Age and Falls History-Related Differences in the Biomechanics of 360º Pivot Turns

INTRODUCTION: Older adults who fall during turning are eight times more likely to experience a hip fracture than from a fall during walking in a straight line [1]. The ability to turn has been identified as an important task of daily living, and the evaluation of turning has been included in many clinical assessments to determine those at risk of falling [2- 4]. Therefore, the comparison of turning biomechanics in fallers and non-fallers in the older population is essential if we are to understand the mechanisms underlying falls. The aims of this study were to compare time to turn, number of steps utilised to turn, and segmental reorientation onset in groups of young adults and older non-fallers, single fallers and multiple fallers during a 360º standing turn METHODS: Fifteen young adults (age 25.7 ± 3.2 years), and older non-fallers (n = 15, age 70.7 ± 6.2 years), single fallers (n = 11, age 70.2 ± 6.1 years) and multiple fallers (n = 14, age 71.5 ± 6.9 years) participated in this study. Participants completed three 360º turn trials at their own speed, and the participants self-selected their turning direction to make the movement as natural as possible. A 14- camera Vicon M2 (624) system was used to collect 3-D marker trajectory data sampled at 60 Hz, and the head, thorax and pelvis segments were defined. Thoracic and pelvic onset latencies were calculated with respect to head rotation onset, and pelvic onset latency with respect to thoracic rotation onset was also calculated. Group differences were investigated using one-way ANOVA. RESULTS: The young adults completed the turn in significantly less time than the multiple fallers (F = 3.636, p = 0.019), and utilised significantly fewer steps to turn (F = 3.693, p = 0.018). All of the participant groups demonstrated head yaw as the first movement in the initiation of the 360º turn. There was a significant difference between groups for pelvic turn onset latency with respect to the thorax (F = 5.968, p = 0.001), post-hoc tests showed the multiple fallers to have significantly shorter latency between the thorax and the pelvis than all other groups. CONCLUSIONS: The multiple fallers demonstrated a more en-bloc strategy for turning than the other groups characterized by a shorter latency between reorientation onset of the thorax and the pelvis at the initiation of the turn. Interestingly, en-bloc turning strategy of the thorax and pelvis has been previously observed in both stroke and Parkinson disease patients; patient groups who also are at increase risk of falling during turning. In combination these results suggest that studying the biomechanics of pivot turns is a useful tool for elucidating the mechanisms underlying falls and diagnosis of increased falls-risk