Loss of Peripheral Sensory Function Explains Much of the Increase in Postural Sway in Healthy Older Adults

Concentrating to avoid falling: interaction between peripheral sensory and central attentional demands during a postural stability limit task in sedentary seniors

Evidence suggests falls and postural instabilities among seniors are attributed to a decline in both the processing of afferent signals (e.g., proprioceptive, vestibular) and attentional resources. We investigated the interaction between the non-visual and attentional demands of postural control in sedentary seniors. Old and young adults performed a postural stability limit task involving a maximal voluntary leaning movement with and without vision as well as a cognitive-attentional subtraction task. These tasks were performed alone (single-task) or simultaneously (dual-task) to vary the sensory-attentional demands. The functional limits of stability were quantified as the maximum center of pressure excursion during voluntary leaning. Seniors showed significantly smaller limits of postural stability compared to young adults in all sensory-attentional conditions. However, surprisingly, both groups of subjects reduced their stability limits by a similar amount when vision was removed. Furthermore, they similarly decreased their anterior-posterior stability limits when concurrently performing the postural and the cognitive-attentional tasks with vision. The overall average cognitive performance of young adults was higher than seniors and was only slightly affected during dual-tasking. In contrast, older adults markedly degraded their cognitive performance from the single- to the dual-task situations, especially when vision was unavailable. Thus, their dual-task costs were higher than those of young adults and increased in the eyes-closed condition, when postural control relied more heavily on non-visual sensory signals. Our findings provide the first evidence that as posture approaches its stability limits, sedentary seniors allot increasingly large cognitive attentional resources to process critical sensory inputs.

Effects of free versus restricted arm movements on postural control in normal and modified sensory conditions in young and older adults

The purpose of this study was to explore the effects of arm movements on postural control when standing under different sensory conditions in healthy young and older adults. Fifteen young (mean ± SD age; 21.3 ± 4.2 years) and 15 older (mean ± SD age; 73.3 ± 5.0 years) adults completed the modified Romberg test, which uses four task manipulations (i.e. eyes open and eyes closed on a firm and foam surface) to compromise the fidelity of sensory feedback mechanisms. Each participant completed the tasks under two arm movement conditions: restricted and free arm movements. Centre of pressure (COP) range and frequency were calculated to characterise postural performance and strategy, respectively. Older adults showed greater COP range with restricted compared to free arm movements during all modified sensory conditions, with these effects most prominent in the medio-lateral (ML) plane (all p < .05, Cohen's d = 0.69-1.61). Compared to the free arm movement condition, there was an increase in ML displacement and frequency when arm movements were restricted during only the most challenging (i.e. vestibular dominant) task in young adults (all p < .05, d = 0.645-0.83). Finally, main age effects for the arm restriction cost (p < .05) indicates a greater reliance on an upper body strategy in older compared to young adults, independent of sensory availability/accuracy. These findings indicate that older adults compensate for the loss of accuracy in sensory input by increasing reliance on upper body movement strategies.

The 'Postural Rhythm' of the Ground Reaction Force during Upright Stance and Its Conversion to Body Sway-The Effect of Vision, Support Surface and Adaptation to Repeated Trials

The ground reaction force (GRF) recorded by a platform when a person stands upright lies at the interface between the neural networks controlling stance and the body sway deduced from centre of pressure (CoP) displacement. It can be decomposed into vertical (VGRF) and horizontal (HGRF) vectors. Few studies have addressed the modulation of the GRFs by the sensory conditions and their relationship with body sway. We reconsidered the features of the GRFs oscillations in healthy young subjects (n = 24) standing for 90 s, with the aim of characterising the possible effects of vision, support surface and adaptation to repeated trials, and the correspondence between HGRF and CoP time-series. We compared the frequency spectra of these variables with eyes open or closed on solid support surface (EOS, ECS) and on foam (EOF, ECF). All stance trials were repeated in a sequence of eight. Conditions were randomised across different days. The oscillations of the VGRF, HGRF and CoP differed between each other, as per the dominant frequency of their spectra (around 4 Hz, 0.8 Hz and <0.4 Hz, respectively) featuring a low-pass filter effect from VGRF to HGRF to CoP. GRF frequencies hardly changed as a function of the experimental conditions, including adaptation. CoP frequencies diminished to <0.2 Hz when vision was available on hard support surface. Amplitudes of both GRFs and CoP oscillations decreased in the order ECF > EOF > ECS ≈ EOS. Adaptation had no effect except in ECF condition. Specific rhythms of the GRFs do not transfer to the CoP frequency, whereas the magnitude of the forces acting on the ground ultimately determines body sway. The discrepancies in the time-series of the HGRF and CoP oscillations confirm that the body's oscillation mode cannot be dictated by the inverted pendulum model in any experimental conditions. The findings emphasise the robustness of the VGRF "postural rhythm" and its correspondence with the cortical theta rhythm, shed new insight on current principles of balance control and on understanding of upright stance in healthy and elderly people as well as on injury prevention and rehabilitation.

