The purpose of this study was to determine the effect of the moment arm length on the muscle activation of the upper limbs and the trunk. Subjects performed push-up exercises on a stable surface and on an unstable surface placing their feet at a higher level than the hands. [Subjects] The subjects of this study were 33 normal adults in their 20s who had normal range of motion and who were without disorders of the shoulder complex, musculoskeletal disease in the upper limbs or low back pain. [Methods] The experiment was performed using the following four positions: on an unstable surface created by placing a 65 cm diameter exercise ball under the ankle or knee joints of the subjects, and on a stable surface created by placing a bench with a height of a 65 cm under the ankle or knee joints of the subjects. To prevent the effect of muscle fatigue, all exercises were randomly performed. To measure muscle activation in the trunk, electrodes were attached to the erector spinae, rectus abdominis, and external oblique abdominal muscle. The serratus anterior, deltoid middle fiber, pectoralis major, and triceps brachii muscle were chosen as scapular stabilizers.[Results] The muscle activations of the four different positions were compared and the results show that there were significant difference among the erector spinae, rectus abdominis, external oblique abdominal, serratus anterior, deltoid middle fiber and pectoralis major. [Conclusion] The push-up exercise with the lower limbs on unstable ground increased trunk and shoulder muscle activation more than those on stable ground. We assume that muscle activation of the distal parts might have affected the muscle activation of the shoulder stabilizers that are proximal part muscles.

Abstract.[Purpose] The purpose of this study was to evaluate the effects of push-up plus exercise with visual biofeedback on the activity of the shoulder stabilizer muscles in individuals with winged scapula.[Subjects] This study was conducted with two groups: a visual biofeedback push-up plus exercise group (n=6) and a control push-up plus exercise group (n=6).[Methods] Muscular activity of the shoulder stabilizer muscles of both groups were measured by electromyogram (EMG), both before and after the exercise.[Results] The control group showed a significant difference pre-and post-exercise in the activity of the serratus anterior muscle during elbow extension, but differences in other muscles were insignificant. The visual feedback group showed significant differences pre-and post-exercise in activity of the upper and lower trapezius during elbow extension, in the serratus anterior muscle during elbow flexion and extension and scapula protraction, and in the pectoralis major muscle during elbow flexion.[Conclusion] Providing visual biofeedback during push-up plus exercise made the exercise more effective for winged scapula.

[Purpose] The present study aimed to determine the changes in the muscle activities of the gluteus medius, latissimus dorsi, and gluteus maximus at different gait speeds, to collect basic data for the study of the gluteus medius. [Subjects and Methods] The subjects were 18 young and healthy male adults whose mean age, height, and weight were 26.4 years, 173.37 cm, and 72.5 kg, respectively. Electromyograpy was used to measure the maximum voluntary isometric contraction of each muscle three times and the values averaged. Then, the subjects walked on a treadmill at gait speeds of 1.5 m/s, 2.5 m/s, and 3.5 m/s and the muscle activity of each muscle was measured. [Results] The gluteus medius showed no significant difference in muscle activity among the different gait speeds. [Conclusion] For selectively strengthening the gluteus medius, to establish the external stability of the pelvis during walking, weight loading or sloped treadmills are effective interventions. However, different gait speeds exert no significant effect on the selective strengthening of the gluteus medius.

Clinicians may use these results to effectively progress strengthening for gluteus medius in the rehabilitation of lower extremity injuries.

[Purpose] The purpose of this study was to measure the muscle activities of the trunk muscles and upper limb muscles during maximum isometric contraction when temporomandibular joint alignment was achieved with a mandibular orthopedic repositioning appliance in order provide basic data on the effects of mandibular orthopedic repositioning appliance on the entire body. [Subjects] The present study was conducted with healthy Korean adults in their 20s (males=10, females=10). [Methods] An 8 channel surface electromyography system was used to measure the muscle activities of the upper limb muscles and neck muscles of the subjects during maximum isometric contraction with and without use of a mandibular orthopedic repositioning appliance. [Results] The maximum isometric contractions of the trunk and upper limb muscles when mandibular orthopedic repositioning appliance were used were compared with those when no mandibular orthopedic repositioning appliance was used. The results showed that the sternocleidomastoid muscle, cervical and lumbar erector spinae, upper trapezius, biceps, triceps, rectus abdominis and internal oblique and external oblique muscles all showed significant increases in maximum isometric contractions with a mandibular orthopedic repositioning appliance. [Conclusion] The use of a mandibular orthopedic repositioning appliance is considered to be a method for normal adults to improve the stability of the entire body with the improvement of the stability of the TMJ. The proximal improvement in stability improves of the proximal thereby improving not only muscle strength with increased muscle activation but also stability during exercises.