For a long time, force plate (FP) gait analysis has been used in veterinary science.1 Quantitative gait analysis is expected to enable the detection of mild lameness that is not visible and the verification of disease-specific gait patterns.2,3 FP gait analysis is commonly used to diagnose orthopedic diseases,4 can be used to objectively evaluate treatment outcomes for various orthopedic diseases, and has been used in clinical research.5 The sensitivity and specificity of the FP analysis of dogs are 93% and 94%, respectively, indicating that it is a useful diagnostic method.3 By obtaining repeatable data, it is possible to obtain objective, quantifiable, and accurate information regarding the normal or abnormal gait of dogs. Currently, the diagnosis of canine lameness tends to be subjective, because the interpretation of visual examination, which is the mainstream approach for gait analysis, is influenced by clinical and personal experience.1 Therefore, the application of a gait analysis system, such as FP, to evaluate individual cases of lameness is likely to be more clinically valuable. Various factors, such as velocity, acceleration, handler, weight, breed, physique, daily variation, number of trials, and habituation, may affect variations in the ground reaction force (GRF).2,4–17
There have been many reports of GRFs in the vertical force (Fz) direction, such as peak vertical force (PVF) and vertical impulse (VI), and in the cranial or caudal force (Fy) direction, such as peak propulsive force (PPF), propulsive impulse (PI), peak braking force (PBF), and braking impulse (BI); however, there have been only a few studies10,17,18 of GRFs in the medial or lateral force (Fx) direction, such as peak lateral force (PLF), lateral impulse (LI), peak medial force (PMF), and medial impulse (MI). GRFs in the Fz direction have less variability and are most often used clinically,18 because the vertical force has to support the body weight. GRFs in the Fy direction show an increasing trend as the velocity increases, but the extent of variation is large and the reliability is low.18 Regarding GRFs in the Fx direction, significant differences and trends are often not detected, partly because the values are smaller than those of other parameters.10,17,18
Most previous studies have evaluated the Fz direction in large dogs such as Greyhounds, Labrador Retrievers, and Rottweilers, whose body weight is often greater than 20 kg; however, only a few studies have evaluated small to medium dogs weighing around 10 kg2–4,7–10,12–15,17 and their GRFs in the Fx or Fy direction.3–9,12,13,15 In this study, 2 FPs were used to evaluate changes in GRFs in relation to gait velocity and differences in GRFs, including the Fx and Fy directions, among healthy Beagles, which are small dogs. It was hypothesized that a certain trend would be observed for GRFs in the Fx and Fy directions with 2 FPs.
The funding sources did not have any involvement in the study design, data analysis and interpretation, or writing and publication of the manuscript.
The authors declare that there were no conflicts of interest.
We thank Editage (www.editage.com) for English language editing. We also thank the students of the Laboratory of Small Animal Surgery, Azabu University, and Vetz Petz for their support.
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