Fitness enthusiasts are crazy about running, but the evidence shows it’s too strenuous for almost everyone. Experts should walk back the running recommendation, says former marathon runner and ancestral health leader Mark Sisson
The romanticized notion that humans are “born to run” has buoyed the running boom of the past 50 years. Well-intentioned fitness enthusiasts lace up their cushioned shoes and plod down roads and trails in pursuit of the runner’s high, a trim physique and the fountain of youth.
Unfortunately, the idea that we’re born to run is a big, fat ruse—a marketing gimmick and a gross misappropriation of evolutionary biology. While any movement away from a sedentary lifestyle is laudable, the truth is that humans are born to walk, not to run.
Fitness enthusiasts may remember the bestselling book Born to Run, by Christopher McDougall (Profile Books, 2009). It romanticized the endurance exploits of the primitive-living Tarahumara peoples of Mexico, the elite Western ultrarunners who traveled there to compete and the proven insights about Homo sapiens’ many genetic endurance attributes. The book was credited with providing another boost to the decades-long running boom and the popularity of minimalist, barefoot-style running shoes.
It’s true that humans possess numerous highly evolved genetic attributes that enable them to perform feats of endurance superior to those of any other animal on earth. Our upright stature, long limbs, narrow pelvis and slender frames, in contrast to the physiognomy of our ape cousins, allow incredibly graceful bipedal locomotion.
We have efficient thermoregulatory mechanisms that adapt to prolonged exercise in the heat. Our springlike ligaments and tendons in the toes, arches, Achilles tendons and calves are designed for optimal impact absorption and the use of kinetic energy for forward propulsion.
Unlike our ape cousins, we possess a large and powerful gluteus maximus that is designed particularly for running. We have short toes, which greatly improve the mechanical efficiency of the foot in comparison to other animals’ longer toes. We even have a nuchal ligament, which connects the base of the skull to the spine and prevents excessive head bobbing while running.
In fact, the fittest humans can outlast cheetahs and antelopes and even fare well against horses, especially when temperatures are warm or hot. The documentary The Great Dance: A Hunter’s Story (Earthrise Productions, 2000) captures a persistence hunt—humans’ most ancient and elementary form of hunting—on film for the first time.
In the film, San hunters in the 110 degree Kalahari Desert track a kudu antelope for four hours, driving it to its ultimate demise by exhaustion. The endurance running hypothesis advanced by many evolutionary anthropologists asserts that persistence hunting is a key reason humans ascended to the top of the food chain. Contrast our graceful locomotion with that of the plodding, waddling, easily overheated great apes for further evidence of our evolutionary endurance superiority.
These scientific insights, combined with a hefty dose of modern fitness-industry marketing hype, have led us to celebrate the idea that humans are natural runners—that training for marathons is one of our birthrights. For the past half century, we have laced up our cushioned shoes and headed off down roads and trails searching for the promises of the runner’s high, a trim physique and protection against the diseases caused by a sedentary lifestyle.
We’ve been buoyed by culture-shaping ad campaigns from Nike (before the epic “Just do it” campaign launched, in 1988, Nike fueled the running boom with 1977’s “There is no finish line”) and dreamy quotations from scientific experts, elite athletes and journalists alike.
But the truth is as simple as this: Endurance running—anything beyond a mile or two—is too physically stressful for most enthusiasts. Attempting a 5k or 10k run (never mind a marathon), even at a modest jog, will cause most people to quickly transition from burning predominantly fat to burning predominantly glucose.1
This results in a stressful, exhausting, depleting workout. It’s not an effective way to become fit or healthy. The idea is supported by the embarrassing rate at which recreational runners are injured.
Numerous studies from all over the world suggest around half of all regular runners are injured every year.2 Even Runner’s World magazine, the go-to community resource for training and lifestyle guidance, admits 46 percent of its readers are injured annually.3 One study reports 25 percent of all runners are sidelined by injury at any given time.4
The reality is that most runners (except highly conditioned and genetically gifted front-of-the-pack athletes) lack the baseline metabolic, musculoskeletal and cardiovascular health to attempt an activity as strenuous as running. Mind you, this is not about training for marathons or ultras, simply about trying to run nonstop for as little as 10–15 minutes.
After only a few minutes of running, your heart rate can easily drift outside the comfortable aerobic zone, prompting increased stress-hormone production, elevated glucose burning, lingering muscular soreness and fatigue, and prolonged recovery time. A pattern of too-strenuous workouts can lead to exhaustion, depletion, brain fog, difficulty dropping excess body fat and an assortment of genetically programmed survival compensations that will make you generally less active in daily life.
