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.
Il-young Yu, Dong-kyu Lee, Myoung-Joo Kang and Jae-seop Oh
Jun-Seok Kim, Moon-Hwan Kim, Duk-Hyun Ahn and Jae-Seop Oh
Context: A winged scapula (WS) is associated with faulty posture caused by weakness of the serratus anterior (SA), which mainly acts as a scapular stabilizer muscle. It is important to accurately assess and train the SA muscle with a focus on scapula stabilizers during musculoskeletal rehabilitation of individuals with a WS. Objective: The authors examined muscle activity in the SA and pectoralis major (PM), upper trapezius (UT), and anterior deltoid (AD) as well as shoulder protraction strength during isometric shoulder protraction in individuals with and without a WS. Design: Cross-sectional study. Setting: A clinical biomechanics laboratory. Participants: In total, 27 males with no shoulder, neck, or upper-extremity pain participated. Main Outcome Measures: Isometric shoulder protraction strength was collected and surface electromyography used to measure the activity of the SA, PM, UT, and AD muscles and selective SA activity ratio to other shoulder muscles. Results: Electromyography activity of the SA muscle and shoulder protraction strength were significantly lower in individuals with a WS compared with the non-WS group (P < .05). In contrast, PM muscle activity and the PM-to-SA, UT-to-SA, and AD-to-SA ratios were significantly greater in individuals with a WS than in individuals without winging (P < .05). Conclusions: Isometric shoulder protraction for measuring SA strength in individuals with a WS should focus on isolated muscle activity of the SA, and SA strengthening exercises are important for individuals with a WS.
Min-Hyeok Kang, Dong-Kyu Lee, Kyung-Hee Park and Jae-Seop Oh
Ankle-dorsiflexion range of motion has often been measured in the weight-bearing condition in the clinical setting; however, little is known about the relationship between the weight-bearing-lunge test (WBLT) and both ankle kinematics and performance on dynamic postural-control tests.
To examine whether ankle kinematics and performance on the Lower Quarter Y-Balance Test (YBT-LQ) are correlated with results of the WBLT using an inclinometer and tape measure.
University motionanalysis laboratory.
30 physically active participants.
Main Outcome Measures:
The WBLT was evaluated using an inclinometer and a tape measure. The reach distances in the anterior, posteromedial, and posterolateral directions on the YBT-LQ were normalized by limb length. Ankle dorsiflexion during the YBT-LQ was recorded using a 3-dimensional motion-analysis system. Simple linear regression was used to examine the relationship between the WBLT results and both ankle dorsiflexion and the normalized reach distance in each direction on the YBT-LQ.
The WBLT results were significantly correlated with ankle dorsiflexion in all directions on the YBT-LQ (P < .05). A strong correlation was found between the inclinometer measurement of the WBLT and ankle dorsiflexion (r = .74, r 2 = .55), whereas the tape-measure results on the WBLT were moderately correlated with ankle dorsiflexion (r = .64, r 2 = .40) during the anterior reach on the YBT-LQ. Only the normalized anterior reach distance was significantly correlated with the results for the inclinometer (r = .68, r 2 = .46) and the tape measure (r = .64, r 2 = .41) on the WBLT.
Inclinometer measurements on the WBLT can be an appropriate tool for predicting the amount of ankle dorsiflexion during the YBT-LQ. Furthermore, WBLT should be measured in those who demonstrate poor dynamic balance.