Abstract
Background:
The scapula is a critical link utilized in the kinetic chain to achieve efficient overhead movement and transfer energy from the lower extremity to the upper extremity. Additionally, daily activities such as sitting at a computer or driving in a car may negatively influence an individual's ability to maintain proper body posture and therefore compromise those movements. To reduce these negative influences, posture garments have been designed to cue the individual in maintaining and improving posture and alignment, specifically targeting scapular positioning.
Purpose:
The purpose of this study was to compare scapular positioning between an IntelliSkin™ posture-cueing compression garment and a generic performance garment on scapular kinematics during static standing.
Study Design: Case control.
Methods:
Forty active females (1.68 ± 0.07 m; 67.29 ± 11.25 kg) stood in a natural standing position while wearing two different garments: IntelliSkin™ posture-cueing compression garment and a generic performance garment. Kinematic data were collected at 100 Hz using an electromagnetic tracking system (trakSTAR™, Ascension Technologies, Inc., Burlington, VT, USA) synced with The MotionMonitor® (Innovative Sports Training, Chicago, IL., USA).
Results:
Repeated measures ANOVAs revealed a statistically significant Shirt by Side interaction for scapular protraction/retraction (F(1,39) = 52.91, p ≤ 0.05) and main-effect of Shirt for scapula anterior/posterior tilt (F(1,39) = 96.45, p ≤ 0.05). Individuals showed increased retraction and posterior tilt while wearing the IntelliSkin™ posture-cueing compression garment.
Conclusion:
The results of the current study indicate that the IntelliSkin™ posture-cueing compression garment improved scapular positioning during static standing posture. The IntelliSkin™ posture-cueing compression garment may provide clinicians an adjunct strategy to include with rehabilitative protocols.
Level of Evidence:
Diagnosis, Level 3
Keywords: Kinetic chain, proprioceptive feedback, rehabilitation, scapular kinematics, upper extremity kinematics
Introduction
The body is designed for locomotion; however, specific daily activities, such as sitting at a desk for an extended period and prolonged screen use may negatively influence an individual's ability to maintain proper body posture and therefore compromise their movements.1,2 Excessive sitting posture influences the alignment on the entire axial skeleton which can ultimately have a negative impact on standing posture and the ability of the upper and lower extremities to efficiently move during locomotion. This posture is consistent with concepts described by Grimsby and Gray have stated that individuals with the classic forward head, rounded shoulders, and increased thoracic kyphosis, have scapulae that rotate forward and downward depressing the acromion process and thus decreasing the subacromial space.2 This may lead to alterations during overhead movement and impingement of the soft tissues in the subacromial space.2 Individuals displaying this posture have altered scapular positioning and kinematics, which is often referred to as ‘scapular winging,’ ‘scapular dyskinesia,’ or ‘scapular dyskinesis’ and may or may not be associated with the symptom of pain.3,4,7
The scapula is a critical link utilized in the kinetic chain for human movement.5-7 It must function in both stabilization and mobilization for efficient glenohumeral movement, as well as serve as a vital link in the kinetic chain.4,7 As a dynamic mover of the upper extremity, the scapula functions in protraction and retraction, upward and downward rotation, anterior and posterior tilt, and elevation and depression.7 Additionally, as a glenohumeral joint stabilizer, the scapula is a base of support for muscle attachment to allow free motion to occur about the glenohumeral joint.4
To combat the decline in optimal posture and scapular positioning, physical therapists and athletic trainers have used different taping methods, as well as worked with apparel companies to design posture-cueing compression garments and shoulder and trunk braces.10,11 These garment designs aim to cue the individual in maintaining and improving posture and alignment, specifically targeting the posterior shoulder region to influence scapular positioning and thus attempt to restore normal shoulder kinematics.12 Proper posture is defined as the muscular balance which protects the supporting structures of the body against injury or progressive deformity, while poor posture is defined as a faulty relationship of the various parts of the body which produce increased strain on the supporting structures causing decreased efficiency of balance of the body over its base of support.6 Postural garment designs have been assessed in several studies focusing on alterations in proper posture such as the forward shoulder posture.12,13 Cole et al. found that shoulder posture significantly improved when participants wore a scapular-stabilizing compression garment with increased tension on the straps, as compared to the control compression garment that did not include tension straps.12 Additionally, Ulkar et al. suggested that application of compressive bracing enhances the position of the shoulder complex by increasing the sensation of stability.13
Other postural-cueing compression garments, such as IntelliSkin™, are specifically designed to signal posture and core musculature to activate and attempt to align an individual's shoulders, spine, and trunk.14 The posture-cueing technology in combination with the compression material mimics the effects of Kinesiology Tape (KT) to assist the body in postural control. 14 The IntelliSkin™ posture-cueing compression garment has been shown to provide clinical success among athletes by positively altering athletic performance and reducing injury.14,16,17 During an unpublished longitudinal study presented at the American Orthopaedic Society of Sports Medicine annual meeting, Shepard et al. revealed that over a course of two seasons an improvement in scapular retraction and no days of competition were lost due to injury among National Collegiate Athletic Association (NCAA) Division I male volleyball athletes.17 Additionally, cyclists who wore the IntelliSkin™ posture-cueing compression garment perceived positive benefits for riding posture, post-ride posture, spine discomfort, and post-ride recovery.17 With the need for proper posture as well as proper scapular kinematics during overhead movements, the purpose of this study was to determine the effectiveness of an IntelliSkin™ posture-cueing compression garment compared to a generic performance garment on scapular kinematics during standing. To the authors’ knowledge, analysis of scapular positioning while wearing an IntelliSkin™ posture-cueing compression garment compared to a generic performance garment has yet to be evaluated. This preliminary study attempted to determine if static scapular positioning can be influenced by a posture-cueing compression garment. It was hypothesized that the IntelliSkin™ posture-cueing compression garment would improve scapular positioning among active females in the directions of scapular retraction, upward rotation, and posterior tilting.
