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  • 1. Alm, M.
    et al.
    Gutierrez-Farewik, Elena M.
    Hultling, C.
    Saraste, H.
    Clinical evaluation of seating in persons with complete thoracic spinal cord injury2003In: Spinal Cord, ISSN 1362-4393, E-ISSN 1476-5624, Vol. 41, no 10, p. 563-571Article in journal (Refereed)
    Abstract [en]

    Study Design: Consecutive male patients studied with photographic measurement of a combination of clinical methods. Objectives: To describe seating in individuals with complete thoracic spinal cord injury (SCI) by using a combination of clinical methods. Setting: Spinalis SCI unit, Stockholm, Sweden. Methods: Wheelchair specifications were documented. Measurements of posture from photographs in 30 male subjects with complete thoracic SCI, sitting in a relaxed and an upright position on a standardized surface and in a wheelchair were calculated. A comparison was made between positions and seating surfaces. An examiner's classification of lower trunk position in wheelchair was compared to subjects' evaluations. SCI subjects reported sitting support, satisfaction, and wishes for improvement. Results: Most SCI subjects used similar wheelchair specifications. None of the backrests were custom designed. Relatively small differences were found between the relaxed and upright position in the wheelchair regarding measurements of posture and according to the examiner's classification of the lower trunk position. Only 13/30 SCI subjects were sitting with the lower trunk centered relative to the backrest in the upright position. The examiner's classification and the subjects' evaluation of asymmetric sitting were not always in agreement. Only 12/30 SCI subjects were satisfied with their way of sitting. Conclusion: Current wheelchair specifications and adjustments seem to inhibit a postural correction towards upright sitting and fail to provide sufficient lateral support. Findings indicate an inability for SCI subjects to vary their sitting position in a wheelchair to a large extent. Both an examiner's classification and subjects' evaluation of asymmetric sitting are necessary to obtain a sufficient knowledge base for subsequent adjustment. By using methods regarding different aspects of seating, a more comprehensive view of seating was achieved. The combination of clinical methods seems to be useful in order to describe seating in individuals with complete thoracic SCI.

  • 2. Bartonek, A.
    et al.
    Gutierrez-Farewik, Elena M.
    Haglund-Akerlind, Y.
    Saraste, H.
    The influence of spasticity in the lower limb muscles on gait pattern in children with sacral to mid-lumbar myelomeningocele: a gait analysis study2005In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 22, no 1, p. 10-25Article in journal (Refereed)
    Abstract [en]

    Gait analysis and recording of standing position were performed in 38 ambulatory children with myelomeningocele. Thirty-four were independent ambulators and four required a walking aid. All subjects were assigned one of four muscle function groups based on muscle strength. They were also divided into subgroups based on the distinction between flaccid and spastic paresis in the lower limb joints. A comparison was made between the gait pattern of the children with spasticity and that of the children with flaccid paresis in each muscle function group. Spasticity in only the ankle joint muscles influenced the subject's gait and standing position compared to the subgroups with a flaccid paresis. Even larger deviations in gait and standing position were observed when spasticity occurred in muscles at the knee and hip joints. When setting ambulatory goals the presence of additional neurological symptoms such as spasticity and inadequate balance should be taken into consideration.

  • 3. Bartonek, A.
    et al.
    Lidbeck, C. M.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Influence of external visual focus on gait in children with bilateral cerebral palsy2016In: Pediatric Physical Therapy, ISSN 0898-5669, E-ISSN 1538-005X, Vol. 28, no 4, p. 393-399Article in journal (Refereed)
    Abstract [en]

    Purpose: To explore whether focusing a target influenced gait in children with cerebral palsy (CP) and typical development (TD). Methods: Thirty children with bilateral CP (Gross Motor Function Classification System [GMFCS] I-III) and 22 with TD looked at a light at walkway end (Gaze Target) while walking and returned (No Target). Results: During Gaze versus No Target, children with TD reduced temporal-spatial parameters and movements in the sagittal (SPM) and transverse planes. In comparison, during Gaze Target, children in CP1 (GMFCS I) had larger trunk SPM, children in CP2 (GMFCS II) larger neck (SPM), and children in CP3 (GMFCS III) greater head and neck frontal plane movements, and reduced cadence and single support. Conclusions: Focusing a target altered gait in children with CP. Children in CP1 reduced movements similar to children with TD, children in CP2 behaved nearly unchanged, whereas children in CP3 reduced movements and temporalspatial parameters, potentially as a consequence of lack of sensory information from lower limbs.

  • 4. Bartonek, Asa
    et al.
    Eriksson, Marie
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    A new carbon fibre spring orthosis for children with plantarflexor weakness2007In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 25, no 4, p. 652-656Article in journal (Refereed)
    Abstract [en]

    We tested a new orthosis with a carbon fiber spring constructed to enable energy storing during increasing dorsiflexion in mid-stance, and to use the energy at the end of stance phase to aid push-off. The orthosis was tested on children with plantarflexor weakness due to motor disorders. All subjects were tested with 3D gait analysis with both the new orthosis and with their regularly used orthosis. In this technical note, the results of three individuals are reported. The preliminary findings show increased dorsiflexion, altered knee kinematics and improved kinetic and temporo-spatial parameters. Although the carbon spring orthosis influenced the subjects' gait in different ways, we conclude that the tested subjects with plantarflexion weakness benefit from the carbon fiber spring orthoses during walking. The parents' and children's subjective impressions as acquired from a questionnaire were also positive.

  • 5. Bartonek, Asa
    et al.
    Eriksson, Marie
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Effects of carbon fibre spring orthoses on gait in ambulatory children with motor disorders and plantarflexor weakness2007In: Developmental Medicine & Child Neurology, ISSN 0012-1622, E-ISSN 1469-8749, Vol. 49, no 8, p. 615-620Article in journal (Refereed)
    Abstract [en]

    A consecutive series of 17 children (six males, 11 females; mean age 11y 11mo [SD 4y 5mo]; range 3y 11mo-17y 4mo) with plantarflexor weakness was assessed to compare gait differences between a carbon fibre spring orthosis (CFSO) and participants' regular orthoses. Twelve children had myelomeningocele, four children had arthrogryposis, and one child had neuropathy with peripheral muscle pareses. All participants underwent clinical examination and 3D gait analysis. Parents answered a questionnaire to assess subjective perceptions of the orthoses. Results from 3D gait analysis provided evidence that CFSOs enhance gait function in most participants by improving ankle plantarflexion moment (p < 0.001), ankle positive work (p < 0.001), and stride length (p < 0.001). The CFSO did not suit all participants, which emphasizes the importance of analyzing each patient's needs.

  • 6.
    Bartonek, Asa
    et al.
    Karolinska Inst, Womens & Childrens Hlth, Motoriklab, Stockholm, Sweden..
    Lidbeck, Cecilia
    Karolinska Inst, Womens & Childrens Hlth, Stockholm, Sweden..
    Hellgren, Kerstin
    Karolinska Inst, Clin Neurosci, Stockholm, Sweden..
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Karolinska Inst, Womens & Childrens Hlth, Stockholm, Sweden..
    Head and Trunk Movements During Turning Gait in Children with Cerebral Palsy2019In: Journal of motor behavior, ISSN 0022-2895, E-ISSN 1940-1027, Vol. 51, no 4, p. 362-370Article in journal (Refereed)
    Abstract [en]

    Thirty children with cerebral palsy (CP) and 22 typical developing (TD) were tested with 3D-gait analysis. At turning, trunk rotation was larger in CP2 (GMFCS II) than in TD and CP1 (GMFCS I), and head flexion was larger in CP3 (GMFCS III) than TD. Maximum head and trunk flexion values during the entire trial were larger in CP3 than in the other groups, and trunk flexion was larger in CP2 than in TD. Trial time increased with GMFCS-level. Less trunk rotation than TD and CP1 reflects spatial insecurity in CP2, which in CP3 is compensated by the walker. The flexed head and trunk in CP3 and trunk in CP2 may reflect deficits in proprioception and sensation requiring visual control of the lower limbs.

