Vestibular and proprioceptive contributions to human balance corrections: aiding these with prosthetic feedback

Effects of flooring on static and dynamic balance in young and older adults

BACKGROUND

Reducing fall-related injuries is difficult due to the multi-factorial nature of falls, and challenges in implementing injury-preventative strategies. While safety floors are effective at absorbing energy and reducing fall-related impact forces, the low stiffness component of these floors may impair an individual's balance and mobility, thereby increasing fall risk.

RESEARCH QUESTION

Therefore, the objective of this study was to investigate the influence of compliant flooring (i.e., safety flooring) on balance and mobility in young and older adults.

METHODS

Kinematics were measured with inertial measurement units from 20 young and 10 older adults. Static balance was evaluated during quiet stance on three flooring surfaces (traditional, safety, foam) with three stance positions (regular, tandem, one-legged). Mobility was evaluated using the 3 m timed-up-and-go test on two flooring surfaces (traditional, safety).

RESULTS

All participants were able to complete quiet standing trials on normal and safety flooring surfaces; however, most older adults could not complete one-legged stance trials or standing on foam. Significant age-related effects were observed for several balance and mobility tasks, particularly during the more challenging tandem stance condition, and the dynamic timed-up-and-go mobility test. In contrast, the introduction of safety flooring (compared to traditional flooring) had limited effects on balance/mobility (1 of 16 outcome variables showed negative effects).

SIGNIFICANCE

Overall, the findings demonstrate minimal effects of a novel safety floor compared to the age-related differences, and provide insights to assist researchers, consumers, and industry stakeholders in the development of environments that support safe movement and maintained independence for older adults.

Enhancement of Anticipatory Postural Adjustments by Virtual Reality in Older Adults with Cognitive and Motor Deficits: A Randomised Trial

BACKGROUND

Postural activities involved in balance control integrate the anticipatory postural adjustments (APA) that stabilize balance and posture, facilitating arm movements and walking initiation and allowing an optimal coordination between posture and movement. Several studies reported the significant benefits of virtual reality (VR) exercises in frail older adults to decrease the anxiety of falling and to induce improvements in behavioural and cognitive abilities in rehabilitation processes. The aim of this study was thus to test the efficiency of a VR system on the enhancement of the APA period, compared to the use of a Nintendo Wii system.

METHODS

Frail older adults (n = 37) were included in this study who were randomized and divided into a VR exercises group (VR group) or a control group using the Nintendo Wii system (CTRL group). Finally, 22 patients were included in the data treatment. APA were studied through muscular activation timings measured with electromyographic activities. The functional reach test, the gait speed, and the time up and go were also evaluated before and after a 3-week training phase.

RESULTS AND DISCUSSION

As the main results, the training phase with VR improved the APA and the functional reach test score along the antero-posterior axis. Together, these results highlight the ability of a VR training phase to induce neuromuscular adaptations during the APA period in frail older adults. Then, it underlines the effective transfer from learning carried out during the VR training movements to control balance abilities in a more daily life context.

Correlations Between Multi-plane vHIT Responses and Balance Control After Onset of an Acute Unilateral Peripheral Vestibular Deficit

OBJECTIVE

Previous studies reported that balance deficits in pitch (sagittal) and roll (lateral) planes during stance and gait after onset of an acute unilateral peripheral vestibular deficit (aUPVD) due to vestibular neuritis are weakly correlated with deficits in commonly explored lateral canal vestibular ocular reflex (VOR) responses. Theoretically, stronger correlations with roll and pitch balance deficits could be expected for vertical canal VOR responses. Therefore, we investigated these correlations.

SETTING

University Hospital.

STUDY DESIGN

Retrospective case review.

PATIENTS

Thirty three patients examined on average 5 days following onset of aUPVD.

MAIN OUTCOME MEASURES

Video head impulse test (vHIT) VOR gains in each vertical canal plane were converted to roll and pitch response asymmetries and correlated with patients' roll and pitch balance control measured during stance and gait with body-worn gyroscopes mounted at lumbar 1 to 3.

