HUBER, SS; HOYT, DF; DUTTO, DJ; WICKLER, SJ; California State Polytechnic University, Pomona: Jumping mechanics of the quadruped: the equine forelimb

Six horses jumped obstacles of different heights (0.6 and 1.0 m) to test the following hypotheses: 1) additional work would be required to jump higher, and 2) the elbow would produce the most work of all the forelimb joints. Ground reaction forces and kinematics of the forelimb were collected synchronously and combined using inverse dynamics to calculate joint moments, power, and work during stance. Net work of the forelimb did not change with increasing obstacle height. On average, the elbow did more net work (0.39 � 0.04 J/kg, mean � standard error) than the net work of the whole limb (0.34 � 0.05 J/kg) during stance. The shoulder produced a small amount of net positive work (0.05 � 0.04 J/kg) while distal joints produced net negative work: distal interphalangeal (-0.04 � 0.05 J/kg), metacarpophalangeal (-0.01 � 0.02 J/kg), carpus (-0.04 � 0.02 J/kg). The braking phase of the horizontal ground reaction force increased in magnitude and duration with increasing obstacle height. During stance, horizontal velocity decreased 56% more, and vertical velocity increased 123% more, for the 1.0 m obstacle than the 0.6 m obstacle. In summary, the elbow appears to be the primary joint in the forelimb that contributes to elevation of the forequarters of the horse during jumping. This contribution from the elbow over higher obstacles, without an increase in net work of the limb, is due to more horizontal velocity being converted to vertical velocity by elastic structures. Supported by NIH # S06 GM53933 to DFH & SJW