RESULTS: Linear Kinematics

Joint Position. The linear displacement of the hip was similar in both subjects. The similarity of the curves of the graphs suggest that both the experienced and novice rowers experience a similar pattern of velocity. There was, however, a qualitative difference. Both rowers start at a position of about 0.78m. The novice rower gets to a final distance of 0.37m in 2sec, while the experienced rower reached a final distance of 0.12m in 1s. This means that the experienced rower moved 3 times farther than the novice in half the time. The difference in the distance traveled is mostly due to the fact that the experienced rower was almost 0.31m (1 ft) taller than the novice rower. The most drastic difference seen in these graphs is the amount of time it took to reach maximum distance.

Figure 8. Linear displacement of the hip in the novice rower (left) and the experienced rower (right). Increasing values represent forward movement in the horizontal direction., with no movement in the vertical direction. The purple line represents the horizontal position and the pink line represents the vertical position.

Joint velocity. There were noticeable differences between the two rowers when looking at the linear velocity of the hip. The horizontal velocity, represented by the purple line, showed differences between the experienced and the novice rowers. The novice reaches a maximal negative velocity of 1.14 m/s, while the experienced rower reached approximately 3 m/s. Although the values were different, both rowers reached their maximal negative velocity at almost the exact same time, about 0.52 sec. This suggests that maximal speed was reached at about halfway through the drive for the experienced rower, and at about one quarter of the drive for the novice. The minimum velocity of zero for both rowers occurred at the beginning, one point in the middle just before max velocity, and at the end of the movement. The velocity in the vertical direction hovered around zero, due to the fact that both subjects were performing on the same machine, which moved primarily in the horizontal direction. We expected a value of zero for vertical velocity.

Figure 9. Linear velocity of the hip in the novice rower (left) and the experienced rower (right). Positive values represent forward movement in the horizontal direction. The purple line represents the horizontal velocity and the pink line represents vertical velocity.

Center of mass. The location of the center of mass (COM) followed a similar pattern between the experienced and the novice rowers. The COM was found outside the body throughout the entire movement. The novice rower had vertical COM values within 0.01 m of each other, whereas the experienced rower's COM began at 0.47m and ended at 0.38m. This difference was due to the fact that the experienced rower had more of a "lay-back" at the end of the stroke than the novice rower. The COM values for the both rowers in the horizontal direction showed significant changes due to the fact that the motion occurs in the horizontal direction, parallel to the ground. The COM does not change significantly with reference to the trunk segment for either rower.

Figure 10. Location of the center of mass (COM) in the novice rower (left) and the experienced rower (right). Body segments shown are the trunk, thigh, and shank.