  • 7. Bartonek, Asa
    et al.
    Lidbeck, Cecilia M.
    Pettersson, Robert
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Weidenhielm, Eva Brostrom
    Eriksson, Marie
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Influence of heel lifts during standing in children with motor disorders2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 3, p. 426-431Article in journal (Refereed)
    Abstract [en]

    Heel wedges may influence standing posture but how and to what extent are unknown. Thirty-two children with motor disorders - 16 with arthrogryposis multiplex congenita (AMC) and 16 with cerebral palsy (CP) - and 19 control children underwent a three-dimensional motion analysis. Unassisted standing during 20s with shoes only and with heel lifts of 10,20 and 30 mm heights was recorded in a randomized order. The more weight-bearing limb or the right limb was chosen for analysis. In both the AMC and CP groups, significant changes were seen between various heel lifts in ankle, knee and pelvis, and in the control group in the ankle only. Between orthosis and non-orthosis users significant differences were seen between different heel lift conditions in ankle, knee and trunk in the AMC group and in the ankle in the CP group. Pelvis position changed toward less anterior tilt with increasing heel height, but led to increasing knee flexion in most of the children, except for the AMC Non-Ort group. Children with AMC and CP represent different motor disorders, but the heel wedges had a similar influence on pelvis, hip and knee positions in all children with CP and in the AMC orthosis users. A challenge is to apply heel heights adequate to each individual's orthopaedic and neurologic conditions to improve biomechanical alignment with respect to all body segments.

  • 8.
    Bartonek, Åsa
    et al.
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Wang, Ruoli
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Eriksson, Marie
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Comparison of two carbon fibre spring orthoses' effect on gait in children with myelomeningocele2012In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219Article in journal (Refereed)
  • 9. Broström, Eva
    et al.
    Örtqvist, Maria
    Haglund-Åkerlind, Yvonne
    Hagelberg, Stefan
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Trunk and center of mass movements during gait in children with juvenile idiopathic arthritis2007In: Human Movement Science, ISSN 0167-9457, E-ISSN 1872-7646, Vol. 26, no 2, p. 296-305Article in journal (Refereed)
    Abstract [en]

    Motion of the body center of mass (CoM) can often indicate the overall effect of the strategy of forward progression used. In the present study, focus is placed on trunk movements in the sagittal, coronal, and transverse/rotation plane, as well as placement of the CoM, during gait in children with juvenile idiopathic arthritis (JIA). Seventeen children with JIA, all with polyarticular lower extremity involvement were examined before and approximately two weeks after treatment with intra-articular cortico-steroid injections. Movement was recorded with a 6-camera 3D motion analysis system in both the children with JIA and in 21 healthy controls. Trunk and center of mass movements were compared between JIA and controls, and effects of intra-articular cortico-steroid treatment were evaluated. Children with JIA were more posteriorly tilted in the trunk, contrary to the common clinical impression, and had their CoM placed more posterior and off-centred, which may have been a result of pain. With such knowledge, it might be possible to better understand the effects of their pain and involvement, and ultimately to plan a treatment strategy for improving their gait patterns.

  • 10.
    Dijkstra, Erik J.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH Engineering Sciences.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Sensitivity in prediction of human posture by constrained optimizationManuscript (preprint) (Other academic)
    Abstract [en]

    In a variety of activities of daily living, it is important to be able to stand still in one place. For persons with motion disorders, orthopaedic treatment, which changes geometric or biomechanical properties, can improve the individual's posture and walking ability. Such treatment requires insight into how posture and walking ability are affected. As this is very challenging to observe by the naked eye, engineering tools are increasingly employed to support clinical diagnostics and treatment planning. Because of their potential to help unravel the causal relation between treatment and its outcome, the number of predictive methods are increasing. This study addresses the complications in the creation and analysis of a posture prediction framework. The fmincon optimization function in MATLAB was used in conjunction with a musculoskeletal model in OpenSim. One clear local minimum was found in the form of a symmetric standing posture but perturbation analyses revealed the presence of many other postural congurations, each representing its own unique local minimum in the feasible parameter space. For human postural stance, this can translate to there being many different ways of standing without actually noticing a difference in the efforts required for these poses.

  • 11.
    Dijkstra, Erik J.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. Karolinska Institutet, Stockholm, Sweden.
    Computation of ground reaction force using Zero Moment Point2015In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 48, no 14, p. 3776-3781Article in journal (Refereed)
    Abstract [en]

    Motion analysis is a common clinical assessment and research tool that uses a camera system or motion sensors and force plates to collect kinematic and kinetic information of a subject performing an activity of interest. The use of force plates can be challenging and sometimes even impossible. Over the past decade, several computational methods have been developed that aim to preclude the use of force plates. Useful in particular for predictive simulations, where a new motion or change in control strategy inherently means different external contact loads. These methods, however, often depend on prior knowledge of common observed ground reaction force (GRF) patterns, are computationally expensive, or difficult to implement. In this study, we evaluated the use of the Zero Moment Point as a computationally inexpensive tool to obtain the GRFs for normal human gait. The method was applied on ten healthy subjects walking in a motion analysis laboratory and predicted GRFs are evaluated against the simultaneously measured force plate data. Apart from the antero-posterior forces, GRFs are well-predicted and errors fall within the error ranges from other published methods. Joint extension moments were underestimated at the ankle and hip but overestimated at the knee, attributable to the observed discrepancy in the predicted application points of the GRFs. The computationally inexpensive method evaluated in this study can reasonably well predict the GRFs for normal human gait without using prior knowledge of common gait kinetics.

  • 12.
    Engström, Pähr
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Tedroff, Kristina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Orefelt, Christina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Haglund-Åkerlind, Yvonne
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    Department of Women’s and Children’s Health. Karolinska University Hospital, Sweden.
    Botulinum toxin A does not improve cast treatment for idiopathic toe-walking - a randomized controlled trial2013In: Journal of Bone and Joint Surgery. American volume, ISSN 0021-9355, E-ISSN 1535-1386, Vol. 95, no 5, p. 400-407Article in journal (Refereed)
    Abstract [en]

    Background: There are many treatments for idiopathic toe-walking, including casts with or without injection of botulinum toxin A. Combined treatment with casts and botulinum toxin A has become more common even though there have been few studies of its efficacy and safety problems. Our aims were to conduct a randomized controlled trial to test the hypotheses that combined treatment with casts and botulinum toxin A is more effective than casts alone in reducing toewalking by patients five to fifteen years of age, and that the treatment effect correlates with the extent of coexisting neuropsychiatric problems. Methods: All patients who had been consecutively admitted to the pediatric orthopaedics department of our institution because of idiopathic toe-walking between November 2005 and April 2010 were considered for inclusion in the study. Forty-seven children constituted the study population. The children were randomized to undergo four weeks of treatment with below-the-knee casts either as the sole intervention or to undergo the cast treatment one to two weeks after receiving injections of botulinum toxin A into the calves. Before treatment and three and twelve months after cast removal, all children underwent three-dimensional (3-D) gait analysis. The severity of the idiopathic toe-walking was classified on the basis of the gait analysis, and the parents rated the time that their child spent on his/her toes during barefoot walking. Passive hip, knee, and ankle motion as well as ankle dorsiflexor strength were measured. Before treatment, all children were evaluated with a screening questionnaire for neuropsychiatric problems. Results: No differences were found in any outcome parameter between the groups before treatment or at three or twelve months after cast removal. Several gait-analysis parameters, passive ankle motion, and ankle dorsiflexor strength were improved at both three and twelve months in both groups, even though many children still demonstrated some degree of toe-walking. The treatment outcomes were not correlated with coexisting neuropsychiatric problems. Conclusion: Adding botulinum toxin-A injections prior to cast treatment for idiopathic toe-walking does not improve the outcome of cast-only treatment. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

  • 13.
    Engström, Pähr
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Tedroff, Kristina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Orefelt, Christina
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Haglund-Åkerlind, Yvonne
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Does Botulinum toxin A improve the walking pattern in children with idiopathic toe-walking?2010In: Journal of Children's Orthopaedics, ISSN 1863-2521, Vol. 4, no 4, p. 301-308Article in journal (Refereed)
    Abstract [en]

    Background: Numerous recommendations have been made for treating idiopathic toe-walking (ITW), but the treatment results have been questioned. The purpose of this study was to investigate whether botulinum toxin A (BTX) improves the walking pattern in ITW as examined with 3-D gait analysis. Participants and methods: A consecutive series of 15 children (aged 5-13 years) were enrolled in the study. The children underwent a 3-D gait analysis prior to treatment with a total of 6 units/kg bodyweight Botox® in the calf muscles and an exercise program. The gait analysis was repeated 3 weeks and 3, 6, and 12 months after treatment. A classification of toe-walking severity was made before treatment and after 12 months. The parents rated the perceived amount of toe-walking prior to treatment and 6 and 12 months after treatment. Results: Eleven children completed the 12-month follow-up. The gait analysis results displayed a significant improvement, indicating decreased plantarflexion angle at initial contact and during swing phase and increased dorsiflexion angle during midstance at all post-treatment testing instances. According to the parents' perception of toe-walking, 3/11 children followed for 12 months had ceased toe-walking completely, 4/11 decreased toe-walking, and 4/11 continued toe-walking. After 6-12 months, the toe-walking severity classification improved in 9 of the 14 children for whom data could be assessed. Conclusions: A single injection of BTX in combination with an exercise program can improve the walking pattern in children with ITW seen at gait analysis, but the obvious goal of ceasing toe-walking is only occasionally reached.

