Postural destabilization induced by trunk extensor muscles fatigue is suppressed by use of a plantar pressure-based electro-tactile biofeedback

Separate studies have reported that postural control during quiet standing could be (1) impaired with muscle fatigue localized at the lower back, and (2) improved through the use of plantar pressure-based electro-tactile biofeedback, under normal neuromuscular state. The aim of this experiment was to investigate whether this biofeedback could reduce postural destabilization induced by trunk extensor muscles. Ten healthy adults were asked to stand as immobile as possible in four experimental conditions: (1) no fatigue/no biofeedback, (2) no fatigue/biofeedback, (3) fatigue/no biofeedback and (4) fatigue/biofeedback. Muscular fatigue was achieved by performing trunk repetitive extensions until maximal exhaustion. The underlying principle of the biofeedback consisted of providing supplementary information related to foot sole pressure distribution through electro-tactile stimulation of the tongue. Centre of foot pressure (CoP) displacements were recorded using a force platform. Results showed (1) increased CoP displacements along the antero-posterior axis in the fatigue than no fatigue condition in the absence of biofeedback and (2) no significant difference between the no fatigue and fatigue conditions in the presence of biofeedback. This suggests that subjects were able to efficiently integrate an artificial plantar pressure information delivered through electro-tactile stimulation of the tongue that allowed them to suppress the destabilizing effect induced by trunk extensor muscles fatigue

Effets d'une suppl\'eance perceptive visuelle, auditive et tactile sur le contr\^ole des pressions fessi\`eres en position assise

This article presents a study on different informative modalities of a perceptual supplementation device aiming at reducing overpressure at the buttock area. Visual, audio and tactile modalities are analysed and compared with a non-biofeedback session. In conclusion, modalities have a positive and equal effect, but they are not equally judged in term of comfort and disturbance with some other activitie

A Plantar-pressure Based Tongue-placed Tactile Biofeedback System for Balance Improvement

Maintaining an upright stance represents a complex task, which is achieved by integrating sensory information from the visual, vestibular and somatosensory systems. When one of these sensory inputs becomes unavailable and/or inaccurate and/or unreliable, postural control generally is degraded. One way to solve this problem is to supplement and/or substitute limited/altered/missing sensory information by providing additional sensory information to the central nervous system via an alternative sensory modality. Along these lines, we developed an original biofeedback system [1] whose underlying principle consists in supplying the user with supplementary sensory information related to foot sole pressure distribution through a tongue-placed output device (Tongue Display Unit, "TDU" [2]). The purpose of the present experiment was to assess its effectiveness in improving balance in young healthy adults

Using contextual factors to elicit placebo and nocebo effects: An online survey of healthcare providers' practice

Contextual factor use by healthcare professionals has been studied mainly among nurses and physiotherapists. Preliminary results show that healthcare professionals use contextual factors without specifically labelling them as such. The main objective of this study was to evaluate knowledge and explore voluntary contextual factor use among various healthcare professions. The results aim to facilitate hypothesis-generation, to better position further research to explain and characterise contextual factor use. We conducted a web-based questionnaire cross-sectional observational study on a non-probabilistic convenience sample. Face and content validity were tested through cognitive interviews. Data were analysed descriptively. The target population was the main healthcare profession, or final year students, defined by the French public health law. The countries of distribution of the questionnaire were the French-speaking European countries. Among our 1236 participants, use of contextual factors was widespread. Those relating to the therapeutic relationship (e.g., communication) and patient characteristics (e.g., past experiences) were reportedly the most used. Meanwhile, contextual factors related to the healthcare providers' characteristics and their own beliefs were reported as less used. Despite high variability, respondents suggested contextual effects contribute to approximately half of the overall effect in healthcare and were perceived as more effective on children and elderly adults. Conceptual variations that exist in the literature are also present in the way healthcare providers consider contextual effects. Interestingly, there seems to be common ground between how physiotherapists, nurses and physicians use different contextual factors. Finally, in the present study we also observed that while there are similarities across usage, there is lack of both an epistemological and ethical consensus among healthcare providers with respect to contextual factors

How a plantar pressure-based, tongue-placed tactile biofeedback modifies postural control mechanisms during quiet standing

The purpose of the present study was to determine the effects of a plantar pressure-based, tongue-placed tactile biofeedback on postural control mechanisms during quiet standing. To this aim, sixteen young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. Centre of foot pressure (CoP) displacements, recorded using a force platform, were used to compute the horizontal displacements of the vertical projection the centre of gravity (CoGh) and those of the difference between the CoP and the vertical projection of the CoG (CoP-CoGv). Altogether, the present findings suggest that the main way the plantar pressure-based, tongue-placed tactile biofeedback improves postural control during quiet standing is via both a reduction of the correction thresholds and an increased efficiency of the corrective mechanism involving the CoGh displacements

Sensory supplementation system based on electrotactile tongue biofeedback of head position for balance control

The present study aimed at investigating the effects of an artificial head position-based tongue-placed electrotactile biofeedback on postural control during quiet standing under different somatosensory conditions from the support surface. Eight young healthy adults were asked to stand as immobile as possible with their eyes closed on two Firm and Foam support surface conditions executed in two conditions of No-biofeedback and Biofeedback. In the Foam condition, a 6-cm thick foam support surface was placed under the subjects' feet to alter the quality and/or quantity of somatosensory information at the plantar sole and the ankle. The underlying principle of the biofeedback consisted of providing supplementary information about the head orientation with respect to gravitational vertical through electrical stimulation of the tongue. Centre of foot pressure (CoP) displacements were recorded using a force platform. Larger CoP displacements were observed in the Foam than Firm conditions in the two conditions of No-biofeedback and Biofeedback. Interestingly, this destabilizing effect was less accentuated in the Biofeedback than No-biofeedback condition. In accordance with the sensory re-weighting hypothesis for balance control, the present findings evidence that the availability of the central nervous system to integrate an artificial head orientation information delivered through electrical stimulation of the tongue to limit the postural perturbation induced by alteration of somatosensory input from the support surface

