Infraspinatus Isolation During External Rotation Exercise at Varying Degrees of Abduction

2018 ◽  
Vol 27 (4) ◽  
pp. 334-339 ◽  
Author(s):  
Gareth Ryan ◽  
Heather Johnston ◽  
Janice Moreside
Keyword(s):  
Surface Electromyography ◽  
Repeated Measures ◽  
Muscle Activation ◽  
External Rotation ◽  
Patient Comfort ◽  
Abduction Angle ◽  
Shoulder Injury ◽  
Subacromial Space ◽  
Common Component ◽  
Rehabilitation Programs

Context:External rotation (ER) strengthening exercises are a common component of shoulder injury prevention and rehabilitation programs. They are primarily intended to target the infraspinatus muscle, based on its role in glenohumeral stabilization and inferior humeral glide. ER also recruits the posterior deltoid, which can be undesirable due to its role in subacromial space narrowing.Objective:To determine the angle of humeral abduction that maximizes the infraspinatus to posterior deltoid activation ratio (INFRA/PD) during ER.Design:Within-subjects repeated-measures controlled lab trial.Participants:A total of 10 healthy participants (5 males, 5 females) aged 21 (0.67) years participated in the study.Intervention:7 consecutive repetitions of ER at 7 different abduction angles ranging from 0° to 90°, with resistance normalized to 3% body mass.Main Outcome Measures:Surface electromyography was performed on the infraspinatus, middle deltoid, and posterior deltoid. Surface electromyography data were processed to determine absolute muscle activation as well as INFRA/PD at each abduction angle. Group means were compared between abduction angles using 1-way analysis of variance.Results:Abduction significantly reduced overall infraspinatus activity but increased posterior deltoid activity (P < .01). Average and peak INFRA/PD decreased as the angle of abduction increased (P < .001 andP < .01, respectively).Conclusion:Our findings suggest that ER should be performed in 0° of abduction to maximize infraspinatus isolation. Slight abduction, such as placing a towel under the humerus, as recommended by some clinicians, may improve patient comfort, but did not increase infraspinatus isolation in this study.

scholarly journals Influence of Body Position on Shoulder and Trunk Muscle Activation During Resisted Isometric Shoulder External Rotation

2018 ◽  
Vol 10 (4) ◽  
pp. 355-360 ◽  
Author(s):  
David A. Krause ◽  
Lucas G. Dueffert ◽  
Jaclyn L. Postma ◽  
Eric T. Vogler ◽  
Amy J. Walsh ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Muscle Activation ◽  
External Rotation ◽  
Body Position ◽  
Trunk Muscle ◽  
Trunk Muscles ◽  
Emg Activity ◽  
Convenience Sample ◽  
Overhead Athletes ◽  
Significant Difference

Background: External rotation (ER) strengthening of the shoulder is an integral component of rehabilitative and preventative programs for overhead athletes. A variety of shoulder ER strengthening exercises are reported, including those intended to integrate the core musculature. The purpose of this study was to examine ER torque and electromyographic (EMG) activation of shoulder and trunk muscles while performing resisted isometric shoulder ER in 3 positions (standing, side lying, and side plank). Hypothesis: Significantly greater force and shoulder muscle activation would be generated while side lying given the inherent stability of the position, and greater trunk muscle activation would be generated in the less stable plank position. Study Design: Quasi-experimental repeated-measures study. Level of Evidence: Level 5. Methods: A convenience sample of 25 healthy overhead recreational athletes (9 men, 16 women) participated in this study. EMG electrodes were placed on the infraspinatus, posterior deltoid, middle trapezius, multifidi, internal obliques, and external obliques. EMG signals were normalized to a maximal isometric contraction. Participants performed resisted isometric ER in standing, side-lying, and side plank positions. Results were analyzed using a repeated-measures analysis of variance with post hoc Bonferroni corrections (α = 0.05). Results: There was no significant difference in ER torque between positions (α = 0.05). A significant difference in EMG activity of shoulder and trunk musculature between positions was found in 7 of the 8 muscles monitored. Significantly greater EMG activity in the infraspinatus, middle trapezius, and the nondominant external and internal obliques was found in the side plank position as compared with standing and side lying. Conclusion: While there was no difference in ER torque between the 3 exercise positions, EMG activity of the shoulder and trunk muscles was dependent on body position. Clinical Relevance: If a clinician is seeking to integrate trunk muscle activation while performing shoulder ER strengthening, the side plank position is preferred as compared with standing or side lying.

