Laura Peeters

Trunk, head and pelvis interactions in healthy children | 69 3 we were interested in self-selected movements of the trunk and hence chose not to standardize initial sitting posture. Second, although the age of the subjects was uniformly distributed over the whole age range, we had only a few participants for each age. Especially because the variability was larger in the younger children, a larger group size would have allowed for a more sensitive analysis of age effects. Third, surface markers were used to identify movement of the segments. Soft tissue movement can result in artifacts in the movement estimation and is a well-known disadvantage of this measurement technique. Especially the soft tissue movement artifacts of the trunk can be quite substantial [21]. However, this influence should be minor when evaluating the range of motion instead of absolute angles according to Zemp, et al. [21]. Last, results of the lumbar segment movement in the younger children should be interpreted with caution, because the markers were placed at a small distance from each other and therefore small artifacts can result in substantial errors. In conclusion, the contribution of individual trunk segments to the ROM varied with the movement plane with specific task aspects such as distance, height and weight handled. Range of trunk movement decreased with age when performing reaching tasks and this should be kept in mind when evaluating the interaction between trunk and upper extremity movements in children. Increased reaching distance, height and object weight all resulted in increased trunk movement in reaching forward and laterally. Generally, the head moved in opposite direction to the trunk (except in the transverse plane when reach laterally), but the head movement strategy was highly variable in the frontal plane and was also dependent on the task performed. Head and trunk movement onsets were generally earlier than arm movement onset when reaching. Only in a few tasks head movement onset was significantly different from trunk movement onset.