Ankle proprioception is not targeted by exercises on an unstable surface

Item does not contain fulltextLaboratory study using a repeated measures design. The aim of this study was to determine if ankle proprioception is targeted in exercises on unstable surfaces. Lateral ankle sprain (LAS) has recurrence rates over 70%, which are believed to be due to a reduced accuracy of proprioceptive signals from the ankle. Proprioceptive exercises in rehabilitation of LAS mostly consist of balancing activities on an unstable surface. The methods include 100 healthy adults stood barefoot on a solid surface and a foam pad over a force plate, with occluded vision. Mechanical vibration was used to stimulate proprioceptive output of muscle spindles of triceps surae and lumbar paraspinal musculature. Each trial lasted for 60 s; vibration was applied from the 15th till the 30th second. Changes in mean velocity and mean position of the center of pressure (CoP) as a result of muscle vibration were calculated. Results show that on foam, the effect of triceps surae vibration on mean CoP velocity was significantly smaller than on a solid surface, while for paraspinal musculature vibration the effect was bigger on foam than on solid surface. Similar effects were seen for mean CoP displacement as outcome. Exercises on unstable surfaces appear not to target peripheral ankle proprioception. Exercises on an unstable surface may challenge the capacity of the central nervous system to shift the weighting of sources of proprioceptive signals on balance

Gezond zijn, gezond blijven. Een visie op gezondheid en preventie.

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H3. Doel en type meetinstrumenten

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De effectiviteit van manipulaties in subgroepen van patiënten met (sub)acute aspecifieke lagerugklachten: een systematische review.

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Test–retest reliability of muscle vibration effects on postural sway

The effect of alterations in the processing of proprioceptive signals, on postural control, has been studied using muscle vibration effects. However, reliability and agreement of muscle vibration have still to be addressed. This study aimed to assess intra- and interday reliability and agreement of vibration effects of lumbar paraspinal and triceps surae muscles in a non-selected sample of 20 subjects, standing on solid surface and on foam. We used mean position and velocity of Centre of Pressure (CoP), during and after vibration to quantify the effect of muscle vibration. We also calculated the ratio of vibration effects on the lumbar paraspinal and triceps surae muscles (proprioceptive weighting). Displacement of the CoP during vibration showed good reliability (ICCs>0.6), and proprioceptive weighting of displacement fair to good reliability (0.52-0.73). Agreement measures were poor, with most CV's ranging between 18% and 36%. Change in CoP velocity appeared not to be reliable. Balance recovery, when based on CoP position and calculated a short period after cessation of vibration, showed good reliability. According to this study, displacement during vibration, proprioceptive weighting and selected recovery variables are the most reliable indicators of the response to muscle vibration.publisher: Elsevier articletitle: Test–retest reliability of muscle vibration effects on postural sway journaltitle: Gait & Posture articlelink: http://dx.doi.org/10.1016/j.gaitpost.2014.03.184 content_type: article copyright: Copyright © 2014 Elsevier B.V. All rights reserved.status: publishe

Effect of postural threat on motor control in people with and without low back pain

Introduction Negative pain-related cognitions are associated with persistence of low-back pain (LBP), but the mechanism underlying this association is not well understood. We propose that negative pain-related cognitions determine how threatening a motor task will be perceived, which in turn will affect how lumbar movements are performed, possibly with negative long-term effects on pain. Objective To assess the effect of postural threat on lumbar movement patterns in people with and without LBP, and to investigate whether this effect is associated with task-specific pain-related cognitions. Methods 30 back-healthy participants and 30 participants with LBP performed consecutive two trials of a seated repetitive reaching movement (45 times). During the first trial participants were threatened with mechanical perturbations, during the second trial participants were informed that the trial would be unperturbed. Movement patterns were characterized by temporal variability (CyclSD), local dynamic stability (LDE) and spatial variability (meanSD) of the relative lumbar Euler angles. Pain-related cognition was assessed with the task-specific ‘Expected Back Strain’-scale (EBS). A three-way mixed Manova was used to assess the effect of Threat, Group (LBP vs control) and EBS (above vs below median) on lumbar movement patterns. Results We found a main effect of threat on lumbar movement patterns. In the threat-condition, participants showed increased variability (MeanSDflexion-extension, p<0.000, η2 = 0.26; CyclSD, p = 0.003, η2 = 0.14) and decreased stability (LDE, p = 0.004, η2 = 0.14), indicating large effects of postural threat. Conclusion Postural threat increased variability and decreased stability of lumbar movements, regardless of group or EBS. These results suggest that perceived postural threat may underlie changes in motor behavior in patients with LBP. Since LBP is likely to impose such a threat, this could be a driver of changes in motor behavior in patients with LBP, as also supported by the higher spatial variability in the group with LBP and higher EBS in the reference condition

