Verification of a standardized method for inserting intramuscular EMG electrodes into uniquely oriented segments of gluteus minimus and gluteus medius

Assessment of the damage to hip abductor muscles in primary total hip arthroplasty with a minimally invasive anterolateral approach with or without trochanteric flip osteotomy

BACKGROUND

Although introduction of minimally invasive techniques via antero-lateral approaches considerably decreased prolonged limp after total hip arthroplasty (THA), potential damage to the abductor muscles is still a concern. This study aimed to evaluate the residual damage after primary THA with two types of antero-lateral approach by assessing fatty infiltration and atrophy of the gluteus medius (GMed) and gluteus minimus (GMin) muscles.

METHODS

We retrospectively analyzed 100 primary THAs using computed tomography; surgeries were performed by detaching the anterior part of the abductor muscles with a bone fragment (ALF) or without it (ALNF). The change in radiodensities (RDs), cross-sectional areas (CSAs), and clinical scores preoperatively and at 1 year after operation were evaluated.

RESULTS

The RD and CSA of GMed increased 1 year postoperatively in 86 and 81% of patients, respectively, while RD and CSA of GMin decreased in 71 and 94%, respectively. The improvement of RD of GMed was more frequently seen in the posterior rather than the anterior part, while GMin decreased in both parts. The RD decrease of GMin was significantly lower in the ALF group than the ALNF group (P= .0250). However, there was no difference in the clinical scores between the two groups. The change in the RD of GMed was the only factor that correlated with clinical scores.

CONCLUSION

The two antero-lateral approaches both improved the RD of GMed, recovery of which was significantly associated with postoperative clinical scores. Although the two approaches showed different recovery patterns in GMin until 1 year after THA, both showed similar improvements in clinical scores.

Evaluating the contribution of fat infiltration in anterior gluteus minimus muscle to walking ability in female with unilateral hip osteoarthritis and candidates for total hip arthroplasty

BACKGROUND

The purpose of this study is to investigate the relationship between gait and fat infiltration in anterior and posterior gluteus minimus in the patients with hip osteoarthritis.

METHODS

Ninety-one female patients who were diagnosed as the unilateral hip osteoarthritis, classified into Kellgren-Lawrence global scoring system grades 3 or 4, and candidate for total hip arthroplasty were retrospectively reviewed. The horizontally cross-sectional regions of interest for the gluteus medius and anterior and posterior gluteus minimus were manually circumscribed in a single transaxial computed tomography image and muscle density of those regions were obtained. The gait was assessed as the step and speed with the 10-Meter Walk Test. The multiple regression analysis was used to compare the step and speed with age, height, range of motion in flexion, the muscle density of anterior gluteus minimus in the affected side, and that of gluteus medius muscle in both affected and unaffected sides.

FINDINGS

Multiple regression analysis for step revealed that the muscle density of anterior gluteus minimus in the affected side and height were the independent predictors for step (R² = 0.389, p < 0.001). That for speed identified the muscle density of anterior gluteus minimus in the affected side as the only factor determining speed (R² = 0.287, p < 0.001).

INTERPRETATION

The fatty infiltration of anterior gluteus minimus muscle in affected side can be a predictor for the gait in in female with unilateral hip osteoarthritis and candidates for total hip arthroplasty.

Towards defining muscular regions of interest from axial magnetic resonance imaging with anatomical cross-reference: a scoping review of lateral hip musculature

Background

Measures of hip muscle morphology and composition (e.g., muscle size and fatty infiltration) are possible with magnetic resonance imaging (MRI). Standardised protocols or guidelines do not exist for evaluation of hip muscle characteristics, hindering reliable and valid inter-study analysis. This scoping review aimed to collate and synthesise MRI methods for measuring lateral hip muscle size and fatty infiltration to inform the future development of standardised protocols.

Methods

Five electronic databases (Medline, CINAHL, Embase, SportsDISCUS and AMED) were searched. Healthy or musculoskeletal pain populations that used MRI to assess lateral hip muscle size and fatty infiltration were included. Lateral hip muscles of interest included tensor fascia late (TFL), gluteus maximus, gluteus medius, and gluteus minimus. Data on MRI parameters, axial slice location, muscle size and fatty infiltrate measures were collected and analysed. Cross referencing for anatomical locations were made between MRI axial slice and E-12 anatomical plastinate sections.

