浴缸內外高低差對進出浴缸動作跌倒風險的影響

Abstract

高齡化社會中，跌倒所衍生的相關傷害及其所花費的社會醫療資源對高齡者自身及整個社會而言，已成為一重要的議題。有關於高齡者的跌倒多發生於室內，且有相當比例發生於浴室。在眾多於浴室執行的日常生活動作當中，進出浴缸除造成高齡者的不便外，亦招致了跌倒的風險。環境因子與跌倒發生的可能息息相關。在進出浴缸時，浴缸內外的高低落差為一常見的環境因子，而此環境因子對進出浴缸跌倒風險的影響卻鮮被提及，此外，跨越厚度對跌倒風險的影響亦未被釐清。有鑑於此，本研究以生物力學的角度出發，討論在進出浴缸時，不同內外高低差及跨越厚度對動作穩定性及跌倒風險的影響。在第一階段的實驗當中，根據市面上常見浴缸的尺寸，本研究給予了90mm、140mm及190mm的內外高低差做為測試條件並比較無內外高低差時的表現。本研究利用八台攝影機所組成的動作擷取系統、兩塊力板及肌電訊號設備量測受測者於跨越時的運動學、動力學資料及肌群活化狀態。共有六位受測者，每位受測者以自身習慣的速度在四種不同條件下進行進出動作，每一個條件進行五次重複的試驗。實驗結果顯示，較大的高低差在進出浴缸時，會使得受測者採取較保守的控制策略。此外，在出浴缸時，與無內外高低差時的表現相較，較大的高低差將會造成跨越腳著地時，身體質量中心與壓力中心在前後方向傾角上升約43-50%，而在側向方向傾角上升了25-28%，顯示動作的穩定程度下降。較大的高低差亦分別造成進出浴缸有較大的絆倒風險及滑倒可能。而關於肌群表現的部分，在出浴缸時，較大的內外高低差將使得跨越腳臀中肌及外側腓腸肌有更大的活化情形，而進浴缸時，則會使得臀中肌、股外側肌及外側腓腸肌在不同的時期下各自有著更大的活化情形。而在第二階段的實驗當中，亦招募六名受測者，在無高低差及140mm內外高低差、140mm及280mm跨越厚度兩兩組合而成的四種條件下，比較兩種因子對動作穩定性及跌倒風險的影響。結果顯示，較大的內外高低差及較厚厚度皆會使得跨越腳著地時，前後方向的人體質量中心與人體壓力中心傾角變大，造成前後方向動作較不穩定。而在側向方向，較大的內外高低差將會使得跨越腳著地時，側向方向的傾角上升，造成較低的側向動作穩定性。綜觀上述結果，浴缸的內外高低差將可能造成進出時有較大的跌倒風險，而厚度亦為一影響跌倒風險的因子。故本研究建議未來在進行浴缸的配置及設計時，除應採取無內外高低差的設置外，也須考慮厚度的配置。

In an aged society, fall related injuries and socioeconmic costs are serious public health issues. Falls in relation to the elderly mostly occur indoors and a significant proportion of those take place in bathroom. Among nemerous activities of daily living performed in bathroom, bathtub entering and exiting movements not only cause inconvenience for the elderly but also bring about risks of falls. Environmental factors is highly correlated with risks of falls. As entering and exiting bathtubs, height difference is a common yet frequently neglected environmental factors when consider risk factors of falls. Besides, how depth of tub apron affects crossing movement still need to be reveal. Hence, our study aims to examine effects of height difference and depth of tub apron on fall risks of bathtub entering and exiting movements. In first stage, based on geometric size of bathtubs prelevant on markert, our study provided 90mm,140mmm and 190mm three height-difference conditions for the experiment. Beside, we compared level conditon with each condition for further interpretation. A eight-camera motion capture system and two force plates were used to obtain kinematics and kinetics during entering and exiting movements; activation of muscle was recorded by EMG system. Six male subjects completed 5 trials in four height-difference conditions with self-selected pace. Our results showed that the larger height difference tend to make subjects exhibit a significantly more conservative strategy when entering and exiting. In addition, when exiting bathtubs, the larger height difference induced inclination angle between center of mass and center of pressure in anterior-posterior, medial-lateral direction increasing 43-50% and 25-28% respectively. This indicated subjects had less dynamic stability. The larger height difference also caused higher risks of trip falls and slip falls for entering and exiting movements. As for activation of muscle, the larger height difference made Gluteus medius and Gastrocnemius lateralis of leading leg become more acivated while exiting bathtubs. In contrast, as entering, Gluteus medius, Vastus lateralis and Gastrocnemius lateralis became more activated in different phase as height difference increased. In second stage, we provided level and 140mm height difference along with 140mm and 280mm depth of tub apron four conditions to testify the effect of height difference and depth of tub apron on fall risks of crossing movement. The results showed that both height difference and depth of tub aporn will lead to larger inclination angle in A/P direction, reducing movement stability. In M/L direction, only height difference will result in larger inclination angle, making subjects have less dynamic stability. In conclusion, for providing a safer living environment of the elderly, we suggest that height difference should not be included as configuring or designing bathtubs. Beside, depth of tub apron also need to be regulated.