Methods
A convenience sample of forty active females (20.7 ± 1.33 yr; 1.68 ± 0.07 m; 67.29 ± 11.25 kg) were recruited to participate. IntelliSkin™ provided female posture-cueing compression garments of varied sizes to serve the participant sample. Participants who reported having any upper extremity injury within the prior six months were excluded. The Institutional Review Board of Auburn University approved all testing protocols and informed consent was obtained prior to any testing.
This was a validation study in a controlled laboratory setting with the objective of comparing scapular position between the IntelliSkin™ posture-cueing compression garment and a generic performance garment. The independent variable for this study was shirt type while the dependent variables were scapular kinematics of retraction, upward rotation, and posterior tilt.
Testing required the participants to stand while wearing two different garments. Participants were verbally instructed to position themselves in a natural standing position as if they were standing in line with hands by side and looking forward. Once the participant was in a natural stance, data were recorded in two conditions: wearing the IntelliSkin™ posture-cueing compression garment (Figure 1) and wearing a generic performance garment (Figure 2). Participants wore each garment only for the period of time it took to collect them standing in a natural standing position. This position was approximately 1-minute for each condition with a 3-minute time difference between testing each garment.
Figure 1.
IntelliSkin™ posture-cueing compression garment.
Figure 2.
Generic performance garment.
Kinematic data were collected at 100 Hz using an electromagnetic tracking system (trakSTAR™, Ascension Technologies, Inc., Burlington, VT, USA) synced with The MotionMonitor® (Innovative Sports Training, Chicago, IL., USA). Participants had a series of 11 electromagnetic sensors affixed to the skin, under their garment, using PowerFlex cohesive tape (Andover Healthcare, Inc., Salisbury, MA) to ensure the sensors remained secure throughout testing. Sensors were attached to the following locations: (1) posterior aspect of the torso at the first thoracic vertebrae (T1) spinous process; (2) posterior aspect of the pelvis at the first sacral vertebrae (S1); (3) top of the head; (4-5) flat, broad portion of the acromion, bilaterally; (6-7) lateral aspect deltoid tuberosity, bilaterally; (8-9) posterior aspect of bilateral distal forearm, centered between the radial and ulnar styloid processes; and (10-11) lateral aspect of each thigh, centered between the greater trochanter and the lateral condyle of the knee. A twelfth, moveable sensor was attached to a plastic stylus used for the digitization of bony landmarks.19,20 To ensure accurate identification and palpitation of bony landmarks, the participant stood in anatomical neutral throughout the duration of the digitization process. Using the digitized joint centers for hips, shoulders, T12-L1, and C7-T1, a link segment model was developed. Joint centers were determined by digitizing the medial and lateral aspect of a joint then calculating the midpoint between those two points. 19,20 The spinal column was defined as the digitized space between C7-T1 and T12-L1.21,22 A rotation method, validated as capable of providing accurate positional data was utilized to estimate the joint centers of the shoulders and hips.23 The shoulder joint centers were calculated from the rotation of the humerus relative to the scapula while the hip joint centers were calculated from the rotation of the femur relative to the pelvis. The rotation method consisted of the investigator stabilizing the joint then passively moving the limb into six different positions in a small, circular pattern.23 Raw data regarding sensor position and orientation were transformed to locally based coordinate systems for each of the representative body segments. For the world axis, the y-axis represented the vertical direction; horizontal and to the right of y was the z-axis; anterior and orthogonal to the plane defined by y and z was the x-axis.