And yet these workouts are the default recommendation of most popular books, magazine articles, coaches, personal trainers, expert-guided group running programs and fitness-minded peers.
By studying evolutionary biology, we understand that humans are genetically hardwired to engage in near constant low-level movement throughout the day, because this promotes optimal cognitive, hormonal, metabolic and immune function. It’s how our ancestors lived for 2.5 million years—hunting, gathering, foraging, wandering, scouting and migrating all day, every day.
Because of the disastrous unintended consequences of running and the tremendous upside of a walking-centric lifestyle, I hereby declare an end to the running boom. Humans are born to walk, not run.
I will stand my ground against any evolutionary biologist who refutes this contention. It’s clear that Homo sapiens has the genetic capability to perform amazing endurance-running feats driven by the fight-or-flight instinct, but that doesn’t mean those feats should be a norm.
Furthermore, as we marvel at our genetic capacity for endurance, we must also acknowledge that nearly all modern humans have completely squandered these gifts in the incessant pursuit of convenience and luxury. Raise your hand if you’ve tracked any antelopes for hours in hundred-degree temperatures recently, and you may be excused from class to go train for your next half-marathon.
Otherwise, let’s reflect on the fact that our amazing locomotive talents have been buried under collective tons of excess body fat; weak and atrophied musculature and connective tissue; diminished aerobic capacity (use it or lose it!); dysfunctional feet resulting from a lifetime of wearing elevated, restrictive shoes; and distracted, hyperconnected brains primed for sedentary instant gratification.
We’ve also been lured into running by profit-seeking marketing forces glamorizing ridiculously unhealthy events like the marathon as the ultimate endurance running achievement (Note: I was an elite marathon runner for many years, so I get to throw a little shade here). It might be instructive to realize the 26.2 mile event is based on a fabrication, not a glorious ancient running achievement.
Most runners are familiar with the story of Pheidipiddes, a Greek foot messenger (hemorodromus) who is the inspiration for the marathon distance today. As the legend goes, Pheidippides ran 26 miles from the city of Marathon, Greece, site of the historic battle of Marathon, to the assembled leaders in the capital, Athens.
He arrived to announce victory in battle (Nike! Nike! Nenekiam!, “Rejoice, we conquer!”) and then dropped dead. The marathon race, which was first presented in the modern Olympic Games in 1896, was contemplated for modern athletes to honor his heroic feat.
One problem: The story is a complete fabrication originating from an 1879 poem by Robert Browning, who took poetic license with Greek history. Pheidippides was indeed a historical figure and military hero. The hemorodromoi were able to travel faster than horses over rugged terrain and communicate key military strategy.
But the historical truth is that Pheidippes ran 153 miles in 36 hours, traveling from Athens to Sparta to request the Spartans’ help in the important battle of Marathon. Upon learning they were on holiday and couldn’t help right away, he quickly returned to Athens to convey the important news—running a superhuman 306 miles in four days.5
If we really want to honor Pheidippides, marathons should be 153 miles, not 26.2. If the marathon distance is truly random and whimsical, might the running community be better off—fitter, healthier and happier—if the “marathon” were 13.1 miles?
If you want to have a long, enjoyable, sustainable fitness journey, let’s back away from the hype and formulate a plan to do things correctly. Endurance exercise is not inherently unhealthy; it’s only unhealthy when you do it in an overly stressful manner.
A simple way to avoid this is to conduct the vast majority of your cardiovascular exercise at comfortable “aerobic” heart rates that emphasize fat burning, minimize glucose burning, are minimally stressful, and leave you refreshed and energized instead of slightly or significantly exhausted, depleted and craving a quick pint of Ben & Jerry’s afterward.
These are workouts conducted at or below your “fat max” heart rate—the point at which you burn the maximum number of fat calories per minute. When you speed up beyond fat max, you of course burn more total calories per minute, but you start burning less fat in favor of a spike in glucose burning.
This makes the workout more stressful and more difficult to recover from. A pattern of workouts that are slightly to significantly too strenuous to emphasize fat burning leads to breakdown, burnout, illness and injury. On the other hand, when you honor your fat max heart rate during endurance sessions, you become more efficient at using fat for fuel, which is the essence of endurance competency.
