The case for a 4th (550mm) height
In preparation for making the case for a 4th height in 2013, a number of comparison videos were taken of “smaller Large” dogs jumping at 550mm and 650mm, with 4m and 5m spacing. These videos were offered to the KC’s Activities Health and Welfare Sub-Group to view, in conjunction with a PowerPoint presentation and a document that made further comparisons using stills of dogs at different phases in the jumping process.
Now, almost 2 years on, it seems appropriate to share some of these images with anyone that might be interested. The descriptions, in the document below, of what is happening when a dog jumps, will give the viewer an insight into what to look for in the video footage. Dogs that would fall into the proposed “4th height” category completed a simple sequence of a curved pipe tunnel, followed by three jumps in a straight line, set at 650mm and 550mm. This sequence was performed at 4m and 5m spacing (see document for further details).
The following is an extract from the document (updated November 2014):
- Take-off: propulsive power of the hind quarters
- Clearing the pole: length of leg versus work needed to lift centre of mass
- Landing: angulation of front assembly
- Force reduction: muscle, tendon & bone ability to absorb potential energy in the “spring system”
- Recovery: ability to return to running gait on landing
- Number of repetitions
- Results of the 2007 Survey of Injuries Occurring in Dogs Participating in Agility
It is not hard to understand why there is no definitive research into the health and welfare consequences for a dog that regularly participates in dog agility – it would probably take longer than a lifetime to test every variable at a level of statistical significance for every breed, type, sex and age of dog affected.
Many small studies have been undertaken on various aspects of our sport. Sometimes these inform practice but more often they inform a view as they are not broad enough to provide a solid base of evidence that would influence change. Every change we have seen in the sport has gone ahead without true evidence-based research – a great shame but it is the way our sport has evolved simply because the cost of such research would be prohibitive. If we had waited for research on our current jump heights, weave and surface changes then our sport would not be where it is now; we would probably still be waiting. Research is important and hopefully will in the future inform practice, but for true research to take place there are enormous ethical constraints.
What we can use now however, in its absence, is evidence-based practice and that is the position we are in today: simple, cost-effective solutions to reduce risk, use common sense and encourage appropriate, best practice training and deal with the obvious.
Where are the risk factors?
In the absence of any study broad enough to provide a solid base of evidence that would influence change, we have attempted to identify the obvious variables associated with hurdle jumping.
The photographs in this document look at take-off, flight, landing and return to running gait. The variable being looked at is dog height at withers.
Of course there are other areas of a less obvious nature to add to the list (Breed type, age, sex, experience, etc) and of course there are the external influences of handler expertise, training and environmental conditions. It is encouraging to think that research can and will be designed to evaluate the interactions and consequences of these influencers on a dog’s long term health and welfare, but the list of risk factors and variables is huge.
When a dog jumps, the rear assembly (hindquarters) provides the propulsion whilst the front assembly (shoulder, elbow, leg, etc) provides the degree of lift and absorbs much of the impact on landing. Regardless of breed or size, all dogs jump using the same sequence of movements.
Currently jump height categories are determined solely by the dog’s height at withers, regardless of height/weight ratio. The following comments are made with this in mind.
There follows a series of photographs of dogs in the suggested “4th height” range jumping hurdles at 550mm and 650mm.
All the dogs jumped at 550mm and then 650mm with 5m spacing. We then filmed the more experienced dogs doing a bounce grid on both heights, at 4m spacing (KC minimum is 3.6m). No dog was asked to do too many repetitions (usually two goes each) and in fact only had one go each at the bounce grid.
A record of each dog’s height, age, breed and experience is provided in the attachments.
1. Take-off: propulsive power of the hind quarters
As a dog approaches a jump, the front feet are placed, one slightly ahead of the other, at a take-off spot. This point is determined by a number of factors: speed, height of jump, weight:height ratio of dog, ground conditions, experience and confidence of the dog and dog’s general strength and well-being.
As the front feet are planted, the head is lowered and the front legs are slightly flexed.
The strong rear-end muscles ultimately provide the power and range for jumping, but the conformation and range of movement of the front legs are critical to getting the body over the hurdles.
Dogs that take off late or early, or fail to decelerate before turning or accelerate when jump spacing is inappropriate are at greater risk than those that are well schooled.
