Background: Excessive hamstring (HS) activation due to the weakness of the gluteus maximus (GM) causes pain in the hip joint. A single-leg deadlift is a hip extensor exercise, especially GM, that includes functional movements in daily life and complex multi-joint training. In single-leg deadlift, the muscle activity depends on the forward trunk lean angle, and it's necessary to study which muscles are used dominantly depending on the angle. Objects: The purpose of this study was to compare the effect on the muscle activity of the GM and HS during single-leg deadlift according to different forward trunk lean angles and the ratio of the GM vs HS (GM/HS). Methods: Twenty-one healthy female participants were recruited. The muscles activities of the GM, HS and the GM/HS ratio were measured through electromyography during single-leg deadlift according to three condition of forward trunk lean angles (30°, 60°, and 90°). Results: The GM and HS activities significantly differed among three conditions (p < 0.05). GM/HS ratio was significantly higher at 30°and 60° of forward trunk lean compared to 90°. Moreover, the GM activity was significantly higher at 60°of forward trunk lean than at 30° (p < 0.05). Conclusion: The single-leg deadlift at 60°of forward trunk lean is a proper GM muscle strengthening exercise.

Background: The hip muscle plays various roles. Several types of functional performance tests are used for the assessment of patients with various lower extremity injuries. Hip muscle functions are important to test the performance of maintaining the spine, pelvic, and leg during bridging exercise. We designed a novel functional performance test tool, which we named close kinetic chain dynamic lower extremity stability (CKCLE) test to assess hip muscle functions. Objects: The purpose of this study was to determine the relationship between CKCLE test and hip extensor, external rotator, and abductor strengths. Methods: Twenty-two subjects were recruited in the present study (13 males and 9 females). The hip extensor, external rotator, and abductor muscle strengths were measured using a Smart KEMA strength sensor. When the examiner said “Go”, the subject performed the CKCLE test by moving one leg from the floor and touching the opposite knee and then return to the floor while maintaining the bridging position. The subjects attempted as many “touches” as possible in the allotted time (20 seconds) during the maximal tests. The correlation between the hip muscle (extensor, external rotator, and abductor) strength of the supporting leg and the number of CKCLE tests performed in 20 seconds was determined using the Pearson correlation. Results: Hip extensor (r = 0.626, p < 0.05), hip external rotator (r = 0.616, p < 0.05), and hip abductor muscle strengths (r = 0.475, p < 0.05) positively correlated with the number of CKCLE tests performed. Conclusion: We designed a CKCLE test and found that performance in the test correlated with hip extensor, external rotator, and abductor muscle strengths. The result suggests that the CKCLE test can be applied as a performance test to assess the functions of the hip extensor, external rotator, and hip abductor muscles.

Background: The bridge exercise targets the gluteus maximus (Gmax) and gluteus medius (Gmed). However, there is also a risk of dominant hamstring (HAM) and erector spinae (ES) muscles. Objects: To analyze the muscle activity the of Gmax, Gmed, HAM and ES during the bridge exercise with and without hip external rotation in different degrees of knee flexion. Methods: Twenty-three subjects were participated. The electormyography (EMG) activity of the Gmax, Gmed, HAM and ES muscles was recorded during the exercise. The subjects performed the bridge exercise under four different conditions: (a) with 90˚ knee flexion, without hip external rotation (b) with 90˚ knee flexion, with hip external rotation (c) with 135˚ knee flexion, without hip external rotation (d) with 135˚ knee flexion, with hip external rotation. Results: There was no significant interaction effect between the degree of knee flexion and hip external rotation. There was a significant main effect for degree of knee flexion in Gmax, HAM muscles activity. Gmax muscle activity was significantly greater in the 135˚ knee flexion position than in the 90˚ knee flexion position (p<.001). While HAM muscle activity was significantly less in 135˚ knee flexion position than in the 90˚ knee flexion position (p<.001). ES muscle activity was significantly less in the 135˚ knee flexion position than in the 90˚ knee flexion position (p=.002). The activity of both the Gmax and Gmed muscles was significantly greater with hip external rotation (p<.001 and p=.005, respectively). Conclusion: For patients performing the bridge exercise, positioning the knee in 135° of flexion with hip external rotation is effective for improving Gmax and Gmed muscle activity while decreasing HAM, and ES muscle activity.

