Hip abductor muscle activity during walking in individuals with gluteal tendinopathy

Current and future advances in practice: tendinopathies of the hip

Tendinopathy describes persistent tendon pain and loss of function related to mechanical loading. Two common hip tendinopathies seen in practice are gluteal tendinopathy and proximal hamstring tendinopathy. Both conditions can be frustrating for patients and clinicians due to the delay in diagnosis, significant disability caused and lack of response to common treatments. Tendinopathy is a clinical diagnosis and can most often be made using findings from the patient interview and pain provocation tests, without the need for imaging. Specific education and progressive exercise offer a low-risk and effective option for gluteal tendinopathy and result in greater rates of treatment success than corticosteroid injection, both in the short term (8 weeks) and at 1 year. Proximal hamstring tendinopathy is a common, but less researched, and under-recognized cause of persistent ischial pain. As research on proximal hamstring tendinopathy is limited, this review summarizes the available evidence on diagnosis and treatment following similar principles to other well-researched tendinopathies.

Understanding muscle coordination during gait based on muscle synergy and its association with symptoms in patients with knee osteoarthritis

OBJECTIVE

We aimed to investigate the muscle coordination differences between a control group and patients with mild and severe knee osteoarthritis (KOA) using muscle synergy analysis and determine whether muscle coordination was associated with symptoms of KOA.

METHOD

Fifty-three women with medial KOA and 19 control patients participated in the study. The gait analyses and muscle activity measurements of seven lower limb muscles were assessed using a motion capture system and electromyography. Gait speed and knee adduction moment impulse were calculated. The spatiotemporal components of muscle synergy were extracted using non-negative matrix factorization, and the dynamic motor control index during walking (walk-DMC) was computed. The number of muscle synergy and their spatiotemporal components were compared among the mild KOA, severe KOA, and control groups. Moreover, the association between KOA symptoms with walk-DMC and other gait parameters was evaluated using multi-linear regression analysis.

RESULTS

The number of muscle synergies was lower in mild and severe KOA compared with those in the control group. In synergy 1, the weightings of biceps femoris and gluteus medius in severe KOA were higher than that in the control group. In synergy 3, the weightings of higher tibial anterior and lower gastrocnemius lateralis were confirmed in the mild KOA group. Regression analysis showed that the walk-DMC was independently associated with knee-related symptoms of KOA after adjusting for the covariates.

CONCLUSIONS

Muscle coordination was altered in patients with KOA. The correlation between muscle coordination and KOA may be attributed to the knee-related symptoms. Key points • Patients with knee osteoarthritis (OA) experienced a deterioration in muscle coordination when walking. • Loss of muscle coordination was associated with severe knee-related symptoms in knee OA. • Considering muscle coordination as a knee OA symptom-related factor may provide improved treatment.

Muscle synergies analysis shows altered neural strategies in women with patellofemoral pain during walking

Several studies suggest that the central nervous system coordinates muscle activation by modulating neural commands directed to groups of muscles combined to form muscle synergies. Individuals with patellofemoral pain (PFP) move differently from asymptomatic individuals. Understanding the neural strategies involved in the execution of tasks such as walking can help comprehend how the movement is planned and better understand this clinical condition. The objective of this study was to compare muscle synergies between women with and without PFP during walking. Eleven women with PFP and thirteen asymptomatic women were assessed using three-dimensional kinematics and electromyography (EMG) while walking at self-selected speed. Kinematics of the trunk, pelvis and lower limbs were analyzed through the Movement Deviation Profile. Muscle synergies were extracted from the EMG signals of eight lower limb muscles collected throughout the whole gait cycle. Kinematic differences between the two groups (p<0.001, z-score = 3.06) were more evident during loading response, terminal stance, and pre-swing. PFP group presented a lower number of muscle synergies (p = 0.037), and greater variability accounted for (VAFtotal) when using 3 (p = 0.017), 4 (p = 0.004), and 5 (p = 0.012) synergies to reconstruct all EMG signals. The PFP group also presented higher VAFmuscle for rectus femoris (p = 0.048) and gastrocnemius medialis (p = 0.019) when considering 4 synergies. Our results suggest that women with PFP show lower motor complexity and deficit in muscle coordination to execute gait, indicating that gait in PFP is the result of different neural commands compared to asymptomatic women.

