雙重任務在上下樓梯各時期動作控制與肌群表現的影響

Abstract

跌倒為高齡者日常生活常發生的意外，且十分之一的跌導致死事件發生在樓梯空間中。因此探討上下樓梯跌倒因子，以預防高齡者跌倒發生為重要的議題。在日常生活中，上下樓梯動作同時進行其他動作容易增加跌倒風險，如：與他人聊天、使用手機等。雖然已有廣泛相關生物力學研究探討平地行走與站姿平衡下雙重任務對動作控制之影響，但仍較少提及上下樓梯受雙重任務影響之現象。因此，本研究目的為探討上下樓梯時各時期動作表現受雙重任務影響情形，觀察在上下樓梯動作中，認知任務與動作任務對其步態表現、肌群活化情形、肌群共縮關係所造成的影響。本研究假設，雙重任務下，額外的動作任務與認知任務的干擾皆會對樓梯動作表現與肌群活化情形造成影響。其次，在上下樓梯動作中，不同時期所需要的專注力有所不同，使肌群在各時期受雙重任務影響表現變化情形有所不同。 本研究實驗中，主要招募12位年輕人(22-26歲)在四種情境下(正常上下樓梯、減法算數、時鐘辨識、手持水杯)各進行7次上下樓梯動作，並額外招募2位中高齡者，初步觀察不同年齡層的變化情形。在上下樓梯動作中，使用加速規與肌電訊號設備記錄步態時間參數與各時期下肢肌群積分值(IEMG)、肌群共縮值資料。本研究將一完整步態分為腳觸地前期、站立期、雙腳站立期與擺盪期分別比較受雙重任務下的影響結果。結果顯示，本研究所設置之認知任務與動作任務對其時間步態、肌群積分值、肌群共縮值參數在各時期有影響，年輕人時間歩態在各時期增加6-12%。此外，肌群積分值在不同時期下受雙重任務影響有不同的變化趨勢，年輕人族群在擺盪期下股內側肌(vastus lateralis)與腳觸地前期的股外側肌(vatsus medialis)、股二頭肌(biceps femoris)、脛骨前肌(tibialis anterior)、外側腓腸肌(gastrocnemius lateralis)與臀大肌(gluteus maximus)肌群積分值受雙任務影響下降5-26%；而外側腓腸肌在站立期與雙腳站立期受雙重任務影響增加5-24%，其代表專注力需求在不同時期有所不同。此外，兩位高齡者的步態參數與肌群積分值在手持水杯下没有顯著差異，顯示其動作策略與年輕人有所不同。綜觀上述結果，在上下樓梯中同時進行認知任務或動作任務將會增加跌倒的風險，且族群間有不同的動作策略。此外，不同時期現所需要的專注力需求量有所不同，故本研究建議未來在相關跌倒感測與老年人訓練應用上，需考慮動作在不同時期專注力需求大小，以預防跌倒發生。

Falling is a common accident among older adults’ daily living, and 10% of fatal fall occur on stair. Therefore, it is an important issue to discuss risk factors for stair fall in older adults. Stair climbing while doing a concurrent task like talking or using cell phone would cause high risk for fall in our life. Most researchers extensively focused on the effect of dual task on biomechanics during ground level walking or postural control. However, there is lack of research on discussing the impact of dual task on movement control of stair negotiation. Hence, the aim of our study was to determine the effect of dual ask on temporal parameters, integrated electromyography (IEMG), and muscle co-contraction of gait when performing a concurrent cognitive or motor task during stair negotiation. We hypothesized that the performance of stair climbing and muscle IEMG would be affected by the interference of dual task. Secondly, we hypothesized that the attention demand would vary depending on phases leading to different variation in muscle activation during dual-task stair negotiation. In our experiment, twelve young subjects (22-26 years of age) performed seven trials of stair climbing in four conditions including normal stair climbing, with clock task, with subtracting seven, with holding a glass of water. We also recruited two older adults for preliminary discussions on aged effect. The temporal parameters, IEMG, and muscle co-contractions were recorded by accelerators and EMG system. We determined the effect of dual task in different phases by dividing the gait cycle into pre-loading phase, stance phase, double stance phase and swing phase. Our results showed that both the concurrent cognitive and motor tasks would have impact on our gait performance, muscle activation, and muscle co-contraction in each phase. The duration of gait performance have increased 6% -12% in young adults. In addition, , the variation of IEMG have distinct trends on different phases in stair climbing. In younger group, the IEMG of vatsus medialis in swing phase and five muscle groups (vatsus medialis, biceps femoris, tibialis anterior, gastrocnemius lateralis, gluteus maximus) in pre-loading phase decreased 5%-26% significantly during dual tasking. In contrast, the gastrocnemius lateralis increased 5%-24% of its muscle activity in the whole stance phase and double stance phase during dual task performance. There results suggest that there would be different attentional demands in each phases during stair climbing. Moreover, different strategy were found between younger and older adults during stair negotiation with holding a glass of water. In conclusion, doing a concurrent task during stair climbing could increase the risk of falling and there might be different strategy between various aged groups. In addition, the attentional demands varied on different phases during stair climbing. For preventing falling in the elderly, we suggest that the attention demand in each different phase should be considered when designing the fall detector or training protocols for older adults.