Single-Session Video and Electromyography Feedback in Overhead Athletes With Scapular Dyskinesis and Impingement Syndrome

Abstract

Context Subacromial impingement syndrome (SIS) is associated with scapular dyskinesis, or imbalanced scapular muscle activity. Evidence has shown that feedback can improve scapular control in patients with SIS. However, it is unknown whether real-time video feedback or electromyography (EMG) biofeedback is optimal for improving scapular kinematics and muscle activity during a functional task. Objective To compare the effects of video and EMG feedback sessions on absolute muscle activity (upper trapezius [UT], lower trapezius [LT], serratus anterior), muscle balance ratios (UT/LT, UT/serratus anterior), and scapular kinematics (anterior-posterior tilt, external-internal rotation, upward rotation) in SIS participants during arm elevation and lowering. Design Randomized controlled clinical trial. Setting Research laboratory. Patients or Other Participants Overhead athletes who were diagnosed with SIS and who also exhibited scapular dyskinesis (N = 41). Main Outcome Measure(s) Three-dimensional kinematics and EMG were recorded before and after feedback training. Results Lower trapezius muscle activity increased (4.2%–18%, P < .011) and UT/LT decreased (0.56–1.17, P < .013) in the EMG biofeedback training group as compared with those in the video feedback training group. Scapular upward rotation during arm elevation was higher in the video group than in the EMG group after feedback training (2.3°, P = .024). Conclusions The EMG biofeedback improved muscle control and video feedback improved the correction of scapular upward rotation in patients with SIS. Trial Registration Number ClinicalTrials.gov: NCT03252444.

Glenohumeral Internal Rotation Deficit on Pitching Biomechanics and Muscle Activity

“…The muscle activities were measured with a wireless surface electromyograph (EMG), the Noraxon TeleMyo 2400 T (Noraxon, USA), and processed with Myo Research XP software (MR-XP 1.07 Master Edition, Noraxon, USA). The electrodes were attached to the pitchers with shirts removed and placed on the upper trapezius, lower trapezius, serratus anterior, biceps brachii, triceps brachii, and anterior deltoid of the dominant arm [23,25]. The MVICs of the target muscles were collected for normalization of the EMG data [26,27].…”

“…Glenohumeral internal rotation deficit (GIRD) is believed to be one of the adaptions contributing to shoulder injuries [16,17]. GIRD has been defined as loss of internal rotation (IR) in the dominant shoulder relative to the non-dominant shoulder [18,19].…”

Current Views of Scapular Dyskinesis and its Possible Clinical Relevance

“…Previous reports have shown that intentional attempts at repositioning the scapula prior to elevating and/or rotating the humerus, called conscious correction, increases scapular muscle activity and enhances scapular kinematics. 34,86,89 Additionally, visual feedback, [93][94][95][96][97] auditory feedback, 93,94 and kinesthetic feedback 93,94 have been shown to positively influence scapular muscle activity and positioning. Considering the scapula as a 'link' within the kinetic chain, the feedback approach may be better suited for re-establishing scapular control as it relates to the sequential activation within the kinetic chain.…”

“…105 Feedback may be incorporated throughout the treatment program but there is not an exclusive type to recommend considering various forms of feedback have been shown to have positive clinical influence. [93][94][95][96][97] However, it should be noted that too much feedback can be detrimental to learning as the patient becomes reliant on the knowledge of performance. 90…”

Scapular force: Couple ratios in healthy shoulders – An observational study reflecting typical values

“…The poor anchoring of the scapula by bony attachments results in the dynamic and static stability of the scapula being largely dependent on the balanced actions of the scapular musculature (Du et al 2020 ; Kibler & Sciascia 2010 ; Kibler et al 2013 ; Michener et al 2016 ; Sahrmann 2001 ). Historically, it has generally been accepted that proper dynamic scapular stability is provided through the combined actions of the force couples of the serratus anterior and all the parts (upper, middle and lower) of the trapezius (Bagg & Forrest 1988 ; Inman et al 1944 ).…”