Why they've has chosen specific heights

Having received many queries on how and why they chose their four jump heights UK Agilty has chosen to answer these questions in an open article to all agility people via the agility media.

To address the speculation about UK Agility copying other international organisations (mainly USDAA) we would like to state that the only jump height we share is the 12" division. We do not know of any other organisation in the world that offers the same jump heights as us.

First, keeping in mind that one of UK Agility’s major aims is to cater for as many competitors and dogs as possible, we chose the following height divisions:-

Dogs Measuring

Jump Height

12 inches and below

12" (305mm)

16 inches and below

15" (381mm)

20 inches and below

24" (610mm)

Over 20 inches

30" (686mm)

UK Agility does, however, give the handler the choice of jumping the dog higher than the jump height their dog is eligible for.

Second, it was important to us that we did not force equipment suppliers and the private individual to have to revamp their equipment to meet new jump heights. Therefore, when creating the new height divisions, we kept in mind the current available equipment specifications. One manufacturer has told us that cost to change their hire equipment to different jump heights such as USDAA would be in the region of £8,500 and the cost to clubs around £12 per jump.

Why pick these heights?
One of the most discriminated groups of dogs in British agility has been the smaller breeds. UK Agility wanted to create a more evenly distributed group of smaller dogs to increase the level of competition and fun.

Our 12" jump height was designed with the smaller mini dogs in mind (toys, etc.) We wanted to create a division that would enable dogs that size, a category which would allow them to compete under conditions suited for them so that they may show their true abilities, thus increasing the standard and diversity of breeds at this height in the UK.

The idea of the 15" class is to again encourage and increase the standard of dog at this height. While we were in the planning stages, gathering data and observing results of agility shows, we also noticed that many Midi classes were small in number and were perhaps, a slightly lower level than the standard dogs.

We also observed a trend, of Border Collies, measuring under 17", entering these classes. By removing the 16-17" dogs from this division, we felt that we would prevent the Border Collie from dominating this division and again encourage people to stick with their original breeds. We were also hoping to establish a division that would give dogs measuring 15-16" - as so many of the shelties, poodles and smaller mixed breeds do - a fairer but also more competitive competing environment.

The 24" division was developed for a couple of reasons. One was to split the collies into 2 groups of larger and smaller. The other reason was to encourage other breeds and mixed breeds that struggle to jump 30" due to height and structure, measuring 20 inches and under, into the sport. The reason for the 24" jump height for this division of dog was that we felt that the other jump heights such as 20 inches, was too low for a 20" dog to jump, while a 26" jump height was too high for 16" dogs to jump. Once again, there was the fact that other jump heights would require equipment modification in Britain.

Safety first
The 30" height division was maintained firstly due to the fact that it is the essence of British Agility. Although, more importantly, 30" was kept because research as well as our own observation has shown that jumping higher is not only safer, but influences a better jump style and form.

Unfortunately, not much effort has been put into the proper research on agility dogs and jumping. In addition, some of the research done is not as scientific as would be liked. One piece of research coming from the Netherlands studied how jump height affects injuries in dogs. It concluded that speed, not height, is more likely to cause injury. It has also been concluded that the lower a dog jumps, the faster the dog will go. The faster the dog travels, the more impact is caused when turning and hitting the other equipment. As said though, it’s been suggested that this is not as scientific as it could have been.

Jumping Dogs
Mitch
Amanda Pigg's Jag
Sing

Rocket science
Wanting to get the best information available, we spoke to a Professor of Physics at the University of Washington, Prof. John G. Cramer who further explained the relationship between an object’s impact at speed versus height. This is what he said.

Let us assume that the chance of injury to a dog depends directly on the amount of energy involved in the execution of a particular obstacle.

The energy involved in a particular jump height is the gravitational energy or E1 = m g h , where m is the mass of the dog, g = 9.8 m/s2 is the acceleration due to gravity, and h is the distance that the dog’s center of mass rises when going over the jump. The energy E1 is both the amount of energy that the dog’s muscles must generate in jumping, and the amount of energy that the dog’s body has to absorb in landing. Because E1 is directly proportional to h, the jump height and energy grow at the same rate. For example, if the jump height is increased by 40%, the gravitational energy E1 is also increased by 40%.

The energy involved in the speed of the dog is the kinetic energy or E2 = (1/2) m v2 , where m is the mass and v the speed of the dog. The energy E2 is both the amount of energy that the dog’s muscles have to generate to run at that speed, and the amount of energy that the dog’s body has to absorb in stopping. Because E2 is proportional to v2, the kinetic energy E2 grows faster than the dog’s speed. For example, if the dog’s speed increases by 40%, the kinetic energy E2 increases by a factor of 2.

Thus, it appears that changes in jump height are less likely to cause injury than comparable changes in the speed of the dog.


Sue Rolfe & Kes

Now not being physicist’s we tried to put this into laymen’s terms and asked him if this was correct.

From this it is apparent that as jump height increases by 40%, impact increases by 40% but as the dogs speed increases by 40% the impact increases by 100%. While watching and running dogs at lower heights it is clear that they go faster and, therefore, lowering the jump heights for many of our dogs is likely to cause more impact injuries.

