5 DISCUSSION AND CONCLUSIONS
5.1 E FFECTS OF FLOOR TRANSITION ON LOCOMOTION
This research project was undertaken to examine the effect of floor material change (transition) on gait and gait stability. In order to better understand how floor transition affects kinematic and kinetics parameters of walking, we observed the locomotion on different floor material conditions and analyzed kinematics variables of gait, and furthermore, the relationship between gait-related variables and COM was examined. As noted in our results, the total medial-lateral excursion of whole-body COM is slightly greater when the subjects walked under the transition conditions than walked on the consistent conditions. We hypothesized that floor materials change would decrease the stability of locomotion, and the results of this study also support the hypothesis.
Because the control of COM movement during walking has been found to be a good indicator of stability (Chou, Kaufman, Brey and Draganich 2001; Chou, Kaufman, Hahn and Brey 2003), and the larger amplitude of COM lateral motion observed in the transition conditions indicate a decrease in gait stability.
Previous research (Bunterngchit, Lockhart, Woldstad and Smith 2000) also suggests that the floor surface (especially the transitional floor surfaces) may increase the potential for slip-induced falls. Although we observed significant gait differences between transition and consistent conditions in young participants, most investigated parameters in the older group did not significantly differ in transition from consistent conditions. In addition to the limited number of older subjects, The insignificant difference might be due to the small difference in COF (<0.1) between two adjacent floor materials consisting the transition condition, and COFs of all employed floor materials are above 0.7 in dry and clean condition.
The results also indicated that walking on transition condition would reduce
foot-ramp angle at heel strike and pelvic anterior tilt angle, and increase required COF. Previous studies indicate that people would reduce required COF to decrease the risk of fall (Bunterngchit, Lockhart, Woldstad and Smith 2000;
Chou, You, Lin, Su and Chou 2000); however, the significantly larger peak-COF following floor transition observed indicates that the gait stability was still reduced, and this may lead to a higher risk of falls (Yang and Hu 2008; Yang and Hu 2009). We also observed decreases in foot angle at heel strike and in pelvic anterior tilt angle when transition from one floor material to anther with lower coefficient of friction. A decreased foot-ramp angle at heel strike was also found when encounter a slippery floor (Chou, You, Lin, Su and Chou 2000; Cham and Redfern 2002), and it might be because the participants walked with caution under transition condition.
The larger ankle dorsi/plantar-flexion angle and less anterior pelvic tilt may be employed to stabilize the body while walking from one floor material onto another with slightly lower coefficient of friction. However, higher peak RCOF could still increase the risk of fall. Moreover, the larger medial-lateral COM excursion also indicated that subject has less stable locomotion under transition condition. Therefore, it is highly recommended to use caution when walking from one floor material to another with different coefficient of friction.
5.2 Variables that could be used for indicating gait stability
The Whole-body COM has been used in many studies as an index of gait stability. However, evaluating COM data needs lots of marker position data.
Enormous anthropometric database and reconstruction of three-dimensional multiple- segment biomechanical models are also needed. In that case, only with complex calculation and high technical skills could obtain a faithful COM data and practical utility of COM in evaluating gait stability would be limited.
Therefore, we would like to know if there is any kinematic or kinetic variable
besides COM could represent the gait stability.
We hypothesized that pelvic motion would express the stability of locomotion. However, the scatter charts of pelvic motion and COM motion in lateral direction (see Figure 22 to Figure 24) showed low covariance (0.0410 of pelvic obliquity, 0.1542 of pelvic rotation, and 0.1557 of pelvic tilt) of these variables. Although pelvic motion was significantly different between transition and consistent conditions, the feasibility of using pelvic motion as an indicator for gait stability is still need to be confirmed with future studies.
5.3 Limitations of the study
Despite the variety of age of participants and the large number of the task, the design of the present study has some limitations. The first one is the lack of diversity of floor materials and the floor combinations in our current study. In this study, we only used three different kinds of floor materials – plane-wood, rough-ceramic, and PVC – to constitute seven experimental conditions. The deficient in floor types caused the shortcoming of classification of COF. Since the study only involved the floor with COF between 0.770 and 0.878, the results cannot discriminate the safe range of COF-difference in two contiguous floor materials. Besides, the small amount of floor types could not represent the general indoor residential floor conditions.
The second limitation is that we did not control the visual feedback during the experiments. Since we were interested in the indoor environments and tried to imitate the environment of home, which people should be familiar with and well aware of the floor materials, we decided to allow subjects see and know the floor condition in advance. However, visual feedback may affect the performance and control of locomotion. The color contrast of two continuous floors might influence the performance of locomotion or decision making for
gait adjustments, even the onset time of the adjustment. The third limitation is that the results of COF measurement might not really manifest the COF between barefoot and floor material. Therefore, the COF in this study would only use as a reference resource which help researchers to quantify the difference of floor materials. The small number of participants is another shortcoming in the study.
Since the study involved only five young participants, one middle age participant and one elder participant, the results might not be general enough.
Thus, the generalization of the results to populations of each age group may be limited. In addition, in our experimental setting and measurements, we could not distinguish active from passive components of the observed gait adjustments when encountering different floor conditions. Recording muscle activation with electromyographic (EMG) and compare the results of EMG with gait parameters might be a way that could specify whether the changes are from the active control or not.
5.4 Recommendations for future research
With above-mentioned limitations of this study, future research is obviously needed in a number of directions, but this is a fascinating beginning to understand the effect of floor materials change on gait stability. It would be beneficial to replicate this study with more and different floor types. In order to present the general indoor floor condition of residence, more floor materials with different COFs should be included to increase the variability of floor combinations. With a wider range of COFs, a safer range of COF-difference in two contiguous floor materials could be determined. Furthermore, the relationship between COF-difference and gait stability would be revealed. To understand more about the effect of floor transition on gait stability in difference age group, we need to repeat the study on larger populations. We also intend to examine gender differences in gait control when encounter floor transition condition.
An additional interesting avenue of investigation is whether the color contrast of two continuous floors would influence the performance of locomotion or decision making for gait adjustments. Since visual feedback plays an important role in motor control, further investigations on the effects of floor appearance and coefficient of friction would be needed.
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Appendix 1 Berg Balance Test
註:下列項目是在站立不扶的情況下測試
0 無法嘗試或需要協助以防止跌倒
總分 (滿分 56 分) 治療師簽名
【無法施測請打“x＂
，並請寫出由於__________________而無法施測】
* From: Physiother Canada 1989;41:304-308.