It’s called the development of an aerobic conditioning base and is the single most important ingredient for success. Your aerobic base allows you to absorb and benefit from occasional faster workouts that prepare you for competition.
You can identify your fat max heart rate with sophisticated laboratory testing, or you can use the widely recommended “180 minus age” formula developed by endurance coaching pioneer Dr Phil Maffetone. Simply subtract your age from 180 to identify your fat max heart rate in beats per minute.
For example, a 40-year-old person will have a fat max of 140 beats per minute. It’s critical to carefully monitor your heart rate during all workouts to ensure you remain below fat max and achieve the desired benefits of an aerobic workout.
What’s shocking to many exercisers is how comfortable fat max pace feels. It’s well below the exertion level at which people feel like they’re “getting a workout.” Instead, exercising at fat max feels extremely comfortable, like you can carry on indefinitely with no breathing or muscle discomfort.
While a heart rate monitor is best, you can also roughly estimate fat max pace with the so-called “talk test” or monitoring your nasal breathing. If you can easily converse without getting winded while exercising, you’re likely at or below fat max. If you can close your mouth and breathe through your nose only without having to open it and gasp for air, this also suggests you’re at or below fat max.
And now for the kicker: Most runners, even experienced runners, are doing most of their training mildly to significantly above fat max. Again, they’re not feeling immediate strain and pain from drifting above fat max, but over time they’re training the wrong energy systems for endurance and raising the risk of overtraining. The heart rate monitor doesn’t lie, so it follows that slowing down to a walk will help many runners properly develop the aerobic system.
It’s known in exercise physiology that the human gait pattern typically switches from a jog to a walk at a pace of 14 minutes per mile. Hence, if you can’t go faster than that without exceeding fat max, your training pace becomes a walk or perhaps a blend of walking and jogging for the desired duration of the workout.
Carefully regulating training pace according to heart rate, and needing to slow from a jog to a walk accordingly, is not as immediately gratifying as taking off down the road or the trail for a vigorous workout after a stressful day in the confines of the office. But it is scientifically validated as the correct way to train the body into a fine-tuned endurance machine—instead of a tired, fat, frequently injured, sugar-burning, sugar-chomping machine. This is a harsh characterization, but it’s an accurate description of the physiological state of most recreational runners.
In contrast, we can reference the training habits of the world’s greatest endurance athletes in every sport for the past 60 years—all of whom spend the vast majority of their training time in comfortably paced aerobic heart rate zones and add impressive high-intensity training sessions only as icing on the cake.6 Even these sessions, which many recreational runners try to integrate in the name of getting “faster,” are beneficial only because the elites have done the hard work to absorb and benefit from them.
If you care about your physical health, including your immune, metabolic and hormonal function, and about making sure your training efforts support longevity rather than compromise it, you will be well served to slow down and patiently build that aerobic base. This applies even if your ultimate goal is only to get faster, and even if it entails trading in your slightly too stressful typical jogging pace for brisk walking or alternate jogging and walking.
The most egregious broken promise of the running boom is also the most obvious: Endurance running does not help you lose excess body fat. It’s likely that the most common goal of recreational joggers is to drop excess body fat, but their workouts are too strenuous and exhausting to be effective in that way.
Yes, you burn calories logging the miles, but a pattern of workouts that are slightly to significantly too stressful prompts an increase in appetite, especially for quick-energy carbs, which you deplete during sugar-burning workouts.
Endurance running also leads to a reduction in general everyday movement and resting metabolic rate. Perhaps most important, it prompts your hormones to signal the body that it needs to shed lean muscle mass and hoard body fat.
These observations led scientists to develop the compensation theory of exercise. In essence, when you push your body too hard with exhausting, depleting workouts, it engages in an assortment of hardwired compensations to conserve energy—to preserve stored body fat and signal the body to become consciously and subconsciously lazy in everyday life.
Dr Herman Pontzer, author of the books Burn (Allen Lane, 2021) and Adaptable (Avery, 2025) and one of the world’s leading experts on energy expenditure by humans and other primates, explains that “reproduction, repair, growth, and locomotion are a zero sum game.” We have an upper limit on our daily caloric expenditure, so if excess energy is devoted to endurance training, the body will turn down other important dials in a genetically programmed response to conserve energy.
Just as too much exercise stress can cause a tear in the biceps or a stress fracture in the tibia, an overtrained heart can sustain serious and irreversible damage. Scientific research reveals that serious heart conditions are occurring with shocking regularity among longtime competitive marathoners, ultramarathoners, triathletes, racing cyclists, long-distance cyclists and cross-country ski racers. Medical experts are now referring to these heart troubles as runner’s cardiomyopathy and Pheidippides cardiomyopathy.
