Foam Support Surface Research Articles

Changes in multi-segmented body movements and EMG activity while standing on firm and foam support surfaces

Postural control ensures stability during both static posture and locomotion by initiating corrective adjustments in body movement. This is particularly important when the conditions of the support surface change. We investigated the effects of standing on a compliant foam surface using 12 normal subjects (mean age 26 years) in terms of: linear movements at the head, shoulder, hip and knee; EMG activity of the tibialis anterior and gastrocnemius muscles and torques towards the support surface. As subjects repeated the trials with eyes open or closed, we were also able to determine the effects of vision on multi-segmented body movements during standing upon different support surface conditions. As expected, EMG activity, torque variance values and body movements at all measured positions increased significantly when standing on foam compared with the firm surface. Linear knee and hip movements increased more, relative to shoulder and head movements while standing on foam. Vision stabilized the head and shoulder movements more than hip and knee movements while standing on foam support surface. Moreover, vision significantly reduced the tibialis anterior EMG activity and torque variance during the trials involving foam. In conclusion, the foam support surface increased corrective muscle and torque activity, and changed the firm-surface multi-segmented body movement pattern. Vision improved the ability of postural control to handle compliant surface conditions. Several essential features of postural control have been found from recording movements from multiple points on the body, synchronized with recording torque and EMG.

Dynamic posture assessment in patients with peripheral vestibulopathy

ObjectiveTo assess the effects on balance of different strategies to create sensory conflict.Material and MethodsTwo different systems of dynamic posturography were compared: computerized dynamic posturography and a static platform on which different visual and support conditions were used. The study was performed in 127 patients with dizziness of a peripheral vestibular origin.ResultsWhen patients stood on a foam support surface, the length and area of the center-of-pressure excursions increased. Interestingly, optokinetic stimulation evoked a longer length and a wider area of the center-of-pressure excursions in patients with a combined vestibular and visual deficit pattern than when they kept their eyes closed. This was opposite to the effect observed in patients with a pattern indicative of a vestibular deficit alone.ConclusionThe effects of visual stimulation on balance in patients with unilateral vestibulopathy reflect the type of sensory deficit, and can be considered to be specific to such a deficit.

Improvements in Trunk Sway Observed for Stance and Gait Tasks during Recovery from an Acute Unilateral Peripheral Vestibular Deficit

Objectives: Our aim was to track improvements in postural control during recovery from an acute unilateral peripheral vestibular deficit (UVL), presumably due to vestibular neuritis, and to determine if recovery rates were different for stance and gait tasks. Postural control was quantified using simple measurements of trunk sway: amplitudes of trunk sway angle and angular velocity, in the roll and pitch directions as well as task duration, were examined for a battery of stance and gait tasks. These measures were collected at the onset of the deficit and then 3 weeks and 3 months later. Study Design: A repeated-measures design was used for UVL subjects and age-matched healthy controls. Stance tasks involved standing on 1 or 2 legs with eyes open or closed. Gait tasks consisted of tandem gait, walking normally with eyes closed, or with the head rotating or head pitching, walking up and down stairs and walking over a series of low barriers. Stance and tandem gait tasks were repeated using a foam support surface instead of a normal floor. Patients: Twenty-eight patients with acute UVL were examined. Main Outcome Measures: The range of trunk sway angular displacement and angular velocity in the pitch and roll directions was measured for each task in addition to task duration. The measures were compared with those of normal subjects. Results: The amplitudes of pitch trunk sway for 2-legged stance tasks with eyes closed underwent the greatest reduction 3 weeks after UVL onset. At 3 months, trunk sway was almost normal for all 2-legged stance tasks. One-legged stance tasks with eyes open showed a similar but slower improvement. Stance time without a fall showed a very rapid improvement for 1-legged tasks but was still shorter than that of normal subjects at 3 months. Trunk sway for the simple gait tasks was within normal range at 3 months; however, task duration was still longer than normal. More complex gait tasks, such as walking 8 tandem steps on foam or walking up and down stairs, showed no improvement in trunk roll sway at 3 months. A mix of variables from mainly gait tasks best identified a balance deficit due to UVL, with complex gait tasks becoming more important for identification purposes as compensation progressed. The accuracy of UVL identification with durations alone was 75% of the accuracy with combined trunk sway and duration measures. Conclusions: These data suggest that recovery of normal trunk control during the compensation process for unilateral vestibular hypofunction is more rapid for stance tasks than gait tasks. Even at 3 months, trunk sway for complex gait tasks was not normal. Thus, trunk sway for gait tasks provides a better insight into remaining deficits in balance control of vestibular-loss patients than the sway of stance tasks.

