Electromyographic analysis of the serratus anterior and trapezius muscles during push-ups on stable and unstable bases in subjects with scapular dyskinesis

Comparison of the Electromyography Activity during Exercises with Stable and Unstable Surfaces: A Systematic Review and Meta-Analysis

The effect of electromyographic (EMG) activity on agonist muscles during exercises performed on stable and unstable surfaces remains uncertain. We aimed to review the literature regarding the comparison of the EMG activity of the agonist muscles of exercises performed on stable and unstable surfaces. Eighty-six studies that evaluated the EMG activity of 1783 individuals during exercises for the lower limbs, upper limbs, and core were included. The EMG activities of the pectoralis major (SMD = 0.28 [95% CI 0.09, 0.47]) and triceps brachii muscles (SMD = 0.45 [95% CI 0.25, 0.66]) were significantly increased when the unstable device was added to the exercise. Likewise, the EMG activity of all core muscles showed a significant increase with the unstable surface during the exercises, such as the rectus abdominis (SMD = 0.51 [95% CI 0.37, 0.66]), external oblique (SMD = 0.44 [95% CI 0.28, 0.61]), internal oblique (SMD = 1.04 [95% CI 0.02, 2.07]), erector spinae (SMD = 0.37 [95% CI 0.04, 0.71]), and lumbar multifidus (SMD = 0.35 [95% CI 0.08, 0.61]). However, the lower limb muscles did not show greater EMG activity during the exercise with unstable surfaces compared to the stable surface. In conclusion, unstable conditions increase the EMG activity of some upper limb and core muscles compared to a stable surface.

Electromyography of scapular stabilizers in people without scapular dyskinesis during push-ups: a systematic review and meta-analysis

Background: Push-up (PU) is widely considered an effective exercise to stabilize the scapular, especially if performed on unstable surfaces. However, available studies cover a wide range of exercise variations and differ according to exercise prescription, muscle selection and study design. Therefore, findings are contradictory, and conclusions for a proper application of the PU are difficult to draw. Objective: To synthesize the available literature on the changes in the activity of the periscapular muscles in individuals without scapular dyskinesis while performing different types of PU on unstable surfaces. Search procedure: Four online databases were searched from the earliest publications to 9 August 2023, using predefined keywords. Out of the 2,850 potential references identified in the primary search, 92 studies were reviewed in detail, of which 38 met the inclusion criteria and were included. Methodological quality was evaluated using a standardized form based on the Newcastle‒Ottawa scale for observational studies. Data combination was performed using CMA (v3), and the random-effects model was used to calculate the standardized mean difference (SMD) with a 95% confidence interval (CI). Results: The use of unstable surfaces in people without scapular dyskinesis led to increased activity of the upper trapezius during the PU (p = 0.017; I2 = 84.95%; SMD = 0.425 [95% CI 0.077, 0.773]) and knee PU (p = 0.023; I2 = 70.23%; SMD = 0.474 [95% CI 0.066, 0.882]) exercises and increased activity of the middle trapezius (MT) (p = 0.003; I2 = 64.50%; SMD = 0.672 [95% CI 0.225, 1.119]) and serratus anterior (SA) (p = 0.039; I2 = 4.25%; SMD = 0.216 [95% CI 0.011, 0.420]) muscles during the push-up plus (PUP) exercise. Conclusion: Using an unstable support base during PU does not necessarily increase the activity of all scapular stabilizers. The amount of muscle activity depends on the type of PU other than the type of support base. If an unstable surface is used, PUP exercise appears to be the most effective modality to increase the quality of training, improve performance, and prevent the occurrence of scapular dyskinesis due to the increase in the activity of the MT and SA muscles. Systematic Review Registration: http://www.crd.york.ac.uk/PROSPERO, CRD42021268465.

Activation of upper limb muscles in subjects with scapular dyskinesis during bench-press and dumbbell fly on stable and unstable surfaces

BACKGROUND

Scapular dyskinesis has been associated with shoulder dysfunctions, and changes in electromyographic (EMG) activity have been reported during the execution of some exercises.

OBJECTIVE

To compare upper limb muscles EMG of asymptomatic subjects with and without scapular dyskinesis during bench-press and dumbbell fly exercise performed on different surface stability conditions.

