Force overlap in trotting dogs: a Fourier technique for reconstructing individual limb ground reaction force

Summary

Time overlap of ground reaction forces from adjacent footfalls is a pervasive problem in clinical gait analysis. When overlap occurs, splitting the fore- and hindlimb force curves at the minimum point between them underestimates hindlimb impulse and contact time. A better alternative is to reconstruct the force curves that occur in the period of overlap. A Fourier method was used to quantify the shape of hindlimb force curves in Labrador Retrievers and Greyhounds. Fourier coefficients did not differ significantly (p <0.05) between those breeds, indicating that, on average, their shapes are quite similar. The technique reported here uses an empirically determined shape that is, subsequently, scaled to the duration and magnitude of the original hindlimb force curve. A segment of this approximated force curve is then inserted in order to reconstruct the portion of the curve that was obscured by the overlap. Subtracting the reconstructed hindlimb curve, from the original force record, yields a reconstructed forelimb force curve.

Keywords

Force platforms - canine - gait analysis

• References

• 1 Alexander RMcN, Jayes AS. Fourier analysis of forces exerted in walking and running. J Bio- mech 1980; 135: 383-90.
• 2 Begg RK, Rahman SM. A method for the reconstruction of ground reaction force-time characteristics during gait from force platform recordings of simultaneous footfalls. IEEE Transaction on Biomedical Engineering 2000; 47: 547-51.
• 3 Bertram JEA, Lee DV, Case HN, Todhunter RJ. Comparison of trotting gaits of Labrador Retrievers and Greyhounds. Am J Vet Res 2000; 61: 832-8.
• 4 Bertram JEA, Lee DV, Todhunter RJ. et al. Multiple force platform analysis of the canine trot: a new approach to assessing basic characteristics of motion. Vet Comp Orthop Trauma 1997; 10: 160-9.
• 5 Brodland GW, Thornton-Trump AB. Gait reaction reconstruction and a heel strike algorithm. J Biomech 1987; 20: 767-72.
• 6 Hamming RW. 1986. Numerical Methods for Scientists and Engineers. (2nd ed.).. New York: Dover Publications.;
• 7 Jayes AS, Alexander RMcN. Mechanics of locomotion of dogs (Canis familiaris) and sheep (Ovis aries). J Zool Lond 1978; 185: 289-308.
• 8 Lee DV, Bertram JEA, Todhunter RJ. Acceleration and balance in trotting dogs. J Exp Biol 1999; 202: 3565-73.