## 4 Discussion  
Our two reported studies have found that children with CP react differently than TD children during reaching tasks, especially for medial reaching [24; 25]. In this detailed kinematic analysis, while reaching in different directions, various angular changes of joint movement were noticed between groups. Children with CP perform different forms of angular patterns of head, trunk, and pelvis segments to manage different tasks than TD children. For postural preparation 300 ms before reach began, children with CP oriented their head and trunk toward the reaching direction in advance, but TD children did not. Children with CP rotated their head and trunk to a greater degree than did TD children to manage the different reach directions; therefore, they might not need to deal with postural adjustment (rotating the body toward the reach direction), postural stability, or hand reach (controlling the upper extremities) at the same time. [PERSON] and [PERSON] (2007) mentioned that postural control could be categorized into two parts: postural orientation and postural stability [29]. This study demonstrated that children with CP chose to align the head and trunk first in order to decrease the demand of the task (needing to re-orient the body and stabilize it at the same time during the task). This result suggests that children with CP perceive their deficit and choose an alternative way to adapt their ability in order to complete the task safely. In [PERSON]'s study, the researchers also found similar results. Children with CP (mean age: 9.5 years) who encountered difficulty in controlling reach and postural stability at the same time found much more advantage in external trunk support than children with CP, who demonstrated fewer problems controlling dual tasks [14]. Furthermore, when the target is located in different directions, such as on the medial side of the trunk, subjects have to deal with the Coriolis force created with trunk rotation, and researchers have found that people create more flexor movement of the upper extremities to counterbalance the Coriolis effect if they reach medially compared to other directions [30]. It is possible that children with CP prepare alignment before reaching begins in order to decrease the need of the upper extremities to deal with the effect of the Coriolis force, since children with CP have deficits in recruiting motor movement efficiently or regulating force in advance [15; 16]. In our study, we consistently found that children with CP reacted differently than TD children during medial reaching. A previous investigation reported that children with CP spent more time on reaching than returning (normalized movement time relative to the reach cycle: 54.2% vs. 45.8%, respectively), but TD children did not show this strategy (47% vs. 53%, respectively) during medial reach. In addition, children with CP demonstrated a larger straightness ratio (SR) of the hand-reach path (the larger the SR, the less efficient the reach) at medial reach, but TD children maintained rather stable SR (close to 1) [24]. Besides, it was also noticed that children with CP demonstrated different postural adjustments than TD children [25]. During acceleration and deceleration phases of medial reach, a greater proportion of children with CP used more apparent pushing or braking force for balancing than did TD children, so these kinematic results further confirm this different phenomenon observed between the groups. In the acceleration and deceleration phases of medial reach, children with CP rotated their trunk and pelvis to a lesser degree than did TD children (Tables 2 and 3). Children with CP also did not efficiently rotate the trunk toward the medial side as did those with TD (significant interactive effect of trunk rotation; Table 2), so they chose to rotate the body in advance, thereby decreasing the need for trunk and pelvis rotation during reaching.