Results

From 2684 identified publications, 78 studies contributed data on volume (n = 31), cross sectional area (CSA) (n = 24), and fatty infiltration (n = 40). Heterogeneity was observed for MRI parameters and anatomical boundaries scrutinizing hip muscle size and fatty infiltration. Seven single level axial slices were identified that provided consistent CSA measurement, including three for both gluteus maximus and TFL, and four for both gluteus medius and minimus. For assessment of fatty infiltration, six axial slice locations were identified including two for TFL, and four for each of the gluteal muscles.

Conclusions

Several consistent anatomical levels were identified for single axial MR slice to facilitate muscle size and fatty infiltration muscle measures at the hip, providing the basis for reliable and accurate data synthesis and improvements in the validity of future between studies analyses. This work establishes the platform for standardised methods for the MRI assessment of lateral hip musculature and will aid in the examination of musculoskeletal conditions around the hip joint. Further studies into whole muscle measures are required to further optimise methodological parameters for hip muscle assessment.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12891-022-05439-x.

The immediate effect of foot orthoses on gluteal and lower limb muscle activity during overground walking in healthy young adults

BACKGROUND

Although foot orthoses are often used in the management of lower limb musculoskeletal conditions, their effects on muscle activation is unclear, especially in more proximal segments of the lower limb.

RESEARCH QUESTION

Primary aim: Is there an immediate effect of foot orthoses on gluteal muscle activity during overground walking in healthy young adults? Secondary aim: Is there an immediate effect of foot orthoses on the activity of hamstring, quadriceps and calf muscles?

METHODS

In eighteen healthy young adults, muscle activity was recorded using fine wire electrodes for gluteus minimus (GMin; anterior, posterior) and gluteus medius (GMed; anterior, middle, posterior); and surface electrodes for gluteus maximus (GMax), hamstring, quadriceps and calf muscles. Participants completed six walking trials for two conditions; shoe and shoe with prefabricated foot orthoses. Muscle activity was normalised to the peak activity of the shoe condition and analysed using one-dimensional statistical non-parametric mapping to identify differences across the gait cycle.

RESULTS

Activity of GMed (anterior, middle, posterior) and GMin (posterior) was reduced in early stance phase when the orthosis was worn in the shoe (p < 0.05). GMin (anterior) activity was significantly reduced during swing (p < 0.05). Muscle activity was also significantly reduced during the orthoses condition for the lateral hamstrings and calf muscles (p < 0.05).

SIGNIFICANCE

Using foot orthoses may provide a strategy to reduce demand on GMin, GMed, lateral hamstring and calf muscles while walking.

A SYSTEMATIC REVIEW AND META-ANALYSIS OF COMMON THERAPEUTIC EXERCISES THAT GENERATE HIGHEST MUSCLE ACTIVITY IN THE GLUTEUS MEDIUS AND GLUTEUS MINIMUS SEGMENTS

Background

The gluteus medius (GMed) and gluteus minimus (GMin) muscle segments demonstrate different responses to pathology and ageing, hence it is important in rehabilitation that prescribed therapeutic exercises can effectively target the individual segments with adequate exercise intensity for strengthening.

Purpose

The purpose of this systematic review was to evaluate whether common therapeutic exercises generate at least high ( > 40% maximum voluntary isometric contraction (MVIC)) electromyographic (EMG) activity in the GMed (anterior, middle and posterior) and GMin (anterior and posterior) segments.

Methods

Seven databases (MEDLINE, EMBASE, CINAHL, AusSPORT, PEDro, SPORTdiscus and Cochrane Library) were searched from inception to May 2018 for terms relating to gluteal muscle, exercise, and EMG. The search yielded 6918 records with 56 suitable for inclusion. Quality assessment, data extraction and data analysis were then undertaken with exercise data pooled into a meta-analysis where two or more studies were available for an exercise and muscle segment.

