Laura Peeters

General discussion |127 6 movements when performing tasks. However, from a pilot study with three boys with CP (Gross Motor Function Classification Score [49] 3 and 4) we learned that the developed measurement protocol should be adapted to the patient population. The CP participants had problems with selective trunk control, which is known from literature [50, 51]. Selective movement control is essential for proper execution of the MVIC tasks. Often compensatory trunk movements were observed and it was sometimes difficult to determine whether these occurred because of the impairments in selective movement control or because instructions were misunderstood. The reliability of the measured muscle strength was therefore questionable and consequently the reliability of the maximum sEMG signals too. This implied that the sEMG signals during task performance could not be normalized. Since normalized sEMG signals are necessary to compare participants, alternatives have to be found for using the MVIC tasks in children with CP, like normalization based on a specific task. The disadvantage of this method is that the maximum contraction amplitude cannot be determined and a task should be selected that can be performed correctly by all participants (taken into account contractures and spasticity) [52]. Finally, research should be extended to the influence of the pelvis and the lower limbs on trunk movement, stability and the performance of daily tasks. Effect of cushions on pelvis and trunk movement can be examined, as well as effects of complete fixation of the pelvis in different patient populations. For the contribution of the legs, research should combine ground reaction force measurements with sEMG of the legs and trunk, to disentangle active and passive components. This knowledge will be crucial in the light of seating adjustments and positioning in the wheelchair in order to support people as well as possible in their daily activities.