Lower Trapezius Activity Research Articles

Correlation between Cranio-Vertebral Angle and Muscle Activity According to Body Movements in Forward Head Posture

The purpose of this study is to determine the correlation between FHP and how it may affect muscle activity during raising the arm and loss of body balance, 40 young people participated. All subjects will have their cranio-vertebral angle (CVA) and muscle activity of the serratus anterior (SA), upper trapezius (UT), and lower trapezius (LT), static balance index, and central pressure excursion index (CPEI) measured. Muscle activity was measured using TeleMyo 2400(Noraxon U.S.A., Inc., Scottsdale, AZ, USA), and static balance indicators and CPEI were measured using the MatscanVersaTek system (Tekscan Inc., MA). Spearman correlation analysis was used to determine the correlation between variables. CVA and SA, UT, and LT all showed significant correlation, positive correlation with SA(r=0.429/p=0.006) and LT(r=0.377/p=0.017), and negative correlation with UT(r=-0.473/p=0.007) (Table 2). CVA showed a moderate level of negative correlation with AREA(r=0.-0.420 /p=0.007) and L-R distance(r=-0.508 /p=0.000) among balance indicators, and did not show a significant correlation with CPEI (Table 3). In people with more severe FHP, SA, and LT muscle activity tended to be lower, UT muscle activity tended to be higher, and static balance ability was lower. According to the results of this study, FHP can have a negative effect on various factors of the body, such as arm movement and static balance, suggesting that establishing correct posture is necessary to prevent secondary physical problems.

Shoulder Rotation Affects Trapezius Muscle Activity During Shoulder Horizontal Abduction.

Shoulder horizontal abduction exercise in the prone position is effective for strengthening the lower trapezius muscle. However, this exercise is difficult for patients with acute pain or those undergoing initial rehabilitation because of the postural characteristics of the exercise. This study aimed to (1) investigate the effect of a shoulder horizontal abduction exercise when performed with a different amount of shoulder rotation on the trapezius muscle activation and scapular anterior/posterior tilt angle and (2) evaluate the effect of shoulder rotation on the acromiohumeral distance while sitting. Fifteen healthy men performed shoulder horizontal abduction exercise in three shoulder positions (internal rotation, neutral rotation, and external rotation). During exercises, we measured trapezius muscle activity using an electromyography system and scapular anterior/posterior tilt angle using an inclinometer application. We also measured the acromiohumeral distance using real-time ultrasonography before the exercises. Increases in lower trapezius and middle trapezius muscle activities and a decrease in scapular anterior tilt occurred in shoulder external rotation compared with other positions (p<0.001). Shoulder external rotation also significantly increased acromiohumeral distance in the sitting position (p<0.05). We propose that shoulder external rotation effectively and safely increases middle and lower trapezius muscle activities during the sitting shoulder horizontal abduction exercise.

Effects of Exercise and Neuromuscular Electrical Stimulation on Lower Trapezius Muscle Activity in Individuals with Round Shoulder Posture

Effects of Exercise and Neuromuscular Electrical Stimulation on Lower Trapezius Muscle Activity in Individuals with Round Shoulder Posture

Comparing Three Wearable Brassiere Braces Designed to Correct Rounded Posture.

Rounded shoulder posture (RSP) causes shoulder pain and can lead to shoulder impingement and thoracic outlet syndromes, ultimately resulting in a frozen shoulder. Altered scapular positions in RSP patients affect muscle activity. Many studies have explored methods to correct and prevent RSP, including shoulder braces, muscle strengthening, stretching, and inhibition techniques. Using a shoulder brace reduces RSP and improves shoulder discomfort and function, similar to conventional rehabilitation. However, despite their effectiveness, these braces are bulky and inconvenient, which makes continuous daily wear challenging. This is especially true for women who are sensitive to their appearance. To address this issue, methods have been developed to convert women's underwear bra straps into braces. This study aimed to evaluate the immediate effects of three underwear-mounted rounded shoulder braces and to identify the brace that is most effective in decreasing RSP and upper trapezius (UT) muscle activity and increasing lower trapezius (LT) muscle activity in patients with RSP. The study included 18 patients with an RSP. The RSP amount and UT and LT muscle activities were measured before and after three interventions. The interventions were scapular posterior tilting (SPT) exercises with the X strap, X + 8 strap, and inner brace. Compared with the baseline value, the RSP amount was significantly lower with the three braces. The RSP was significantly lower with the X + 8 strap and the inner brace than with the X strap. The inner brace showed significantly lower UT muscle activity than those with the X strap and X + 8 straps and significantly greater LT muscle activity than that with the X + 8 strap. These results show underwear-mounted braces as a potential RSP solution, but long-term sustainability and improving comfort, especially for those concerned about appearance, require further research and development.

