Elegance in Running: How Humans Can Beat Cheetahs

PHYSIOLOGY Elegance in Running How Humans can Beat Cheetahs sarA remSen ‘12 umans do not make the world’s top 20 fastest runners. We Hlose our spot to animals like cheetahs and pronghorn antelope. But, do not discount yourself as a top performer; we are actually capable of outrunning cheetahs—as long as the race is longer than 600 yards. Humans are so specialized for running that we can win in an endurance race against almost any animal, includ- ing those animals that we consider un- beatable. As one tribe of Bushmen in Af- rica has demonstrated, winning against the world’s fastest animals is only a matter of finding the right distance. Throughout millions of years of evolution, terrestrial animals devel- oped many forms of getting around, Image courtesy of Steve Garvie. such as walking, hopping, slithering, Fig. 2: A giraffe in a jarring galloping gait. trotting, and running. Some terres- for the last 5 million years and are well awkward because their long, stiff legs trial animals are born to run; these adapted to the demands of their envi- prevent them from achieving the rapid “cursorial mammals” possess adapta- ronment (see Fig. 1). unlike lions, which stride rate of lions or cheetahs (see Fig. tions that make running easy and effi- depend on the other lions in the pride to 2). The cheetah’s solution to this re- cient. Running is a survival advantage; hunt, cheetahs hunt independently, us- striction is a flexible spine; it can coil these animals can travel further and ing their raw speed to catch an antelope. its long legs so compactly that its front more quickly to find food, escape from Their evolutionary success has been and hind feet never get tangled, which swift predators, and catch agile prey. driven in part by the cheetah’s successful allows it to flex and extend its legs 2.5 adaptations for the two components that times per second (1). In addition to a Specialized Runners drive speed: stride length and stride rate. long stride and fast stride rate, a chee- A cheetah’s full stride, from the tah‘s tail acts like a stabilizer, and its Cheetahs and pronghorn ante- contact of its left front foot to the next semi-retractable claws can grip the sa- contact of the same foot, can reach up lope are two of the most specialized vannah ground like track cleats (2, 3). to 25 feet in length (1). Both horses and and successful runners—and the two The cheetah’s adaptations for cheetahs gather their legs underneath fastest animals in the world. Chee- the speed record have compromised themselves during a gallop, with no feet tahs reach the global record at a top its long-distance stamina. Its high- touching the ground. Horses have a sin- speed of 70 miles per hour (mph), with ly-specialized sprinting gallop is ex- pronghorn antelope keeping pace at gle airborne moment during each stride, documented by Eadweard Muybridge in tremely fast, but also energetically 50 mph. Cheetahs have been sprinting exhausting; a cheetah can only run a after antelope on the African Savannah 1978 with a series of photographs called “The Horse in Motion.” In comparison, distance of 1,300-2,000 ft before it cheetahs gain a second airborne suspen- tires (1). Nevertheless, those 600 yards sion in a single stride when they extend are just long enough to chase down a both their front and hind legs (1). Like swift gazelle and score a meal, leav- other cursorial mammals, cheetahs’ long ing the lions to search for a new lunch. legs help them lengthen their stride. Long legs are good for long strides, but they limit the number of strides per Adaptations for second (stride rate). For example, gi- Endurance raffes spend their day walking, but can gallop when necessary. Giraffes’ move- The second fastest land animal is Image courtesy of Anup Shah/Nature Picture Library. ments are deliberate and somewhat a little-known New World runner: the Fig. 1: A cheetah breaking into a run. pronghorn antelope. The pronghorn FALL 2011 31 antelope ranges from western to cen- Who is still going after 100 miles? There legs also absorb shock by compressing tral North America, and is about the is a point at which horses and dogs can under our body, while our springy ten- size and shape of an African gazelle no longer sustain their running pace dons and ligaments store and release with long, spindly legs and two pronged and must stop—and then we catch up. energy over time. We can run for a long horns (Fig. 3). Like the cheetah, the While the cheetah maximizes time because our bodies are built to pronghorn is a champion sprinter, but stride length and rate for intense conserve energy at every opportunity. it also possesses additional adaptations bursts