以不同速度於平地與跑步機行走時人體平衡控制策略與動態穩定之比較

Comparisons of Human Balance Control Strategy and Dynamic Stability Between Over-Ground and Treadmill Walking at Different Speeds

盧炫綸(Hsuan-Lun Lu)

指導教授 ： 呂東武

國立臺灣大學/工學院/醫學工程學研究所/博士(2016年)

https://doi.org/10.6342/NTU201603748

摘要

老化導致平衡能力降低使得活動度受到限制，因而提高跌倒之風險。走路為人體神經肌肉骨骼系統以最低層級之自主認知控制下，整合失狀面與額狀面之控制所達成之動態平衡。因此，個人之自選行走速度高低亦反應了其系統性整合下動態平衡之能力。當該能力降低或喪失時，透過跑步機為基礎之復健通常可提供不錯之成效。然而，過去研究對於跑步機走路與平地走路間平衡控制之差異性尚未有一致看法，跑步機上復健之成效如轉移至日常平地走路更保留著模糊地帶。另一方面，過去研究指出，自選行走速度變慢與其跌倒風險有高度關聯性，行走速度對人體平衡控制之影響亦尚待釐清。有鑒於此，過去研究經常透過人體質量中心相對於足底壓力中心之傾角與傾角變化速率描述人體平衡控制，並將人體擬為一動態系統，並可透過連續相對相位角來描述其系統之協調程度。基於動態系統理論，不同週期之連續相對相位角曲線間之偏差值，以及描述量測動態系統之訊號發散程度之最大李亞普諾夫指數，皆為可用於評估動態穩定性之指標參數。因此，本研究以傾角與傾角變化速率比較跑步機走路與平地走路平衡控制之差異，並評估走路速度對人體平衡控制之影響。而連續相對相位、相位角偏差與最大李亞普諾夫指數則用於評估行走速度對協調與動態穩定性之影響。

本研究收取15位健康男性年輕受試者，身上各黏貼39顆紅外線反光球，分別以五種、三種速度行走於測力跑步機與測力板步道，其中皆包括一相同之自選行走速度。反光球軌跡藉由8台立體紅外線攝影機捕捉，並以13連桿模型計算行走時人體質量中心位置。足底壓力中心位置則分別透過一精準校正之測力跑步機與3塊測力板計算得知。其結果顯示，人體以相似之平衡控制模式與協調模式行走於跑步機與平地，且不受到行走速度之影響。然而，平衡控制之差異性依舊可於相似之模式中發現，於腳跟著地時額狀面被動控制與失狀面主動控制受到跑帶影響，使得人體於力學條件較不佳之狀態下行走於跑步機。基於人體質量中心相對於足底壓力中心之傾角與傾角變化速率之平衡控制之發現，自選行走速度似乎為維持單腳站立週期額狀面穩定與雙腳站立週期重心轉換流暢度最佳之折衷狀態。因此，自選行走速度時擁有最佳之動態穩定性，這樣的結果，有助於解釋人體於自選速度下行走時為何最省能量。速度對於平衡控制、協調與動態穩定性之影響，可提供臨床人員對應訓練需求，挑選平衡訓練時適當之行走速度設置條件。然而，基於本研究之發現，平地走路與跑步機走路之異同可提供未來臨床訓練規範之設計基礎，使跑步機上復健之成效能最佳化地轉移至日常平地走路。

關鍵字

人體平衡控制 ； 協調 ； 動態穩定性 ； 質量與壓力中心之傾角 ； 連續相對相位 ； 相位角偏差 ； 最大李亞普諾夫指數

並列摘要

There has been a general awareness that aging comes with increased risk of falling, induced by a poor balance and consequently mobility restrictions. Human walking requires minimal higher-level cognitive input but multi-level physiological sub-systems to maintain dynamic balance, suggested by an integrative control that an active control in the frontal plane but passive control in the sagittal plane. A preferred walking speed (PWS) is then reflected in one’s ability coordinate these sub-systems. For people who have less ability to maintain such a dynamic stability, treadmill-based trainings are usually recommended in clinical settings. However, there has not been a consensus over the differences in the balance control between treadmill walking (TW) and over-ground walking (OW). While a reduction of one’s PWS has been shown to correlate an increasing risk of fall in the elderly, speed effects on the body balance control remains still unclear.

Describing the position and velocity of the body’s center of mass (COM) with respect to the center of pressure (COP), in terms of COM-COP inclination angles (IAs) and their rate of change (RCIA), provides useful information to investigate dynamic balance control during movements. Such balance control is quite complex underlying, which was regarded as a dynamic system. Inter-segment coordination was usually addressed by continous relative phase angle (CRP) determined by two phase plots of the targets in a dynamic system. The control stability in such dynamic system was frequently assessed by variability-based measurements, i.e., deviation of the phase angle (DP), and the maximum Lyapunov exponent (λ_s). Therefore, the purposes of the current dissertation were to compare the similarities and differences in balance control between TW and OW; to investigate the speed effects on the body balance control strategies during TW and OW, in terms of IA/RCIA related variables; to investigate the speed effects on the body balance coordination and dynamic stability in controlling sagittal and frontal COM motion relative to the COP both during TW and OW, in terms of deviation of continuous relative phase angle (CRP), deviation of phase angle (DP) and short-time maximal Lyapunov exponents (λ_s).

Kinematics of the COM and COP in fifteen healthy adults at five belt speeds and three gait speeds, including the subjects’ PWS, was determined using a motion capture system, an instrumented treadmill and forceplates. The current findings suggested that human adapted similar dynamic postural control both during TW and OW, as indicated by the comparable patterns in the balance control of the COM motion relative to the COP. The similarity was also addressed in the coordination between frontal and sagittal COM motion relative to the COP, similar CRP curves were observed regardless of walking speed both for TW and OW. Despite these similarities, when compared to OW, a positive control in the sagittal IA at heel-strike and an active control in the frontal RCIA at toe-off were shown during TW. By adapting the control strategies, PWS appeared to be the best compromise between frontal stability during single-limb support and smooth weight-transfer during double-limb support. As a result of such compromise control, highest dynamic stability was found when subjects walked at their PWS both for TW and OW. These findings might help to explain that why PWS is regarded as a well-recognized locomotor that minimizes the energy expenditure. As the speed effects on the balance control and dynamic stability revealed in the current dissertation, selection of training speeds might be subject to the needs for the target population in the rehabilitation protocol. Nonetheless, these differences between TW and OW may have to be taken into account in future designs of strategies to optimize the translation of treadmill gait training outcomes to real life over-ground walking.

並列關鍵字

balance control ； coordination ； dynamic stability ； COM-COP inclination ； continuous relative phase ； deviation of phase angle ； maximal Lyapunov exponent

參考文獻

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