Angular Kinematics

Segment angle. In both the short stick throw and long stick throw, the upper arm rotated in a clockwise direction. Counterclockwise rotation, indicated by the negative slope, corresponds to shoulder flexion; clockwise rotation corresponds to shoulder extension. In the short stick throw, the maximum arm angle (-52 deg) occurred at the beginning of the motion, and the minimum angle (-98 deg) occurred at 47.6% of movement time. The range of motion, therefore, was 46 degrees. In the long stick throw, the maximum arm angle (-49 deg) also occurred at the beginning of the motion, and the minimum angle (-86 deg) occurred at 50.6% of movement time. The range of motion for this movement was 37 degrees.

Figure 3. Upper arm angle during short stick throw (left) and long stick throw (right). Angle is measured from the vertical; positive values indicate clockwise rotation.

Segment velocity. The shapes for the velocity curves for each movement are generally similar, but have some marked differences. In both graphs, peak angular velocity occurs near the middle of clockwise (shoulder extension) and counterclockwise (shoulder flexion) rotation. The short throw graph indicates, however, that peak velocity during this movement was sustained for a longer period of time. For the short throw, minimum angular velocity was -242 deg/s, and maximum velocity was 91 deg/s. For the long stick throw, minimum angular velocity was -167 deg/s, and maximum velocity was 61 deg/s.

Figure 4. Segment angular velocity of the upper arm in short stick throw (left) and long stick throw (right). Positive values represent clockwise rotation; negative values represent counterclockwise rotation.

Joint angle1. The graphs indicate that elbow angle position was similar for both motions. For the short stick throw, the maximum angle (105 deg) occurred at the beginning of the movement (t=0), and the minimum angle (12 deg) occurred at 73% of movement time (t=0.46 s). Therefore, the range of motion was 93 degrees. For the long stick throw, the maximum angle of the elbow (94 deg) occurred at 8.8% of movement time (t=0.07 s), and the minimum angle (13 deg) occurred at 96.2% of movement time (t=0.76 s). Here, the range of motion was 81 degrees.

Figure 5. Elbow angles in short stick throw (left) and long stick throw (right). Zero degrees represents anatomical position. Angles greater than zero degrees indicate flexion.

Joint angle 2. For the short throw, maximum angle of the wrist (212 deg) occurred at 4.8% of movement time (t=0.03 s), and minimum angle (149 deg) occurred at 88.9% of movement time (t=0.56 s). The range of motion of the wrist was 63 degrees. For the long throw, maximum angle (212 deg) occurred at the beginning of motion, and minimum angle (154 deg) first occurred at 74.7% of movement time (t=0.59 s) and sustained for 0.03 s. Here, range of motion was 58 degrees.

Figure 6. Wrist angles for short stick throw (left) and long stick throw (right). An angle of 180 degrees represents anatomical position. Angles greater than 180 degrees indicate hyperextension.

Angle-Angle Plot. For the short throw, elbow angle started at 105 degrees of flexion; upper arm angle started at -52 degrees of flexion. At ball release, elbow angle for the short throw is 14 degrees, and upper arm angle is -98 degrees. For the long throw, elbow angle started at 90 degrees of flexion; upper arm angle started at -53 degrees of flexion. At ball release, elbow angle is 22 degrees, and upper arm angle is -84 degrees. After ball release, upper arm angle increases slightly, but elbow angle remains relatively constant. Angle coordination for the short throw is less eratic than for the long throw.

Figure 7. Coordination of elbow and shoulder joints in short stick throw (left) and long stick throw (right). Arrows represent direction of movement. Symbol nearest tail of arrow represents starting point of movement.