## 4 Discussion  
The aim of the present study was to compare the lower-extremity intra-joint coordination and its variability in fallers and non-fallers older adults during gait. The results showed that there were no significant differences in the hip, knee, and ankle ROMs between the faller and non-faller groups. However, the spatiotemporal parameters were significantly different between the two groups, confirming our first hypothesis about the differences in spatiotemporal gait parameters between fallers and non-fallers. In our study, fallers walked with lower cadence, gait speed, and stride length but greater double support and stride time than non-fallers, indicating a cautious gait pattern adopted by fallers during walking. The decreased cadence and short stride length and greater double support and stride time seen in the faller group may be a consequence of decreased efficiency and an adaptation to decrease the risk of falling. The results of the present study were similar to those of a previous research [35], suggesting that a decrease in stride length, cadence, and gait speed and an increase in stride time are the most common parameters that can distinguish between fallers and non-fallers. Moreover, in 2018, [PERSON] reported that fallers had slower speed, shorter steps, and longer stance phase, with increased double-limb support, than non-fallers [16]. However, our results on spatiotemporal gait parameters  
Figure 4: (**a**) Ankle-to-hip coordination variability (CoordV), (**b**) ankle-to-knee CoordV, and (**c**) knee-to-hip CoordV during gait cycles in fallers and non-fallers. Figure 3: Ankle-to-hip angular displacement diagram (left axis), and frequency of coordination patterns (left axis) in the sagittal plane in fallers and non-fallers[PERSON] The red and green solid lines are angular displacement of knee joint in fallers and non-fallers, respectively[PERSON] The red and green dashed lines are angular displacement of ankle joint in fallers and non-fallers, respectively. The black and green dots are the frequency scatter of coupling angle in fallers and non-fallers, respectively. The black and green bar charts are the frequency percentage of coupling angle in gait cycle in fallers and non-fallers, respectively. were not in line with the results of the studies by [PERSON] in 2017, [PERSON] in 2015, and [PERSON] in 2017, which showed no significant differences in kinematic gait parameters between fallers and non-fallers [12; 36; 37]. The intra-joint coordination pattern of the lower extremity and its variability in the sagittal plane were significantly different between fallers and non-fallers in some instants of the gait cycle. This confirms, to some extent, our second and third hypotheses about significant differences in the intra-joint coordination pattern and its variability in the lower extremity between fallers and non-fallers. Fallers showed a more anti-phase coordination pattern in knee flexion-ankle plantar flexion with ankle dominancy (270-315\({}^{\circ}\)) compared to non-fallers; this is related to the greater knee flexion in all gait cycles and greater plantar flexion in loading response and late swing in fallers (Figure 1). The greater knee flexion in all gait cycles was probably a result of knee extensor weakness in older people with a history of falling. Knee extensors eccentrically control knee flexion during the stance phase of gait [38], and individuals with knee extensor weakness cannot efficiently extend their knee in the stance phase. Moreover, studies on differences between young and older adults showed that the contribution of the hips and ankles increased and decreased, respectively, with aging [39; 40]. Fallers seem to have more ankle plantar flexion during late swing and initial contact to compensate more knee flexion and be more cautious about foot contact with ground. Fallers showed a less in-phase coordination pattern in knee extension-ankle plantar flexion with knee dominancy (180-225\({}^{\circ}\)) in forward progression than non-fallers (Figure 1).