Laura Peeters

Trunk, head and pelvis interactions in healthy children | 49 3 BACKGROUND Children with neuromuscular disorders (NMD) suffer from progressive muscle weakness. Generally, they first lose the ability to walk, followed by a decrease in trunk and arm function. Some children, e.g. with spinal muscular atrophy type I or II, may never have the ability to walk while patients with Duchenne muscular dystrophy lose the ability to walk around the age of 12 years [1]. When seated in a wheelchair, autonomy and level of independence are highly dependent on arm function [2]. Patients report that eating and drinking, reaching for objects, writing and personal hygiene are most problematic in daily life and therefore assisting performance of these tasks with supportive devices is of key importance [3]. In addition to control of upper extremity movement, trunk and head control are necessary in accomplishing daily tasks. The interaction between trunk and arm movements is likely most pronounced when reaching to objects beyond arm length distance [4, 5]. However, in healthy children, trunk movement is also seen when performing tasks within arm length distance [4, 6]. Furthermore trunk motions are often needed to maintain postural stability during daily tasks [7]. In healthy children and adults, the head generally shows a countermovement relative to the trunk resulting in a constant head orientation in space [5]. Head movement is also important for visual control of task performance. Maturation affects the interactions between arm, trunk and head movements in children. Interactions in younger children are more variable than in older children [5]. When developing supportive devices for patients with NMD, trunk and head as well as arm movement should be taken into account. Therefore, detailed information is needed about pelvis, trunk and head movement in coordination with armmovements, both in healthy children and in children with NMD. However, literature on these segmental interactions is scarce [8]. In our study, healthy children in the same age range as children with NMD were included to obtain insight in the interaction between upper body segmental movements, prior to studying this in children with NMD. While there is some knowledge on the interactions of the upper body in healthy children, the trunk is mostly regarded as one rigid segment. The movement of the thorax is often measured, with respect to the pelvis or the world, and is seen as representative for the overall trunk movement. However, the trunk has great flexibility and can probably not be seen as a rigid segment for development of dynamic supportive devices. Clearly, for the development of supportive devices or spinal orthoses it is important to have insight in the movement of the trunk in more detail than as a single segment. This information could result in requirements concerning selection