Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors

doi:10.1053/apmr.2003.50087

Archives of Physical Medicine and Rehabilitation

Volume 84, Issue 4, April 2003, Pages 563-568

https://doi.org/10.1053/apmr.2003.50087 Get rights and content

Abstract

Finley MA, Lee RY. Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors. Arch Phys Med Rehabil 2003;84:563-8. Objective: To determine the effect of trunk sitting posture on scapular kinematics during humeral elevation by using skin-mounted electromagnetic tracking sensors. Design: Repeated-measures design contrasting scapular kinematics in 2 different sitting postures. Setting: A biomechanics laboratory in Hong Kong with a real-time, 3-dimensional electromagnetic tracking device for measuring movements of the scapula. Participants: A sample of 16 healthy adults (12 women, 4 men; age, 21.6[plusmn]3.92y) with full, pain-free shoulder range of motion and no history of shoulder pathology. Interventions: Not applicable. Main Outcome Measures: Movements of the scapula were measured while each subject performed humeral elevation in an upright seated position and a slouched seated position. Results: In both postures, posterior tip, lateral and upward rotation of the scapula, and lateral rotation of the humerus were observed during humeral elevation. When the slouched posture was adopted, there were significant decreases in the posterior tip and lateral rotation of the scapula, but there was no significant change in the magnitude of the upward rotation of the scapula. Conclusion: Increased thoracic kyphosis significantly alters the kinematics of the scapula during humeral elevation.

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Cited by (129)

