Limits to Locomotion

Factors Affecting Locomotion and Performance

Factors that affect locomotion, especially at faster speeds, determine the limits to how fast animals can move. This is directly related to athletic performance, where animals are often pushed to run faster or complete courses quicker.

Different limits to performance exist, which includes:

Confirmation of the Animal: An animal's physical structure and conformation can limit its performance. Confirmation is not easily changed except over generations through breeding programs. An animal's confirmation is largely fixed.
Gait: An animal's gait is more dynamic and can potentially be altered with training.

Turning Locomotion

Turning is a fundamental aspect of locomotion, present in various activities, including sports and everyday movements. The lecture focuses on high-speed turning and its relation to injury risk. While biomechanics can measure limb forces and joint angles, linking these measures to injury prevalence (often gathered through questionnaires) is challenging. An example of this is the study of box angles in canine flyball.

A PhD study examined box angles in canine flyball.
Fly ball involves dogs running to hit a box and return.
Competitors adjust the box angle (vertical or shallow).
The study measured force but found no significant effect of box angle on limb force, failing to clearly link box angle to injury.

Papers on Turning Locomotion

Two papers that discuss turning locomotion include:

"Turning Performance and Forelimb Loading in Polo Ponies and Racehorses" by Tan et al. (2010)
"Limitations to Maximum Speed During Cornering in Cheetahs" by Wilson et al. (2013)

Both papers utilize similar methodologies and technologies to measure turning, with overlapping authorship.

Video Analysis of Dogs Turning

A video demonstration using GPS-IMU units to measure dogs' locomotion during turning was shown. Data loggers were placed on the dogs using customized harnesses. The goal was to capture free turnings at high speed, but in some instances, dogs did not reach high speeds before turning due to distractions. The data loggers used in the demonstration were the same as those used in the cited research papers.

Limits to Turning Performance

Two primary factors limit turning performance in quadrupeds and humans:

Grip:
- The ability to maintain traction and prevent legs from sliding.
- Higher speeds and tighter turns increase the risk of slipping.
Limb Force:
- Turning causes ground reaction force to misalign with the center of mass, increasing limb force compared to straight-line running.
- This increased force can approach the limit the limb can withstand without breaking, causing the animal to slow down.

To manage these limits, animals slow down and increase their duty factor (the proportion of the stride the limb is in contact with the ground). Increasing the duty factor spreads the force over a longer time period, reducing its intensity. Animals with a narrow trackway width can lean into the bend to maintain speed, balancing stability and speed during maneuvering.

Additional Limits to Turning Performance in Dogs

A study proposed additional factors limiting turning performance:

Toppling Avoidance:
- Toppling can occur due to a lack of grip.
- Body weight should be less than the medial ground reaction force to avoid toppling.
Rotation of the Body:
- The ability to change heading angle effectively is critical.
- Factors like weight of the head, stride length, and body length can affect this.
- Stride length and body length also affects the ability to rotate.
- $Smaller$ animals outmaneuver big dogs when they're all running around due to shorter leg length.

Smaller animals can bring their center of mass closer to the ground leading to increased stability due to shorter leg lengths and a more crouched posture. Body length affects maneuverability.

Ground Reaction Force

During turning, ground reaction force often does not align with the center of mass, leading to higher limb forces in animals.

$Coefficient$ of friction is measured between zero and one.
$Cheetahs$ have a curve of friction usually of about 1.3.
$Horses$ are about 1.06.
$Dogs$ there was a study where they were about 1.1 something.

Natural surfaces generally provide more grip than synthetic surfaces. Measuring grip in animals is challenging due to ethical concerns, often requiring the use of cadaver limbs.