The acute effects of vibratory stimuli during exercise on the sensorimotor control of the shoulder complex: A pilot study.

Functional stability of the shoulder requires a balance of active forces, passive forces, and control subsystems of the joint complex. Although whole-body vibration enhances shoulder muscle function and proprioception, the impact of vibration on the sensorimotor control of the shoulder joint remains unclear. To investigate the acute effect of vibratory stimuli on the sensorimotor control of the shoulder joint. Fifteen male participants (age, 22.7 ± 2.3years) were included and performed the exercise in a modified push-up position with partial weight-bearing on a vibration platform with and without vibratory stimuli. The vibration protocol included six sets lasting for 30s each with a 30-s rest between sets. The main outcome measures included the upper limb static stability test, Upper Quarter Y Balance Test (UQYBT), and electromyography data of the upper limb. Vibratory stimuli resulted in an increased UQYBT score (all directions; P< 0.01) and infraspinatus, serratus anterior, and lower trapezius muscle activity (P< 0.05) between pre- and post-exercise versus the control condition. Stabilometric parameters showed no significant interaction between condition and time. Vibratory stimuli could maximize training benefits while limiting injury risk for athletes. Our findings could guide the development of rehabilitation programs for patients with shoulder instability.

Effect of Trunk Position on Trapezius Muscle Activity and Ratio during Performing Modified Seated Cable Row Exercise

Background Changes in trunk angle as part of modifying the seated cable row exercise (MSCRE) are associated with trapezius muscle activity and ratio. Purpose This study aimed to determine the changes in muscle activity and ratio for the upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT) muscles during the MSCRE in healthy participants without shoulder pain. Study design Cross-sectional study Methods We included participants who were 23 healthy individuals aged 23–39 years. The participants performed a pulling motion three times during the MSCRE at each of the following trunk angles: upright posture 0°, forward lean 30°, and backward lean 20°. Surface electromyography was performed for the UT, MT, and LT muscles during the 5-s isometric contraction, with the participant in a preset position, while the muscle activity was normalized with the maximal voluntary isometric contraction using the manual muscle test. Results The UT and LT muscle activities showed significant differences in angle (<italic>p</italic>&lt;0.05); the highest muscle activity was observed for the UT at backward lean 20° and LT at forward lean 30°. The UT/MT and UT/LT ratios showed significant differences in angle (<italic>p</italic>&lt;0.05), with the highest values observed at backward lean 20° for both the ratios. Conclusions These results suggest that the forward lean 30° trunk angle was most suitable for the MSCRE in the selective strengthening of the LT muscle, indicating that the trunk should be tilted forward during exercise for normal and balanced recovery of trapezius muscle activities in shoulder rehabilitation.

Comparison of the Lower Trapezius Muscle Activity during Three Different Shoulder Flexion Exercises in Healthy Subjects

Comparison of the Lower Trapezius Muscle Activity during Three Different Shoulder Flexion Exercises in Healthy Subjects

Effects of Intended Scapular Posterior Tilt Motion on Trapezius Muscle Electromyography Activity.

The intended scapular motion is a strategy to strengthen the lower trapezius (LT). However, few studies have explored the effects of the intended scapular posterior tilt motion on selective LT activation. Thus, the present study investigated the effect of the intended scapular posterior tilt on the electromyography (EMG) activity of trapezius muscles during prone shoulder horizontal abduction (PSHA). Eighteen asymptomatic men performed three types of PSHA: (1) preferred PSHA, (2) PSHA with the intended scapular posterior tilt, and (3) PSHA with the intended scapular posterior tilt and trunk extension. EMG activity of the upper trapezius (UT), middle trapezius (MT), and LT were measured during PSHAs. Scapular posterior tilt angle, with and without the intended scapular posterior tilt, were measured using inclinometer. The results indicated that LT muscle activity increased when scapular posterior tilt was applied with and without trunk extension (14–16%), compared to the preferred condition, during PSHA (p < 0.05). However, the addition of trunk extension to PSHA with the intended scapular posterior tilt increased the UT muscle activity (28%) and the UT/LT (29%) and UT/MT (31%) ratios (p < 0.05). The scapular posterior tilt angle was higher (15%) when applying the intended scapular posterior tilt (p = 0.020). These findings suggest that the intended scapular posterior tilt may be a useful strategy for selective LT muscle activation.

