Changes in Stiffness of the Gastrocnemius Muscle-Tendon Unit After Stretching Exercises
|Keywords:||腓腸肌;伸展運動;硬度;彈性超音波影像;gastrocnemius muscle;stretching exercise;stiffness;shear wave elastography||Issue Date:||2016||Abstract:||
腓腸肌肌肉肌腱複合體需有足夠的柔軟度來協助完成日常活動或運動動作而不致產生傷害；因此早期學者建議運動前作靜態伸展來暖身，可以降低傷害的發生。近年來有學者發現在靜態伸展會造成最大肌力與運動表現能力的下降而提倡動態伸展。然而這類論文多半直接量測最大肌力與運動表現，沒有探討組織延展性的變化。腓腸肌肌肉肌腱複合體因包含肌肉、腱膜、肌腱三大部分，較其他肌肉適合用來觀察伸展技術後組織延展性的變化。因此，本研究計畫預計利用剪力波彈性影像儀測量腓腸肌肌肉肌腱複合體各部分延展性的變化，以了解不同伸展運動對於組織延展性的影響。 本研究計畫為前瞻性、介入性、單盲性、前後實驗，徵召21名健康且規律運動之成人進行實驗。受試者在簽署研究同意書後，受試者將以隨機次序接受靜態與動態伸展運動，此兩種技術施行時間相隔一週，並於第三週進行施測者間信度的試驗。量測項目將包括以剪力波彈性影像儀測量腓腸肌肌肉肌腱複合體的硬度、以電子量角器測量踝關節的最大背屈角度，並以自製的高度計測量下蹲跳的高度。所有變項皆在介入伸展技術前後各測量一次。所有統計分析將以SAS 9.4進行，以重複量測變異數分析計算前後以及兩種伸展技術之間的差異，並以組內相關係數、量測標準誤與最小可偵測變化值計算各個參數的測試者內與測試者間信度。顯著水準訂在=0.05，而檢定力訂在0.8。 本研究主要結果為：(一)進行二種伸展運動後皆能降低腓腸肌肌肉肌腱複合體的肌腱和腱膜的硬度；二種伸展運動皆沒有對肌肉硬度造成顯著的改變。(二)在二種伸展運動後，最大背屈角度皆會增加，但二者之間沒有顯著差異；(三)在動態伸展運動後，下蹲跳高度沒有顯著差異；然而靜態伸展運動後下蹲跳高度顯著下降。 本研究為第一篇使用剪力波彈性超音波影像檢測腓腸肌肌肉肌腱複合體再進行不同伸展運動後的硬度變化，也是第一篇同時檢測肌腱、腱膜與肌肉三種組織的研究。此結果顯示兩種伸展運動皆能改善肌腱與腱膜組織的延展性，而肌肉的延展性在伸展運動後並沒有顯著改變。此外，動態伸展運動能同時改善組織延展性並不讓運動表現變差。未來研究可藉此探討不同伸展運動對於組織延展性與對運動表現的影響，包括不同的族群、伸展時機，以為臨床運動處方的參考。
Sufficient flexibility of the gastrocnemius muscle-tendon unit (MTU) is necessary to accomplish daily or sports activities in order to prevent from injuries. Static stretching exercises had been widely used as a part of warm up exercises. Decreased force production after static stretching has documented recently and dynamic stretching is suggested instead. However, only changes in the maximal voluntary contraction and sports performance were measured as evidences of effectiveness. The gastrocnemius MTU is more appropriate to be examined the tissue extensibility because it consists of three portions of tissue structures, including the muscle, the aponeurosis, and the free tendon. Therefore, the purpose of this research project will be to investigate the tissue extensibility and functional performance of the gastrocnemius MTU after different stretching exercises using shear wave elastography (SWE). The research was a prospective, randomize-order, single-blinded, and pre-post test design. There were 21 healthy and active adults recruited for the research project. All participants received static and dynamic stretching exercises at one-week interval and intervention order was employed randomly. The interrater reliability test was executed on the third week. The measurements included stiffness of the gastrocnemius MTU using the SWE system, maximum ankle dorsiflexion angle using an electrogoniometer, and countermovement jump height using a self-made jump height measuring board. All variables were acquired before and after intervention in both sessions. A two-way ANOVA with repeated measures was used to compare the differences between conditions, different testing sessions, and their interaction. The intra-class correlation coefficients, standard errors of measurement and minimal detectable change were used to test the intrarater and interrater reliabilities. All statistical analyses were executed using SAS 9.4. The significant level was set at =.05, and the power was set at 0.8. The results of this research were: 1) The stiffness of the tendon and aponeurosis of the gastrocnemius MTU significantly decreased after two kinds of stretching exercises, but no significant difference was noted in stiffness of the gastrocnemius muscle; 2) Both stretching exercises significantly improved the maximum ankle dorsiflexion angle while no significant difference was found between static and dynamic stretching exercise; 3) There was no significant difference in countermovement jump height after dynamic stretching exercise, but the countermovement jump height decreased significantly after static stretching exercise. It was the first research that examined three different portions of the gastrocnemius MTU on tissue extensibility after different kinds of stretching exercises using SWE. The results concluded that both stretching exercises significantly improved extensibility of tendon and aponeurosis, but extensibility of muscle did not change significantly. This research gives an insight that dynamic stretching exercise can improve the tissue extensibility without negative effects on sports performance. Information of tissue extensibility provided by SWE can assist in effects of different stretching exercises on sports performance. Therefore, the application of stretching exercises, including population, timing and duration can be further examined in the future.
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