Laura Peeters

Trunk involvement in performing upper extremity activities | 35 2 including more than 30 subjects, were mostly performed on healthy persons [2, 4, 12, 13], although we were able to identify two such studies of patients with SCI [37, 38] and one study including patients with CP [33]. No studies were found on patients with neuromuscular disorders like DMD, SMA or spinal dysraphism/spina bifida. Nevertheless, there were common key findings that will be discussed below. Trunk-head-arm movement during reaching Reaching distance seems to be a crucial factor in choosing a movement strategy for both healthy persons and neurological patients (see Figure 3). Different movement strategies were found for different groups when reaching towards targets within 90% arm length (see figure 3A). Healthy adults showed no trunk flexion [2], whereas healthy children showed some trunk movement [12, 20], and children with CP even more trunk flexion [20, 21, 24, 25, 27, 28]. In contrast, patients with SCI tended to move their trunk backwards [40]. Apparently, different patients use different movement strategies to compensate for their impairments. For instance, it may be easier to accurately perform a reaching task when the arm is not completely extended (due to a smaller moment arm), which implies that more trunk flexion is needed. This strategy is seen in patients with CP, but also to some extent in healthy children. For patients with SCI, the main challenge is to maintain sitting balance while reaching. Hence, stretching out the arm (resulting in a forward center-of-mass displacement) is compensated by trunk extension to maintain balance. Remarkably, Figure 2 Movement directions of the trunk and head when reaching forward at arm length according to the study by Sveistrup, et al. [13]. In the sagittal plane, the trunk flexes in the direction of reach, while the head bends backwards when reaching at arm length or beyond. In the frontal plane, the trunk moves away from the reaching arm, while the head moves either towards or away from the reaching arm. In the transversal plane, the trunk and head predominantly rotate away from the direction of reach in children (> 3 years) and adults.