The effects of shoulder posture on neck and shoulder musculoskeletal loading and discomfort during smartphone usage

While using their smartphone, users tend to adopt awkward neck and shoulder postures for an extended duration. Such postures impose the risk of MSDs on those body parts. Numerous studies have been undertaken to examine neck posture; however, few studies have investigated shoulder postures. This study examined various shoulder postures during smartphone use and their effect on neck and shoulder kinematics, muscle loading, and neck/shoulder discomfort. Thirty-two asymptomatic young adult smartphone users randomly performed texting tasks for 3 min at four different shoulder flexion angles (15°, 30°, 45°, and 60°), while maintained a neck posture in the neutral position (0° neck flexion angle). Measures were taken of neck and shoulder muscle activity of the cervical erector spinae (CES), anterior deltoid (AD), upper trapezius (UT) and lower trapezius (LT), and kinematic data (angle, distance and gravitational moment). Results showed AD and LT muscle activity significantly increased when the shoulder flexion angle increased with an opposite effect on CES and UT. A recommended shoulder posture was identified as 30° flexion, as this yielded the best compromise between activation levels of the four muscles studied. This angle also induced the lowest neck/shoulder discomfort score. The findings suggest smartphone users hold their device at approximately 30° shoulder flexion angle with their neck in a neutral posture to reduce the risk of shoulder and neck musculoskeletal disorders when smartphone texting. Relevance to industrySmartphone use in the manufacturing and service industries is an integral part of work and useful means of communication tool. Awkward postures during extensive smartphone use impose an increased risk of both neck and shoulder musculoskeletal disorders. Shoulder flexion angles need consideration when making recommendations about safe work postures during smartphone use.

EMG activity of the serratus anterior and trapezius muscles during elevation and PUSH UP exercises

BackgroundElevation and push up (Pu) exercises are considered to be beneficial for the rehabilitation of shoulder complex pathology. Despite their clinical utility, there is a lack of evidence comparing scapulothoracic muscles recruitment during these exercises. ObjectiveTo evaluate the EMG activity of upper trapezius (UT), Lower Trapezius (LT), Upper Serratus anterior (USa) and Lower Serratus anterior (LSa) muscles during a variety of elevation and Pu exercises. MethodsThirteen healthy participants (non, athlete, male, mean ± standard deviation; age: 21.1 ± 1.8 years; height: 1.80 m ± 0.04; weight: 79 ± 12 kg) were assessed. EMG data was collected during Scaption, wall slide and elevation with external rotation (EleEr) with and without load. Pu classic, Pu plus (PuP) on stable/unstable surfaces and Pu with shoulder internal rotation were also assessed. ResultsUT had a significant higher activity during ‘Scaption load’ (p < .05) and LT in ‘EleEr load’ and ‘Scaption load’ (p < .05). USa and LSa had a significant higher activity on ‘PuP unstable surface’ and ‘PuP internal rotation’ compared to elevation exercises (p < .05). Scaption had greater activity ratio compared to the other exercises on UT/LT (p < .05). Pu variations had lower results in UT/USa and UT/LSa ratios compared to shoulder elevation exercises (p < .05). ConclusionsElevation exercises produce significant effects on upper and lower trapezius activation while Pu exercises on Sa muscles. Wall slide exercise notes the lowest activation in all muscles. A descending order of muscle activity during different variations of elevation and Pu exercises is provided in order to guide exercise selection in everyday clinical practice.

