High performance has a recurring temptation: to believe that if we collect enough data, we will finally find the textbook athlete. The right body, the right training, the right diet, and the predicted response.
Herman Pontzer's Adaptable begins exactly where that fantasy ends. The book tours the human body to show that the average human is a useful abstraction. Genes, development, environment, culture, and chance leave their mark on all of us. We share the same architecture, yet no organism matches the textbook illustration in every detail.
This is not a book about athletic preparation. That may be why it made me think so deeply about it.
Biology gives us shared principles and individual responses. Our job is to know when to trust each level.
The average athlete is a starting point, not a person
Science and practice need averages. They show what tends to work, define reasonable doses, and protect us from decisions based on impressions. The problem begins when the average stops guiding us and starts replacing the person in front of us.
Two people can complete the same session and experience different internal costs. The same athlete may respond differently weeks later because sleep, intake, pain, accumulated load, travel, stress, or training status has changed. The exposure is identical on paper; the organism receiving it is not.
There is an equal and opposite trap: calling every fluctuation individuality. A single change can be measurement error, day-to-day variability, or behavior outside training. Reviews of trainability show that some of the apparent difference between “responders” and “non-responders” disappears when control groups, error, and meaningful change enter the analysis.
Individualization, therefore, does not mean abandoning collective knowledge. It means starting from a defensible baseline and earning the right to adjust it through reliable observations.
Genes change probabilities; they do not write the score
Pontzer presents human diversity as the result of genes, environment, and chance interacting. That frame is especially useful in sport.
Biological characteristics matter. Height, body proportions, development, cardiorespiratory capacity, muscle properties, and load tolerance may favor particular tasks. At the elite level, small advantages can matter because nearly everything else has already been selected and trained.
Even so, a genetic association found in a group cannot predict an individual's future. Performance is a highly polygenic, context-dependent phenotype. No single marker tells us the quality of training someone will receive, their opportunity to practice, how they will respond to a coach, which injuries they will avoid, or when an opening will appear.
The consensus on genetic testing in sport and newer analyses of variants such as ACTN3 do not support using them to select talent or prescribe training. DNA participates in the story; it does not hand us the script.
That changes the professional question. Instead of asking, “What is this athlete's true potential?” I prefer to ask: What capacities does the task demand, what resources does this athlete have now, and what does their response trajectory allow us to build?
How the ideas connect
Adapting does not mean improving in every direction
The chapter on muscle and bone is the book's most direct link to high performance. Muscle changes with use; the nervous system learns to recruit it; metabolism reorganizes its capacity; tissues become more tolerant of what they encounter progressively.
That plasticity, however, is specific and costly. A marathoner, sprinter, gymnast, and weightlifter are not better or worse versions of the same design. They are different solutions to different demands.
In high performance, this rules out the naive pursuit of maximizing everything at once. More mass may increase force production and raise locomotion cost. More volume may develop capacity and reduce availability for the next game. An intervention that favors chronic adaptation may temporarily worsen readiness; a strategy that restores readiness today may reduce part of the stimulus a block was meant to provide.
The criterion is never “more adapted” in the abstract. It is adapted for what, in which phase, at what cost, and for how long.
Practice is essential, but it does not govern alone
The book revisits the popular ten-thousand-hour rule and arrives at a more honest formulation: accumulated work is necessary, but it cannot explain excellence on its own.
A sports meta-analysis estimated that deliberate practice explained some of the variation in performance, and far less among athletes who had already reached the elite level. The exact figure depends on definitions and methods that remain debated, but the practical decision is stable: counting hours does not measure the quality of learning.
High-level training requires an appropriate task, feedback, progression, focus, correction, and time. It also requires access. Family, sporting culture, good coaches, infrastructure, calendar, biological maturity, and opportunity shape careers long before a genetic test could add any value.
Talent is not a substance hidden inside the athlete, waiting to be discovered. It is a trajectory that becomes visible through the relationship among predisposition, exposure, learning, and context.
Recovery is the adaptation budget
Another idea runs through the book: the organism allocates finite resources among growth, movement, immunity, reproduction, maintenance, and repair. For performance, that changes the language in an important way.
Training is not adaptation. Training is an exposure that may produce adaptation if the system has the time, energy, and substrates to reorganize.
When load rises and energy availability does not keep pace, the body must negotiate. The International Olympic Committee's consensus on Relative Energy Deficiency in Sport describes how problematic low energy availability can impair reproductive function, musculoskeletal health, immunity, glycogen synthesis, well-being, and performance.
This does not turn recovery into passivity. It turns recovery into allocation. Sleep, energy, carbohydrate, protein, load spacing, and stress management must serve the desired adaptation and the next demand.
An adaptable body can also hide the cost for a while. Stable body weight and completed training do not prove the budget is balanced.
From concept to decision
The environment enters the athlete
One of Adaptable's best contributions is dissolving the artificial boundary between biology and environment. The environment does not merely sit around the body as scenery. It participates in building the body.
In performance, environment includes surface, temperature, and altitude, but also staff language, role clarity, access to food, psychological safety, sleep quality while traveling, contractual pressure, and belonging. These factors can alter behavior, recovery, availability, and the capacity to learn.
