高能量聚焦磁場合併足部核心訓練對功能性扁平足族群之足部動態功能的影響

Abstract

研究背景：足部核心系統分為主動、被動和神經三個次系統，功能性扁平足族群因足部核心系統功能不足，使足部穩定性降低，增加累積性傷害的風險。足部動態功能測量能夠呈現動態情境下的生物力學特徵，因此對足部或下肢傷害可以提供更完整且客觀的評估。足部核心訓練透過徵召足掌內肌收縮，強化足部核心之神經次系統及主動次系統，然而足掌內肌選擇性收縮困難，對足弓高度改善效果有限，因此，利用神經肌肉電刺激能夠增進足部核心訓練的效果。高能量聚焦磁場技術已被證實能促進肌肉生長、增強肌肉功能，並且作用機制可避免電刺激所產生的副作用，目前尚無研究探討此技術在足掌內肌的應用。 研究目的：本研究目的為應用高能量聚焦磁場合併足部核心訓練對足掌內肌進行訓練，探討對扁平足族群足部動態功能的介入成效。另外，透過靜態量測與動態足部測量，探討高能量聚焦磁場合併足部核心訓練分別對足部核心系統主動、被動和神經次系統的效應。 研究方法：本研究招募30位功能性扁平足受試者，隨機分成三組，分別進行高能量聚焦磁場合併足部核心訓練、高能量聚焦磁場、偽高能量聚焦磁場合併足部核心訓練。高能量聚焦磁場每次20分鐘，足部核心訓練包括四種運動，每種運動一組10回、一次三組，每週兩次，總共介入六週。於介入前後，檢測行走時足底負荷與外展拇肌肌電訊號、足掌內肌型態以及靜態足部姿勢。統計方法使用廣義估計式，分析6週介入後，各組在足部負荷參數、足掌內肌型態學參數、外展拇肌肌電訊號及靜態足部姿勢的改變，顯著水平α設為0.05。 研究結果：高能量聚焦磁場合併足部核心訓練組的前足內側峰值壓力（95%CI: -20.75 N/cm2 ~ -7.09 N/cm2, p<0.001）、最大受力（95%CI: -0.72 kg ~ -0.12 kg, p=0.006）、壓力時間積分（95%CI: -0.97 N*min/cm2 ~ -0.30 N*min/cm2, p<0.001），大拇趾峰值壓力（95%CI: -18.70 N/cm2 ~ -3.47 N/cm2, p=0.004）、壓力時間積分（95%CI: -0.88 N*min/cm2 ~ -0.24 N*min/cm2, p=0.001），以及前足外側最大受力（95%CI: -0.69 kg ~ -0.11 kg, p=0.007）顯著較高能量聚焦磁場組減少，壓力中心偏移指數（95%CI: 1.14% ~ 2.68%, p<0.001）較高能量聚焦磁場組顯著增加；偽高能量聚焦磁場合併足部核心訓練組前足外側最大受力（95%CI: -0.62 kg ~ -0.04 kg, p=0.026）也顯著較高能量聚焦磁場組減少。足掌內肌型態學、外展拇肌肌電訊號及靜態足部姿勢無交互作用亦無組間差異，僅高能量聚焦磁場合併足部核心訓練組在介入後，外展拇肌肌電訊號在擺盪前期顯著提升（95%CI: 6.79% ~ 40.80%, p=0.006）。 結論：高能量聚焦磁場合併足部核心訓練較高能量聚焦磁場顯著減少足部負荷壓力，顯示足部核心訓練合併高能量聚焦磁場刺激足掌內肌，在6週訓練後，顯著活化外展拇肌，比起只有高能量聚焦磁場刺激足掌內肌可以顯著減少功能性扁平足步行時前足內側(大拇指)壓力。本研究證明功能性扁平足同時使用高能量聚焦磁場合併足部核心訓練，6週訓練對神經次系統得到明顯改善，有效促進扁平足動態功能。

