The effect of body condition score on peak ground reaction forces in walking dogs

Introduction: Obesity is the most common nutritional disease of dogs, and is estimated to affect a quarter of the canine population (1). It is well documented that weight may be a risk factor in the development of a number of common canine orthopaedic conditions including osteoarthritis (1). However, few studies have addressed the relationship between body condition score (BCS) in healthy dogs and ground reaction forces (GRF). The aim of this study was to assess the effect of BCS on weight normalised peak GRF (N/kg) in dogs at the walk. Methods: A sample population of n = 17 medium and large breed dogs of varying age (mean 5.30 ± 4.16 years) and a range of BCS (mean 3.06 ± 1.14) were recruited for this study. Dogs were body condition scored by an experienced person using PFMA guidelines. Dogs were placed in weight categories (underweight, ideal, overweight) based on how their weight differed from the recommended range for their breed. Dogs were lead on a loose lead at a consistent velocity over a single AMTI force plate at a walk to capture ground reaction forces (Fx, Fy and Fz). Twelve valid trials were recorded for each dog (valid trials required a single limb to contact the plate at one time). Spearman’s correlations were used to test for a relationship between BCS and GRF and a Kruskal-Wallis and post-hoc with Bonferroni adjusted p-values was used to test for differences in BCS across weight categories. Results: There was a moderate negative correlation (R2 = -0.57, p = 0.017) between Fx and BCS, there was a moderate negative correlation between Fy and BCS (R2 = -0.65, p=0.004) and there was a moderate negative correlation between Fz and BCS (R2= -0.58, p = 0.016). There was a significant effect of weight category on Fx, Fy and Fz. For Fx (χ2 2= 6.46, p = 0.040), Fy (χ2 2= 7.62, p = 0.022) and Fz (χ2 2= 6.61, p = 0.035); forces were significantly lower in the overweight group compared to the underweight group (p< 0.05). Discussion: Dogs that were classified as overweight and had a higher BCS, generally had lower peak GRFs. This was an unexpected finding, but despite attempts to control speed, overweight dogs may have walked at slower velocities than dogs of a normal weight. Further work is needed to fully understand the effect of BCS on limb kinetics in healthy dogs in order to better appreciate the benefits of weight loss to both normal and pathological animals. References: 1. Impellizeri, J.A., Tetrick, M.A., Muir, P., 2000. Effect of weight reduction on clinical signs of lameness in dogs with hip osteoarthritis. Journal of the American Veterinary Medical Association 216, 1089–1091.