RESULTS: Angular Kinematics

Segment angle. Our segment angle was the trunk segment. In the forward walking movement our maximum angle was 19 deg. and our minimum was -4 E 10-7 deg. These occurred at 8.6% and 42.8% of the gait cycle, respectively. The maximum angle was more forward, instead of vertical because it corresponded to flexion. In backward walking, the maximum angle was 16 deg. This occurred at 47.1% of the gait cycle. The minimum angle for backward walking occurred at 5.3% gait cycle and the angle equaled -3.3 deg. In forward walking our range of motion was 19 degrees. Our backward walking range of motion was 19.22 degrees.

Figure 3. Trunk segment angle during forward walking (left) and backward walking (right). Trunk angle was calculated from the vertical (0 degrees corresponds to anatomical position); increased values represented clockwise rotation from the vertical. Increased positive values represented flexion. Extension occurred in the counterclockwise direction, which was negative. The positive and negative directions were consistent for both backward and forward walking.

Joint angle 1. In forward walking movement, our maximum angle of the knee joint was 179 deg. and our minimum was 118 deg. The maximum occurred at 97.14% of the gait cycle and the minimum occurred at 74.3% of the gait cycle. The maximum of 179 deg. occurred while the knee was flexed at the beginning of the gait cycle. Therefore, the maximum angle was peak flexion. The minimum angle occurred during swing phase of the gait cycle when the knee was in extension, which corresponded to the minimum angle as peak extension. In backward walking movement, the maximum angle was 184 deg. which occurred during extension of the swing phase. The minimum angle was 126 deg. which occurred during stance phase at the end of the gait cycle. The maximum angle occurred at 58.1% of the gait cycle and the minimum angle occurred at 94.3% of the gait cycle. The range of motion for forward walking was 61 deg. and the range of motion for backward walking was 58 deg. Thus, the range of motion was not that different for forward and backward walking.

Figure 4. Knee angles in the forward walking (left) and backward walking (right). Anatomical position corresponded to 180 degrees. Flexion corresponded to angles less than 180 degrees, angles greater than 180 degrees corresponded to extension. The knee angle was calculated as the posterior angle between the thigh and shank body segments. This angle was calculated from a horizontal line through the knee joint.

Joint angle 2. In forward walking movement, the maximum dorsiflexed angle occurred at 137 deg. and the minimum plantarflexed angle was 88 deg. Therefore, forward walking range of motion was 49 deg. The maximum angle occurred during the swing phase with dorsiflexion of the foot and flexion of the ankle. The minimum angle occurred during plantarflexion of the foot and extension of the ankle just prior to swing phase. In backward walking, the maximum dorsiflexed angle was 139 deg. and the minimum plantarflexed angle was 99 deg. The range of motion for backward walking was less than forward walking at 40 deg. The maximum angle occurred with dorsiflexion of the foot and flexion of the ankle during the end of swing phase. The minimum occurred at toe strike, at the end of the backward walking movement, while the foot was plantarflexed and the ankle joint was extended.

Figure 5. Ankle angles in forward walking (left) and backward walking (right). Anatomical position in forward walking was 120 degrees and was 130 degrees in backward walking. This angle was calculated in the clockwise direction, in both movements, from the posterior shank to the foot segment. Decreasing values represented extension, i.e. plantar flexion, of the ankle joint.

Joint velocity. In forward walking, the maximum plantarflexed ankle velocity was 272 deg./sec. which occurred at 42.8% of the gait cycle. The minimum dorsiflexed velocity was -385 deg./ sec. which occurred at 60% of the gait cycle. The maximum velocity occurred during forward movement when toe off was initiated and the minimum velocity occurred at the completion of swing phase. In backward walking, the maximum plantarflexed velocity was 950 deg./sec. which occurred at 0% of the gait cycle and the minimum dorsiflexed velocity was -305 deg./ sec. at 19.3% of the gait cycle. The maximum velocity occurred at the initiation of the gait cycle. The minimum velocity occurred at heel strike prior to the swing phase.

Figure 6. Ankle joint angular velocity in forward walking (left) and backward walking (right). In relation to anatomical position, negative velocity represented dorsiflexion and positive velocity represented plantarflexion, in both forward and backward walking.

Angle-Angle Plot. Knee and ankle angle plots were used to determine coordination between the joints. In forward walking, the gait cycle began with knee flexion, while the ankle plantarflexed, dorsiflexed, and then plantarflexed. As the gait cycle was completed, the knee extended, while the ankle plantarflexed and then dorsiflexed. In backward walking, the gait cycle was initiated with knee extension, while the ankle plantarflexed then dorsiflexed. At completion of the gait cycle, the knee flexed as the ankle plantarflexed and then proceeded to dorsiflex as the knee extended.

Figure 7. Coordination of knee and ankle angles in forward walking (left) and backward walking (right). The movement in forward walking started at 180 degrees in the x axis and 115 degrees in the y axis and proceeded to move downward, up and to the left, down, down and to the right, and then up to the right. The movement in backward walking started at 144 degrees in the x axis and 136 degrees in the y axis and proceeded straight downward, up and right, down to the left, straight up, and then down to the right.