Effects of slouched sitting posture on clavicular and scapular orientations and movements in individuals with neck pain with scapular dysfunction
2024, Gait and Posture
It has been suggested that sitting posture affects clavicular, scapular and spinal kinematics, however its effects in people with neck pain and scapular dysfunction remain unknown. The study aimed to determine the clavicular and scapular kinematics in different sitting postures in patients with neck pain and scapular dysfunction.
Thirty-four participants with neck pain and scapular dysfunction were recruited into the study. Kinematics of the clavicle and scapula were recorded using motion analysis at rest and during arm elevation (at 30, 60, 90, and 120 degrees) in a slouched and upright sitting posture.
Compared to the upright sitting posture, the slouched sitting posture had increased clavicular protraction and elevation as well as scapular internal rotation and anterior tilt at rest and during the arm raising and lowering phases (at 30, 60, 90, and 120 degrees) (p < 0.05). The slouched sitting also had increased scapular upward rotation in the lowering phase at all angles (p < 0.05).
The slouched sitting posture has a significant influence on clavicular and scapular kinematics. Awareness of good sitting posture should be encouraged in patients with neck pain and scapular dysfunction.
Effect of improved thoracic kyphosis on forward shoulder posture after mobilization in individuals with thoracic hyperkyphosis
2022, Clinical Biomechanics
Thoracic hyperkyphosis structurally alters the position of the scapula to cause forward shoulder posture. However, the effect of improved thoracic hyperkyphosis on forward shoulder posture is unclear. The objective of this study was to determine the effect of eight weeks of thoracic mobilization on improving thoracic hyperkyphosis and forward shoulder posture and determine the cutoff change ratio in kyphosis for improving forward shoulder posture using the decision tree method.
This study included 19 participants with thoracic hyperkyphosis who underwent thoracic mobilization for eight weeks. Forward shoulder posture (acromion-to-the-wall index) and thoracic kyphosis were measured before and after thoracic mobilization.
The intervention significantly improved thoracic kyphosis and forward shoulder posture. The cutoff change ratio in kyphosis for improving forward shoulder posture was >13.79%. In the subgroup analysis of participants with a change ratio of kyphosis >13.79% (seven cases), all patients showed improved forward shoulder posture. In contrast, in the subgroup with a change ratio of kyphosis ≤13.79% (12 cases), eight cases showed improved forward shoulder posture, while four cases showed no improvement.
Thoracic mobilization can be recommended in shoulder rehabilitation programs to improve forward shoulder posture to manage and prevent scapular malalignment in individuals with thoracic hyperkyphosis. We suggest that a high probability of improvement in forward shoulder posture can be expected when kyphosis is improved by >13.79%.
Scapular dyskinesis type is associated with glenohumeral joint and scapular kinematic alteration during pitching motion in baseball players
2021, Journal of Bodywork and Movement Therapies
Scapular dyskinesis (SD) is associated with an increased risk of throwing-related shoulder injury onset, resulting in abnormalities in glenohumeral joint (GH) and scapular motions during pitching. The effects of SD on shoulder motion during pitching remain unknown. This study aimed to investigate kinematic alterations in GH and scapular motions during pitching in baseball players with type I SD.
Sixty-seven university and independent-league baseball players with and without SD were included. Pitching motion was measured using an optical three-dimensional motion capture system, and a SD test was conducted to evaluate SD. SD was classified into types I–IV. The inter-rater reliability of SD assessment was calculated using kappa coefficients. Three-dimensional GH and scapular kinematics during pitching motion were analyzed.
The percentage of agreement representing the inter-rater reliability of SD assessment was 77.6% (52/67; kappa coefficient: 0.72). Overall, 24 and 27 participants were categorized into abnormal (type I SD) and normal group (type IV SD), respectively, with normal scapular motion; one individual with type III SD was excluded. The abnormal group exhibited a significantly increased GH external rotation angle (9°) and decreased scapular posterior tilt angle (6°) during the maximum external rotation period compared with the normal group.
Baseball players in the abnormal group showed increased GH motion and decreased scapular motion during pitching. The SD test for the evaluation of type I SD can help predict excessive GH external rotation and decreased scapular posterior tilt during pitching.
Influence of Forward Head Posture on Cervicocephalic Kinesthesia and Electromyographic Activity of Neck Musculature in Asymptomatic Individuals
2020, Journal of Chiropractic Medicine
Citation Excerpt :
In the present study, the EMG activity of the UT and SCM muscles was found to be significantly increased in the FHP group relative to the control group both at rest and during activity. Forward head posture with rounded shoulders due to adoption of poor sitting posture for longer durations has been found to be common in the young population as a result of prolonged use of smartphones and computers.63,64 Sitting with a forward head inclination involves a combination of lower cervical flexion, upper cervical extension, and anterior shoulder position, leading to lengthening and weakness of deep cervical flexors and shortening of deep cervical extensors.40
The purpose of this study was to compare cervicocephalic kinesthesia and electromyographic (EMG) activity of neck muscles—upper trapezius (UT) and sternocleidomastoid (SCM)—between individuals with and without forward head posture (FHP) and to examine the correlation between cervicocephalic kinesthesia and craniovertebral angle (CVA).
