背景與目的：本研究目的在評估用超音波影像來測量腹橫肌厚度及其變化的施測者內信度。方法：使用HDI5000超音波儀器施測腹橫肌肌肉收縮，分析休息時厚度(thickness resting, Tr)、最大收縮時的肌肉厚度(thickness during maximal contraction, Tm)、厚度變化量(change of the thickness，△T)以及標準化厚度變化量(normalized change of the thickness，△T/h)等四個量測參數。以方便取樣方式收集年齡在20?30歲之問的受試者。在主要實驗部分，包括當天測的施測者內信度以及相隔兩天測的施測者內信度。在修正實驗部分，包括相隔兩天測的施測者內信度。統計分析：以五種統計指標分析，包括組內相關係數(ICC)、受試者內變異係數(CVw)、受試者閒變異係數(CVb)，平均差的95%信賴區間(95%CI)、以及量測標準誤差(SEM)。結果：修正實驗部份的四個量測參數之ICC、CVw以及SEM均較主要實驗部份的相隔兩天測的施測者內信度有改善，而且修正實驗部份的ICC大都達到優良信度範圍，另外休息時厚度以及最大收縮時厚度的CVw小於10%。CVb都大於10%。95%CI包括0。就SEM而言，兩次施測的左右兩側升、Tm、△T以及△T/Tm差至少分別大於0.02公分、0.04公分、0.04公分以及0.05公分，才沒有在誤差範圍內。結論：經過適當訓練及修正實驗方法後，初學者利用超音波評估腹橫肌肌肉功能於量測時至少可達到普通至良好信度。在修正部份實驗過程後，和主要實驗比較，其信度有改善。臨床意義：可以利用超音波評估腹橫肌肌肉功能，及了解肌肉功能變化。

Background and Purpose: The use of ultrasonography for the assessment of musculoskeletal function becomes important clinical applications. The purpose of the main study was to investigate the intra-rater reliability of the measurement of transverses abdominis and its change by ultrasonography. Method: HDI 5000 ultrasonography was used to assess contraction of transverses abdomonins (TrA) and measure four parameters, including thickness of resting (Tr), thickness during maximal contraction (Tm), change of the thickness (AT), and normalized change of the thickness(AT/Tm). Convenient sampling of subjects aged between 20 and 30 years old was included. In the pilot study, intra-day intra-rater and inter-day intra-rater reliability were tested. After modifying the process of experiment, we re-examined the inter-day intra-rater reliability in the main study. Statistical analysis: Intra-class correlation coefficient (ICC), within subjects of coefficient of variance (CVw), between subjects of coefficient of variance (CVb), 95% confidence interval of the mean difference (95%CI), and standard error of measurements (SEM) were analyzed. Result: ICC, CVw and SEM of four parameters of the modified study improved compared to those of the main study. In addition, Most ICC of the modified experiment reached the excellent reliability. Besides, CVw of thickness of resting and during maximal contraction were smaller than 10% and CVb were greater than 10%. The range of 95%CI included 0. As for SEM, Tr, Tm, AT, and AT/Tm of both sides for two analysis were at least greater than 0.02cm, 0,04cm, 0.04cm and 0.05 respectively, indicating not in error range. Conclusion: After proper training for operating ultrasonography and modification part of experimental process, the reliability for the beginners assessing the transverses abdominis could reach fair to good reliability. After modifying parts of experimental procedure, the reliability of the modified study was improved compared to that of the main study. Clinical significant: Dynamic ultrasonography appeared to be a reliable tool for assessing thickness of transverses abdomens at clinical practice.