Author and graduation date: Athina A. ZARCADES, April, 2002

Committee members: Roger Simmons (Chair), Peter Francis, Karen May-Newman

Thesis title: Body Segment Stabilization in the Horse During Three Forms of Gait

Previous research has shown that either the head or the trunk body segments need to be stabilized during locomotion in order to give feedback to the brain about the environment and body orientation in space. Different forms of gait in humans (walk, run) produce different velocities, and thus, different pitch rotations of the head and/or trunk. To date, there has been no research examining the pitch rotations of head or trunk movement in the equine species during various forms of locomotion. The purpose of this study is to determine whether multiple segments (head and trunk) are stabilized (rotations <20 degrees) relative to space (i.e., earth horizontal). Three horses from the Rancho Riding Club in Rancho Santa Fe, California, were tested. Four anatomical landmarks were identified by the investigator and were used to create a spatial model for the data analysis. A Sony Digital 8 60 Hz video camera recorded ten trials of walking, trotting, and cantering. At the completion of testing the video record was transferred onto a VHS tape and the researcher analyzed the data using a Peak Motion Analysis System. The study focused on the following variables: average angular rotation and range of angular rotation of the head and trunk relative to earth horizontal. The analysis of the average head rotation revealed a significant main effect for gait. The main effect for trials and gait by trials interaction indicated no significance. The range of head movement relative to horizontal indicated no significant main effects for gait or trials. The gait by trials interaction was also not significant. The analysis of the average angle of trunk movement relative to horizontal revealed a significant main effect for gait. However, there were no significant main effects for trials or for the gait by trials interaction. The range of trunk movement relative to horizontal indicated a significant main effect for gait. Neither the main effects for trials nor the gait by trials interaction was significant. The results of this study support previous research with normal humans, in that, during locomotion horses stabilize their head in order to provide a spatial reference frame. Additionally, rotation of tire trunk was also less than 20 degrees relative to earth horizontal.

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