The effects of biofeedback training for efficient activation of infraspinatus on proprioception and EMG activity during shoulder external rotation.

The purpose of this study investigated which biofeedback (BF) training enables efficient activation of the infraspinatus muscle that affect joint position sense (JPS) and force sense (FS) of the shoulder joint. Twenty healthy males participated and performed three external rotation (ER) exercises under three randomly assigned training conditions: 1) non-biofeedback (NBF), 2) BF and 3) force biofeedback (FBF). Each exercise was performed at intervals of one week between training conditions. After performed the ER exercise under each training condition, the relative error (RE) was calculated at shoulder ER 45° and 80°, and then shoulder ER force were measured to determine the JPS error and FS error, respectively. Muscle activity of infraspinatus and posterior deltoid were measured and compared between training conditions. The RE of shoulder ER 45° and 80° were significantly lower under the FBF conditions than other training conditions (P < 0.05). The RE of shoulder ER force were also significantly lower under the FBF conditions compared to those under the other training conditions (P < 0.05). The activity of the infraspinatus muscle was significantly higher under the FBF conditions during all three ER exercises than other training conditions (p < 0.05). We suggest that BF trainings can be useful to improve the proprioception of shoulder joint as well as activation of infraspinatus muscle while performing the ER exercises.

Influence of scapular motion cues on trapezius muscle activity during Y exercise.

BACKGROUND: The Y exercise is a therapeutic exercise facilitating lower trapezius muscle activity. OBJECTIVE: To identify the effects of scapular movement cues (posterior tilt vs. posterior tilt with adduction/depression) on trapezius muscle activity during Y exercise. METHODS: Fifteen healthy men without current shoulder pain performed general Y exercise; Y exercise with cues for scapular posterior tilt; and Y exercise with cues for scapular posterior tilt, adduction, and depression. Electromyography (EMG) data for the trapezius muscles were collected during Y exercise. The posterior tilt angle of the scapula was measured in the prone position with and without cues for scapular posterior tilt using an inclinometer application. RESULTS: The greatest lower trapezius muscle activity was observed during Y exercise with cues for scapular posterior tilt, while the greatest EMG activity of the upper trapezius was observed during Y exercise with cues for scapular posterior tilt, adduction, and depression (p< 0.05). Middle trapezius muscle activity did not significantly differ among the three Y exercise conditions (p= 0.175). Cues for scapular posterior tilt significantly increased the scapular posterior tilt angle in the prone shoulder abduction position (p= 0.007). CONCLUSION: Cues for scapular posterior tilt were most effective in facilitating lower trapezius muscle activity during Y exercise.

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.

Strategies for controlling axial shoulder rotation change shoulder muscle activity during external rotation exercises.

BACKGROUND: The infraspinatus muscle has a crucial role in shoulder stability. Although axial shoulder rotation is useful for selective activation of the infraspinatus, no study has examined the influence of exercise position on axial shoulder rotation during shoulder external rotation (ER) exercises. Thus, this study investigated the muscle activity in the infraspinatus, posterior deltoid, and middle trapezius during shoulder ER exercises performed with and without controlled axial shoulder rotation in 2 different positions. METHODS: Twenty healthy subjects performed prone external rotation (PER) exercises with and without pressure biofeedback and seated external rotation (SITER) exercises with and without posterior humeral head gliding. Muscle activity during each ER exercise was measured using surface electromyography. RESULTS: Exercise strategy (P < .001) and position (P < .001) had a significant main effect on muscle activity in the infraspinatus and posterior deltoid. However, no significant interaction between strategy and position was observed. For muscle activity in the middle trapezius, strategy and position had a significant interaction effect (P = .014). Muscle activity in the infraspinatus increased significantly with the use of strategies to control axial shoulder rotation, whereas muscle activity in the posterior deltoid and middle trapezius decreased significantly. For all 3 muscles, greater activity was observed in the prone position than the seated position. CONCLUSION: We suggest that PER with pressure biofeedback can be useful to improve selective activation of the infraspinatus muscle while further eliciting infraspinatus muscle activity.

Appropriate Resistance Intensity and Effective Exercise for Activation of Infraspinatus.