Older adults with slow sit to stand times show reduced temporal precision of audio-visual integration

Sustained integration of sensory inputs over increased temporal delays is associated with reduced cognitive and physical functioning in older adults and adverse outcomes such as falls. Here, we explored the relationship between multisensory integration and a clinically relevant measure of balance/postural control; Sit-to-Stand Time, the efficiency with which an older adult can transition between a seated and a standing posture. We investigated whether temporal multisensory integration was associated with performance on the Five-Times Sit-to-Stand Test (FTSST) in a large sample of 2556 older adults (mean age = 63.62 years, SD = 7.50; 55% female) drawn from The Irish Longitudinal Study on Ageing (TILDA). K-means clustering was applied to FTSST data, yielding three clusters characterised by fast (mean = 10.88 s; n = 1122), medium (mean = 14.34 s; n = 1133) and slow (mean = 18.97 s; n = 301) sit-to-stand times. At wave 3 of TILDA, older adults participated in the Sound Induced Flash Illusion (SIFI), a measure of the precision of temporal audio-visual integration, which included three audio-visual stimulus onset asynchronies (SOAs): 70, 150 and 230 ms. Older adults with the slowest sit-to-stand times were more susceptible to the SIFI at the longest SOA (230 ms) compared to the shortest SOA (70 ms) relative to those with the fastest times (p = 0.02). Older adults who take longer to repeatedly transition from a seated to a standing posture exhibit an expanded temporal binding window for audio-visual events, supporting a link between multisensory perception and balance/postural control in ageing.

Exploring how arm movement moderates the effect of task difficulty on balance performance in young and older adults

Emerging evidence highlights that arm movements exert a substantial and functionally relevant contribution on quiet standing balance control in young adults. Ageing is associated with "non-functional" compensatory postural control strategies (i.e., lower limb co-contraction), which in turn, may increase the reliance on an upper body strategy to control upright stance. Thus, the primary purpose of this study was to compare the effects of free versus restricted arm movements on balance performance in young and older adults, during tasks of different difficulty. Fifteen young (mean ± SD age; 21.3 ± 4.2 years) and fifteen older (mean ± SD age; 73.3 ± 5.0 years) adults performed bipedal, semi-tandem and tandem balance tasks under two arm position conditions: restricted arm movements and free arm movements. Centre of pressure (COP) amplitude and frequency were calculated as indices of postural performance and strategy, respectively. Especially in older adults, restriction of arm movement resulted in increased sway amplitude and frequency, which was primarily observed for the mediolateral direction. Further, increasing balance task difficulty raised the arm restriction cost (ARC; a new measure to quantify free vs. restricted arm movement differences in postural control) that was more prominent in older adults. These findings indicate the ARC provides a measure of reliance on the upper body for balance control and that arm movement is important for postural control in older adults, especially during tasks of greater difficulty.