  • 14. Eriksson, Marie
    et al.
    Bartonek, Asa
    Ponten, Eva
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. Karolinska institutet, Sweden.
    Gait dynamics in the wide spectrum of children with arthrogryposis: a descriptive study2015In: BMC Musculoskeletal Disorders, ISSN 1471-2474, E-ISSN 1471-2474, Vol. 16Article in journal (Refereed)
    Abstract [en]

    Background: Arthrogryposis Multiplex Congenita (AMC) is a heterogeneous condition characterized by multiple joint contractures at birth. Greater movements in the trunk and pelvis during walking have been observed in children with AMC using orthoses compared to those wearing only shoes. This study investigated gait dynamics in children with AMC and identified compensatory mechanisms that accommodate walking. Methods: Twenty-six children with AMC who walked with orthoses or shoes and a control group consisting of 37 typically-developing children were evaluated in 3D gait analysis. Children with AMC were divided into subgroups based on which joints needed to be stabilized in the sagittal plane; AMC1 used knee-ankle-foot orthoses (KAFOs) with locked knee joints, AMC2 used KAFOs with open knee joints or ankle-foot orthoses, and AMC3 used shoes. Results: The Gait Deviation Index was lower in AMC groups than in the control group, with the lowest in AMC1. Excessive trunk movements in frontal and transverse planes were observed in AMC2 and especially in AMC1. Lower hip flexion moment was found in AMC1, while AMC2 and AMC3 showed similar hip flexion moments as the control group. Knee extension moments were similar between the groups. In the frontal plane there were only small differences between the groups in hip abduction moment. A joint work analysis indicated greater contribution from the hip muscles to overall positive work in AMC groups, particularly in AMC1, than in the control group. Conclusion: All AMC groups showed less hip extension than the control group, but hip flexion moment was significantly lower only in AMC1, which can be attributed to their gait strategy with bilateral locked KAFOs. AMC1, who had weak knee extensors, were helped by their locked KAFOs and therefore showed similar knee extension moment as the other groups. This finding, together with their gait patterns, demonstrates the children's high reliance on hip muscles and presumably trunk muscles to provide propulsion. Our study shows that with adequate orthotic support, children with AMC and even with severe weakness and contractures can achieve walking.

  • 15.
    Eriksson, Marie
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics. Karolinska Institutet.
    Broström, Eva
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Gait pattern in children with arthrogryposis multiplex congenita2010In: Journal of Children's Orthopaedics, ISSN 1863-2521, E-ISSN 1863-2548, Vol. 4, no 1, p. 21-31Article in journal (Refereed)
    Abstract [en]

    Purpose: Lower limb contractures and muscle weakness are common in children with arthrogryposis multiplex congenita (AMC). To enhance or facilitate ambulation, orthoses may be used. The aim of this study was to describe gait pattern among individuals wearing their habitual orthotic devices. Methods: Fifteen children with AMC, mean age 12. 4 (4. 3) years, with some lower limb involvement underwent 3-D gait analysis. Three groups were defined based on orthosis use; Group 1 used knee-ankle-foot orthoses with locked knee joints, Group 2 used ankle-foot orthoses or knee-ankle-foot orthoses with open knee joints and Group 3 used no orthoses. Results: The greatest trunk and pelvis movements in all planes and the greatest hip abduction were observed in Group 1, compared to Groups 2 and 3, as well as to the gait laboratory control group. Maximum hip extension was similar in Groups 1 and 2, but in Group 3, there was less hip extension and large deviations from the control data. Lower cadence and walking speed were observed in Group 1 than in Groups 2 and 3. The step length was similar in all groups and also with respect to the gait laboratory reference values. Conclusions: Children with AMC were subdivided according to orthoses use. Kinematic data as recorded with 3-D gait analysis showed differences among the groups in trunk, pelvis and knee kinematics, and in cadence and walking speed. The step length was similar in all groups and to the gait laboratory reference values, which may be attributable to good hip extension strength in all participants.

  • 16.
    Farewik, Lanie
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. University of Michigan, Department of Mechanical Engineering, Division of Biomechanics.
    Mild diabetic neuropathy affects ankle motor function2001In: Clinical Biomechanics, ISSN 0268-0033, E-ISSN 1879-1271, Vol. 16, no 6, p. 522-528Article in journal (Refereed)
    Abstract [en]

    Objective. To evaluate the effect of age and diabetic neuropathy on ankle motor function in the frontal plane in terms of rate of torque development and capability for balance recovery.

    Design. Case control study. Six older women with diabetic neuropathy compared to six women without neuropathy, matched for age and presence of diabetes mellitus; and nine healthy young women.

    Background. Neuropathy causes a distal impairment in lower extremity sensory function which increases fall risk. Impairments in ankle inversion/eversion proprioceptive thresholds have been identified, but the effect of neuropathy on ankle motor strength in the frontal plane is unknown.

    Methods. Subjects' abilities to recover from a lateral lean (with center of gravity offset as percentage of foot width) while standing on one foot, and to rapidly generate inversion torque about the ankle, were quantified.

    Results. All nine of the young, but only one of six older, control subjects recovered from a 10% lean (P=0.0052). Three of six older controls, but no neuropathy subject, recovered from a 5% lean (P=0.083). Neuropathy subjects demonstrated half the ankle rate of torque development [78.2 (50.8) N m/s; P=0.016] of the young and older controls [162.0 (54.6) and 152.7 (22.2) N m/s, respectively].

    Conclusions. Diabetic neuropathy leads to a decrease in rapidly available ankle strength which impairs balance recovery among older women. Younger women demonstrate similar ankle strength but superior balance recovery compared to older women without neuropathy.Relevance

    Older women with diabetic neuropathy and normal ankle strength, as judged by clinical muscle testing, demonstrate a sub-clinical impairment in ankle motor function suggesting a target for intervention.

  • 17.
    Gutierrez, A.
    et al.
    Universidad de Los Andes, Colombia; Univ. de Toulouse, Univ. Paul Sabatier, France.
    Chamorro, H.R.
    KTH, School of Electrical Engineering (EES), Electric Power and Energy Systems.
    Villa, L. F. L.
    Jimenez, J. F.
    Alonso, C.
    SysML Methodology for HIL Implementation of PV Models2015In: 2015 17TH EUROPEAN CONFERENCE ON POWER ELECTRONICS AND APPLICATIONS (EPE'15 ECCE-EUROPE), IEEE , 2015Conference paper (Refereed)
    Abstract [en]

    This paper describes a methodology for implementing in FPGA models of photovoltaic panels for Hardware-in-the-Loop (HIL) and real-time simulations. The proposed methodology integrates numerical solutions, SysML diagrams and Petri nets for structural design and formal validation. In this study, photovoltaic cells have been modeled using the single diode circuit. The photovoltaic panel model is solved by the Newton-Raphson method, and the Lagrange remainder is employed to limit the iteration number. Results show suitable accuracy and performance of the proposed methodology.

  • 18.
    Gutierrez, Elena
    Karolinska Institutet.
    Kinetics of compensatory gait in persons with myelomeningocele2005In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 21, no 1, p. 12-23Article in journal (Refereed)
    Abstract [en]

    This study investigated the kinetic strategy and compensatory mechanisms during self-ambulatory gait in children with lumbo-sacral myelomeningocele. Thirty-one children with mid-lumbar to low-sacral myelomeningocele who walked without aids and 21 control children were evaluated by three-dimensional gait analysis. Joint moments in all planes at the hip and knee and sagittal moments at the ankle, as well as joint power and work done at all three joints, were analyzed. Joint moment capacity lost due to plantarflexor and dorsiflexor weakness was provided instead by orthotic support, but other joints were loaded more to compensate for the weakness at the ankles and restricted ankle motion. Subjects with total plantarflexor and dorsiflexor paresis and strength in the hip abductors had more knee extensor loading due to plantarflexor weakness and dorsiflexion angle of the orthotic ankle joint. The subjects with orthoses also generated more power at the hip to supplement the power generation lost to plantarflexor weakness and fixed ankles. The most determinant muscle whose paresis changes gait kinetics was the hip abductor. Hip abductor weakness resulted in a characteristic pattern where the hips displayed an eccentric adduction moment, mediating energy transfer into the lower limbs, and the hips replaced the knees as power absorbers in early stance. Joint moment, power and work analyses complement a kinematic analysis to provide a complete picture of how children who have muscle paresis recruit stronger muscle groups to compensate for weaker ones.