METHODS

Twenty-eight physically active men were allocated into two groups: Control group (n= 14) and Dyskinesis group (n= 14). The participants performed six repetitions lasting three seconds of the bench press and dumbbell fly exercises with 50% of one-repetition maximum (1RM) on a bench and a Swiss ball. The EMG activity of the pectoralis major, serratus anterior, upper and lower trapezius, anterior deltoid, biceps and triceps muscles were recorded.

RESULTS

No differences were found between groups, regardless of exercise or surface type. Inserting the unstable surface in the supine exercise promoted a slight increase in upper trapezius EMG activity for the control [4.32 (95% CI: 1.04 to 7.60)] and dyskinesis [3.30 (95% CI: 0.34 to 6.27)] groups.

CONCLUSIONS

There is no difference in upper limb muscle EMG activity between subjects with and without scapular dyskinesis. In addition, inserting unstable surfaces did not modify EMG activity.

Electromyographic analysis of the serratus anterior and upper trapezius in closed kinetic chain exercises performed on different unstable support surfaces: a systematic review and meta-analysis

Background

Multiple investigations have compared the electromyographic (EMG) activity of the scapular muscles between stable and unstable support surfaces during the execution of closed kinetic chain exercises. However, these comparative analyses have grouped different unstable surfaces (wobble board, BOSU, therapeutic ball, and suspension equipment) into a single data pool, without considering the possible differences in neuromuscular demand induced by each unstable support surface. This study aimed to analyze the individual effect of different unstable support surfaces compared to a stable support surface on scapular muscles EMG activity during the execution of closed kinetic chain exercises.

Methodology

A literature search was conducted of the Pubmed Central, ScienceDirect and SPORTDiscus databases. Studies which investigated scapular muscles EMG during push-ups and compared at least two support surfaces were included. The risk of bias of included articles was assessed using a standardized quality assessment form for descriptive, observational and EMG studies, and the certainty of the evidence was measured with the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach. A random-effects model was used to calculate effect sizes (ES, Hedge's g).

Results

Thirty studies were selected in the systematic review. Of these, twenty-three low-to-high quality studies (498 participants) were included in the meta-analysis. The main analyzes revealed, in decreasing order, greater UT EMG activity during push-ups performed on suspension equipment (ES = 2.92; p = 0.004), therapeutic ball (ES = 1.03; p < 0.001) and wobble board (ES = 0.33; p = 0.003); without effect on the BOSU ball. In addition, no effect was observed for SA on any unstable device. The certainty of the evidence ranged from low to very low due to the inclusion of descriptive studies, as well as high imprecision, inconsistency, and risk of publication bias.

Conclusion

These findings could be applied in scapular muscles strengthening in healthy individuals. The use of suspension equipment achieves higher UT activation levels. Conversely, the use of any type of unstable devices to increase the activation levels of the SA in shoulder musculoskeletal dysfunctions is not recommended. These conclusions should be interpreted with caution as the available evidence showed a low to very low certainty of evidence, downgraded mostly by inconsistency and imprecision.

Relationship of scapular dyskinesis with the pattern of activation of periescapular muscles during exercise

abstract The aim of the present study was to analyze the activation pattern of the serratus anterior (SA), upper trapezius (UT), and lower trapezius (LT) muscles during periscapular exercises in individuals with and without ED, and to identify which proposed exercise presents greater activation of the periscapular muscles. Fourteen women, aged between 18 and 30 years, participated in this study, divided into a control group (n = 8) and a dyskinesis group (n = 8). The determination of the presence of ED was performed according to the analysis of scapular movement during arm elevation, using the yes/no classification. To evaluate muscle activation, electromyography signals of the SA, UT, and LT muscles were collected during exercise. The exercise protocol was composed of three repetitions of the exercises: punch up, wall slide, and scaption. The results showed that the ED group showed less activation of the AS and TT than the control group. During the scaption and wall slide exercises, the DE group showed less activation of the AS in relation to those without DE. There was no difference in muscle activation between the exercises. That individuals with dyskinesis have less activation of the muscles that control scapular mechanics and that the type of exercise did not influence the activation of the periscapular muscles.

