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Graphical User Interface to Identify Optimal Combinations of Isometric Normalization Tests for the Production of Maximum Voluntary Activation of the Shoulder Muscles

      In the recently published article of Dal Maso et al,
      • Dal Maso F.
      • Marion P.
      • Begon M.
      Optimal combinations of isometric normalization tests for the production of maximum voluntary activation of the shoulder muscles.
      a novel method was proposed to identify the optimal combinations of maximum isometric voluntary contraction (MVIC) tests to normalize the electromyographic signal of 12 shoulder muscles. These optimal combinations include the smallest number of MVIC tests required to produce electromyographic activation levels >90% of maximum voluntary activation for >90% of the participants. This method produced more reliable recommendations to normalize shoulder electromyographic signals than previous methods.
      • Castelein B.
      • Cagnie B.
      • Parlevliet T.
      • Danneels L.
      • Cools A.
      Optimal normalization tests for muscle activation of the levator scapulae, pectoralis minor and rhomboid major: an electromyography study using maximum voluntary isometric contractions.
      • Boettcher C.E.
      • Ginn K.A.
      • Cathers I.
      Standard maximum isometric voluntary contraction tests for normalizing shoulder muscle EMG.
      However, these recommendations only address optimal combinations for the 12 muscles individually and simultaneously, using all 15 MVIC tests available, and with thresholds of 90%. Researchers may wish to focus on a subset of these shoulder muscles (4095 possible combinations with 12 muscles), exclude MVIC test(s) involving postures that may trigger pain in patient populations, and/or adjust their own sensitivity thresholds. Because each single case cannot be covered in an article, the method proposed by Dal Maso
      • Dal Maso F.
      • Marion P.
      • Begon M.
      Optimal combinations of isometric normalization tests for the production of maximum voluntary activation of the shoulder muscles.
      was implemented into a graphical user interface developed in MATLAB.a Web addresses to download deployed versions and original codes are provided in appendix 1. In this software, the user selects the muscle(s) and the MVIC test(s) of interest from the “select muscles” and “select MVIC tests” panels, respectively. Then, the maximum number of MVIC tests to include in the optimal combination and the thresholds are specified from the “select parameters” panel. The default values consist of the previously recommended thresholds of 90% of maximum voluntary activation for 90% of participants.
      • Dal Maso F.
      • Marion P.
      • Begon M.
      Optimal combinations of isometric normalization tests for the production of maximum voluntary activation of the shoulder muscles.
      The results based on the user's settings and the proposed method
      • Dal Maso F.
      • Marion P.
      • Begon M.
      Optimal combinations of isometric normalization tests for the production of maximum voluntary activation of the shoulder muscles.
      appear after pressing “identify optimal combination.” The MVIC tests retained in the optimal combination are highlighted. A table reports the average ± SD of the 95th percentile of participants with the highest electromyographic activation levels. Additionally, a figure shows the percentage of participants for whom the electromyographic activation level is comprised between 100% and 0% in 10% steps as indicated by a color code. The user is informed if no optimal combination satisfies the criteria for all selected muscles. In this case, the combination that produces the highest electromyographic activation levels across all participants and all muscles is displayed. Otherwise, each combination that satisfied the criteria can be displayed and saved. To date, the results are based on a database that includes 38 participants (16 participants for the anterior deltoid). The sample will regularly increase with new participants volunteering to shoulder electromyographic-based experiments in our laboratory. The “read me” button will always report the exact number of participants included in the database. To conclude, the use of this graphical user interface as a reference to identify optimal MVIC tests for the normalization of shoulder electromyographic signals may help to improve the comparison between studies that focus on shoulder muscle activation levels.
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      References

        • Dal Maso F.
        • Marion P.
        • Begon M.
        Optimal combinations of isometric normalization tests for the production of maximum voluntary activation of the shoulder muscles.
        Arch Phys Med Rehabil. 2016; 97: 1542-1551
        • Castelein B.
        • Cagnie B.
        • Parlevliet T.
        • Danneels L.
        • Cools A.
        Optimal normalization tests for muscle activation of the levator scapulae, pectoralis minor and rhomboid major: an electromyography study using maximum voluntary isometric contractions.
        Arch Phys Med Rehabil. 2015; 96: 1820-1827
        • Boettcher C.E.
        • Ginn K.A.
        • Cathers I.
        Standard maximum isometric voluntary contraction tests for normalizing shoulder muscle EMG.
        J Orthop Res. 2008; 26: 1591-1597