Effects of Neuromuscular Training on Physical Performance in Older People: A Systematic Review

This systematic review aimed to assess the available evidence on the effects of neuromuscular training on physical performance in older adults. A literature search was conducted across four databases (Psychology and Behavioral (EBSCO), Scopus, Web of Science and PubMed). The PRISMA guidelines were followed. The PEDro scale and Cochrane risk of bias tool were used to assess the quality of and risk of bias in the studies, respectively. The protocol was registered in PROSPERO (code: CRD42022319239). The outcomes were muscle strength, cardiorespiratory fitness, postural balance and gait speed. From 610 records initially found, 10 were finally included in the systematic review, involving 354 older people with a mean age of 67.3 years. Nine of them reported significant changes in at least one variable related to physical performance in the intervention compared to the control groups. The neuromuscular training caused significant improvements in postural balance, flexibility, cardiorespiratory fitness, strength power of the upper and lower limbs and autonomy. The available evidence indicates that neuromuscular training has a positive effect on some variables of physical performance, especially in postural balance; however, the methodological quality and certainty of the evidence in the available literature are limited. Therefore, a greater number of high-quality studies are required to draw definitive conclusions.

Can handgrip strength measurements predict postural balance performance in older women?

OBJECTIVES

The link between handgrip strength and postural balance in older adults is not well understood. This study aimed to examine the correlations between postural balance performance and handgrip peak force and rate of force development (RFD) measurements in older women.

METHODS

Twenty older women (67 ± 5 years) participated in this study. Handgrip contractions were used to assess peak force, peak RFD, and RFD at 0-100 (RFD100) and 0-200 (RFD200) ms. Postural balance was evaluated using a commercially designed balance testing device, which provides a measurement of static stability based on the sway index.

RESULTS

There were significant correlations between sway index and handgrip peak force (r = -0.497, P = 0.026), peak RFD (r = -0.552, P = 0.012), RFD100 (r = -0.539, P = 0.014), and RFD200 (r = -0.499, P = 0.025). Stepwise multiple regression analysis indicated that handgrip peak RFD was the single best predictor of sway index (R² = 0.305). The other variables, including peak force, did not add any unique variance to the stepwise prediction model.

CONCLUSION

These findings suggest that handgrip strength, and in particular peak RFD, may be an effective parameter at predicting postural balance performance in older women.

Young, but not in the dark-The influence of reduced lighting on gait stability in middle-aged adults

BACKGROUND

The aim of this study was to investigate the effects of walking in reduced lighting with or without performing a secondary cognitive task on gait dynamics in middle-aged adults and to compare them with young and old adults.

METHODS

Twenty young (age 28.8±4.1), 20 middle-aged (age 50.2±4.4), and 19 elderly (age 70.7±4.2) subjects participated in the study. Subjects walked on an instrumented treadmill at a self-determined pace under four conditions in randomized order: (1) walking in usual lighting (1000 lumens); (2) walking in near-darkness (5 lumens); (3) walking in usual lighting with a serial-7 subtraction dual-task; and (4) walking in near-darkness with a serial-7 subtraction dual-task. Variability in stride time and variability in the trajectory of the center of pressure in the sagittal and frontal planes (anterior/posterior and lateral variability) were measured. Repeated measures ANOVA and planned comparisons were used to determine the effects of age, lighting conditions, and cognitive task on each gait outcome.

RESULTS

Under usual lighting, stride time variability and anterior/posterior variability of the middle-aged subjects were similar to those of the young and lower than those of the old. The lateral variability of the middle-aged subjects was higher than that of young adults under both lighting conditions. Similar to the older adults, the middle-aged participants increased their stride time variability when walking in near-darkness, but they were the only ones to exhibit increased lateral variability and anterior/posterior variability in near-darkness. Young adult gait was not affected by lighting, and concurrent performance of a cognitive task while walking did not affect gait stability in all groups under any of the lighting conditions.

CONCLUSIONS

Gait stability decreases in middle age when walking in the dark. Recognition of functional deficits in middle age could promote appropriate interventions to optimize aging and reduce fall risk.

Unilateral cathodal transcranial direct current stimulation over the parietal area modulates postural control depending with eyes open and closed

Objective

Cathodal transcranial direct current stimulation (C-tDCS) is generally assumed to inhibit cortical excitability. The parietal cortex contributes to multisensory information processing in the postural control system, and this processing is proposed to be different between the right and left hemispheres and sensory modality. However, previous studies did not clarify whether the effects of unilateral C-tDCS of the parietal cortex on the postural control system differ depending on the hemisphere. We investigated the changes in static postural stability after unilateral C-tDCS of the parietal cortex.