Results

For the GMed, different variations of the hip hitch/ pelvic drop exercise generated at least high activity in all segments. The dip test, and isometric standing hip abduction are other options to target the anterior GMed segment, while isometric standing hip abduction can be used for the posterior GMed segment. For the middle GMed segment, the single leg bridge; side-lying hip abduction with hip internal rotation; lateral step-up; standing hip abduction on stance or swing leg with added resistance; and resisted side-step were the best options for generating at least high activity. Standing isometric hip abduction and different variations of the hip hitch/ pelvic drop exercise generated at least high activity in all GMin segments, while side-lying hip abduction, the dip test, single leg bridge and single leg squat can also be used for targeting the posterior GMin segment.

Conclusion

The findings from this review provide the clinician with confidence in exercise prescription for targeting individual GMed and GMin segments for potential strengthening following injury or ageing.

Level of Evidence

Level 1.

What is known about the subject

Previous reviews on GMed exercises have been based on single electrode, surface EMG measures at middle GMed segment. It is not known whether these exercises effectively target the other segments of GMed or the GMin at a sufficient intensity for strengthening.

What this study adds to existing knowledge

This review provides the clinician with confidence in exercise prescription of common therapeutic exercises to effectively target individual GMed and GMin segments for potential strengthening.

Pericapsular hip muscle activity in people with and without femoroacetabular impingement. A comparison in dynamic tasks

OBJECTIVES

Compare anterior pericapsular muscle activity between individuals with and without femoroacetabular impingement syndrome (FAIS) during dynamic tasks, to investigate whether muscle activity is consistent with a role in retracting the capsule to prevent impingement and active restraint of the femoral head in walking.

DESIGN

Cross-sectional.

SETTING

University-laboratory.

PARTICIPANTS

Thirteen athletes with FAIS and 13 pain-free controls.

MAIN OUTCOME MEASURES

Muscle activity was recorded using fine-wire (Iliocapsularis, iliacus and anterior gluteus minimus) and surface (rectus femoris) electromyography (EMG), during three hip flexion tasks (active and assisted hip flexion; squatting) and four walking trials.

RESULTS

Iliocapsularis EMG amplitude was no different between active and assisted hip flexion tasks around 90° of hip flexion in FAIS. There was no difference in EMG between groups in squatting. The pattern of burst activity preceding peak hip extension in iliacus, iliocapsularis, and anterior gluteus minimus was similar in both groups during walking.

CONCLUSION

In FAIS, similar activation of iliocapsularis during active and assisted hip flexion, despite reduced flexion torque demand in the latter, suggests a role in capsular retraction or enhanced hip joint protection. Pericapsular muscle activity in advance of peak hip extension during walking is consistent with a proposed contribution to femoral head control.

Gluteal muscle activity during running in asymptomatic people

BACKGROUND

Hip abductor muscle function is associated with running-related injuries. Previous electromyography (EMG) studies that reporting gluteal muscle activity when running have failed to account for the multiple segments of the gluteals, and have used surface electrodes, which may be contaminated by cross-talk of surrounding muscles.

RESEARCH QUESTION

This study aimed to: (i) develop EMG profiles of gluteus medius (GMed - anterior, middle and posterior) and gluteus minimus (GMin - anterior and posterior) segments during running; (ii) compare the activation patterns of each gluteal segment between running and walking; and (iii) compare surface EMG signals of running and walking to fine wire EMG signals of middle GMed.

METHODS

Ten physically active and asymptomatic people participated. Gluteal segment activation was assessed during running and walking over 10 m. Muscle activation was assessed using bipolar fine wire intramuscular EMG electrodes and GMed activation was also assessed using surface EMG.

RESULTS

During running, all gluteal segments presented peak amplitude during the stance phase and anterior GMin presented additional second peak amplitude during the swing phase. All gluteal segments evaluated demonstrated consistently higher amplitudes during the stance and swing phases of running compared to walking. The mean amplitude assessed using surface EMG was 32-87% higher compared to fine wire during both phases for running and walking.

SIGNIFICANCE

Greater activation of GMed segments during the stance phase and the increased anterior GMin activity during the swing phase indicate a potentially important role for pelvis and hip stabilization, respectively, which should be considered during development of targeted rehabilitation for running populations. The overestimated activation using surface electrodes highlights a limitation of using surface EMG during running and walking.

