The effect of shoulder core exercises on isometric torque of glenohumeral joint movements in healthy young females (original) (raw)
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https://ijshr.com/IJSHR\_Vol.5\_Issue.3\_July2020/IJSHR\_Abstract.0021.html, 2020
Introduction: Increased range of motion at glenohumeral joint makes it susceptible to injury and instability. It was found that subjects with total glenohumeral rotation>1650 had less isometric external rotation and internal rotation muscle strength than those with glenohumeral rotation was<1650. Beyond normal 1800 of shoulder range of motion indicates joint instability hence aim was to find out the muscle strength difference of internal rotation and external rotation with total arc of glenohumeral rotation. Material and Methods: 50 young healthy subjects (43 females,7 males) of 18to25 years were included. Initially dominant shoulder internal and external rotation passive range of motion was recorded with help of universal goniometer as well by motion analyzer in supine position. Shoulder rotator muscle strength was measured using hand held dynamometer in supine position in neutral and at end range of rotation motions. Data analysis and Results: Karl Pearson’s correlation was used to evaluate correlation between strength and shoulder range of rotation for right side. Out of 50,37 females and 6 males showed >1800 whereas 6 females and 1 male showed<1800 of total shoulder internal and external range of motion. It was observed that subjects with<1800 shoulder rotation showed moderate correlation with muscle strength where as those with>1800 shoulder rotation range showed no or weak correlation with rotator muscle strength. Conclusion: As the total arc of glenohumeral rotation increases beyond normal limits of 0-1800 there is a decreased strength of internal rotator and external rotator muscles as compared to total arc of glenohumeral rotation less than 1800.
Activation of shoulder muscles in healthy men and women under isometric conditions
Journal of Electromyography and Kinesiology, 2004
Purpose: Due to the low osseous lead of the shoulder joint a large portion of the shoulder muscles, in addition to executing movements, deals with stabilising tasks. This requires a permanent readjustment of the intermuscular co-ordination of all involved muscles. The aim of the study was to verify the existence of gender dependent differences in intramuscular co-ordination patterns of shoulder muscles.
Background. Isokinetic strength imbalance is a risk factor for movement dysfunctions and injuries related to shoulder complex. The effects of recreational weightlifting on developing the imbalances between the shoulder muscles are not yet known. Objectives. To investigate the isokinetic concentric shoulder muscle strength values (peak torque normalized to body weight) in recreational weightlifters (RWL) and to compare the shoulder muscles agonist/antagonist ratios with nonweightlifters. Methods. Thirty male RWL with mean age, weight, height, and body mass index (BMI) of 21.56 years, 84.25 kg, 175.34 cm, and 26.51 kg/m 2 , respectively, matched with nonweightlifters served as a control group. The normalized concentric peak torque values of shoulder flexors, extensors, abductors, adductors, and internal and external rotators were measured at angular velocity 120°/sec by using Biodex isokinetic system. Moreover, the agonist/antagonist strength ratio for all muscle groups were calculated. Results. The normalized peak torques of RWL group were significantly greater than the control group (p < 0:05). The abductor/adductor and external rotator/internal rotator ratios of the RWL were significantly lower than the control group (p = 0:008 and 0.009, respectively). Conversely, there was no significant difference between both groups in relation to the flexor/extensor ratio (p = 0:259). Conclusion. These results suggested that the recreational weightlifting exercises place trainees at risk of muscle imbalances. Therefore, the restoration of a normal concentric abductor/adductor and external rotator/internal rotator strength ratios may decrease the risk of possible shoulder injury.
Muscle function in glenohumeral joint stability during lifting task
PloS one, 2017
Ensuring glenohumeral stability during repetitive lifting tasks is a key factor to reduce the risk of shoulder injuries. Nevertheless, the literature reveals some lack concerning the assessment of the muscles that ensure glenohumeral stability during specific lifting tasks. Therefore, the purpose of this study was to assess the stabilization function of shoulder muscles during a lifting task. Kinematics and muscle electromyograms (n = 9) were recorded from 13 healthy adults during a bi-manual lifting task performed from the hip to the shoulder level. A generic upper-limb OpenSim model was implemented to simulate glenohumeral stability and instability by performing static optimizations with and without glenohumeral stability constraints. This procedure enabled to compute the level of shoulder muscle activity and forces in the two conditions. Without the stability constraint, the simulated movement was unstable during 74%±16% of the time. The force of the supraspinatus was significant...
International Journal of Sports Physical Therapy, 2015
There is little research on how the amount of shoulder joint range of motion, specifically glenohumeral rotation, may be related to the muscle strength of the rotator cuff muscles. A long held belief is that a joint with excessive range of motion needs sufficient muscular strength for stability. However, no studies have examined this concept. The purpose of this study was to see if total arc of glenohumeral joint rotation (External rotation [ER]+Internal rotation [IR]) could predict peak isometric muscle strength of the IR or ER muscles of the shoulder. Cross-sectional study design. Fifty-three participants (41 females, 12 males) participated in the study. Passive glenohumeral joint internal rotation and external rotation motion was measured for each participant with a standard goniometer. Isometric muscle force of the ER and IR muscles were tested using a handheld dynamometer in three positions: end range ER, neutral 0°, and end range IR. Data were analyzed using a non-parametric t...