scholarly journals Neuromuscular shoulder activity during exercises with different combinations of stable and unstable weight mass

2019 ◽  
Author(s):  
Omar Baritello ◽  
Mina Khajooei ◽  
Tilman Engel ◽  
Stephan Kopinski ◽  
Andrew Quarmby ◽  
...  
Keyword(s):  
Muscle Activation ◽  
External Rotation ◽  
Muscular Activity ◽  
Shoulder Injury ◽  
Serratus Anterior ◽  
Maximal Voluntary Isometric Contraction ◽  
Cross Sectional ◽  
Neuromuscular Activity ◽  
Custom Made ◽  
Flexion Extension

Abstract Background:Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass (UWM) affects the muscular activity of the shoulder stabilizers. Aim of the study was to assess neuromuscular activity of dynamic shoulder stabilizers under four conditions of stable and UWM during three shoulder exercises. It was hypothesized that a combined condition of weight with UWM would elicit greater activation due to the increased stabilization demand. Methods:Sixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 sec.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different training conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root mean square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (SR : U.TA/L.TA; U.TA/SA) and contraction (CR : concentric/eccentric) ratios were analyzed (paired t-test; a = 0.05; Bonferroni adjusted a = 0.008). Results:PWG showed significantly greater muscle activity for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG (p> 0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The SR ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the CR ratio in all exercises and for all muscles. Conclusion:Higher weight generated greater muscle activation whereas an UWM raised the neuromuscular activity, increasing the stabilization demands. Especially in the In/Ex rotation, an unstable weight mass increased the RMS%MVIC and SR ratio. This might improve training effects in shoulder prevention and rehabilitation programs.

scholarly journals Muscle Activation and Perceived Loading During Rehabilitation Exercises: Comparison of Dumbbells and Elastic Resistance

2010 ◽  
Vol 90 (4) ◽  
pp. 538-549 ◽  
Author(s):  
Lars L. Andersen ◽  
Christoffer H. Andersen ◽  
Ole S. Mortensen ◽  
Otto M. Poulsen ◽  
Inger Birthe T. Bjørnlund ◽  
...  
Keyword(s):  
Repeated Measures ◽  
Muscle Activation ◽  
Musculoskeletal Diseases ◽  
External Rotation ◽  
Emg Activity ◽  
Absolute Maximum ◽  
Maximal Voluntary Isometric Contraction ◽  
Emg Amplitude ◽  
Elastic Resistance ◽  
Resistance Exercises

BackgroundHigh-intensity resistance training plays an essential role in the prevention and rehabilitation of musculoskeletal injuries and disorders. Although resistance exercises with heavy weights yield high levels of muscle activation, the efficacy of more user-friendly forms of exercise needs to be examined.ObjectiveThe aim of this study was to investigate muscle activation and perceived loading during upper-extremity resistance exercises with dumbbells compared with elastic tubing.DesignA single-group, repeated-measures study design was used.SettingExercise evaluation was conducted in a laboratory setting.ParticipantsSixteen female workers (aged 26–55 years) without serious musculoskeletal diseases and with a mean neck and shoulder pain intensity of 7.8 on a 100-mm visual analog scale participated in the study.MeasurementsElectromyographic (EMG) activity was measured in 5 selected muscles during the exercises of lateral raise, wrist extension, and shoulder external rotation during graded loadings with dumbbells (2–7.5 kg) and elastic tubing (Thera-Band, red to silver resistance). The order of exercises and loadings was randomized for each individual. Electromyographic amplitude was normalized to the absolute maximum EMG amplitude obtained during maximal voluntary isometric contraction and exercise testing. Immediately after each set of exercise, the Borg CR10 scale was used to rate perceived loading during the exercise.ResultsResistance exercise with dumbbells as well as elastic tubing showed increasing EMG amplitude and perceived loading with increasing resistance. At the individually maximal level of resistance for each exercise—defined as the 3 repetitions maximum—normalized EMG activity of the prime muscles was not significantly different between dumbbells (59%–87%) and elastic tubing (64%–86%). Perceived loading was moderately to very strongly related to normalized EMG activity (r=.59–.92).LimitationsThe results of this study apply only for exercises performed in a controlled manner (ie, without sudden jerks or high acceleration).ConclusionsComparably high levels of muscle activation were obtained during resistance exercises with dumbbells and elastic tubing, indicating that therapists can choose either type in clinical practice. The Borg CR10 can be a useful aid in estimating intensity of individual rehabilitation protocols.