Gluteus medius and minimus activity during stepping tasks: Comparisons between people with hip osteoarthritis and matched control participants

BACKGROUND

Altered gluteus minimus (GMin) activity has been identified in people with hip osteoarthritis (OA) during gait with some evidence of altered gluteus medius (GMed) activity in patients with advanced OA. It is not known whether these muscles also exhibit altered activity during other functional tasks.

RESEARCH QUESTION

Does gluteal muscle activity during stepping tasks differ between people with hip OA and healthy older adults?

METHODS

Participants included 20 people with unilateral hip OA and 20 age-and sex-matched controls. Muscle activity in the three segments within GMed and two segments of GMin were examined using intramuscular electromyography during step-up, step-down and side-step tasks.

RESULTS

Participants in the OA group demonstrated reduced muscle activity early in the step-up task and a later time to peak activity in most muscle segments. Greater activity was identified in anterior GMin in people with hip OA during the side-step task. A delay in time to peak activity was identified in most muscle segments in people with OA during the side-step task.

SIGNIFICANCE

For participants with OA, reduced activity in most muscle segments and increased time spent in double limb stance during the step-up task could reflect the decreased strength and pain associated with single limb stance on the affected limb. This study provides further evidence of altered function of the deep gluteal muscles in people with hip OA and highlights the importance of addressing these muscles in rehabilitation.

Rehabilitation Exercises for the Gluteus Minimus Muscle Segments: An Electromyography Study

CONTEXT

The gluteus minimus (GMin) muscle consists of 2 uniquely oriented segments that have potential for independent function and have different responses to pathology and aging. For healthy young adults, it is unknown that which rehabilitation exercises specifically target the individual segments.

OBJECTIVE

To quantify segmental GMin activity for 6 common lower-limb rehabilitation exercises in healthy young adults and determine if significant differences exist in segmental activity levels between the exercises.

METHOD

Six common lower-limb rehabilitation exercises were performed by 10 healthy young adults with fine-wire electromyography (EMG) electrodes inserted into the anterior and posterior segments of the GMin muscle.

MAIN OUTCOME MEASURES

Electromyography signals were recorded, and median normalized exercise activity levels were reported and compared for each GMin segment across the 6 exercises.

RESULTS

High activity levels were generated in the anterior segment by the resisted hip abduction-extension exercise (51% maximum voluntary isometric contraction [MVIC]), whereas for the posterior segment, high activity levels were produced by the single-leg bridge (49% MVIC), the side-lie hip abduction (43% MVIC), the resisted hip abduction-extension exercise (43% MVIC), and the single-leg squat (40% MVIC). There were significant differences (P < .05) in the median electromyography activity levels for the anterior GMin segment but not for the posterior GMin segment across some of the exercises with large effect sizes.

CONCLUSION

Targeted rehabilitation exercises graded by exercise intensity can be prescribed specifically for the anterior and posterior GMin segments to aid in restoration of hip function following injury or aging.

Rehabilitation Exercises for the Gluteus Medius Muscle Segments: An Electromyography Study

CONTEXT

Many different rehabilitation exercises have been recommended in the literature to target the gluteus medius (GMed) muscle based mainly on single-electrode, surface electromyography (EMG) measures. With the GMed consisting of 3 structurally and functionally independent segments, there is uncertainty on whether these exercises will target the individual segments effectively.

OBJECTIVE

To measure individual GMed segmental activity during 6 common, lower-limb rehabilitation exercises in healthy young adults, and determine if there are significant differences between the exercises for each segment.

METHOD

With fine-wire EMG electrodes inserted into the anterior, middle, and posterior segments of the GMed muscle, 10 healthy young adults performed 6 common, lower-limb rehabilitation exercises.

MAIN OUTCOME MEASURES

Recorded EMG activity was normalized, then reported and compared with median activity for each of the GMed segments across the 6 exercises.

RESULTS

For the anterior GMed segment, high activity was recorded for the single-leg squat (48% maximum voluntary isometric contraction [MVIC]), the single-leg bridge (44% MVIC), and the resisted hip abduction-extension exercise (41% MVIC). No exercises recorded high activity for the middle GMed segment, but for the posterior GMed segment very high activity was recorded by the resisted hip abduction-extension exercise (69% MVIC), and high activity was generated by the single-leg squat (48% MVIC) and side-lie hip abduction (43% MVIC). For each of the GMed segments, there were significant differences (P < .05) in the median EMG activity levels between some of the exercises and the side-lie clam with large effect sizes favoring these exercises over the side-lie clam.

