###### Abstract
They also found that children with CP seemed to develop at least three control patterns of postural adjustment: (1) variable patterns of postural control, (2) stereotyped patterns of weakly modulating postural control, and (3) stereotyped patterns with stiff postural control, implying that these children might balance their body according to previous experience for reaching tasks. Additionally, they discovered that selective postural control, in accordance with the balancing situation, could be the key component for children with CP functioning well in daily life. Other researchers have found children with CP could balance themselves with specific muscle recruitment at different balancing conditions, demonstrating higher levels of self-care performance than children who could not react selectively in such situations. This evidence supports a relationship between postural control ability and upper extremity functionality. In another study, researchers examined the reach performance (kinematic data) of people with hemiplegic CP (age: 11-27 years old) compared to a control group with typical development (age-matched) [21]. Impaired forearm supination was characterized in the CP group. The results showed that people with CP recruited extra-trunk movement to compensate for their deficit of upper extremity movement; additionally, yet another research study showed similar findings [22]. Children with CP and TD (aged 5-14 years) performed a reach-and-drink task with supported seated posture, and children with CP increased forward trunk motion compared to children with TD while conducting the task [22]; however, this extra trunk displacement of children with CP occurred in a supported sitting position. In [PERSON] and [PERSON]'s study (2018), the researchers also found a similar result, as they requested children with hemiplegic CP to reach targets on the frontal plane and found that this specific group demonstrated less trunk rotation than TD children during reach [23]. It seems that people with CP perceive their characteristics and develop a motor solution (alternative movement pattern) to complete functional tasks. [PERSON] et al. derived a detailed kinematic analysis as indispensable in planning therapy for people with motor difficulty [21]. Although these studies have revealed that children with CP demonstrated several motor control problems during reaching, the relationship between postural control ability and hand-reach performance was not consistently tested. The children were not seated freely (certain postural constraints were used in these studies) while reaching for a target; additionally, previous researchers might have recruited children with hemiplegic CP who had less postural control disadvantage compared to children with diplegic CP [23]. Accordingly, limited kinematic information regarding reaching performance in children with diplegic CP has been reported, such as head, trunk, and pelvis alignment and movement since the subjects have difficulty managing to balance themselves during functional tasks. Formerly, our research revealed that the outcome of hand performance (movement units and straightness ratio) in terms of coordination and smoothness of movement is significantly correlated with postural control ability by children with CP [24]. The children with insufficient postural control ability produced inadequate coordinated and inefficient hand reach. In addition, children with CP demonstrated different patterns of postural adjustment in terms of center of pressure (COP) performance compared to TD children when reaching in different directions [25]. The findings of this study revealed that COP performance (e.g., sway ratio: SR) of children was negatively correlated with hand movement units (MUs). Children with insufficient postural control ability (low PRT score) also showed wide COP excursion (small SR value) with the evidence of increasing absolute peak COP velocity in the medial-lateral direction.