SCHREIBER, JS; DUTTO, DJ; HOYT, DF; CLAYTON, HM; COGGER, EA; WICKLER, SJ; California State Polytechnic University, Pomona; California State Polytechnic University, Pomona; California State Polytechnic University, Pomona; Michigan State University; California State Polytechnic University, Pomona; California State Polytechnic University, Pomona; ; : Hind Limb Joint Kinetics Of The Horse During Decline Trotting: A Pilot Study
During decline (DEC) trotting, the forelimb of a horse produces similar vertical peak forces but greater breaking impulse relative to the level (LVL) over a range of speeds. Differences in breaking impulse must be created by altered joint kinetics on the DEC. Which forelimb joints are responsible for the differences observed in breaking impulse during stance on the DEC relative to the LVL? Synchronized ground reaction forces (1000 Hz) and digital video (250 Hz) were recorded while horses trotted at constant speeds on a level and 10% declined runway. Inverse dynamic analysis was used to determine the joint moment, power and work generated by the forelimb joints: shoulder, elbow, carpus, metacarpophalangeal (MP) and distal interphalangeal (DIP). Average values reported are for a range of speeds of 2.0 to 5.0 m/s. The shoulder generated larger flexor and extensor moments for a greater fraction of stance on the DEC than on the LVL. The elbow generated a greater flexor moment for about the same fraction of stance and a larger extensor moment for a greater fraction of stance. Negative power on the DEC was greater for shoulder (-9.4 � 3.7 v. �2.8 � 1.4 W/kg, DEC and LVL, respectively) and the MCP (-7.9 � 2.3 v. �4.1� 1.5 W/kg). Contrary to the LVL, net negative work was produced by both the shoulder (-0.6 � 0.2 v. 0.11 � 0.07 J/kg) and the MCP (-0.4 � 0.2 v. 0.1 � .01 J/kg), and net work by the forelimb is negative on the DEC (-0.6 v. 0.06 J/kg). The shoulder and the MCP produce the negative work necessary to counter gravitational acceleration on the DEC, producing the differences in breaking impulse. Supported by NIH # S06 GM53933 DFH & SJW and an ARI grant to SJW.
