Background

Shoulder muscle force is commonly assessed during clinical examination using both an isometric “make” test against a fixed resistance or a “break” test where the examiner exerts enough force to break the isometric contraction. The purpose of this study was to explain the difference in force produced during these two forms of testing.

Methods

Data were collected on 25 subjects. Both shoulder external rotation and elevation force were measured over three trials, isometrically, for approximately 3 s, after which the examiner exerted enough force to move the arm. Surface EMG was recorded for the infraspinatus for external rotation and middle deltoid for elevation. Peak isometric and break forces, and normalized, averaged EMG data at peak isometric and break forces were compared with paired t-tests.

Findings

External rotation peak break force was 46.9% (SD33.6, range − 3% to 108.6%) greater than isometric force (p < 0.01). EMG for the infraspinatus was 17.0% (20.8) greater at break (p < 0.01). For elevation, peak break force was 63% (73.1, range − 3.5 to 238.16%) greater than isometric force (p < 0.01). EMG for the middle deltoid was 11.1% (30.8) greater during peak break force (not significant).

Interpretations

There is a difference in both force and muscle activity between “make” and “break” tests. Clinicians should use a consistent method when measuring force and a break test will provide the maximum force. The cause of greater force produced during a break test is likely attributable to the brief eccentric contraction rather than greater recruitment. Future analysis will include examining the differences in make and break forces based on activity levels.

中文翻译：

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制作与断裂测试期间的肩部肌肉力量和肌电图活动

背景

通常在临床检查期间使用对固定阻力的等距“ make”测试或检查者施加足够的力来破坏等长收缩的“ break”测试来评估肩部肌肉的力量。这项研究的目的是解释在这两种测试形式期间产生的力的差异。

方法

收集了25个受试者的数据。在三个试验中，以等轴测法测量了大约3 s的肩部外部旋转力和抬高力，然后检查者施加了足够的力来移动手臂。记录下肌电图的肌电图以示腓下肌的外旋和中三角肌的抬高。将峰值等距和断裂力以及在峰值等距和断裂力处的标准化平均EMG数据与成对的t检验进行比较。

发现

外部旋转峰值断裂力比等轴测力大46.9％（SD33.6，范围-3％至108.6％）（p  <0.01）。鼻下肌肌电图在断裂时增加17.0％（20.8）（p  <0.01）。对于高程，峰值断裂力比等轴测力大63％（73.1，范围-3.5至238.16％）（p  <0.01）。在峰值断裂力作用下，中间三角肌的肌电图增加11.1％（30.8）（无明显意义）。

释义

在“制造”和“断裂”测试之间，力量和肌肉活动均有所不同。在测量力时，临床医生应使用一致的方法，并且断裂试验将提供最大的力。断裂试验期间产生更大力的原因可能是由于短暂的偏心收缩而不是更大的重击。未来的分析将包括根据活动水平检查制动力和制动力的差异。