

• Life is movement, movement is medicine
• Exercise in a regular and varied manner
• Train equally in strength, speed, agility, balance, and endurance
• Increase everyday incidental exercise
• Utilise your body weight
• Exercise outdoors whenever possible
• Quality over quantity
• Exercise in good company
• Maintain the balance between exercise and rest
• Never stop playing

The pages that follow get into specifics. Energy Systems covers how your body produces and stores energy for movement and the metabolic constraints that shape training. Training Specificity and Testing covers how to measure your current physical capacity across the different domains (endurance, strength, power, mobility, balance) and how to train each. The Longevity Program covers training specifically for a long, capable, disease-resistant life.

If you only take one thing from this page, take this: movement is non-negotiable, exercise is supplemental, and the floor is much lower than the fitness industry tells you. Walk every day, lift heavy things twice a week, play hard sometimes, sleep well, eat well, and the substantial majority of what exercise can do for you will be available to you.