Surface Electromyography of the Internal and External Oblique Muscles During Isometric Tasks Targeting the Lateral Trunk

2020 ◽  
pp. 1-6
Author(s):  
Allison L. Kinney ◽  
Matthew Giel ◽  
Brady Harre ◽  
Kyle Heffner ◽  
Timothy McCullough ◽  
...  
Keyword(s):  
Surface Electromyography ◽  
Muscle Activation ◽  
Maximum Voluntary Contraction ◽  
Voluntary Contraction ◽  
Trunk Muscle ◽  
Muscle Performance ◽  
Trunk Muscles ◽  
The Novel ◽  
Rehabilitation Programs ◽  
Hip Abduction

Context: Tasks that activate the lateral trunk muscles are clinically relevant in athletic and rehabilitation programs. However, no electromyography studies have compared tasks aimed at lateral trunk muscle activation. Objective: To compare the activation magnitudes of the internal and external obliques between 4 tasks targeting recruitment of the lateral trunk muscles, including the proposal of a novel assessment. Design: Comparative laboratory study. Setting: University-based biomechanics laboratory. Participants: Sixty-three participants (35 females, age = 23.6 [2.0] y, height = 1.72 [0.10] m, mass = 70.7 [14.4] kg, body mass index = 23.6 [2.86] kg/m2). Intervention(s): Surface electromyography data were recorded bilaterally from the internal and external obliques while the participants performed 2 maximum voluntary contraction tasks followed by 4 isometric tasks. The isometric tasks included feet-elevated side-supported, trunk-elevated side-unsupported, lateral plank, and side-lying hip abduction. Main Outcome Measures: Maximum voluntary contraction-normalized and integrated muscle activities were calculated for targeted and nontargeted muscles in each task. A side-by-task analysis of variance with Bonferroni correction was conducted. Results: The trunk-elevated side-unsupported task strongly activated the internal (199% maximum voluntary contraction) and external (103%) oblique muscles. The feet-elevated side-supported task strongly activated the internal obliques (205%) but not the external obliques (55%). The lateral plank task successfully activated the internal (107%) and external (72%) obliques, but not at the highest levels of the tested tasks. The side-lying hip abduction task was the least effective at activating either the internal (48%) or external (20%) obliques. Conclusions: We recommend the novel trunk-elevated side-unsupported task for assessing lateral trunk muscle performance. For independent exercise, we recommend the lateral plank task, unless arm or shoulder pathologies are present, whereby the feet-elevated side-supported task may be favorable.

scholarly journals Gluteus Medius Muscle Activation During Isometric Muscle Contractions

2011 ◽  
Vol 20 (2) ◽  
pp. 174-186 ◽  
Author(s):  
Catriona O’Dwyer ◽  
David Sainsbury ◽  
Kieran O’Sullivan
Keyword(s):  
Internal Rotation ◽  
Outcome Measures ◽  
Lower Limb ◽  
Repeated Measures ◽  
Muscle Activation ◽  
External Rotation ◽  
Gluteus Medius ◽  
Isometric Contractions ◽  
Main Effect

Context:Functional subdivisions are proposed to exist in the gluteus medius (GM) muscle. Dysfunction of the GM, in particular its functional subdivisions, is commonly implicated in lower limb pathologies. However, there is a lack of empirical evidence examining the role of the subdivisions of the GM.Objectives:To compare the activation of the functional subdivisions of the GM (anterior, middle, and posterior) during isometric hip contractions.Design:Single-session, repeated-measures observational study.Setting:University research laboratory.Participants:Convenience sample of 15 healthy, pain-free subjects.Intervention:Subjects performed 3 maximal voluntary isometric contractions for hip abduction and internal and external rotation on an isokinetic dynamometer with simultaneous recording of surface electromyography (sEMG) activity of the GM subdivisions.Main Outcome Measures:sEMG muscle activity for each functional subdivision of the GM during each hip movement was analyzed using a 1-way repeated-measures ANOVA (post hoc Bonferroni).Results:The response of GM subdivisions during the 3 different isometric contractions was significantly different (interaction effect; P = .003). The anterior GM displayed significantly higher activation across all 3 isometric contractions than the middle and posterior subdivisions (main effect; both P < .001). The middle GM also demonstrated significantly higher activation than the posterior GM across all 3 isometric contractions (main effect; P = .027). There was also significantly higher activation of all 3 subdivisions during both abduction and internal rotation than during external rotation (main effect; both P < .001).Conclusions:The existence of functional subdivisions in the GM appears to be supported by the findings. Muscle activation was not homogeneous throughout the entire muscle. The highest GM activation was found in the anterior GM subdivision and during abduction and internal rotation. Future studies should examine the role of GM functional subdivisions in subjects with lower limb pathologies.

