Background: The hamstring muscles in the lower extremity are highly important for knee joint stability and can be classified into medial and lateral hamstrings according to the anatomical position, which have some different functions. To measure the strength of the individual hamstring muscles, manual muscle testing is clinically performed by dividing rotation postures into internal and external postures. However, this has no sufficient scientific background. Objects: This study aimed to test the difference that the tibial rotation would cause in the muscle activity of the medial and lateral hamstrings. Methods: The muscle activities of the biceps femoris, semitendinosus, and semimembranosus were measured in a total of three different postures (neutral position and internal and external rotations) with 3 replications. During the maximal isometric contraction, resistance was constantly provided by the string attached to the strap, not by manual resistance of the examiner. Before and after electromyography measurements, the participants underwent hamstring flexibility measurement using the active knee extension test in the supine position on the treatment table Results: The semitendinosus had a 12.56% reduction in muscle activity in external rotation as compared with that in neutral position. The biceps femoris and semimembranosus showed reduced muscle activities in both external and internal rotations as compared with those in neutral position. Only the women showed significant decreases in the comparison between pre and post-active knee extension. Conclusion: Only the semitendinosus muscle was consistent with the anatomical speculation. However, the reduction in the muscle activity of the semitendinosus as compared with that in neutral position was only 12.56%, the clinical value of which may be difficult to justify.

Background: Muscle weakness and impaired trunk muscle control are common in stroke patients. The bridging exercise (BE) is generally used for trunk stabilization and improving the overall function of stroke patients. The effectiveness of the BE with hip adductor contraction (BEHA) in facilitating trunk muscle activation has been well studied in healthy adults. However, the impact of BEHA in sub-acute stroke patients has not yet been investigated. Objects: The purpose of this study was to determine the effects of BEHA on the electromyography (EMG) activities and the asymmetry of the rectus abdominis (RA), external oblique (EO) and internal oblique (IO) abdominal muscles. Methods: Twenty participants with sub-acute stroke (11 males and 9 females) were recruited. Each participant was asked to perform bridging exercises for five seconds under three different conditions: BE in a neutral position (BEN), BEHA with a large ball (BEHAL) and BEHA with a small ball (BEHAS). The EMG amplitudes of the bilateral RA, EO and IO and the asymmetry of the EMG activity between the sound and affected sides were compared among the conditions. The significance level was set at α=.05. Results: The EMG activities of RA, EO and IO were significantly greater during BEHAL and BEHAS than during BEN (p<.05); the asymmetry of the RA, EO and IO decreased significantly during BEHAL and BEHAS compared to BEN (p<.05). However, no measured variables showed any significant differences between BEHAL and BEHAS (p>.05). Conclusion: This study compared the EMG activities of the RA, EO and IO on both sides and the asymmetry of the RA, EO and IO during BEN, BEHAL and BEHAS. Our findings suggest that BEHA was more effective for individuals with hemiplegic stroke at facilitating and normalizing abdominal muscle control than BEN.

The aim of this study was to compare the electromyographic (EMG) activity levels of the scapular upward rotators [upper trapezius (UT), lower trapezius (LT), and serratus anterior (SA)] and other scapular muscles [posterior deltoid (PD), levator scapulae (LS), and infraspinatus (IS)] during isometric lower trapezius exercises. Twenty males with no medical history of shoulder pain or upper extremity disorders were recruited for this study. EMG activity was recorded from the UT, LT, SA, PD, LS, and IS while subjects performed three different exercises: Prone arm lift (PAL), Backward rocking diagonal arm lift (BRDAL), Modified Prone Cobra (MPC). One-way analysis of variance (ANOVA) was used to determine any significant differences among the three exercises. A lower relative activation of UT, LT, and SA was seen with the MPC than with the other exercises (p<.05). The relatively lower activation of the UT identified, the MPC exercise as the preferred choice for preferential strengthening the LT (p<.05). However, a higher activation in the PD, LS, and IS occurred with the MPC than with the other exercises (p>.05). The recruitment pattern of synergist varied depending on the exercise posture. These findings suggest that exercise posture is an important factor in the selection of strengthening exercise for weak muscle.

