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

Abstract

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.