Influence of Feet Position and Execution Velocity on Muscle Activation and Kinematic Parameters During the Inclined Leg Press Exercise

2021 ◽  
pp. 194173812110163
Author(s):  
Isabel Martín-Fuentes ◽  
José M. Oliva-Lozano ◽  
José M. Muyor
Keyword(s):  
Repeated Measures ◽  
Muscle Activation ◽  
External Rotation ◽  
Vastus Lateralis ◽  
Maximum Velocity ◽  
Lower Limbs ◽  
Vastus Medialis ◽  
Kinetic Chain ◽  
Kinematic Parameters ◽  
Leg Press

Background: The leg press is one of the most typical exercises for strengthening the lower limbs. The objectives of this study were to compare 5 inclined leg press exercise conditions, varying the feet width stance (100% or 150% hip width), the feet rotation (0° or 45° external rotation) on the footplate and using 2 different movement velocities (MVs; maximum intended, and 2:2 seconds steady-paced velocities) to determine their effect on muscle activation as well as on the kinematic parameters between trained men and trained women. Hypotheses: There will be no significant differences in muscle activation with regard to the feet position. The higher the MV, the greater the muscle activation. Study Design: A cross-sectional cohort study. Level of Evidence: Level 3. Methods: A repeated-measures between-group design was performed to examine muscle activation and kinematic parameters for the different conditions between gender groups. The level of significance was set at alpha = 0.05 for all statistical analyses. Results: Muscle activation presented no differences between conditions regarding feet width stance or feet rotation. Furthermore, muscle activation was greater during positive phases than negative phases of the exercise for all conditions and was also greater under maximum intended velocity conditions compared with steady-paced conditions. Otherwise, the muscle activation pattern presented slight differences by gender. In men, the greatest muscle activation was for the vastus medialis, followed by the vastus lateralis (VL), rectus femoris (RF), and gluteus medialis (GMED), while in women, the greatest muscle activation was for the vastus medialis, followed by the RF, VL, and GMED. Finally, greater mean propulsive velocity, maximum velocity, maximum power, and footplate displacement values were reported for men than for women under all the conditions. Conclusion: The inclined leg press exercise produces the highest muscle activation in the vastus medialis, regardless of the velocity, feet stance, or gender. Clinical Relevance: Given that there are no differences in muscle activation regarding the feet stance, a participant’s preferred feet stance should be encouraged during the inclined leg press exercise. Furthermore, the MV would preferably depend on the session objective (a training or a rehabilitation program), being aware that there is greater muscle activation at higher speeds. The inclined leg press exercise could be performed as a closed kinetic chain exercise when the main objective is to activate the vastus medialis.

scholarly journals Gender Differences in Shoulder Performance Fatiguability are Affected by Arm Position, Dominance and Muscle Group

2021 ◽  
Author(s):  
Cosmin Horobeanu ◽  
Samuel A. Pullinger ◽  
Julien Paulus ◽  
Cristian Savoia ◽  
Fui Yen Wong ◽  
...  
Keyword(s):  
Muscle Activation ◽  
Frontal Plane ◽  
Comparative Investigation ◽  
Muscle Group ◽  
Abduction Angle ◽  
Shoulder Injuries ◽  
Rehabilitation Programs ◽  
Shoulder Muscles ◽  
Significant Difference ◽  
Muscle Groups