Analysis of Turning Performance in Horses

The Tan and Wilson paper utilized GPS-IMU units to collect data from racehorses and polo ponies, measuring speed and turning radius of the horses. The equation for the grip limit:

$Grip Limit = Coefficient ewline of ewline Friction * Normal ewline Force$

The equation for the limb force limit:

$Limb ewline Force ewline Limit = Maximum ewline Limb ewline Force ewline the ewline Limb ewline Can ewline Withstand$

The collected data was plotted on a graph with mathematically calculated force and grip limits to assess whether the biological data aligned with these theoretical limits. Racehorses did not reach the grip limit but approached the force limit, while polo ponies came close to both limits but closer to the grip limit.

Implications of the Horse Data

Polo ponies are probably more limited by grip than racehorses.
Racehorses are probably more limited by the force limit.

Polo ponies, performing tighter turns will hit high speed while racehorses maintain higher speeds on broader bends that make grip the limiter. Lean angle, which the study may not have directly calculated, is another relevant factor in turning performance.

Dog Turning Data

Dog turning data was also analyzed, using a similar methodology to the horse study. Dogs were run around a bend with a set radius, and their movements were tracked using GPS loggers. The peak force and grip limits were applied to the data. The data points fell closely under these limits.

Influence of Body Size on Turning Performance

Turning radius directly relates to the size of the animal. Data suggest that best hurling performance was by intermediate-sized dogs. Rotational inertia wasn't seen not to be the main limiter. Studies found that friction was quite important for turning along with the force limit. Turning involves lateral force production, with hind limbs potentially more important for lateral force production and forelimbs better at generating lateral impulse.

Combined Turning and Jump Landing

Turning and jump landing puts dogs at a unique advantage. A research experiment recorded kinematic data and kinetic data of advanced and beginner dogs. Advanced dogs have higher turning angle. Measurements were taken with reflective markered dogs in 3D with force plates. They had multiple cameras placed surrounding each marked dog.

Greyhound Racing

Injuries were directly related to decreased radium tracks. Change from grass to sand increased track safety. Increased banking aided in reducing force. One factor was that conditions were directly tied to injury rate.

Agility

Agility related information was generally obtained from surveys. Survey results include breed, prior injuries, and experience. Injuries in this topic are difficult to associate due to jump landing, turning, etc. Additional factors are based on collinding instead from forced based injuries such as falls. There are injuries that have been seen in this topic such as shoulders, etc.

Horse Racing

There's a lot of literature on the topic of horse racing injuries. Examples include tendon and ligament injuries and even catastrophic injuries. Variables that affect the horses are the speed, limb loading, and hyperextension.

Flyball

Flyball PhD project focused on:

Box angle (degree of impact of box)
Padding of box
Material placed

Research looked into the different box angles to see which was best (45-55 having greater risk).

Turn direction was also looked into from this topic. Dogs typically run in one direction due to comfort when acquiring the ball.

$Ethical$ concerns arise when looking for bandaging studies due to requiring injuries to compare and test with.

Impact of Ground Surface Interface

Researchers have looked at the ground interface surface (Rebecca parks and Tom Vitter. A review article was formed regarding effects of limb damping, vibrations, etc. Vibration is reduced as the frequency goes up the limb. Different surfaces deform at different lengths leading to difference in shock absorbing capacity. Researchers found issues of force to grip between the handlers.

Factors Affecting Locomotion and Performance

Factors that affect locomotion, especially at faster speeds, determine the limits to how fast animals can move. These factors directly influence athletic performance, where animals are often pushed to run faster, jump higher, or complete courses more quickly. Understanding these limits is crucial for optimizing training and preventing injuries.

Different limits to performance exist, including:

Conformation of the Animal: An animal's physical structure and conformation significantly limit its performance. Conformation includes skeletal structure, muscle attachments, and overall body proportions, and it is not easily changed except over generations through selective breeding programs. An animal's conformation is largely fixed at maturity, making it a primary constraint on athletic potential.
Gait: An animal's gait, or style of movement, is more dynamic and can potentially be altered with training. Gait adaptations can improve efficiency and speed, but they are also subject to biomechanical constraints.

