Background: The weakness of the gluteus medius (GM) is associated with various musculoskeletal disorders. The increasing GM activity without synergistic dominance should be considered when prescribing pelvic drop exercise (PD). Isometric hip extension or flexion of the non-weight bearing leg using thera-band at the ankle during PD may influence hip abductor activities. Objects: To determine how isometric hip extension or flexion of the non-weight bearing leg using thera-band at the ankle during PD influences the activities of three subdivisions of GM (anterior, GMa; middle, GMm; posterior, GMp), tensor fasciae latae (TFL), contralateral quadratus lumborum (QL), and GMp/TFL, GMm/QL activity ratios in patients with GM weakness. Methods: Twenty-three patients with GM weakness were recruited. Three types of PD were performed: PD, PD with an isometric hip extension of the non-weight bearing leg (PDE), and PD with an isometric hip flexion of the non-weight bearing leg (PDF). Surface electromyography (SEMG) was used to measure hip abductor activities. One-way repeated-measures analysis of variance was used to assess the statistical significance of muscle activities and muscle activity ratios. Results: GMa, GMm, and GMp activities were significantly greater during PDF than during PD and PDE (p < 0.001, p = 0.001; p = 0.001, p = 0.005; p = 0.004, p = 0.004; respectively). TFL activity was significantly greater during PDE than during PD and PDF (p < 0.001, p < 0.001, respectively). QL activity was significantly greater during PDF than during PD (p = 0.003). GMp/TFL activity ratio was significantly lower during PDE than during PD and PDF (p = 0.001, p = 0.001, respectively). There were no significant differences in the GMm/QL activity ratio. Conclusion: PDF may be an effective exercise to increase the activities of all three GM subdivisions while minimizing the TFL activity in patients with GM weakness.

Background: The lateral step down (LSD) is a form of stair negotiation used by the elderly because it requires less movement of the lower extremity. Although it is necessary to study the amount of pelvic drop and the strength of a hip abductor during LSD for intervention, limited studies have investigated the relationship between the amount of pelvic drop and strength of a hip abductor during LSD in elderly people. Objects: This study aimed to determine the relationship between the amount of pelvic drop on an unsupported leg and the strength of the hip abductor during LSD in the elderly. Methods: Thirty elderly people (male: 17, female: 13) were recruited. Subjects performed the LSD task, and the evaluator measured and the amount of pelvic drop on an unsupported side. Also, the isometric strength of the hip abductor was measured in a supine position. Results: We found significant relationships between the strength of the hip abductor and the amount of pelvic drop (r = –0.386). The average hip abductor strength normalized by body weight was 1.06 N/kg (max: 1.99, min: 0.52) and the average contralateral pelvic drop (CPD) angle was 4.16° (max: 15.3, min: 0). Conclusion: Our results indicated that the strength of the hip abductor had a moderate correlation with the CPD during a LSD in the elderly. Hip abductor weakness could translate into altered movement of the pelvis.

Background: Gluteus medius muscle is important for the stability of hip joint. The sufficient core stability can be contributed to the performance of gluteus medius muscle in standing position. In addition, the external support may affect core stability in standing position. Objects: The purpose of this study was to investigated the effectiveness of the external support on the strength and muscle activity of hip abductor muscle during hip abduction in standing position in subjects without core stability. Methods: Fifteen subjects participated in this study. The subjects were evaluated by using the double-leg lowering with bent knees to measure the core stability. The strength and muscle activity of hip abductors was measured in standing position with the condition with and without external support using the tensiometer sensor and the surface electromyography. The paired t-test was used to investigate the difference between hip abductor strength and activity according to external support. The level of statistical significance was set at α = 0.05. Results: The hip abductor strength and muscle activity of gluteus medius muscle with external support were significantly greater than those without external support during hip abduction in standing position (p < 0.05). Conclusion: During hip abduction in standing position, the external support may be contributed to the improvement of the hip abductor strength and muscle activity of gluteus medius especially in the subjects without core stability.