Do posted foot orthoses alter hip biomechanics and pain during walking in women with greater trochanteric pain syndrome?

BACKGROUND

Greater trochanteric pain syndrome (GTPS), including gluteal tendinopathy and bursitis, is a common, painful and debilitating condition. It is thought to involve overload of the gluteal tendons, which may be amplified through increased hip adduction moment (HAM) seen during gait in these individuals. Reducing the aberrant HAM may improve pain and function in this population. We aimed to determine if medially-posted foot orthoses immediately reduce HAM and pain in females with GTPS during walking gait.

METHODS

A double-blind, repeated-measures trial with randomised intervention order compared three conditions in 53 women with GTPS. Participants acted as their own control during baseline (everyday-shoe insole), medially-posted (active) orthosis, or flat insert (sham orthosis) walking. Data were collected via three-dimensional gait analysis for HAM, hip, pelvic, and thorax kinematics; as well as ground reaction force; and pain via the numerical rating scale. Subgroup analysis was performed based on a pronated foot-posture defined by the Foot Posture Index.

RESULTS

A small pain reduction was found between the active orthosis and flat insert (mean difference = -0.444, p = 0.017). No difference was detected for pain between other condition comparisons. Thoracic lateral flexion increased at second-peak HAM between the baseline and active conditions (mean difference = -0.917, p = 0.040). No differences were detected for HAM, remaining kinematic or kinetic variables, or ground reaction force data across the three conditions. No significant differences were detected between any of the three conditions for biomechanical or pain data in the pronated-foot subgroup.

SIGNIFICANCE

A medially-posted foot orthosis did not immediately alter gait biomechanics or provide a clinically meaningful pain reduction in women with GTPS. There is uncertainty regarding the clinical benefit of orthoses in the management of GTPS. Longer-term follow-up or the use of customised orthoses may produce different outcomes and should be explored in future research.

Unilateral symptomatic Achilles tendinopathy has limited effects on bilateral lower limb ground reaction force asymmetries and muscular synergy attributes when walking at natural and fast speeds

BACKGROUND

Achilles tendinopathy (AT) may affect ground reaction force (GRF) and muscle synergy (MS) during walking due to pain, biological integrity changes in the tendon and neuroplastic adaptations. The objective of this study was to compare GRF asymmetries and MS attributes between symptomatic and asymptomatic lower limbs (LL) during walking at natural and fast speeds in adults with unilateral AT.

METHODS

A convenience sample consisting of twenty-eight participants walked on an instrumented treadmill at natural (1.3 m/s) and fast (1.6 m/s) speeds. Peak GRF were measured in mediolateral, anteroposterior and vertical directions. Individualized electromyography (EMG) activation profiles were time- and amplitude-normalized for three consecutive gait cycles and MS were extracted using non-negative matrix factorization algorithms. MS were characterized by the number, composition (i.e., weighting of each muscle) and temporal profiles (i.e., duration and amplitude) of the MS extracted during walking. Paired Student's t-tests assessed peak GRF and MS muscle weighting differences between sides whereas Pearson correlation coefficients characterized the similarities of the individualized EMG and MS activation temporal profiles within sides.

RESULTS

AT had limited effects on peak GRF asymmetries and the number, composition and temporal profiles of MS between symptomatic and asymptomatic LL while walking on a level treadmill at natural and fast speeds. In most participants, four MS with a specific set of predominantly activated muscles were extracted across natural (71 and 61%) and fast (54 and 50%) walking speeds for the symptomatic and asymptomatic side respectively. Individualized EMG activation profiles were relatively similar between sides (r = 0.970 to 0.999). As for MS attributes, relatively similar temporal activation profiles (r = 0.988 to 0.998) and muscle weightings (p < 0.05) were found between sides for all four MS and the most solicited muscles. Although the faster walking speed increased the number of merged MS for both sides, it did not significantly alter MS symmetry.