of speed and the pronghorn Our second unique adaptation is for sustaining high speeds. A prong- optimized its oxygen intake for flex- our ability to regulate our breathing horn antelope’s top speed is 60 mph, ible types of speed, humans spe- independently of our limb movement. but it can run for several hours at 35 cialize in long-distance marathons. Because all other cursorial mammals mph (4). At that pace, it can outrun a Humans are the only primates that are quadrupeds, the expansion of their biking Lance Armstrong over a 3-hour can run for extended periods of time; ribcage—and therefore the expansion of section of the Tour de France (5). chimpanzees and gorillas are incapable their lungs—is limited by each stride. As The pronghorn’s efficient adapta- of running upright for more than a few a cheetah gathers its legs midstride, its tions allow it to run for hours across the minutes. Dennis Bramble from the Uni- momentum slams the air out of its lungs; American plains, perhaps, as research- versity of Utah and Daniel Lieberman as it extends its legs, its internal weight ers suggested in a paper published in from Harvard University believe that pulls away from its chest and allows it Nature, to escape from the now-extinct our ancestors’ development of running to expand its lungs. The cheetah can- prehistoric American cheetah. Unlike 2 million years ago may have influenced not breathe more than once per stride. the modern cheetah’s flexible spine, the the evolution of human body. Humans Because humans stand upright, pronghorn’s spine is less flexible but evolved three ingenious adaptations the movement of our legs as we walk similar to the spine of a horse. A semi- that are remarkably well-suited to en- and run does not affect the expansion of flexible spine stabilizes the pronghorn’s durance running, allowing us to com- our lungs. Humans have only two gaits, vertical motion so that it spends less pete with the other cursorial mammals: walking and running. Unlike cheetahs, energy lifting its body into the air in our unique physical form, our ability we can breath faster than we can move each stride (1). Like horses and gazelles, to breathe, and our ability to sweat. our legs, getting the maximum amount pronghorn antelope have lost extrane- The human physical form is unique of oxygen to our muscles. The regulation ous digits and walk on their toes, giving among animal runners. The arch of the of our breathing allows us to run for ex- them more speed by reducing unneces- human foot is the biological engineer’s tended distances because we constant- sary bone and muscle weight at the end suspension bridge and one of the most ly remain in an energy-efficient gait. of their legs. Pronghorn antelope also simple, yet sophisticated adaptations Humans compete against other take in and use oxygen more efficiently for running. With each step we take, mammals with a third ingenious and than most other animals. The more ox- the lattice of tendons and ligaments unique adaptation: the ability to cool our ygen that pronghorn antelope breathe in our foot stretches to absorb shock body temperatures by sweating. Most in, the more oxygen that reaches their like an earthquake-proof bridge. Our animals cool themselves by seeking muscles; hence, the faster and longer their muscles can contract to allow them to run. Their maximum oxygen uptake relative to their body size is three times the uptake of any other running or flying animal (4). Pronghorn antelope have intricate lung surfaces to absorb the most oxygen possible to make the most out of each breath. They can also skip the warm-up jog because they are per- petually “warmed up”; they keep their muscles at a higher resting tempera- ture than other mammals of their size so they are ready to run immediately. The Human Physique At a first glance, we are quick to dismiss humans as wimps in the running race. Horses and dogs—not to mention cheetahs and pronghorns—can beat us effortlessly down to the end of a football field. However, what happens when one football field becomes 100 Image courtesy of Rick Berg. football fields or 10,000 football fields? Fig. 3: A pronghorn antelope in Wyoming. 32 DARTMOUTH UNDERGRADUATE JOURNAL OF SCIENCE compete on foot that the horserace split into the equestrian Tevis Cup and the world’s first 100-mile ultramarathon, the Western States 100 (7). While humans cannot beat dogs, horses, or cheetahs to the end of a football field, we are well adapted for races of 1,000 football fields. Although we have yet to compete directly against a pronghorn in an ultramarathon, per- sistence hunting shows that we are capable of running down a gazelle.

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