Differences in proprioceptive postural control during the sit-to-stand-to-sit movement between persons with non-specific low back pain and healthy controls on a stable surface

Introduction: Persons with non-specific low back pain (NSLBP) have been observed to have an altered postural control strategy during static postural conditions (e.g. quiet standing), due to decreased reliance on lumbosacral proprioceptive inputs [1]. It remains unclear whether persons with NSLBP show an altered proprioceptive control strategy during more dynamic postural tasks. Therefore, the aim of the present study was to examine the performance of a sit-to-stand-to-sit task (STSTS) on a stable support surface in persons with NSLBP and healthy controls. Methods: The total duration of five consecutive STSTS movements as well as the duration of each stance, sitting and movement phase of 47 young subjects with NSLBP and 9 young pain-free subjects was recorded. Postural sway characteristics were evaluated with a six-channel force plate during the five consecutive STSTS movements. In addition, muscle vibration on triceps surae muscles and lumbar multifidus muscles was used to appraise the relative proprioceptive weighting (RPW) [1]. A score equal to 1 corresponds to 100% reliance on afferent input from triceps surae muscles for postural control, a score equal to 0 corresponds to 100% reliance on back muscle afferent input. Results: Persons with NSLBP need significantly more time to perform five consecutive STSTS movements compared to pain-free subjects (p0.05). Furthermore, the postural sways during the stance phases are significantly larger in persons with NSLBP compared to the healthy controls (p<0.05). In addition, persons with NSLBP have significantly higher RPW values in comparison with the healthy persons (NSLBP: 0.71±0.17; Healthy: 0.51±0.15; p<0.05). Conclusion: The adopted proprioceptive postural control strategy (i.e. more ankle-steered vs. multi-segmental control observed in healthy persons) in people with NSLBP seemed to have a negative effect on the performance of a dynamic postural task such as STSTS. A task of associated movements or anticipatory postural adjustments is to maintain postural stability during movements with high acceleration or mass displacement [2]. Therefore, the observations of the longer duration of the stance phases and the concomitant larger sways suggest mainly impairments in anticipatory postural adjustments and not in the focal motor program in persons with NSLBP. Moreover, the control of pelvic movement in the process of mass redistribution during trunk movement is normally highly efficient, however, this proprioceptive control of the pelvis may be impaired in these subjects with NSLBP [2,3]. Further study with direct measurement of pelvis kinematics is needed to underscore this hypothesis. References: 1. Brumagne S et al. Eur. Spine J. 17:1177-84, 2008. 2. Cordo PJ, Gurfinkel VS. Prog. Brain Res. 143:29-38, 2004. 3. Brumagne S et al. Spine 25:989-994, 2000.status: publishe

Postural sway and integration of proprioceptive signals in subjects with LBP

Patients with non-specific low back pain (LBP) may use postural control strategies that differ from healthy subjects. To study these possible differences, we measured the amount and structure of postural sway, and the response to muscle vibration in a working cohort of 215 subjects. Subjects were standing on a force plate in bipedal stance. In the first trial the eyes were open, no perturbation applied. In the following 6 trials, vision was occluded and subjects stood under various conditions of vibration/no vibration of the lumbar spine or m. Triceps Surae (TSM) on firm surface and on foam surface. We performed a factor analysis to reduce the large amount of variables that are available to quantify all effects. Subjects with LBP showed the same amount of sway as subjects without LBP, but the structure of their sway pattern was less regular with higher frequency content. Subjects with LBP also showed a smaller response to TSM vibration, and a slower balance recovery after cessation of vibration when standing on a solid surface. There was a weak but significant association between smaller responses to TSM vibration and an irregular, high frequency sway pattern, independent from LBP. A model for control of postural sway is proposed. This model suggests that subjects with LBP use more co-contraction and less cognitive control, to maintain a standing balance when compared to subjects without LBP. In addition, a reduced weighting of proprioceptive signals in subjects with LBP is suggested as an explanation for the findings in this study.publisher: Elsevier articletitle: Postural sway and integration of proprioceptive signals in subjects with LBP journaltitle: Human Movement Science articlelink: http://dx.doi.org/10.1016/j.humov.2014.05.011 content_type: article copyright: Copyright © 2014 Published by Elsevier B.V.status: publishe