Background: Many previous studies recommended the side-lying hip abduction (SHA) exercise for targeting the gluteus medius (Gmed) and gluteus maximus (Gmax) muscle activity while the decreasing tensor fasciae latae (TFL) activation. Mischoice of hip position and angle in SHA may increase the risk of lower extremity injuries and undesirable muscle activation. However, information is limited on the effect of composite hip flexion angles and hip rotation on the gluteal muscle activity during SHA. Objects: This study aimed to compare muscle activity (Gmed, TFL, and Gmax) and activity ratios (Gmed/TFL, Gmax/TFL, and Gmed/Gmax) using surface electromyography (EMG) during SHA exercise at three different hip flexion angles either with or without internal rotation (IR) in subjects with Gmed weakness. We hypothesized that applying hip flexion and IR during SHA would increase gluteal muscle activity and decrease TFL activity. Methods: Muscle activity and activity ratios in 20 volunteers with Gmed weakness during 6 different SHA were investigated with surface EMG. One-way repeated-measures analysis of variance was used to determine the statistical significance. Results: Significant differences were found among the six different exercises for Gmed (F2,41=11.817, p<.001) and Gmax (F3,52=5.513, p=.003) muscle activity, and Gmed/TFL (F3,54=8.735, p<.001) and Gmax/TFL (F2,37=4.019, p=.028) activity ratios. Conclusion: Applying hip flexion is an effective method for increasing gluteal activity, and it elicits great Gmed/TFL and Gmax/TFL activity ratios during SHA in subjects with Gmed weakness.

The purpose of this study was to examine the effect of the hip internal rotation on knee extensor and hip abductor electromyographic (EMG) activity during stair up and stair down mobility. Eighteen healthy subjects were recruited. All subjects performed stair up and down movements on a step of 30cm height while maintaining the hip in neutral (condition 1) and hip in internal rotation (condition 2). Surface EMG activity was recorded from five muscles (gluteus maximus, vastus lateralis (VL), vastus medialis oblique (VMO), posterior gluteus medius (Gmed), and tensor fascia latae (TFU)) and hip internal rotation angle was measured using a three dimensional motion analysis system The time period for stair up and down was normalized using the MatLab 6.5 program, and EMG activity was normalized to the value of maximal voluntary isometric contraction (%MVIC). The EMG activities according to the hip rotation (neutral or internal rotation) during the entire time period of stair up and down in each phase were compared using a paired t-test. During the entire period of stair up, the EMG activities of VL and TFL in condition 2 were significantly greater than in condition 1 (p<.05). During the entire period of stair down, the EMG activities of VL and TFL in condition 2 were significantly greater than in condition 1 (p<.05). However, the EMG activities of the other muscles were not significantly different between the conditions (p>.05). These results suggest that the stair up and down maintaining hip internal rotation was could be a contributing factor on patellar lateral tracking.

The right hip abductor musculature has been reported to demonstrate "stretch weakness" attributable to chronic elongation imposed by standing posture common to right-handed healthy persons. Kendall and associates have described the concept of "stretch weakness",. The purpose of this study was to assess isometric hip abduction torque and surface electromyographic activity (using MYOMED 432) in a sample of 40 healthy right-handed persons (20 male, 20 female), all of whom agreed to participate in the study, and compare side difference in the hip abductor musculature. In order to assure the statistical significance of the results, the paired t test was applied at the .05 level of significance. The results were as follows: 1) The difference in apparent leg length of right and left legs was significant at the .05 level. 2) There was a significant difference between right and left pelvic height (standing position) at the 05 level measurements, and scapula height at the .05 level. 3) Power measurements and action potentials of right hip abductor were greater than the left hip abductor regardless of the range of joint motion (inner range, outer range) 4) The difference in muscle power and action potentials according to inner or outer range of both hip abductor were significant at the .05 level. 5) In supine during active left hip abduction, the appearance of action potentials in the right hip abductors is indicative of contra-lateral effect (p<.05) These results suggest: In healthy right-handed persons, the apparent leg length on the right is longer than on the left, and pelvic height is elevated on the right side. Muscle those and muscle action potentials of the right hip abductor are higher than those of the left hip abductor in the lengthened position. Therefore, the results in this study are contrary to Kendall's. This type of study should be carried out in many physical therapy departments.