목적 : 본 연구는 상위흉수손상군, 하위흉수손상군, 정상군을 대상으로 체간과 상지의 컴퓨터 사용과 관련된 여덟 가지 근육의 활성도를 측정하여 흉수손상자에게 적절한 키보드의 위치를 제시하고자 실시되었다. 연구방법 : 연구대상자는 미국 척수 손상 협회(American Spinal Injury Association; ASIA) A 또는 B의 흉수손상자 중 상위흉수손상자(T2-T8) 9명, 하위흉수손상자(T9-T12) 11명, 그리고 정상인 9명이었다. 적절한 키보드의 위치를 알아 보고자 두 가지 위치 즉, 팔꿈치 굽힘 100°위치와 팔꿈치 굽힘 70°위치에서 근활성도를 측정하였다. 모든 대상자는 2분간 메트로놈의 박자에 맞춰 키보드 중간열의 키를 1초에 4타의 속도로 타이핑하였으며 이때 표면근전도기를 이용하여 목과 어깨의 목세움근, 위등세모근, 앞어깨세모근, 뒤세모근, 중간등세모근과 손목폄근군, 그리고 척수손상자의 체간유지 보조근육인 넓은 등근과 큰가슴근의 근활성도(%RVC)를 측정하였다. 결과 : 상·하위흉수손상군의 측정치는 정상인과 동일하게 팔꿈치 굽힘 100°의 자세에 비해 팔꿈치 굽힘 70°인 위치에서 위등세모근, 손목폄근군, 앞어깨세모근의 활성도가 유의하게 낮게 나타났다. 또한 하위흉수손상군의 경우 정상인과 다르게 팔꿈치 굽힘 100°높이에서 목세움근과 넓은등근의 활성도가 유의하게 증가하였다. 결론 : 흉수손상자의 체간과 상지의 근긴장도를 감소시키기 위해 적절한 키보드 위치는 팔꿈치 굽힘 70°정도의 높이였다. 차후 연구에서는 보다 많은 척수손상자를 대상으로 장시간의 포괄적 컴퓨터 작업을 적용하여 장애특성에 적합한 VDT 환경을 파악하는 연구가 필요할 것으로 사료된다.

The purpose of this study was to investigate the trunk and lower extremity muscle activity induced by three different intensity conditions (intensity 1, 3, 5) of whole body vibration (WBV) during bridging exercise. Surface electromyography (EMG) was used to measure trunk and lower extremity muscles activity. Eleven healthy young subjects (6 males, 5 females) were recruited from university students. The collected EMG data were normalized using reference contraction (no vibration during bridging) and expressed as a percentage of reference voluntary contraction. To analyze the differences in EMG data, the repeated one-way analysis of variance was used. A Bonferroni's correction was used for multiple comparisons. The study showed that EMG activity of the rectus abdominis, external oblique, internal oblique, erector spinae and rectus femoris muscles was not significantly different among three intensity conditions of WBV during bridging exercise (p>.05). However, there were significantly increased EMG activity of the medial hamstring muscle (p=.001) and medial gastrocnemius muscle (p=.027) in the intensity 3 condition compared with the intensity 1 condition. This result can be interpreted that vibration was absorbed through the distal muscles, plantar flexor and knee flexor.

The purposes of this study were to compare core muscle activities with and without the use of Pilates resistive equipment during bridging exercises and to investigate the efficacy of a Pilates device. Fourteen healthy individuals (6 males, 8 females) between 20 to 26 years of age were examined. They were engaged in a bridging exercise with and without a magic circle. Three consecutive repetitions of each exercise were performed. Surface electromyography (sEMG) was used to measure the electrical activities of the right side internal oblique, the adductor longus, the multifidus, and the gluteus maximus muscles. Normalized EMG activities were compared using a paired t-test and the level of significance was set at =.05. The results showed that the EMG activities of the internal oblique (p=.0078), the adductor longus (p=.0007), and the gluteus maximus (p=.0001) muscles were significantly higher when using the magic circle during the Pilates bridging exercise. Also, statistically significant change existed in the multifidus muscle (p=.0106). The bridging exercise, combined with hip adduction using the magic circle, may enhance core stabilization. Therefore, using a magic circle during hip adduction combined with bridging exercise may be recommended usefully for individuals wanting to strength the core muscles. Further research is needed to access the nature of motor control of the Pilates mat exercises and to deliver exercise intervention for lower back pain patients.

This study was conducted to identify the effects of high-heel shoes on EMG activities of rectus femoris and biceps femoris in 28 healthy women. Subjects were composed of experimental group (wearing high-heel shoes) and control group (wearing low-heel shoes). Two groups participated in three conditions standing (bare foot wearing athletic shoes and 7.5 cm height shoes). In high-heel shoes condition, EMG activities of rectus femoris of control group were significantly lower than that of biceps femoris of experimental group, but EMG activities of both muscles of experimental group did not should significant difference. In bare foot standing condition, EMG activities of rectus femoris of experimental group were significantly lower than that of biceps femoris but EMG activities of both muscles of control group had no significant difference. These results showed that hamstring lengthening effects was produced when wearing high-heel shoes because the external knee extension moment was increased. In the short term, high-heel shoes effect on the increase of the biceps femoris activities by spindle reflex, but in the long term, the normal amplitude of the same muscle activities by Golgi tendon organ reflex.