CONCLUSIONS

Open-chain hip abduction and single-limb support exercises appear to be effective options for recruiting the individual GMed segments with selection dependent on individual requirements. However, the side-lie clam does not appear to be effective at recruiting the GMed segments, particularly the anterior and middle segments.

Systematic differences of gluteal muscle activation during overground and treadmill walking in healthy older adults

Guteal muscle activation during walkway and treadmill walking was compared by means of Surface EMG (SEMG). Healthy older adults (50-75 years, n = 54; 29 females, 25 males) walked on a walkway (WW) at their self-selected slow, normal, and fast walking speeds and on a treadmill (TM) at 2, 3, 4, 5, and 6 km/h. Subject-individual, best-matched speed pairs were constituted and named SLOW, NORMAL, and FAST. Hip muscle activation was measured on both sides at mid-distance between the greater trochanter and the iliac crest by applying eight equally-spaced bipolar SEMG channels from ventral to dorsal (P1-P8). Grand averaged amplitude curves and mean amplitudes over the complete stride were analyzed to compare WW and TM walking. TM walking evoked significantly elevated mean amplitude levels, particularly at the ventral positions P1 to P4, which were disproportionately increased at SLOW. In grand averaged curves, corresponding significant amplitude differences between WW and TM were observed during load acceptance (SLOW; NORMAL), mid-stance (all speeds), and late swing phase (SLOW), with the number of significant differences decreasing for all electrode positions from SLOW to FAST. Compared to WW walking, TM walking may thus require systematically elevated effort of gluteal muscles, in particular at slow walking speed.

Targeted gluteal exercise versus sham exercise on self-reported physical function for people with hip osteoarthritis (the GHOst trial - Gluteal exercise for Hip Osteoarthritis): a protocol for a randomised clinical trial

BACKGROUND

Clinical practice guidelines recommend exercise as the first line of management for hip osteoarthritis, yet high-quality evidence from Cochrane reviews suggest only slight benefits for pain and physical function; and no benefit on quality of life (low-quality evidence). However, the scope of physical impairments identified in people with hip osteoarthritis may not have been adequately addressed with targeted rehabilitation options in previous randomised controlled trials (RCTs). Potential targeted options include gait retraining to address spatio-temporal impairments in walking; motor control training to address deep gluteal (gluteus minimus) dysfunction; and progressive, high-intensity resistance exercises to address atrophy of the gluteal muscles. The aim of this study is to investigate the effect of a targeted gluteal rehabilitation programme that incorporates gait retraining, motor control and progressive, high-intensity resistance-strength training, to address physical activity levels and self-reported physical function in people with mild to moderate disability from hip osteoarthritis.

METHODS

Ninety people diagnosed with mild to moderately disabling hip osteoarthritis will be recruited and randomised to receive one of two exercise programmes (sham or GHOst programme). Interventions will be 12 weeks in duration, with weekly, supervised physiotherapy sessions, and daily home exercises. Both groups will receive standardised education. Outcomes will be assessed at baseline, 7 weeks, 13 weeks (primary time-point) and 25 weeks. The primary outcome will be self-reported physical function measured with the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Secondary outcomes include physical activity measured with a tri-axial accelerometer, physical function tests, self-reported physical activity, isometric hip-muscle strength tests, hip-related patient-reported outcome measures, pain thoughts and depressive symptoms, quality of life, global rating of change, gluteal-muscle activity (electromyography (EMG)) and gluteal-muscle size and adiposity (magnetic resonance imaging (MRI)).

DISCUSSION

This will be the first study to compare a targeted gluteal rehabilitation programme to a sham exercise programme. The targeted GHOst programme includes exercises designed to address gait impairments as well as gluteal-muscle atrophy and dysfunction.

TRIAL REGISTRATION

Australian New Zealand Clinical Trials Registry, ID: ACTRN12617000970347 . Registered retrospectively on 5 July 2017. Protocol version 3.0.

