“Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding” by Daniel Lieberman presents a thought-provoking analysis of the role of exercise in our contemporary, industrialised society. As an acclaimed evolutionary biologist, Lieberman challenges conventional perspectives by suggesting that humans did not evolve to exercise in the manner we do today. Rather than viewing physical activity as a pursuit for health and fitness, Lieberman posits that our ancestors primarily engaged in movement for survival purposes. In our modern world, where the treadmill has become a symbol of our complex relationship with physical exertion, Lieberman’s “Exercised” prompts us to reconsider the very concept of exercise itself.
Imagine attempting to explain to our ancestors the idea of sweating profusely on a machine just to remain stationary—it would undoubtedly seem absurd. However, Lieberman delves deeper, contending that the evolutionary history of humans does not align with the contemporary notion of exercise.This book has significantly impacted my personal approach to exercise. As someone who previously viewed physical activity as a burdensome task confined to the walls of a gym, Lieberman’s work introduced a transformative perspective. It encouraged me to integrate movement into my daily life by embracing enjoyable activities and bypassing some of the conveniences afforded by modernity. Furthermore, it emphasised the importance of physical activity in combating lifestyle diseases.
The core advice distilled from Lieberman’s insights is refreshingly concise: make exercise both necessary and enjoyable. Opt for activities that incorporate cardiovascular exercise and resistance training, recognising that any level of activity is beneficial. Consistency and gradual progression are key, particularly as one ages.
In our fast-paced lives, many individuals may struggle to find time to delve into an entire book. However, I hope this summary serves as a gateway to understanding the profound effects of exercise on the body and its role in promoting overall well-being. Importantly, it underscores that exercise does not necessitate a visit to the gym; rather, by embracing the lifestyle of our ancestors and integrating movement into daily routines, we can cultivate vibrant health well into our later years.
MYTH #1 We Evolved to Exercise
In the pursuit of understanding our relationship with physical activity, a prevailing notion, rooted in the concept of the “natural human,” has long captured imaginations. But as we delve deeper into this idea, we uncover a complex interplay between evolution, lifestyle, and the myths surrounding the athleticism of certain indigenous groups. Let’s unravel the layers of this myth and explore what truly defines “normal” physical activity for humans.
The Myth of the Athletic Savage: The theory of the natural human, championed by philosopher Jean-Jacques Rousseau, posits that individuals untouched by civilisation embody our true selves. This notion, though debunked, persists in various forms, including the belief in the athletic savage. This myth suggests that people like the Tarahumara tribes, renowned for their long-distance running prowess, effortlessly achieve remarkable feats due to their untainted lifestyles.
However, a closer look reveals a different reality. The Tarahumara, like the Hadza of Tanzania, engage in daily physical labour integral to their existence. Far from idle, they walk miles, perform manual tasks, and hunt or gather food regularly. Their endurance stems not from inherent athleticism but from a lifestyle steeped in physical activity.
Understanding Indigenous Lifestyles: Observations of the Hadza reveal a balance between light activities and periods of rest. While their daily routines differ from modern sedentary lifestyles, they do not engage in constant strenuous activity. Similarly, the Tarahumara’s ability to run long distances without formal training is a result of their everyday physical exertion, not genetic predisposition.
Reevaluating “Normal” Physical Activity: Comparing the physical activity levels (PALs) of hunter-gatherers to postindustrial individuals sheds light on what constitutes “normal” activity. While hunter-gatherers exhibit PALs comparable to those of factory workers and farmers in developed countries, they fall short of the activity levels seen in wild mammals. This challenges the notion of inherent athleticism and highlights the influence of lifestyle on physical activity patterns.
Debunking the myth of the athletic savage reveals the nuanced relationship between human evolution and physical activity. Rather than innate athleticism, lifestyle factors heavily influence our capacity for endurance and fitness. By redefining “normal” physical activity within the context of evolutionary biology and cultural practices, we gain a deeper understanding of our relationship with exercise and movement.
MYTH #2 It Is Unnatural to Be Indolent (wanting to avoid activity)
Consider chimpanzees, our evolutionary kin. While traversing the forest floor might be a challenging feat to match, these primates spend the bulk of their waking hours either feeding or digesting. Their lifestyle involves leisurely pursuits: munching on fibrous foods, grooming one another, and indulging in long siestas. Despite occasional bursts of activity, chimpanzees epitomise a leisurely existence, akin to a perpetual Sabbath.