Background: Improvement of the lumbo-pelvic stability can reduce the compensatory action of the erector spinae (ES) during prone hip extension (PHE). Furthermore, the application of abdominal drawing-in (ADI) maneuver increases the action of gluteus maximus (GM) and decreases the action of ES during PHE by improving the lumbo-pelvic stability. However, the post-ADI exercise effects on PHE, not the real-time application of ADI maneuver, has not been studied. Objects: This study is aimed at investigating the post-ADI exercise effects on the muscle activities of GM and ES during PHE. Methods: A total of 24 female adults participated in the study, and they were divided into two groups: Those with normal abdominal muscles (n1=12) and those with weak abdominal muscles (WA) (n2=12). Before the intervention, the subjects’ GM and ES muscle activities during PHE were measured. Subsequently, the two groups were asked to perform the ADI exercise for 10 minutes. After the ADI exercise, the GM and ES activities were equally measured during PHE. Results: The comparison result of the ES muscle activities before intervention shows a significant difference between the two groups (p<.05); the WA group showed higher muscle activities than the normal group. For the within-group comparison, the muscle activities of the ES in the WA group significantly decreased after the ADI exercise (p<.05). For the GM muscle activity, no significant difference was observed in all comparisons (p>.05). For the changes in muscle activities before and after the ADI exercise, a significant difference exists between the two groups only for the changes in ES activities (p<.05); WA group exhibits higher changes than the normal group. By contrast, no significant difference exists between the two groups for the changes in GM activities (p>.05). Conclusion: After the ADI exercise, the compensatory action of ES in the female adults with WC is implied to decrease during PHE.

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.

Background: Prone hip extension (PHE) can be performed to measure the lumbopelvic motor patterns and motions. Imbalances in lumbopelvic muscle activity and muscle weakness can result in instability including pain in lumbopelvic region. The posterior oblique sling (POS) muscles contribute to dynamic lumbopelvic stability. In addition, POS are anatomically aligned with the trapezius muscle group according to shoulder positions. Objects: This study compared the electromyography (EMG) activity of POS and pelvic compensations during PHE with and without pre-activation of lower trapezius muscle (lowT). Methods: Sixteen healthy males were recruited. PHE was performed in randomized order: PHE with and without lowT pre-activation. Surface EMG signals were recorded for biceps femoris (BF), gluteus maximus (GM) (ipsilateral), lumbar multifidus (MF) (bilateral), and the lowT (contralateral). An electromagnetic tracking motion analysis was used to measure the angle of pelvic rotation and anterior tilting. Results: The ipsilateral GM and bilateral MF EMG amplitudes were greater during PHE with lowT pre-activation compared to PHE without lowT pre-activation (p<.05). The BF amplitude during PHE without lowT pre-activation was significantly greater than that during PHE with lowT pre-activation (p<.05). The angles of pelvic rotation and anterior tilting during PHE with lowT pre-activation were significantly smaller compared to PHE without lowT pre-activation (p<.05). Conclusion: PHE with lowT pre-activation, which is aligned with the POS, showed more increased MF and GM muscular activity with smaller lumbopelvic compensations in rotation and anterior tilting compared to PHE without lowT pre-activation.

Active straight-leg raise (ASLR) is a physical evaluation procedure to test lumbar spine stability. Several previous studies have reported various methods to control the activation of abdominal muscles during ASLR. We investigated the effects of three different hip positions in frontal plane on abdominal muscles to increase or decrease the difficulty level of lumbar spine stability exercise during ASLR in pain free subjects. Eleven young and healthy subjects voluntarily participated in this study (6 men, 5 women; mean age=24.0±1.2 years, height=160.0±7.3 ㎝, weight=55.0±10.6 ㎏, body mass index=21.5±2.3 ㎏/㎡). The subjects had three trials on each ASLR with hip 10° adduction, neutral hip, and hip 30° abduction. Separate repeated-measures analysis of variance (ANOVA) and the post hoc Bonferroni tests (with α =.05/3=.017) were performed for each muscle among the three different hip positions in frontal plane (ASLR with hip 10° adduction, neutral hip, and hip 30° abduction). The ipsilateral external oblique (EO), contralateral EO, ipsilateral internal oblique/transverse abdominis (IO/TrA), and contralateral IO/TrA were significantly greater in ASLR with hip 30° abduction compared with ASLR with hip 10° adduction. Also, the ipsilateral EO, contralateral EO, and ipsilateral IO/TrA were significantly greater in ASLR with hip 30° abduction compared with ASLR with neutral hip. These results suggest that ASLR with hip 30° abduction and neutral would be useful method to strengthen the EO and IO/TrA. And, ASLR with hip 10° adduction would be effective in early stages of lumbar stabilization program due to low activation of EO and IO/TrA during maintaining of ASLR position with low load.

