2024 Fall | Biomechanics in the Wild

The Biomechanical Blueprint: How Cheetahs’ Bodies Are Engineered for Speed

The cheetah (Acinonyx jubatus) is the fastest land animal on earth reaching speeds of over 60 miles per hour (29 m/s). The cheetah is native to Africa and parts of the Middle East and is a predator of the impala, along with several other prey animals of the Savannah and Middle East. The biomechanics of the cheetah can help us understand how to create such high speeds in biological organisms and how to protect the body against high acceleration and decelerations.

In a study from 2012, researchers measured the speed and force of captive cheetahs in sprint and compared them to greyhounds, who have similar body structures to cheetahs. The experiment was set up similar to how greyhounds race with the cheetah’s chasing a “rabbit“. What Hudson et al. found was that cheetahs in full sprint put 70% of their body weight into their hind legs as compared with only 62% for the greyhound. This is coupled with the fact that the cheetah had a longer stride length and a higher frequency of strides, both of which led to a faster ground speed.

Image showing the experimental setup for measuring force during a run. A force plate is positioned on the ground, with high-speed cameras placed on either side, perpendicular to the direction of the run, to capture detailed motion data. — The Greyhound and Cheetah Experiemnt setup (Hudson Et Al. 2012)

Another study accounted for the fact that cheetahs in captivity do not run at their maximum speed. This is presumed to be because cheetahs in captivity have no reason to subject their bodies to these accelerations and decelerations. This study instead put an accelerometer and Global Positioning System (GPS) inside a collar and put them around the neck of three females, and two male cheetahs. An accelerometer is able to track its orientation and using different equations, is able to track the acceleration in all different directions. Using the data collected by these collars, the researchers found that the cheetahs were able to accelerate by up to 3 meters per second and decelerated by up to 4 meters per second in a singular stride length. What these researchers also found was that in comparison to other greyhounds specifically, cheetahs had a longer and stronger propulsive muscle group, like their hamstrings. Even though the stride frequency was similar between the cheetah and greyhound, the cheetah’s muscles were able to shorten at a greater speed, creating more force. This is because force is equal to mass multiplied by acceleration (F=ma) and because the acceleration of the shortening of the muscles is greater, it generates a greater force. In addition, another study found that in comparison to impalas, the cheetah’s main prey, the cheetah had a 20% increase in the power output in their high-performance muscles. Wilson Et Al. also found that in order to fully control their acceleration and deceleration, cheetahs have non-retractable claws in order to fully grip the ground more effectively. Lastly, it was found that the cheetah, uses an extremely low center of mass in order to make high velocity turn. Using this technique plus the grip with their claws, cheetahs are able to manuever at high speeds.

Figure divided into four quadrants illustrating aspects of a cheetah's movement and anatomy. Image A: A cheetah with a collar around its neck, representing a tracking or monitoring device. Image B: A cheetah wearing a collar shown in a pivoting motion with a force diagram indicating forces acting near its center of mass. Image C: Close-up of a cheetah's irretractable claws, highlighting an anatomical feature aiding in traction. Image D: A collared cheetah decelerating from a run, illustrating its movement while slowing down. — Figure showing the collar used in the Wilson Et Al. experiement. (Wilson Et Al. 2013)

In conclusion, the cheetah uses a majority of hind muscle groups to propel itself forward at a high stride frequency. This is coupled with small inertial adjustments as well as traction from the claws to achieve extreme speeds of over 60 miles per hour. In order to truely find the maximum speed of the cheetah, more work needs to be done to study this remarkable animal.

Aliens of the Ocean – How Can an Octopus Manipulate its Body So Well?

Nine brains, eight arms, three hearts, and zero bones – what on Earth could be built like this? The answer… an Octopus!

