Laura Peeters

64 | Chapter 3 Head movement strategies Different head movement strategies were found in the daily activities (figure 9). There was no missing data. Two times the maximum standard deviation of quiet sitting was equal to 2.24° (frontal plane), 2.80° (sagittal plane), 2.02° (transverse plane), and was used as range within the head movement was categorized as none. In almost all tasks, a variety in head movement strategies was used by the participants. Most consistency could be seen in the transverse plane. Axial rotation movement of the head was in opposite direction to the axial rotation of the trunk when reaching forward and contra-lateral (on average across tasks, 88% of the participants), while the rotation was in the same direction when reaching laterally (on average across 0 5 10 15 0 50 100 Frontal plane 0 5 10 15 Head movement strategy [%] 0 50 100 Sagittal plane 0 5 10 15 0 50 100 N-S-0 N-S-500 N-E-0 N-E-500 F-S-0 F-E-0 N-S-0 N-S-500 N-E-0 N-E-500 F-S-0 F-E-0 N-S-0 N-S-500 Plate Draw Drink Dexterity Reach forward Reach laterally Reach contra- lateral Transverse plane No relative movement Same movement as trunk Counter movement trunk Figure 9 Head movement strategies used by the subjects as percentage of the total group when performing daily tasks. The bars indicate no relative movement between head and trunk, relative head movement in the same direction as the trunk movement and relative head movement in opposite direction of the trunk movement. 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.