Segment angle. The angle of the thoracic spine segment of the subject was analyzed for both the Ab-Shaper and the Ab-Flex devices. Both movements had the subject starting at the supine position of approximately 90 degrees counterclockwise from anatomical position. The Ab-Shaper crunch produced a greater range of motion, decreasing from 86 degrees (supine) until reaching 56 degrees (minimum angle) and returning back to a starting position of 86 degrees. The Ab-Flex crunch began in a supine position of 88 degrees counterclockwise from anatomical position and decreased to a minimum of 63 degrees. Subject returned to initial starting position of 86 degrees.
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Figure 3. Thoracic spine angle during the Ab-Shaper crunch (left) and the Ab-Flex crunch (right). Anatomical position corresponds to 90 degrees. Positive angles represent clockwise rotation from the vertical axis about an axis through the distal rib. | |
Segment velocity. The Ab-Shaper crunch produced a greater segment velocity than the Ab-Flex. The maximum angular velocity for the Ab-Shaper crunch (117 deg/s) was faster than the Ab-Flex crunch (106 deg/s). The minimum angular velocity was also greater for the Ab-Shaper crunch (-133 deg/s) than the Ab-Flex crunch (-91 deg/s).
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Figure 4. Thoracic spine angular velocity during the Ab-Shaper crunch (left) and the Ab-Flex crunch (right). Positive velocity values represent clockwise rotation from the vertical axis. | |
Joint angle1. The maximum lumbar-thoracic angle for the Ab-Shaper crunch measured clockwise from the anatomical position of 360 degrees was 355 degrees. A reduction of the angle during the ascent phase produced a minimum angle of 319 degrees. The Ab-Shaper crunch returned to an anatomical position of 357 degrees. Total range of motion for movement was 38 degrees. The Ab-Flex crunch began at approximately the same anatomical position (357 degrees) and decreased during the ascent phase to 323 degrees. The Ab-Flex crunch returned to a starting position of 356 degrees. Total range of motion for the Ab-Flex crunch was 34 degrees. Ab-Shaper crunch produced slightly more trunk flexion (38 degrees) than Ab-Flex (34 degrees). Thus, range of motion can be said to be similar for the two devices.
Lumbar thoracic trunk motion during both sit-ups consisted of trunk flexion from the supine position (360 degrees) followed by extension back to the supine position (360 degrees). Minimum lumbar thoracic angle differed. It was greater in the Ab-Shaper (319 degrees) than in the Ab-Flex (323 degrees).
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Figure 5. Lumbar-thoracic angle during the Ab-Shaper crunch (left) and Ab-Flex crunch (right). Lumbar-thoracic angle is measured clockwise from the right horizontal to the thoracic segment. Anatomical position corresponds to 360 deg. Decrease in values indicate flexion about the Lumbar-thoracic joint. | |
Joint angle 2. The maximum cervical-thoracic angle (absolute angle) for the Ab-Shaper crunch corresponds to an angle of 270 degrees. Increase in angular displacement indicates flexion of the cervical spine. The Ab-Flex crunch produced a much greater range of motion (66 degrees) decreasing from the starting position of 192 degrees from anatomical position to a minimum angle of 126 degrees. The Ab-Shaper crunch produced a much smaller range of motion (22 degrees) decreasing from the starting position of 153 degrees from anatomical position to a minimum angle of 146 degrees. Peak angle during the Ab-Shaper crunch occurs at 165 degrees. Peak angle for the Ab-Flex crunch occurs at 192 degrees.
There is a big difference in the shapes of the two graphs. The cervical thoracic region for the Ab-Shaper had virtually no motion. The Ab-flex has an increase range of motion with flexion then extension.
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Figure 6. Cervical-thoracic angles in the Ab-Shaper (left) and in the Ab-Flex (right). Cervical-thoracic angle is calculated as the anterior angle between the thoracic and cervical segments. Anatomical position corresponds to an angle of 180 degrees. Decreasing angular displacement indicate flexion while increasing values indicate extension. | |
Angle-Angle Plot. Coordination of the cervical-thoracic and the thoracic-lumbar angles was vastly different in the two movements generated by the Ab-Shaper and the Ab-Flex. In the Ab-Shaper crunch, the cervical-thoracic movement remained fairly constant at approximately 150 degrees throughout the movement while the lumbar-thoracic produced a much greater range of motion. In the Ab-Flex crunch, motions were coupled between the cervical-thoracic and the thoracic-lumbar. Both the cervical-thoracic and lumbar-thoracic exhibited flexion during the ascent phase of the Ab-Flex crunch and extended together in the descent phase.
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Figure 7. Coordination of the cervical-thoracic and thoracic-lumbar angles in the Ab-Shaper crunch (left) and in the Ab-Flex crunch (right). Arrows indicate direction of motion. The tail of the arrow is located at the beginning of the movement. | |
