[Purpose] Scapular stabilizer strengthening exercise is crucial for shoulder rehabilitation. The purpose of this study was to compare two types of push-up plus exercises, on a stable and unstable bases of support, using surface electromyography (EMG), to suggest an effective shoulder rehabilitation program. [Subjects and Methods] Ten healthy men volunteered for this study. All volunteers performed two sets of push-up plus exercise (standard push up and knee push up) on stable and unstable bases of support. The muscle activities of five important scapular stabilizer muscles (upper trapezius, middle trapezius, lower trapezius, serratus anterior, latissimus dorsi) were recorded during the exercise. [Results] The upper trapezius showed greater mean electric activation amplitude in the scapular retraction posture than in the scapular protraction posture, and the serratus anterior showed greater mean electric activation amplitude in the scapular protraction posture than in the scapular retraction posture. The root-mean-square normalized EMG values of the muscles were greater during the exercise performed on the unstable support than those on the stable support. [Conclusion] The standard push-up plus exercise on an unstable base of support helps to increase muscle activity, especially those of the upper/middle trapezius and serratus anterior.

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[Purpose] This study attempted to identify how genu varum or valgum affects the electromyographic activities of the vastus medialis, vastus lateralis, and rectus femoris during knee isometric contraction. [Subjects] Fifty-two healthy young adults were enrolled in this study. They were enrolled and classified into three groups by knee alignment conditions: the genu varum, genu valgum, and control groups. [Methods] The electromyographic activity ratio of the vastus medialis to the vastus lateralis and rectus femoris were calculated using the percentage of maximum voluntary contraction. The participants contracted their quadriceps during isometric contraction at 30 and 60° of knee flexion. [Results] The genu varum group had more activity in the vastus medialis than in the vastus lateralis and rectus femoris, whereas the genu valgum group had more activity in the vastus lateralis and rectus femoris than in the vastus medialis. There was a significant difference in the muscle activity ratio between the vastus medialis and vastus lateralis by angle of knee flexion degree only in the genu valgum. There were no significant differences in any of the three groups in terms of the muscle activity ratio of the vastus medialis to the rectus femoris by angle of knee flexion. [Conclusion] The quadriceps femoris was used for different strategies according to knee alignment during isometric contraction at 30 and 60°. This study suggests that rehabilitation training programs used to strengthen the quadriceps should consider the knee alignment conditions of the target subjects.

Purpose:The purpose of the present study was to examine joint position senses and muscle activity in subjects with and without chronic low back pain and to determine the effects of different types of bridge exercises on their trunk muscle activity. Methods: Thrity -eight subjects with chronic low back pain and thrity healthy controls participated in the experiment. Joint position senses and trunk muscle activity levels were measured during the different bridge exercise methods. Results:The joint position senses of the healthy group and chronic low back pain group showed significant differences during lumbar flexion, lumbar extension, lumbar lateral flexion, and lumbar rotation. The muscle activity levels of the transversus abdominis (TrA), internal oblique (IO), and external oblique (EO) were highest in the prone bridge exercise (PBE) group, followed by the supine bridge swiss ball exercise (SBSE) group and supine bridge exercise (SBE) group in order of precedence. The muscle activity level of the erector spinae (ES) was highest in the SBSE group, followed by the SBE and PBE groups in order of precedence. Conclusion: Overall, the results suggest that chronic low back pain is associated with declines in joint position senses and that PBEs increase trunk muscle activity more than conventional bridge exercises.

[Purpose] The purposes of this study were to strengthen gluteus maximus and trunk muscles depending upon the hip joint direction by bridging exercise on an unstable and stable surface, and to suggest an intervention method for efficient and selective exercise. [Participants and Methods] The test measured the muscle activities with the external rotation and internal rotation of 25 degrees and hip joint neutral position of 0 degree on a stable and unstable surface each exercise 3 times for 9 seconds. [Results] External oblique abdominis showed a higher muscle activity on the unstable surface and internal rotation. Erector spinae showed no significant difference on the surfaces and demonstrated the highest muscle activity at the internal rotation. Gluteus maximus showed a higher muscle activity on the stable surface and external rotation and the interaction effect between the surface and the angle indicated a statistical significance as well. [Conclusion] Muscle activities appear different depending upon the change of surface and joint angle, and it can be said that the correct mobilization of muscle fiber relying on the muscle arrangement direction and muscle contraction direction is the most important factor for gluteus maximus.