Background: Shoulder external rotation exercises are commonly used to improve the stabilizing ability of the infraspinatus. However, during exercise, excessive activation of the posterior deltoid compared to the infraspinatus causes the humeral head to move anteriorly in an abnormal position. Many researchers have emphasized selective activation of the infraspinatus during shoulder external rotation exercise. Objects: This study aims to delineate the optimal exercise method for selective activation of infraspinatus by investigating the muscle activities of the infraspinatus and posterior deltoid according to the four shoulder exercise methods and two forearm positions. Methods: Thirty healthy individuals participated in this study. The participants were instructed to perform shoulder external rotation exercises following four exercise methods: sitting external rotation (SIER); standing external rotation at 90° abduction (STER); prone external rotation at 90° abduction (PRER); side-lying external rotation (SLER), and two forearm positions (neutral, supinated). The electromyography (EMG) signal amplitude was measured during each exercise. Surface EMG signals were recorded from the posterior deltoid, infraspinatus, and biceps brachii. Results: EMG results of the infraspinatus and posterior deltoid in PRER, were significantly higher than that of the other exercises (p < 0.01). The EMG ratio (infraspinatus/posterior deltoid) in SIER was significantly higher than that of the other exercises. EMG activation of the posterior deltoid in SIER, PRER, and SLER was significantly higher in neutral than in supinated (p < 0.01). Furthermore, the EMG of the infraspinatus in SIER was significantly higher in neutral than in supinated (p < 0.01). The EMG ratio (infraspinatus/ posterior deltoid) in SIER was significantly higher in neutral than in supinated (p < 0.05.) Contrarily EMG ratios in PRER and SLER were significantly higher in supinated than in neutral (p < 0.05). Conclusion: The results show that clinicians should consider these exercise methods and forearm positions when planning shoulder external rotation exercises for optimal shoulder rehabilitation.

Background: Round shoulder posture, results from excessive flexed posture of the thorax, is defined as a position of scapular protraction, anterior tipping, and downward rotation. However, previous studies have focused on only passive position of the thorax during scapular posterior tilting (SPT) and have not reported on SPT combined with correction of flexed posture. Objects: The aim of this study was to compare effects of SPT and SPT with prone trunk extension (SPT + PTE) on activities of the lower trapezius, serratus anterior, and thoracic erector spinae and degree of posture in subjects with round shoulder and flexed posture. Methods: Fifteen subjects with round shoulder and flexed posture were recruited. The caliper was used to measure the degree of round shoulder and flexed posture. Electromyography was performed to collect data of muscle activities. Paired t-test was used to compare two exercise (α=.05). Results: When SPT + PTE was applied, the degree of round shoulder posture (p=.001) and flexed posture (p=.039) significantly decreased compared with that when SPT was applied. The lower trapezius activity significantly increased in the SPT + PTE condition compared with that in the SPT condition (p=.026). There were no significant differences in serratus anterior activity between SPT + PTE and SPT. The thoracic erector spinae activity significantly increased in the SPT + PTE condition compared with that in the SPT condition (p=.014). Conclusion: SPT + PTE might be one of the effective methods to enhance activities of lower trapezius and thoracic erector spinae, and to reduce round shoulder posture and flexed posture in subjects with round shoulder and flexed posture.

Background: Sitting posture influences movements of scapulothoracic and glenohumeral joints and changes the shoulder muscle activities. The development and maintenance of correct sitting posture is important for the fundamental treatment of shoulder pain during rehabilitation. Objects: The purpose of this study was to investigate the effects of the sitting postures and the shoulder movements on shoulder muscle activities for both male and female. Methods: Twenty-eight subjects without shoulder-related diseases participated in this experiment. The subjects had randomly adopted three different sitting postures (upright posture, preferred posture, maximum slouched posture) and shoulder flexion angles in scapular plane (30˚, 90˚, 120˚). Surface electrodes were collected from upper trapezius (UT), anterior deltoid (AD), and posterior deltoid (PD) and the active shoulder range of motion was measured in each sitting posture and shoulder flexion angle. Results: The active range of motions of the shoulder external rotation and the flexion in the scapular plane decreased from the upright posture to the maximum slouched posture (p<.05, mixed-effect linear regression with random intercept, Tukey post-hoc analysis). All muscles showed the highest EMG activities at 120˚ shoulder flexion with the maximum slouched posture and did not show the gender differences. Conclusion: Increased shoulder muscle activities may become the potential risk factor for the shoulder impairment and pain if people continuously maintain the maximum slouched posture. Therefore, an upright position is necessary during shoulder exercises, as well as in activities of daily living, including motions involving lifting the arms.

