Mats Djupsjöbacka

Högskolan i Gävle, Gäfle, Gävleborg, Sweden

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Publications (47)92.55 Total impact

  • Ann-Katrin Stensdotter, Joakim Bjerke, Mats Djupsjöbacka
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    ABSTRACT: To investigate whether total knee arthroplasty (TKA) was associated with stability in single-limb stance and whether reduced stability in single-limb stance was associated with increased postural sway in bilateral quiet standing.
    Gait & Posture. 02/2015;
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    ABSTRACT: Objective: To evaluate the effect of neck coordination exercise on sensorimotor function in women with neck pain compared with best-available treatment and sham treatment. Design: Observer-blinded randomized controlled trial with short-term and 6-month follow-ups. Subjects: Women with chronic non-specific neck pain were randomized to 3 groups: neck coordination exercise with a novel training device; strength training for the neck and shoulders; or massage. Each group had 36 participants. Methods: The intervention period was 11 weeks with 22 individually supervised sessions. Primary outcomes were postural sway measures and precision of goal-directed arm movements. Secondary outcomes were range of motion for the neck, peak speed of axial rotation, and neck pain. A repeated measures multivariate analysis of variance (MANOVA) was conducted separately on the primary outcomes for the short-term and 6-month evaluations and on the sensorimotor secondary outcomes for the 6-month effect. The 6-month effect on pain was analysed with a repeated measures analysis of variance (ANOVA). Results: No significant treatment effects in favour of neck coordination exercise were found for short-term or 6-month evaluations. Conclusion: Neck coordination exercise is no better than strength training and massage in improving sensorimotor function. Further research should investigate the use of cut-offs for sensorimotor dysfunctions prior to proprioceptive or coordinative training.
    Journal of Rehabilitation Medicine 09/2014; · 1.90 Impact Factor
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    ABSTRACT: There is evidence that patients with psychotic conditions display greater center of pressure (CoP) displacement during quite standing than healthy subjects, but the underlying impairments in the control mechanisms are uncertain. The aim of this study was to identify the nature of possible impairments in the control of posture by modulation of visual and kinesthetic information during quiet standing. Center of pressure (CoP) data and whole-body kinematics of the center of mass (CoM) were recorded during quite standing on a firm surface with eyes open and with eyes closed, and standing with eyes open on a yielding surface. During all three conditions, patients displayed greater migration of CoM and CoP-CoM, a measure related to ankle joint torque, whereas CoP-frequency (MPF) was similar in patients and healthy subjects. Our results suggested that greater postural sway in patients may depend on disproportionally large ankle joint torque without corresponding increase in frequency. Furthermore, interactions between groups and conditions suggested that the patients made less use of visual information for postural control than the healthy subjects.
    Gait & posture 05/2013; · 2.58 Impact Factor
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    ABSTRACT: BACKGROUND: A major problem with rehabilitation interventions for neck pain is that the condition may have multiple causes, thus a single treatment approach is seldom efficient. The present study protocol outlines a single blinded randomised controlled trial evaluating the effect of tailored treatment for neck-shoulder pain. The treatment is based on a decision model guided by standardized clinical assessment and functional tests with cut-off values. Our main hypothesis is that the tailored treatment has better short, intermediate and long-term effects than either non-tailored treatment or treatment-as-usual (TAU) on pain and function. We sub-sequentially hypothesize that tailored and non-tailored treatment both have better effect than TAU. METHODS: 120 working women with minimum six weeks of nonspecific neck-shoulder pain aged 20-65, are allocated by minimisation with the factors age, duration of pain, pain intensity and disability in to the groups tailored treatment (T), non-tailored treatment (NT) or treatment-as-usual (TAU). Treatment is given to the groups T and NT for 11 weeks (27 sessions evenly distributed). An extensive presentation of the tests and treatment decision model is provided. The main treatment components are manual therapy, cranio-cervical flexion exercise and strength training, EMG-biofeedback training, treatment for cervicogenic headache, neck motor control training. A decision algorithm based on the baseline assessment determines the treatment components given to the each participant of T- and NT-groups. Primary outcome measures are physical functioning (Neck Disability Index) and average pain intensity last week (Numeric Rating Scale). Secondary outcomes are general improvement (Patient Global Impression of Change scale), symptoms (Profile Fitness Mapping neck questionnaire), capacity to work in the last 6 weeks (quality and quantity) and pressure pain threshold of m. trapezius. Primary and secondary outcomes will be reported for each group with effect size and its precision. DISCUSSION: We have chosen not to include women with psychological ill-health and focus on biomedical aspects of neck pain. Future studies should aim at including psychosocial aspects in a widened treatment decision model. No important adverse events or side-effects are expected. Trial registration: Current Controlled Trials registration ISRCTN49348025. Key words: Neck, trapezius, myalgia, neck-shoulder pain, RCT, individualized treatment, rehabilitation, physiotherapy, tailored.
