Joint Position. The pattern of knee joint linear motion is similar in the two movements. For both movements, the vertical displacement is very small while the horizontal movement is large. In walking, the range of horizontal displacement is 0.35 m and there is 0.02 m displacement in the vertical direction which leads to the resultant being dominated by the horizontal displacement. In trotting, the range of horizontal displacement is .6 m and again there is 0.03 m displacement in the vertical direction which leads to the resultant horizontal displacement. An interesting note is that, in looking at the data for linear movement, during walking the hip moved a total of 0.7 m. During trotting, the hip only moved 0.6 m.
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Figure 8. Position of the knee joint in walking (left) and trotting (right). Negative values correspond to forward in the horizontal direction. Positive values correspond to upward movement in the vertical direction. The dashed line represents the horizontal position. The heavy dashed line represents the vertical position. The solid line represents combined curves. | |
Joint velocity. In the walking movement, the knee joint velocity increases, then decreases and levels off through the end of the stance phase and into the swing phase. The velocity decreases as the swing phase ends. Although the pattern of linear motion is similar in the two gaits, the horizontal velocity was much greater in the trot. The horizontal component is more important than the vertical component in determining the resultant velocity. In the trotting movement, the knee joint velocity increases during the stance phase, decreases through half of the swing phase were it increases until the end. The horizontal component is more important than the vertical component in determining the resultant velocity. An interesting note is that, in looking at the data for linear velocity, during walking the hip moved at a rate of 0.47 meters per square second. During trotting, the hip moved at a rate of 1.57 meters per square second.
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Figure 9. Velocity of the knee joint in walking (left) and trotting (right). Negative values correspond to forward in the horizontal direction. Positive values correspond to upward movement in the vertical direction. The dashed line represents the horizontal position. The heavy dashed line represents the vertical position. The solid line represents combined curves. | |
Center of mass. The center of mass was calculated for the thigh, calf, and paw segments for the initial position of both the walking and the trotting movements. The center of mass is located in two very different locations. For the walking motion, the center of mass is located very far behind the body segment. This could be due to errors in locating the joint centers. For the trotting motion, the center of mass is located near the hip joint. Although, for both movements, the center of mass is not on the body segments.
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Figure 10. Location of the center of mass (CM) in walking (left) and trotting (right). The figure shows the thigh, calf, and foot segments for the subject in the initial position for each movement. Positions show the distances from the reference marker. | |