Courses that are poorly designed increase the chances of the above happening.
The higher the jump in proportion to the dog’s height, the greater the propulsive power required.
“Aoife” is 3 years old, Nova Scotia Duck Tolling Retriever. Grade 2. Approx 480mm at withers.
Jumps were spaced at 4m
Aoife was unable to takeoff for the 650mm jump (2nd pic) after landing. She ran underneath.
2. Clearing the pole: length of leg versus work needed to lift centre of mass
The spine is flexed as the rear legs are brought forward and planted slightly ahead of the front feet. The front legs are extended, pushing the front body upwards and raising the head to help with upward thrust.
The rear legs are then extended to propel the dog upward and forward. Once the dog is in the air, the head is lowered closer to the outstretched front legs to help with forward thrust and to reduce drag.
At the apex of the arc, the dog should lower his head and lift his tail to help rotate the body forward and downward.
Work needed to clear a pole is influenced by
- length of leg to body mass
- length of leg from the ground to the elbow as a percentage of the dog’s height at withers.
Different breeds of dog with different conformation will have a differing degree of challenge associated with clearing a pole.
“The shorter the breed and the dog, the lower will be the leg-length-to-height ratio. Think of most Toys, Cockers and Corgis, but also Brittanys and smaller dogs.” (Lanting, 2011)
“A dog whose legs are greater in length from the ground to the elbow as a percentage of the dog’s height at withers has the advantage of a higher centre of gravity. During jumping, the majority of the lengthening of the leg takes place above the elbow, with this joint acting as the fulcrum from which the leg extends. It is an advantage in jumping to have that height as high as possible in relation to the height of the jump”. (Zink, M.C. & Daniels, J, 2005)
“Look” is 20 months old, Grade 3, approx 460mm at withers. Jumps were spaced at 5m
Above (550mm) the degree of lift required is clearly less than below (650mm)
Note the extension of the neck and lifting of the head at 650mm
Point of takeoff and point of landing very similar, shape of trajectory slightly flatter at 550mm
Back to Contents
3. Landing: angulation of front assembly
“When the shoulder blade is more vertical [often referred to as upright or straight shoulders], three things happen. First, there is a reduction in the range over which the scapula-humoral joint [the joint between the shoulder blade and the upper arm] can extend. This reduces the amount by which the dog can stretch the front legs forward [reach] and results in a shortened step length. Second, upright shoulders reduce the ability of the front legs to absorb the weight of the dog’s body as the feet hit the ground, both when gaiting and jumping. This increases wear and tear on the shoulder and elbow joints, which absorb the majority of the impact during movement. Third, dogs with upright shoulders have less area available for the muscles that extend between the shoulder blade and the upper arm. This can reduce the strength of the forelimbs and thus affect performance. It is also important to note length of leg — short upper arms create similar problems to straight shoulders, by reducing the available muscle mass, which in turn reduces reach and shock absorbance.” (Zink, M.C. & Daniels, J, 1996).
“Blue” 9 years old, Grade 6, approx 440mm at withers. Jumps were spaced at 4m
Note the steepness of landing angle at 650mm, which in turn decreases the dog’s ability to run on easily.
“Caolmhe” 6 years old, Nova Scotia Duck Tolling Retriever, Grade 2 approx 480mm at withers
Jumps spaced at 5m
Although the photo on the right is slightly later in the landing phase, the angle of descent can be seen to be steeper, causing greater vertical impact on the shoulder assembly at 650mm
Back to Contents
4. Force reduction: muscle, tendon and bone ability to absorb potential energy in the “spring system”
Researchers at Brown University in Providence, Rhode Island (Brown University, 2011) have documented how muscles and tendons work in concert first to store and then to rid themselves of energy and heat. They found that tendons take on the role of shock absorbers at the time of impact. About a tenth of a second later, the fibrous bundles in skeletally connecting muscles, known as fascicles, absorb the remaining energy. The tendons’ role is crucial, the Brown researchers write in the journal Proceedings of the Royal Society B, because they help protect these fascicles against damage from the rapid burst of energy and power generated by the impact.
