DUTTO, D.J.*; HOYT, D.F.; CLAYTON, H.M.; COGGER, E.A.; WICKLER, S.J.; Calif. State Polytechnic Univ., Pomona, 91768; College of Veterinary Medicine, Michigan State University, East Lansing, MI 48854: Joint kinetics of the horse during trotting: the hind limb during stance
During trotting, a horse generates force with diagonal fore- and hind limbs during each stride. The role of each limb is different, as the peak vertical force of the forelimb increases with speed, but the hind limb force does not from 2.5 to 5 m/s. Does the work produced by the hind limb change in this speed range? Synchronized ground reaction force (1000 Hz) and digital video (250 Hz) were recorded while horses trotted at a constant speed on a runway. Inverse dynamic analysis was used to determine the joint moment, power, and work generated during the stance phase of trotting for the joints of the hind limb (hip, knee, ankle, metatarsophalangeal [MP], and distal interphalangeal [DIP]) of 4 horses. During most of stance, hip and ankle joints generated extensor moments (peak values: 1.3 � 0.3 Nm/kg and 1.7 � 0.3 Nm/kg, respectively), while flexor moments occurred at the knee and MP joints (-1.2 � 0.3 Nm/kg and -1.3 � 0.2 Nm/kg). Only the peak hip extensor moment tended to increase slightly as speed increased (slope = 0.23, r2 = 0.28). Positive power peaked in the proximal joints first starting with the hip (4.0 � 1.5 W/kg; 32% of stance), ankle (3.8 � 1.8 W/kg; 63% of stance), and finally MP (7.1 � 1.7 W/kg; 71% of stance) joints. Peak positive power tended to increase for the hip and knee, but not the ankle or MP joints as speed increased. Net work produced by the hind limb was essentially independent of speed (0.35 � 0.08 J/kg), with the hip contributing the most to net work (0.39 � 0.14 J/kg). On average, the knee, ankle, and MP joints produced net positive work, while the DIP produced net negative work. Supported by NIH # S06 GM53933 to DFH & SJW.
