Walking

Walking, also known as ambulation, is a primary method of terrestrial locomotion for legged animals. It is a way of moving across land that is typically slower than running or other gaits. Scientists define walking as an "inverted pendulum" gait. In this process, the body vaults over a stiff limb or limbs with every single step. This mechanical pattern applies to many different creatures. Even arthropods with six, eight, or more limbs use this method to move.

There is a mechanical way to distinguish walking from running in humans and other bipeds. In walking, only one foot leaves the ground at any given time. This creates a period of "double-support" where both feet are in contact with the ground. In contrast, running is defined by a phase where both feet leave the ground during each step. You can also identify walking by measuring the height of a person's center of mass. During walking, the center of mass reaches its maximum height at mid-stance. In running, the center of mass is at its minimum height during that same moment.

Walking has deep evolutionary roots that stretch back millions of years. Some scientists theorize that walking among tetrapods began underwater. Air-breathing fish may have "walked" on the ocean floor, potentially leading to land-dwelling life. For example, little skates use their pelvic fins to push off the ocean floor. This neural mechanism may have evolved as early as 420 million years ago. While terrestrial tetrapods likely have a single origin, arthropods evolved walking independently several times. This includes groups like hexapods, crustaceans, and tardigrades.

For human ancestors, bipedal walking was a defining characteristic. Fossil evidence suggests that walking on two legs emerged before other major Hominidae traits. Footprints discovered in Kenya suggest ancestors may have walked like modern humans 3 million years ago. This shift was likely driven by metabolic energy efficiency. Human walking is slightly more efficient than the travel of a quadrupedal mammal of similar size. For instance, chimpanzees expend 150% of the energy required by true quadrupeds. Human locomotion is approximately 75% less costly than the movement of chimpanzees.

Our bodies possess specific anatomical features that make this efficiency possible. Humans have longer legs and short, dorsally oriented ischia, which are parts of the hipbone. These features result in longer hamstring extensor moments to improve energy economy. We also have long Achilles tendons that support efficient bipedal movement. Additionally, humans have long femoral necks. This means our hip muscles require less energy to flex while we move. Even early hominins like Ardipithecus ramidus showed signs of energy-efficient bipedal walking.

Walking provides significant health benefits for the human body and mind. Regular, brisk exercise can improve stamina, energy, and weight control. It can also reduce stress and improve mental functions like memory, concentration, and creativity. For people with diabetes, walking two or more hours a week lowered mortality rates by 39 percent. Studies show that taking 4,500 to 7,500 steps a day may reduce premature deaths. A 2023 study found that just 2,337 steps a day reduces the risk of cardiovascular death. Even a light walk after a meal can help reduce glucose spikes.

People also use different techniques and tools to change how they walk. Nordic walking uses specially designed poles to engage the entire body. This activity stimulates muscles in the chest, arms, and core. It can increase energy consumption by up to 46% compared to walking without poles.

Other variants include snowshoeing, which uses wide footwear to provide "flotation" on snow. There is also scrambling, a slow and careful way to walk up steep mountains using both hands. People even participate in beach walking competitions on non-compact sand.