The Application of Double Elastic Band Exercise in the 90/90 Arm Position for Overhead Athletes

Traditional exercises performed with the shoulder in the position of 90° abduction and external rotation with elbow flexion (90/90) while using a single elastic band showed moderate activity of both the lower trapezius (LT) and infraspinatus (IS) muscle. The purpose of this study was to investigate activity of the teres minor (TMi) and the LT muscles during standing external rotation exercise with the shoulder in the 90/90 position with 2 elastic bands in both the frontal and the scapular plane. TMi, IS, and LT muscle activities will vary depending on whether the shoulder is positioned in the frontal or scapular plane with the application of 2 elastic bands. Also, the serratus anterior (SA) and teres major (TMa) muscles will produce different muscular activity patterns during exercises performed with 2 elastic bands in the frontal plane compared with the TMi and LT muscles. Controlled laboratory study. Level 4. A total of 21 collegiate baseball players volunteered to participate. The electromyography (EMG) activities of the TMi, IS, LT, SA, TMa, middle deltoid (MD), posterior deltoid, and upper trapezius (UT) muscles were measured with the 90/90 arm position during both isometric and oscillation resistance exercises with 2 elastic bands oriented in the frontal and scapular planes. A significant difference was observed in EMG activity of both the TMi and the LT muscles between single and double elastic band applications in the frontal plane (P < 0.05). In contrast, EMG activity of the IS, SA, and TMa muscles was significantly increased in the scapular plane compared with the frontal plane (P < 0.05). The standing 90/90 position effectively increased both TMi and LT muscle EMG activity with the double elastic band in the frontal plane while minimizing UT and MD muscle activity. EMG activity of the IS, SA, and TMa muscles increased with exercise in the scapular plane as compared with the frontal plane. Oscillation movement under double elastic band application differentiated external rotator muscle and scapular muscle activities between the frontal and scapular plane during the 90/90 exercise in the frontal plane compared with the scapular plane. Clinicians can utilize each of the scapular and frontal positions based on their desired focus for muscular activation.

Analysis of Scapular Muscle EMG Activity During Elastic Resistance Oscillation Exercises From the Perspective of Different Arm Positions.

Little is known about the optimal exercise intensity and the effects of arm position on elastic resistance exercise. The purpose of this study was to investigate scapular muscle activity in different arm positions utilized during standing elastic resistance exercise. Lower trapezius (LT), serratus anterior (SA), and infraspinatus (IS) muscle activity will vary across arm positions above shoulder level. Also, oscillation resistance exercise will result in increased muscle activity compared with isometric contraction. Controlled laboratory study. Level 4. A total of 19 uninjured male collegiate baseball players volunteered to participate in this study. The electromyography (EMG) activity of the LT, upper trapezius (UT), middle deltoid (MD), SA, and IS muscles was determined using surface EMG in 3 arm positions: diagonal pattern 1 (D1), 120° of shoulder abduction (120), and 90° shoulder abduction with external rotation and elbow flexion (90/90) during both isometric contraction and oscillation resistance exercise. No difference in EMG activity of the LT muscle was found between the 120 and 90/90 position. However, the 120 position increased UT and MD muscle activity significantly more than those of the 90/90 position. The D1 arm position significantly increased SA muscle activity more than the 120 and 90/90 positions while the LT muscle activity was nearly silent. The standing 90/90 position effectively generated both LT and IS muscle EMG activity while minimizing both UT and MD muscle activity. The use of oscillation movements under elastic loading can create high muscle activation in the LT muscle without an adverse effect of the humeral head position and scapular rotation.