“Something has to take up the slack, and it falls to the tendon,” said Nicolai Konow, a postdoctoral researcher in the Department of Ecology and Evolutionary Biology at Brown and the lead author on the paper. “The good news is it’s elastic enough to do that.”
“We used to think that all of the motion of the body could be explained just from the action of muscle motors,” said Thomas Roberts, associate professor of biology in the Department of Ecology and Evolutionary Biology, who specializes in animal movement. “It is becoming increasingly apparent that springy tendons are a big part of what makes us go.”
This ” spring system” allows kinetic energy to be dissipated and absorbed. It’s influence needs to be factored in when attempting to calculate forces generated in landing from different heights
“Brie” 5 years old Kelpie, Grade 4, approx 480mm at withers
Landing from 550mm above, at 4m and 5m spacing Landing from 650mm below, at 4m and 5m spacing
5. Recovery: ability to return to running gait on landing
After the outstretched front legs have hit the ground with one leg slightly ahead of the other, the rear legs are drawn forward under the body to absorb some of the impact of landing and to continue with the forward running gait on landing.
If the dog is unable to return quickly to running gait (too steep an angle of landing, not enough forward momentum) then the impact on landing is not as easily dissipated and needs to be taken up by the dog’s legs, initially by its pads and ankle joints.
“Pounding. The scissoring of the rear leg helps absorb impact shock, but the front legs have a more difficult time. The front knee bends only backwards, so the front leg extended forward comes down straight at impact. We speculate that the front knee-elbow arrangement do not scissor at impact like the back leg, since body inertia into it would probably cause the front leg to collapse the dog into the ground. Therefore, the leg is held straight and ankle joints (plus pads on the dog) register the major shock.
However, if the forward angle of the leg is correct, given the stride, then the force of impact will be lessened. If the leg comes down too soon at too steep an angle, then the foot “pounds” into the ground, increasing the force of impact. And if the leg comes down at too shallow an angle, the dog will lose grip and skid.” (Oricom Technologies, 2004)
“Blue” Collie x, between 9 & 10 years old, Grade 6, approx 440mm at withers
Landing and returning to run above at 550mm, 5m spacing
Landing and returning to run below at 650mm, 5m spacing
Note the increased effort for reach and flying tail at 650mm below as dog rebalances on landing
6. Number of repetitions
There is no question that many breeds of dog are capable of jumping the highest jump height currently on offer at KC competition.
What we don’t know is the effect on dogs with less leg length / different conformations repeatedly jumping this height in competition, in training and over a number of years.
This would be a very lengthy study indeed.
Results of the 2007 Survey of Injuries Occurring in Dogs Participating in Agility
In 2007, data was collected from 1,669 handlers of 3,801 agility dogs from 27 countries. This data was reanalysed over several years and used to provide an insight into 2 questions
What are the risk factors for agility-related injuries?
Variables evaluated included: demographics; frequency of practice and competition; use of warm-up, cool-down, and conditioning exercises; “alternative therapy” treatments (acupuncture,massage, chiropractic); breed; and dietary supplements.
A multivariable logistic regression analysis allowed each potential risk factor to be considered independently of all other factors.
Results showed that 32% of dogs sustained at least 1 injury during agility, with 1602 injuries reported in total. Dogs in the study were made up of 162 different breeds.
Question 1 -Variables Associated With Increased Risk Of Injury:
- Previous injury – after controlling for all other variables, dogs with a previous agility injury were 100 times more likely to sustain another injury.
- Border Collies – this breed is more prevalent in agility than any other breed. In this study, 16.8% of all dogs were Border Collies. These dogs are known for their athletic stamina and willingness to perform tasks, and this may allow handlers to work with Border Collies for longer durations during competition and practice than with other breeds. When controlling for all variables (including percentage of Border Collies studied), these dogs still had 1.7 times the odds of injury compared with other breeds. The authors postulated that this may be due to reasons like: the speed at which Border Collies navigate an agility course and high drive, speed and quickness at changing direction.
- Experience – there was an increased risk of injury in dogs with less than four years experience. The authors related this finding to improved skills in dogs, with increasing accuracy and speed as well as better decision making. Also, the odds of injury were reduced if the handler had more than five years of experience. In this study, amount of practice per week and number of competitions per month were not significant factors.
