The Influence of Three Working Harnesses on Thoracic Limb Kinematics and Stride Length at Walk in Assistance Dogs

Studies have investigated the kinematics of the healthy canine thoracic limb (TL), but there is currently no research to the authors’ knowledge investigating the influence of the working harness on TL kinematics. The aim of this study was to compare the TL stride length (SL) and shoulder, elbow and carpal joint range of movement (ROM) of assistance dogs when wearing three different harnesses (H1 and H2 Y-shaped harnesses; H3 the dog's original harness) with differing handle designs (A and B type handles; all dogs used an A type handle with H3, their original harness), in comparison to a standard collar at walk. Thirteen dogs were analyzed at walk in each condition: Harness 1, H1 (B-handle); Harness 2, H2 (A-handle); Harness 3, H3 (A-handle, and the dog's original working harness); and the Collar with the lead held between 20 and 40cm. A series of Friedman's analyses with post-hoc Wilcoxon Signed Rank tests compared SL and joint ROM at peak protraction and retraction of the TL. Results: The results show significant TL kinematic changes in H1 (B-handle): SL in H1 was significantly reduced in comparison to the Collar (6%; P = 0.008). In TL protraction, a significant reduction in shoulder extension was recorded for H1 in comparison to H3 (6%; P = 0.005). In TL retraction, a significant reduction in carpal extension was observed in H1 in comparison to the collar (4%; P = 0.008), H2 (2%; P = 0.005), and H3 (4%; P = 0.005). Conclusions: Differences in canine locomotion were observed between conditions in comparison to when the dog was at walk in the collar. Our findings suggest the harness handle type may result in the TL kinematic changes observed. Significant TL SL and ROM restrictions were noted in H1, the only harness in the study with a specific handle design (B-handle type). The increase in proximal TL joint ROM and a subsequent reduction in distal TL joint ROM suggests an alteration to the energy efficiency of locomotion when compared to previous literature. These results were seen only in H1 and not H2, a similar design of harness, therefore suggesting the B-handle type may be the key factor in the kinematic changes observed.