Position and orientation of the body segments were obtained using Euler angle decomposition sequences for the motion of the scapula relative to the thorax (Y-X-Z order). Kinematic data were obtained using Euler angle sequences, consistent with the International Society of Biomechanics standards and joint conventions. 19,20 All raw data were independently filtered along each global axis using a 4th order Butterworth filter with a cutoff frequency of 13.4 Hz.21,22,24 All data were time stamped through The MotionMonitor® and passively synchronized using a data acquisition board.
All statistical analyses were performed using IBM SPSS Statistics 22 software (IBM Corp., Armonk, NY) with an alpha level set a priori at α = 0.05. Prior to analysis, Shapiro-Wilk Tests of Normality were run. Results showed an approximately normal distribution of the standing static posture data. All kinematic variables of the standing static posture in two conditions were analyzed using a 2 (Shirt) x 2 (Side) repeated measures analysis of variance (ANOVA). This ANOVA was applied to the variables of scapula protraction/retraction, upward/downward rotation, and anterior/posterior tilt. For all variables, Mauchly's Test of Sphericity was conducted prior to all analyses, and a Greenhouse-Geisser correction was imposed when sphericity was violated. Paired sample t-tests were used to further examine differences when statistically significant effects were seen.
Results
Means and standard deviations (SDs) for each kinematic variable for the static standing posture are reported in Table 1. Repeated measures ANOVAs of all scapula kinematic variables are revealed in Table 2 and indicate a significant main effect of Shirt for scapula anterior/posterior tilt and a statistically significant Shirt by Side interaction of scapular protraction/retraction. Post-hoc test results are shown in Table 3. There were no statistically significant scapula upward/downward rotation interactions.
Table 1.
Means (Standard deviations) of scapular positional kinematics in degrees
| Variables | Control Garment | Posture-Cueing Garment |
|---|---|---|
| Scapular Protxaction/Retraction | ||
| Right | 1.59 (5.23) | -5.34 (10.61) |
| Left | -2.92 (4.86) | 3.34 (6.17) |
| Scapular Up/Down Rotation | ||
| Right | -0.53 (4.30) | -2.18 (4.90) |
| Left | 0.02 (3.72) | -0.19(6.71) |
| Scapular Anterior/Posterior Tilt | ||
| Right | 2.7 (4.05) | 13.2 (6.82) |
| Left | 3.84 (5.48) | 13.75 Π 1.56) |
Note: Scapular protraction (^/retraction (-); scapular up (+)/down (-); scapular anterior (-)/posterior (+)
Table 2.
Repeated measures ANOVAs of scapular positional kinematics
| Scapular Protraction/Retraction | Scapular Up/Down Rotation | Scapular Anterior/Posterior Tilt | |
|---|---|---|---|
| Shirt | F(1,39) = 0.20, p = 0.67, r2 = 0.01 | F(1,39) = 1.75, p = 0.19? r2 = 0.04 | F(1.13) = 96.45, p < 0.05, r2 = 071 |
| Side | F(1,39) = 1.70, p = 0.20, r2 = 0.04 | F(1,39) = 1.73, p = 0.20, r2 = 0.04 | F(1,39) = 0.61, p = 0.44, r2 = 0.02 |
| Shirt*Side Interaction | F(1,39) = 52.91, p ≤ 0.05, r2 = 0.58 | F(1,39) = 2.20, p = 0.15, r2 = 0.05 | F(1,39) = 0.13, p = 0.73, r2 = 0.01 |
Table 3.
Post Hoc Analysis of Scapular Protraction/Retraction and Scapular Anterior/Posterior Tilt
| Scapular Protraction/Retraction | 95% Cl | t | p-value |
|---|---|---|---|
| Control Garment Right vs Left | 1.67,7.36 | 3.21 | p≤0.01 |
| Posture-Cueing Garment Right vs Left | 4.26, 13.10 | 3.98 | p ≤ 0.01 |
| Control Garment vs Postxire-Cuemg Garment Right | 4.12, 9.75 | 4.99 | p ≤ 0.01 |
| Control Garment vs Posture-Cueing Garment Left | -8.17, -4.34 | -6.62 | p ≤ 0.01 |
| Scapular Anterior/Posterior Tilt | |||
| Control Garment vs Posture-Cueing Garment Right | -12.57, -8.43 | -10.28 | p ≤ 0.01 |
| Control Garment vs Posture-Cueing Garment Left | -13.10, -6.72 | -6.28 | p ≤ 0.01 |
Discussion
The purpose of this study was to determine the effectiveness of an IntelliSkin™ posture-cueing compression garment compared to a generic performance garment on scapular kinematics during static standing. It was hypothesized that IntelliSkin™ posture-cueing compression garment would improve scapular positioning among the female participants. Significant kinematic differences were observed in the natural standing condition in scapular protraction/retraction and anterior/posterior tilt. The participants in the current study presented with greater retraction and posterior tilt while wearing IntelliSkin™ posture-cueing compression garment compared to the control garment. The position of posterior tilt allows for elevation of the acromion and in overhead athletes this position has proven beneficial.7 The control garment showed increased protraction and anterior tilt representing worse scapular positioning.4,25 It has been established that for the most effective movement of the glenohumeral joint, the scapula must move in a coordinated manner with the humerus.4,7,8 The scapula needs to be able to retract, posteriorly tilt and upwardly rotate to facilitate the position of maximum external rotation to efficiently execute overhead tasks. 4,7,8,25 Positioning the scapula in retraction allows for an efficient transfer of energy from eccentric to concentric for explosive acceleration in dynamic overhead movements.4-8,26 Additionally, posterior tilt and upward rotation allows movement of the arm to clear the acromion during forward elevation or abduction.7 Kibler et al. and Myers et al. described the necessity of the scapular retraction position during overhead movements as it allows maximum activation of all muscles, which assist the scapula to maintain a stabilized position.4,9 Therefore, it is postulated that by wearing the IntelliSkin™ posture-cueing compression garment an individual may benefit from an improved position of the scapula during static standing, which could possibly allow for more efficient positioning during overhead tasks.