The Effect of Aquabag Use on Muscle Activation in Functional Strength Training

Context: Although training with an aquabag (AB) has gained popularity, there is a lack of evidence of its effect. This study wanted to evaluate the effect of AB implementation on muscle activity of core and lower limb muscles during 3 functional exercises. Design: Cross-sectional observational study. Methods: Twenty healthy subjects performed a squat, lunge, and step-up, while using a stick and an AB. Surface electromyography signals were recorded from the trunk, pelvis, and thigh muscles in the dominant leg. Linear-mixed models were used to analyze the normalized surface electromyography signals. Results: Results demonstrated a significant increase in muscle activity of the back muscles during all 3 exercises (P < .001 to P = .003), abdominals during squat (P = .034) and step-up (P = .046), hamstrings during lunge (P = .008) and step-up (P = .008), and gluteal muscles during lunge (P < .001 and P = .010, respectively). Conclusions: These results indicate that an AB promotes functional strength training by demanding compensatory/additional activity of both stabilizing muscles (specifically in the core and pelvis regions) and prime movers of the lower limb. The authors recommend the use of an AB to enhance training and rehabilitation effects.

Serratus Anterior Fatigue Reduces Scapular Posterior Tilt and External Rotation During Arm Elevation

CONTEXT

Fatigue of the scapular stabilizing muscles resulting from repeated arm motion has been reported to alter scapular kinematics, which could result in shoulder pathology, especially impingement.

OBJECTIVE

This study aimed to examine the effects of fatigue of the serratus anterior muscle on scapular kinematics, specifically, decrease scapular posterior tilt and upward scapular rotation during arm elevation.

DESIGN

Repeated measures.

SETTING

Laboratory.

PARTICIPANTS

Thirty participants were included in the investigation.

INTERVENTIONS

Scapular kinematics and shoulder strength were measured before and immediately following a serratus anterior fatigue protocol.

MAIN OUTCOME

Scapular 3-dimensional position during arm elevation.

RESULTS

No difference in upward rotation of the scapula between prefatigue and postfatigue conditions (ascending: P = .188; descending: P = .798). Scapular posterior tilt decreased during arm elevation following the fatigue protocol between 60° and 90° and 90° and 120° of arm elevation during the ascent (P = .004) and the descent (P = .013). Fatigue by arm elevation angle interaction was found for clavicular elevation during the ascent (P = .050) between 90° and 120° of arm elevation. Scapular internal rotation increased during the ascent (P = .027). There was no difference in clavicular protraction between the prefatigue and postfatigue conditions (ascending: P ≤ .001; descending: P ≤ .001).

CONCLUSION

Fatigue of the serratus anterior decreases posterior scapular tilt and greater clavicular elevation and scapular internal rotation at higher arm elevation angles. These findings are consistent with the scapular kinematic patterns associated with shoulder pain. Improving serratus anterior endurance might delay the changes in scapular kinematics associated with repeated arm motion and shoulder injury mechanisms.

Can the Use of Unstable Surfaces and Instruction for Conscious Abdominal Contraction Increase the EMG Activity of the Periscapular Muscles During the Dynamic Push-Up?

CONTEXT

It is believed that conscious abdominal contraction (CAC) during exercise encourages greater periscapular activation through existing myofascial connections. On the other hand, it is postulated that the use of unstable surfaces would promote greater neuromuscular demand.

OBJECTIVE

To analyze the effect of CAC on periscapular muscle activity during push-up plus exercise on stable and unstable surfaces and to evaluate the correlation between electromyographic (EMG) activity of the serratus anterior (SA) and abdominal oblique muscles.

DESIGN

Repeated-measures design in a single group, pre-post CAC.

SETTING

Biomechanics laboratory.

PARTICIPANTS

Twenty-three male volunteers without a history of lesions in the upper limbs participated in the study.

MAIN OUTCOME MEASURES

Five repetitions of push-ups on stable and unstable surfaces were performed with and without instruction for CAC. The normalized amplitude of the EMG activity was obtained from the muscles of the upper, middle, and lower trapezius, SA upper (SA_5th) and lower (SA_7th) portions, external oblique (EO), and internal oblique.

