Stride characteristics of horses competing in Grand Prix jumping.

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 less than 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 less than 0.05). The nonlead leg stance phase lasted longer than the lead leg stance phase (P less than 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 less than 0.05). The overlap of the stance phases of the pelvic limbs was greater than that of the thoracic limbs (P less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)