Human beings are not made to run fast, but we are made to run long distances. Here is anatomical and physiological evidence that we are better adapted to endurance running than many other mammals.
Humans of the 21st century are sedentary. Modern urban life and technology make running unnecessary to survive. Maybe we run sometimes to get on public transportation or to check our card on time at work, but there are many of us who work sitting for hours. However, more and more people run to stay agile and healthy, or simply because running makes them feel good. Every year the number of people who participate in a marathon or triathlon increases. These skills require strenuous efforts for those of us who lead a sedentary life, but which, apparently, are not unnatural for us.
Contrary to what many think, the marathon is not a sport that demands more from the body than it can give. Biologist Dennis Bramble, from the University of Utah, and paleoanthropologist Daniel Lieberman, from Harvard University, assure that the endurance race was crucial in the evolution of the Homo sapiens and that the body has the anatomical and physiological elements necessary to go at a fast pace for a long time.
Many mammals surpass man in sprint, which consists of running at your maximum speed for a short period of time. The cheetah is the fastest animal, reaching 120 kilometers per hour. The fastest dogs reach 50 kilometers per hour. On the other hand, the maximum speed of a top athlete in the 100-meter dash race is just 36 kilometers per hour. The speed of sprint It can be maintained for a short time because the effort it requires raises the body temperature above 40 ° C. All animals, including man, stop running when their body reaches that temperature. If they persist they can die.
But in endurance running, humans surpass most mammals, as Bramble and Lieberman point out, because our body is adapted to use energy efficiently, control its temperature and maintain body stability despite the complexity of the movements. necessary for running.
Exclusive tendons
In an article published in the journal Nature in 2004, Bramble and Lieberman show that when running the legs behave like a spring that stores and recycles the energy of each stride. When stepping, the arch of the foot is compressed at the same time as the knee bends; The center of gravity of the body lowers and in the next step it is propelled upward. The kinetic energy of this foot landing is stored in the arch tendons and the large Achilles tendon, which connects the calf muscles to the heel bone and the iliotibial ligament. This ligament connects from the iliac bone to the tibia, with the most powerful muscle in the human body, the gluteus maximus. Neither the gluteus maximus, nor the Achilles tendon, nor the iliotibial tendon intervene when walking; They are exclusively for running.
Tendons form the junction between muscles and bones and contract and extend like springs to take the next step. They are composed of a protein called collagen, which has precisely the structure of a spring. Collagen fibers are coiled to give the tendon great strength and the ability to store elastic energy. Animals that run, such as gazelles or kangaroos, have large tendons. In those who do not run, the tendons are very small or non-existent.
Recently Herman Ponzer, an anthropologist at Washington University in St. Louis, Missouri, developed a mathematical model based on physics principles that proves that the energy consumed when running depends on two main factors: speed and leg length. In both man and animals, the longer the legs are, the fewer the up and down movements are exerted when running, which considerably reduces the force needed to push down with each step. Bramble and Lieberman experimented with people, dogs, goats and other animals on treadmills that they adapted in their laboratory, and calculated the energy expended by measuring the oxygen their organisms consumed when running the same distance. In all cases, this energy is inversely proportional to the length of the legs; That is, the longer the length, the less energy expended.
“Nike! Nike!”
This is how Pheidippides shouted with all his might at the gates of Athens one day, 2,500 years ago. It was not advertising for sporting goods (niké in Greek, means “victory”), but rather news: the Athenian army, made up of only 12,000 soldiers, had just defeated the Persian enemy, 10 times larger, on the beaches. from Marathon, 42 kilometers northeast of Athens. It was essential to announce the news promptly, because the Persians, seeing themselves defeated, thought that the city was unprotected. The Persian survivors returned to their ships to head by sea to Athens. If they were lucky, they would catch her by surprise. Pheidippides’ announcement gave the Greeks the necessary encouragement to defend the Acropolis with the precarious army that had been left defending the city.
