Peak forelimb ground reaction forces experienced by dogs jumping from a simulated car boot

Effects of jump height on forelimb landing forces in border collies

Objective

The objective of this study was to evaluate the effects of jump height on the landing forces of dogs.

Animals

Client-owned Border Collies experienced in agility competition, n = 9.

Procedures

The study involved client owned border collies with the same AKC standard jump height of 20 inches and preferred height of 16 inches. Standard height is based upon the height of the dog at the withers, with preferred height referred to as reduction in jump height by one level due to injury or age. An AKC regulation bar jump was placed over a previously validated pressure sensitive walkway (PSW). The peak force (%BW) and peak contact pressure (kPa) of the leading and trailing forelimbs were evaluated for all dogs.

Results

There was no significant difference in landing force between the two jump heights for either peak force as a percentage of body weight or peak contact pressure when evaluated in both leading and trailing forelimbs.

Conclusions and clinical relevance

Our findings demonstrated no significant difference in active landing forces of peak contact pressure and peak force on the forelimbs of dogs when jumping at a standard jump height vs. a preferred jump height when controlling for velocity in dogs performing a single running bar jump. These results suggest that the recommendation of decreasing jump height for older animals or injured animals may not provide a significant decrease in the impact on the forelimbs. It is likely that other factors contribute to the total forelimb kinematics picture during competition. Veterinarians and trainers should consider additional ways to decrease impact for canine athletes as they recover from injury.

Understanding the Impact of Scale Height on the Kinetics and Kinematics of Dogs in Working Trials

Working trials is a canine discipline that originated from police and military dog work. One aspect of working trials competition is for a dog to “scale” a 6ft high wooden wall. Concern has been raised in other canine disciplines that landing forces after traversing jumps may lead to soft tissue injuries. There is a paucity of research into the impact of scale height on peak vertical landing force (PVF) in dogs participating in working trials. The aim of this work was to determine whether an alteration in scale height impacts PVF and apparent joint angulation on landing. Twenty-one dogs who regularly competed in working trials traversed the scale at three different heights; 6ft (full height), 5.5ft and 5ft. Changes in PVF, apparent carpal and shoulder joint angulation and duration of landing were analyzed using general linear mixed models. Dogs weighing >25 kg had greater PVF at 6ft than at 5ft (p < 0.05). There was no effect of scale height on PVF in dogs <25kg. Duration of landing was longer at 5ft than 5.5ft (p < 0.001) and 6ft (p < 0.001). Apparent carpus angle on landing was smaller at 6ft than 5ft (p < 0.05) and 5.5ft (p < 0.05) for dogs <25 kg. Apparent carpus angle on landing did not differ at any height for dogs >25 kg (p > 0.05). Apparent shoulder angle was not affected by scale height for any dogs (p > 0.05). There was considerable variation in the study population, but this research indicates that when the scale height was lowered to 5.5ft dogs had reduced PVF and less compressed joint angles on landing. When the scale height was lowered to 5ft they altered their traversing style and greater compression and increased PVF was seen. Evidence-based approaches to canine working trials are important to ensure minimum impacts on physical health and welfare of participating dogs, in terms of risk of injury in both competition and training. Based on these findings it is recommended that the maximum height of the scale is reviewed for training and competitive purposes, to ensure minimal impacts on the health of competing dogs, while maintaining the level of competitive challenge.

Kinematics and kinetics of dogs completing jump and A-frame exercises

Many police dogs do not reach their expected retirement age as they are no longer able to cope with the physical demands of the job. Annual licensing requires police dogs to complete a series of agility tasks, including jumping and negotiating an A-frame obstacle, both of which are associated with higher injury rates in canine agility competitors. This study sought to measure conformational, kinematic, and kinetic parameters of actively employed police German Shepherd Dogs (GSDs), whilst completing a 55 cm jump hurdle, and a standard A-frame. Each dog completed three repetitions of each obstacle and was also recorded at both walk and trot. Contact pressures and forces were measured, whilst joint kinematics were recorded using reflective markers and a high-speed camera. Results found that static hip angle was significantly correlated with hip flexion at trot, during jump suspension and at the apex of the A-frame. Stifle and hock flexion were greatest during the suspension phase of jump (56.98±11.710° and 54.51±17.430°). Shoulder and elbow flexion were greatest at the apex of A-frame (104.34±16.744° and 75.72±20.804°), whilst carpal extension was highest upon landing from the jump (125.77±7.071°). Peak vertical force (PFz) when normalised for body mass (BM) increased when landing from A-frame (14.28 N/kg BM) as opposed to landing from the jump obstacle (12.055 N/kg·BM). Our results show that increased range of motion (ROM) is required during both jumping and negotiation of A-frame compared to walk and trot, but more significantly, greater forces are incurred upon landing from the A-frame than compared to jumping. It was also observed that dogs were subject to high degrees of torsion in the distal limbs upon landing from the A-frame due to trained behaviours. We conclude that use of agility equipment generates greater forces through the musculoskeletal system and requires a greater ROM than what is experienced at walk and trot, which may contribute to early retirement ages in police dogs.