    BMC Musculoskeletal Disorders 05/2012; 13(1):75. · 1.90 Impact Factor
  • Thomas Rudolfsson, Martin Björklund, Mats Djupsjöbacka
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    ABSTRACT: Reduced cervical range of motion (ROM) is a common finding in people with neck pain. With few exceptions, only the angle between head and thorax has been measured. Our aim was to use an extended model to compare active cervical flexion and extension, separate for upper and lower cervical levels, between people with chronic non-traumatic neck pain and controls. We also investigated associations between ROM measures, symptoms and self-rated functioning. In this cross-sectional study, 102 subjects with neck pain and 33 healthy controls participated. An electromagnetic tracker system was used to measure the kinematics to construct a three-segment model including the thorax, cervical spine and head. Neutral flexion/extension were defined at subjects' self-selected seated posture. We found that in the neck pain group, extension in the upper cervical levels and predominately flexion for the lower levels were reduced. The ratio between ROM for the upper and lower levels was altered in the neck pain group so that the lower levels contributed to a lesser extent to the total sagittal ROM compared to controls. These findings could not be explained by a greater forward head posture but must have other origins. For the neck pain group, ROM measures were weakly associated to pain and self-rated functioning. Altogether, this implies that using a three-segment model for assessment of ROM can be a valuable improvement for characterisation of patients and treatment evaluation.
    Manual therapy 09/2011; 17(1):53-9. · 2.32 Impact Factor
  • Ulrik Röijezon, Martin Björklund, Mats Djupsjöbacka
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    ABSTRACT: Several studies have reported altered postural control in people with neck pain. The aim of this study was to increase the understanding of the nature of altered postural control in neck pain by studying the slow and fast components of body sway. Subjects with whiplash associated disorders (WAD, n = 21) and chronic non-specific neck pain (NS, n = 24) were compared to healthy controls (CON, n = 21) in this cross-sectional study. The magnitudes of the slow and fast sway components were assessed in Rhomberg quiet stance for 30 s on a force plate with eyes closed. We also investigated associations between postural sway and symptoms, self-ratings of functioning and kinesiophobia. Increased magnitude of the slow sway component was found in WAD, but not in NS. Greater magnitude of the slow component in WAD was associated with poorer physical functioning, including balance disturbances, and more severe sensory symptoms. Increased magnitude of the slow sway component implies an aberration in sensory feedback or processing of sensory information in WAD. The associations between postural sway and self-rated characteristics support the clinical validity of the test. Further investigation into NS, involving a longer test time is warranted.
    Manual therapy 12/2010; 16(3):273-8. · 2.32 Impact Factor
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    ABSTRACT: Assessment of sensorimotor function is useful for classification and treatment evaluation of neck pain disorders. Several studies have investigated various aspects of cervical motor functions. Most of these have involved slow or self-paced movements, while few have investigated fast cervical movements. Moreover, the reliability of assessment of fast cervical axial rotation has, to our knowledge, not been evaluated before. Cervical kinematics was assessed during fast axial head rotations in 118 women with chronic nonspecific neck pain (NS) and compared to 49 healthy controls (CON). The relationship between cervical kinematics and symptoms, self-rated functioning and fear of movement was evaluated in the NS group. A sub-sample of 16 NS and 16 CON was re-tested after one week to assess the reliability of kinematic variables. Six cervical kinematic variables were calculated: peak speed, range of movement, conjunct movements and three variables related to the shape of the speed profile. Together, peak speed and conjunct movements had a sensitivity of 76% and a specificity of 78% in discriminating between NS and CON, of which the major part could be attributed to peak speed (NS: 226 ± 88°/s and CON: 348 ± 92°/s, p < 0.01). Peak speed was slower in NS compared to healthy controls and even slower in NS with comorbidity of low-back pain. Associations were found between reduced peak speed and self-rated difficulties with running, performing head movements, car driving, sleeping and pain. Peak speed showed reasonably high reliability, while the reliability for conjunct movements was poor. Peak speed of fast cervical axial rotations is reduced in people with chronic neck pain, and even further reduced in subjects with concomitant low back pain. Fast cervical rotation test seems to be a reliable and valid tool for assessment of neck pain disorders on group level, while a rather large between subject variation and overlap between groups calls for caution in the interpretation of individual assessments.