The octopus is a creature that not only intrigues the avid scuba divers of the world but many in the science community. Often referred to as a “sea alien” – the octopus is a creature that contains extraterrestrial looks and abilities. Regardless of their size, octopuses can morph themselves into incredible shapes and sizes to allow themselves to squeeze through small spaces or expand to demonstrate strength against possible predators. The purpose of this paper is to explore the unique muscular and connective tissue structure of octopuses and how this allows them to do so many out-ofworldly abilities.

Endurance Performance: The Biomechanics of VO2 Max and Muscle Fatigue in Endurance Sports

Endurance athletes, ranging from marathon runners to long-distance cyclists, are frequently faced with the mechanical limits of their muscles and bodies. But what sets these limits? A key limitation is the anaerobic threshold. The anaerobic threshold is the point at which the body shifts from aerobic to anaerobic metabolism, which causes a buildup of lactate and ultimately muscle fatigue. This is particularly an issue for endurance athletes because is limits the athlete’s ability to sustain force production and resist fatigue, lowering their endurance capabilities.

How Do Chameleons Catch Food with Their Tongues?

Have you ever wondered how chameleons are able to shoot out their tongues, grab a snack, and bring it back to their mouths? That skill is all thanks to the chameleon tongue’s unique mix of special muscles. Their ability to use their tongue for grocery shopping is essential for their survival, and the way it works is fascinating!

Apart from the famous color-changing skin chameleons have, they possess a magnificent power within their mouths. The chameleon tongue sits loaded in the mouth, always ready to attack the prey. When ready to shoot, they push their tongue against a bone inside of their mouth, which throws the tongue forward at a rate of up to 50 milliseconds, according to The Elastic Secrets of the Chameleon Tongue by Derek E. Moulton – that is less than a tenth of a second! This pushing off is similar to needing starter blocks in track to have an explosive start. After being shot out, the tongue separates into sections that lengthen telescopically, like the well known toy lightsabers (Moulton, 2016). These sections are referred to as sheaths, and they are said to contain all of the potential energy needed to shoot the tongue out so far (Moulton, 2016). Before launch, the sheaths look like concentric cylinders stacked together – think of cutting a jawbreaker in half and seeing all of the layers of circles, except there are only a few, large layers. Once the tongue has been released, it can reach up to 2.5 times the length of the body of the chameleon (Moulton, 2016)! In order to actually get a grip on the prey, the tongue is equipped with a type of sticky pad, as claimed by Peter C. Wainwright in The Mechanism of Tongue Projection in Chameleons: I. Electromyographic Tests of Functional Hypotheses. After the prey is caught (or missed), it takes a little bit longer for the chameleon to bring its tongue back into its mouth (Moulton, 2016). This type of retraction can be found in other nature, such as an elephant’s trunk (Moulton, 2016).

Short video of green and blue striped chameleon. It is sitting on a branch and extending its pink tongue quickly

Chameleons eat all kinds of insects, such as crickets, grasshoppers, and if the chameleon is large enough, sometimes even small birds (San Diego Zoo, 2024). What if the prey is unusually large or heavy, though? How can a tongue carry that load back into its mouth? The chameleon tongue is made up of various extraordinary muscles. Take a moment and think about how a chameleon would go about hunting its prey; it tries its best to blend into its surroundings, and after waiting for the prey to come near, it strikes quickly with its killer tongue. In order to have such a fast strike, the chameleon first uses the special muscles in its tongue, called hyoglossus muscles (found in many animals), and then applies the accelerator muscle to push its tongue out (Wainwright, 1992). These hyoglossus muscles help to push against the bone that was mentioned above. Then, the retraction muscles are utilized, and the hyoglossus continue working (Wainwright, 1992). The retractor muscles can be thought of as the accordion part of a bungee cord; they can be stretched out and bounce back to a shorter length. Those muscles are said to have “evolved supercontractile properties” that allow the chameleon to pull its prey in from various distances, according to Functional Implications of Supercontracting Muscle in the Chameleon Tongue Retractors by Anthony Herrel. After a bit of a workout, the chameleon then has a tasty meal to enjoy, that is, if it has good aim!

Featured Image from Pixabay

Category: 2024 Fall