Similarly, posterior tilting of the scapula has been shown to contribute to elevation of the anterior acromion, thereby decreasing compression of subacromial soft tissues during humeral elevation and abduction.7,8,28 For efficient arm elevation in dynamic upper extremity movements the scapula must posteriorly tilt to allow for acromial elevation.4,9 Since elevation allows for increased subacromial space for full arm elevation, if one is performing dynamic overhead movement without acromioclavicular elevation, there is a relative decrease (or lack of increase) in subacromial space and a greater susceptibility for impingement of the supraspinatus or biceps tendon. By eliciting greater scapular posterior tilt, the IntelliSkin™ posture-cueing compression garment appears to allow for elevation of the acromion that could possibly influence the effectiveness of dynamic movements. Subacromial impingement, which is associated with scapular dyskinesis, is one of the most commonly diagnosed injuries of the upper extremity and causes alteration in both dynamic and static scapular positioning.28-30 Although the focus of this study was not on the muscular activity during the wearing of the IntelliSkin™ posture-cueing compression garment, it is important to note that scapular positioning alterations are associated with muscle activation patterns and strength of scapular stabilizing muscles.28-30 Individuals with subacromial impingement have been found to have increased upper trapezius activation, decreased lower trapezius activation, and decreased serratus anterior activation, thus contributing to inadequate rotation and movement of the scapula. 28-30 These muscular activation patterns cause excessive anterior scapular tilt and loss of upward rotation that may result in injury. 28-30
In addition, although this study found no significant difference between the garments in upward/downward rotation, it is important to note the IntelliSkin™ posture-cueing compression garment did show a non-statistically significant increase in upward rotation. Researchers have shown that upward rotation of the scapula is important for increasing subacromial space, thereby decreasing impingement of soft tissues.7,8,28-30 These improvements may suggest this posture-cueing compression garment assists in scapular proprioception, thus possibly providing biofeedback that could assist in improving static scapular posture.
As the posterior scapular stabilizing musculature works to retract, posteriorly tilt, and upwardly rotate, it is speculated that in turn there is a reduction in pectoralis minor tension and an increase in lower trapezius and serratus anterior activation.4,25 This improved length-tension relationship allows for repositioning of the acromion posteriorly to create more subacromial space and increase shoulder range of motion. Any alteration of scapular positioning in excessive protraction, downward rotation, or anterior tilt can cause pain and may lead to an increased risk of injury. Any pain associated with shoulder mobility may inhibit proper function of scapular movement and therefore lead to chronic shoulder impingement.
Limitations and Future Research
Limitations of this study include a female, undergraduate population. Although participants were healthy and reported not having an upper extremity injury within the prior six months, participants were not screened for scapular dyskinesis, which may have contributed to the greater variety (large standard deviations) of scapular positioning present in the statistical analysis.
Future research should focus on the implications the Intelliskin™ posture-cueing compression garment has in a clinical setting among individuals suffering from scapular dyskinesis. Research should also examine the Intelliskin™ posture-cueing compression garment influence on muscle activation of the shoulder complex and lumbopelvic-hip complex.
Conclusions
Proper posture and scapular positioning are necessary components to ensure appropriate coordination and efficiency of overhead movements. Any deviation from optimal posture and scapula positioning may increase upper extremity injury susceptibility during overhead tasks. The results of the current study indicate that the IntelliSkin™ posture-cueing compression garment improved scapular positioning during static standing posture. However, this study is a preliminary study and further investigation regarding the impact the IntelliSkin™ posture-cueing compression garment may have on scapular positioning during dynamic movements is warranted.
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