    BMC Musculoskeletal Disorders 09/2010; 11:222. · 1.90 Impact Factor
    This article is viewable in ResearchGate's enriched format
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    ABSTRACT: The effect of neck/shoulder pain on the performance in a hand laterality motor imagery test was studied. Responses to the Cooper and Shepard (1975, Journal of Experimental Psychology: Human Perception and Performance 104 48-56) hand laterality test were explored in twenty-four individuals with chronic non-specific neck pain and twenty-one subjects with chronic neck pain of traumatic origin (whiplash-associated disorder). Twenty-two controls were also included in the study. Digitalised right- or left-hand stimuli were presented at five different stimulus angles (0 degrees, 45 degrees laterally, 90 degrees laterally, 135 degrees laterally, and 180 degrees). The experimental task was to decide the laterality as fast and accurately as possible. The performance, both reaction time (RT) and accuracy, of the two experimental groups was contrasted with that of the control group. The main results revealed that the subjects afflicted with whiplash injury on the average exhibited a faster response pattern than symptom-free healthy controls. Despite their musculoskeletal deficits and experience of pain these volunteers also exhibited a preserved speed-accuracy tradeoff. Longer duration of time with symptoms of neck pain was, moreover, associated with progressively faster RTs. These results point to perceptual learning and may reflect different stages of adaptation to neck pain.
    Perception 01/2010; 39(1):119-30. · 1.11 Impact Factor
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    ABSTRACT: Previous research has indicated neck-shoulder disorders to have a fluctuating course incorporating a variety of symptoms. These findings awoke our interest to make a comparison between symptoms experienced by people affected with the disorder and the content of questionnaires that assess pain and other symptoms in neck-shoulder disorders. Thus the aims of this study were: -to explore the symptoms experienced by people with non-specific neck-shoulder problems, as well as experiences of nuances and temporal variations (fluctuations) of symptoms; -to investigate which sources were used in the development of ten questionnaires for assessing pain and other symptoms in the neck-shoulder; -to analyse the item content of the questionnaires; -to analyse the correspondence between the item content of the questionnaires and the symptoms described by the informants. Content analysis of interviews with 40 people with non-specific neck-shoulder pain, and 10 questionnaires used to assess pain and other symptoms in neck-shoulder disorders. The interviews revealed a variety of symptoms indicating a bodily, mental/cognitive, and emotional engagement, and more general and severe symptoms than are usually considered in neck-shoulder questionnaires. Taking all questionnaires together many of the symptoms were considered, but most questionnaires only included a few of them. The informants were able to distinguish fluctuation of symptoms, and a variety of different qualities which were not usually considered in the questionnaires. Only two questionnaires had made use of the opinions of affected people in the development. Few of the questionnaires had made use of the experiences of affected people in the development. The correspondence between the symptoms expressed by those affected and the content of the questionnaires was low. A variety of symptoms were expressed by the interviewees, and the participants were also able to distinguish nuances and fluctuations of symptoms. The present study points to the importance of other aspects than just pain and physical functioning as clinical trial outcome measures related to neck-shoulder disorders. To develop a condition-specific questionnaire, it is important to decide on the specific symptoms for the condition. Using the experiences of those affected, in combination with relevant research and professional knowledge, can enhance the validity of the questionnaires.
