The biomechanics of working dog locomotion II: Loaded trotting

There is a growing need for working dogs to carry equipment to facilitate or enhance the completion of tasks, and carrying these wearable devices often involves bearing substantial loads on or around their spines. However, the potential locomotory, physiological and/or behavioural effects of the shape and/or weight of these devices on working dog performance are unknown. This work aimed to investigate the absolute and relative impact of carrying various shapes and magnitude of load on functional performance in working dogs, including Labrador retrievers, shepherd breeds and spaniel breeds. Functional parameters were analysed from each dog during trotting whilst carrying loads that included bags (10% body mass) and a cylindrical tube (5% or 10% body mass). The impact of load type and mass appeared to be breed-specific, with shepherd breeds incurring the greatest impacts in terms of altered spatiotemporal parameters relative to unloaded trotting. Spaniel breeds showed less impact from both load conditions in spatiotemporal gait parameters, but larger differences in joint kinematics and moments relative to the unloaded condition. These data point to a lack of generalisability in the responses to load carrying, even between breeds of broadly similar body shapes, but tentatively suggest that spaniel breeds may perform better during trotting load-carrying tasks, although they may do so at a possible cost of increased muscle forces and joint loads. Further work incorporating measures of energetic expenditure and fatigue is needed to test these hypotheses.