A VET'S OPINION ON JUMP HEIGHT

Agility Australia, Oct 29 2001

Just some more interesting considerations about jump heights. Firstly, I want to say I am very much in favour of LOWER jump heights, but I think it is worth while discussing the article that Terry referred us to.

Terry referred us to an interesting article that quoted a vet's theory about the effect of LOADS IN AGILITY, with reference, in this case, to jump heights and the likelihood of injuries:
<<I also found this article as well. Might raise a few eyebrows concerning low height jumps: http://www.agilitynet.com/magazine/health/jumpingheightinagility.shtml>>

The article on a UK website that Terry refers to, actually discusses an original article written by a Dutch vet who studies biomechanics. In the past, I have referred to the original article, probably when we were talking about jump heights with the rule reviews happening. For those interested in the original article there is a link on this website's links page (article on joint stress)

Mind you, I have not tried to find it lately, so it may not be there still.

I will try to make a brief, and very simplistic summary of the original article.

When a dog lands, he must absorb the kinetic energy produced. (This happens whenever a moving object is stopped). In a simple straight line jump, this kinetic energy has 2 components - vertical (up and down) and horizontal (from forward propulsion)

The section on jump heights explained that, to jump higher heights, a lot of dogs make a steeper take-off and landing (dog takes off closer to the jump, and lands closer to the jump). So, although they do have to absorb more "vertical kinetic energy", because the take-off and landing is steeper they have less horizontal energy to absorb.

With lower jump heights, the dogs tend to jump longer and flatter - there is less vertical energy to absorb but, because the dog takes off earlier and takes a longer jump, there is much, much, much more horizontal energy to absorb.

The writer, therefore believes that it is better to use higher jump heights.

THE FOLLOWING IS MY PERSONAL OPINION

1. This theory does not take into account the dog the continues to take jumps in a rounded arc even at very high heights. All my dogs will continue to use a rounded arc, (taking off proportionally further away from the jump and landing proportionally further) as the jump height increases. This means that when you increase the jump heights for these dogs, you are increasing both vertical and horizontal stresses. Obviously increasing jump heights dramatically increases the stresses and strains on the ligaments, tendons and joints of dogs of this jumping style.

2. I believe that the canine body is better designed to absorb the horizontal kinetic energy. After all, the main stresses and strains on dogs, as they evolved is a full gallop on flat land - obviously the dog's body must be well designed to absorb these forces. Although I am sure that the wild dog did some jumping, mother nature never designed him to absorb repetitive shock absorption
from jumping.


The original article is well worth the read. It brings up a lot of useful discussion on a number of issues. One, in particular that I am strongly in favour of is getting rid of the slats on dog walks and A-frames. A lot of food for thought, although, like any similar article, it should be considered carefully, and not always considered as the whole truth - try to look at it from several perspectives.

Le Hammer BVSc