Methods

Ten healthy right-handed participants were recruited for right- and left-hemisphere tDCS and sham stimulation, respectively. The cathodal electrode was placed on either the right or left parietal area, whereas the anodal electrode was placed over the contralateral orbit. tDCS was applied at 1.5 mA for 15 min. We evaluated static standing balance by measuring the sway path length (SPL), mediolateral sway path length (ML-SPL), anteroposterior sway path length (AP-SPL), sway area, and the SPL per unit area (L/A) after 15-minute C-tDCS under eyes open (EO) and closed (EC) conditions. To evaluate the effects of C-tDCS on pre- and post-offline trials, each parameter was compared using two-way repeated-measures analysis of variance (ANOVA) with factors of intervention and time. A post-hoc evaluation was performed using a paired t-test. The effect sizes were evaluated according to standardized size-effect indices of partial eta-squared (ηp²) and Cohen’s d. The power analysis was calculated (1-β).

Results

A significant interaction was observed between intervention and time for SPL (F (2, 27) = 4.740, p = 0.017, ηp² = 0.260), ML-SPL (F (2, 27) = 4.926, p = 0.015, ηp² = 0.267), and sway area (F (2, 27) = 9.624, p = 0.001, ηp² = 0.416) in the EO condition. C-tDCS over the right hemisphere significantly increased the SPL (p < 0.01, d = 0.51), ML-SPL (p < 0.01, d = 0.52), and sway area (p < 0.05, d = 0.83) in the EO condition. In contrast, C-tDCS over the left hemisphere significantly increased the L/A in both the EC and EO condition (EO; p < 0.05, d = 0.67, EC; p < 0.05, d = 0.57).

Conclusion

These results suggest that the right parietal region contributes to static standing balance through chiefly visual information processing during the EO condition. On the other hand, L/A increase during EC and EO by tDCS over the left parietal region depends more on somatosensory information to maintain static standing balance during the EC condition.

Diferentes intervenções de fisioterapia na melhora da sensibilidade plantar e equilíbrio de idosas

Objetivo: comparar os efeitos de dois diferentes protocolos de fisioterapia no tratamento da sensibilidade plantar e equilíbrio em idosas da comunidade do município de Panambi. Métodos: ensaio clínico piloto, quantitativo e descritivo. As participantes responderam questionário sobre condições de saúde e autopercepção de sensibilidade plantar. Após, passaram por avaliação da sensibilidade plantar com estesiômetro Semmes-Weinstein. Foram selecionadas apenas idosas com sensibilidade diminuída. O equilíbrio foi avaliado através da Escala de Equilíbrio de Berg e teste Timed Up and Go. As 13 participantes selecionadas foram divididas em grupo sensibilidade plantar e grupo proprioceptivo, com a realização de 10 intervenções com cada grupo, com estímulo específico conforme alocação nos grupos. Após houve a reavaliação das participantes com estesiômetro, Escala de Equilíbrio de Berg e Timed Up and Go. As comparações das variáveis quantitativas foram realizadas através do teste t de Student, com nível de significância adotado de 5% (p<0,05). Resultados: 12 idosas concluíram o estudo, porém apenas cinco relataram perceber diminuição de sensibilidade plantar. As regiões plantares com maior perda de sensibilidade foram nos metatarsos, região lateral do pé e calcâneo. Já a região medial, apresentou menor perda sensorial. Após os treinos, ambos os grupos mostraram melhora estatisticamente significativa na sensibilidade plantar. Já no equilíbrio, o grupo sensibilidade plantar apresentou resultados estatisticamente significativos no teste Timed Up and Go e o grupo proprioceptivo na Escala de Equilíbrio de Berg. Conclusão: os treinos mostraram-se efetivos na sensibilidade plantar e equilíbrio das participantes, indicando que a combinação dessas intervenções no tratamento do controle postural é uma boa opção para fisioterapeutas.

