Discipline of Exercise and Sport Science, Faculty of Health Sciences, The University of Sydney, Australia.
Discipline of Biomedical Science, Sydney Medical School, The University of Sydney, Australia.
J Electromyogr Kinesiol. 2014 Apr;24(2):221-7. doi: 10.1016/j.jelekin.2014.01.007. Epub 2014 Jan 31.
No direct evidence exists to support the validity of using surface electrodes to record muscle activity from serratus anterior, an important and commonly investigated shoulder muscle. The aims of this study were to determine the validity of examining muscle activation patterns in serratus anterior using surface electromyography and to determine whether intramuscular electromyography is representative of serratus anterior muscle activity.
Seven asymptomatic subjects performed dynamic and isometric shoulder flexion, extension, abduction, adduction and dynamic bench press plus tests. Surface electrodes were placed over serratus anterior and around intramuscular electrodes in serratus anterior. Load was ramped during isometric tests from 0% to 100% maximum load and dynamic tests were performed at 70% maximum load. EMG signals were normalised using five standard maximum voluntary contraction tests.
Surface electrodes significantly underestimated serratus anterior muscle activity compared with the intramuscular electrodes during dynamic flexion, dynamic abduction, isometric flexion, isometric abduction and bench press plus tests. All other test conditions showed no significant differences including the flexion normalisation test where maximum activation was recorded from both electrode types. Low correlation between signals was recorded using surface and intramuscular electrodes during concentric phases of dynamic abduction and flexion.
It is not valid to use surface electromyography to assess muscle activation levels in serratus anterior during isometric exercises where the electrodes are not placed at the angle of testing and dynamic exercises. Intramuscular electrodes are as representative of the serratus anterior muscle activity as surface electrodes.
目前尚无直接证据支持使用表面电极来记录前锯肌的肌肉活动，前锯肌是一个重要且常被研究的肩部肌肉。本研究旨在确定使用表面肌电图检查前锯肌肌肉激活模式的有效性，并确定肌内肌电图是否代表前锯肌的肌肉活动。
7 名无症状受试者进行了动态和等长肩前屈、伸展、外展、内收和动态卧推加测试。表面电极放置在前锯肌上方，肌内电极放置在前锯肌周围。等长测试时，负载从 0%逐渐增加到 100%最大负载，动态测试时以 70%最大负载进行。EMG 信号使用 5 个标准最大自主收缩测试进行归一化。
与肌内电极相比，表面电极在动态前屈、动态外展、等长前屈、等长外展和卧推加测试中显著低估了前锯肌的肌肉活动。所有其他测试条件均无显著差异，包括在两种电极类型都记录到最大激活的前屈归一化测试中。在动态外展和前屈的向心阶段，表面和肌内电极记录到的信号相关性较低。
在等长运动中，电极未放置在测试角度时，以及在动态运动中，使用表面肌电图评估等长运动和动态运动中前锯肌的肌肉激活水平是无效的。肌内电极与表面电极一样能代表前锯肌的肌肉活动。