Contrastingly, hunter-gatherer tribes like the Hadza, though not engaged in strenuous labor, still outpace apes in activity levels, painting humans as energetic dynamos in comparison. This paradox raises intriguing questions about the evolutionary shift towards sedentarism in modern humans. To unravel this mystery, we delve into the intricate workings of our bodies and the energy we expend while at rest, a journey that demands scientific scrutiny.
The Dynamics of Energy Expenditure
Imagine yourself, an average 180-pound adult male in America. Even in a state of rest and inactivity, your body diligently burns approximately seventy calories per hour, constituting your resting metabolic rate (RMR). This metabolic baseline fuels the myriad chemical reactions sustaining your bodily functions. Over twenty-four sedentary hours, you’d effortlessly expend around 1,700 calories based on your RMR alone.
Further delving into energy dynamics reveals that your basal metabolic rate (BMR), roughly 10% lower than your RMR, reflects the energy required to maintain vital bodily functions in a dormant state. These metabolic nuances highlight a fundamental truth: regardless of physical exertion levels, the body continually expends energy to sustain itself, defying conventional wisdom.
Insights from Starvation Studies
The landmark Minnesota Starvation Experiment conducted from 1944 to 1945 sheds light on the body’s remarkable adaptability to prolonged dietary restriction. Volunteers, subjected to severe caloric deprivation, witnessed a staggering 40% reduction in both resting and basal metabolic rates over twenty-four weeks. This metabolic downshift, though imperceptible outwardly, underscores the body’s innate ability to economise energy even in dire circumstances.
During starvation, essential bodily functions undergo recalibration to conserve energy. Heart rates plummet, and body temperatures dip, manifesting as constant coldness – a testament to the body’s resourcefulness in times of scarcity. Such revelations challenge the notion of rest as mere physical inactivity, emphasising its role as an active process entailing substantial energy expenditure.
Navigating the Calorie Conundrum
In the intricate dance of energy allocation, understanding the finite nature of caloric expenditure is paramount. A calorie, a unit of energy, serves diverse functions – from bodily growth and maintenance during rest to storage as fat or fuelling physical exertion or reproduction. These allocations, dictated by age and environmental factors, underscore the body’s adaptive prowess in optimising energy utilisation for survival and reproductive success.
For our ancestors, prudent energy allocation was vital for survival. Engaging in essential activities like foraging and reproduction took precedence over discretionary physical exertion. Thus, while movement remains integral to human existence, moderation in energy expenditure ensures optimal resource allocation for life-sustaining endeavours.
Embracing the Wisdom of Rest
As you pause amidst your daily pursuits, grappling with feelings of guilt over perceived idleness, consider this: your stillness mirrors a time-honoured strategy for conserving precious energy. Contrary to societal narratives equating laziness with sloth, the inclination to preserve energy has deep evolutionary roots, transcending mere physical inactivity. Far from a moral failing, opting for rest reflects a primal instinct honed through millennia of adaptation.
In reframing laziness as a prudent energy-saving measure, we reclaim its essence from moral judgment, recognising it as a survival strategy ingrained in our evolutionary heritage. So, the next time you find yourself hesitating to engage in strenuous activity, remember: in the grand tapestry of human evolution, rest is not only natural but also indispensable.
MYTH #3 Sitting Is Intrinsically Unhealthy
In understanding the human body’s relationship with physical activity, one often comes across the notion that sitting is intrinsically unhealthy. However, delving deeper into this concept reveals a more nuanced perspective that challenges conventional wisdom.
Sitting, a universal human behavior, has evolved alongside our species as a means of conserving energy. From ancient hunter-gatherers to modern-day individuals, sitting for extended periods is a common practice deeply rooted in our history. While the average American may spend a significant portion of their day seated, this habit mirrors the sedentary tendencies observed in other animals, such as chimpanzees.
Contrary to popular belief, chimpanzees, our closest relatives in the animal kingdom, exhibit remarkably sedentary behaviour, with up to 87% of their day spent in activities like grooming, resting, and feeding. Even the most inactive humans surpass the activity levels of wild chimpanzees. This begs the question: if sedentary behaviour is natural for both humans and apes, why is sitting often demonised as unhealthy?
The purported health risks associated with prolonged sitting primarily revolve around three concerns: lack of physical activity, elevated levels of sugar and fat in the bloodstream, and potential immune system dysfunction leading to inflammation. However, studies challenge these assumptions, suggesting that the link between sitting and adverse health outcomes is more complex than initially thought.