CONCLUSION

Faster walking speed increased peak GRF values but had limited effects on GRF symmetries and MS attribute differences between the LL. Corticospinal neuroplastic adaptations associated with chronic unilateral AT may explain the preserved quasi-symmetric LL motor control strategy observed during natural and fast walking among adults with chronic unilateral AT.

Difference in muscle synergies of the butterfly technique with and without swimmer's shoulder

This study aimed to investigate whether muscle synergy differs between swimmers with and without swimmer's shoulder in the butterfly technique. Muscle synergies, which can assess muscle coordination, were analyzed using surface electromyography. Twenty elite swimmers were included in this study (swimmer's shoulder: n = 8; control: n = 12). The motions involved in executing the butterfly technique were classified into the early pull-through, late pull-through, and recovery phases. Muscle synergy data analyzed using the nonnegative matrix factorization method were compared between the two groups.

The swimming velocities were 1.66 ± 0.09 m・s ⁻¹ and 1.69 ± 0.06 m・s ⁻¹ for the control and swimmer's shoulder groups, respectively. Four muscle synergies in both groups were identified: synergy #1, which was involved in the early pull; synergy #2, involved in the late pull; synergy #3, involved in the early recovery; and synergy #4, involved in pre- and posthand entry. Compared to the control group, the swimmer's shoulder group had a small contribution from the pectoralis major (p = 0.032) and a high contribution from the rectus femoris during the early pull phase (p = 0.036). In the late pull phase, the contribution of the lower trapezius muscle in the swimmer's shoulder group was low (p = 0.033), while the contribution of the upper trapezius muscle in the pre- and postentry phases was high (p = 0.032). In the rehabilitation of athletes with swimmer's shoulder, it is therefore important to introduce targeted muscle rehabilitation in each phase.

Motor control exercises versus general exercises for greater trochanteric pain syndrome: A protocol of a randomized controlled trial

Introduction

Greater trochanteric pain syndrome is an overarching term used to define pain and tenderness in the greater trochanteric region of the femur, which is more common in women. Abnormal control of lower limb movements and deficient neuromuscular parameters may lead to greater trochanteric pain syndrome; however, no studies have used neuromuscular training as a treatment strategy. Thus, this study aims to compare the effect of a protocol of general exercises versus a program of motor control training on pain at baseline and after treatment in women with greater trochanteric pain syndrome.

Methods

The study was approved by the Research Ethics Committee (CAAE: 87372318.1.0000.5406) and has been prospectively registered on the Brazilian Registry of Clinical Trials (RBR-37gw2x). Sixty participants will be randomized to receive motor control exercises or general exercises. The application will be performed twice a week for 8 weeks. The participants will be evaluated before the treatment (T0), after 8 weeks of intervention (T8) and after 60 weeks of intervention (T60). The primary outcome measures will be the hip pain intensity, and secondary outcomes will be muscle strength, kinesiophobia, global perceived effect, pain catastrophization, central sensitization and quality of life.

Conclusions

Studies have suggested that greater trochanteric pain syndrome may be related to poor hip and pelvic control, however, no study has investigated an exercise protocol focused on increasing the strength of the abductor and extensor muscles of the hip associated with pelvic control training, especially in positions of unilateral support, such as gait. This study will help determine whether greater trochanteric pain syndrome is related to abnormal control of lower limb movements.