  • 19.
    Gutierrez, Elena
    et al.
    Chalmers University of Technology, Crash Safety Division.
    Huang, Yinglai
    Department of Anatomy and Cell Biology, Göteborg University.
    Haglid, Kenneth
    Department of Anatomy and Cell Biology, Göteborg University.
    Bao, Feng
    Department of Anatomy and Cell Biology, Göteborg University.
    Hansson, Hans-Arne
    Department of Anatomy and Cell Biology, Göteborg University.
    Hamberger, Anders
    Department of Anatomy and Cell Biology, Göteborg University.
    Viano, David
    Crash Safety Division, Chalmers University of Technology.
    A New Model for Diffuse Brain Injury by Rotational Acceleration: I. Model, Gross Appearance, and Astrocytosis2001In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 18, no 3, p. 247-257Article in journal (Refereed)
  • 20.
    Gutierrez, Elena M
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. Chalmers University of Technology.
    A new model for diffuse brain injury by rotational acceleration: I model, gross appearance, and astrocytosis2001In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 18, no 3, p. 247-257Article in journal (Refereed)
    Abstract [en]

    Rapid head rotation is a major cause of brain damage in automobile crashes and falls. This report details a new model for rotational acceleration about the center of mass of the rabbit head. This allows the study of brain injury without translational acceleration of the head. Impact from a pneumatic cylinder was transferred to the skull surface to cause a half-sine peak acceleration of 2.1 × 105 rad/s2 and 0.96-ms pulse duration. Extensive subarachnoid hemorrhages and small focal bleedings were observed in the brain tissue. A pronounced reactive astrogliosis was found 8-14 days after trauma, both as networks around the focal hemorrhages and more diffusely in several brain regions. Astrocytosis was prominent in the gray matter of the cerebral cortex, layers II-V, and in the granule cell layer and around the axons of the pyramidal neurons in the hippocampus. The nuclei of cranial nerves, such as the hypoglossal and facial nerves, also showed intense astrocytosis. The new model allows study of brain injuries from head rotation in the absence of translational influences.

  • 21.
    Gutierrez, Elena M
    et al.
    Karolinska Institutet, Dept. of Surgical Sciences, Orthopedics Section.
    Bartonek, Åsa
    Karolinska Institutet, Dept. of Women's and Child's Health.
    Haglund-Åkerlind, Yvonne
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Saraste, Helena
    Karolinska Institutet, Dept. of Surgical Sciences, Orthopedics Section.
    Kinetics of compensatory gait in persons with myelomeningocele2005In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 21, no 1, p. 12-23Article in journal (Refereed)
    Abstract [en]

    This study investigated the kinetic strategy and compensatory mechanisms during self-ambulatory gait in children with lumbo-sacral myelomeningocele. Thirty-one children with mid-lumbar to low-sacral myelomeningocele who walked without aids and 21 control children were evaluated by three-dimensional gait analysis. Joint moments in all planes at the hip and knee and sagittal moments at the ankle, as well as joint power and work done at all three joints, were analyzed. Joint moment capacity lost due to plantarflexor and dorsiflexor weakness was provided instead by orthotic support, but other joints were loaded more to compensate for the weakness at the ankles and restricted ankle motion. Subjects with total plantarflexor and dorsiflexor paresis and strength in the hip abductors had more knee extensor loading due to plantarflexor weakness and dorsiflexion angle of the orthotic, ankle joint. The subjects with orthoses also generated more power at the hip to supplement the power generation lost to plantarflexor weakness and fixed ankles. The most determinant muscle whose paresis changes gait kinetics was the hip abductor. Hip abductor weakness resulted in a characteristic pattern where the hips displayed an eccentric adduction moment, mediating energy transfer into the lower limbs, and the hips replaced the knees as power absorbers in early stance. Joint moment, power and work analyses complement a kinematic analysis to provide a complete picture of how children who have muscle paresis recruit stronger muscle groups to compensate for weaker ones.

  • 22.
    Gutierrez, Elena M
    et al.
    Dept. of Mechanical Engineering, Division of Biomechanics, University of Michigan.
    Helber, Matther
    Dept. of Mechanical Engineering, Division of Biomechanics, University of Michigan.
    Dealva, Denise
    Dept. of Physical Medicine and Rehabilitation, University of Michigan.
    Ashton-Miller, James
    Dept. of Mechanical Engineering, Division of Biomechanics, University of Michigan.
    Richardson, James
    Dept. of Physical Medicine and Rehabilitation, University of Michigan.
    Mild diabetic neuropathy affects ankle motor function2001In: Clinical Biomechanics, ISSN 0268-0033, E-ISSN 1879-1271, Vol. 16, no 6, p. 522-528Article in journal (Refereed)
  • 23.
    Gutierrez Farewik, Elena M
    Chalmers University of Technology, Crash Safety Division.
    A new model for diffuse brain injury by rotational acceleration: II. Effects on extracellular glutamate, intracranial pressure, and neuronal apoptosis2001In: Journal of Neurotrauma, ISSN 0897-7151, Vol. 18, no 3, p. 259-73Article in journal (Refereed)
    Abstract [en]

    The aim of this study is to monitor excitatory amino acids (EAAs) in the extracellular fluids of the brain and to characterize regional neuronaldamage in a new experimental model for brain injury, in which rabbits were exposed to 180-260 krad/s2 rotational head acceleration. This loading causes extensive subarachnoid hemorrhage, focal tissue bleeding, reactive astrocytosis, and axonal damage. Animals were monitored for intracranial pressure (ICP) and for amino acids in the extracellular fluids. Immunohistochemistry was used to study expression of the gene c-Jun and apoptosis with the terminal deoxynucleotidyl transferase nick-end labeling (TUNEL) technique. Extracellular glutamate, glycine, and taurine increased significantly in the hippocampus within a few hours and remained high after 24 h. Neuronal nuclei in the granule layers of the hippocampus and cerebellum were positive for c-Jun after 24 h. Little immunoreactivity was detected in the cerebral cortex. c-Jun-positive neuronal perikarya and processes were found in granule and pyramidal CA4 layers of the hippocampus and among the Purkinje cells of the cerebellum. Also some microglial cells stained positively for c-Jun. TUNEL reactivity was most intense at 10 days after trauma and was extensive in neurons of the cerebral cortex, hippocampus, and cerebellum. The initial response of the brain after rotationalhead injury involves brain edema after 24 h and an excitotoxic neuronal microenvironment in the first hour, which leads to extensive delayed neuronal cell death by apoptosis necrosis in the cerebral cortex, hippocampus and cerebellum.

  • 24. Gutierrez-Farewik, Elena M.
    et al.
    Alm, M.
    Hultling, C.
    Saraste, H.
    Measuring seating pressure, area, and asymmetry in persons with spinal cord injury2004In: European spine journal, ISSN 0940-6719, E-ISSN 1432-0932, Vol. 13, no 4, p. 374-379Article in journal (Refereed)
    Abstract [en]

    The goal of this study was to measure characteristics of seat loading in manual wheelchair users with complete spinal cord injury (SCI). Pressure distribution on the seating area of 25 adult males with SCI and eight non-injured adult males was measured in a relaxed and an upright posture on a standardized hard surface. Subjects with SCI were also tested in their wheelchairs. Maximum pressure, contact area, area of the highest pressure, and three asymmetry indices were compared. Subjects with SCI have higher pressure distributed over a smaller area, have a much smaller contact area, and distribute the loading more asymmetrically than non-injured subjects. Upright posture only corrects for some loading problems, while the wheelchair corrects for more loading parameters. Routine clinical seat loading evaluation may lead to improved chair and cushion selection for patients with SCI and may even alert clinicians to patients at high risk for complications due to high or unbalanced loads.

  • 25. Gutierrez-Farewik, Elena M.
    et al.
    Bartonek, A.
    Haglund-Akerlind, Y.
    Saraste, H.
    Centre of mass motion during gait in persons with myelomeningocele2003In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 18, no 2, p. 37-46Article in journal (Refereed)
    Abstract [en]

    The movement of the centre of mass in the vertical and lateral directions during gait in children with myelomeningocele was analyzed. The children were classified into five groups depending on the successive paresis of lower limb muscle groups and compared to a control group. In the groups with. dorsi- and plantarflexor weakness, the excursions increased and an anterior trend in the centre of mass was observed. In the groups with additional abductor paresis, the lateral excursion was highest and the vertical excursion low due to increased transverse and frontal motion and reduced sagittal motion. With further paresis of the hip extensors, the centre of mass was more posteriorly positioned due to compensatory trunk extension. Improved understanding of individual children's solutions to their muscle paresis can be obtained by visualizing the centre of mass relative to the pelvis. Centre of mass analyses in myelomeningocele offer an important complement to standard gait analysis.