Journal of Strength and Conditioning Research, 2008
Imbalance of the eccentrically-activated external rotator cuff muscles versus the concentrically-activated internal rotator cuff muscles is a primary risk factor for glenohumeral joint injuries in overhead activity athletes. Nonisokinetic dynamometer based strength training studies, however, have focused exclusively on resulting concentric instead of applicable eccentric strength gains of the external rotator cuff muscles. Furthermore, previous strength training studies did not result in a reduction in glenoumeral joint muscle imbalance, thereby suggesting that currently used shoulder strength training programs do not effectively reduce the risk of shoulder injury to the overhead activity athlete. Two collegiate women tennis teams, consisting of 12 women, participated in this study throughout their preseason training. One team (n = 6) participated in a 5-week, 4 times a week, external shoulder rotator muscle strength training program next to their preseason tennis training. The other team (n = 6) participated in a comparable preseason tennis training program, but did not conduct any upper body strength training. Effects of this strength training program were evaluated by comparing pre-and posttraining data of 5 maximal eccentric external immediately followed by concentric internal contractions on a Kin-Com isokinetic dynamometer (Chattecx Corp., Hixson, Tennessee). Overall, the shoulder strength training program significantly increased eccentric external total work without significant effects on concentric internal total work, concentric internal mean peak force, or eccentric external mean peak force. In conclusion, by increasing the eccentric external total exercise capacity without a subsequent increase in the concentric internal total exercise capacity, this strength training program potentially decreases shoulder rotator muscle imbalances and the risk for shoulder injuries to overhead activity athletes.
Medicina dello sport; rivista di fisiopatologia dello sport
Aim. The objective of the present study was to compare the range of motion (ROM) of shoulder joint in movements (inward and outward rotation, abduction and extension) in active and former weightlifters, and ordinary people (nonweightlifters). Methods. For this purpose, 61 men aged 19-29 years from Golestan and Markazi provinces were selected using cluster random sampling and categorized in three groups, that is, active weightlifters (N.=23), former weightlifters (N.=18) and non-weightlifters (N.=20) who, then, participated in a causal-comparative study. Measurements were conducted using Universal goniometer as suggested in Norkin and White’s method (1995). Data analysis was carried out using paired t-test, ANOVA and LSD. Results. ROM of shoulder joint in active and former weightlifters was significantly less than in non-weightlifters (P<0.05). There were no significant differences between ROM of shoulder joint in active and former weightlifters (P<0.05). Conclusion. It could b...
EMG and strength correlates of selected shoulder muscles during rotations of the glenohumeral joint
Clinical Biomechanics, 2000
Objective. To identify activation patterns of several muscles acting on the shoulder joint during isokinetic internal and external rotation. Design. Combined EMG and isokinetic strength analysis in healthy subjects. Background. EMG studies of the shoulder region revealed intricate muscular activation patterns during elevation of the arm but no parallel studies regarding pure rotations of the joint could be located. Methods. Fifteen (n 30 shoulders) young, asymptomatic male subjects participated in the study. Strength production during isokinetic concentric and eccentric internal and external rotations at 60 and 180°/s was correlated with the EMG activity of the rotator cu, biceps, deltoid and pectoralis major. Analysis of the smoothed EMG related to the timing of onset of the signal and to the normalized activity at the angle of the peak moment. Determination of the association between the EMG and the moment was based on strength ratios. Results. Findings indicated that for both types of rotations, the rotator cu and biceps were active 0.092 0.038±0.215 0.045 s prior to the initiation of the actual movement and 0.112±0.034 s prior to onset of deltoid and pectoralis major activity. These dierences were signi®cant in all of the eight conditions (P < 0.05). In terms of the strength ratios, strong association was found between electrical activity and moment production in the subscapularis and infraspinatus (r 2 0.95 and 0.72, respectively) at the low and high angular velocities. Conclusions. Prior to actual rotation of the shoulder joint, normal recruitment of the rotator cu and biceps is characterized by a non-speci®c presetting phase which is mainly directed at enhancing the joint`stiness' and hence its stability. Once movement is in progress, the EMG patterns of these muscles become movement speci®c and are correlated with the resultant moment. Relevance Muscular dysfunction relating to delayed onset activity or altered activation patterns, due to pain, perturbed mechanics or disturbed neural activation have been implicated as concomitant factors in other joint associated pathologies. Through highlighting the role of the rotator cu in shoulder joint rotations, this study lends further support to the argument that a parallel situation may prevail with respect to shoulder joint dysfunction. This could lead to the development of rehabilitation protocols aimed speci®cally at redressing such dysfunction.