Changes in Stiffness of the Gastrocnemius Muscle-Tendon Unit After Stretching Exercises
Date Issued
2016
Date
2016
Author(s)
Lai, Guan-Fan
Abstract
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.
Subjects
gastrocnemius muscle
stretching exercise
stiffness
shear wave elastography
Type
thesis
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