Laura Peeters

34 | Chapter 2 stability, and deficits in trunk control may indirectly affect head stability as well. Adding external trunk support improved head stability in children with CP, but this result was very much dependent on disease severity and level of support [29, 42, 43]. Head stability improved with higher support level in healthy children, healthy adults and in children with CP (GMFCS levels I – III). Still, head stability in the sagittal plane was worse in children with CP compared to healthy persons even when supported at thoracic level [20, 42], indicating that children with CP had deficits in both trunk and head stability. Support at mid-thoracic level resulted in improved trunk stability, postural alignment and reaching performance in children with GMFCS level IV, whereas support at axillary level restricted them in their active movements and, therefore, negatively affected their posture and reaching performance [29, 43]. For children with GMFCS level V, head stability did not improve significantly with external support at axillary level, indicating that even this level of support was not sufficient for improving reaching performance. Santamaria, et al. [29] found improvement in head alignment with support at axillary level, whereas Saavedra and Woollacott [43] did not find any effect. No studies were found regarding the interaction between trunk and head in patients with SCI. Interaction trunk – head – arm No studies were found describing the interaction between all three segments combined in any group of neurological patients. However, a few studies in healthy children provided results on the interaction between the trunk, head and arm. Head and trunk movement directions with respect to the arm and strategies for head movement relative to the trunk, varied across movement planes and reaching distances (Figure 2) [13]. These interactions also mature at different ages. The trunk starts moving prior to the arm movement when reaching forward beyond arm length [12, 17, 18], however, the literature is contradicting whether this also applies to reaching within arm length. When reaching laterally, a top-to-bottom sequence (head-trunk-pelvis) was found in healthy adults [44]. DISCUSSION This review provides an overview of trunk movement and stability when performing upper extremity activities in a seated positionin neurological patients with a flaccid trunk compared to healthy subjects. Overall, in most studies, the study samples were relatively small and rarely exceeded 15 participants per group. Larger studies