Tailless runners
When animals run, they maintain their stability thanks to their tail. The movement of this counteracts the tendency to fall forward caused by the inertia of each stride. In our case, since we do not have a tail to step on, our trunk leans forward every time our foot hits the ground, and the gluteus maximus, which is a huge muscle, contracts and prevents us from falling. The relatively narrow waist combined with the mobile chest allows alternating movements of the arms and shoulders to also counteract the tendency to fall flat on one’s face.
On the other hand, the mobility of the neck vertebrae could cause the head to sway freely while running. However, humans have a ligament that inserts from the base of the skull to the seventh cervical vertebra—the nuchal ligament—which keeps the head level. This way we can run with our eyes fixed forward and without losing our balance.
The best cooling system
The amount of heat released from the body of any running animal is enormous. But to function well, the body must be kept at a temperature of less than 40 °C, otherwise the biochemical processes of the cells begin to fail and some proteins lose their structure. All organisms have a cooling system for these occasions, but none as efficient as ours.
Humans, unlike most animals, have millions of sweat glands in our skin to eliminate water through sweat. The amount of water removed is directly proportional to the rise in temperature. When sweat evaporates, it absorbs large amounts of heat, which cools the skin and, through it, the entire body. Since, unlike animals, our skin is not covered with hair, the air can also contribute to our cooling. Animal hair, on the other hand, traps heat.
Most animals eliminate heat by panting, but panting interferes with breathing and makes it less efficient. This is one of the main reasons why, despite being very fast in the sprint, other animals are not as good as man in the endurance race. We breathe through our mouths when running to increase our respiratory capacity. According to Bramble and Lieberman, this also helps dissipate the heat we generate during the race.
The first races
To know how and when races began among hominids, anthropologists refer to the fossil evidence of our ancestors such as the Australopithecus afarensishe Homo erectus and the Homo sapiens from other times, as well as the skeleton of today’s chimpanzee.
Humans and chimpanzees come from the same lineage (see As you see? No. 135), as shown by the great similarity between the genomes of both species. Despite the similarity, these monkeys are terrible runners: their hips are narrow and therefore their iliotibial ligament, gluteus maximus and the large tendons of the legs are very underdeveloped. Additionally, chimpanzees lack a nuchal ligament to stabilize their heads. Instead, they have powerful muscles that hold their shoulders, cervical vertebrae, and skull tightly together. This muscle mass, their long arms, their short legs and the arrangement of the bones in their feet and hands help them to climb and hang from trees, but not to run.
In 1974, paleoanthropologist Donald Johanson’s team found fossil remains in a region of northeastern Africa that, although similar to those of a chimpanzee, also had marked differences. Johanson classified them as belonging to hominids of the species Australopithecus afarensis. The most complete skeleton that was obtained (of a female) was named Lucy (that day they had been listening to the Beatles song over and over again Lucy in the sky with diamonds). He A. afarensis It inhabited that area 3.9 million years ago and remained there until three million years ago.
Lucy’s family had longer legs than chimpanzees and, as shown by the angle that the femur makes between the hip and the knee, already walked on two legs. However, her thorax, arms, and the curvature of her fingers and toes show that she was better adapted to climbing than walking, and that she hardly ran. Her skull had a volume of approximately 400 ml; Her occipital bone does not show the mark left by the nuchal ligament and the space in the inner ear occupied by the semicircular canals that serve to maintain balance is very small. This makes us think that her running movements would have caused dizziness and disorientation to Lucy and her peers. The next ancestor that appears in our family album is Homo erectus, who emigrated from Africa to Southeast Asia. Fossil remains of this ancestor, who lived approximately two million years ago, have been found in various parts of the world. Its appearance is very similar to ours. Although his skull is smaller, it is larger than Lucy’s and has the part where the nuchal ligament inserts is well marked. Bramble and Lieberman believe that the Homo erectus He was the first of our ancestors who was adapted for endurance running. And why did he want to run? Homo erectus? Researchers suggest that the ability to run long distances may have been useful for hunting (for example, allowing them to get close enough to prey to throw spears at them, or by chasing them to death from exhaustion). Thus, meat, marrow and brains were added to the diet of this ancestor of ours, and…