Laura Peeters

116 Chapter 6 and shoulder joint torques were also collected during MVIC. In chapter 3, we aimed to gain insight in trunk, pelvis and head movements when performing UE tasks in 25 healthy children and young adults (6-20 years old). We focused especially on movement of different trunk segments (i.e. upper thoracic, lower thoracic, upper lumbar, and lower lumbar), since the trunk has substantial flexibility but has previously mainly been studied as one rigid segment. We found that contributions of individual trunk segments varied with movement direction and, therefore, with the performed task. The contribution to trunk motion was approximately uniformly distributed across all trunk segments when flexing and decreased from caudal to cranial segments when extending. For lateral bending, the thoracic segments contributed more than the lumbar segments. In axial rotation, movement of the lower thoracic segment with respect to the upper lumbar segment was most important. The pelvis also contributed greatly in all movement directions, indicating that it has a major influence on the maximum trunk movement. Trunk movement significantly increased with reaching height, distance and object weight in the sagittal and frontal planes. This also applied to all individual trunk segments in the sagittal plane and to the thoracic segments in the frontal plane. Similar to the literature, we found that total trunk movement decreased with subject age in childhood when reaching forward and laterally [5, 6]. Age-matched comparison is therefore important in childhood to distinguish between natural and pathologic trunk movements. Head movement was opposite to trunk movement in the sagittal (> 50% of the subjects) and transverse planes (> 75% of the subjects) and was variable in the frontal plane in most tasks. Both trunk and head movement onsets were earlier compared to arm movement onset. Chapter 3 showed that interaction between trunk and UE movement is essential for accomplishing daily tasks in healthy children and young adults. For DMD patients this may be even more important, because clinically they show increased trunk movement to compensate for reduced arm function. Therefore, the aim of chapter 4 was to investigate how DMD patients use trunk movement to compensate for reduced arm function. We hypothesized that the use of compensatory trunk movement is dependent on task difficulty and disease progression, and is related to increased trunk muscle activity. Seventeen boys with DMD participated in this study, and results were compared to the 25 healthy controls (HC) as described in Chapter 3. As hypothesized, we found a significant increase in trunk movement in the frontal and/or sagittal plane in DMD patients compared to HC when performing all tasks. However, trunk movement did not significantly increase with task difficulty (i.e. increasing object weight) or Brooke scale. Normalized muscle activity was significantly higher in DMD patients compared to HC for all tasks and all muscles. On average, normalized muscle activity was almost twice as high for back muscles and 4 times higher for abdominal muscles.