jumping | Biomechanics in the Wild

Springing Squirrels: The Mechanics of Squirrel Leaping and Landing

How do squirrels escape dogs, scavenge for food, and climb their way around trees? The answer is simple: squirrel parkour. With precise calculations and the physical ability to maneuver and adjust, squirrels can effortlessly leap from tree branch to tree branch without falling.

A study done by Nathaniel Hunt et al. tested squirrels on different activities where gap distance, flexibility of the launching bar, and gap height were varied. The squirrels were observed, and results showed a consistent trade-off scenario between branch flexibility and leap distance. When on high-flexibility branches, squirrels jumped closer to the branch connection point. This led to large gap lengths, up to three times the squirrel’s body length. The opposite was true for low-flexibility branches. Squirrels are able to determine branch flexibility and what launch point is necessary for them to safely make leaps to neighboring branches.

In terms of safety, throughout the course of the experiments, the researchers observed that not a single squirrel fell. They were able to successfully adjust to varying branch flexibility, height, and leap distance. The squirrels were able to accomplish this feature by performing a “parkour” move. The squirrels jumped off the branch toward a nearby wall and sprang off of it before landing. The squirrels utilized this parkour move to adjust their landing speeds. Not only does this demonstrate the adaptability of squirrels, but also their ability to adjust their bodies while jumping.

An important concept to consider when looking at mechanics of squirrels jumping is the force and speed at which they take off. Grégoire Boulinguez-Ambroise et al. completed a study to examine the effects of different branch sizes on squirrel take-off velocity and the displacement of their center of mass. Results showed that there was a difference between squirrels jumping upwards off of a flat plate, and off of a branchlike object. When jumping off the branchlike poles, squirrels prioritized shifting their center of mass to jump, whereas on the flat plates, priority was given to the produced force. These results imply that while on branches, squirrels try to maximize balance before jumping. This intuitively makes sense as you would want to be as balanced as you could before making a leap!

Two plots showing data from a study on squirrel jumping performance. One plot shows take-off velocity vs substrate diameter. The data shows the lowest take-off velocity occurring on the largest diameter substrate and the highest take-off velocity occurring on the smallest diameter substrate. The second plot shows the jump height vs the substrate size. The data shows an increase of jump size with a decrease in substrate diameter. — Figure 1. Data showing an increase in take-off velocity with a decrease in branchlike diameter as well as data showing an increase in jump height with a decrease in branchlike diameter. Image from Grégoire Boulinguez-Ambroise et al.

Interesting results, shown in Figure 1, showed that squirrels jumped the highest while jumping from the smaller diameter branch, and jumped the lowest when jumping from flat ground. Putting this together with the previously mentioned idea of squirrels shifting their center of mass, squirrels are able to adjust their approach to jumping depending on branch sizes.

Graphic of a squirrel foot and hindlimb on top of a substrate. A shear force, vertical force, and normal force are drawn in their respective positions. A small graphic of a squirrel standing on a substrate is displayed in the bottom right. — Figure 2. Force components between a squirrel foot and a pole substrate before vertical jumping. Image from Grégoire Boulinguez-Ambroise et al.

Based on the size of the branch, squirrels have to adjust their feet position. For smaller branches, squirrels must place the middle of their feet closer to the sides of the branch. Figure 2 shows the forces acting between the feet and the branch. Varying branch sizes will change the angles and size of the forces, and the squirrel will have to adjust accordingly. In the study mentioned above, results showed that the feet placement on the varying diameter sizes did not have a significant impact on the measured take-off velocity. This implies how squirrels can adjust to different sized branches and still maintain high quality jumping performance.

Diving into how squirrels jump, they use their hind limbs to push themselves off of an object. Richard Essner completed a study on squirrel launch kinematics. Results showed that for leaping, squirrels act as small-bodied primates and rely less on their knees than their ankles. Squirrels also use their tails to help with balance.

While squirrels may seem like cute animals who only care about adding to their nut collection, there is a lot more than meets the eye when it comes to their movement between and through trees. The nature of squirrels to be able to apply the parkour move, change foot placement, determine the flexibility of branches, and adjust take-off velocity depending on each individual branch they leap from are just a few of the amazing features that squirrels can accomplish.

Feature image from Pixabay.

Avoiding Cat-astrophe: How do Cats Land their Crazy Jumps?

Four panels showing the sequence of an American shorthair domestic cat jumping from the top of a fridge to a counter. The cat's body stretches long while in the air and curls up after contacting the counter.

Cats always land on their feet, or so the saying goes. Every cat owner has witnessed their feline make death defying jumps and walk away like it’s no big deal. 90% of cats can actually survive falling off of a high rise building. But how do they do it? How do cats absorb the impact of their leaps without sustaining injuries?

