Running

Running is a method of terrestrial locomotion used by humans and many animals to move quickly on foot.

Unlike walking, running includes a distinct aerial phase. During this phase, all feet are briefly above the ground at the same time. Walking is a slower movement where at least one foot always maintains contact with the ground. In walking, the legs remain mostly straight, and the body's center of gravity vaults over the stance legs like an inverted pendulum. Running, however, utilizes spring-mass mechanics to maintain speed. This process involves the simultaneous change of kinetic and potential energy within a single stride.

Energy is stored and released through springy tendons and passive muscle elasticity.

To understand the mechanics, one must examine the running gait cycle. This cycle can be divided into the stance phase and the swing phase. The stance phase begins with the footstrike, when a portion of the foot makes contact with the ground.

There are three common types of footstrike: forefoot, midfoot, and heel strike. During footstrike, the hip joint undergoes extension from its previous maximal flexion. The absorption phase follows, where the body attenuates the forces of initial contact. This continues until the runner reaches midstance. At midstance, the limb is positioned directly underneath the trunk, pelvis, and hips.

Propulsion is the stage where the body is actively pushed forward. This occurs from midstance through the toe-off point. During this phase, the hips undergo extension, the knee joint undergoes extension, and the ankle undergoes plantar flexion.

The setup for this movement actually begins during the terminal swing. At that time, the hip joint flexes, allowing the hip extensors to generate force. As the runner enters midstance, the hip extensors continue contracting. This motion pulls the ground underneath the body to propel the runner forward. The final push during toe-off involves the coordinated work of the ankle, knee, and hip joints.

The swing phase begins once the foot leaves the ground. The initial swing is a response to the propulsion movements of the body. During this stage, hip flexion and knee flexion occur to return the limb to its starting position.

The initial swing ends at midswing, when the limb is again directly under the hips. Terminal swing then follows, as the knee begins to extend slightly toward the front of the body. This prepares the foot for the next footstrike, completing the cycle for that limb. Because the limbs work in opposition, one leg is always in a recovery phase while the other is in a stance phase.

Running is not just a function of the legs; the upper extremity is vital for balance.

The arms move in conjunction with the opposite leg to counterbalance the body. Elite athletes often keep their elbow joints at approximately 90 degrees or less. The hands swing from the hips up to mid-chest level. The humerus moves from being parallel with the trunk to about 45 degrees of shoulder extension. The trunk itself provides a stable anchor point. It undergoes only slight rotation to prevent wasted energy from excessive transverse motion.

Human running has a deep evolutionary history. It is thought that running evolved at least four and a half million years ago.

This ability likely emerged from the Australopithecus, an early human ancestor that could walk upright. Many scientists believe humans developed into endurance runners through persistence hunting. This involved chasing prey until the animal succumbed to exhaustion or "chase myopathy." This activity may have caused specific physical changes, such as the development of the nuchal ligament, Achilles tendons, and large glutei maximi muscles.

Competitive running has also been a part of human culture for millennia. Many traditions grew out of religious festivals in places like Egypt, Asia, and Greece.

The Tailteann Games in Ireland provide some of the earliest records, dating back to 1829 BCE. The first recorded Olympic Games took place in 776 BCE. In Ancient Greece, running was not limited to men.

Women competed in the Heraean Games, which were held just before the Olympics. In these races, maidens ran a course of 500 feet. Winners received olive crowns and a share of a sacrificed heifer. Today, running remains one of the most accessible sports in the world.