We investigated the muscle activities of the infraspinatus and posterior deltoid, as well as the ratio of the infraspinatus to posterior deltoid muscle activities, in response to 3 resistance intensities during prone external rotation (PER) and sitting external rotation (SITER) exercises. Fifteen healthy males participated; the subjects performed two exercises randomly at three resistance intensity levels: 1) low intensity (10-20%); 2) medium intensity (45-55%); 3) high intensity (60-70%). Surface electromyography was used to measure the activities of the infraspinatus and posterior deltoid muscles. The activities of the infraspinatus and posterior deltoid increased significantly as the resistance intensity increased during both PER and SITER exercises (p<0.001). The infraspinatus-to-posterior deltoid activity ratio increased as the resistance intensity decreased. Whereas the muscle activity ratio was highest under low and medium intensity during PER and SITER, respectively, and the muscle activity ratio was significantly increased at medium intensity compared with high intensity during both PER (p=0.023) and SITER (p=0.001). Our results suggest that low to medium intensity is the appropriate resistance intensity for selective activation of the infraspinatus. In addition, our results suggest that PER and SITER are effective for strengthening the infraspinatus.

Effects of real-time visual biofeedback of pelvic movement on electromyographic activity of hip muscles and lateral pelvic tilt during unilateral weight-bearing and side-lying hip abduction exercises.

Although neutral pelvic alignment is important for hip abduction exercises, studies exploring objectively monitored pelvic alignment on the gluteus medius (Gmed) muscle activity during hip abduction exercises, especially under weight-bearing (WB) conditions, are limited. Therefore, we examined the effects of real-time visual biofeedback (RVBF) of pelvic movement on electromyographic (EMG) activity of hip muscles and lateral pelvic tilt during unilateral WB and side-lying hip abductions. Fifteen male participants performed unilateral WB and side-lying hip abduction exercises with and without RVBF. Under the RVBF condition, participants monitored pelvic movements in real time during hip abduction exercises. EMG activity of Gmed and quadratus lumborum (QL) as well as lateral pelvic tilt angle were recorded during each hip abduction exercise. Gmed EMG activity increased, while lateral pelvic tilt decreased during both hip abduction exercises with RVBF (p < 0.05). Additionally, the changes in Gmed activity, the Gmed/QL activity ratio, and the lateral pelvic tilt angle under RVBF were greater during unilateral WB hip abduction than during side-lying hip abduction (p < 0.05). These results suggest that RVBF of pelvic movement could be useful to strengthen Gmed and prevent compensatory lateral pelvic movement during hip abduction exercises, especially in the unilateral WB position.

Effects of 3 Infraspinatus Muscle Strengthening Exercises on Isokinetic Peak Torque and Muscle Activity.

CONTEXT: The infraspinatus muscle plays a particularly important role in producing primary external rotation (ER) torque and dynamic stability of the shoulder joint. Previous studies have reported that prone external rotation with horizontal abduction (PER), side-lying wiper exercise (SWE), and standing external rotation (STER) were effective exercises for strengthening the infraspinatus. However, we do not have enough knowledge about changes in muscle strength and dynamic muscle activity in each exercise under dynamic conditions. OBJECTIVE: To compare the ER muscle strength, muscle activity among exercise methods and between muscle contraction types during 3 different exercises. DESIGN: Repeated measures design in which ER muscle strength and muscle activities data were collected from subjects under 3 exercise conditions. SETTING: Outpatient clinic. PARTICIPANTS: A total of 15 healthy men with no shoulder, neck, or upper-extremity pain were participated. INTERVENTION: The subjects performed 3 different exercises randomly in concentric and eccentric using a Biodex dynamometer at an angular velocity of 60°/s. MAIN OUTCOME MEASURES: The ER peak torque (PT) data was collected and surface electromyography was used to measure the activity of the infraspinatus and posterior deltoid muscles and infraspinatus to posterior deltoid muscle activity ratio. RESULTS: There was significant main effect for muscle contraction type in ER PT (P < .05). The concentric PT was greater during PER (P < .05) and SWE (P < .05) compared with eccentric. The main effect for exercise was found in ER PT and muscle activity (P < .05). The ER PT and infraspinatus muscle activity were the largest increased during PER whereas the lowest during STER in both concentric and eccentric (P < .05). CONCLUSION: The results of this study suggest that PER is an exercise for strengthening the infraspinatus muscle effectively.