  • 26. Gutierrez-Farewik, Elena M.
    et al.
    Bartonek, A.
    Haglund-Akerlind, Y.
    Saraste, H.
    Characteristic gait kinematics in persons with lumbosacral myelomeningocele2003In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 18, no 3, p. 170-177Article in journal (Refereed)
    Abstract [en]

    Thirty self-ambulatory children with mid-lumbar to low-sacral myelomeningocele who walked without aids and 21 control children were evaluated by three-dimensional gait analysis. Characteristic kinematic patterns and parameters in the trunk, pelvis, hip, knee and ankle were analyzed with respect to groups with successive weakness of the ankle plantarflexor, ankle dorsiflexor, hip abductor, hip extensor and knee flexor muscles. Extensive weakness of the plantarflexors resulted in kinematic alterations in the trunk, pelvis, hip and knee and in all three planes seen as knee flexion, anterior pelvic tilt and trunk and pelvic rotation. Additional extensive weakness of the dorsiflexors made little difference in the walking strategy. Large kinematic alterations in all planes were observed where there was a large extent of additional weakness of the hip abductor but strength remaining in the hip extensors. In this group, gait was characterized by large lateral sway of the trunk, rotation of the trunk and pelvis, pelvic hike and increased extension of the knees. In the group with total poresis hip extensors but yet some knee flexion, gait was similar to the previous group but there was less sagittal plane movement greates and posterior trunk tilt. Gait analysis provides an understanding of the compensatory strategies employed in these patients. Clinical management can be directed towards stabilizing the lower extremities and accommodating large upper body motion to preserve this method of self-ambulation even in children who have considerable hip extensor and abductor weakness.

  • 27.
    Gutierrez-Farewik, Elena M.
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Bartonek, A.
    Saraste, H.
    Comparison and evaluation of two common methods to measure center of mass displacement in three dimensions during gait2006In: Human Movement Science, ISSN 0167-9457, E-ISSN 1872-7646, Vol. 25, no 2, p. 238-256Article in journal (Refereed)
    Abstract [en]

    Center of mass displacement during gait has frequently been used as an indicator of gait efficiency or as a complement to standard gait analysis. With technological advances, measuring the center of mass as the centroid of a multi-segment system is practical and feasible, but must first be compared to the well-established Newtonian computation of double-integrating the ground reaction force. This study aims to verify that the kinematic centroid obtained from a commonly-used model (Vicon Peak (R) Plug-In-Gait) provides at least as reliable measurements of center of mass displacement as those obtained from the ground reaction forces. Gait data was collected for able-bodied children and children with myelomeningocele who use larger lateral center of mass excursions during gait. Reasonable agreement between methods was found in fore-aft and vertical directions, where the methods' excursions differed by an average of less than 10 mm in either direction, and the average RMS differences between methods' computed curves were 6 and 13 mm. Particularly good agreement was observed in the lateral direction, where the calculated excursions differed by an average of less than 2 mm and the RMS difference was 5 mm. Error analyses in computing the center of mass displacement from ground reaction forces were performed. A 5% deviation in mass estimation increased the computed vertical excursion twofold, and a 5% deviation in the integration constant of initial velocity increased the computed fore-aft excursions by 10%. The suitability of calculating center of mass displacement using ground reaction forces in a patient population is questioned. The kinematic centroid is susceptible to errors in segment parameters and marker placement, but results in plausible results that are at least within the range of doubt of the better-established ground reaction force integration, and are more useful when interpreting 3-D gait data.

  • 28.
    Heintz, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Static optimization of muscle forces during gait in comparison to EMG-to-force processing approach2007In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 26, no 2, p. 279-288Article in journal (Refereed)
    Abstract [en]

    Individual muscle forces evaluated from experimental motion analysis may be useful in mathematical simulation, but require additional musculoskeletal and mathematical modelling. A numerical method of static optimization was used in this study to evaluate muscular forces during gait. The numerical algorithm used was built on the basis of traditional optimization techniques, i.e., constrained minimization technique using the Lagrange multiplier method to solve for constraints. Measuring exact muscle forces during gait analysis is not currently possible. The developed optimization method calculates optimal forces during gait, given a specific performance criterion, using kinematics and kinetics from gait analysis together with muscle architectural data. Experimental methods to validate mathematical methods to calculate forces are limited. Electromyography (EMG) is frequently used as a tool to determine muscle activation in experimental studies on human motion. A method of estimating force from the EMG signal, the EMG-to-force approach, was recently developed by Bogey et al. [Bogey RA, Perry J, Gitter AJ. An EMG-to-force processing approach for determining ankle muscle forcs during normal human gait. IEEE Trans Neural Syst Rehabil Eng 2005;13:302-10] and is based on normalization of activation during a maximum voluntary contraction to documented maximal muscle strength. This method was adapted in this study as a tool with which to compare static optimization during a gait cycle. Muscle forces from static optimization and from EMG-to-force muscle forces show reasonably good correlation in the plantarflexor and dorsiflexor muscles, but less correlation in the knee flexor and extensor muscles. Additional comparison of the mathematical muscle forces from static optimization to documented averaged EMG data reveals good overall correlation to patterns of evaluated muscular activation. This indicates that on an individual level, muscular force patterns from mathematical models can arguably be more accurate than from those obtained from surface EMG during gait, though magnitude must still be validated.

  • 29.
    Heintz, Sofia
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Evaluation of load-sharing and load capacity in force-limited muscle systems2006In: Computer Methods in Biomechanics and Biomedical Engineering, ISSN 1025-5842, E-ISSN 1476-8259Article in journal (Other academic)
    Abstract [en]

    This study had the objective to develop an algorithm for accurate force decomposition in a redundant musculoskeletal system. The hypothesis was that the calculated load-sharing is dependent on the optimality criterion adopted, but also on the magnitude of carried load. The developed algorithm emphasizes that several established optimization techniques can be unified, by identifying and separating the underlying optimization functions and the numerical methods to solve the resulting system. A numerically efficient and easily adaptable solution method is thereby created. In addition, individual capacity values are introduced for the muscles, allowing the evaluation of a magnitude-dependent load-sharing, and a load carrying capacity of the whole system. By modularizing the optimization method, the algorithm can be used as part of larger simulation systems. To illustrate the possibilities of the algorithm, a model of the upper limb is used in a set of demonstrative examples. The results from the examples show how the interactions between synergistic muscles is predicted in different configurations, and at different load levels.

  • 30.
    Karimi, Mohammad Taghi
    et al.
    Rehabilitation Sciences Research Center, Shiraz University of Medical Sciences, Shiraz, Iran.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    McGarry, Anthony
    Department of Biomedical Engineering, University of Strathclyde, Glasgow, United Kingdom.
    Evaluation of the hip joint contact force in subjects with Perthes based on OpenSIM2019In: Medical Engineering and Physics, ISSN 1350-4533, E-ISSN 1873-4030, Vol. 67, p. 44-48Article in journal (Refereed)
    Abstract [en]

    The head of femoral bone is deformed in the subjects with Leg Calve Perthes disease (LCPD). This may be due to the excessive loads applied on it. There are no studies that report the hip joint contact force in subjects with LCPD. Therefore, the aim of this study was to evaluate the hip joint contact force in subjects with Perthes disease. Ten typically-developing (TD) children and 10 children with LCPD were recruited in this study. The kinematics and kinetics of the subjects were evaluated in 3D motion analysis. The hip joint contact force was approximated using OpenSIM software. Differences were determined with an independent t-test. There was a significant difference between walking speed of TD and Perthes subjects (63.8 (±8.1) and 57.4 (±7.0) m/min, respectively). The first peak of hip joint contact force was 4.8 (±1.7) N/BW in Perthes subjects, compared to 7.6 (±2.5) N/BW in TD subjects (p = 0.004). The peak hip joint contact force in mediolateral and anteroposterior directions was significantly lower in Perthes subjects (p < 0.05). The hip joint excursion was 40.0 (±5.6) and 46.4 (±8.5) degrees in Perthes and normal subjects, respectively (p = 0.03). The hip joint contact forces were lower in the subjects with Perthes disease. Therefore, it can be concluded that the strategies used by LCPD subjects were successful to decrease hip joint contact force.