Association of sensory phenotype with quality of life, functionality, and emotional well-being in patients suffering from neuropathic pain

ABSTRACT

Neuropathic pain highly affects quality of life, well-being, and function. It has recently been shown based on cluster analysis studies that most patients with neuropathic pain may be categorized into 1 of 3 sensory phenotypes: sensory loss, mechanical hyperalgesia, and thermal hyperalgesia. If these phenotypes reflect underlying pathophysiological mechanisms, they may be more relevant for patient management than underlying neurological diagnosis or pain intensity. The aim of this study was thus to examine the impact of these sensory phenotypes on mental health, functionality, and quality of life. Data of 433 patients from the IMI/EuroPain network database were analyzed, and results of HADS-D/A, Pain Catastrophizing Scale, Euro Quality of Life 5D/-VAS, Brief Pain Inventory, and Graded Chronic Pain Scale between the sensory phenotypes were compared using multiple regression analysis. There was no difference in chronic pain grade, pain intensity, depression, or anxiety scores between phenotypes. Pain interference (Brief Pain Inventory) was higher (P = 0.002); self-reported health state lower (Euro Quality of Life 5D VAS, P = 0.02); and problems regarding mobility (P = 0.008), usual activities (P = 0.004), and self-care (P = 0.039) more prominent (EQ5-D) in the sensory loss compared with the thermal hyperalgesia phenotype. Patients with sensory loss also showed higher pain catastrophizing scores (P = 0.006 and 0.022, respectively) compared with the 2 other groups. Sensory phenotype is associated with the impact of neuropathic pain conditions on well-being, daily functionality, and quality of life but is less associated with pain intensity. These results suggest that the somatosensory phenotype should be considered for personalized pain management.

Age-related changes to vestibular heave and pitch perception and associations with postural control

Falls are a common cause of injury in older adults (OAs), and age-related declines across the sensory systems are associated with increased falls risk. The vestibular system is particularly important for maintaining balance and supporting safe mobility, and aging has been associated with declines in vestibular end-organ functioning. However, few studies have examined potential age-related differences in vestibular perceptual sensitivities or their association with postural stability. Here we used an adaptive-staircase procedure to measure detection and discrimination thresholds in 19 healthy OAs and 18 healthy younger adults (YAs), by presenting participants with passive heave (linear up-and-down translations) and pitch (forward-backward tilt rotations) movements on a motion-platform in the dark. We also examined participants' postural stability under various standing-balance conditions. Associations among these postural measures and vestibular perceptual thresholds were further examined. Ultimately, OAs showed larger heave and pitch detection thresholds compared to YAs, and larger perceptual thresholds were associated with greater postural sway, but only in OAs. Overall, these results suggest that vestibular perceptual sensitivity declines with older age and that such declines are associated with poorer postural stability. Future studies could consider the potential applicability of these results in the development of screening tools for falls prevention in OAs.

Vestibular Function Predicts Balance and Fall Risk in Patients with Alzheimer's Disease

BACKGROUND

Patients with Alzheimer's disease (AD) are at high risk for falls. Vestibular dysfunction predicts balance impairment in healthy adults; however, its contribution to falls in patients with AD is not well known.

OBJECTIVE

The objective of this study was to assess whether vestibular function contributes to balance and fall risk in patients with AD.

METHODS

In this prospective observational study, we assessed vestibular function using measures of semicircular canal (vestibulo-ocular reflex (VOR) gain) and saccular function (cervical vestibular-evoked myogenic (cVEMP) response), and we assessed balance function using the Berg Balance Scale and quantitative posturography. We evaluated falls incidence for a mean 1-year follow-up period (range 3-21 months) in 48 patients with mild-moderate AD.

RESULTS

Relative to matched controls, AD patients exhibited increased medio-lateral (ML) sway in eyes-open (0.89 cm versus 0.69 cm; p = 0.033) and eyes-closed (0.86 cm versus 0.65 cm; p = 0.042) conditions. Among AD patients, better semicircular canal function was associated with lower ML sway and antero-posterior (AP) sway in the eyes-closed condition (β= -2.42, 95% CI (-3.89, -0.95), p = 0.002; β= -2.38, 95% CI (-4.43, -0.32), p = 0.025, respectively). Additionally, better saccular function was associated with lower sway velocity (β= -0.18, 95% CI (-0.28, -0.08); p = 0.001). Finally, we observed that better semicircular canal function was significantly associated with lower likelihood of falls when adjusted for age, sex, and MMSE score (HR = 0.65; p = 0.009).