ELECTROMYOGRAPHIC ANALYSIS OF THE SCAPULAR DYSKINESIS TEST IN A BASEBALL PITCHER WITH A SLAP LESION: A CASE REPORT

The return to play percentage of baseball pitchers who have undergone isolated superior labrum anterior-posterior (SLAP) repair has been reported to be less than 60%. Scapular dyskinesis (SD), characterized by scapular prominence during dynamic scapulohumeral movements, may be used to assist in diagnosing a baseball pitcher with shoulder pathology including a SLAP lesion. The purpose of this case report was to describe the use of the SD test to assess the scapular muscles and report EMG findings in a college baseball pitcher diagnosed with a Type 2 posterior SLAP lesion. The subject was a NCAA-D1 senior collegiate baseball right hand 3/4 slot pitcher (21 years old) with a primary complaint of pain in the anterior portion of the shoulder during the entire fall practice season, which was attributed to labral surgery performed when he was a senior in high school. No positive clinical testing of the patient was found including: the sulcus sign, tests of gross instability, and the load & shift test. A Type II posterior SLAP lesion was identified via magnetic resonance imaging. The subject presented with glenohuemral internal rotation deficit (GIRD). The SD test identified moderate to severe prominence of scapular medial boarder in shoulder flexion/extension (FLX/EXT). Furthermore, surface EMG analyses indicated that the lower trapezius (LT) muscle was abruptly inhibited on the dominant side during the descending phase of FLX, compared with the non-dominant side. Additionally, a remarkably higher ratio of upper trapezius to LT muscle EMG activity on the dominant side compared to that of the non-dominant side was identified during the descending phase from flexion. After identification of SD, an off season conservative treatment program allowed him to compete in his last college baseball season, appearing 22 times out of the bullpen in which he was credited four wins with a 3.70 earned run average (ERA) in 41.1 innings in 57 games. The SD test may play a critical role in identifying rehabilitation potential and guide the focus of the rehabilitation program to improve scapulothoracic stability and mobility for unilateral repetitive overhead athletes. Particularly the descending phase during sagittal plane motion (FLX/EXT) may effectively accentuate the scapular prominence during movement, portentially due to LT muscle activity inhibition. 5 Case Report.

Increased Upper and Lower Trapezius Muscle Activities During Rest in Side-Lying Position in Young Adults with Forward Head Posture

Forward head posture (FHP) is a problem with muscle imbalance around neck and shoulder girdle. The FHP might be a silent threat for young adults in their later stages of life. An impact of the FHP on muscle activities in upright posture has been well established; however, how it influences neck and shoulder muscle activities in side lying-position has been still elusive. This study was aimed to investigate electrical muscle activities (% maximum voluntary contraction, %MVC) on both upper and lower sides of 4 neck and shoulder muscles—sternocleidomastoid (SCM), upper trapezius (UT), middle trapezius (MT) and lower trapezius (LT) using surface electromyography (EMG) in 34 participants (normal head posture (NHP) group, aged 21.24±0.97 years old, n=17; and FHP group, aged 20.83±1.20 years old, n=17). Each participant performed side-lying position with a self-selected pillow for 5-min of acclimatization and another 12-min for EMG recordings. Results showed that there was no significant difference between %MVC on upper and lower sides of all muscles in both groups. In contrast, the %MVC of the trapezius muscles on the upper side of the FHP group were significantly higher than the NHP group i.e., 1.26±0.76 vs 0.79±0.44 in UT; and 3.06±1.86 vs 1.74±1.14 in LT, respectively. Despite symmetrical activation of bilateral muscles can be seen in both groups; however, the FHP could induce over activation of UT and LT while resting in side-sleeping position. Therefore, selective technique to minimize muscle activation during resting position might be required as preventive regimen for this group of young adults

Kinesiotaping for scapular dyskinesis: The influence on scapular kinematics and on the activity of scapular stabilizing muscles

Scapular dyskinesis is observed in 61% of overhead athletes (Burn et al., 2016). For most of them, it remains asymptomatic. However, scapular dyskinesis is considered a risk factor for shoulder injury by some authors (Clarsen et al., 2014). The aim of this study is to explore the effectiveness of kinesiotaping in modifying scapular kinematics and peri-scapular muscle activity in dyskinetic athletes. The 3-dimensional position and orientation of the scapula as well as the activation of upper trapezius, lower trapezius and serratus anterior were recorded in twenty asymptomatic athletes during shoulder movements (flexion and abduction), in loaded and unloaded conditions and in three circumstances (standard, kinesiotaping 1, kinesiotaping 2). A significant decrease between 9 and 12% in upper trapezius activity was observed with kinesiotaping 1 and 2. Lower trapezius activity was slightly increased with kinesiotaping 1 while it was significantly decreased about 15–20% with kinesiotaping 2. No change was observed in serratus anterior activity, for either kinesiotaping 1 or 2. Considering scapular kinematics, both kinesiotaping 1 and 2 significantly increased posterior tilt and upward rotation. External rotation was decreased with kinesiotaping 2, in comparison to standard condition. Kinesiotaping, and especially taping 1, seems to be an effective method for changing periscapular muscle activity and scapular kinematics.