Background: Scapular posterior tilt (SPT) is important in the prevention of abnormal scapular movement and pain during elevation of the arm. However, previous studies have overlooked increased upper trapezius (UT) muscle activity interrupting the normal force couple of scapular motion and compensation of levator scapulae (LS) muscle activated simultaneously with UT during SPT exercise. Objects: The purpose of this study was to compare the effects of modified SPT with depression exercise versus SPT exercise on serratus anterior (SA), lower trapezius (LT), UT, and LS muscle activities and the clavicular tilt angle, in subjects with rounded shoulder posture (RSP) and myofascial pain in the UT muscle region. Methods: Eighteen subjects with RSP were recruited and randomly allocated to 2 groups; 9 in the SPT group and 9 in the SPT with depression group. All subjects met the specific RSP criteria and had myofascial pain of UT region. Depending on the allocated group, subjects performed the assigned SPT exercise and EMG data were recorded during the each exercise. Clavicular tilt angle was defined as the angle between the line joining the medial and lateral end of the clavicle and a horizontal line. Results: The SA muscle activity was significantly greater in SPT with depression than with SPT exercise (p<.05). The UT, LS muscle activity and the clavicular tilt angle was significantly lower in SPT with depression than with SPT exercise (p<.05). Conclusion: These findings were insightful because the potential risk of pain from overactivation of the UT and LS was considered, in contrast with SPT exercise. SPT with depression exercise can be implemented as an effective method to facilitate scapular muscle activity for stability and to prevent myofascial pain in the neck and shoulder.

Background:Individuals with spinal cord injury (SCI) rely on their upper limbs for body-lifting activity (BLA). While studies have examined the electromyography (EMG) and kinematics of the shoulder joints during BLA, no studies have considered foot position during BLA.Objects:This study compared the effects of different foot positions during BLA on the shoulder muscle activities, peak plantar pressure, knee flexion angle, and rating perceived exertion in individuals with SCI.Methods:The study enrolled 13 mens with motor-complete paraplegic SCI, ASIA (American Spinal Injury Association) A or B. All subjects performed BLA with the feet positioned on the wheelchair footrest and on the floor independently. Surface EMG was used to collect data from the latissimus dorsi, pectoralis major, serratus anterior, and triceps brachii. The peak plantar pressure was measured using pedar-X and the knee flexion angle with Image J. Borg’s rating perceived exertion scale was used to measure the physical activity intensity level. The paired t-test was used to compare the shoulder muscle activities, peak plantar pressure, knee flexion angle, and rating perceived exertion between the two feet positions during BLA.Results:The activity of the latissimus dorsi, pectoralis major, serratus anterior, and triceps brachii and rating perceived exertion decreased significantly and the peak plantar pressure and knee flexion angle increased significantly when performing BLA with the feet positioned on the wheelchair footrest compared with on the floor (p<.05).Conclusion:These findings suggest that individuals with SCI may perform BLA with the feet positioned on the wheelchair footrest for weight-relief lifting to decrease the shoulder muscle activities and the rating perceived exertion and to increase the peak plantar pressure and the knee flexion angle.

