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- Author or Editor: David R. Mullineaux x
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Abstract
Objective—To evaluate the locomotor mechanics of the tölt in Icelandic horses.
Animals—10 adult Icelandic horses with no history of lameness.
Procedures—Force platform data were captured for 27 trials for horses ridden at a tölt in a lateral sequence single-foot gait at a steady speed from 0.89 to 5.98 m/s. Simultaneous kinematic data were obtained by tracking retroflective markers overlying the right fore- and hind limbs. These kinetic and kinematic data were combined to evaluate 3 mechanical approaches, duty factor, Froude number, and center of mass (COM) mechanics, and to evaluate the capacity to recover mechanical energies during tölting via inverse pendulum and spring-mass (bouncing) mechanics.
Results—Tölting horses had in-phase fluctuations of gravitational potential and kinetic energies of their COM and a capacity to recover mechanical energy through elastic recoil of spring elements in their limbs. These characteristics, along with Froude numbers exceeding values expected for the walk-run transition, are indicative of bouncing mechanics and, hence, most strongly ally tölting with running. Only the footfall pattern of a lateral sequence single-foot gait and low vertical excursions of the COM are more commonly associated with walking.
Conclusions and Clinical Relevance—At the tölt, horses have unique mechanical characteristics that should be understood for veterinary care. Differences in interlimb coordination between tölting and trotting mask the overall similarities in most other aspects of their locomotor dynamics.
Abstract
Objective—To assess the reliability of the center-ofpressure (COP) values obtained from a force platform for analysis of postural sway in horses.
Animals—Six 2-year-old horses that were free from lameness and neurologic disease.
Procedure—Horses stood stationary with all 4 hooves on a force platform; COP data were collected at 1,000 Hz and 3-dimensional kinematics collected at 60 Hz for 10 seconds. Five trials were recorded at each of 3 time periods (15-minute intervals) or at 1 time period on 3 separate days. Mean values for each set of 5 trials and actual, normalized, and relative COP variables were calculated. The reliability was quantified by use of agreement boundary.
Results—The COP results within and across days were similar and provided small agreement boundary limits (eg, across days, in order of least relative reliability: area, ± 62 mm2; mediolateral range, ± 8 mm; radius, ± 2 mm; craniocaudal range, ± 4 mm; and velocity, ± 3 mm/s). Head height possessed the greatest relative intraday reliability (12%) but a high agreement boundary limit (± 0.15 m).
Conclusions and Clinical Relevance—The use of a force platform to analyze postural sway in a group of young healthy horses was found to produce reliable results and may provide a simple and sensitive measure for assessing balance deficiencies in horses. Agreement boundaries provide 95% confidence intervals for use as limits of error and variability in measurements that, if exceeded, may signify meaningful effects. (Am J Vet Res 2003;64:1354–1359)