Factors Affecting Gait

Stride Length: The distance covered in one stride; longer strides typically result in higher speeds, but excessively long strides can compromise stability and increase energy expenditure.
Stride Frequency: The number of strides taken per unit of time; higher stride frequencies can increase speed, but they must be coordinated with stride length to optimize performance.

Turning Locomotion

Turning is a fundamental aspect of locomotion, present in various activities, including sports and everyday movements. The lecture focuses on high-speed turning and its relation to injury risk. While biomechanics can measure limb forces and joint angles with sophisticated equipment (e.g., force plates, motion capture systems), linking these measures to injury prevalence (often gathered through questionnaires) is challenging due to the multifactorial nature of injuries. An example of this is the study of box angles in canine flyball.

A PhD study examined box angles in canine flyball, a sport that requires dogs to turn sharply and quickly.
Fly ball involves dogs running to hit a box and return, emphasizing the importance of turning speed and agility.
Competitors adjust the box angle (vertical or shallow) to optimize their dog's performance.
The study measured force but found no significant effect of box angle on limb force, failing to clearly link box angle to injury. This suggests that other factors, such as individual dog characteristics or training methods, may play a more significant role in injury risk.

Papers on Turning Locomotion

Two papers that discuss turning locomotion include:

"Turning Performance and Forelimb Loading in Polo Ponies and Racehorses" by Tan et al. (2010)
"Limitations to Maximum Speed During Cornering in Cheetahs" by Wilson et al. (2013)

Both papers utilize similar methodologies and technologies to measure turning, with overlapping authorship, indicating a collaborative effort in studying animal locomotion.

Video Analysis of Dogs Turning

Limits to Turning Performance

Two primary factors limit turning performance in quadrupeds and humans:

Grip:
- The ability to maintain traction and prevent legs from sliding is crucial for effective turning.
- Higher speeds and tighter turns increase the risk of slipping, requiring greater grip strength and stability.
Limb Force:
- Turning causes the ground reaction force to misalign with the center of mass, increasing limb force compared to straight-line running.
- This increased force can approach the limit the limb can withstand without breaking, causing the animal to slow down to prevent injury.

Additional Limits to Turning Performance in Dogs

A study proposed additional factors limiting turning performance:

Toppling Avoidance:
- Toppling can occur due to a lack of grip, resulting in a loss of balance.
- Body weight should be less than the medial ground reaction force to avoid toppling, ensuring stability during turns.
Rotation of the Body:
- The ability to change heading angle effectively is critical for executing turns efficiently.
- Factors like weight of the head, stride length, and body length can affect this, influencing the animal's turning radius and agility.
- Stride length and body length also affects the ability to rotate, with shorter strides and bodies facilitating quicker turns.
- $Smaller$ animals outmaneuver big dogs when they're all running around due to shorter leg length, which allows them to make tighter turns.

Smaller animals can bring their center of mass closer to the ground leading to increased stability due to shorter leg lengths and a more crouched posture. Body length affects maneuverability. Shorter bodies are generally more agile and can change direction more rapidly.

Ground Reaction Force

During turning, the ground reaction force often does not align with the center of mass, leading to higher limb forces in animals. This misalignment requires the animal to exert additional effort to maintain balance and control.

Coefficient of friction measures grip between two surfaces; typically measured between 0 and 1, can exceed 1 in biological contexts due to claws providing additional grip. Cheetahs have a coefficient of friction around $1.3$ , horses around $1.06$ , and dogs around $1.1$ . Claws and specialized paw structures enhance grip, allowing animals to achieve coefficients of friction greater than 1.

$Coefficient$ of friction is measured between zero and one, representing the ratio of frictional force to normal force.
$Cheetahs$ have a curve of friction usually of about 1.3, reflecting their exceptional ability to grip the ground at high speeds.
$Horses$ are about 1.06, indicating a good but lesser grip compared to cheetahs.
$Dogs$ there was a study where they were about 1.1 something, showing that they have better grip than horses but not as good as cheetahs.

