Laura Peeters

96 | Chapter 5 hand to the mouth and could sit independently (without back or arm rests) for at least 5 minutes. Patients also needed to have a genetically confirmed diagnosis of SMA. Participants were excluded if they had (other) diseases affecting arm, trunk or head movements. The fifteen HC were a sample of the HC group described previously [9]. Since our participants with SMA were mainly adults, we selected only HC above the age of 12 years to eliminate the maturation effect (e.g. coordination between trunk and arm movements changes in children up to the age of 10 years) as previously described [9, 12]. For the same reason, the 6-year old participant with SMA (SMA_6y) will be described and compared separately with 3 HC of 6 years (HC_6y) as a case study. Participants with SMA were recruited through advertisements by patient organizations (Spierziekten Nederland and Prinses Beatrix Spierfonds) and through the Radboudumc outpatient clinic Nijmegen. HC were recruited from local primary schools, high schools and university. Written informed consent was given by all participants prior to participation. The study was approved by the medical ethics committee Arnhem- Nijmegen (NL58988.091.16) and all data were handled according to the guidelines of good clinical practice. This study conforms to all STROBE guidelines and reports the required information accordingly (see Supplementary Checklist). Procedures We used the same procedure as that employed in a previous study with healthy children [9]. All participants were seated on a height adjustable chair without back- or armrests. The sitting height was adjusted so that the knees were flexed 90 degrees and both feet were flat on the ground. First, to determine maximum trunk range of motion, participants were asked to perform a maximum active flexion movement of their trunk from a seated position, immediately followed by a maximum active extension movement of their trunk (keeping both feet on the ground). The same was done for maximum axial rotation and lateral bending. Thereafter, several reaching (and placing) tasks were performed with a preferred hand at shoulder height: reaching forward, sideways and contra- laterally. Reaching distance and object weight were varied, resulting in the following combinations for forward, lateral and contra-lateral reaching: nearby-0 gram (“N- 0”), nearby-500 gram (“N-500”), far-0 gram (“F-0”). Contra-lateral reaching was not performed at a far distance. Nearby was defined as the distance that could be reached with the arm without moving the trunk (i.e. 100% arm length for HC, but could be closer for SMA) and far was defined as 133% of arm length when possible, otherwise as maximum reaching distance. Furthermore, subjects were asked to perform two daily tasks: displace a porcelain plate (circa 600 grams) from left to right on a table