RESULTS

Mean caloric canal paresis was 92 ± 12%. Deficit side lateral vHIT mean gain was 0.4 ± 0.12, anterior gain 0.44 ± 0.18, and posterior gain, greater, 0.69 ± 0.15. Lateral VOR response gain asymmetries (37.2 ± 11.0%) were greater than roll VOR asymmetries calculated from all four vertical canal vHIT gains (16.2 ± 10.2%, p < 0.0001) and correlated (R = 0.56, p = 0.002). Pitch gain VOR asymmetries were less (4.9 ± 9.9%, p < 0.0001). All gait, but no stance, trunk roll angular velocity measures were correlated (p ≤ 0.03) with VOR roll asymmetries.

CONCLUSIONS

This report links roll balance control deficits during gait with roll VOR deficits and emphasises the need to perform anterior canal vHIT to judge effects of an aUPVD on balance control. Pitch VOR asymmetries were weakly affected by vestibular neuritis.

The effects of a 6-month moderate-intensity Hatha yoga-based training program on health-related fitness in middle-aged sedentary women: a randomized controlled study

BACKGROUND

There is paucity of data examining the effectiveness of long-term Hatha yoga-based (HY) programs focused on the health-related fitness (H-RF) of asymptomatic, sedentary women. The purpose of this study was to examine the effects of a 6-month HY-based training program on H-RF components in sedentary middle-aged women.

METHODS

Eighty sedentary women were randomly assigned into either the HY group (HYG) (N.=42) or the control group (CG) (N.=38). The 6-month HYG program involved a progressive series of Vinyasa Flow poses performed 3 times/week for 60 minutes (40 minutes within the exercise zone of 60-75% HR<inf>max</inf>). The CG participants did not undergo any physical training or education. Health-related fitness parameters included measures of pre- and post-training: body composition, muscular strength and maximal voluntary isometric torques of elbow flexors and knee extensors, cardio-respiratory fitness, lower back and hamstring flexibility and a static-dynamic balance.

RESULTS

Two-way mixed design ANOVA revealed significant main effects for all the indicators of H-RF. Tukey post-hoc tests confirmed that the HYG demonstrated significant improvements in every variable tested. Examples of the benefits achieved include (all P<.001): an average loss of 1.03 kg and a 4.82% decrease in body fat, 14.6% and 13.1% gains in isometric strength of the knee extensors and elbow flexors respectively, an increase in relative VO<inf>2max</inf> of 6.1% (33.12±5.30 to 35.14±4.82 mL/kg/min), a 4-cm or 10.4% increase in their MSAR, and an average improved Balance Index of 5.6 mm/s. Reversely, the CG showed non-significant changes in H-RF variables (all P>0.05; percent range from -1.4% to 1.1%).

CONCLUSIONS

By participating in a moderate-intensity 6-month HY-based training program, middle-aged women can significantly improve their HR-F status. The application of progressive target heart rate goals facilitated greater than expected improvements in cardio-respiratory fitness and improvements in body composition.

The Effect of Unilateral Vestibular Loss on Standing Balance During Postural Threat

OBJECTIVE

Vestibular deficit patients have an increased fall risk and fear of falling. Postural threat, known to increase balance-related fear and anxiety, influences vestibular gains during quiet standing in young healthy adults. The current study examined whether there is a similar relationship for peripheral unilateral vestibular loss (UVL) patients in comparison to age-matched healthy controls (HC).

SETTING

University laboratory.

STUDY DESIGN

Prospective laboratory study.

PATIENTS AND CONTROLS

Eleven UVL patients, nine with vestibular neurectomy. Eleven aged-matched HCs.

MAIN OUTCOME MEASURES

Subjects stood on a hydraulic lift placed at two heights: low (0.8 m, away from the edge) and high (3.2 m, at the edge). Amplitude (root mean square), mean power frequency (MPF), and mean position were analyzed for center of foot pressure (COP) and 90% ranges for angle amplitude and velocity for trunk sway.

RESULTS

Group interactions were strongest for anterior-posterior (AP) COP and trunk pitch angle. AP lean away from the edge was greater in HCs than UVLs. HCs, but not UVLs had a decrease in root mean square AP COP with height. Trunk pitch sway was changed similarly. Both groups had increased trunk pitch velocity at height. Changes with height were less for roll: MPF of lateral COP increased with height for UVLs with no changes for HCs, and trunk roll amplitude decreased for both groups.

