Laura Peeters

66 | Chapter 3 caudal segments. These difference are likely due to differences in task instructions. Subjects moved their head along with the trunk in our study, whereas they had to touch a reference with their head in the study of Preuss and Popovic [14]. The pelvis also contributed greatly in all movement directions in our maximum trunk movement tasks, indicating that it has a great influence on the maximum trunk movement. In accordance with a previous study [15], trunk movement increases with reaching distance and object weight when reaching forward. In addition, we found that this also applies for reaching laterally and for different reaching heights. Moreover, it applies to most trunk segments and the pelvis in the sagittal plane and for the thoracic segments in the frontal plane. It is noticeable that despite the large standard deviations in ROM, subjects adapt similarly to differences in reaching conditions in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 Movement onset [s] -2 -1.5 -1 -0.5 0 0.5 1 1.5 N-S-0 (n=15) (n=16) N-S-500 (n=19) (n=19) N-E-0 (n=17) (n=15) N-E-500 (n=17) (n=14) F-S-0 (n=20) (n=16) F-E-0 (n=18) (n=19) N-S-0 (n=16) (n=16) N-S-500 (n=18) (n=21) N-E-0 (n=19) (n=18) N-E-500 (n=18) (n=18) F-S-0 (n=18) (n=16) F-E-0 (n=21) (n=21) N-S-0 (n=18) (n=15) N-S-500 (n=19) (n=12) Reach forward Reach laterally Reach contra- lateral Trunk onset Head onset Figure 10 Trunk and head movement onset relative to the arm movement onset for all reaching tasks. Boxes represent 25 th , 50 th and 75 th percentile, wiskers minimum and maximum of non-outlier values, and dots indicate outliers (greater than 1.5 times the interquartile range). * p<0.05 for trunk or head with respect to zero (e.g. arm movement onset), Δ p<0.05 between trunk and head onset. Abbreviations in reaching tasks: N = near target, F = far target, S = shoulder height, E = eye height, 0 = 0 gram object weight, 500 = 500 gram object weight.