CONCLUSION

These results support the vestibular system as an important contributor to balance and fall risk in AD patients and suggest a role for vestibular therapy.

Quantitative Romberg using a force plate: an objective measure for cervical myelopathy

BACKGROUND CONTEXT

Surgical decision making for cervical spondylotic myelopathy (CSM) relies on evaluation of symptoms and physical examination. The Romberg test is a clinical exam used to identify balance issues with CSM. However, the Romberg test has a subjective interpretation and has a binary (positive or negative) result.

PURPOSE

This study aims to compare force plate pressure readings during a standard Romberg test in patients with CSM to age-matched normal healthy volunteers.

STUDY DESIGN/SETTING

Prospective cross sectional observational comparative cohort from a single multi-surgeon spine center.

PATIENT SAMPLE

Patients who were clinically diagnosed with CSM were compared to age-matched healthy volunteers without a clinical history of spine pathology.

OUTCOME MEASURES

Quantitative Romberg Force Plate Measurements METHODS: Patients with CSM requiring surgery and healthy normal volunteers were asked to perform the Romberg test while on a force plate measuring the center of pressure (COP): standing up straight with arms extended for 30 seconds with eyes open, followed by 30 seconds with eyes closed. The change for total sway area, sway frequency and sway speed with eyes closed and eyes open were calculated and compared between patients with CSM and healthy volunteers.

RESULTS

Thirty-four CSM patients were age-matched to 34 healthy volunteers. There was a larger change in quantitative Romberg measurements with eyes open versus eyes closed in CSM patients compared to normal volunteers for maximum lateral movement (10.79 cm vs. 0.94 cm, p=.003), maximum anterior-posterior movement (15.06 cm vs. 10.00 cm p=.201), total lateral CoP movement (89.82cm vs. 18.71cm, p=.007), total AP CoP movement (154.68 cm vs. 87.47 cm, p=.601), total CoP trace movement (199.79 cm vs. 88.44 cm, p=.014), sway area (284.74 cm² vs. 57.76 cm², p=.006), and average speed (7.00 cm/s vs. 2.91 cm/s, p=.006).

DISCUSSION

Poor standing balance can be quantified in patients with CSM. Quantifying standing balance in patients with CSM shows significantly worse objective measures than age-matched healthy volunteers. The Romberg test on a force plate may help diagnose and evaluate patients with CSM, guide patient management and potentially grade the severity of spinal pathology. Further studies are needed to determine its utility in monitoring disease progression and measure treatment effectiveness.

Might Vestibular "Noise" Cause Subclinical Balance Impairment and Falls?

Falls are the leading causes of accidental injury in older adults and directly contribute to more than 600,000 deaths each year worldwide. Although the issue of falls is complex, balance dysfunction is one the principal contributors to the heightened incidence of falls in older adults. A nationally representative survey of older adults in the United States showed that an inability to stand on a foam pad with the eyes closed was associated with more than a six-fold increase in the odds of reporting "difficulty with falls." As stability in the "eyes closed, on foam" condition is reliant upon intact vestibular cues, these data implicate age-related vestibular loss as a potential contributor to falls, yet, the specific causal mechanism explaining the link between age-related vestibular loss and imbalance/falls was not known. Here we review recent data showing that, vestibular perceptual thresholds, an assay of vestibular sensory noise, were found to, (1) account for nearly half of subclinical balance impairment in healthy older adults and (2) correlate with postural sway in healthy young adults. Based upon the identified links between balance dysfunction and vestibular noise in healthy adults, we posit the following causal chain: (a) increased "noise" in vestibular feedback - yielding a reduced signal-to-noise ratio in vestibular feedback-increases sway, (b) excessive sway leads to imbalance, and (c) imbalance contributes to falls. Identifying the "cause" of age-related balance dysfunction will inform the development of interventions tailored to prevent falls, and fall-related injuries, in the growing population of older adults.