  • 31.
    Klets, Olesya
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Riad, Jacques
    Department of Orthopaedics, Skaraborg Hospital, Skövde, Sweden.
    Broström, Eva W.
    Karolinska Intitutet, Dept. of Women's and Children's Health, Stockholm, Sweden.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Comparison between a subject-specific and a scaled generic musculoskeletal model of the lower extremities in a subject with unilateral cerebral palsy2011In: Clinical Biomechanics, ISSN 0268-0033, E-ISSN 1879-1271Article in journal (Other academic)
    Abstract [en]

    The purpose of this paper was to develop methods to build a subject-specific musculoskeletal model of the lower extremities based on MRIs of a subject with unilateral CP, and to determine whether a scaled generic musculoskeletal model is accurate enough to characterize MTLs and MALs of 70 muscles in both lower limbs during gait in a subject with unilateral cerebral palsy. We found, that the generic models produced accurate values for changes in MTL during gait for almost all muscles, except adductor longus, adductor magnus, adductor brevis, quadratus femoris, pectineus, extensor digitorum longus, soleus, lateral gastrocnemius, and medial gastrocnemius. MALs computed from the scaled generic model, however, differed considerably from those computed from the subject-specific model. Upon comparison of hip, knee and ankle MALs in affected and non-affected sides of the lower extremities, the scaled generic model generally failed to identify level arm dysfunction in the subject with unilateral CP

  • 32.
    Klets, Olesya
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Riad, Jacques
    Department of Orthopaedics, Skaraborg Hospital, Skövde, Sweden.
    Broström, Eva W.
    Karolinska Institutet, Dept. of Women's and Children's Health, Stockholm, Sweden.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Moment-generating biomechanical factors of hip muscles in persons with unilateral with subject-specific models2012In: Journal of Applied Biomechanics, ISSN 1065-8483, E-ISSN 1543-2688Article in journal (Other academic)
  • 33.
    Kosterina, Natalia
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Wang, Ruoli
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Eriksson, Anders
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez Farewik, Lanie
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Force enhancement and force depression in a modified muscle model used for muscle activation prediction2013In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 23, no 4, p. 759-765Article in journal (Refereed)
    Abstract [en]

    This article introduces history-dependent effects in a skeletal muscle model applied to dynamic simulations of musculoskeletal system motion. Force depression and force enhancement induced by active muscle shortening and lengthening, respectively, represent muscle history effects. A muscle model depending on the preceding contractile events together with the current parameters was developed for OpenSim software, and applied in simulations of standing heel-raise and squat movements. Muscle activations were computed using joint kinematics and ground reaction forces recorded from the motion capture of seven individuals. In the muscle-actuated simulations, a modification was applied to the computed activation, and was compared to the measured electromyography data. For the studied movements, the history gives a small but visible effect to the muscular force trace, but some parameter values must be identified before the exact magnitude can be analysed. The muscle model modification improves the existing muscle models and gives a more accurate description of underlying forces and activations in musculoskeletal system movement simulations.

  • 34. Lidbeck, Cecilia
    et al.
    Bartonek, Åsa
    Yadav, Priti
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Tedroff, Kristina
    Åstrand, Per
    Hellgren, Kerstin
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. Karolinska Inst, Sweden.
    The role of visual stimuli on standing posture in children with bilateral cerebral palsy2016In: BMC Neurology, ISSN 1471-2377, E-ISSN 1471-2377, Vol. 16, no 1, article id 151Article in journal (Refereed)
    Abstract [en]

    Background: In children with bilateral cerebral palsy (CP) maintaining a standing position can be difficult. The fundamental motor task of standing independently is achieved by an interaction between the visual, somatosensory, and vestibular systems. In CP, the motor disorders are commonly accompanied by sensory and perceptual disturbances. Our aims were to examine the influence of visual stimuli on standing posture in relation to standing ability. Methods: Three dimensional motion analysis with surface electromyography was recorded to describe body position, body movement, and muscle activity during three standing tasks: in a self-selected position, while blindfolded, and during an attention-demanding task. Participants were twenty-seven typically-developing (TD) children and 36 children with bilateral CP, of which 17 required support for standing (CP-SwS) and 19 stood without support (CP-SwoS). Results: All children with CP stood with a more flexed body position than the TD children, even more pronounced in the children in CP-SwS. While blindfolded, the CP-SwS group further flexed their hips and knees, and increased muscle activity in knee extensors. In contrast, the children in CP-SwoS maintained the same body position but increased calf muscle activity. During the attention-demanding task, the children in CP-SwoS stood with more still head and knee positions and with less muscle activity. Conclusions: Visual input was important for children with CP to maintain a standing position. Without visual input the children who required support dropped into a further crouched position. The somatosensory and vestibular systems alone could not provide enough information about the body position in space without visual cues as a reference frame. In the children who stood without support, an intensified visual stimulus enhanced the ability to maintain a quiet standing position. It may be that impairments in the sensory systems are major contributors to the difficulties to stand erect in children with CP.

  • 35. Lidbeck, Cecilia M.
    et al.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Broström, Eva
    Karolinska Institutet, Stockholm, Sweden .
    Bartonek, Åsa
    Karolinska Institutet, Stockholm, Sweden .
    Postural Orientation During Standing in Children With Bilateral Cerebral Palsy2014In: Pediatric Physical Therapy, ISSN 0898-5669, E-ISSN 1538-005X, Vol. 26, no 2, p. 223-229Article in journal (Refereed)
    Abstract [en]

    Purpose: To investigate postural orientation and maintenance of joint position during standing in children with bilateral spastic cerebral palsy (BSCP). Methods: Standing was examined with 3-D motion analysis in 26 children with BSCP, and 19 children typically developing (TD). Two groups of children with cerebral palsy (CP) were analyzed: 15 who were able to maintain standing without support and 11 who needed support. Results: Children with CP stood with more flexion than children TD. In the CP groups, children standing without support stood more asymmetrically with less hip and knee flexion and less movement than those who required support. Conclusion: Children with CP had varying abilities to stand and maintain standing posture with or without support. Both CP groups stood with more flexion than their potential passive joint angle, more obvious in children requiring support. Investigations on how muscle strength and spatial perception influence posture remains to be explored.

  • 36. Löwing, K.
    et al.
    Thews, K.
    Haglund-Åkerlind, Y.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. Karolinska Institutet, Sweden.
    Effects of Botulinum Toxin-A and Goal-Directed Physiotherapy in Children with Cerebral Palsy GMFCS Levels I & II2017In: Physical & Occupational Therapy in Pediatrics, ISSN 0194-2638, E-ISSN 1541-3144, Vol. 37, no 3, p. 268-282Article in journal (Refereed)
    Abstract [en]

    Aims: To evaluate short and long-term effects of botulinum toxin-A combined with goal-directed physiotherapy in children with cerebral palsy (CP). Method: A consecutive selection of 40 children, ages 4–12 years, diagnosed with unilateral or bilateral CP, and classified in GMFCS levels I–II. During the 24 months, 9 children received one BoNT-A injection, 10 children two injections, 11 children three injections, and 10 children received four injections. 3D gait analysis, goal-attainment scaling, and body function assessments were performed before and at 3, 12, and 24 months after initial injections. Results: A significant but clinically small long-term improvement in gait was observed. Plantarflexor spasticity was reduced after three months and remained stable, while passive ankle dorsiflexion increased after 3 months but decreased slightly after 12 months. Goal-attainment gradually increased, reached the highest levels at 12 months, and levels were maintained at 24 months. Conclusion: The treatments’ positive effect on spasticity reduction was identified, but did not relate to improvement in gait or goal-attainment. No long-term positive change in passive ankle dorsiflexion was observed. Goal attainment was achieved in all except four children. The clinical significance of the improved gait is unclear. Further studies are recommended to identify predictors for positive treatment outcome.

  • 37. Murans, Girts
    et al.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Saraste, Helena
    Kinematic and kinetic analysis of static sitting of patients with neuropathic spine deformity2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 4, p. 533-538Article in journal (Refereed)
    Abstract [en]

    Wheelchair dependent children with neuropathic and neuromuscular diseases have up to 90% risk for progressive spine deformities. An unbalanced sitting can induce progression of spinal and pelvic deformities. Many current clinical assessment methods of sitting of such patients are semi-quantitative, or questionnaire-based. A 3D movement analysis offers quantitative and objective biomechanical analysis of sitting. The aim was to validate a method to describe quiet sitting and differences between patients and controls as well as to apply the methodology for pre- and post-operative comparison. The analysis was performed on 14 patients and 10 controls. Four patients were retested after spine surgery. Seat load asymmetry was up to 30% in the patient group comparing to maximum 7% in the control group. The asymmetric position of Ground Reaction Force vector between left and right sides was significant. Plumb line of cervical 7th vertebra over sacral 1st was different only in rotation. The location of Common Center of Pressure relative to inter-trochanteric midpoint was more anterior in controls than in patients. Pelvic inclination in patients was smaller, the obliquity and rotation was similar. There were no significant differences between patients and controls of the thorax position. Results with more changes in the seat-loading domain in comparison with posture indicate good postural control compensation of spinal deformity induced disequilibrium despite neuromuscular disease in the background. The comparison of the pelvic obliquity data from kinematics and X-ray showed good correlation. The four patients tested postoperatively improved after surgery.