This study investigated the effects of axillary crutch length on trunk muscle activity and lumbo-pelvic-hip complex movements during crutch gait. Eleven healthy men participated in this study. The participants performed a three-point gait with optimal, shorter, and longer crutch lengths. Weight-bearing (WB) side was determined as the dominant leg side. The electromyography (EMG) activity of the bilateral rectus abdominis (RA) and erector spinae (ES) muscles and lumbo-pelvic-hip complex movements were monitored using a three-dimensional motion system with wireless surface EMG. Differences in the EMG activity of RA and ES muscles and range of motion (ROM) of lumbar spine, pelvis, and hip among conditions were analyzed using one-way repeated-measures analysis of variance, and a Bonferroni correction was conducted. There was less RA muscle activity on the WB side under the optimal crutch length condition compared with shorter and longer crutch length conditions (p<.05). The EMG activity of the RA muscle on the non-WB side and ES muscle on the WB side were significantly decreased under the optimal crutch length condition compared with shorter crutch length condition (p<.05). No significant differences in the EMG activity of the ES muscle on the non-WB side and ROM of lumbo-pelvic-hip complex were found among conditions (p>.05). These findings indicate that the optimal crutch length improves the trunk muscle efficiency during crutch gait.

Many muscles of the trunk and hip are capable of contributing to the stabilization and protection of the lumbar spine. To have optimal effectiveness, a training program should include dynamic back/stomach/hip exercises. This study was designed to assess the L5 level paraspinal, external abdominal oblique, and gluteus maximus muscle activities during various low back stabilization exercises. Participants were 26 healthy adults (13 males, 13 Females), aged 21 to 28 years. The surface electromyography (EMG) was recorded from the L5 level paraspinal, external abdominal oblique, and gluteus maximus muscles. The recorded signal was averaged and normalized to the maximal electromyographic amplitude obtained during the maximal voluntary contraction. The measurements were taken during 3 low back stabilization exercises. One-way analysis of variance with repeated measures was used to examine the difference, and a post hoc test was performed with least significant difference. A level of significance was set at p<.05. The significance of difference between men and women, and between the electromyographic recording sites was evaluated by an independent t-test. The EMG activity for the externus oblique and gluteus maximus muscles had significant differences among 3 exercises (p<.05). In males, the EMG activity for the external abdominal oblique muscle had significantly increased differences during exercises 1 and exercise 2 (p<.05). The gluteus maximus muscle had significantly increased differences during exercise 2 and exercise 3 (p<.05). In females, the multifidus muscle had significantly increased difference during exercise 3 (p<.05), the external abdominal oblique muscle had significantly increased difference during exercise 1 (p<.05). and the gluteus maximus muscle had significantly decreased difference during exercise 3 (p<.05). The results were that the external abdominal oblique muscle was apparently activated during the curl-up exercise in females and males, and the multifidus muscle was apparently activated during the bridging exercise in females and during the sling exercise in males and females.1)In comparison of the %MVC between males and females, exercise 2 and exercise 3 apparently activated of the multifidus and gluteus maximus muscles in both males and females (p<.05). The EMG activity of the gluteus maximus muscle of the males significantly increased during exercise 2 and exercise 3 (p<.05). The EMG activity the multifidus muscle of the females was significantly increased during exercise 2 and exercise 3 (p<.05). More research is needed to understand the nature of motor control problems in the deep muscles in patients with low back pain.