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The Effects of Jumping on Forelimb Injuries
by Unknown Author
Copyright June, 2004 -
When jumping over obstacles, dogs land with significant force applied to their forelimbs. If this is an infrequent event, then the impact is usually of little concern, but repetitive jumping over many years may have significant consequences. Repeated impact loading has been documented to cause some overuse injuries in human athletes. The effects of jumping on chronic injuries in dogs has not been studied extensively. Forelimb injuries such as biceps tendinitis and carpal hyperextension (severe wrist sprain) seem to occur more frequently in dogs that do a lot of jumping. Chronic, repetitive forms of trauma, including jumping, have been linked to another type of shoulder injury in dogs termed mineralization of the supraspinatus tendon. Both the frequency of jumping and the height jumped may play a role in these injuries.
There
is some concern among certain breed clubs that jump heights used
in obedience competition may contribute to long term orthopedic
trauma in dogs. A jump height standard of 1 1/4 times the dog's
height at the withers is commonly used in competition. One potential
problem with using a jump height standard based solely on the dog's
height is that it does not take into effect the body weight or body
conformation of the different breeds. In their recently published
book, Jumping From A to Z, Zink and Daniels discuss "weight:height
ratio" as a more accurate way of determining the risk of jumping.
Dogs with a ratio of greater than 4 (when using weight in pounds
and height in inches) are considered in the "danger zone"
for jumping. They advised jumping at full height only when the footing
is excellent and the landing is soft. Further concern is stimulated
by the results of a scientific paper published in 1992 in Veterinary
and Comparative Orthopedics and Traumatology. In a study entitled
Measurements of Vertical Ground Reaction Force in Jumping Dogs,
the authors found that the forces increased significantly with increasing
height. Vertical ground reaction forces are considered to be an
accurate indication of the impact placed on the forelegs when a
dog jumps. Furthermore, the dog's body weight and breed also influenced
the vertical ground reaction forces. Statistical analysis of the
effect of weight on force shows that heavier dogs impact with greater
force at each jump height.
Factors
that may affect vertical ground reaction force were discussed by
the authors and these included conformation, jumping style, degree
of training and physical conditioning. Dogs with less angulation
in the limbs and straighter conformation were thought to land with
greater forces. It was also mentioned that well-trained dogs appear
to jump and land more smoothly ("good style") than the
stiff-legged landing of untrained dogs. Good physical conditioning
may enable a dog to more actively control joint motion. In fact,
properly timed and executed muscle contractions may provide a shock
absorbing effect. Smooth landings allow the jumping dog to absorb
the impact over a longer period of time than stiff landings, in
which the jarring impact results in higher vertical ground reaction
forces.
If jumping contributes to the development of acute and chronic injuries in a significant number of dogs, should we be taking proactive steps to decrease these injuries? It is apparent that more investigation into the long-term effects of jumping is necessary. A number of veterinary schools have canine sports medicine programs that are equipped to evaluate these types of questions. On the competitor level, one simple step might be to lower the jumping height requirement for breeds whose conformation is not well suited to jumping. As long as the changes are consistent, this would have minimal impact on competitive events and may have a significant impact in reducing injuries.
This article originally appeared in the October 1996 issue of Canine Sports Medicine Update.
