Laura Peeters

126 | Chapter 6 levels. Therefore, these dynamic systems are promising solutions for interventions to optimize muscle load in DMD and SMA patients when performing daily tasks. Recommendations In this thesis we made the first step towards obtaining a better understanding of trunk function in patients with neuromuscular disorders during UE tasks, but we are still far away from a complete understanding of trunk function in the perspective of different disease stages. A profound MRI study would be the first step to obtain more insight in trunk muscle degeneration patterns in DMD and SMA patients and would help to explain our findings in more detail. Inclusion of DMD and SMA patients with different disease stages, and different types of SMA, will be essential. It is also important to include both superficial and deep back muscles (at different levels) and abdominal muscles to create an overall picture of trunk muscle weakness, which can be related to the movement patterns and muscle activity levels observed. We hypothesized that trunk stability is decreased in SMA patients and is worse in SMA patients compared to DMD patients. To confirm or reject our hypotheses, more research on this topic is recommended. Evaluating trunk stability could be done by measuring center-of-pressure trajectories when being seated on a wobbly chair [47]. However, since SMA and DMD patients can have reduced or absent postural reflexes, insight in the presence, amplitude and timing of the reflexes involved in trunk stability control might be more valuable. This has not been studied before in these patient groups. van Drunen, et al. [48] described a method to quantify intrinsic and reflexive muscular contributions to trunk stabilization by providing force perturbations at the trunk and measuring frequency response functions, kinematics and reflexes (sEMG). But this method likely needs to be adapted slightly to the population at hand, like reducing the perturbation force. Combined with imaging-based information on deep and superficial muscles, this could help to further unravel trunk function, including better distinction between (control of) stability and overall trunk motion. Development of a reliable trunk measurement scale is also recommended, so that trunk function can be evaluated reliably in clinical practice. Evaluating the feasibility and reliability of the Trunk Control Measurement Scale in patients with DMD and SMA can be a good starting point [22]. Additionally, it would be interesting to evaluate whether scores in the ‘dynamic sitting stability’ could be divided into subscores for the ‘trunk only’ tasks and tasks that also include UE movement. Fourth, repeating the measurements performed in this thesis with other patient populations having a flaccid trunk, like (bilateral) CP and SCI, would be of great interest to extract common grounds and crucial differences for interventions. It can also increase our understanding of the interaction between trunk, UE and head