For instance, extensive research, including a 15-year study of over 10,000 Danish individuals and a study of 66,000 Japanese office workers, found no direct correlation between sitting at work and heart disease. Instead, factors like socioeconomic status and leisure-time activities play a more significant role in predicting mortality. Similarly, the belief that sitting posture contributes to back pain lacks robust scientific evidence. Studies examining the relationship between sitting posture and back pain consistently fail to establish a causal link, emphasising the importance of factors like muscular strength and fatigue resistance in maintaining spinal health.
In essence, while prolonged sitting may raise concerns, the narrative surrounding its inherent danger warrants reconsideration. By acknowledging the evolutionary context of sedentary behavior and critically evaluating scientific evidence, we can adopt a more balanced perspective on the role of sitting in human health.
MYTH #4 You Need Eight Hours of Sleep Every Night
In today’s fast-paced world, we often fall into the trap of medicalising various aspects of our lives, prescribing specific doses of behaviours like physical activity, fibre intake, and yes, even sleep. The notion that we need a strict eight hours of sleep each night has become ingrained in our collective consciousness. But where did this recommendation originate, and is it truly applicable to everyone?
Let’s delve into the intricate world of sleep patterns to uncover the truth behind this pervasive myth.
Dispelling the Myth: Firstly, it’s essential to recognise that sleep patterns vary widely among different species, and even among individuals within the same species. Take, for example, the striking differences between donkeys, who sleep for a mere two hours a day, and armadillos, who can slumber for up to twenty hours. Some animals, like giraffes, take frequent naps, while others, like whales, have evolved unique sleep adaptations to function effectively underwater.
Insights from Anthropology: Anthropological studies shed light on the diversity of sleep patterns among human populations. Research by anthropologist David Samson among Hadza hunter-gatherers revealed a wide range of sleep activity, suggesting that the notion of a standard eight-hour sleep cycle is far from universal. Similarly, studies conducted among forager-farmers from various regions show that these populations typically sleep less than industrialized societies, yet exhibit remarkable alertness and functionality during waking hours.
The Evolutionary Perspective: Contrary to popular belief, the disorderly sleeping conditions of our ancestors may have served an adaptive purpose. Anthropologist Carol Worthman suggests that the gradual transition into sleep, marked by a decrease in environmental awareness, may have functioned as a protective mechanism in an environment fraught with potential dangers. By attuning to subtle cues of safety, our ancestors could enter deeper stages of sleep with greater security.
Understanding the Sleeping System: Our sleep-wake cycle is governed by two main biological processes: the circadian rhythm and the homeostatic system. The circadian rhythm, regulated by the hypothalamus, dictates our sleep-wake cycle in response to environmental cues like light. Meanwhile, the homeostatic system builds sleep pressure based on the duration of wakefulness, ensuring a balance between time spent awake and asleep.
Challenging the Sleep-Industrial Complex: In recent years, the proliferation of the sleep industry has capitalised on society’s concerns about sleep quality, inundating consumers with an array of high-tech gadgets and pharmaceutical solutions. However, the overreliance on sleeping pills and other quick fixes overlooks the complex interplay of biological and environmental factors that influence sleep.
The myth of the eight-hour sleep cycle serves as a reminder of the dangers of oversimplification in matters of health and wellness. While acknowledging the importance of quality sleep, we must resist the temptation to adhere rigidly to arbitrary standards. Instead, we should embrace the rich diversity of sleep patterns observed across cultures and species, informed by insights from anthropology, evolutionary biology, and neuroscience.
By reframing our understanding of sleep through a multidisciplinary lens, we can foster a more nuanced dialogue about sleep health and well-being in the modern world.
MYTH #5 Normal Humans Trade Off Speed for Endurance
Why are humans relatively slow compared to many animals?
Humans, despite the impressive speed of athletes like Usain Bolt, lag behind many quadrupeds such as zebras, giraffes, wildebeests, white-tailed deer, and even wild goats in terms of speed. Even slower predators like grizzly bears and hyenas could easily surpass human sprinters like Bolt. The primary reason behind this is the limitation of sprinting, which relies on quick bursts of energy. Even the fastest animals cannot maintain top speed for long durations, and humans are no exception. For example, elite sprinters like Bolt can maintain maximum velocity for about twenty seconds only before they slow down significantly. Similarly, cheetahs, known for their incredible speed, can only sustain peak velocity for around thirty seconds before fatigue sets in. In contrast, many other mammals can run much faster than humans and can sustain their pace for longer periods.