RESULTS

CAC increased the activity of the EO, internal oblique, middle trapezius, and SA (P < .05) in both surfaces. The use of the unstable surface increased the EMG activity of the EO, SA_7th, and middle trapezius and decreased the EMG activity of the SA_5th. However, all changes observed in EMG signals were of low magnitude, with effect sizes lower than 0.45. There was a weak correlation between the EMG activity of the EO and SA_5th (r = .24) and a strong correlation between the EO and SA_7th (r = .70).

CONCLUSION

The isolated use of CAC or unstable surface during push-up seems to present no practical relevance, but the combined use of these strategies may increase activation of the SA_7th and middle trapezius muscles.

Periscapular activity in subjects with scapular dyskinesis during push-ups on stable and unstable support surfaces

BACKGROUND: The scapular dyskinesis has been described as a sign of scapular instability due to weakness or imbalance of scapular muscles. OBJECTIVE: The aim of this study was to compare the EMG activity of the periscapular and abdominal muscles of asymptomatic subjects without and with scapular dyskinesis type II during a push-up exercise performed on different surface stability conditions. METHODS: Twenty-seven physically active men were allocated into two groups: the Control group (n= 14); and the Dyskinesis group (n= 13). All participants performed three variations of the push-up exercise: Stable, Push-up with hand instability, and Push-up with hand and feet instability. The EMG activity of serratus anterior, upper (UT), middle (MT) and lower (LT) trapezius, external oblique (EO) and rectus abdominis (RA) was recorded during each task. RESULTS: The control group showed an increase in MT activity (mean difference -3.46 to 8.66) under both instability conditions compared to stable push-ups (p< 0.001). The comparison between groups showed that the control group had higher MT activity (mean difference -10.07 to 13.82) compared to the dyskinesis group under unstable conditions (p< 0.012). CONCLUSION: The insertion of unstable surfaces increased MT activity in the control group only. The insertion of the unstable surface, either the hands or the footrest, did not provide significant effects for the other muscles.

Differences in scapular motion and parascapular muscle activities among patients with symptomatic and asymptomatic rotator cuff tears, and healthy individuals

Background

Altered scapular motion is thought to be one of the factors associated with the development of symptomatic rotator cuff tears. However, the differences in kinematics and muscle activities of scapular upward/downward rotation between patients with symptomatic and asymptomatic tears are unclear. The purpose of this study was to compare the differences in kinematics and muscle activities of scapular rotation among patients with symptomatic and asymptomatic tears, and healthy individuals.

Methods

Twenty-three patients with rotator cuff tears and 9 healthy individuals (healthy group) participated in this study. Based on a visual analog scale (VAS, 0-100 mm), the patients were divided into symptomatic (13 patients; VAS ≥20 mm) and asymptomatic (10 patients; VAS <20 mm) groups. Scapular upward rotation was measured with a digital inclinometer. Elasticities of the upper trapezius, levator scapulae, and rhomboid major were assessed by using ultrasound real-time tissue elastography to quantify their muscle activities. All measurements were performed at 0°, 60°, 90°, and 120° of active arm elevation in the scapular plane.

Results

Scapular upward rotation was significantly less in the symptomatic group (9.4° ± 5.6°) compared with the asymptomatic group (15.7° ± 6.0°; P = .022) at 90° of arm elevation. The activity of the levator scapulae was significantly higher in the symptomatic group compared with the asymptomatic and healthy groups (P = .013 and P = .005, respectively) at 90° of arm elevation. The activity of the upper trapezius was significantly higher in the symptomatic group compared with the healthy group (P = .015) at 120° of arm elevation.

Conclusion

Patients with symptomatic rotator cuff tears showed less scapular upward rotation and higher activity of the levator scapulae at 90° of arm elevation compared to patients with asymptomatic rotator cuff tears.

Use of unstable exercises in periscapular muscle activity: A systematic review and meta-analysis of electromyographic studies

BACKGROUND

The use of unstable surfaces has been proposed to increase the neuromuscular demand. This strategy has been adopted to generate an increase in the activity of periscapular muscles due to its role in the stabilization of the scapula. However, the influence of this instability on the EMG activity remains uncertain. The aim of this study was to analyze the effects of using unstable surfaces on the EMG activity of the periscapular muscles.

