UPPER BODY AXIAL ROTATIONS IN DIFFERENT AGE-GROUPS DURING LEVEL WALKING.

High amplitude of movements in the lower body during walking is attenuated in the upper body to stabilize the head, which serves as the platform of critical sensory systems (vestibular and visual). The upper body attenuation has been investigated on the linear acceleration, however, not on the angular motion. This study aimed to compare the attenuation of axial rotation in different age-groups. Methods: Thirty healthy men (15 young and 15 elderly) participated in this study. Subjects walked on a level surface with gyro sensors attached at four locations of the back (pelvis, thorax, shoulder, and head), from which the angular motion was derived. Outcome measures included the average peak-to-peak amplitude of axial rotation at all sensor locations and the phase delay at each location with reference to the pelvis. Results: Age-position interaction was significant for both the amplitude and phase delay. Post hoc test revealed that rotation amplitude was similar at pelvis, thorax and shoulder in the elderly, whereas it was significantly reduced at the thorax-shoulder section in the young. The elderly also showed smaller phase delay at shoulder and head than those of the young. Discussion: The results suggest that the attenuation by upper trunk was reduced and the shoulder and head motions were more tightly coupled to the pelvis in the elderly, i.e., the upper body moved more like a rigid body in the axial motion. [ABSTRACT FROM AUTHOR]