Background: The foot core system consists of three subsystems which are active, passive, and neural subsystems. Individuals with pronated foot suffer from compromised foot stability due to an inadequate foot core system, thereby consequently increasing the risk of cumulative injury. Dynamic foot function measurements elucidate biomechanics of the foot in dynamic situations, contributing to a more comprehensive assessment of lower limb injuries. Foot core training enhances neural and active subsystems by recruiting intrinsic foot muscles. However, it is found that the difficulty in selectively contracting the intrinsic foot muscles leads to ineffectiveness in changing arch height following foot core training. Therefore, the neuromuscular electrical stimulation is used to improve the effectiveness by selectively stimulating intrinsic foot muscles. High-intensity focused electromagnetic technology has been shown to promote muscle growth, improve muscle function, and reduce the side effects of electrical stimulation. However, there is a lack of studies investigating the application of this technology targeting the intrinsic foot muscles. Purpose: The aims of this study were to use high-intensity focused electromagnetic technology combined with foot core training targeting the intrinsic foot muscles, to investigate the efficacy on dynamic foot function in individuals with pronated foot. Additionally, static measurements and dynamic foot function evaluation will be conducted to explore the effects of the combined intervention on the active, passive, and neural subsystems of the foot core system. Methods: This study recruited 30 participants with pronated foot and randomly assigned them to three groups that were high-intensity focused electromagnetic combined with foot core training group, high-intensity focused electromagnetic group and sham high-intensity focused electromagnetic combined with foot core training group. High-intensity focused electromagnetic was performed 20 minutes per session, and the foot core training consisted of four exercises with 10 repetitions per set and three sets per session for each exercise. All participants received the interventions twice a week for six weeks. Plantar load and electromyographic signals of abductor hallucis during gait, ultrasonography for morphological analysis of intrinsic foot muscles, and static foot posture were evaluated at the baseline and six weeks after the intervention. Generalized estimating equations (GEE) was used to compare the pre- and the post-intervention measurements across the three groups, assessing both between-group and within-group interactions. The level of statistical significance was set at α=0.05. Results: High-intensity focused electromagnetic combined with foot core training group showed significant reduction in peak pressure (medial forefoot: 95%CI: -20.75 N/cm2 ~ -7.09 N/cm2, p<0.001; hallux: 95%CI: -18.70 N/cm2 ~ -3.47 N/cm2, p=0.004), maximal force (medial forefoot: 95%CI: -0.72 kg ~ -0.12 kg, p=0.006; lateral forefoot: -0.69 kg ~ -0.11 kg, p=0.007), pressure-time integral (medial forefoot: 95%CI: -0.97 N*min/cm2 ~ -0.30 N*min/cm2, p<0.001; hallux: 95%CI: -0.88 N*min/cm2 ~ -0.24 N*min/cm2, p=0.001) and increase in center of pressure excursion index (95%CI: 1.14% ~ 2.68%, p<0.001) compared to high-intensity focused electromagnetic group. Sham high-intensity focused electromagnetic combined with foot core training group showed significant reduction in maximal force (lateral forefoot: 95%CI: -0.62 kg ~ -0.04 kg, p=0.026) compared to high-intensity focused electromagnetic group. There were no group-by-time interactions in electromyographic signals of the abductor hallucis, intrinsic foot muscle morphology and static foot posture. Only high-intensity focused electromagnetic combined with foot core training group showed an increase in electromyographic signals of abductor hallucis after the intervention (95%CI: 6.79% ~ 40.80%, p=0.006). Conclusion: High-intensity focused electromagnetic combined with foot core training group showed a significant improvement in plantar load compared to high-intensity focused electromagnetic group, indicating enhancing the active and neural subsystems lead to better outcomes. High-intensity focused electromagnetic combined with foot core training group exhibited significant increases in electromyographic signals of the abductor hallucis. This demonstrated that combined approach effectively improved the active and neural subsystem respectively, thereby enhancing the dynamic foot function.