CONCLUSIONS

This report provides evidence for a differential effect of height induced postural threat on balance control between UVLs and HCs presumably due to the reduced vestibular-spinal gain in UVL subjects.

The effects of the three-dimensional active trunk training exercise on trunk control ability, trunk muscle strength, and balance ability in sub-acute stroke patients: A randomized controlled pilot study

BACKGROUND

Trunk control ability has been identified as an important early predictor of functional recovery after stroke.

OBJECTIVE

Our study aimed to investigate the effects of three-dimensional active trunk training exercise on trunk control ability, trunk muscle strength, and balance ability in sub-acute stroke patients.

METHODS

Twenty-four sub-acute stroke patients were randomly assigned to an experimental (n= 12) or control (n= 12) group. The experimental group (EG) performed three-dimensional active trunk training exercises using the Space Balance 3D system, while the control group (CG) performed only general trunk training exercises five times per week, for a total of three weeks. The Trunk Impairment Scale (TIS), trunk muscle strength, balance ability using the Space Balance 3D system, and Brunel Balance Assessment (BBA) scores were assessed before and after the intervention.

RESULTS

Pre-to-post intervention improvement was noted in all outcome measures for both groups (p< 0.05). Post intervention, the TIS, trunk muscle strength, static balance, and BBA scores were significantly higher in the EG than those in the CG (p< 0.05).

CONCLUSION

Our study suggests that the three-dimensional active trunk training exercise may be more effective compared to the general trunk training exercise in improving trunk control ability, trunk muscle strength, and balance ability in sub-acute stroke patients.

Biofeedback Systems for Gait Rehabilitation of Individuals with Lower-Limb Amputation: A Systematic Review

Individuals with lower-limb amputation often have gait deficits and diminished mobility function. Biofeedback systems have the potential to improve gait rehabilitation outcomes. Research on biofeedback has steadily increased in recent decades, representing the growing interest toward this topic. This systematic review highlights the methodological designs, main technical and clinical challenges, and evidence relating to the effectiveness of biofeedback systems for gait rehabilitation. This review provides insights for developing an effective, robust, and user-friendly wearable biofeedback system. The literature search was conducted on six databases and 31 full-text articles were included in this review. Most studies found biofeedback to be effective in improving gait. Biofeedback was most commonly concurrently provided and related to limb loading and symmetry ratios for stance or step time. Visual feedback was the most used modality, followed by auditory and haptic. Biofeedback must not be obtrusive and ideally provide a level of enjoyment to the user. Biofeedback appears to be most effective during the early stages of rehabilitation but presents some usability challenges when applied to the elderly. More research is needed on younger populations and higher amputation levels, understanding retention as well as the relationship between training intensity and performance.

Parameters of the crossing points between center of pressure and center of mass signals are potential markers of postural control efficiency

Posturographic signals were recorded for 384 subjects of different ages and with old persons with gait disturbances. Four conditions were used: Eyes Open/Closed vs. Head Normal/Bent Back. ‘Center of Pressure’ (CoP) signals were decomposed into ‘Center of Mass’ (CoM) and the remaining difference between Center of Pressure and Center of Mass (CoPM). The Zero-Crossing points in which the Center of Mass and Center of Pressure paths cross each other have been extracted. Velocity of CoM, velocity of CoPM and acceleration of CoPM in Zero-Crossing points were analyzed to be potential markers of balance efficiency. Three factors causing the deterioration of balance quality were analyzed: closing eyes, bending the head back and patient age. The influence of the given factors was measured using the significance p of the t-Student test and Cohen's d effect size and applied to differences for the logarithms of three of the mentioned above variables measured without and with the given deteriorating factor. In the majority of comparisons, the proposed new parameters of balance quality possessed higher statistical power to detect deteriorated balance quality than the standard parameters: standard deviation of the signal and ellipse area covering 90% of the signal envelope. Most valuable are the velocity and acceleration of CoPM for the medio-lateral direction. Logarithms of the analyzed parameters are proposed to be used in analyses because they possess normal or close to normal distribution and they are less sensitive to single high values occurring often in measurements.