METHODS

A comprehensive search in the PubMed, EMBASE, SCIELO, Web of Science, SCOPUS, Cochrane and LILACS databases was undertaken from their year of inception up to December 2019. Studies which directly investigated the EMG activity of periscapular muscles in healthy individuals while performing exercises for the upper limbs in stable and unstable conditions.

RESULTS

A total of 33 studies which evaluated a total of 678 healthy individuals were found according to the eligibility criteria. A meta-analysis identified that the EMG activity of the upper trapezius showed a trivial increase with the insertion of the unstable surface (P = 0.04; SMD = 0.14 [95%CI 0.00, 0.27]). No significant effects were observed on the middle trapezius (P = 0.10) and lower trapezius (P = 0.25). A decrease of the anterior serratus EMG activity with a small effect size was observed by implementing an unstable surface (P = 0.01; SMD = -0.21 [95%CI -0.36, -0.05]).

CONCLUSION

The use of unstable surfaces generated a trivial increase in the upper trapezius activity, and a slight decrease in the anterior serratus activity. No effect was observed on the middle and lower trapezius.

Scapular Dyskinesis: From Basic Science to Ultimate Treatment

Background: This study intends to summarize the causes, clinical examination, and treatments of scapular dyskinesis (SD) and to briefly investigate whether alteration can be managed by a precision rehabilitation protocol planned on the basis of features derived from clinical tests. Methods: We performed a comprehensive search of PubMed, Cochrane, CINAHL and EMBASE databases using various combinations of the keywords “Rotator cuff”, “Scapula”, “Scapular Dyskinesis”, “Shoulder”, “Biomechanics” and “Arthroscopy”. Results: SD incidence is growing in patients with shoulder pathologies, even if it is not a specific injury or directly related to a particular injury. SD can be caused by multiple factors or can be the trigger of shoulder-degenerative pathologies. In both cases, SD results in a protracted scapula with the arm at rest or in motion. Conclusions: A clinical evaluation of altered shoulder kinematics is still complicated. Limitations in observing scapular motion are mainly related to the anatomical position and function of the scapula itself and the absence of a tool for quantitative SD clinical assessment. High-quality clinical trials are needed to establish whether there is a possible correlation between SD patterns and the specific findings of shoulder pathologies with altered scapular kinematics.

Use of unstable surfaces and conscious abdominal contraction on the activity of periscapular muscles

Background/aims

Core training has been recommended in shoulder rehabilitation programs. However, the evidence on this topic is still scarce. The aim of this study was to investigate the effect of conscious abdominal contraction combined with unstable surfaces on electromyographic activity of periscapular muscles during the plus phase of a push-up.

Methods

A total of 20 male participants (22.8 ± 2.5 years) were evaluated. Electromyographic signals were collected from the upper, middle and lower trapezius, serratus anterior, and external and internal oblique muscles during push-up exercises on a stable and unstable surface with and without the conscious abdominal contraction. Each participant performed four variations of the plus phase of a push-up.

Results

The results demonstrated that the conscious abdominal contraction caused an increase in the electromyographic activity of external oblique, internal oblique, serratus anterior and lower trapezius muscles (P≤0.008). The unstable surface caused only a relevant increase in electromyographic activity of the abdominal muscles (P≤0.025). Combining the two strategies did not increase the electromyographic activity of any muscles (P≥0.238).

Conclusions

The conscious abdominal contraction seems to be a viable strategy to increase the electromyographic activity of the periscapular muscles.

Pain, motion and function comparison of two exercise protocols for the rotator cuff and scapular stabilizers in patients with subacromial syndrome

STUDY DESIGN

Randomized clinical trial.

INTRODUCTION

Eccentric exercise (EE) was shown to be an effective treatment in tendinopathies. However, the evidence of its effectiveness in subacromial syndrome (SS) is scarce. Moreover, consensus has not been reached on whether best results for SS are obtained by means of EE with or without pain.

PURPOSE OF THE STUDY

The purpose of this is to compare the effect on pain, active range of motion (AROM), and shoulder function of an exercise protocol performed with pain <40 mm Visual Analog Scale (VAS) and without pain, in patients with SS.