A program should therefore be judged on more than the physiological coherence of its sessions. It must also be judged on the quality of the ecosystem that makes those sessions executable and adaptive.
Individualization means closing the loop
The operational translation of the book fits into four moves:
- Defensible baselineBegin with evidence, the sport's demands, and safety limits.
- Defined exposureKnow the dose applied, its timing, and the context surrounding it.
- Observed responseCombine performance, health, and availability while respecting measurement error and day-to-day variability.
- RecalibrationMaintain, progress, or replace the intervention according to the trajectory, not the anxiety created by an isolated data point.
This loop avoids two extremes. On one side is the universal protocol that ignores the person. On the other is ornamental personalization that creates complexity before showing the athlete needs it.
The caveat that makes the reading better
Adaptable is a wide-ranging work of popular science, not a systematic review or a training manual. Some passages in the sports chapter simplify physiology too far.
The idea that training should create as much muscle damage as possible to promote growth does not align well with the literature: hypertrophy can occur with minimal damage, while excessive damage can reduce the quality of subsequent sessions. The passage linking the ACE gene's I allele to sprinters and its D allele to endurance athletes also appears reversed relative to the cited reference, which describes I in association with endurance and D with power. Even those associations are heterogeneous and offer no useful individual prediction.
These corrections do not overturn the central thesis. They show how the book should be used: as an intellectual map of plasticity, limits, and human diversity—not as a prescription.
The central shift
What remained after the final page
High performance is often narrated as overcoming biology. After reading Adaptable, I think it is more precise to describe it as a skilled negotiation with biology.
The athlete is not infinitely malleable. They arrive with a history, an architecture, and limits. Nor are they condemned to their starting point. Tissues learn, the brain reorganizes, skills mature, and the environment can expand or waste possibilities.
The practitioner does not control that response. They organize the conditions for it to occur, measure what they can, acknowledge what they still do not know, and correct course.
Not promising to read the athlete's destiny, but building a system capable of learning from them.
Frequently asked questions
Does adaptability mean every athlete can reach the same level?
No. Plasticity enables change within limits influenced by biology, development, history, and context. It expands possibilities; it does not erase differences or guarantee the same competitive ceiling.
Should a program be fully individualized from day one?
Not necessarily. An evidence-based baseline is usually the best beginning. Individualization improves when adjustments respond to reliable measures, tolerance, adherence, and real demands.
Can genetic tests identify athletic talent?
The current body of evidence does not support using isolated markers to select athletes or define training. A population association is not an individual prediction.
Verified references
- Pontzer H. Adaptable: How Your Unique Body Really Works and Why Our Biology Unites Us. Avery; 2025. ISBN 9780593539309.
- Bonafiglia JT, Swinton PA, Ross R, et al. Interindividual Differences in Trainability and Moderators of Cardiorespiratory Fitness, Waist Circumference, and Body Mass Responses: A Large-Scale Individual Participant Data Meta-analysis. Sports Medicine. 2022;52(12):2837–2851. DOI: 10.1007/s40279-022-01725-9.
- Webborn N, Williams A, McNamee M, et al. Direct-to-consumer genetic testing for predicting sports performance and talent identification: Consensus statement. British Journal of Sports Medicine. 2015;49(23):1486–1491. DOI: 10.1136/bjsports-2015-095343.
- Godina E, Khromov-Borisov N, Bondareva E, et al. Prediction of success in sports based on assumed individual genetic predisposition: lack of association with the C>T variant in the ACTN3 gene. Journal of Physiological Anthropology. 2025. DOI: 10.1186/s40101-025-00386-7.
- Macnamara BN, Moreau D, Hambrick DZ. The Relationship Between Deliberate Practice and Performance in Sports: A Meta-Analysis. Perspectives on Psychological Science. 2016;11(3):333–350. DOI: 10.1177/1745691616635591.
- Mountjoy M, Ackerman KE, Bailey DM, et al. 2023 International Olympic Committee’s consensus statement on Relative Energy Deficiency in Sport (REDs). British Journal of Sports Medicine. 2023;57(17):1073–1098. DOI: 10.1136/bjsports-2023-106994.
- Mujika I, Halson S, Burke LM, Balagué G, Farrow D. An Integrated, Multifactorial Approach to Periodization for Optimal Performance in Individual and Team Sports. International Journal of Sports Physiology and Performance. 2018;13(5):538–561. DOI: 10.1123/ijspp.2018-0093.
- Damas F, Libardi CA, Ugrinowitsch C. The development of skeletal muscle hypertrophy through resistance training: the role of muscle damage and muscle protein synthesis. European Journal of Applied Physiology. 2018;118(3):485–500. DOI: 10.1007/s00421-017-3792-9.
- Jones A, Montgomery HE, Woods DR. Human Performance: A Role for the ACE Genotype? Exercise and Sport Sciences Reviews. 2002;30(4):184–190. DOI: 10.1097/00003677-200210000-00008.
Educational content. Training individualization does not replace clinical assessment, safety criteria, or contextual interpretation of the athlete's responses.