Vibro-tactile and auditory balance biofeedback changes muscle activity patterns: Possible implications for vestibular implants

BACKGROUND

The two different types of balance prostheses being developed, implants and vibro-tactile/auditory feedback prostheses, rely on different measures to prove efficacy (those based on vestibular ocular reflexes versus balance control, respectively). Here we provide evidence that examining muscle activity might provide a useful alternative for both.

METHODS

The muscle activity of 6 bilateral vestibular loss (BVL) and 7 age-matched healthy controls (HC) was examined while standing eyes closed on a foam support surface. Pelvis and upper trunk angular movements were recorded in the roll and pitch planes. Surface EMG was recorded from the lower leg, trunk and upper arm muscles. BVL subjects were first assessed without feedback of pelvis sway, then received training with combined vibro-tactile and auditory feedback, before being re-assessed with feedback.

RESULTS

Feedback reduced the amplitudes of pelvis and shoulder sway to values of HC without feedback. Both the level of background EMG activity and the EMG area amplitudes changed when feedback was provided in a manner consistent with the reduced amplitude modulation of muscle synergies of HC.

CONCLUSIONS

The results of this study indicate that changed muscle synergy amplitudes underlie improvements in sway achieved by BVL subjects. The concept of this investigation may provide a means to prove efficacy for different types of balance prostheses, including implants.

A Longitudinal Assessment Of Standing Balance In Healthy Adults

Background/Study Context: The study was a longitudinal assessment of age-related changes in standing balance and response strategy usage in healthy adults.

METHODS

Balance of 17 individuals with a mean age of 44.5 years was assessed and then reassessed 19.5 years later. Participants stood on computer-controlled dual-force platforms enclosed by a visual surround and completed six tests in which visual and/or somatosensory information was systematically degraded or eliminated.

RESULTS

Results for each test and a weighted composite balance score revealed no significant change in postural control over the time period studied. However, response strategy scores indicated some significant change with age. Specifically, compensatory movement corrections about the ankle complex increased when standing on a stable support surface with and without vision, and hip-centered corrections were prominent when standing on an unstable surface with eyes open or closed.

CONCLUSION

Increased reliance on response strategy usage with time is interpreted as a compensatory adjustment to age-related increases in postural instability and accounts for the absence of any change in standing balance under different conditions of sensory input.

Tai Chi with mental imagery theory improves soleus H-reflex and nerve conduction velocity in patients with type 2 diabetes

OBJECTIVES

Diabetes is a disease that leads to damage to the peripheral nerves which may eventually cause balance instability. The purpose of this study was to determine the effect of 8 weeks of Tai Chi (TC) training combined with mental imagery (MI) on soleus H-reflex and nerve conduction velocity (NCV) of the sural and superficial peroneal nerves in people with diabetes.

DESIGNS

Quasi-experimental, one group pretest-posttest design.

SETTING

Human Research Laboratory.

INTERVENTIONS

A series of Yang style of Tai Chi classes with mental imagery, one hour, two sessions per week for 8 weeks was done.

MAIN OUTCOME MEASURES

The Activities-specific Balance Confidence (ABC) Scale, Functional Reach Test (FRT), and One Leg Standing Test (OLS) were measured as functional data. Hoffman reflex (H-reflex), and sural and superficial peroneal NCV were measured as main outcomes.

RESULTS

All functional outcomes measures were significantly improved after the intervention (p<0.01). In the H-reflex, there was a significant increase in amplitude (μV) after completing 8 weeks of TC exercise (p=0.02). In the sural nerve, the velocity (p=0.01), amplitude (p=0.01), and latency (p=0.01) were significantly improved between pre and post-test. In the superficial peroneal nerve, significant improvements were observed in (p=0.02) and latency (p=0.01), but not in amplitude (μV) (p>0.05).

CONCLUSIONS

Combining TC intervention with MI theory showed an improvement in the H-reflex and NCV tests, which suggests improved balance and walking stability.