  • 38. Nielsen, C.
    et al.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Hirschfeld, H.
    Saraste, H.
    Seat load characteristics in children with neuromuscular and syndrome-related scoliosis: effects of pathology and treatment2008In: Journal of pediatric orthopedics. Part B, ISSN 1060-152X, E-ISSN 1473-5865, Vol. 17, no 3, p. 139-144Article in journal (Refereed)
    Abstract [en]

    The amount of correction from spine deformity surgery that is required to avoid asymmetric and unbalanced sifting is not known, and methods sensitive enough to document moderate changes in pressure distribution over time are few, as the commonly used methods are qualitative or semiquantitative. The aim was to analyse seating pressure distribution with a pressure sensor mat system in patients with nonidiopathic scoliosis and to compare the pressure distribution with that in able-bodied controls. The aim was also to apply the method in a surgically treated scoliosis group before and after the spine fusion. Peak pressure, contact area of the entire and the maximum pressure surface, and three measures of asymmetry were calculated. Patients had higher peak pressure and more asymmetric loading than controls. Significant difference was indicated in contact area. After the spine fusion, all asymmetry indices improved. The method fulfilled clinical needs to detect the differences from normal controls as well as the surgery-dependent changes.

  • 39.
    Pettersson, Robert
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Bartonek, Å.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Posture strategies generated by constrained optimization2012In: Journal of Biomechanics, ISSN 0021-9290, E-ISSN 1873-2380, Vol. 45, no 3, p. 461-468Article in journal (Refereed)
    Abstract [en]

    For people with motion disorders, posture can impact fatigue, discomfort or deformities in the long term. Orthopedic treatments such as orthoses or orthopedic surgeries which change geometric properties can improve posture in these individuals. In this study, a model has been created to study posture strategies in such situations. A 3D mechanical model consisting of eight rigid segments and 30 muscle groups is used in which varying moment arms along the ranges of motion and biarticular muscles are considered. The method is based on static optimization, both to solve the load sharing in the muscle system and to choose posture strategy. The optimization computes the specific posture with minimal required effort (level of muscle activations), while fulfilling constraints containing subject specific ranges of motion, muscle strength/weakness and external support if present. Anthropometry and strength were scaled to each individual, based on reported pediatric anthropometry and strength values, combined with each individual's physical assessment. A control group of 10 able-bodied subjects as well as three subjects with motion disorders were studied, and simulated posture was compared with experimental data. The simulation showed reasonable to good agreement and ability to predict the effect of motion disorders and of external support. An example of application in parameter studies was also presented wherein ankle orthosis angles were varied. The model allows the user to study muscle activity at the muscle group level, position of center of mass and moments at joints in various situations.

  • 40.
    Rakesh, Krishnan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Univ Gavle, Dept Elect Math & Nat Sci, Gavle, Sweden..
    Bjorsell, Niclas
    Univ Gavle, Dept Elect Math & Nat Sci, Gavle, Sweden..
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    Smith, Christian
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL. KTH, School of Engineering Sciences (SCI), Centres, BioMEx.
    A survey of human shoulder functional kinematic representations2019In: Medical and Biological Engineering and Computing, ISSN 0140-0118, E-ISSN 1741-0444, Vol. 57, no 2, p. 339-367Article, review/survey (Refereed)
    Abstract [en]

    In this survey, we review the field of human shoulder functional kinematic representations. The central question of this review is to evaluate whether the current approaches in shoulder kinematics can meet the high-reliability computational challenge. This challenge is posed by applications such as robot-assisted rehabilitation. Currently, the role of kinematic representations in such applications has been mostly overlooked. Therefore, we have systematically searched and summarised the existing literature on shoulder kinematics. The shoulder is an important functional joint, and its large range of motion (ROM) poses several mathematical and practical challenges. Frequently, in kinematic analysis, the role of the shoulder articulation is approximated to a ball-and-socket joint. Following the high-reliability computational challenge, our review challenges this inappropriate use of reductionism. Therefore, we propose that this challenge could be met by kinematic representations, that are redundant, that use an active interpretation and that emphasise on functional understanding.

  • 41.
    Rakesh, Krishnan
    et al.
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL. Department of Electronics, Mathematics and Natural Sciences, University of Gävle, Gävle, Sweden.
    Cruciani, Silvia
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Björsell, Niclas
    Department of Electronics, Mathematics and Natural Sciences, University of Gävle, Gävle, Sweden.
    Smith, Christian
    KTH, School of Electrical Engineering and Computer Science (EECS), Robotics, perception and learning, RPL.
    Reliably Segmenting Motion Reversals of a Rigid-IMU Cluster Using Screw-Based Invariants2018Conference paper (Refereed)
    Abstract [en]

    Human-robot interaction (HRI) is movingtowards the human-robot synchronization challenge. Inrobots like exoskeletons, this challenge translates to thereliable motion segmentation problem using wearabledevices. Therefore, our paper explores the possibility ofsegmenting the motion reversals of a rigid-IMU clusterusing screw-based invariants. Moreover, we evaluate thereliability of this framework with regard to the sensorplacement, speed and type of motion. Overall, our resultsshow that the screw-based invariants can reliably segmentthe motion reversals of a rigid-IMU cluster.

  • 42.
    Riad, Jacques
    et al.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Modlesky, Christopher
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics. KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Broström, Eva W.
    Karolinska Institutet, Dept. of Women's and Children's Health.
    Are Muscle Volume Differences Related to Concentric Muscle Work During Walking in Spastic Hemiplegic Cerebral Palsy?2012In: Clinical Orthopaedics and Related Research, ISSN 0009-921X, E-ISSN 1528-1132, Vol. 470, no 5, p. 1278-1285Article in journal (Refereed)
    Abstract [en]

    Background: Individuals with spastic hemiplegic cerebral palsy are typically high functioning and walk without assistive devices. The involved limb is usually smaller and shorter, although it is not clear whether the difference in muscle volume has an impact on walking capacity. Questions/purposes: We determined the volume of muscles important for propulsion and related that volume to concentric muscle work during walking on the hemiplegic and noninvolved sides in patients with cerebral palsy. Patients and Methods: We studied 46 patients (mean age, 17.6 years; range, 13-24 years) with spastic hemiplegic cerebral palsy. We assessed muscle volume using MRI and concentric muscle work in the sagittal plane from the hip, knee, and ankle using three-dimensional gait analysis. Patients were classified by Winters' criteria to assess the involvement of cerebral palsy and movement pattern during walking. Results: On the hemiplegic side, muscles were smaller, except for the gracilis muscle, and concentric muscle work from the ankle plantar flexors, knee extensors, and hip flexors and extensors was lower compared to the noninvolved side. Hip extensor work was higher on the hemiplegic and the noninvolved sides compared to a control group of 14 subjects without cerebral palsy. Hemiplegic to noninvolved volume ratios correlated with work ratios (r = 0.40-0.66). The Winters classification and previous calf muscle surgery predicted work ratios. Conclusions: Our observations of smaller muscles on the hemiplegic side and changes in muscle work on both sides can help us distinguish between primary deviations that may potentially be treatable and compensatory mechanisms that should not be treated.