The mechanics of bipedalism, or walking on two legs, contribute to humans’ relatively slow running speed. Unlike animals with four legs, such as dogs and chimpanzees, humans generate power for movement solely from their legs against the ground. This means less power and, consequently, less speed. While quadrupeds can push off the ground with four legs, humans have only two, limiting their running speed to half that of similar-sized quadrupeds. This disadvantage arises from the fact that only one leg is on the ground at any given moment to propel the body forward. Essentially, having two legs is the primary reason why humans are relatively slow runners.
How do our muscles replenish energy during exercise?
Muscles replenish energy through various processes that occur over time. Initially, energy comes almost instantaneously from stored ATP (adenosine triphosphate) and creatine phosphate (CrP). As these stored energy sources get used up, energy is provided rapidly from glycolysis, a process that breaks down sugar. However, as exercise continues, glycolysis becomes insufficient to meet energy demands, and the body turns to aerobic metabolism, a slower but steady process that occurs in the mitochondria of cells.
The Phosphagen system, the first process of muscle energy regeneration, is the quickest but short-lived method of providing energy. At the onset of exercise, muscles rely on the small amount of ATP and creatine phosphate available. Creatine phosphate, similar to ATP, stores energy and quickly replenishes ATP stores. However, these reserves are limited and depleted within seconds of intense activity.
Glycolysis, the second process, involves the breakdown of sugar to produce energy rapidly. This process does not require oxygen and generates ATP to fuel high-intensity activities like sprinting. However, glycolysis produces lactic acid as a byproduct, leading to muscle fatigue and discomfort.
The aerobic system, the third and final process, provides long-term energy through the breakdown of sugar or fatty acids in the presence of oxygen. While aerobic metabolism yields significantly more ATP compared to glycolysis, it takes longer to produce energy. This process is essential for sustained activities like long-distance running.
Can one possess both speed and endurance?
The common belief that exceptional athletic abilities are either speed-oriented or endurance-focused may not accurately reflect human potential. While professional athletes often excel in specific domains, such as sprinting or marathon running, the general population may not face the same limitations.
Elite marathoners and sprinters represent extremes in athletic performance, with distinct skill sets tailored to their respective disciplines. However, their exceptional abilities may not apply to the average individual. For example, elite marathoners can maintain a pace of 4:40 per mile for an entire marathon, showcasing both speed and endurance. This demonstrates that it is possible to possess both qualities without compromising one for the other.
While most people may not reach the levels of elite athletes, individuals can develop a balance of speed and endurance through training and practice. By focusing on improving cardiovascular fitness, muscular strength, and technique, individuals can enhance both their speed and endurance capabilities. Thus, while the majority may not compete at the highest levels, they can still achieve a harmonious blend of speed and endurance in their athletic pursuits.
The Power of HIIT:
Our bodies are capable of learning various activities, including both speedy bursts and long-lasting endurance. Training for both aspects can be highly effective. Even if you prefer endurance exercises over high-speed ones, research suggests that engaging in regular sessions of high-intensity interval training (HIIT) can significantly enhance not only strength and speed but also overall fitness and health. HIIT involves alternating short bursts of intense anaerobic exercise, like sprinting, with less intense recovery periods. It’s important to note that HIIT isn’t weight training but a vigorous form of cardio. To delve deeper into how HIIT can boost sprinting speed without compromising endurance, let’s explore further.
Let’s begin with plyometric exercises, also known as jumping training drills. A typical plyometric routine might include around ten vigorous skips, where you jump as high and fast as possible on one leg at a time, while raising the opposite knee and both arms.
Upon landing, your hip, knee, and ankle joints flex, stretching your leg muscles and making it challenging for them to contract explosively. This rapid jumping fatigues your fast-twitch muscle fibers. Following this, perform an equal number of butt kicks. Finally, try sprinting repeatedly for a hundred or two hundred meters as fast as you can, demanding rapid and forceful muscle contractions while depleting ATP and phosphate stores. These HIIT workouts are intense and may lead to muscle soreness for a few days.
While HIIT cannot increase the number of fast-twitch muscle fibres, it can make existing ones thicker, resulting in enhanced strength and speed. Indeed, sprinters typically have muscles that are over 20 percent thicker than those of distance runners. HIIT can also transform slower, fatigue-resistant pink fibres into more fatigable white fibres, as well as elongate fibres, improving their contraction speed, and increase the percentage of muscle fibres that contract, thereby boosting force.
However, these adaptations don’t occur automatically and necessitate continuous effort to maintain. If you aim to enhance your speed, you must consistently strive to run faster.