Benefits of multi-session balance and gait training with multi-modal biofeedback in healthy older adults

Real-time balance-relevant biofeedback from a wearable sensor can improve balance in many patient populations, however, it is unknown if balance training with biofeedback has lasting benefits for healthy older adults once training is completed and biofeedback removed. This study was designed to determine if multi-session balance training with and without biofeedback leads to changes in balance performance in healthy older adults; and if changes persist after training. 36 participants (age 60-88) were randomly divided into two groups. Both groups trained on seven stance and gait tasks for 2 consecutive weeks (3×/week) while trunk angular sway and task duration were monitored. One group received real-time multi-modal biofeedback of trunk sway and a control group trained without biofeedback. Training effects were assessed at the last training session, with biofeedback available to the feedback group. Post-training effects (without biofeedback) were assessed immediately after, 1-week, and 1-month post-training. Both groups demonstrated training effects; participants swayed less when standing on foam with eyes closed (EC), maintained tandem-stance EC longer, and completed 8 tandem-steps EC faster and with less sway at the last training session. Changes in sway and duration, indicative of faster walking, were also observed after training for other gait tasks. While changes in walking speed persisted post-training, few other post-training effects were observed. These data suggest there is little added benefit to balance training with biofeedback, beyond training without, in healthy older adults. However, transient use of wearable balance biofeedback systems as balance aides remains beneficial for challenging balance situations and some clinical populations.

VOLUME OF CONVEX HULL: A TECHNIQUE FOR QUANTIFYING HUMAN POSTURAL STABILITY

Many disorders, such as nervous system disorders, can affect orientation of the body segments in 3D space negatively. Patients with these disorders often show body segments instability during stance tasks. Nowadays, 3-axis gyroscopes are about to be used to measure postural stability. The main objective of the paper is to describe a method which would be suitable for quantifying postural stability and 3D movement as a whole using a cheap 3-axis gyroscope. New method based on the volume of a 3D convex hull (CH) obtained by plotting pitch, roll and yaw angles versus each other was proposed for quantitative evaluation of 3D trunk sway. The sway was measured while patients with degenerative cerebellar disorder (Pts) and eleven healthy subjects (HSs) performed quiet stance on a firm surface (FiS) and foam surface (FoS) with open eyes (OE) and closed eyes (CE). The CH was used to identify differences in balance control, and there were significant differences found between the two groups. The median (Mdn) of the volume of Pts with OE on FiS is four times larger than the Mdn of the volume of HS with OE on FiS. The Mdn of the volume of Pts with CE on FoS is 80 times larger than the Mdn of the volume of HS with CE on FoS. It was therefore found that the volume of CH is suitable for quantifying postural sway and identifying differences in balance control.

Hatha yoga on body balance

Background:

A good body balance requires a proper function of vestibular, visual, and somatosensory systems which can be reach with exercise practice and/or yoga.

Aim:

To determine the effects of a 5-month hatha yoga training program on body balance in young adults.

Materials and Methods:

This study used a controlled, nonrandomized design, where the experimental group underwent a 5-month training program and were then compared with the control group that had a sedentary lifestyle. A convenience sample of 34 out of 40 men aged 25-55 years old (34.0 ± 0.9) were deemed eligible for this study. They were randomly divided into two groups: Experimental and control groups. Subjects in the experimental group were engaged in 60 min sessions of hatha yoga three times a week for 5 months. We evaluated postural control by measuring the limit of stability and velocity of oscillation (VOS) in three conditions of the balance rehabilitation unit (BRU) and through field procedures (four position, plane, flamingo, hopscotch, and dynamic test).

Results:

We observed differences (P < 0.05) in postintervention scores between the groups regardless of BRU parameters and field procedures (except for flamingo) even after adjusting for preintervention scores, suggesting that these changes were induced by hatha yoga training. The partial eta squared on BRU parameters ranged from 0.78 (VOS1)-0.97 (COP2), and from 0.00 (flamingo)-0.94 (four position) for the field procedures.

Conclusions:

Our results provide substantial evidence that postural control in healthy young adults can be improved through practicing hatha yoga.