The answer to this question was 'Yes, basic physics tell us this is correct.'

More Jumping Dogs

Cosmic

Holly

Fen

In our experience
Greg and Laura Derrett from UK Agility have had a lot of experience in working and training in many other countries where dogs jump at lower jump heights. Both have come to the conclusion that jumping lower affects the jump style of dogs in a negative way. Dogs often flatten out over the jumps with a noticeable higher knocked pole rate because of the lack of effort it takes to get over the lower jumps. Thus less effort is put into the jump style. It is also evident that many of these dogs have a very poor jump apex causing them to take off in the wrong place for the jumps, often smashing into the poles. When you speak to people who are experts in jump style, they will tell you how important correct body form is to prevent injury and this decrease in style will unfortunately increase injury.

Many handlers in countries where we have worked have now begun to train their dogs at 30" even though their competition jump heights are 22", 24" or 26". This seems to have had a considerable affect on the dogs consistency as well as jump style.

In addition, some of these countries are constantly working on trying to correct poor jump style in their dogs with lots of work spent on jumping style and a increasing demand for training days from ‘jumping experts’ from the horse jumping world. Back end awareness, jump shoots, cavaletti work, ground bars and jump apex is something all agility competitors would start to have to understand if we brought in a lower height.

Another observation noted from the countries that jump at lower heights is the tendency for the herding breeds to have more ACL (anterior cruciate ligament) injuries and surgeries. Unfortunately, this again is purely observational with no research to back this claim up but there is a large number of dogs we know abroad with this particular injury in comparison to only a few seen in British Agility.

Whatever the competitor’s opinion is on what is a safe height for their dog to jump, we have tried to give them the options to jump both higher and lower. If they feel higher is safer, they have that option available to them. If they feel the lower heights are safer for that particular dog, they are still able to have two runs a day in the Casual classes where they can choose any height.

With all this information it was still important to make sure that those competing at 30" were happy to do so. From discussions with competitors over the years along with Jim Gregson’s knowledge of agility competitor’s thoughts obtained from his work for the Kennel Club Agility Liaison Council and from articles written on the subject, the majority of competitors seemed more than happy with the 30" jump height.

Again from experience in the UK Agility team it may also be an advantage to the British international competitor to jump higher in Britain and then jump lower in international events. Jo, Nikki and Toni certainly proved that in 2003 and Greg did get the Silver this year. The 30" jump height is certainly keeping us competitive on an international front.

In conclusion
Now we are happy to admit that the reason for sticking to 30" is not a ‘proven fact’ that it is better and safer, but everything we could find on jump heights led us to the conclusion that there was no evidence to change from the 30" jump height while on the other hand there seems to be a lot of reasons to keep it. If future research were to conclude that alternative jump heights would be safer, then UK Agility would seriously review it’s current perspective.

With the information UK Agility currently has to go by, it is clear that we may have caused a lot of problems bringing in lower heights. Bringing these new problems in to British agility was something the British Agility competitor would probably not thank us for!

From Greg Fontaine (Asheville, NC USA)...
I think it’s great that people are attempting to analyze more scientifically what our dogs might be experiencing while playing agility. I am NOT a physicist; I quickly get lost over my head in this stuff. A bio mechanist I used to work with referred me to a website with various models that can be used in pre-college math and science classes. (These days, even pre-college math and science materials can often leave me bewildered.)

A relevant model for this discussion involved a comparison of two different types of ski jumping events. Nordic jumping stresses distance travelled.

Aerial freestyle jumping stresses height attained (higher heights mean greater air time allowing more time for spins, twists, etc). The model analyzed landing impact forces for the two different types of jumping events. You can read the details at: http://pumas.jpl.nasa.gov/PDF_Examples/05_10_99_1.pdf.

In the ski jumping examples, the flatter trajectory of the Nordic jumper resulted in less impact force; the rounder trajectory of the Aerial freestyle jumper resulted in more impact force. Admittedly, dog agility is not ski jumping. However, the model and its discussion are just one example suggesting that in analyzing impact forces from landing different trajectories, there would appear to be much more to the question than merely calculating the energy involved executing the jump.

It seems perhaps even more important to consider how that energy is absorbed or deflected as the jumper returns to the ground. Angle of descent relative to the ground would seem to be one factor. Add to that, the question of whether the jumper’s horizontal velocity will be allowed to continue forward or instead be expected to turn sharply upon landing. A higher trajectory might mean less horizontal velocity, which would be beneficial in preparing for a turn. Then again, it seems counterintuitive to expect dogs (and humans) preparing to turn to typically resort to jumping higher and higher in order to lessen horizontal velocity; instead I would expect a tendency to shorten stride. That logic would suggest that jumping higher and higher might not be the most effective strategy for dissipating landing impact.

Anyhow, I look forward to the possibility of more input from those with greater physics intellect and practical knowledge than I can apply to such questions.

In any event, whatever the jump heights, best wishes to UKAgility ! (18/01/05)

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