METHODS

Twenty-two subjects (mean age: 59 years [Q1 = 48.50-Q3 = 70], 54.5% women) were randomized into a not-painful EE group (NPEE; G0: n = 11) and a painful EE group (PEE; G1: n = 11). The intervention lasted 4 weeks. Pain was recorded using VAS; AROM was measured using a goniometer; and shoulder function using the modified Constant-Murley Score (CMS) before and after intervention.

RESULTS

All dependent variables improved significantly in both groups (P < .05): NPEE VAS median: pretest = 55.0 posttest = 28.0; CMS median: pretest = 36.0 posttest = 65.0. PEE VAS median: pretest = 37.0 posttest = 12.0; CMS median: pretest = 35.0 posttest = 59.0. The comparison between groups showed no significant differences, with small effect size values (VAS = 0.09; CMS = 0.21; AROM = 0.12-0.43).

DISCUSSION

In contrast to the previous findings, our results suggest that PEE do not add benefit in SS patients compared to NPEE.

CONCLUSION

Our results suggest that both interventions are effective in terms of pain, function, and shoulder AROM. Furthermore, PEE does not provide greater benefits. Further studies are needed with long-term follow-up to reinforce these results.

Serratus Anterior and Upper Trapezius Electromyographic Analysis of the Push-Up Plus Exercise: A Systematic Review and Meta-Analysis

CONTEXT

Whereas the serratus anterior (SA) and the upper trapezius (UT) work as a force couple for scapular motion, weakness of the SA and overactivation of the UT are often present in overhead athletes with shoulder dysfunction. Therefore, researchers addressing an intramuscular imbalance between the SA and UT have focused on finding exercises that target the weak SA and minimally activate the UT.

OBJECTIVE

To compare the effectiveness of push-up plus (PUP) exercise variants based on the electromyographic (EMG) activity of the SA and UT.

DATA SOURCES

A systematic search of PubMed and Scopus between January 1, 2000, and March 31, 2008.

STUDY SELECTION

Studies of PUP exercises that involved EMG analysis.

DATA EXTRACTION

We assessed study quality using the Critical Appraisal Skills Program. For the systematic analysis, the following data were extracted: (1) author, year, and study design; (2) participant characteristics; (3) type of PUP intervention; (4) EMG outcome measures; and (5) main results. For the meta-analysis, the EMG data of the SA and UT were calculated using the mean difference of EMG activity with a 95% confidence interval.

DATA SYNTHESIS

Based on 19 studies with 356 participants, different hand positions (the distance between the hands, shoulder-flexion angle, and elbow-flexion angle) and different lower extremity positions variably affected the activation of the SA and UT during the PUP exercise. Also, when participants performed the PUP on an unstable surface compared with a stable surface, UT activity increased 2.74% (95% confidence interval = 0.07%, 5.41%).

CONCLUSIONS

The standard PUP exercise elicited high EMG activity of the SA. Participants generated higher SA and lower UT EMG activity when they performed the PUP exercise on a stable surface in full elbow extension, with the hands placed shoulder-width apart, shoulder-flexion angles of 110° or 120°, and the ipsilateral lower extremity lifted.

Electromyographic activity of the serratus anterior and pectoralis major during isometric scapular protraction at different resistance intensities in subjects with and without a winged scapula

BACKGROUND

During maximal isometric protraction, it is important to determine the optimal resistance intensity in subjects with a winged scapula, for inducing isolated activity of the serratus anterior against the pectoralis major, which is activated as a synergistic muscle. The aim of the present study was to determine electromyographic activities of the serratus anterior and pectoralis major muscles during isometric shoulder protraction at different levels in subjects with and without a winged scapula.

METHODS

Thirty male subjects performed isometric shoulder protraction in a sitting position at different resistance intensity levels (100%, 80%, and 60% of maximal protraction strength). Surface electromyographic data of the serratus anterior and pectoralis major muscles were gathered simultaneously using fixed instrumentation to measure isometric shoulder protraction.

FINDINGS

Muscle activity of the serratus anterior in subjects without a winged scapula was significantly greater than that of subjects with a winged scapula across all three conditions, whereas muscle activity of the pectoralis major was lower in subjects without a winged scapula. In addition, winged scapula muscle activity corresponding to maximal protraction was significantly greater than that in the submaximal condition.