Kinematic analysis of the hip and trunk during bilateral stance on firm, foam, and multiaxial support surfaces

Objective. To differentiate hip and trunk motion during double-leg stance. Design. Trunk and hip angular position variances were measured on different support surfaces with and without vision. Background. Postural control results from motion about the hips and trunk during bilateral stance. While the hip joint has been studied extensively, information concerning relative amounts of hip and trunk motions during postural control is limited. Methods. Trunk flexion/extension, trunk lateral flexion, right and left hip flexion/extension and abduction/adduction angular position variances were assessed in 14 normal subjects using an electromagnetic tracking system during bilateral stance on firm, foam, and multiaxial support surfaces with and without vision. Results. Significantly greater amounts of motion occurred at all joints for the multiaxial-eyes closed condition compared to all other surface–vision conditions. No significant differences were found between any other surface–vision conditions. Within the multiaxial-eyes closed condition, right and left hip flexion/extension and abduction/adduction magnitudes were significantly greater than those of trunk flexion and lateral flexion, and left hip flexion/extension motion was significantly greater than that of the right hip. Conclusions. Postural control mechanisms involve similar amounts of motion at the hips and trunk, except for conditions under which a rigid base of support becomes unstable and vision is eliminated. Relevance These results suggest that the trunk and hips should be considered separately during kinematic analysis of postural control. This information may be useful in providing a more sensitive assessment of postural control to identify balance-related pathologies associated with stroke, concussion, and somatosensory deficits.

Trunk sway measures of postural stability during clinical balance tests: effects of a unilateral vestibular deficit.

This research evaluated whether quantified measures of trunk sway during clinical balance tasks are sensitive enough to identify a balance disorder and possibly specific enough to distinguish between different types of balance disorder. We used a light-weight, easy to attach, body-worn apparatus to measure trunk angular velocities in the roll and pitch planes during a number of stance and gait tasks similar to those of the Tinetti and CTSIB protocols. The tasks included standing on one or two legs both eyes-open and closed on a foam or firm support-surface, walking eight tandem steps, walking five steps while horizontally rotating or pitching the head, walking over low barriers, and up and down stairs. Tasks were sought, which when quantified might provide optimal screening for a balance pathology by comparing the test results of 15 patients with a well defined acute balance deficit (sudden unilateral vestibular loss (UVL)) with those of 26 patients with less severe chronic balance problems caused by a cerebellar-pontine-angle-tumour (CPAT) prior to surgery, and with those of 88 age- and sex-matched healthy subjects. The UVL patients demonstrated significantly greater than normal trunk sway for all two-legged stance tasks especially those performed with eyes closed on a foam support surface. Sway was also greater for walking while rotating or pitching the head, and for walking eight tandem steps on a foam support surface. Interestingly, the patients could perform gait tasks such as walking over barriers almost normally, however took longer. CPAT patients had trunk sway values intermediate between those of UVL patients and normals. A combination of trunk sway amplitude measurements (roll angle and pitch velocity) from the stance tasks of standing on two legs eyes closed on a foam support, standing eyes open on a normal support surface, as well as from the gait tasks of walking five steps while rotating, or pitching the head, and walking eight tandem steps on foam permitted a 97% correct recognition of a normal subject and a 93% correct recognition of an acute vestibular loss patient. Just over 50% of CPAT patients could be classified into a group with intermediate balance deficits, the rest were classified as normal. Our results indicate that measuring trunk sway in the form of roll angle and pitch angular velocity during five simple clinical tests of equilibrium, four of which probe both stance and gait control under more difficult sensory conditions, can reliably and quantitatively distinguish patients with a well defined balance deficit from healthy controls. Further, refinement of these trunk sway measuring techniques may be required if functions such as preliminary diagnosis rather than screening are to be attempted.

An assessment of foam support surfaces used in static stabilometry

We undertook this study to estimate the limits of agreement of repeated measures of static posturography on healthy adults and to assess the use of those limits on the interpretation of variations observed during vestibular rehabilitation of patients with chronic, peripheral vestibular disease.Twenty healthy adults and 30 vestibular patients accepted to participate. At baseline and at weeks 4, 6 and 8 of follow-up, posturography was performed with the eyes open or closed, while adding or not a layer of foam rubber to the base of support. The Dizziness Handicap Inventory was administered to patients prior to rehabilitation and at week 8.At baseline, a difference between groups was observed on the sway area (p < 0.05). Healthy subjects showed no statistical difference among the four recordings (repeatability of measurements from 85–100%). Vestibular patients showed differences among the four recordings on the area and the length/average speed of sway (p <0.05); individual differences from baseline exceeding the limits of agreement were observed on the sway area. A decrease on the Dizziness Handicap Inventory (≥18 points) was observed on 19 patients, from whom 12 (63, 95% CI 53–73%) showed a change on the sway area (eyes closed) that was larger than the limits of agreement.In healthy subjects, intra-subject repeated recordings of the area and the length/average speed of sway may be reliable at intervals of 4, 6 and 8 weeks. The sway area (without vision) may be a useful sway component, among others, to follow-up vestibular patients with chronic, peripheral disease during rehabilitation.