- Use of alternative therapies (acupuncture, massage, chiropractic) – the authors discussed that these therapies were likely implemented after a dog had sustained an initial injury, and because previous injury was a high indicator of future injury, dogs receiving these therapies were more likely to sustain injury.
- There was no relationship found between the use of warm-up and cool-down exercises and injury.
- There were no significant differences with use of dietary supplements.
- There were no significant differences between countries.
Question 2 – Can we characterize agility injuries on the basis of type, severity, and affected body part. (same 1,669 handlers of 3,801 agility dogs worldwide.)
Results of this study were consistent with previous studies indicating that approximately one-third of dogs participating in the sport sustain an injury. Soft tissue injuries (strains, sprains and contusions) to the shoulder, back, phalanges and neck are the most common types and sites of injury.
Almost 42% of the injuries in this study were attributed to interaction with 3 specific pieces of equipment: bar jumps (16%), A-frame (14%), and dog walks (11%).
Dogs typically perform many more jumps on a given course compared with A-frames and dog walks. In general, for a course containing 20 obstacles, 13 of these were bar jumps, with only 1 A-frame and 1 dog walk. Given the exposure to bar jumps, it is not surprising that many injuries were attributed to contact with this obstacle. It is possible that injuries associated with a particular obstacle may be in part related to the previous obstacle as it may influence the speed and direction that dog approaches.
The authors state “The fact that many injuries were attributed to interactions with A-frame or dog walk obstacles was disconcerting, considering the lower degree of exposure to these obstacles in typical competition courses.” They also found that a higher than expected number of shoulder and phalanges were injured during the A-frame. Shoulder, elbow, stifle and carpal injuries were most frequently reported with bar jump injuries. Contact with or a fall from the dog walk most often caused ribcage and head injuries, as well as abrasions. 27% of injuries had a non-specific cause, and the authors postulate that handlers are not always able to identify early signs of injury or lameness.
Cullen KL, Dickey JP, Bent LR, Thomason JJ, Moëns NMM. Survey-based Analysis of Risk Factors for Injury Among Dogs Participating in Agility Training and Competition Events. JAVMA, Vol 243, No. 7, October 1, 2013
(Summaries taken from a review published in Canada in 2014 by Carrie Smith, BScPT, CAFCI, CCRT and published by Four Leg Rehabilitation
Brown University (2011, September 28). Tendons absorb shocks muscles won’t handle. ScienceDaily. Retrieved January 27, 2013, from http://www.sciencedaily.com /releases/2011/09/110927211818.htm.
Lanting, F. (2011). A Matter of Proportion. Proportions, Leg-Length Ratios and Breed Standards: Using the Vizsla and the German Shepherd Dog as Examples. Retrieved January 27, 2013, from http://siriusdog.com/breed-standard-leg-length-ratios-vizsla-gsd.htm.
Oricom Technologies (2004). Leg mechanics. Retrieved January 27, 2013, from www.oricomtech.com/projects/leg-mech.htm.
Zink, M.C. & Daniels, J. (1996). Jumping from A to Z. Ellicott City, MD: Canine Sports Productions.
Dog information relating to the Photographs and Videos included here from Photo Session held on Saturday 26th January 2013 (details of dogs, ages and grades correct as at January 2013).
- Aoife, Toller age 3, Grade 2, approx height at withers 480mm.
Normally competes at 550mm
- Blue, Collie type, aged between 9-10 years, Grade 6, height 440mm.
Normally competes at 550mm.
- Look, Border Collie, aged 20 months, Grade 3, height approx 460mm.
Trains over 650mm and 550mm.
- Caoimhe, Toller aged 6 years, Grade 2, height approx 480mm.
Normally competes up to 550mm.
- Brie, Kelpie, aged 5 years, Grade 4, height 480mm.
Used to jumping 650mm and 550mm.
- Lace, Border Collie, age 6 years, Grade 6, height 460mm. Competes at 650mm and 550mm.
- Spice, Border Collie, age 20 months, Grade 3, height 470mm. Training over 650mm and 550mm
- Guiness, Springer Spaniel, age 7 years, Grade N/A at KC, height 450mm. Normally competes up to 550mm.