Association of tensor fascia lata hypertrophy and fatty infiltration in the presence of abductor tendon tears: a radiographic study

Hip abductor tendon tears of the gluteus medius and minimus are becoming a well-recognized source of pain and dysfunction, primarily in middle-age females. Like the rotator cuff, fatty infiltration (FI) can occur after tearing of these tendons. While the association of TFL hypertrophy after abductor tendon tears has been established, its association with FI has not been well studied. Our hypothesis is that hypertrophy of the TFL will be associated with FI of the abductors. All patients &gt;18 years old undergoing primary surgical repair for a confirmed tears on MRI, without a history of prior hip surgery or osteoarthritis, were included. The following measurements were obtained from MRI: TFL cross-sectional area, TFL:sartorius volume ratio, and modified Goutallier grade of gluteus medius and minimus. Seventy patients met inclusion criteria and were divided in two groups, those with (n = 28) and those without FI (n = 42) of the abductors. The FI group was on average older (65 versus 58 years, P &lt; 0.00016). TFL hypertrophy and TFL:sartorius volume ratio were significantly associated with FI (P= 0.00069). Following abductor tendon tear and subsequent FI, there exists significant TFL hypertrophy in patients without a prior history of hip surgery in our patient cohort.

Tensor Fascia Latae Muscle Structure and Activation in Individuals With Lower Limb Musculoskeletal Conditions: A Systematic Review and Meta-Analysis

BACKGROUND

Dysfunction of the tensor fascia latae (TFL) muscle is often clinically implicated in many musculoskeletal disorders.

OBJECTIVE

To systematically review the literature of the TFL muscle to determine whether there are differences in its structure and activation between individuals with and without lower limb musculoskeletal conditions.

DATA SOURCES

A comprehensive search in MEDLINE, EMBASE, CINHAL, and LILACS was undertaken from year of inception to 9 July 2019.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

Studies that directly investigated the structure or activity of the TFL muscle between individuals with a lower limb musculoskeletal condition and a pain-free control group.

RESULTS

Seventeen studies were included (n = 556 participants), eight reporting structure and ten activation of the TFL muscle. Conditions included lateral hip pain, hip joint pathology, ACL injury, iliotibial band syndrome, and patellofemoral joint osteoarthritis. Meta-analysis identified with low confidence (p value = 0.07) a small tendency towards hypertrophy in the affected side of participants with hip joint diseases (SMD 0.37, 95% CI [- 0.02, 0.77]). Moderate effect sizes were found for a higher cross-sectional area of the TFL/sartorius ratio in abductor tendon tear (SMD 0.74; 95% CI [0.05, 1.43, p value = 0.04), and for a smaller body mass normalized TFL volume in patellofemoral joint osteoarthritis (SMD - 0.61; 95% CI [- 1.23, 0.00], p value = 0.05). Normalised electromyography (EMG) amplitude did not differ between groups for any condition, but when EMG was analysed as linear envelopes or synergies, some differences in pattern of TFL activation were observed between individuals with lateral hip pain and controls. Timing of TFL activation did not differ between individuals with knee conditions and controls.

CONCLUSIONS AND IMPLICATIONS

Common clinical assumptions of the role of TFL muscle in lower limb musculoskeletal conditions are not well investigated and poorly supported by current research. There are contradictory findings on the muscle size of TFL. Differing methodology in muscle activation studies precludes a clear interpretation for comparison between groups.

PROSPERO REGISTRATION NUMBER

CRD42017076160.

Quantification of muscle coordination underlying basic shoulder movements using muscle synergy extraction

Numerous muscles around the shoulder joint are required to work in a coordinated manner, even when a basic shoulder movement is executed. Muscle synergy can be utilized as an index to determine muscle coordination. The purpose of the present study was to investigate the muscle coordination among different shoulder muscles underlying basic shoulder movements based on muscle synergy. Thirteen men performed 14 multiplanar shoulder movements; five movements were associated with elevation and lowering, while five were associated with horizontal abduction and adduction. The four additional movements were simple rotations at different positions. Muscle activity was measured from 12 muscle portions using surface electromyography. Using the dimensionality reduction technique, synergies were extracted first for each movement separately ("separate" synergies), and then for the global dataset (containing all movements; "global" synergies). The least number that provided 90% of the variance accounted for was selected as the optimal number of synergies. For each subject, approximately two separate synergies and approximately six global synergies with small residual values were extracted from the separate and global electromyography datasets, respectively. Specific patterns of these muscle synergies in each task were observed during each movement. In the cross-validation method, six global synergies explained 88.0 ± 1.3% of the global dataset. These findings indicate that muscle activities underlying basic shoulder movements are expressed as six units, and these units could be proxies for shoulder muscle coordination.