    BMC Musculoskeletal Disorders 04/2009; 10:30. · 1.90 Impact Factor
    This article is viewable in ResearchGate's enriched format
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    ABSTRACT: Chronic neck pain is a common problem and is often associated with changes in sensorimotor functions, such as reduced proprioceptive acuity of the neck, altered coordination of the cervical muscles, and increased postural sway. In line with these findings there are studies supporting the efficacy of exercises targeting different aspects of sensorimotor function, for example training aimed at improving proprioception and muscle coordination. To further develop this type of exercises we have designed a novel device and method for neck coordination training. The aim of the study was to investigate the clinical applicability of the method and to obtain indications of preliminary effects on sensorimotor functions, symptoms and self-rated characteristics in non-specific chronic neck pain The study was designed as an uncontrolled clinical trial including fourteen subjects with chronic non-specific neck pain. A new device was designed to allow for an open skills task with adjustable difficulty. With visual feedback, subjects had to control the movement of a metal ball on a flat surface with a rim strapped on the subjects' head. Eight training sessions were performed over a four week period. Skill acquisition was measured throughout the intervention period. After intervention subjects were interviewed about their experience of the exercise and pain and sensorimotor functions, including the fast and slow components of postural sway and jerkiness-, range-, position sense-, movement time- and velocity of cervical rotation, were measured. At six-month follow up, self-rated pain, health and functioning was collected. The subjects improved their skill to perform the exercise and were overall positive to the method. No residual negative side-effects due to the exercise were reported. After intervention the fast component of postural sway (p = 0.019) and jerkiness of cervical rotation (p = 0.032) were reduced. The follow up showed decreased disability (one out of three indices) and fear of movement, and increased general health (three out of eight dimensions). The results support the clinical applicability of the method. The improvements in sensorimotor functions may suggest transfer from the exercise to other, non-task specific motor functions and justifies a future randomized controlled trial.
    Journal of NeuroEngineering and Rehabilitation 01/2009; 5(1):36. · 2.62 Impact Factor
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    ABSTRACT: The purpose of this pilot study was to evaluate sensorimotor functions in patients with chronic neck pain with objective and quantitative methods. A group of 16 patients with chronic idiopathic neck pain of insidious onset or whiplash associated disorders (WAD) was compared to an equally sized group of healthy subjects. Kinematics were investigated during voluntary head rotations by measuring range of motion, variability of range of motion (ROM-Variability), peak velocity, and smoothness of movement (jerk index). Repositioning acuity after cervical rotations was evaluated by analysing constant and variable error (VE). In comparison to the healthy subjects, the patients showed significantly larger jerk index, ROM-Variability and VE. No statistically significant differences were found between insidious neck pain and WAD. It is concluded that jerky and irregular cervical movements and poor position sense acuity are characteristic sensorimotor symptoms in chronic neck pain. The observed individuality in sensorimotor disturbances emphasizes the importance of developing specific rehabilitation programs for specific dysfunctions, and of using objective and quantitative methods for evaluation of rehabilitation.
    Manual therapy 06/2008; 13(2):122-31. · 2.32 Impact Factor
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    ABSTRACT: To evaluate end-point acuity in goal-directed arm movements in subjects with chronic neck pain, while taking the trade-off between speed and accuracy into account, and to evaluate associations between reduced acuity and self-rated characteristics. Single-blinded, controlled, comparative group study. Forty-five subjects with chronic non-traumatic, non-specific neck pain (n = 24) and whiplash-associated disorders (n = 21). Healthy subjects served as controls (n = 22). The groups were age- and sex-matched. Subjects performed fast and accurate pointing movements to a visual target. Group differences in end-point variability, controlled for peak velocity, were evaluated. Associations between end-point variability and self-rated symptoms, functioning, self-efficacy and kinesiophobia were analysed. End-point acuity, controlled for peak velocity, was reduced for both neck-pain groups. Similar spatial error patterns across all groups indicated no direction-specific reduction. For both neck-pain groups, associations were found between end-point acuity and neck movement deficits, physical functioning and, in whiplash, also balance and pain. Acuity of goal-directed arm movements can be reduced in chronic neck pain. Associations between acuity and self-rated characteristics support the clinical validity of the results and indicate that impaired neck function contributes to reduced end-point acuity. The results can be of importance for characterization and rehabilitation of neck disorders.
