Gonçalves Josiane Sotrate, Shinohara Moriguchi Cristiane, Takekawa Karina Sachiko, Coury Helenice Jane Cote Gil, Sato Tatiana de Oliveira
Laboratory of Preventive Physical Therapy and Ergonomics (LAFIPE), Physical Therapy Post Graduate Program, Federal University of São Carlos, Brazil.
J Phys Ther Sci. 2017 May;29(5):793-798. doi: 10.1589/jpts.29.793. Epub 2017 May 16.
[Purpose] To assess the effects of forearm support and shoulder posture on upper trapezius and anterior deltoid activity. [Subjects and Methods] Twenty-three female university students were evaluated. Muscle activity was assessed by a portable surface electromyography (sEMG) system (Myomonitor IV, Delsys, USA). Upper trapezius and anterior deltoid activity were recorded in five shoulder flexion postures: 0°, 15°, 30°, 45° and 60° and in two conditions: with the forearm supported and unsupported. Descriptive data analysis was performed and statistical analysis was conducted by a multivariate analysis of variance with three repeated factors (posture, support and side). [Results] Three-way interactions were not significant. Two-way interaction was significant for support and posture for both muscles, indicating that the muscular activity depends on the forearm support and shoulder posture. The forearm support reduced upper trapezius and anterior deltoid activity for all shoulder flexion angles. The mean and standard deviation for this decrease was 7.8 (SD=4.6)% of the maximal voluntary contraction for anterior deltoid and 3.8 (SD=2.0)% of the maximal voluntary contraction for upper trapezius. In the unsupported condition, increasing the shoulder flexion angle caused an increase in the upper trapezius and anterior deltoid activation. [Conclusion] These results highlight the importance of using forearm support and to maintain neutral shoulder posture, when the upper arms are not supported, to reduce muscle activation. Thus, this study provides evidence about the effect of these recommendations to reduce muscular activity.
[目的]评估前臂支撑和肩部姿势对上斜方肌和三角肌前束活动的影响。[对象与方法]对23名女大学生进行了评估。采用便携式表面肌电图（sEMG）系统（美国Delsys公司的Myomonitor IV）评估肌肉活动。记录了上斜方肌和三角肌前束在五种肩部屈曲姿势（0°、15°、30°、45°和60°）以及两种状态（前臂支撑和无支撑）下的活动情况。进行了描述性数据分析，并通过具有三个重复因素（姿势、支撑和侧别）的多因素方差分析进行统计分析。[结果]三因素交互作用不显著。两种肌肉的支撑与姿势的二因素交互作用显著，表明肌肉活动取决于前臂支撑和肩部姿势。前臂支撑可降低所有肩部屈曲角度下的上斜方肌和三角肌前束活动。三角肌前束这种降低的平均值和标准差为最大自主收缩的7.8（标准差=4.6）%，上斜方肌为最大自主收缩的3.8（标准差=2.0）%。在无支撑状态下，增加肩部屈曲角度会导致上斜方肌和三角肌前束激活增加。[结论]这些结果突出了使用前臂支撑以及在上臂无支撑时保持肩部中立姿势以减少肌肉激活的重要性。因此，本研究为这些减少肌肉活动的建议的效果提供了证据。