The effects of pressure biofeedback training on infraspinatus muscle activity and muscle thickness.

The aim of this study was to investigate muscle activity in the infraspinatus and posterior deltoid and infraspinatus muscle thickness during a prone external rotation (PER) exercise using pressure biofeedback. Fifteen healthy men participated in this study, performing PER exercise with pressure biofeedback under four conditions (comfortable, 2 mm Hg, 4 mm Hg, and 8 mm Hg). Surface electromyography (EMG) was used to monitor infraspinatus and posterior deltoid muscle activity, and ultrasonography was used to collect infraspinatus muscle thickness data. Infraspinatus activity and muscle thickness were greatest at 2 mm Hg pressure feedback, and both measures were significantly different from those under other pressure feedback conditions (p < 0.05). In contrast, posterior deltoid activity was lower at 2 mm Hg. However, there was no significant difference between any of the four pressure feedback conditions. These findings suggest that PER exercise with pressure biofeedback, particularly at 2 mm Hg, is effective in selectively activating the infraspinatus muscle.

Immediate effects of an end-range mobilization technique on shoulder range of motion and skin temperature in individuals with posterior shoulder tightness.

[Purpose] This study investigated the effects of an end-range mobilization technique on the range of motion of the glenohumeral internal rotation and the skin temperature of the shoulder in individuals with posterior shoulder tightness. [Subjects] Thirteen subjects with posterior shoulder tightness who had glenohumeral internal rotation deficit ≥ 15° participated. [Methods] All subjects underwent glenohumeral joint end-range mobilization intervention. The internal rotation range of motion of the glenohumeral joint was measured by a goniometer and the shoulder skin temperature was measured by a digital infrared thermographic imaging device before and immediately after the intervention. Paired t-tests were used to analyze the differences in these parameter pre and post-intervention. [Results] The glenohumeral internal rotation range of motion and skin temperature of the posterolateral shoulder in increased significantly post-intervention. [Conclusion] The end-range mobilization technique is effective for increasing the glenohumeral internal rotation range of motion and skin temperature of the shoulder in individuals with posterior shoulder tightness.

Effects of lifting the non-paretic foot on muscle activity during the semi-squat exercise in hemiplegic patients.

[Purpose] This study compared the electromyographic activity of the quadriceps in hemiplegic patients during the downward, maintenance, and upward phases of squat exercises performed with the feet parallel and with the non-paretic foot lifted. [Subjects] A total of 17 hemiplegic patients (9 males and 8 females) volunteered for this study. [Methods] All subjects performed squat exercises with the knees flexed to 30° and with the feet parallel (shoulder-width apart) or with lifting of the non-paretic foot (normalized to 25% of the knee height). [Results] The activity of the rectus femoris, vastus medialis oblique, and vastus lateralis muscles was significantly higher during squat exercises performed with the non-paretic foot lifted than with the feet parallel to each other. The activity of all muscles during the maintenance phase of the exercises was greater than that during the downward and upward phases. [Conclusion] Lifting the non-paretic foot during squats may represent an effective exercise for motor function rehabilitation in hemiplegic patients.

Reliability of ankle dorsiflexion passive range of motion measurements obtained using a hand-held goniometer and Biodex dynamometer in stroke patients.

[Purpose] This study investigated the reliability of ankle dorsiflexion passive range of motion (DF-PROM) measurements obtained using a goniometer and Biodex dynamometer in stroke patients. [Subjects] Fifteen stroke patients participated in this study. [Methods] Ankle DF-PROM was assessed using a goniometer and Biodex dynamometer. Ankle DF-PROM was measured during two sessions with 7 days between tests. Intraclass correlation coefficient, standard error of measurement, and minimal detectable change values were used to assess the reliability of measurements obtained using both instruments. [Results] The intra-rater reliability for ankle DF-PROM using the goniometer was moderate and good for the two raters, while using the Biodex dynamometer, it was good for both raters. Inter-rater reliability using the goniometer was moderate; using the Biodex, it was good. [Conclusion] Both intra- and inter-reliability measurements of ankle DF-PROM were higher using a Biodex dynamometer than with a goniometer.