The effects of pilates mat exercise on the balance ability of elderly females

[Purpose] The purpose of this study was to examine the effects of Pilates exercise on a mat and balance exercise on an unstable base of support for trunk stability on the balance ability of elderly females. [Subjects and Methods] Forty elderly women aged 65 or older were equally assigned to a Pilates mat exercise (PME) group and an unstable support surface exercise (USSE) group. They conducted exercise three times per week for 12 weeks for 40 minutes each time. In order to examine balance, sway length and the speed of the center of foot pressure were measured for one minute, and in order to examine dynamic balance, the Timed Up and Go (TUG) test was conducted. [Results] After the intervention, sway length, sway speed, and TUG significantly decreased in both groups. A comparison of sway speed after the intervention between the two groups revealed that the PME group showed larger decreases than the USSE group. [Conclusion] PME and USSE elicited significant effects on the static and dynamic balance of elderly female subjects, suggesting that those exercises are effective at enhancing the balance ability of this group of subjects. However, the Pilates mat exercise is regarded as being safer than exercise on an unstable base of support.

The effect of prosthetic feedback on the strategies and synergies used by vestibular loss subjects to control stance

Background

This study investigated changes in stance movement strategies and muscle synergies when bilateral peripheral vestibular loss (BVL) subjects are provided feedback of pelvis sway angle.

Methods

Six BVL (all male) and 7 age-matched male healthy control (HC) subjects performed 3 stance tasks: standing feet hip width apart, eyes closed, on a firm and foam surface, and eyes open on foam. Pelvis and upper trunk movements were recorded in the roll and pitch planes. Surface EMG was recorded from pairs of antagonistic muscles at the lower leg, trunk and upper arm. Subjects were first assessed without feedback. Then, they received training with vibrotactile, auditory, and fall-warning visual feedback during stance tasks before being reassessed with feedback.

Results

Feedback reduced pelvis sway angle displacements to values of HCs for all tasks. Movement strategies were reduced in amplitude but not otherwise changed by feedback. These strategies were not different from those of HCs before or after use of feedback. Low frequency motion was in-phase and high frequency motion anti-phasic. Feedback reduced amplitudes of EMG, activity ratios (synergies) of antagonistic muscle pairs and slightly reduced baseline muscle activity.

Conclusions

This is the first study demonstrating how vestibular loss subjects achieve a reduction of sway during stance with prosthetic feedback. Unchanged movement strategies with reduced amplitudes are achieved with improved antagonistic muscle synergies. This study suggests that both body movement and muscle measures could be explored when choosing feedback variables, feedback location, and patient groups for prosthetic devices which reduce sway of those with a tendency to fall.

Short-term retention effect of rehabilitation using head position-based electrotactile feedback to the tongue: influence of vestibular loss and old-age

Our objective was to evaluate whether the severity of vestibular loss and old-age (>65) affect a patient's ability to benefit from training using head-position based, tongue-placed electrotactile feedback. Seventy-one chronic dizzy patients, who had reached a plateau with their conventional rehabilitation, followed six 1-h training sessions during 4 consecutive days (once on days 1 and 4, twice on days 2 and 3). They presented bilateral vestibular areflexia (BVA), bilateral vestibular losses (BVL), unilateral vestibular areflexia or unilateral vestibular losses and were divided into two age-subgroups (≤65 and >65). Posturographic assessments were performed without the device, 4h before and after the training. Patients were tested with eyes opened and eyes closed (EC) on static and dynamic (passively tilting) platforms. The studied posturographic scores improved significantly, especially under test conditions restricting either visual or somatosensory input. This 4-h retention effect was greater in older compared to younger patients and was proportional to the degree of vestibular loss, patients with increased vestibular losses showing greater improvements. In bilateral patients, who constantly fell under dynamic-EC condition at the baseline, the therapy effect was expressed by disappearance of falls in BVL and significant prolongation in time-to-fall in BVA subgroups. Globally, our data showed that short training with head-position based, tongue-placed electrotactile biofeedback improves balance in chronic vestibulopathic patients some 16.74% beyond that achieved with standard balance physiotherapy. Further studies with longer use of this biofeedback are needed to investigate whether this approach could have long-lasting retention effect on balance and quality of life.