Arm Lifting Exercises for Lower Trapezius Muscle Activation

Background: Lower trapezius muscle function is important for the prevention and treatment of shoulder injuries. However, scapular posterior tilt movement has been overlooked in lower trapezius strengthening exercise programs. Objective: To examine the effects of prone arm lifting with scapular posterior tilt (PALSPT) on trapezius muscles. Design: Crossover study Methods: 17 healthy males were recruited for participation in this study. Participants performed backward rocking diagonal arm lifting (BRDAL) and PALSPT. To train participants in scapular posterior tilt movements for PALSPT, visual biofeedback of scapular movements was provided using a motion sen­sor. Electromyography (EMG) activities of the middle and lower trapezius were recorded using a surface EMG system. Differences in middle and lower trapezius muscle activity between BRDAL and PALSPT exercises were ana­lyzed. Results: Lower trapezius muscle activity was significantly greater during PALSPT than during BRDAL (p=.006). Although greater EMG activity was observed in the middle trapezius during PALSPT than during BRDAL, this dif­ference was not significant (p=.055). Conclusions: The results of the present study indicate that scapular posterior tilt movements must be considered in lower trapezius muscle strengthening programs.

SCAPULAR MUSCLE ELECTROMYOGRAPHIC ACTIVITY DURING ABDUCTION EXERCISES IN THE SCAPULAR PLANE IN THREE POSITIONS

Hyperactivity of the anterior deltoid (AD) has been shown to produce adverse effects on subacromial space width as a result of humeral head superior translation during rehabilitation exercises used with overhead athletes. Also, the importance of the ratio of upper trapezius (UT) to lower trapezius (LT) muscle activity has been examined during rehabilitation exercises particularly for those who develop scapular dyskinesis. The purpose of this study was to investigate the level of LT and SA muscle activity during scapular plane elevation (scaption) in three positions while maintaining a moderate level of AD muscle activity. A secondary purpose was to identify the ratio of UT to LT muscle activity during the varied scaption exercises. The authors hypothesized that the activation of these two important muscles and the UT/LT ratio would vary with exercise position and throughout the range of scapular plane elevation. Fourteen active young subjects performed scaption exercises in three different positions: standing (STAN), quadruped (QUAD), and prone (PRON) with three different weight loads: 0 kg, 1.8 kg, and 4.1 kg. Surface electromyography (EMG) was used to record muscular activity. Tested muscles included the UT, LT, SA, AD, and posterior deltoid muscles on the dominant side. QUAD scaption exercises with a load of 1.8 kg at 4 sec after the initial movement activated the LT muscle up to 49% of maximum voluntary isometric contraction (MVIC) while maintaining a moderate level of AD muscle activity (30% MVIC). STAN scaption exercises with the weight load of 1.8 kg at 3 sec after the initial movement activated 43% MVIC of the SA muscle while maintaining a moderate level of AD muscle activity (39% MVIC). The PRON condition generated significantly less SA muscle activity with both 1.8 and 4.1 kg weight loads than during the QUAD condition. The ratios of UT to LT muscle activity were significantly less in QUAD than those of STAN up to 4 sec after the initial movement. No significant difference was observed in the UT/LT ratio between QUAD and PRON conditions. QUAD scaption exercise effectively activated both LT and SA muscles without over activating the AD and produced favorable ratios of UT to LT muscle activity. Descriptive Cohort Study, Level 4.

Effects of the Safety Squat Bar on Trunk and Lower-Body Mechanics During a Back Squat.