Gluteus Minimus and Gluteus Medius Muscle Activity During Common Rehabilitation Exercises in Healthy Postmenopausal Women

Study Design Controlled laboratory study, cross-sectional. Background The gluteus medius (GMed) and gluteus minimus (GMin) provide dynamic stability of the hip joint and pelvis. These muscles are susceptible to atrophy and injury in individuals during menopause, aging, and disease. Numerous studies have reported on the ability of exercises to elicit high levels of GMed activity; however, few studies have differentiated between the portions of the GMed, and none have examined the GMin. Objectives To quantify and rank the level of muscle activity of the 2 segments of the GMin (anterior and posterior fibers) and 3 segments of the GMed (anterior, middle, and posterior fibers) during 4 isometric and 3 dynamic exercises in a group of healthy, postmenopausal women. Methods Intramuscular electrodes were inserted into each segment of the GMed and GMin in 10 healthy, postmenopausal women. Participants completed 7 gluteal rehabilitation exercises, and average normalized muscle activity was used to rank the exercises from highest to lowest. Results The isometric standing hip hitch with contralateral hip swing was the highest-ranked exercise for all muscle segments except the anterior GMin, where it was ranked second. The highest-ranked dynamic exercise for all muscle segments was the dip test. Conclusion The hip hitch and its variations maximally activate the GMed and GMin muscle segments, and may be useful in hip muscle rehabilitation in postmenopausal women. J Orthop Sports Phys Ther 2017;47(12):914-922. Epub 15 Oct 2017. doi:10.2519/jospt.2017.7229.

Detailed spatial characterization of superficial hip muscle activation during walking: A multi-electrode surface EMG investigation of the gluteal region in healthy older adults

PURPOSE

A multi-electrode array was used to generate spatially resolved Surface electromyography (SEMG) data of the hip muscles in healthy older adults. The cohort was meant to serve as an age-matched, normal control population for future surgical and rehabilitative studies in patients undergoing total hip arthroplasty, in view of the large, continuously increasing number of hip joint replacements.

METHODS

Bilateral hip muscle SEMG activity, including tensor fasciae latae (TFL), gluteus medius (Gmed), and gluteus maximus (Gmax), was measured during locomotion on a walkway at self-selected slow, normal, and fast walking speeds (age-matched cohort of 29 females and 25 males). Eight equally-spaced, vertically oriented bipolar channels were applied on a horizontal line at mid-distance between iliac crest and greater trochanter (length 17.5 cm; named P1 to P8). Time-independent parameters (e.g., mean amplitude) were derived from the amplitude curves expressed as root mean square.

RESULTS

The acquired SEMG data were not significantly influenced by gender (p = 0.202) or side (p = 0.313) and were therefore pooled. The most ventral to central electrode positions P1 to P5, representing TFL and ventral to central Gmed, showed the highest mean amplitude levels (averaged over the whole stride; 0.001 < p < 0.027 against P6 to P8; Bonferroni-adjusted paired t-test) at all walking speeds. Also, the respective curves showed two distinct amplitude peaks (representing load acceptance and hip stabilization during mid-stance), with a continuous increase of the first peak from P1 to P4 (most pronounced at fast speed) and the second peak from P1 to P3. Independently of the underlying individual muscles, both peaks displayed a continuous time shift from the most dorsal P8 to the most ventral P1 position, with the peaks for the ventral positions occurring at later time points during the normalized stride.

CONCLUSIONS

The continuously changing activation patterns of the superficial muscles in the gluteal region during walking may reflect function-driven, finely tuned coordination patterns of neighboring muscles and muscle segments, rather than independent activation of anatomically defined muscles. This may be important for the definition of specific target parameters for the improvement and/or normalization of muscle function during training and post-injury rehabilitation.

Therapeutic Effect of Microcurrent Therapy in Children With In-toeing Gait Caused by Increased Femoral Anteversion: A Pilot Study

Objective

To investigate the efficacy of portable microcurrent therapy device (PMTD) of the hip internal rotators in the treatment of in-toeing gait caused by increased femoral anteversion in children over 8 years of age.

