Segment angle. The upper arm motion between the two bowstrokes was nearly identical. The maximum clockwise angle was greater in the cello with the straight endpin (54 degrees compared to 52 degrees), but the maximum counterclockwise angle was greater with the bent endpin (5 degrees with straight endpin and 9 degrees with bent endpin). Surprisingly, the straight endpin cello boasted a slightly greater upper arm (49 degrees) range of motion. The bent endpin cello fell short at 43 degrees.
|
|
|
|
Figure 3. Upper arm angle during bowstroke with bent endpin (left) and straight endpin (right). The upper arm angle is calculated from the vertical axis about the shoulder joint. Anatomical position corresponds to 0 degrees. Increasing values represent clockwise rotation. | |
Joint angle 1. The elbow angle between the two bowstrokes differed significantly. The bowstroke involving the bent endpin cello had a maximum flexion angle of 279 degrees. There was a smaller flexion angle (259 degrees) regarding the bowstroke on the straight endpin cello. Both setups had the same maximum extension angle at 214 degrees. As expected, the bent endpin cello scored 20 degrees higher, with respect to the range of motion of the elbow, than the straight endpin cello.
|
|
|
|
Figure 4. Elbow angle during bowstroke with bent endpin (left) and straight endpin (right). Elbow angle is calculated as the angle between the upper arm and the forearm. Anatomical position corresponds to 180 degrees. Increasing values represent flexion. | |
Joint angle 2. The wrist angle was similar in both bowstrokes. Radial deviation was greater in the bent endpin (192 degrees) cello than in the straight endpin cello (177 degrees). However, the straight endpin cello had more ulnar deviation (115 degrees) than the bent endpin cello (110 degrees). The range of motion in wrist deviation was 82 degrees for the bent endpin cello while the straight endpin cello was only 62 degrees.
|
|
|
|
Figure 5. Wrist angle during bowstroke with bent endpin (left) and straight endpin (right). Wrist angle is calculated as the angle between the forearm and the hand. Anatomical position corresponds to 180 degrees. Increasing values represent radial deviation. | |
Joint velocity. There was a significant difference in elbow angular velocities of the two setups. Both the maximum flexion and extension velocities were greater in the bent-endpin setup (187 deg/s, -136 deg/s respectively) than that of the straight endpin (123 deg/s, -93 deg/s respectively).
|
|
|
|
Figure 6. Elbow angular velocity in bowstroke with bent endpin (left) and straight endpin (right). Positive values represent flexion velocity. | |
Angle-Angle Plot. For the most part, the angles were coordinated in a similar fashion. Both movements involved abduction of the shoulder and extension of the elbow. The diagonal direction in both angle-angle plots was a telltale sign of both actions working at a constant ratio. However, the bowstroke involving the straight endpin cello had tighter coordination while more decoupled coordination was evident in the bent endpin cello.
|
|
|
|
Figure 7. Coordination of wrist angle and elbow angle in bowstroke with bent endpin (left) and straight endpin (right). | |
