The Effects of Shoulder Position on Bicep Brachii Activation

Abstract

Record ID: 245

Award(s): Excellence in Undergraduate Research Mentorship; Excellence in Research Communication

Program Affiliation: Capstone

Presentation Type: Poster

Abstract: Our study aims to investigate how different shoulder positions affect the activation of the biceps brachii muscle during bicep flexion resistance exercises. Limited research shows that shoulder position from extended to neutral to flexed changes biceps activations. The purpose of this study is to investigate which shoulder position elicits the greatest relative EMG activation. The EMG of the biceps brachii will be measured in shoulder extension, anatomical position, and shoulder flexion. The EMG data will be derived from an elbow flexion curl exercise and a metronome will be used to keep consistent speed of repetitions. The EMG analyzed will consist of the peak normalized signal of a full concentric repetition. Each participant will have a 1RM measured in each of the shoulder positions and will be tested with the same relative load across each shoulder position. The expected results are that performing a bicep curl with the shoulder in an extended position will produce the greatest EMG activation, followed by the shoulder in anatomical and finally the least activation in the flexed position. The expected results that a bicep curl from a shoulder extended position would increase the activation due to the reduced force-generating capabilities in an extended position. This extended position would have increased biceps activations from having to recruit more muscle fibers to complete the biceps curl with the relative external load and the induced stretch of the biceps from the initial starting position.