Determination of the Centre of Mass in Dogs

Introduction: Inertial measurement units (IMUs) offer an opportunity to monitor activity of a dog in their natural environment. If one understands the relationship between the subject's centre of mass (CoM) relative to commonly measured subject morphometric parameters, the mathematical relationship can be built into an IMU's algorithm. Thus, the objectives of this study were to identify variance of CoM in a heterogeneous population of dogs and describe the relationship between three-dimensional CoM, IMU location, and subject morphometrics. We studied the hypothesis that the relationship between subject three-dimensional CoM and IMU location would be influenced by subject morphometrics.

Materials and Methods: Thirty-one healthy, adult client-owned dogs were included. A single force platform and a reaction board were built to determine each dog's CoM. A neck collar with IMU box was positioned on each dog's neck and a series of measurements acquired while standing. Centre of masses in the transverse, sagittal and dorsal planes were calculated, and statistical analyses performed.

Results: The relationship between three-dimensional CoM and the IMU was significantly influenced by subject morphometrics. Dog length was the only variable required to maximize R-squared. The transverse plane CoM was 52% the distance from ischium to the IMU box. A simple linear regression of variables had an R ² = 0.78, p = 4.85 to 11.

Discussion/Conclusion: This proposed method for determining CoM can be of clinical importance to determine the distance from an accelerometer to the subject's CoM and factor it into the activity reporting algorithm, thus minimizing measurement error when utilizing IMUs in dogs of different morphology.

Acknowledgements: This study was funded by the University of Minnesota Tata Group Endowment. The authors have no conflicts of interest, financial or otherwise, to report.

Publication History

Article published online:
26 October 2022