Natural surfaces generally provide more grip than synthetic surfaces, due to irregularities and textures that increase friction. Measuring grip in animals is challenging due to ethical concerns, often requiring the use of cadaver limbs or sophisticated biomechanical models.

Analysis of Turning Performance in Horses

The Tan and Wilson paper utilized GPS-IMU units to collect data from racehorses and polo ponies, measuring speed and turning radius of the horses. These measurements provide insights into the biomechanics of turning and the limits of performance. The equation for the grip limit:

$Grip Limit = Coefficient ewline of ewline Friction * Normal ewline Force$

The equation for the limb force limit:

$Limb ewline Force ewline Limit = Maximum ewline Limb ewline Force ewline the ewline Limb ewline Can ewline Withstand$

The collected data was plotted on a graph with mathematically calculated force and grip limits to assess whether the biological data aligned with these theoretical limits. This analysis helps to determine whether animals are more limited by grip or limb force during turning. Racehorses did not reach the grip limit but approached the force limit, while polo ponies came close to both limits but closer to the grip limit.

Implications of the Horse Data

Polo ponies are probably more limited by grip than racehorses, due to the tight turns and quick maneuvers required in polo.
Racehorses are probably more limited by the force limit, as they maintain higher speeds on broader bends, increasing the stress on their limbs.

Dog Turning Data

Influence of Body Size on Turning Performance

Turning radius directly relates to the size of the animal. Smaller animals can achieve tighter turning radii, enhancing their maneuverability. Data suggest that best hurling performance was by intermediate-sized dogs. Rotational inertia wasn't seen not to be the main limiter. Studies found that friction was quite important for turning along with the force limit. Turning involves lateral force production, with hind limbs potentially more important for lateral force production and forelimbs better at generating lateral impulse.

Combined Turning and Jump Landing

Turning and jump landing puts dogs at a unique advantage. This combination requires precise coordination and control to maintain balance and avoid injury. A research experiment recorded kinematic data and kinetic data of advanced and beginner dogs. Advanced dogs have higher turning angle, indicating greater skill and control. Measurements were taken with reflective markered dogs in 3D with force plates. They had multiple cameras placed surrounding each marked dog, capturing detailed movement data.

Greyhound Racing

Injuries were directly related to decreased radium tracks. Shorter radii increase the forces experienced during turning, elevating the risk of injury. Change from grass to sand increased track safety. Sand provides better cushioning and reduces the impact on the limbs. Increased banking aided in reducing force. Banking helps to counteract centrifugal forces, improving safety and performance. One factor was that conditions were directly tied to injury rate. Weather conditions and track maintenance significantly influence the risk of injury.

Agility

Agility related information was generally obtained from surveys. Survey results include breed, prior injuries, and experience. Surveys provide valuable data on the prevalence and types of injuries in agility dogs. Injuries in this topic are difficult to associate due to jump landing, turning, etc. The combination of different movements makes it challenging to identify specific causes of injury. Additional factors are based on collinding instead from forced based injuries such as falls. Collisions with obstacles or other dogs can also lead to injuries. There are injuries that have been seen in this topic such as shoulders, etc. Common injuries include shoulder strains, sprains, and dislocations.

Horse Racing

There's a lot of literature on the topic of horse racing injuries. Examples include tendon and ligament injuries and even catastrophic injuries. Horse racing is associated with a high risk of musculoskeletal injuries. Variables that affect the horses are the speed, limb loading, and hyperextension. High speeds and extreme limb movements contribute to the risk of injury.

Flyball

Flyball PhD project focused on:

Box angle (degree of impact of box)
Padding of box
Material placed

Research looked into the different box angles to see which was best (45-55 having greater risk). Steeper angles increase the impact force on the dog's limbs.

Turn direction was also looked into from this topic. Dogs typically run in one direction due to comfort when acquiring the ball. Preference for one direction over the other can lead to overuse injuries on one side of the body.

$Ethical$ concerns arise when looking for bandaging studies due to requiring injuries to compare and test with. It is challenging to conduct research on injury prevention methods without causing harm to the animals.