Effects of biofeedback on secondary-task response time and postural stability in older adults

Real-time single- and multiple-axis vibrotactile feedback of trunk motion has been shown to significantly decrease mean trunk tilt and decrease time spent outside a no vibrotactile feedback zone (dead zone) in older adults within a laboratory setting. This study aimed to determine if these improvements can translate into everyday use, during which other tasks may simultaneously demand attention. A dual-task paradigm was used in which 10 community-dwelling older adults were asked to perform standing trials in the presence of a secondary task (verbal or push-button), vibrotactile feedback, or both (dual-task). Results show that subjects significantly increased the percentage of time inside the dead zone when feedback was provided compared to when it was not during both verbal (+13.6%) and push-button (+10.1%) secondary tasks. Providing feedback also decreased RMS of trunk tilt during both secondary tasks (verbal: -0.129°; push-button: -0.138°). However, response times for secondary tasks increased (verbal: +119 ms; push-button: +110 ms) when feedback was provided. These results suggest that while vibrotactile feedback does increase attentional load in older adults, it can still be used effectively to improve postural metrics in high cognitive load situations.

Strategies and synergies underlying replacement of vestibular function with prosthetic feedback

This study investigated changes in movement strategies and muscle synergies when bilateral peripheral vestibular loss (BVL) subjects are provided prosthetic feedback of their pelvis sway during stance. Six BVL subjects performed 3, for them, difficult stance tasks: standing eyes closed, on a firm surface, on a foam surface, and standing eyes open on foam. Movement strategies were recorded as roll and pitch ratios of upper and lower body velocities with body-worn gyroscopes. Surface EMG recordings were taken from two pairs of antagonistic, lower leg and trunk muscles in order to note synergy changes with feedback. Subjects were first assessed without feedback. Then they were provided stance training with vibro-tactile and auditory feedback of pelvis angle sway, and finally reassessed with the same feedback active. For analysis of movement strategies, angle values integrated from angular velocity samples, were split into 3 frequency bands (&#60;0.7, 0.7-3, and >3 Hz). Feedback caused a reduction in pelvis sway angle displacements to values of age-matched healthy controls (HC) for all tasks. Pelvis sway velocity was only reduced for the task with largest angle displacements, standing eyes closed on foam. Movement strategies in each frequency band examined were unaltered by feedback, except for amplitude, and were not different from those of HCs before or after use of feedback. Low frequency motion was in-phase as if the upper and lower body moved as an inverted pendulum, high frequency motion anti-phasic. Amplitudes of EMG were reduced with feedback. Synergies recorded in the form of activity ratios of antagonistic muscle pairs were reduced with feedback. This is the first study that demonstrates how vestibular loss subjects achieve a reduction of sway during stance with prosthetic feedback. Unchanged movement strategies with reduced amplitudes are achieved with reduced antagonistic muscle synergies. This study has implications for the choice of feedback parameters (angle or velocity) and patient groups when using prosthetic devices to reduce sway of those with a tendency to fall.

Effects of an exercise program on balance and trunk proprioception in older adults with diabetic neuropathies

BACKGROUND

Diabetes is the most common cause of peripheral neuropathies. No definitive treatment for diabetic neuropathies has been reported, and very few studies have been published on the role of exercise in reducing either the symptoms or incidence of diabetic neuropathies.

METHODS

This study assessed the effects of an exercise program on balance and trunk proprioception in older adults with diabetic neuropathies. Thirty-eight patients with diabetes having peripheral neuropathies were enrolled, randomized, and subdivided in two groups: an experimental group of 19 participants with diabetes (72.9 ± 5.6 years old) and a control group of 19 participants with diabetes (73.2 ± 5.4 years old). Both groups received health education on diabetes for 50 min/week for 8 weeks. The experimental group practiced an additional balance exercise program for 60 min, two times a week. The exercise training was performed two times per week for 8 weeks. Results were evaluated by both static and dynamic balance and trunk proprioception.

RESULTS

Postural sway significantly decreased (P < 0.05), the one-leg stance test significantly increased (P < 0.05), and dynamic balance from the Berg Balance Scale, Functional Reach Test, Timed Up and Go test, and 10-m walking time improved significantly after balance exercise (P < 0.05). Trunk repositioning errors also decreased with training (P < 0.05).

CONCLUSION

The balance exercise program improved balance and trunk proprioception. These results suggested that a balance exercise is suitable for individuals with diabetic neuropathy.