  • 43.
    Runnerstam, Magnus
    et al.
    Department of Neurosurgery, Sahlgrenska University Hospital.
    Bao, Feng
    Department of Anatomy and Cell Biology, Göteborg University.
    Huang, Yinglai
    Department of Anatomy and Cell Biology, Göteborg University.
    Shi, Jingshan
    Department of Anatomy and Cell Biology, Göteborg Universit.
    Gutierrez, Elena
    Chalmers University of Technology, Crash Safety Division.
    Hamberger, Anders
    Department of Anatomy and Cell Biology, Göteborg University.
    Hansson, Hans-Arne
    Department of Anatomy and Cell Biology, Göteborg University.
    Viano, David
    Crash Safety Division, Chalmers University of Technology.
    Haglid, Kenneth
    Department of Anatomy and Cell Biology, Göteborg University.
    A New Model for Diffuse Brain Injury by Rotational Acceleration: II. Effects on Extracellular Glutamate, Intracranial Pressure, and Neuronal Apoptosis2001In: Journal of Neurotrauma, ISSN 0897-7151, E-ISSN 1557-9042, Vol. 18, no 3, p. 259-273Article in journal (Refereed)
  • 44.
    Sandamas, Paul
    et al.
    Swedish Sch Sport & Hlth Sci, GIH, Lidingovagen 1, S-11433 Stockholm, Sweden..
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics. KTH, School of Engineering Sciences (SCI), Centres, BioMEx. Karolinska Inst, Stockholm, Sweden..
    Arndt, Anton
    Swedish Sch Sport & Hlth Sci, GIH, Lidingovagen 1, S-11433 Stockholm, Sweden.;Karolinska Inst, Stockholm, Sweden..
    The effect of a reduced first step width on starting block and first stance power and impulses during an athletic sprint start2019In: Journal of Sports Sciences, ISSN 0264-0414, E-ISSN 1466-447X, Vol. 37, no 9, p. 1046-1054Article in journal (Refereed)
    Abstract [en]

    This study investigated how manipulating first step width affects 3D external force production, centre of mass (CoM) motion and performance in athletic sprinting. Eight male and 2 female competitive sprinters (100m PB: 11.03 +/- 0.36 s male and 11.6 +/- 0.45 s female) performed 10 maximal effort block starts. External force and three-dimensional kinematics were recorded in both the block and first stance phases. Five trials were performed with the athletes performing their preferred technique (Skating) and five trials with the athletes running inside a 0.3 m lane (Narrow). By reducing step width from a mean of 0.31 +/- 0.06 m (Skating) to 0.19 +/- 0.03 m (Narrow), reductions were found between the two styles in medial block and medial 1st stance impulses, 1st stance anterior toe-off velocity and mediolateral motion of the CoM. No differences were found in block time, step length, stance time, average net resultant force vector, net anteroposterior impulse nor normalised external power. Step width correlated positively with medial impulse but not with braking nor net anteroposterior impulse. Despite less medially directed forces and less mediolateral motion of the CoM in the Narrow trials, no immediate improvement to performance was found by restricting step width.

  • 45. Tedroff, K.
    et al.
    Lowing, K.
    Haglund-Akerlind, Y.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Forssberg, H.
    Botulinumtoxin A treatment in toddlers with cerebral palsy2010In: Acta Paediatrica, ISSN 0803-5253, E-ISSN 1651-2227, Vol. 99, no 8, p. 1156-1162Article in journal (Refereed)
    Abstract [en]

    Aims: In this study the aim was to evaluate the effect of botulinum toxin A (BoNT-A) treatment on muscle tone, contracture development and gait pattern in young children with cerebral palsy (CP). Method: Fifteen children with spastic CP (mean age = 16 months) were included in a randomized control study. All received a daily stretching programme and children in the BoNT-A group additionally received two injections, 6 months apart in the gastrocnemius muscle. Outcomes were assessed at baseline, and after 1 and 3.5 years. A 3D gait-analysis was performed at 5 years of age. Results: Plantarflexor muscle tone in the BoNT-A group was significantly reduced after 3.5 years, while the muscle tone at the ankle and knee in the control group remained unchanged. The change-score in knee-flexion muscle tone between the groups was significantly different after 3.5 years. The knee joint ROM was significantly increased at 1 year in the BoNT-A group but reduced at the knee and ankle joints in the control group after 3.5 years. No group differences were found for gait analysis, GMFM-66 or PEDI. Conclusion: Early treatment of BoNT-A in children with spastic CP may decrease muscle tone and decelerate contracture development after 3.5 years. The effect on gait development remains inconclusive.

  • 46.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Broström, Eva
    Women's and Children's Health, Karolinska Institutet.
    Esbjörnsson, Anna-Clara
    Women's and Children's Health, Karolinska Institutet.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Analytical decomposition can help to interpret ankle joint moment-angle relationship2012In: Journal of Electromyography & Kinesiology, ISSN 1050-6411, E-ISSN 1873-5711, Vol. 22, no 4, p. 566-574Article in journal (Refereed)
    Abstract [en]

    Moment-angle relationship (dynamic joint stiffness) - the relationship between changes in joint moment and changes in joint angle - is useful for demonstrating interaction of kinematics and kinetics during gait. However, the individual contributors of dynamic joint stiffness are not well studied and understood, which has thus far limited its clinical application. In this study, ankle dynamic joint stiffness was analyzed and decomposed into three components in thirty able-bodied children during the stance phase of the gait. To verify the accuracy of the decomposition, the sum of decomposed components was compared to stiffness computed from experimental data, and good to very good agreement was found. Component 1, the term associated with changes in ground reaction force moment, was the dominant contribution to ankle dynamic joint stiffness. Retrospective data from eight children with juvenile idiopathic arthritis and idiopathic toe-walking was examined to explore the potential utility of analytical decomposition in pathological gait. Compared to controls, component 1 was the source of highest deviation in both pathological groups. Specifically, ankle dynamic joint stiffness differences can be further identified via two sub-components of component 1 which are based on magnitudes and rates of change of the ground reaction force and of its moment arm, and differences between the two patient groups and controls were most evident and interpretable here. Findings of the current study indicate that analytical decomposition can help identify the individual contributors to joint stiffness and clarify the sources of differences in patient groups.

  • 47.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    The effect of subtalar inversion/eversion on the dynamic function of the tibialis anterior, soleus, and gastrocnemius during the stance phase of gait2011In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 34, no 1, p. 29-35Article in journal (Refereed)
    Abstract [en]

    The purpose of this study was to determine how gait deviation in one plane (i.e. excessive subtalar inversion/eversion) can affect the dynamic function of the tibialis anterior, gastrocnemius, and soleus to accelerate the subtalar, ankle, knee and hip joints, as well as the body center of mass. Induced acceleration analysis was performed based on a subject-specific three-dimensional linkage model configured by stance phase gait data and driven by one unit of muscle force. Eight healthy adult subjects were examined in gait analysis. The subtalar inversion/eversion was modeled by offsetting up to 20 from the normal subtalar angle while other configurations remained unaltered. This study showed that the gastrocnemius, soleus and tibialis anterior generally functioned as their anatomical definition in normal gait, but counterintuitive function was occasionally found in the bi-articular gastrocnemius. The plantarflexors play important roles in the body support and forward progression. Excessive subtalar eversion was found to enlarge the plantarflexors and tibialis anterior's function. Induced acceleration analysis demonstrated its ability to isolate the contributions of individual muscle to a given factor, and as a means of studying effect of pathological gait on the dynamic muscle functions.

  • 48.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Gutierrez-Farewik, Elena
    KTH, School of Engineering Sciences (SCI), Mechanics, Structural Mechanics.
    Compensatory strategies in response to excessive muscle co-contraction at the ankle joint during walkingManuscript (preprint) (Other academic)
  • 49.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics, Biomechanics.
    Compensatory strategies during walking in response to excessive muscle co-contraction at the ankle joint2014In: Gait & Posture, ISSN 0966-6362, E-ISSN 1879-2219, Vol. 39, no 3, p. 926-932Article in journal (Refereed)
    Abstract [en]

    Excessive co-contraction causes inefficient or abnormal movement in several neuromuscular pathologies. How synergistic muscles spanning the ankle, knee and hip adapt to co-contraction of ankle muscles is not well understood. This study aimed to identify the compensation strategies required to retain normal walking with excessive antagonistic ankle muscle co-contraction. Muscle-actuated simulations of normal walking were performed to quantify compensatory mechanisms of ankle and knee muscles during stance in the presence of normal, medium and high levels of co-contraction of antagonistic pairs gastrocnemius + tibialis anterior and soleus + tibialis anterior. The study showed that if co-contraction increases, the synergistic ankle muscles can compensate; with gastrocmemius + tibialis anterior co-contraction, the soleus will increase its contribution to ankle plantarflexion acceleration. At the knee, however, almost all muscles spanning the knee and hip are involved in compensation. We also found that ankle and knee muscles alone can provide sufficient compensation at the ankle joint, but hip muscles must be involved to generate sufficient knee moment. Our findings imply that subjects with a rather high level of dorsiflexor + plantarflexor co-contraction can still perform normal walking. This also suggests that capacity of other lower limb muscles to compensate is important to retain normal walking in co-contracted persons. The compensatory mechanisms can be useful in clinical interpretation of motion analyses, when secondary muscle co-contraction or other deficits may present simultaneously in subjects with motion disorders.

  • 50.
    Wang, Ruoli
    et al.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    Gutierrez-Farewik, Elena M.
    KTH, School of Engineering Sciences (SCI), Mechanics.
    The effect of excessive subtalar inversion/eversion on the dynamic function of the soleus and gastrocnemius during the stance phase2009In: Proceedings of the ASME Summer Bioengineering Conference 2009, SBC2009, New York: AMER SOC MECHANICAL ENGINEERS , 2009, p. 1035-1036Conference paper (Refereed)
12 1 - 50 of 57
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