Hecker, KA, Carlson, LA, and Lawrence, MA. Effects of the safety squat bar on trunk and lower-body mechanics during a back squat. J Strength Cond Res 33(7S): S45-S51, 2019-The purpose of this study was to determine whether the safety squat bar (SSB) alters the mechanics and muscle activity of a back squat compared with a standard barbell (ST). Motion and muscle activation of the trunk and lower extremity were measured while 12 competitive powerlifters (8 males, 4 females, age 31.5 ± 6.3 years, body mass 88.1 ± 20.7 kg, competitive lifting experience 3.3 ± 2.8 years) squatted 3 sets of 5 repetitions at 75% of their 3 repetition maximum (3RM). Mean muscle activity and peak joint flexion angles were measured for the trunk and one lower extremity. A repeated-measures analysis of variance (p = 0.05) revealed an 11.3% decrease in 3RM when using the SSB. When using the SSB, there was a decrease in trunk and hip flexion (7.3 and 5.7° respectively) and a 50.3% increase in lower trapezius activation. However, using the SSB decreased activation of the rectus abdominis (46.3%), medial hamstring (17.1%), lateral hamstring (15.1%), vastus lateralis (9.3%), and medial gastrocnemius (18.8%). Squatting with the SSB resulted in a more upright trunk angle, which places less stress on the lower back, a commonly injured area when squatting. Decreases in lower-extremity muscle activation are likely due to the decreased load used, suggesting that the SSB may not be as effective as a standard bar to increase lower-extremity strength. However, the increase in the lower trapezius with the lighter load suggests that midback musculature may be challenged more by the SSB than a standard barbell.

The utility of Sysmex XN body fluid mode for cell count in body fluids

While using their smartphone, users tend to adopt awkward neck and shoulder postures for an extended duration. Such postures impose the risk of MSDs on those body parts. Numerous studies have been undertaken to examine neck posture; however, few studies have investigated shoulder postures. This study examined various shoulder postures during smartphone use and their effect on neck and shoulder kinematics, muscle loading, and neck/shoulder discomfort. Thirty-two asymptomatic young adult smartphone users randomly performed texting tasks for 3 min at four different shoulder flexion angles (15°, 30°, 45°, and 60°), while maintained a neck posture in the neutral position (0° neck flexion angle). Measures were taken of neck and shoulder muscle activity of the cervical erector spinae (CES), anterior deltoid (AD), upper trapezius (UT) and lower trapezius (LT), and kinematic data (angle, distance and gravitational moment). Results showed AD and LT muscle activity significantly increased when the shoulder flexion angle increased with an opposite effect on CES and UT. A recommended shoulder posture was identified as 30° flexion, as this yielded the best compromise between activation levels of the four muscles studied. This angle also induced the lowest neck/shoulder discomfort score. The findings suggest smartphone users hold their device at approximately 30° shoulder flexion angle with their neck in a neutral posture to reduce the risk of shoulder and neck musculoskeletal disorders when smartphone texting.Smartphone use in the manufacturing and service industries is an integral part of work and useful means of communication tool. Awkward postures during extensive smartphone use impose an increased risk of both neck and shoulder musculoskeletal disorders. Shoulder flexion angles need consideration when making recommendations about safe work postures during smartphone use.

Trapezius muscle activation levels and ratios during scapular retraction exercises: A comparative study between patients with subacromial impingement syndrome and healthy controls

BackgroundLittle is known about trapezius muscle activities during scapular retraction exercises in patients with subacromial impingement syndrome. The aim of this study was to compare upper trapezius, middle trapezius and lower trapezius muscle activity and upper/middle and upper/lower trapezius ratios between patients with subacromial impingement syndrome and healthy individuals during six scapular retraction exercises. MethodsTwenty-two patients with subacromial impingement syndrome and 22 healthy individuals participated. Upper, middle, and lower trapezius activities were measured by surface electromyography, while the participants performed six scapular retraction exercises at different shoulder abduction angles in a standing position. Upper/middle and upper/lower trapezius ratios were also calculated. Repeated-measures analyses of variance were performed to determine whether muscle activation levels and ratios differed between groups during exercises. FindingsThere was no significant exercise × group interactions for upper, middle, and lower trapezius activation levels and upper/middle and upper/lower trapezius ratios (P > .05). A main effect for the exercise was observed for the upper/middle and upper/lower trapezius ratios (P < .05). InterpretationCompared to healthy individuals, patients with subacromial impingement syndrome did not exhibit different upper, middle, and lower trapezius activity and had similar upper/middle and upper/lower trapezius ratios during the various scapular retraction exercises. Therefore, scapular retraction exercises with various shoulder abduction could be safely offered for the patients with subacromial impingement syndrome since it does not lead to abnormal compensatory trapezius muscle activity. If the goal is to minimize upper/middle and upper/lower trapezius ratios, the scapular retraction exercises at 0° shoulder abduction may be used in early stage of shoulder rehabilitation.