Abstract Background: Injury prevalence data, muscle strength, and fatiguability have shown differences between males and females. In addition, arm spatial orientation affects muscle activation and strength of the shoulder muscles, but little to no research has been conducted in relation to the shoulder rotator muscles comparing men and women. Therefore, the main aim of of this study was to perform a comparative investigation between two arm spatial orientations (45⁰ and 90⁰ of abduction in frontal plane) during a fatigue assessment of shoulder internal rotator (IR) and external rotator (ER) muscles. Secondly, the interaction of gender and dominance with muscular performance was assessed.Methods: Forty healthy sedentary participants, 20 males and 20 females took part in this study. Participants performed a fatigue resistance protocol consisting of 30 consecutive maximal concentric contractions of the IR and ER shoulder muscles in a supine position at a speed of 180⁰/s. The upper limb was abducted to an angle of 45⁰ or 90⁰ in frontal plane and each subject was tested on dominant and nom-dominant side, counterbalanced in order of administration. Performance measures of Induced Fatigue (IF), Cumulated Performance (C.Perf) and Best repetition (BR) were calculated and used for further analysis.Results: There was a significant difference in angle, with higher values observed in 90⁰ of abduction compared to 45⁰ of abduction for C.Perf by 6% and 7% for BR (P < 0.0005) in the ER. The dominant arm was significantly higher than the non-dominant arm for C.Perf with higher values of 9.7% at 90⁰ of abduction compared to 45⁰ of abduction (P = 0.017) and BR with higher values of 4.2% at 90⁰ of abduction compared to 45⁰ of abduction (P < 0.0005) in the ER in males. There was a significant difference in muscle group, with higher values observed in the IR for C.Perf (88.2%), BR (22.5%) and IF (36.9%); at 90⁰ of abduction compared to 45⁰ of abduction in males (P < 0.0005). Significantly higher values were observed for C.Perf in females between the dominant and non-dominant arm for the IR and ER (P < 0.0005). The females showed significantly lower values for C.Perf (47.74-55.10%) and BR (47.30-53.41%) in both muscle groups, both testing positions and in both limbs, when compared to males (P < 0.05)Discussion: It was established that an increase in the abduction angle will influence the strength of ER muscles in favour of the 90° angle without any differences observed in IR muscles. Males were found to produce approximately double the amount of work done compared to females, but the amount of induced fatigue was no different between both groups. Conclusion: Therefore, these findings are useful for clinicians throughout the monitoring of rehabilitation programs in sedentary individuals following shoulder injuries.

scholarly journals Neuromuscular shoulder activity during exercises with different combinations of stable and unstable weight mass

2019 ◽  
Author(s):  
Omar Baritello ◽  
Mina Khajooei ◽  
Tilman Engel ◽  
Stephan Kopinski ◽  
Andrew Quarmby ◽  
...  
Keyword(s):  
Muscle Activation ◽  
External Rotation ◽  
Muscular Activity ◽  
Shoulder Injury ◽  
Serratus Anterior ◽  
Maximal Voluntary Isometric Contraction ◽  
Cross Sectional ◽  
Neuromuscular Activity ◽  
Custom Made ◽  
Flexion Extension

Abstract Background Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass affects the muscular activity of the shoulder stabilizers (ST). Aim of the study was to analyzed the neuromuscular activity of the dynamic ST under four combinations of stable and unstable weight mass during three shoulder exercises. It was hypothesized that a combined condition of weight with unstable mass would elicit significantly greater activation due to the increased stabilization demand. Methods Sixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 sec.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different training conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root mean square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (SR: U.TA/L.TA; U.TA/SA) and contraction (CR: concentric/eccentric) ratios were analyzed (paired t-test;Bonferroni adjusted α=0.008) Results PWG showed significantly greater activation for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG (p>0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The SR ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the CR ratio in all exercises and for all muscles. Conclusion Higher weight generated greater muscle activation whereas an unstable weight mass behavior raised the neuromuscular activity, increasing the stabilization demands. Especially in the In/Ex rotation, an unstable weight mass increased the RMS%MVIC and SR ratio. This might improve training effects in shoulder prevention and rehabilitation programs.

scholarly journals Neuromuscular shoulder activity during exercises with different combinations of stable and unstable weight mass