Lesions of the abductors in the hip

Abductor tendon lesions and insertional tendinopathy are the most common causes of lateral thigh pain. Gluteal tendon pathology is more prevalent in women and frequency increases with age.

Chronic atraumatic tears result in altered lower limb biomechanics. The chief complaint is lateral thigh pain. Clinical examination should include evaluation of muscle strength, lumbar spine, hip and fascia lata pathology. The hip lag sign and 30-second single leg stance tests are useful in diagnosing abductor insufficiency.

Magnetic resonance imaging (MRI) is the gold-standard investigation to identify abductor tendon tears and evaluate the extent of muscle fatty infiltration that has predictive value on the outcome of abductor repair.

Abductor tendinosis treatment is mainly conservative, including non-steroidal anti-inflammatory medications, activity modification, local corticosteroid injections, plasma-rich protein, physical and radial shockwave therapy. The limited number of available high-quality studies on treatment outcomes and limited evidence between tendinosis and partial ruptures make it difficult to provide definite conclusions regarding the best management of gluteal tendinopathy.

Surgical management is indicated in complete and partial gluteal tendon tears that are unresponsive to conservative treatment.

There are various open and arthroscopic surgical procedures for direct repair of abductor tendon tears. There is limited evidence concerning surgical management outcomes. Prerequisites for effective tendon suturing are neurologic integrity and limited muscle fatty infiltration. Chronic irreparable tears with limited muscle atrophy and limited fatty infiltration can be augmented with grafts. Gluteus maximus or/vastus lateralis muscle transfers are salvage reconstruction procedures for the management of chronic end-stage abductor tears with significant tendon insufficiency or gluteal atrophy.

Cite this article: EFORT Open Rev 2020;5:464-476. DOI: 10.1302/2058-5241.5.190094

Hip abductor tendon tears: where are we now?

Hip abductor tendon tear is a difficult problem to manage. The hip abductor mechanism is made up of the gluteus medius and minimus muscles, both of which contribute to stabilising the pelvis through the gait cycle. Tears of these tendons are likely due to iatrogenic injury during arthroplasty and chronic degenerative tendinopathy. Ultrasound and magnetic resonance imaging have provided limited clues regarding the pattern of disease and further work is required to clarify both the macro and microscopic pattern of disease. While surgery has been attempted over the last 2 decades, the outcomes are variable and the lack of high-quality studies have limited the uptake of surgical repair. Hip abductor tendon tears share many features with rotator cuff tears, hence, innovations in surgical techniques, materials and biologics may apply to both pathologies.

Application of functional data analysis to explore movements: walking, running and jumping - A systematic review

Background Signals are continuously captured during the recording of motion data. Statistical analysis, however, usually uses only a few aspects of the recorded data. Functional data analysis offers the possibility to analyze the entire signal over time. Research question The review is based on the question of how functional data analysis is used in the study of lower limb movements. Methods The literature search was based on the databases EMBASE, PUBMED and OVID MEDLINE. All articles on the application of functional data analysis to motion-associated variables trajectories, ground reaction force,electromyography were included. The references were assessed independently by two reviewers. Results In total 1448 articles were found in the search. Finally, 13 articles were included in the review. All were of moderate methodological quality. The publication year of the studies ranges from 2009 to 2019. Healthy volunteers and persons with cruciate ligament injuries, knee osteoarthritis, gluteal tendinopathy, idiopathic torsional deformities, slipped capital femoral epiphysis and chronic ankle instability were examined in the studies. Movements were analyzed on basis of kinematics (3D motion analysis), ground reaction forces and electromyography. Functional Data Analysis was used in terms of landmark registration, functional principal component analysis, functional t-test and functional ANOVA. Significance Functional data analysis provides the possibility to gain detailed and in-depth insights into the analysis of motion patterns. As a result of the increase in references over the past year, the FDA is becoming more important in the analysis of continuous signals and the explorative analysis of movement data.

