Jumping

Jumping is a specific form of locomotion used by living organisms or mechanical systems. It involves propelling oneself through the air along a ballistic trajectory. This means the jumper follows a curved path through space. Jumping is distinct from gaits like running or galloping. In those gaits, the body is briefly airborne. In jumping, the entire body remains in the air for a relatively long duration. The initial launch also occurs at a much higher angle than in running.

The physics of jumping begins with the application of force. A jumper must push against a substrate, which is a supporting surface. This substrate can be a solid like the ground or a liquid like water. When the jumper applies force, the substrate generates a reactive force. This reactive force is what actually propels the jumper away. Once the jumper loses contact with the substrate, they follow a parabolic path. This curved path is determined by the launch angle and the initial launch velocity. These two factors dictate how high or how far the jump will go.

Launching angles play a major role in how far a jumper travels. In physics, the maximum horizontal distance for a projectile occurs at a 45° angle. However, any angle between 35° and 55° will still achieve ninety percent of that maximum distance. Humans are a bit different in their mechanics. For a human, the angle that maximizes horizontal distance is lower, around 23° to 26°. This is specifically noted in the mechanics of a standing long jump.

Muscles are the engines that drive the jump. During the propulsive phase, muscles do physical work to add kinetic energy to the body. Kinetic energy is the energy of motion. The amount of kinetic energy at launch is proportional to the square of the jumper's speed. To increase distance and height, animals often evolve long legs and large muscles. Long legs increase the time and distance over which an animal can push. This allows for more power and a faster launch. Many jumping animals are optimized for maximal power through their muscle structure.

Some animals use a clever method called power amplification to overcome muscle limits. Muscles have a physiological limit on how much power they can produce. To bypass this, species like grasshoppers use elastic elements such as tendons or apodemes. They slowly pre-stretch these elements to store work as strain energy. When released, these elastic parts can discharge energy at a much higher rate than muscle alone. This is similar to how a bow releases energy much faster than a human hand can throw an arrow. This method can increase power by two to seven times the level of equivalent muscle mass.

Anatomy varies greatly depending on the environment. Terrestrial animals typically use their legs, though some species use their tails. Frogs are considered the undisputed champions of vertebrate jumping. Their legs can be nearly twice their total body length. Their leg muscles may account for up to twenty percent of their total body weight. They even have extra joints in their ankles and hips to increase length. In contrast, aquatic species rarely have specializations for jumping. Some, like mud skippers, use a flick of the tail to jump on land.

Jumping can also be classified by how the feet move. A jump involves landing on two feet. A hop is jumping from one foot and landing on that same foot. A leap involves jumping from one foot and landing on the other. There are also complex movements like the assemblé and the sissonne. Humans use different techniques to change their jump height. Athletes use plyometrics, which are repetitive jumping exercises, to increase power and agility.

Technology is now mimicking these biological wonders. In 2021, researchers designed a robot that uses ratchets to jump. This mechanical system was able to jump vertically over thirty meters. This shows how understanding the mechanics of jumping can lead to incredible engineering. Whether in a grasshopper or a robot, the goal is the same: converting energy into a powerful launch.