Using virtual reality to assess vestibulo-visual interaction in people with Parkinson's disease compared to healthy controls

People with Parkinson's disease (PD) have increased visual dependency for balance and suspected vestibular dysfunction. Immersive virtual reality (VR) allows graded manipulation of visual sensory inputs during balance tasks, and hence VR coupled with portable force platforms have emerged as feasible, affordable, and validated tools for assessing sensory-motor integration of balance. This study aims to determine (i) how people with PD perform on a VR-based visual perturbation standing balance task compared to healthy controls (HC), and (ii) whether balance performance is influenced by vestibular function, when other known factors are controlled for. This prospective observational study compared the balance performance under varying sensory conditions in 40 people with mild to moderate PD with 40 age-matched HC. Vestibular function was assessed via Head Impulse Test (HIMP), cervical and ocular vestibular evoked myogenic potentials (cVEMPs and oVEMPs) and subjective visual vertical (SVV). Regression analyses were used to determine associations between VR balance performance on firm and foam surfaces with age, group, vestibular function, and lower limb proprioception. PD failed at significantly lower levels of visual perturbation than HC on both surfaces. In PD, greater disease severity was significantly associated with lower fall thresholds on both surfaces. Multiple PD participants failed prior to visual perturbation on foam. On firm, PD had a greater visual dependency. Increasing age, impaired proprioception, impaired SVV, abnormal HIMP and cVEMP scores were associated with worse balance performance. The multivariate model containing these factors explained 29% of the variability in balance performance on both surfaces. Quantitative VR-based balance assessment is safe and feasible in PD. Balance performance on both surfaces was associated with age, HIMP abnormality and proprioception.

A Perturbed Postural Balance Test Using an Instrumented Treadmill - Precision and Accuracy of Belt Movement and Test-Retest Reliability of Balance Measures

A perturbed postural balance test can be used to investigate balance control under mechanical disturbances. The test is typically performed using purpose-built movable force plates. As instrumented treadmills become increasingly common in biomechanics laboratories and in clinical settings, these devices could be potentially used to assess and train balance control. The purpose of the study was to investigate how an instrumented treadmill applies to perturbed postural balance test. This was investigated by assessing the precision and reliability of the treadmill belt movement and the test-retest reliability of perturbed postural balance test over 5 days. Postural balance variables were calculated from the center of pressure trajectory and included peak displacement, time to peak displacement, and recovery displacement. Additionally, the study investigated short-term learning effects over the 5 days. Eight healthy participants (aged 24–43 years) were assessed for 5 consecutive days with four different perturbation protocols. Center of pressure (COP) data were collected using the force plates of the treadmill while participant and belt movements were measured with an optical motion capture system. The results show that the treadmill can reliably deliver the intended perturbations with <1% deviation in total displacement and with minimal variability between days and participants (typical errors 0.06–2.71%). However, the treadmill was not able to reach the programmed 4 m/s² acceleration, reaching only about 75% of it. Test–retest reliability of the selected postural balance variables ranged from poor to good (ICC 0.156–0.752) with typical errors between 4.3 and 28.2%. Learning effects were detected based on linear or quadratic trends (p < 0.05) in peak displacement of the slow forward and fast backward protocols and in time to peak displacement in slow and fast backward protocols. The participants altered the initial location of the COP relative to the foot depending on the direction of the perturbation. In conclusion, the precision and accuracy of belt movement were found to be excellent. Test-retest reliability of the balance test utilizing an instrumented treadmill ranged from poor to good which is, in line with previous investigations using purpose-built devices for perturbed postural balance assessment.

Measuring Vestibular Contributions to Age-Related Balance Impairment: A Review

Aging is associated with progressive declines in both the vestibular and human balance systems. While vestibular lesions certainly contribute to imbalance, the specific contributions of age-related vestibular declines to age-related balance impairment is poorly understood. This gap in knowledge results from the absence of a standardized method for measuring age-related changes to the vestibular balance pathways. The purpose of this manuscript is to provide an overview of the existing body of literature as it pertains to the methods currently used to infer vestibular contributions to age-related imbalance.