    Journal of Rehabilitation Medicine 06/2008; 40(5):366-74. · 1.90 Impact Factor
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    ABSTRACT: To resolve the debate over whether lumbar repositioning acuity is reduced in patients with chronic low back pain (CLBP) by using a study design and methodology to minimize the effects of potential confounders. A single-blinded, controlled, multigroup comparative study. Vocational rehabilitation center. Ninety-two patients with CLBP, divided into subgroups based on severity of symptoms and diagnostic characteristics. An age- and sex-matched group (n=31) of healthy subjects were the control. Not applicable. We measured repositioning errors (variable, constant) at 3 positions of the lumbar spine. Subjects were guided to a sitting target posture and asked to perform lumbar flexion before reproducing the target posture. Self-assessed pain, self-efficacy, and functional ability were addressed through questionnaires. There were no differences in repositioning errors between the patients with CLBP or the subgroups of patients and the control group. We found only weak correlations between the repositioning errors and the self-reported data on functional disability, self-efficacy, and pain. We suggest that sensorimotor dysfunctions in CLBP should be evaluated with methods other than repositioning tests in order to generate data relevant to the development of rational diagnostic methods and rehabilitation programs.
    Archives of Physical Medicine and Rehabilitation 10/2006; 87(9):1170-6. · 2.44 Impact Factor
  • A G Crenshaw, M Djupsjöbacka, A Svedmark
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    ABSTRACT: We investigated the effects of active versus passive pauses implemented during computer mouse work on muscle oxygenation and EMG of the forearm extensor carpi radialis muscle, and on wrist position sense. Fifteen healthy female subjects (age: 19-24 years) performed a 60-min mouse-operated computer task, divided into three 20 min periods, on two occasions separated by 3-6 days. On one occasion a passive pause (subjects resting) was implemented at the end of each 20-min period, and on another occasion an active pause (subjects performed a number of high intensity extensions of the forearm) was implemented. Also at the end of each 20-min period, test contractions were conducted and subjective ratings of fatigue and stress were obtained. Another parameter of interest was total haemoglobin calculated as the summation of oxy-and deoxy-haemoglobin, since it reflects blood volume changes. The most interesting findings were an overall increasing trend in total haemoglobin throughout the mouse work (P<0.001), and that this trend was greater for the active pause as compared to the passive pause (P<0.01). These data were accompanied by an overall increase in oxygen saturation (P<0.001), with a tendency, albeit not significant, toward a higher increase for the active pause (P=0.13). EMG amplitude and median frequency tended to decrease (P=0.08 and 0.05, respectively) during the mouse work but was not different between pause types. Borg ratings of forearm fatigue showed an overall increase during the activity (P<0.001), but the perceptions of stress did not change. Position sense did not change due to the mouse work for either pause type. While increasing trends were found for both pause types, the present study lends support to the hypothesis of an enhancement in oxygenation and blood volume for computer mouse work implemented with active pauses. However, a presumption of an association between this enhancement and attenuated fatigue during the mouse work was not supported.
    Arbeitsphysiologie 05/2006; 97(1):59-67. · 2.30 Impact Factor
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    ABSTRACT: To evaluate whether patients suffering from whiplash-associated disorders have impaired shoulder proprioception and whether the acuity of shoulder proprioception is reflected in the patients' symptoms and self-rated function. A comparative group design, including a correlation design for the patient group. Patients with chronic whiplash-associated disorders (n=37) and healthy subjects (n=41). The groups were matched for age and gender. All subjects underwent a shoulder proprioception test involving active ipsilateral arm position-matching. Group difference was evaluated by multiple analysis of variance and analysis of variance. The patient group completed questionnaires addressing functioning and health and performed pain ratings. Associations between proprioceptive acuity and self-rated functioning and symptoms were studied by correlation and regression analyses. The patient group showed significantly lower acuity of shoulder proprioception. Moderate correlations were found between proprioceptive acuity and questionnaire scores representing physical functioning, so that low proprioceptive acuity was associated with low self-rated physical functioning. Scores representing pain-intensity did not correlate with proprioceptive acuity. The results show that, at the group level, patients with whiplash-associated disorders have impaired shoulder proprioception. The clinical relevance of this finding is strongly supported by the association between shoulder proprioceptive acuity and self-rated functioning in the patient group.