Re-weighting of somatosensory inputs from the foot and the ankle for controlling posture during quiet standing following trunk extensor muscles fatigue

The present study focused on the effects of trunk extensor muscles fatigue on postural control during quiet standing under different somatosensory conditions from the foot and the ankle. With this aim, 20 young healthy adults were asked to stand as immobile as possible in two conditions of No fatigue and Fatigue of trunk extensor muscles. In Experiment 1 (n = 10), somatosensation from the foot and the ankle was degraded by standing on a foam surface. In Experiment 2 (n = 10), somatosensation from the foot and ankle was facilitated through the increased cutaneous feedback at the foot and ankle provided by strips of athletic tape applied across both ankle joints. The centre of foot pressure displacements (CoP) were recorded using a force platform. The results showed that (1) trunk extensor muscles fatigue increased CoP displacements under normal somatosensatory conditions (Experiment 1 and Experiment 2), (2) this destabilizing effect was exacerbated when somatosensation from the foot and the ankle was degraded (Experiment 1), and (3) this destabilizing effect was mitigated when somatosensation from the foot and the ankle was facilitated (Experiment 2). Altogether, the present findings evidenced re-weighting of sensory cues for controlling posture during quiet standing following trunk extensor muscles fatigue by increasing the reliance on the somatosensory inputs from the foot and the ankle. This could have implications in clinical and rehabilitative areas

Postural control during quiet standing following cervical muscular fatigue: effects of changes in sensory inputs

The purpose of the present experiment was to investigate the effects of cervical muscular fatigue on postural control during quiet standing under different conditions of reliability and/or availability of somatosensory inputs from the plantar soles and the ankles and visual information. To this aim, 14 young healthy adults were asked to sway as little as possible in three sensory conditions (No vision, No vision-Foam support and Vision) executed in two conditions of No fatigue and Fatigue of the scapula elevator muscles. Centre of foot pressure (CoP) displacements were recorded using a force platform. Results showed that (1) the cervical muscular fatigue yielded increased CoP displacements in the absence of vision, (2) this effect was more accentuated when somatosensation was degraded by standing on a foam surface and (3) the availability of vision allowed the individuals to suppress this destabilising effect. On the whole, these findings not only stress the importance of intact cervical neuromuscular function on postural control during quiet standing, but also suggest a reweigthing of sensory cues in balance control following cervical muscular fatigue by increasing the reliance on the somatosensory inputs from the plantar soles and the ankles and visual information

Differential postural effects of plantar-flexor muscles fatigue under normal, altered and improved vestibular and neck somatosensory conditions

The aim of the present study was to assess the effects of plantar-flexor muscles fatigue on postural control during quiet standing under normal, altered and improved vestibular and neck somatosensory conditions. To address this objective, young male university students were asked to stand upright as still as possible with their eyes closed in two conditions of No Fatigue and Fatigue of the plantar-flexor muscles. In Experiment 1 (n=15), the postural task was executed in two Neutral head and Head tilted backward postures, recognized to degrade vestibular and neck somatosensory information. In Experiment 2 (n=15), the postural task was executed in two conditions of No tactile and Tactile stimulation of the neck provided by the application of strips of adhesive bandage to the skin over and around the neck. Centre of foot pressure displacements were recorded using a force platform. Results showed that (1) the Fatigue condition yielded increased CoP displacements relative to the No Fatigue condition (Experiment 1 and Experiment 2), (2) this destabilizing effect was more accentuated in the Head tilted backward posture than Neutral head posture (Experiment 1) and (3) this destabilizing effect was less accentuated in the condition of Tactile stimulation than that of No tactile stimulation of the neck (Experiment 2). In the context of the multisensory control of balance, these results suggest an increased reliance on vestibular and neck somatosensory information for controlling posture during quiet standing in condition of altered ankle neuromuscular function

Inter-individual variability in sensory weighting of a plantar pressure-based, tongue-placed tactile biofeedback for controlling posture

The purpose of the present experiment was to investigate whether the sensory weighting of a plantar pressure-based, tongue-placed tactile biofeedback for controlling posture could be subject to inter-individual variability. To achieve this goal, 60 young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. Centre of foot pressure (CoP) displacements were recorded using a force platform. Overall, results showed reduced CoP displacements in the Biofeedback relative to the No-biofeedback condition, evidencing the ability of the central nervous system to efficiently integrate an artificial plantar-based, tongue-placed tactile biofeedback for controlling posture during quiet standing. Results further showed a significant positive correlation between the CoP displacements measured in the No-biofeedback condition and the decrease in the CoP displacements induced by the use of the biofeedback. In other words, the degree of postural stabilization appeared to depend on each subject's balance control capabilities, the biofeedback yielding a greater stabilizing effect in subjects exhibiting the largest CoP displacements when standing in the No-biofeedback condition. On the whole, by evidencing a significant inter-individual variability in sensory weighting of an additional tactile information related to foot sole pressure distribution for controlling posture, the present findings underscore the need and the necessity to address the issue of inter-individual variability in the field of neuroscience