Scapular muscle activation and co-activation following a fatigue task

Abstract

Scapular muscles precisely move the scapulothoracic articulation and if fatigued may contribute to pathology. Fatigue of serratus anterior may be a mechanism for shoulder pathology by altering scapula motions and requiring compensation by other shoulder muscles. A total of 28 asymptomatic subjects performed a task to fatigue the serratus anterior, while muscle activity was recorded from three muscles. Mean normalized activation levels and activation ratios were examined before and after the fatigue task during arm elevation and lowering. All muscles demonstrated meaningful declines in the median frequency of the electromyographic signal during the task. Following the task, only the upper trapezius had higher mean activation levels (mean difference 10.79% MVIC), while the serratus anterior/lower trapezius activation ratio was altered (mean difference -0.3). Higher mean upper trapezius activation may be compensatory for fatigue of other shoulder muscles and may reflect fiber type or central control mechanisms. Serratus anterior eccentric endurance training may be beneficial for the prevention of shoulder pathology.

Pilates Based Exercise in Muscle Disbalances Prevention and Treatment of Sports Injuries

“…Using this task as a rehabilitative exercise may be too strenuous for most patients, but it may have potential as an assessment tool to help determine the success of serratus anterior strengthening and endurance training or the readiness for return to high demand overhead work. (Szucs et al, 2009) The results of the controlled study with 19 participants show that a 12-week long Pilates training program was effective in improving core strength and posture (exercising subjects showed smaller static thoracic kyphosis during quiet standing) as well as certain aspects of scapula and upper trunk displacement during a shoulder flexion task. As deficits in neckshoulder biomechanics have previously been associated with symptoms in the neckshoulder region, these results could support the use of the Pilates method in the prevention of neck-shoulder disorders.…”

“…In addition, the serratus anterior is considered to be one component of several muscle synergies at the shoulder complex and its fatigue may alter the balance of these synergies. (Szucs et al, 2009) Precise control of movement at the shoulder complex during upper extremity use is considered critical to the health of the shoulder region. In Pilates based exercise it is strongly recommended to keep scapulas in position of "soft V" at starting positions so the intention is to voluntarily "fix" the scapula in the position of posterial depression.…”

“…As muscle fatigue can be a central phenomenon as well as a peripheral phenomenon, the upper trapezius may have been recruited differently during or after the task. (Alexander et al, 2007, Hunter et al, 2006 as cited in Szucs et al, 2009) It is ball, important that performing Pilates Push-up, which is an exercise in close kinematic chain, serratus anterior muscle should be activated rather than a dominant role of upper trapezius muscle which can be achieved by the alignment of spine, unlocked elbow joints, lower -costal breathing and touching stimulus of an instructor during execution of an exercise. The Push-up exercise has been recommended as a rehabilitative exercise for individuals with shoulder pathology because it strongly activates serratus anterior while minimizing upper trapezius co-activation (Ekstrom et al, 2005, Lear&Gross 1998, Ludewig et al, 2004 as cited in Szucs et al, 2009).…”

“…(Alexander et al, 2007, Hunter et al, 2006 as cited in Szucs et al, 2009) It is ball, important that performing Pilates Push-up, which is an exercise in close kinematic chain, serratus anterior muscle should be activated rather than a dominant role of upper trapezius muscle which can be achieved by the alignment of spine, unlocked elbow joints, lower -costal breathing and touching stimulus of an instructor during execution of an exercise. The Push-up exercise has been recommended as a rehabilitative exercise for individuals with shoulder pathology because it strongly activates serratus anterior while minimizing upper trapezius co-activation (Ekstrom et al, 2005, Lear&Gross 1998, Ludewig et al, 2004 as cited in Szucs et al, 2009). Using this task as a rehabilitative exercise may be too strenuous for most patients, but it may have potential as an assessment tool to help determine the success of serratus anterior strengthening and endurance training or the readiness for return to high demand overhead work.…”

Shoulder biomechanics: today’s consensus and tomorrow’s perspectives

“…To monitor the shoulder-girdle mobility Garofalo identified and tested a 3D motion analysis protocol, which will develop into an easy to use tool able to provide targeted clinical information. Moving further toward clinical questions, Szucs et al [18] analyzed the relationship between muscle function/fatigue and the development of shoulder pathologies. In their study, through kinematic and EMG analysis, these authors tested the hypothesis that fatigue of the serratus anterior can alter shoulder motion, induce compensation by other shoulder muscles which might then lead to pathology.…”