Physical findings differ between individuals with greater trochanteric pain syndrome and healthy controls: A systematic review with meta-analysis

BACKGROUND

Understanding of the biopsychosocial characteristics of greater trochanteric pain syndrome (GTPS), a prevalent lower limb tendinopathy, is currently lacking.

OBJECTIVES

To quantify differences in participant characteristics between individuals with GTPS and healthy control participants.

DESIGN

Systematic review of original studies with meta-analyses where appropriate.

METHODS

A comprehensive electronic search was undertaken in Pubmed, EMBASE, Web of Science and CINAHL for terms referring to GTPS. Studies that provided comparison of individuals with clinically characterized GTPS with healthy controls were included. Study quality was rated with the Joanna Briggs Institute Critical Appraisal Checklist for Cross Sectional Studies. Standardized mean differences were calculated and supported by narrative synthesis or meta-analyses where appropriate. Certainty of evidence was assessed based on the GRADE guidelines.

RESULTS

The search revealed 2798 studies, of which 13 studies from five research groups were included. There were 229 participants with at least three months duration of GTPS and 193 control participants. Individuals with GTPS displayed larger greater trochanteric width, greater body mass index, lower hip abductor muscle strength, higher hip abductor muscle activity, altered single leg loading and gait parameters including shorter step length and velocity. No studies investigating psychological features or sensory perception were identified. Quality of life was investigated in a single study.

CONCLUSIONS

Compared to healthy controls, participants with GTPS are more overweight, have poorer hip abductor muscle function and altered gait parameters. Overall quality of evidence across studies was very low based on GRADE guidelines.

Physiotherapy management of greater trochanteric pain syndrome (GTPS): an international survey of current physiotherapy practice

OBJECTIVES

This study aimed to establish and compare current physiotherapy management of GTPS in Australia, New Zealand (NZ) and Ireland.

DESIGN

Cross-sectional observational survey of physiotherapists.

METHODS

An online survey was distributed to registered musculoskeletal physiotherapists in Australia, NZ and Ireland. Ordinal and nominal data were analysed using frequency counts or mean ranks; median and interquartile ranges were calculated for numerical data. Inter-country comparisons were made using Chi-squared analyses for nominal/ordinal data and Kruskal-Wallis tests for numerical data. Statistical significance was set at P<0.05.

RESULTS/FINDINGS

Valid responses were received from 361 physiotherapists, 61% were female and 80% worked in private practice. Overall, consistency in treatment of GTPS was observed across the three countries. All physiotherapists used education and exercise (most commonly strengthening and neuromuscular control) primarily targeting the gluteal muscles. Other interventions included massage (90%), stretching (53%), range of motion (40%), thermal modalities (50%), taping (38%) and electrotherapy (25%), whilst 40% commonly recommended up to 2 to 3 corticosteroid injections per patient/per annum. Physiotherapists used pain severity scales as their primary outcome measure (79%). Single leg stance was the most common physical measure used (68%), and global rating scores or standardised physical measures were less commonly used.

CONCLUSION

This international survey established the physiotherapy management of GTPS. Education used in conjunction with exercise is in line with current evidence, but a proportion of clinicians use adjunct treatments without clear rationale or supporting evidence. Results indicate the need to further define optimal management of GTPS using robust methodologies such as randomised controlled trials.

Current trends in sport and exercise hip conditions: Intra-articular and extra-articular hip pain, with detailed focus on femoroacetabular impingement (FAI) syndrome

Musculoskeletal conditions, such as hip pain are leading causes of pain and disability. Hip pain is the second most common cause of lower limb musculoskeletal pain, and is commonly seen in active individuals. Hip and groin pain may have intra-articular and extra-articular causes. Femoroacetabular impingement (FAI) syndrome and the associated pathologies are common intra-articular causes of hip and groin pain in active individuals. There are also a number of extra-articular causes of pain, which include musculotendinous conditions, extra-articular impingements and the clinical entities of groin pain described in the Doha agreement. This chapter will describe these, with a detailed focus on FAI syndrome. Specifically, it addresses: 1. What is and what causes FAI syndrome; 2. How do I diagnose FAI syndrome; and 3. What is the evidence-based approach to managing FAI syndrome?