INTERPRETATION

In a clinical setting, submaximal resistance can be more optimal than maximal effort during isometric shoulder protraction in individuals with a winged scapula.

Superior Training-Specific Adaptations With an 8-Week Yoak Push-up Training Program

Lima, C, Li, Y, Low, JL, Herat, N, and Behm, DG. Superior training-specific adaptations with an 8-week yoak push-up training program. J Strength Cond Res 32(9): 2409-2418, 2018-There are few progressive metastability training programs in the literature. The purpose of this study was to investigate changes in strength, endurance, muscle activation, and neuromuscular efficiency after an 8-week progressive, push-up training program under stable and unstable conditions. Nineteen male and female recreationally trained participants performed twice per week, an 8-week push-up training program, using either a relatively unstable suspension system (Yoak) or under stable conditions. Participants were tested in 2 separate sessions before and after training for chest press maximal voluntary isometric contraction (MVIC) forces, and unstable and stable push-up endurance. Participants were tested during all testing measures for anterior deltoid, biceps brachii (BB), triceps brachii (TB), and serratus anterior (SA) electromyography (EMG) activity. The training progression consisted of altering the suspension configurations, push-up height, and increasing the number of sets (1-3 sets). The stable group performed 153.3 and 33.8% less repetitions than the Yoak group when performing push-ups on the Yoak device or stable floor, respectively (p = 0.03). Training-induced MVIC forces were 9.2% (p = 0.03) greater for the Yoak vs. the stable group. Regarding neuromuscular efficiency, the Yoak group decreased (30.4%; p = 0.01) and stable group increased (97.8%; p = 0.02) antagonist BB EMG activity from pre- to post-training. Both groups decreased the TB fatigue index from pre- to post-training. Nevertheless, Yoak group demonstrated 12.5% (p = 0.09) and 8.9% (p = 0.02) lower fatigue indexes with TB and SA, respectively, than the stable group. These findings suggest that Yoak training demonstrates superior improvements over stable training for push-up endurance, neuromuscular efficiency, MVIC, and fatigue index.

Rehabilitation for Shoulder Instability - Current Approaches

Background:

The shoulder relies predominantly on dynamic muscular control to provide stability. Successful treatment is highly dependent upon the correct clinical diagnosis, identification of anatomical structural defects and abnormal movement patterns so that rehabilitation programs can be designed accordingly and individualised to the patient.

Method:

A systematic outline is provided to guide the clinician on how to identify muscular insufficiencies both local to the shoulder joint and global muscles that can influence shoulder instability. Management is based on expert experience and current literature.

Results:

The Stanmore classification helps to correctly diagnose the type of instability and prioritise management. Symptom modification tests can help to guide management, however assessing individual muscle groups local to glenohumeral control is also recommended.

Conclusion:

Physical and psychosocial factors can influence motor control in the presence of pain and injury. A multi-disciplinary approach is required to avoid recurrence of symptoms with rehabilitation focusing on kinetic chain, scapular and gleno-humeral control.

EMG activity of the serratus anterior and trapezius muscles during the different phases of the push-up plus exercise on different support surfaces and different hand positions

[Purpose] The appropriate exercise prescription is crucial for achieving scapular stability and providing successful rehabilitation, and the Push-up Plus (PuP) exercise has an important role in shoulder rehabilitation. Consequently, this study examined the effect of support surface stability, hand positioning, and phase of exercise, on the trapezius and serratus anterior muscle contractions as well as on the EMG ratio of the upper/lower trapezius. [Subjects and Methods] Thirteen healthy male volunteers participated in this study. The subjects performed the PuP exercise on stable and unstable supporting surfaces with three different hand orientations. During the PuP exercise, the muscle activities of the upper (UT) and lower (LT) trapezius, as well as the serratus anterior (SA) were measured and expressed as percentages of maximum voluntary isometric contraction (%MVIC). [Results] The EMG activities of UT and LT were statistically greater during the push-up phase compared to the plus phase of the exercise. The contrary was recorded for the activity of the SA. SA was affected by the support surface as well as by the hand positioning. [Conclusion] The results suggest that different phases of the PuP exercise require different muscle stability actions with corresponding activations of appropriate muscle fibers. A detailed prescription of the required phase of the exercise can more effectively activate the scapula-thoracic musculature.