    Journal of Rehabilitation Medicine 02/2006; 38(1):44-9. · 1.90 Impact Factor
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    ABSTRACT: Much is still unknown concerning the mechanisms underlying the development of chronic muscle pain. The presence and magnitude of inflammatory substances and neurotransmitters in chronic painful conditions is not clear. The aims of the present study were to determine, with the use of microdialysis, the interstitial concentrations and the equilibration times for PGE2 and glutamate in the trapezius muscles of nine female subjects with chronic muscle pain, and nine pain-free age-matched controls. A microdialysis probe was implanted in the upper part of the trapezius muscle and perfused with Ringer-acetate solution at a flow rate of 0.3 microL/min. Samples were obtained every 30 min, during a 4-h rest period. At equilibration, the mean concentrations (+/-SE) of PGE2 were 0.71 (+/-0.11) ng/mL for the pain-group and 0.97 (+/-0.35) ng/mL for the controls. For glutamate the mean concentrations for the pain-group were 66.3 (+/-13.3) micromol/L and 60.6 (+/-22.9) micromol/L for the controls. For the pain group and the control group, respectively, equilibration for PGE2 was reached at 180 and 150 min, and for glutamate at 150 and 120 min. The present study showed no differences between groups in the concentrations of PGE2 and glutamate in the trapezius muscle. Further, it revealed that when using the slow-flow method, a period of at least 2.0-2.5 h is needed, after probe insertion, to reach steady state for glutamate and PGE2.
    European Journal of Pain 11/2005; 9(5):511-5. · 3.22 Impact Factor
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    ABSTRACT: Previous studies performed in jaw muscles of rabbits and rats have demonstrated that sympathetic outflow may affect the activity of muscle spindle afferents (MSAs). The resulting impairment of MSA information has been suggested to be involved in the genesis and spread of chronic muscle pain. The present study was designed to investigate sympathetic influences on muscle spindles in feline trapezius and splenius muscles (TrSp), as these muscles are commonly affected by chronic pain in humans. Experiments were carried out in cats anesthetized with alpha-chloralose. The effect of electrical stimulation (10 Hz for 90 s or 3 Hz for 5 min) of the peripheral stump of the cervical sympathetic nerve (CSN) was investigated on the discharge of TrSp MSAs (units classified as Ia-like and II-like) and on their responses to sinusoidal stretching of these muscles. In some of the experiments, the local microcirculation of the muscles was monitored by laser Doppler flowmetry. In total, 46 MSAs were recorded. Stimulation of the CSN at 10 Hz powerfully depressed the mean discharge rate of the majority of the tested MSAs (73%) and also affected the sensitivity of MSAs to sinusoidal changes of muscle length, which were evaluated in terms of amplitude and phase of the sinusoidal fitting of unitary activity. The amplitude was significantly reduced in Ia-like units and variably affected in II-like units, while in general the phase was affected little and not changed significantly in either group. The discharge of a smaller percentage of tested units was also modulated by 3-Hz CSN stimulation. Blockade of the neuromuscular junctions by pancuronium did not induce any changes in MSA responses to CSN stimulation, showing that these responses were not secondary to changes in extrafusal or fusimotor activity. Further data showed that the sympathetically induced modulation of MSA discharge was not secondary to the concomitant reduction of muscle blood flow induced by the stimulation. Hence, changes in sympathetic outflow can modulate the afferent signals from muscle spindles through an action exerted directly on the spindles, independent of changes in blood flow. It is suggested that such an action may be one of the mechanisms mediating the onset of chronic muscle pain in these muscles in humans.
    Experimental Brain Research 10/2005; 165(3):328-42. · 2.17 Impact Factor
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    ABSTRACT: Responses of gastrocnemius-soleus (G-S) motoneurones to stretches of the homonymous muscles were recorded intracellularly in decerebrate cats before, during and after fatiguing stimulation (FST) of G-S muscles. Ventral roots (VR) L7 and S1 were cut, and FST was applied to VR S1, a single FST session including 4 to 5 repetitions of 12-s periods of regular 40 s(-1) stimulation. Muscle stretches consisted of several phases of slow sinusoidal shortening-lengthening cycles and intermediate constant lengths. The maximal stretch of the muscles was 8.8 mm above the rest length. Effects of FST on excitatory postsynaptic potentials (EPSPs) and spikes evoked by the muscle stretches were studied in 12 motoneurones from ten experiments. Stretch-evoked EPSPs and firing were predominantly suppressed after FST, with the exception of a post-contraction increase of the first EPSP after FST, which was most likely due to after-effects in the activity of muscle spindle afferents. The post-fatigue suppression of EPSPs and spike activity was followed by restoration within 60-100 s. Additional bouts of FST augmented the intensity of post-fatigue suppression of EPSPs, with the spike activity sometimes disappearing completely. FST itself elicited EPSPs at latencies suggesting activation of muscle spindle group Ia afferents via stimulation of beta-fibres. The suppression of the stretch-evoked responses most likely resulted from fatigue-evoked activity of group III and IV muscle afferents. Presynaptic inhibition could be one of the mechanisms involved, but homosynaptic depression in the FST-activated group Ia afferents may also have contributed.