2019 ◽  
Author(s):  
Omar Baritello ◽  
Mina Khajooei ◽  
Tilman Engel ◽  
Stephan Kopinski ◽  
Andrew Quarmby ◽  
...  
Keyword(s):  
Muscle Activation ◽  
External Rotation ◽  
Muscular Activity ◽  
Shoulder Injury ◽  
Serratus Anterior ◽  
Maximal Voluntary Isometric Contraction ◽  
Cross Sectional ◽  
Neuromuscular Activity ◽  
Custom Made ◽  
Flexion Extension

Abstract Background Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass affects the muscular activity of the shoulder stabilizers. Aim of the study was to analyzed the neuromuscular activity of the dynamic shoulder stabilizers under four combinations of stable and unstable weight mass during three shoulder exercises. It was hypothesized that a combined condition of weight with unstable mass would elicit significantly greater activation due to the increased stabilization demand. Methods Sixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 sec.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different training conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root mean square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (SR: U.TA/L.TA; U.TA/SA) and contraction (CR: concentric/eccentric) ratios were analyzed (paired t-test; α=0.05; Bonferroni adjusted α=0.008) Results PWG showed significantly greater muscle activity for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG (p>0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The SR ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the CR ratio in all exercises and for all muscles. Conclusion Higher weight generated greater muscle activation whereas an unstable weight mass behavior raised the neuromuscular activity, possibly due to increased stabilization demands. Application of an unstable weight mass may be beneficial to improve training effects in shoulder prevention and rehabilitation programs.

scholarly journals Neuromuscular shoulder activity during exercises with different combinations of stable and unstable weight mass.

2020 ◽  
Author(s):  
Omar Baritello ◽  
Mina Khajooei ◽  
Tilman Engel ◽  
Stephan Kopinski ◽  
Andrew Quarmby ◽  
...  
Keyword(s):  
Muscle Activation ◽  
External Rotation ◽  
Muscular Activity ◽  
Shoulder Injury ◽  
Serratus Anterior ◽  
Maximal Voluntary Isometric Contraction ◽  
Cross Sectional ◽  
Neuromuscular Activity ◽  
Custom Made ◽  
Flexion Extension

Abstract Background:Recent shoulder injury prevention programs have utilized resistance exercises combined with different forms of instability, with the goal of eliciting functional adaptations and thereby reducing the risk of injury. However, it is still unknown how an unstable weight mass affects the muscular activity of the shoulder stabilizers.Aim of the study was to analyze the neuromuscular activity of the dynamic shoulder stabilizers under four conditions of stable and unstable weight mass during three shoulder exercises. It was hypothesized that a combined condition of weight with unstable mass would elicit significantly greater activation due to the increased stabilization demand.MethodsSixteen participants (7 m/9 f) were included in this cross-sectional study and prepared with an EMG-setup for the: Mm. upper/lower trapezius (U.TA/L.TA), lateral deltoid (DE), latissimus dorsi (LD), serratus anterior (SA) and pectoralis major (PE). A maximal voluntary isometric contraction test (MVIC; 5 sec.) was performed on an isokinetic dynamometer. Next, internal/external rotation (In/Ex), abduction/adduction (Ab/Ad) and diagonal flexion/extension (F/E) exercises (5 reps.) were performed with four custom-made-pipes representing different training conditions. First, the empty-pipe (P; 0.5 kg) and then, randomly ordered, water-filled-pipe (PW; 1 kg), weight-pipe (PG; 4.5 kg) and weight + water-filled-pipe (PWG; 4.5 kg), while EMG was recorded. Raw root mean square values (RMS) were normalized to MVIC (%MVIC). Differences between conditions for RMS%MVIC, scapular stabilizer (SR: U.TA/L.TA; U.TA/SA) and contraction (CR: concentric/eccentric) ratios were analyzed (paired t-test; a = 0.05; Bonferroni adjusted a = 0.008) ResultsPWG showed significantly greater muscle activity for all exercises and all muscles except for PE compared to P and PW. Condition PG elicited muscular activity comparable to PWG (p > 0.008) with significantly lower activation of L.TA and SA in the In/Ex rotation. The SR ratio was significantly higher in PWG compared to P and PW. No significant differences were found for the CR ratio in all exercises and for all muscles.ConclusionHigher weight generated greater muscle activation whereas an unstable weight mass behavior raised the neuromuscular activity, increasing the stabilization demands. Especially in the In/Ex rotation, an unstable weight mass increased the RMS%MVIC and SR ratio. This might improve training effects in shoulder prevention and rehabilitation programs.Trial Registration: not applicable

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