Twenty-two asymptomatic individuals with FHP and 22 without FHP were recruited for the present study. Craniovertebral angle was measured, and those with CVA ≤53° were assigned to the FHP group, whereas those with CVA >53° were assigned to the control group. Thereafter, cervicocephalic kinesthesia and EMG activity of the neck muscles were assessed. Cervicocephalic kinesthesia was measured using a head repositioning accuracy test for all cervical spine motions. EMG activity of the UT and SCM muscles was recorded at rest and during activity.
Position-sense error values were found to be significantly greater for all directions—ie, flexion, extension, side flexion, and rotation—in participants with FHP than those without (P < .05). EMG activity of the UT and SCM muscles was found to be significantly raised both at rest and during activity in individuals with FHP relative to the non-FHP group (P < .05). Position-sense error values showed a significant inverse correlation with CVA (P < .05).
Findings of the present study suggest that cervicocephalic kinesthesia and activation patterns of the neck muscles may be significantly altered in individuals with FHP. Also, cervicocephalic kinesthesia is significantly associated with the severity of FHP.
Examining assessment methods of scapular motion: Comparing results from planar elevations and functional task performance
2020, Clinical Biomechanics
Scapular kinematics of breast cancer survivors are most often evaluated during arm elevation. However, known compensations exist during functional task performance. The purpose of this study was to determine if scapular kinematics of breast cancer survivors during arm elevation are related to scapular kinematics during functional task performance.
Scapular kinematics of 25 non-cancer controls and 25 breast cancer survivors (split by presence of impingement pain) during arm elevation in 3 planes and 3 reaching and lifting functional tasks were measured. Scapular upward rotation and scapulohumeral rhythm (SHR) at 30° increments of arm elevation were calculated. Between-group differences of upward rotation during arm elevation were evaluated with one-way ANOVAs (p < 0.05). The association of upward rotation angle and SHR during arm elevation and functional tasks was tested with Pearson correlations (p < 0.05).
Scapular upward rotation was reduced for the breast cancer survivor with pain at lower levels of arm elevation in each plane by up to 7.1° (p = .014 to 0.049). This is inconsistent with functional task results, in which upward rotation decrements occurred at higher levels of arm elevation. Upward rotation angles and SHR during arm elevation had an overall weak-to-moderate relationship (r = 0.003 to 0.970, p = .001 to 0.048) to values from functional tasks. Arm elevation during sagittal plane elevation demonstrated scapular upward rotation that was most closely associated to upward rotation during functional task performance.
Inconsistent relationships suggests that clinical evaluations should adopt basic functional movements for scapular motion assessment to complement simple arm elevations.
Effects of scapular retraction/protraction position and scapular elevation on shoulder girdle muscle activity during glenohumeral abduction
2019, Human Movement Science
Citation Excerpt :
Noteworthy, scapular protraction occurs through a summation of scapular abduction, internal rotation, and anterior tilt, which are all secondary to the action of pectoralis minor (Neumann, 2010). Moreover, previous research studies on scapular kinematics highlighted that protracted scapular position, secondary to slouched body posture and rounded shoulder posture, led to a significant increase of scapular anterior tilt and internal rotation (Finley & Lee, 2003; Thigpen et al., 2010). Given that, we may assume that protracted scapular position is associated with a shortening in pectoralis minor length.
According to scapulohumeral rhythm, shoulder abduction is followed through scapular upward rotation to ensure joint mobility and stability. Of interest, the shoulder abduction can be performed holding the scapula in different positions and in association with scapular elevation, with possible effects on shoulder muscle activity. Therefore, the aim of the study was to analyze the activity of relevant shoulder muscles and the activity ratios between the scapulothoracic muscles, during shoulder abduction performed in different combinations of scapular position (neutral, retracted, protracted) and scapular elevation.
The electromyographic activity of middle deltoid, serratus anterior, upper, middle and lower fibers of trapezius was recorded during shoulder abduction movements executed holding the scapula in neutral, retracted and protracted position, and subsequently a shoulder elevation movement. The activation of each muscle and the scapulothoracic muscles activity ratios were determined every 15 degrees, from 15° to 120° of abduction.
Scapular retraction led to higher activation of the entire trapezius muscle, whereas protraction induced higher upper trapezius, middle deltoid and serratus anterior activity, along with lower activity of middle and lower trapezius. Shoulder elevation led to higher activity of the upper trapezius and middle deltoid. Moreover, it induced lower activation of the serratus anterior and middle and lower trapezius, thus leading to high ratios between the upper trapezius and the other scapulothoracic muscles, especially between 15 and 75 degrees of abduction.
This study highlights that shoulder abduction performed with scapular protraction and in combination with scapular elevation leads to increased activity of the middle deltoid and upper trapezius, resulting in imbalances between the scapulothoracic muscles that could hamper the optimal scapulohumeral rhythm. The abduction performed in the aforementioned scapular conditions also induce potential reciprocal inhibition effects between the movers and stabilizers muscles of scapula, suggesting different motor control strategies of integrating a common shoulder movement with various modification of the scapular position.

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^☆: Supported in part by the International Society of Biomechanics (student travel grant) and The Foundation for Physical Therapy.

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ArticlesEffect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors☆

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Effect of sitting posture on 3-dimensional scapular kinematics measured by skin-mounted electromagnetic tracking sensors☆