The smart-phone has become a necessity for most people. In this study, we determined that using a smart-phone for 20 minutes can cause increased neck and shoulder muscle activities and fatigue. Seventeen healthy male smart-phone users who attended Yonsei University played a smart-phone game for 20 minutes and changes in their bilateral cervical erector spinae and upper trapezius muscle activities and fatigue were measured. To assess muscle activities and fatigue, we used the following variables: the median frequency, the 50th percentile Amplitude probability distribution function (APDF) value (median load), and the discrepancy in the 90th percentile APDF value and the 10th percentile APDF value (APDF range). A paired t-test was used to compare pre-smart-phone-use status with post-smart-phone-usestatus. The median frequency of the bilateral cervical erector spinae and the upper trapezius decreased significantly after 20 minutes of smart-phone use (p<.05). In addition, the 50th percentile APDF value of the bilateral cervical erector spinae and the right upper trapezius increased significantly (p<.05). The APDF range of the bilateral cervical erector spinae and the upper trapezius also increased significantly (p<.05). However, the 50th percentile APDF range of the left upper trapezius was not significantly different (p>.05). These findings suggest that using smart-phones for 20 minutes can induce muscle fatigue and increased neck and shoulder muscle activities.

The purpose of this study was to investigate the variations in gait parameters in terms of the type of arm sling used in hemiplegic patients. Ten patients with hemiplegia and ten healthy adults participated in this study and walked at self-selected speeds on a GAITRite-instrumented carpet. The activities of the opposite shoulder girdle muscle including the latissimus dorsi, anterior deltoid, and posterior deltoid were simultaneously recorded using surface EMG during gait. They were randomly assigned a condition: without an arm sling, a single strap arm sling, a Harris hemi arm sling, a Rolyan humeral cuff arm sling, and a Bobath roll arm sling. The following gait variables were analyzed: the temporo-spatial parameters of velocity, step length, stride length, swing phase, stance phase, single support, step time and toe in/toe out. The statistical analysis was one-way ANOVA with repeated measures to compare the variation of each variable. In comparison of parameters in each trial in the hemiplegia group, the non-affected side stride length, single support, and toe in/toe out resulted in statistically significantly changes (p<.05). But without an arm sling group did not show any gait parameter differences with arm slings. This study found that several arm slings varied gait patterns in patients with hemiplegia and in healthy adults. In the EMG analysis, the Rolyan humeral cuff arm sling and the Bobath roll arm sling were higher muscle activity for the latissimus dorsi muscle than did the single strap ann sling. Further study should examine the problems that appeared in patients who worn arm slings by focusing on a larger number of subjects and by studying the variety of responses in more detail using an assessment tool that measures variation.

This study was carried out to compare the muscle activities of the shoulder stabilizers between persons with and without winging scapular during push-up plus exercise (adds the scapular protraction to the general push-up exercise). For this study, eleven males with winging scapular and eleven healthy males were recruited. Surface electromyographic (EMG) activity was recorded from the serratus anterior, upper trapezius, lower trapezius, infraspinatus, and pectoralis major while the subjects performed the push-up plus. Each push-up plus was subdivided into three phases according to the elbow position which was measured using the 3-D motion analysis system: elbow flexion (EF), elbow extension (EE), and shoulder protraction phases (SP). Two-way repeated measure ANOVA (phase group) were used for statistical analysis. There was significant phase by group interaction only on the EMG composition ratio of the serratus anterior (p>.05). The EMG composition ratio of the serratus anterior was significantly higher in SP than in either EF or EE however, it was not different between winging scapular and normal groups. For both groups, the EMG composition ratio of upper trapezius, lower trapezius, and pectoralis major was significantly different across the phases of push-up plus, but the infraspinatus EMG composition ratio was not. For both groups, in EF and EE phases, the EMG composition ratio of both pectoralis major and serratus anterior were relatively higher than that of other muscles. However, in both groups, the EMG composition ratio of the serratus anterior became much more predominant than that of the pectoralis major. In addition, infraspinatus activated greater than pectoralis major. These results showed that the push-up plus exercise is effective to selectively strengthen the serratus anterior for both individuals with and without winging scapular, but not equally effective for other shoulder stabilizers.