MYTH #6 We Evolved to Be Extremely Strong
Primal Strength: CrossFit enthusiasts believe that their training taps into an ancient tradition of overall physical prowess necessary for survival. Essentially, they argue that being strong is a fundamental aspect of human nature.
However, it’s essential to question whether the intense workouts of CrossFit truly mirror the physical activities of our ancestors. Unlike modern fitness routines, our early human predecessors didn’t engage in structured exercise solely for health purposes. So, were they really as strong as we think? Or would the demanding workouts of CrossFit seem as alien to them as contemporary tasks like handling taxes or reading?
While there’s limited data on the strength of hunter-gatherer men and women, what we do have suggests that they were generally lean and moderately strong but not bulky. Specifically, tropical hunter-gatherers tend to be more slender than muscular. For instance, Hadza men average around five feet four inches and 117 pounds, while Hadza women average about four feet eleven inches and 103 pounds. Their body fat percentages hover around 10 percent in men and 20 percent in women, just skirting the line of being underweight.
Studies on the Hadza tribe’s grip strength, upper-body strength, and muscle size show that they fall within Western norms for their age, but below those of highly trained athletes. The Hadza aren’t known for their muscular physique, but they are physically fit and possess the strength needed for their daily activities, which include tasks like digging, running, and climbing trees. It’s important to note that while the Hadza represent one population, their physical attributes are similar to other hunter-gatherer groups such as the San of the Kalahari, the Mbuti of central Africa, the Batek of Malaysia, and the Aché of Paraguay.
Although hunter-gatherers engage in occasional heavy lifting, most of their muscle resistance comes from activities like carrying, digging, and lifting their own body weight. They rely on equipment-free, body-weight-based exercises such as push-ups, pull-ups, squats, and lunges to build strength. However, there’s a downside to these exercises: as you get stronger, the resistance remains constant because you’re lifting your own body weight. Unlike modern gym-goers who can adjust weights, hunter-gatherers lack access to such tools for achieving a highly muscular physique.
MYTH #7 Sports = Exercise
Are humans stronger than chimps?
Scientists from the U.S. Air Force designed a unique device resembling a blend of a metal enclosure and an electric chair to gauge the force generated by humans and chimpanzees when bending their elbows. Among the adult chimps trained to utilize this apparatus, only one could manage it, and it was discovered to be roughly 30 percent stronger than the strongest human tested.
More recently, researchers from Belgium revealed that bonobos weighing seventy-five pounds can leap twice as high as humans weighing twice as much, indicating that both species can jump to the same height per pound.
Additionally, a lab analysis of muscle fibers indicated that a chimpanzee’s muscles can produce a maximum of 30 percent more force and power than those of an average human. Although these studies differ in their methodologies, they collectively suggest that adult chimpanzees are not more than a third stronger than humans. Therefore, contrary to popular belief, a chimp wouldn’t be able to dislocate your arm in an arm-wrestling match. However, it’s still probable that you would lose.
Ageing and Muscles: As we age, our muscle fibres tend to shrink in size and number, and our nerves deteriorate. This leads to a decline in strength and power. In developed countries like the United States and the U.K., grip strength typically diminishes by about 25 percent from the age of twenty-five to seventy-five.
In Framingham, Massachusetts, near the author’s residence, the percentage of women incapable of lifting ten pounds has been observed to rise from 40 percent among fifty-five- to sixty-four-year-olds to 65 percent among seventy-five- to eighty-four-year-olds. This trend is concerning because as individuals lose strength, they become less capable of performing basic tasks such as rising from a chair, climbing stairs, and walking normally. This frailty also leads to decreased physical activity, creating a vicious cycle of deterioration.
However, elderly hunter-gatherers and others who maintain physical activity throughout their lives demonstrate the encouraging news that using our muscles can slow down muscle loss as we age. In fact, ageing doesn’t prevent our muscles from responding to resistance exercise. Even moderate levels of resistance exercise can slow down and sometimes reverse sarcopenia, regardless of age, thanks to previously discussed mechanisms.
Violent and Peaceful: We’ve been taught to recognise humanity’s tendencies and capacities for violence but to believe that humans evolved to be predominantly moral, peaceful, and cooperative. We should be satisfied with being mostly nonviolent humans rather than apes because, if we were chimpanzees, a significant portion of our day would be spent trying to avoid being attacked or killed. Only humans are willing to risk their lives by rushing into a burning building to save the life of an unrelated individual or a pet. Even aggressive sports like cage fighting are regulated by rules and referees to limit the harm participants can inflict on each other. In this respect, we collectively lean towards the beliefs of Jean-Jacques Rousseau and his supporters, who argue that behaving morally is our natural inclination and that many instances of human violence result from corrupt cultural attitudes and circumstances.