The Modified Resisted Internal Rotation Test for Detection of Gluteal Tendon Tears

Greater trochanteric pain syndrome (GTPS) has received increasing attention in recent years. Most patients with GTPS present with trochanteric bursitis and respond to nonoperative treatment. However, a subset of patients may have persistent lateral hip pain or recalcitrant GTPS resulting from an undiagnosed gluteal tendon tear. Recalcitrant GTPS may be a debilitating condition in this patient subset. There is a need for an accurate and evidence-based physical examination maneuver to aid in earlier diagnosis of gluteal tendon tears and timely intervention in these patients. Most studies evaluating gluteal tendinopathy fail to assess surgical indications and instead focus on identifying trochanteric bursitis, which may or may not require surgical treatment. The modified resisted internal rotation test has been used in our practice to detect gluteus medius tendon tears in the recalcitrant GTPS patient population. Fundamental anatomic, biomechanical, electromyographic, and clinical data have been reviewed to make this an evidence-based clinical test for early detection of this pathology.

Neuromuscular control during gait in people with haemophilic arthropathy

INTRODUCTION

Effects of haemophilic arthropathy on neuromuscular control during gait are currently unknown.

AIMS

(a) To assess how haemophilic arthropathy affects the complexity of neuromuscular control during gait; (b) To investigate the relationship between complexity of neuromuscular control and joint impairment.

METHODS

Thirteen control subjects (CG) walked overground at their preferred and a slow velocity and thirteen people with haemophilic arthropathy (PWHA) walking at their preferred velocity. Surface electromyography (EMG) was collected from eleven leg muscles. Electromyography variance explained by muscle synergies (sets of co-activated muscles that can be recruited by a single signal) was calculated by the total variance accounted (tVAF). Three measures were used to evaluate complexity of neuromuscular control: (a) the number of synergies required for tVAF > 90%, (b) tVAF as a function of the number of muscle synergies, and (c) the dynamic motor control index (Walk-DMC). Impairment of ankle and knee joints was determined by the Haemophilia Joint Health Score (HJHS).

RESULTS

The same number of the muscle synergies was found for each group (P > 0.05). For both walking velocities tested, tVAF1 was higher in PHWA (P < 0.05). The Walk-DMC of PWHA was lower than that of the CG for both walking velocities (P < 0.05). For PWHA, no significant correlation was found between HJHS (sum knee and ankle) and Walk-DMC index (r = -0.32, P = 0.28).

CONCLUSIONS

These results indicate differences between PWHA and CG in the neuromuscular control of gait. The Walk-DMC and tVAF1 may be useful measures to assess changes in neuromuscular control in response to treatment.

You are better off running than walking revisited: Does an acute vestibular imbalance affect muscle synergies?

It has been suggested that vestibular cues are inhibited for the benefit of spinal locomotor centres in parallel with the increase in locomotion speed. This study aimed at quantifying the influence of a transient vestibular tone imbalance (TVTI) on gait kinematics, muscle activity and muscle synergies during walking and running. Twelve participants walk or run at a self-selected speed with or without TVTI, which was generated by 10 body rotations just prior the locomotion task. Three-dimensional lower-limb kinematic was recorded simultaneously with the surface electromyographic (EMG) activity of 8 muscles to extract muscle synergies via non-negative matrix factorization. Under TVTI, there was an increased gait deviation in walking compared to running (22.8 ± 8.4° and 8.5 ± 3.6°, respectively; p < 0.01), while the number (n = 4) and the composition of the muscle synergies did not differ across conditions (p = 0.78). A higher increase (p < 0.05) in EMG activity due to TVTI was found during walking compared to running, especially during stance. These findings confirmed that the central nervous system inhibited misleading vestibular signals according to the increase in locomotion speed for the benefit of spinal mechanisms, expressed by the muscle synergies.