Methods

Eleven children (22 legs; 4 boys and 7 girls; mean age, 10.4±1.6 years) with in-toeing gait caused by increased femoral anteversion were included in the present study. All children received 60 minutes of PMTD (intensity, 25 µA; frequency, 8 Hz) applied to the hip internal rotators daily for 4 weeks. Hip internal rotation (IR) angle, external rotation (ER) angle, and midmalleolar-second toe angle (MSTA) measurement during stance phase at transverse plane and Family Satisfaction Questionnaire, frequency of tripping and fatigue like pains about the PMTD were performed before treatment and at 4 weeks after initial PMTD treatment. Paired t-test and Fisher exact test were used for statistical analysis.

Results

Hip IR/ER/MSTA was 70.3°±5.4°/20.1°±5.5°/–11.4°±2.7°, and 55.7°±7.8°/33.6°±8.2°/–2.6°±3.8° before treatment and at 4 weeks after initial PMTD treatment, respectively (p<0.01). Ten of 11 (91%) children's family stated that they were generally satisfied with the PMTD treatment. The frequency of tripping and fatigue like pains was significantly lower at 4 weeks after PMTD treatment (p<0.05). Excellent inter-rater and intra-rater reliability was observed for repeated MSTA measurements between the examiners (k=0.91–0.96 and k=0.93–0.99), respectively.

Conclusion

PMTD of the hip internal rotators can be effective in improving the gait pattern of children with in-toeing gait caused by increased femoral anteversion.

Lumbopelvic muscle activation patterns in adolescent fast bowlers

INTRODUCTION

Adolescent fast bowlers are prone to sustaining lumbar injuries. Numerous components have been identified as contributing factors; however, there is limited empirical evidence outlining how the muscles of the lumbopelvic region, which play a vital role in stabilising the spine, function during the bowling action and the influence of such activation on injuries in the fast bowler.

METHODS

Surface electromyography was utilised to measure the function of the lumbar erector spinae, lumbar multifidus, gluteus medius and gluteus maximus muscles bilaterally during the fast bowling action in a group of 35 cricket fast bowlers aged 12-16 years.

RESULTS

Two prominent periods of activation occurred in each of the muscles examined. The period of greatest mean activation in the erector spinae and multifidus occurred near back foot contact (BFC) and within the post-ball-release (BR) phase. The period of greatest mean activation for the gluteus medius and gluteus maximus occurred during phases of ipsilateral foot contact.

DISCUSSION

The greatest periods of muscle activation in the paraspinal and gluteal muscles occurred at times where vertical forces were high such as BFC, and in the phases near BR where substantial shear forces are present.

CONCLUSION

The posterior muscles within the lumbopelvic region appear to play a prominent role during the bowling action, specifically when compressive and shear forces are high. Further research is required to substantiate these findings and establish the role of the lumbopelvic muscles in the aetiology of lumbar injury in the cricket fast bowler.

Gluteal muscle function and size in swimmers

OBJECTIVES

To compare the gluteus medius and minimus segments size and activity in swimmers versus non-swimmers.

DESIGN

Case matched-control cross-sectional study.

METHODS

The three segments of gluteus medius (anterior, middle and posterior) and two segments of gluteus minimus (anterior and posterior) were evaluated using electromyography and magnetic resonance imaging in 15 swimmers (7 elite and 8 non-elite) and 15 gender- and aged-matched controls. For each muscle segment, values were obtained for peak amplitude, average amplitude, and time to peak from each phase of the gait cycle (0-20%, 20-60%, and total stance).

RESULTS

The pattern of anterior gluteus minimus EMG activity in swimmers demonstrated additional activity early in the gait cycle when compared with controls. The segmental differences between anterior and posterior gluteus minimus during gait identified in the control group were not present in the swimmers. Overall, there were no significant differences in the gluteus medius EMG characteristics between groups and muscle size was not significantly different between groups for any of the hip abductor muscles.

CONCLUSIONS

The preliminary evidence of non-segmental differences within the gluteus minimus of swimmers (as opposed to non-swimmers) might implicate reduced-gravity environments in contributing to subsequent changes in deep stabiliser muscles. Such changes might predispose the athlete to a greater risk of lower limb injury during weight bearing activities.