However, violence is ingrained in every culture, including hunter-gatherer societies, which challenges the assumption that we are inherently gentle and non-aggressive. Therefore, I also recognize the contributions of Thomas Hobbes and his followers, who view human tendencies toward aggression as ancient, inherent, and sometimes advantageous.
The question remains: how can we reconcile our remarkable abilities for cooperation and conflict prevention (Rousseau) with our potential for aggression (Hobbes)?
Richard Wrangham offers a compelling resolution to this longstanding debate by emphasizing the critical difference between two fundamentally distinct types of aggression: proactive and reactive. According to Wrangham, humans exhibit substantially lower levels of reactive aggression than other animals, particularly our primate relatives, but much higher levels of proactive aggression. In terms of reactive aggression, we align with Rousseau, while in terms of proactive aggression, we align with Hobbes.
Humans are not as physically strong as our ancestors because we did not evolve to fight in the same way. Our fighting methods became more proactive, involving the use of weapons and sports. Similarly, sports were not initially developed for exercise purposes but rather as organised play to teach survival skills and cooperation. It was only when physical labor decreased that sports became a means of exercise. In modern times, we promote sports as a way to stay healthy, although the effectiveness of some activities like darts may be debatable.
MYTH #8 You Can’t Lose Weight by Walking
Unlike modern exercise routines, our ancestors didn’t walk for fitness; they walked to survive. Take the average hunter-gatherer, like the Hadza people, who clock about nine to six miles daily, respectively. Their walks weren’t about hitting the gym but about meeting daily needs. Picture this: every year, these ancient humans covered a distance akin to traversing from New York to Los Angeles. It’s a testament to our natural inclination for long-distance walking.
Despite its ubiquity, walking alone might not be the silver bullet for weight loss. Some argue it burns too few calories and could even trigger hunger. An article in Time magazine back in 2009, titled “The Myth About Exercise,” made this point clear. But before diving into these debates, let’s unravel the mechanics of bipedal locomotion.
Why do we walk upright? Compared to our knuckle-walking primate cousins, walking upright has significant energy-saving perks. A seven-mile stroll for a human burns around 325 calories, whereas a chimpanzee would burn about 700 calories using their less efficient knuckle-walking technique. By walking upright, our ancestors saved a whopping 2,400 calories weekly, equivalent to the energy needed for about forty-five marathons.
The shift to bipedalism wasn’t arbitrary; it was an adaptation to our environment. For generations, our ancestors relied on walking vast distances daily. Even today, remnants of this instinct linger, with many of us conserving energy by minimizing unnecessary walks. This contrasts sharply with our ancestors, who routinely carried significant loads while walking, such as infants, food, firewood, and water.
Enter the constrained energy expenditure hypothesis, which sheds light on the complexities of metabolism and weight loss. Studies on the Hadza people reveal a fascinating phenomenon: despite their high activity levels, they burn similar daily calories as sedentary individuals with comparable body compositions. Similarly, studies across different populations show that more physically active individuals don’t necessarily have higher total energy budgets.
This phenomenon can be attributed to the constrained energy expenditure hypothesis, suggesting that our total energy budgets are finite. In simpler terms, if we expend extra calories through physical activity, our bodies may compensate by reducing resting metabolism to maintain overall energy balance. While this hypothesis is still under scrutiny, it suggests that even avid exercisers might burn nearly the same daily calories as their sedentary counterparts, highlighting the intricate interplay between activity levels and metabolism.
Myth #9 Running is Bad for your Knees
In a discussion centered around pigs, Lieberman was alerted to the significance of maintaining a steady gaze while running, a feat pigs are unable to accomplish. This observation sparked an inquiry leading to the identification of a nuchal ligament located at the back of the heads of animals evolved for running. This ligament functions as a spring, stabilizing their heads during movement. Remarkably, both humans and fossil species from the Homo genus possess this ligament, suggesting that humans were anatomically adapted for running millions of years ago.
Around two million years ago, Homo erectus had evolved the necessary physical attributes to run long distances, particularly in hot environments for hunting and scavenging purposes. Evidence indicates that our ancestors occasionally hunted by outrunning swift animals. Despite this evolutionary heritage, the majority of modern humans engage more in walking than running, and even the swiftest among us are slower and less agile than many animals.
How do Humans Outrun Horses?
