Laura Peeters

94 | Chapter 5 ABSTRACT Objective : To investigate trunk function during seated upper extremity tasks in patients with spinal muscular atrophy (SMA) type 2 and 3. Design : 17 persons with SMA and 15 healthy controls (HC) performed several tasks when sitting unsupported, such as reaching (and placing) forward and sideward. Joint torque and muscle activity were measured during maximum voluntary isometric contractions (MVIC). Three-dimensional kinematics and normalized muscle activity were analyzed when performing tasks. Results : Trunk joint torques were significantly decreased, approximately 45%, in patients with SMA compared to HC. Active range of trunk motion was also significantly decreased in all directions. When performing tasks, the average back muscle activity was 27% and 56% of MVIC for respectively HC and SMA, and for abdominal muscles respectively 10% and 44% of MVIC. Trunk range of motion did not differ when performing daily tasks. Conclusion : The trunk of patients with SMA is weaker compared to HC, reflected by reduced trunk torques and decreased active range of motion. Additionally, patients with SMA use high percentages of their trunk muscle capacity to perform tasks. Clinicians should take this into account for intervention development, because using high percentages of the maximum muscle capacity results in fatigue and muscle overloading.