    Experimental Brain Research 07/2005; 163(3):284-94. · 2.17 Impact Factor
  • Mats Djupsjöbacka, Dmitry Domkin
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    ABSTRACT: In order to plan and control movements the central nervous system (CNS) needs to continuously keep track of the state of the musculoskeletal system. Therefore the CNS constantly uses sensory input from mechanoreceptors in muscles, joints and skin to update information about body configuration on different levels of the CNS. On the conscious level, such representations constitute proprioception. Different tests for assessment of proprioceptive acuity have been described. However, it is unclear if the proprioceptive acuity measurements in these tests correlate within subjects. By using both uni- and multivariate analysis we compared proprioceptive acuity in different variants of ipsilateral active and passive limb position-matching and ipsilateral passive limb movement velocity-discrimination in a group of healthy subjects. The analysis of the position-matching data revealed a higher acuity of matching for active movements in comparison to passive ones. The acuity of matching was negatively correlated to movement extent. There was a lack of correlation between proprioceptive acuity measurements in position-matching and velocity-discrimination.
    Somatosensory and Motor Research 06/2005; 22(1-2):85-93. · 0.58 Impact Factor
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    ABSTRACT: The structure of joint angle variability and its changes with practice were investigated using the uncontrolled manifold (UCM) computational approach. Subjects performed fast and accurate bimanual pointing movements in 3D space, trying to match the tip of a pointer, held in the right hand, with the tip of one of three different targets, held in the left hand during a pre-test, several practice sessions and a post-test. The prediction of the UCM approach about the structuring of joint angle variance for selective stabilization of important task variables was tested with respect to selective stabilization of time series of the vectorial distance between the pointer and aimed target tips (bimanual control hypothesis) and with respect to selective stabilization of the endpoint trajectory of each arm (unimanual control hypothesis). The components of the total joint angle variance not affecting (V(COMP)) and affecting (V(UN)) the value of a selected task variable were computed for each 10% of the normalized movement time. The ratio of these two components R(V)=V(COMP)/V(UN) served as a quantitative index of selective stabilization. Both the bimanual and unimanual control hypotheses were supported, however the R(V) values for the bimanual hypothesis were significantly higher than those for the unimanual hypothesis applied to the left and right arm both prior to and after practice. This suggests that the CNS stabilizes the relative trajectory of one endpoint with respect to the other more than it stabilizes the trajectories of each of the endpoints in the external space. Practice-associated improvement in both movement speed and accuracy was accompanied by counter-intuitive lack of changes in R(V). Both V(COMP) and V(UN) variance components decreased such that their ratio remained constant prior to and after practice. We conclude that the UCM approach offers a unique and under-explored opportunity to track changes in the organization of multi-effector systems with practice and allows quantitative assessment of the degree of stabilization of selected performance variables.
    Experimental Brain Research 06/2005; 163(1):44-57. · 2.17 Impact Factor

Publication Stats

1k Citations
92.55 Total Impact Points


  • 2003–2015
    • Högskolan i Gävle
      • Centre for Musculoskeletal Research (CBF)
      Gäfle, Gävleborg, Sweden
  • 2013
    • Sør-Trøndelag University College
      Nidaros, Sør-Trøndelag, Norway
  • 1989–2009
    • Umeå University
      • • Department of Nursing
      • • Department of Surgical and Perioperative Sciences
      • • Department of Plant Physiology
      Umeå, Vaesterbotten, Sweden
  • 2005
    • National Academy of Sciences of Ukraine
      • Department of Movements Physiology
      Kiev, Misto Kyyiv, Ukraine
  • 1994–1996
    • National Veterinary Institute, Sweden
      Uppsala, Uppsala, Sweden