To comprehend how humans can outrun horses, we need to compare marathon running speeds with the trotting speeds of horses, greyhounds, and ponies. While animals like horses, dogs, zebras, and antelopes can sprint faster than humans, they lack the endurance to maintain their pace for extended distances, especially in hot conditions.
Humans exhibit a unique ability to engage in long-distance running regularly, unlike most wild animals. While social carnivores like wolves, dogs, and hyenas may run up to ten miles during hunts, few other animals voluntarily engage in extended running without external compulsion. Antelopes sprint to evade predators, but these bursts of speed last only minutes. Although some animals, like dogs and horses, can cover many miles, they typically do so under coercion.
Why Are Humans Good at Endurance Running?
Several physiological adaptations enable ordinary humans, descended from flat-footed apes, to excel at endurance running:
High-performance Legs: Human legs possess elongated and elastic tendons, such as the Achilles tendon, which act as springs during running, propelling the runner forward with each stride. These adaptations are unique to humans among primates and contribute to our running efficiency.
Sweating: Humans possess an exceptional sweating capacity, crucial for dissipating heat generated during running. Sweating facilitates evaporative cooling, preventing overheating during prolonged physical activity. Humans have a high density of sweat glands distributed throughout their skin, aiding in thermoregulation.
Elastic Hearts: Humans have voluminous and elastic heart chambers, allowing for efficient circulation of oxygen-rich blood during exercise. This adaptation enables the heart to pump large volumes of blood to working muscles, sustaining endurance.
Slow-Twitch Leg Muscles: Human leg muscles predominantly consist of fatigue-resistant slow-twitch fibres, enhancing endurance compared to apes, which have a lower proportion of these fibres.
Despite the inherent advantages for running, many runners experience injuries. Research suggests that the risk of running-related injuries is highest among beginners, competitive runners focused on speed, and marathoners. However, common misconceptions regarding the detrimental effects of running, such as the belief that it leads to osteoarthritis, have been debunked by scientific studies. In reality, running can promote healthy cartilage and protect against osteoarthritis, highlighting the importance of dispelling myths surrounding running-related injuries.
MYTH #10 It’s Normal to Be Less Active as We Age
Fitness and Chronic Diseases: For many years, scientists at the Cooper Center followed the health of over 18,000 middle-aged people who were initially in good health. They wanted to see who among them developed chronic conditions like Alzheimer’s and diabetes. What they discovered was that those who were more physically fit were about half as likely to get chronic diseases. And if they did get sick, it happened later in life. These findings support the idea that staying active helps keep us healthy as we age. As the saying goes, “Men do not stop playing because they grow old; they grow old because they stop playing.”
The active grandparent hypothesis: To understand why exercise is so important for aging, let’s introduce a new idea: the active grandparent hypothesis. This idea builds on the grandmother hypothesis, suggesting that humans evolved to live longer not only because of genes that help us survive past fifty but also because older individuals needed to stay physically active to help younger relatives, like children and grandchildren. So, genes that help repair and maintain our bodies during physical activity were also favored by evolution. Physical activity, especially as we get older, triggers many mechanisms that promote longevity and good health, which both depend on and contribute to physical activity.
The active grandparent hypothesis suggests that in ancient times, being old didn’t mean sitting around leisurely; it meant being active, like walking, digging, and carrying things. Natural selection favored older individuals whose bodies could repair and maintain themselves during these activities. Since our ancestors didn’t have the luxury of retiring and relaxing, their bodies evolved to respond to the stresses of physical activity.
Let’s compare the walking habits of Americans and Hadza people. A study found that the average American woman aged 18-40 walks about 5,756 steps per day (around two to three miles), but this decreases significantly with age. By the time American women reach their seventies, they take about half as many steps. In contrast, Hadza women walk twice as much per day as Americans, with only slight reductions in activity as they age. Additionally, elderly Hadza women engage in more moderate to vigorous activity than younger women who are still bearing children. If elderly American women had to walk five miles a day for daily activities like shopping and gathering food, they would likely be in better shape. Hard work helps maintain the fitness of elderly hunter-gatherers, and walking speed is a reliable indicator of age-related fitness that correlates positively with life expectancy.
Furthermore, how did our ancestors deal with aging when they couldn’t hunt and gather anymore? Some modern societies offer nursing homes and pensions to support the elderly. But in ancient times, those who couldn’t perform physically demanding tasks became burdens when food was scarce. So, if humans evolved to live long after they stopped having children, they likely weren’t meant to spend those years in a state of chronic disability. From a Darwinian viewpoint, it’s best to live long and actively and then die quickly once physical activity declines. But it’s even better to prevent age-related decline altogether.
