Neck and shoulder motion of the gallop stride

Abstract

The motion patterns of the neck and shoulders during the gallop stride were documented using high-speed cinematography. The gallop stride characteristics of 4 Quarter Horse fillies, approximately 30 months of age, were used as a model. Horses were housed and fed together and received the same amount and type of limited training; and were all ridden with the same tack and by the same person. Both sides of each horse were filmed simultaneously (243 frames/sec) while galloping individually along a 1.5-m-wide track. Kinematic variables describing 29 strides (mean velocity 13.1 m/sec, stride frequency 2.6 strides/sec, stride length 5.1 m) included linear and temporal measurements of the maximum and minimum heights of the wing of the atlas, spine of the scapula, shoulder joint and elbow joint; maximum and minimum angles with respect to the horizon of the neck, shoulder and arm segments; and maximum and minimum relative angles between the neck and shoulder, and shoulder and arm segments. Differences (P<.05) between the leading and trailing sides of the body were identified for 12 of a total of 27 spatial measurements reported for the neck, shoulder and arm, including minimum height of the scapula spine, maximum height of the scapula spine and elbow joint, maximum absolute angle of the shoulder segment, and minimum angle between neck and shoulder segments. Of 18 temporal measurements reported involving the neck, shoulder and arm, 14 differed (P<.05) between leading and trailing sides. Kinematic events describing the motion of the leading and trailing shoulder and arm segments were ordered and tabulated in the temporal sequence of the normal gallop stride. Results indicated that the motion patterns of the shoulder and arm segments were highly specific to the leading and trailing sides of the body in the equine gallop stride. The work required for vertical displacement of the center of mass in galloping was estimated to be approximately 98,500 J/km or 23.5 kcal/km; equivalent to approximately 6 percent of the total energy expenditure for galloping 1 km.