SUMMARY An investigation was made of the stride characteristics of horses jumping 2 obstacles during a Grand Prix competition. One obstacle was a picket fence and rail 1.3 m high (fence 2), and the other was a coop and rail 1.52 m high (fence 11). Thirteen distance and 22 timing measurements of 17 horses were extracted from high-speed films, using computer-aided analysis. These data were used to compare takeoff and landing of the lead and nonlead legs, the thoracic limbs and pelvic limbs, and fence 2 and fence 11. Paired t -tests were used to compare means and a stepwise regression analysis was done for each fence, using the total horizontal distance jumped as the dependent variable. Stride timing and distance measurements did not differ ( P < 0.05) between the 2 fences. Each horse approached the fences in a moderately fast canter and, at takeoff, placed the nonlead thoracic limb earlier and farther from the fence than the lead thoracic limb ( P < 0.05). The nonlead leg stance phase lasted longer than the lead leg stance phase ( P < 0.05). The lead and nonlead pelvic limbs acted more in unison than the thoracic limbs and did not differ in their time of placement, stance phase duration, or position from the fence ( P < 0.05). The overlap of the stance phases of the pelvic limbs was greater than that of the thoracic limbs ( P < 0.05). The pelvic limbs remained on the ground for a longer period of time and were placed closer to the jump than the thoracic limbs ( P < 0.05), but the total stance phase of the thoracic limbs did not differ from the total stance phase of the pelvic limbs ( P < 0.05). In 15 of 29 jumps studied, the lead thoracic limb changed during the jump. In the landing phase the lead thoracic limb was positioned further from the jump and had a longer stance phase and single support than did the nonlead thoracic limb ( P < 0.05). The overlap increased and advanced placement decreased between these limb pairs on landing as compared with the takeoff ( P < 0.05). The distance between the pelvic limbs at landing was greater than at takeoff ( P < 0.05), but was not significantly different from the distance between the thoracic limbs at landing. The stepwise regression analysis selected different independent variables for the 2 fences. The final regression equation for fence 2 included 5 independent variables and had an adjusted R 2 value of 0.999. Four of these independent variables were distance measurements and 4 described the thoracic limbs. The R 2 value of the final regression equation for fence 11 was 0.953 and all 3 independent variables selected were distance measurements of the pelvic limbs.
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LEACH et al. (1984) studied this question.