Engaging in chronic cardio for years and decades can prompt an assortment of pathological structural and electrical changes to a healthy heart:
That’s right: This is the same high blood pressure and hardening of the arteries that you think you’re running away from with your devotion to endurance training. Alas, if you keep running long enough and keep pushing the pace, you may complete a loop that lands you on a couch next to your lazy, junk-food-eating next-door neighbor.
A study of longtime marathon runners—those who finished a minimum of 25 marathons over the previous 25 years—showed an average calcified plaque volume, also known as a coronary artery calcium (CAC) score or Agatston score, of 274. In the sedentary control group, the average score was 169.1
For reference, a CAC score over 300 indicates a very high risk of heart disease. A score of 100 suggests an elevated risk, below 50 is considered safe, and zero is a great score—clean pipes from clean living and sensible fitness pursuits.
The right ventricle is particularly vulnerable to damage from chronic cardio because it typically pumps against the low-resistance lungs and is far less muscular than the left ventricle. When the delicate right ventricle is repeatedly stretched and scarred from overuse, it can no longer contract efficiently—like a worn rubber band.
While a scarred hamstring is a bummer for your fitness goals, scarred heart tissue can disrupt the electrical impulses that flow through it and cause arrhythmias. Endurance athletes are particularly susceptible to atrial fibrillation as well as premature ventricular contractions, atrial flutter, ventricular fibrillation, ventricular tachycardia, atrial tachycardia and hypertrophic cardiomyopathy.
In the worst cases, athletes experience sudden cardiac death during exercise, even when their blood work and routine screenings such as EKGs show no evidence of atherosclerosis or other risk factors. Many athletic types have gone in for routine screenings to discover significant blockages of the major arteries despite their impressive fitness credentials.
Jogging 2.0
Instead of a humdrum steady-state session, you can make jogging the baseline form of locomotion for the workout, but sprinkle in brief periods of medium-to-high-intensity running technique drills, dynamic stretches, jumping drills, balance and agility drills, or core- or leg-strengthening movements. Visit the Peluva YouTube channel (youtube.com/@wearpeluva) for instructional videos of basic, intermediate and advanced running technique drills, such as the popular “skipping” drills and many variations performed by track and field athletes.
Skipping drills emphasize certain segments of the running stride to help reinforce correct technique or exaggerate range of motion to improve your mobility and force production. Most of them are low-impact and easy to learn, even for those without racing experience.
Walkabouts
Instead of staying on the beaten trail or path, do some off-roading to purposely negotiate rough, varied and/or uneven terrain. Even the most urban-dense pedestrian trails offer opportunities for brief detours onto varied terrain. The idea here is to purposely challenge your proprioception (awareness of the body’s position in space) and foot functionality by walking on a rock bed or natural debris, up or down steep slopes, diagonally across a steep incline, or any other variation you can find in your environment.
Even if you’re confined to an urban setting not intended for fitness or adventure, you can find ways to sprinkle in variation. For example, try walking a few strides with one foot on the sidewalk and another at street level before returning to a level surface. Hop onto a bus bench, jump back down and resume your walk. Grab a sign pole and do a set of single-leg Romanian deadlifts with each leg before resuming your walk.
Walk-jog fat max workout
Instead of pegging your heart rate at fat max for the duration of your aerobic workouts, consider starting at your typical jogging pace, then slowing to a walk when your heart rate reaches fat max. After a few minutes of walking, your heart rate should drop significantly and you can break into a jog once again. Then repeat the cycle, always slowing when your heart rate reaches fat max.
Uphill backward walking
Weighted backward uphill (or backward on an incline treadmill) walking delivers an excellent strengthening effect to the arches, calves, quads and glutes in a way that forward walking doesn’t. The quads in particular get loaded much more than when walking forward. This exercise is also great for improving balance and proprioception.
It’s important to use minimalist shoes (or just socks on a treadmill) to get full muscle activation without interference from landing on an elevated-heel shoe. I typically walk for three to five minutes, take a short break for forward walking and then repeat for a few sets.
Adapted from Born to Walk by Mark Sisson and Brad Kearns (Primal Blueprint Publishing, 2025). Former endurance athlete Mark Sisson is a pioneer of the Primal/Paleo lifestyle and is known for his best-selling books and top-ranked health blog
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