The Science Behind Load Management: How Isometrically Overloading Tired Knees Can Promote Growth and Healing

Many athletes who experience pain right below the kneecap after a spike in volume of explosive physical activities (ie. running/jumping) are diagnosed with patellar tendonitis, commonly referred to as runner’s or jumper’s knee. The suffix “itis” is Greek for inflammation and a common remedy is rest to reduce the inflammation. In some cases, an initial rest period combined with physical therapy to strengthen surrounding muscles such as the hip flexors and gluteus medius is enough to alleviate the knee pain for good, in other cases the rest is of no benefit or even worsens the patellar tendon’s condition and starts a chronic cycle of resting and then returning to activity in more pain than before. In these cases a more accurate diagnosis of patellar tendinopathy is correct. Patellar tendinopathy implies chronically recurring pain on the anterior of the knee that is difficult to treat. In such cases, an MRI often reveals small lesions throughout the patellar tendon indicating that the tendon is structurally damaged and not just inflamed. A better understanding of the patellar tendon’s biological composition, and biomechanical function may help to resolve future cases of patellar tendinopathy.

Which Body Mechanics Help You Jump Higher?

Vertical jumping is an essential aspect of many sports. In volleyball and basketball, for example, jumping higher than your opponent gives you a significant competitive advantage. Volleyball players need to be able to block and spike, while basketball players need to be able to rebound well and finish tough shots over opponents. Most athletes know the basics of jumping, but few know what specific body mechanisms contribute to jump height. This article will discuss four key elements to vertical jump height:

Squat depth
Non-extension movements
Arm swing
Toe flexor strength

Understanding the mechanics behind each of these elements can help guide athletes in training regimens to better increase jump height.

Jumping into Better Bone Health: Impact Exercise and Your Bones

When exercising for overall health, the general public tends to disregard the importance of bone health. Often the focus is on consuming milk or calcium rich foods, but are there certain exercises that can increase bone health? Studies show that the presence of impact in exercise plays a major factor.

As we age, everyone loses bone mineral density, which is a determining factor in bone strength and stiffness. Decreasing bone mineral density can lead to bones that easily break and fracture, and will, in extreme cases, result in the disease osteoporosis. Women are at a higher risk of osteoporosis because they lose more bone mineral density as they age due to the process of menopause. Increasing bone mineral density at younger ages can ensure that even with the inevitable bone loss, peoples’ bones are still strong.

Big Air: The mechanics of SKIERS and snowboarders landing after jumps

Have you ever watched the X-Games or Olympics or any other skiing or snowboarding competition and marveled at the sheer heights that the athletes achieve? Depending on the type of jump the skier goes off, they can reach heights of up to 50 feet off the ground. How exactly do the skiers land what are essentially free falls from such heights? Supposedly “survivable injuries” occur from falling heights above the “critical threshold” of 20-25 feet, so how do these athletes land from heights of up to double this?

Patellar Tendinitis: The Kryptonite of Jumping Athletes

Volleyball is a sport of quick movements. For hitters, one of the most common movements in the game is the jump, whether that be to block or to hit. Although a higher vertical leads to improvement in game performance, it can increase the risk of developing a serious injury that affects many volleyball players: patellar tendinitis. This condition is associated with pain and tenderness directly below the knee cap that is especially apparent during explosive, jumping movements. But what exactly causes this condition? And what can be done to remedy it?

Fish in Flight: The Science Behind Great White Breach Attacks on Cape Fur Seals

If you’ve ever turned on Discovery channel during Shark Week, then you’ve probably seen the iconic footage of a 2.5-ton great white shark leaping out of the water to catch its next meal. If you’re weird like me and you’ve ever tried to mimic one of these epic breaches in a backyard pool, then you realize just how difficult it is to generate enough momentum to jump even partway out of the water and therefore have a real appreciation for what it takes to pull off this incredible feat.

Artificial Turf: Game Changer or Game Ender?

Artificial turf fields were first introduced in the late 1960s and have grown tremendously in popularity since. Today, artificial turf fields can be found at all levels of sport, from youth league to professional, and across many different sporting disciplines. A major reason they are so popular is because they offer a consistent, low-maintenance, year-round green playing field in all weather conditions and climates. However, despite the benefits they provide, artificial turf fields are not without controversy. Even though artificial turf mimics grass in appearance, its properties are much different.

Secret Behind Kangaroos’ Tail

Red kangaroos can reach speed of more than 35 miles an hour, they can also cover an area 25 feet long and get up to 6 feet high in one jump using their tail like a spring to give them more power. When kangaroos want to move slowly, they do kind of lean on their tail, to support their body. When kangaroos are grazing they move their hind pairs of feet together which makes their movement awkward but the power behind them in their tail is keeping them balanced. There was always a question of why Kangaroos are placing their tail on the ground when they are walking slowly.

Tag: jumping