Verification of a standardized method for inserting intramuscular electromyography electrodes into teres minor using ultrasound

The close proximity of the infraspinatus to the teres minor and their functional similarity in producing external rotation of the glenohumeral joint make accurate insertion of electromyographic (EMG) electrodes into the teres minor difficult and questionable even when published guidelines are followed. The primary aim of this study was to examine the anatomical support for the current guidelines for inserting intramuscular EMG electrodes into the teres minor muscle. The secondary aim was to provide a technical description for ultrasound-guided electrode insertion into the teres minor. Intramuscular electrodes were inserted into four cadaveric shoulders using markings based on the current guidelines. EMG electrodes were also inserted into the teres minor of four healthy male participants using real-time ultrasound (RTUS) guidance. Systematic dissections of the cadaver specimens revealed that the electrode had been successfully inserted into the teres minor muscle in only one out of the four. In the remaining three specimens, the needle lodged in the infraspinatus muscle belly at distances ranging from 3 to 17 mm medial to the teres minor. Using RTUS guidance, the electrodes were successfully inserted into the teres minor in all participants, as confirmed by visual inspection with RTUS. This study confirms that the current EMG electrode insertion guidelines for the teres minor are not accurate and RTUS ensures the placement of electrodes into the teres minor rather than the adjacent infraspinatus muscle.

The variable roles of the upper and lower subscapularis during shoulder motion

BACKGROUND

The varied roles of the subscapularis muscle as an internal rotator of the humerus, a shoulder abductor, a humeral head depressor and an anterior stabiliser may be a result of differing innervation and lines of torque between its superior and inferior components. The aims of the study were to investigate the differences in the level of muscle activation between the upper and lower subscapularis during abduction, flexion, internal and external rotation movements, and temporal characteristics during abduction and flexion.

METHODS

Intramuscular electrodes recorded electromyographic muscle activity from the upper and lower subscapularis muscles of the dominant throwing arm of twenty-four normal subjects. Participants completed ten repetitions of four shoulder movements - abduction, flexion, internal rotation and external rotation. Muscle activity was expressed as a percentage of maximum voluntary isometric contraction.

FINDINGS

The lower subscapularis was found to activate at a higher level than the subscapularis during abduction, flexion and external rotation movements and this was significant during concentric and eccentric phases of abduction and flexion (<0.001). During internal rotation, upper subscapularis muscle activity mirrored that of lower subscapularis, with a mean difference of 1.14%. Neither upper nor lower subscapularis had onset data commencing prior to the abduction movement; however upper subscapularis activated significantly later than lower subscapularis (P=0.018).

INTERPRETATION

The lower subscapularis has significantly higher muscle activity during shoulder elevation and this might reflect its greater role as a humeral head depressor and anterior stabiliser.

Gluteus minimus: an intramuscular EMG investigation of anterior and posterior segments during gait

Gluteus minimus is believed to consist of two structurally and functionally unique segments (anterior and posterior); however there is a lack of electromyography (EMG) research that attempts to verify current theoretical knowledge of this muscle. The purpose of this study was therefore to evaluate the function of gluteus minimus during gait, and to determine whether anterior and posterior segments are functionally independent. Bipolar fine wire intramuscular EMG electrodes were inserted into anterior and posterior gluteus minimus segments of fifteen healthy volunteers (9 males) according to previously verified guidelines. Participants completed a series of four walking trials, followed by maximum voluntary isometric contractions in five different positions. Temporal and amplitude variables for each segment were compared across the gait cycle with independent t-tests. The relative contribution of each segment to the maximum resisted trials was compared with Mann-Whitney U tests (α = 0.05). Anterior and posterior segments were contracting at different relative intensities for three of the five maximum resisted trials (effect size = 0.39 to 0.62, P < 0.037). The posterior segment was larger in EMG amplitude (peak and average) during the first 20% of the gait cycle (effect size = 0.96 to 1.03, P < 0.02), while the anterior segment peaked later in the stance phase (effect size = 0.83, P = 0.034). Gluteus minimus is therefore composed of functionally independent segments. These results build on contemporary theoretical knowledge and may signify hip stabilising roles for each segment across different phases of the gait cycle.