## 4 Discussion  
The present study aimed to investigate the effect of the amplitude of turning on whole-body coordination during standing turns in healthy older adults in comparison to younger adults and to observe the impact of turning amplitude on whole-body coordination and stepping characteristics. We expected to see systematic changes in the characteristics of turning kinematics and stepping behavior. However, only step duration and turn speed were found to differ significantly between older and younger adults. Other variables appeared to be modulated identically in both groups during the differences in turn amplitudes. It is important to note that the data shows that an increase in turn amplitude had a significant effect as regards segment onset latencies (head, thorax, pelvis and feet), peak segments angular separation, stepping characteristics, and also turning speed in the older adult group in comparison to the younger adult group. Our study found that the larger turn amplitude significantly affected the order of the reorientation of mean onset latency by delaying the onset of all segments. This delay was consistent between turns to each amplitude, as was segmental onset latency, suggesting that onset latency of segments is regulated by a central nervous system (CNS) regulatory synergy [14; 15]. In addition, onset latency of segments in our study consistently shows a top-down sequence which starts with the head and proceeds to the trunk, pelvis, leading foot and trailing foot [12; 16; 17; 18; 19], which indicates that a motor program for movement may  
Figure 5: Bar graph showing the effect of group and turn amplitude on turn speed variable. Values are mean \(\pm\) SEM. \(\blacklozenge\)Denotes a significant interaction (\(p<0.05\)) from Mixed Model Analysis of Variance. \({}^{*}\)Denotes post hoc pairwise comparisons of turning amplitudes within group from Repeated Measure Analysis of Variance. \({}^{**}\)Denotes main effects of group and amplitude from Mixed Model Analysis of Variance. be altered to handle similar motor activities in order to maintain balance and ongoing movement [15, 20]. This would also imply that the CNS has a dominant control synergy schema, with the CNS employing the upper body to guide lower-body responses [21]. It stands to reason that the whole-body coordination strategy might have an effect on turning abilities. When the path of movement is disrupted increasing the turning amplitude allows the motor cortex and motor planning more time to absorb sensory information and deliver correction orders to stabilize the body. Turning amplitude only impacts a small portion of the age-phase shift connection, and segment onset latency may not always be the best explanation of turning characteristics in healthy older and younger adults. However, a limitation of this study is that we did not measure eye movements which are described as a trigger of whole-body coordination in both standing and walking turns which could impact on the completion of turning [12, 15]. In future work, the characteristics of eye movement need to be evaluated to clarify the effect of changing amplitude during turning. In this study, we found a significant main effect of turn amplitude (\(p<0.001\)) for peak head-thorax angular separations. In addition, significant main effect for both groups (\(p<0.001\)) and turning amplitude (\(p<0.001\)) were found on peak head-pelvis angular separations. Previous studies found that an en-bloc strategy has been observed in terms of a reduction in head on trunk rotation and a delay in the initiation of body segment rotation during 360\({}^{\circ}\) turns in older adults [14, 16]. It has been suggested that the en-bloc strategy during turning may be adjusted increasing control and compensation in cases of decreased stability and impaired balance in older adults [3] and individuals with movement disorders such as Parkinson's disease [14].