Why do we age?
At a cellular level, aging involves various harmful processes that damage cells, tissues, and organs. One process stems from the chemical reactions that occur in our bodies to sustain life.
Breathing: When we breathe in oxygen, our cells use it to produce energy, but this process also creates unstable oxygen molecules called reactive oxygen species or free radicals. These molecules can damage the body by stealing electrons from other molecules in an uncontrolled manner, leading to oxidation.
Mitochondrial dysfunction: Another contributor to aging is malfunctioning mitochondria. These are small organelles in cells responsible for generating energy (ATP) by burning fuel with oxygen. When mitochondria malfunction, they produce reactive oxygen species that can damage cells.
Glycation: Another harmful process is glycation, which occurs when sugar and protein combine in the presence of heat. This can cause tissue damage and generate advanced glycation end products (AGEs), which have various harmful effects on the body.
In addition to these processes, there are other ways cells can age, such as epigenetic modifications and the accumulation of molecules on DNA. These processes gradually cause chaos in our bodies, leading to various health problems.
Why does exercise slow down aging?
Many studies have shown that exercise has anti-aging effects, but the underlying reasons are not fully understood. One possible explanation is that exercise helps prevent or mitigate factors that contribute to aging.
Fat: Exercise helps reduce the build-up of excessive fat, particularly visceral fat, which can cause inflammation and other health problems. It also decreases levels of sugar, fat, and unhealthy cholesterol in the bloodstream, which can contribute to arterial stiffening and other disruptions in the body.
The costly repair hypothesis: Exercise can cause damage to the body, but it also stimulates repair processes that can help restore tissues to their previous state. These repair processes require energy and resources but are less costly than the exercise itself. Our bodies have evolved to allocate resources efficiently, so they can respond to the demands of physical activity while still maintaining overall health.
Mortality and morbidity: While exercise can help delay ageing and prevent many chronic diseases, death is still inevitable. However, engaging in healthy habits like exercise can reduce the risk of falling ill and increase the likelihood of maintaining good health as we age.
In summary, physical activity is crucial for maintaining good health as we age. Our bodies have evolved to stay active, and physical activity can help delay ageing and prevent many chronic diseases. It’s never too late to start exercising, and even small changes can have a big impact on our health and longevity.
How to Make Exercise Happen
To Move or Not to Move?
Throughout history, people of all ages relied on physical activity every day just to get by. They spent hours walking, digging, and doing other essential tasks to survive. Sometimes, they also enjoyed activities like dancing and playing for fun and to connect with others. But generally, they avoided unnecessary physical activities that didn’t help them survive or reproduce. It’s interesting because our bodies actually need physical activity throughout our lives to work at their best. However, our minds aren’t always eager to exercise unless it’s necessary, fun, or rewarding.
In today’s world, we find it hard to get enough physical activity through exercise, which is often seen as something optional and not very enjoyable. Despite doctors, trainers, and fitness experts telling us to exercise, many of us still avoid it.
The urge to put off or skip exercise is something many of us experience, and environments that don’t encourage or support physical activity tend to make us more sedentary. When we’re faced with the choice between lounging in a comfy chair or breaking a sweat with a workout, the chair usually wins. Even though we know exercise is important, our instincts might say, “I’ll do it later.” Maybe we feel short on time or energy, or it’s inconvenient to be active because of things like a lack of sidewalks or unappealing stairs.
So, how can we encourage exercise? According to Lieberman, we need to recognise that choosing to exercise for health and fitness is a modern behaviour that our brains might resist. To do this effectively, we should reconsider two things from an evolutionary and anthropological perspective: necessity and pleasure.
First, let’s talk about necessity. We all know exercise is good for us, even if billions of people don’t get enough of it regularly. But feeling bad about not exercising doesn’t usually help, especially when people who do exercise brag or nag about it. The issue here is the difference between knowing we “should” exercise and feeling like we “need” to. While we know we should exercise to improve our health and happiness and live longer, there are plenty of reasons why we might not need to. In fact, it’s possible to lead a pretty healthy life without much exercise.
Exercise seems unnecessary, especially in our modern world where technology has made many physical tasks much easier. We can go a whole day without breaking a sweat thanks to things like driving everywhere and sitting for hours at work. Even everyday chores like cooking and cleaning have become less physically demanding. Plus, exercise takes up time that could be spent on other important things, like work or family.
Despite these challenges, it’s worth noting that exercise is mainly done for its emotional and physical rewards, not because it’s a necessity.