Cutaneous and muscular afferents from the foot and sensory fusion processing: Physiology and pathology in neuropathies

The foot-sole cutaneous receptors (section 2), their function in stance control (sway minimisation, exploratory role) (2.1), and the modulation of their effects by gait pattern and intended behaviour (2.2) are reviewed. Experimental manipulations (anaesthesia, temperature) (2.3 and 2.4) have shown that information from foot sole has widespread influence on balance. Foot-sole stimulation (2.5) appears to be a promising approach for rehabilitation. Proprioceptive information (3) has a pre-eminent role in balance and gait. Reflex responses to balance perturbations are produced by both leg and foot muscle stretch (3.1) and show complex interactions with skin input at both spinal and supra-spinal levels (3.2), where sensory feedback is modulated by posture, locomotion and vision. Other muscles, notably of neck and trunk, contribute to kinaesthesia and sense of orientation in space (3.3). The effects of age-related decline of afferent input are variable under different foot-contact and visual conditions (3.4). Muscle force diminishes with age and sarcopenia, affecting intrinsic foot muscles relaying relevant feedback (3.5). In neuropathy (4), reduction in cutaneous sensation accompanies the diminished density of viable receptors (4.1). Loss of foot-sole input goes along with large-fibre dysfunction in intrinsic foot muscles. Diabetic patients have an elevated risk of falling, and vision and vestibular compensation strategies may be inadequate (4.2). From Charcot-Marie-Tooth 1A disease (4.3) we have become aware of the role of spindle group II fibres and of the anatomical feet conditions in balance control. Lastly (5) we touch on the effects of nerve stimulation onto cortical and spinal excitability, which may participate in plasticity processes, and on exercise interventions to reduce the impact of neuropathy.

Aging, Vestibular Function, and Balance: Proceedings of a National Institute on Aging/National Institute on Deafness and Other Communication Disorders Workshop

Balance impairment and falls are among the most prevalent and morbid conditions affecting older adults. A critical contributor to balance and gait function is the vestibular system; however, there remain substantial knowledge gaps regarding age-related vestibular loss and its contribution to balance impairment and falls in older adults. Given these knowledge gaps, the National Institute on Aging and the National Institute on Deafness and Other Communication Disorders convened a multidisciplinary workshop in April 2019 that brought together experts from a wide array of disciplines, such as vestibular physiology, neuroscience, movement science, rehabilitation, and geriatrics. The goal of the workshop was to identify key knowledge gaps on vestibular function and balance control in older adults and develop a research agenda to make substantial advancements in the field. This article provides a report of the proceedings of this workshop. Three key questions emerged from the workshop, specifically: (i) How does aging impact vestibular function?; (ii) How do we know what is the contribution of age-related vestibular impairment to an older adult's balance problem?; and more broadly, (iii) Can we develop a nosology of balance impairments in older adults that can guide clinical practice? For each of these key questions, the current knowledge is reviewed, and the critical knowledge gaps and research strategies to address them are discussed. This document outlines an ambitious 5- to 10-year research agenda for increasing knowledge related to vestibular impairment and balance control in older adults, with the ultimate goal of linking this knowledge to more effective treatment.

Assessment of standing balance in normal versus cervical spondylotic myelopathy patients

Background

The Romberg test is used to identify balance issues in patients with Cervical Spondylotic Myelopathy (CSM), but has subjective interpretation. The purpose of this study is to evaluate force plate pressure readings during a Romberg test to quantify postural control.

Methods

Quantitative Romberg force plate readings with eyes open and closed in patients with CSM were obtained and changes in balance measurements were compared to a normal population (N = 28, mean age 39 ± 7 years).

Results

We identified 30 CSM patients with a mean age of 58 ± 10 years. Majority of patients presented with pain (90%) and neurologic symptoms (83%). Cord compression on imaging was identified in 90%. Mean eyes closed Romberg measurements were larger compared to eyes open measurements in CSM patients (p < 0.01). There was a larger change in Romberg (∆R) measurements in CSM compared to normals for total sway area (TSA, 14.18 vs 0.02 cm², p < 0.001) and average speed (AS, 2.07 vs 0.23 cm/s, p < 0.001). The presence of long tract signs produced larger ∆R (TSA, 15.35 vs 0.02 cm², p = 0.003; AS, 2.21 vs 0.23 cm/s, p = 0.001), and those with identified cord compression on imaging also had larger ∆R (TSA, 15.1 vs 0.02 cm², p < 0.001; AS, 2.17 vs 0.23 cm/s, p < 0.001).

Conclusions

Standing balance can be quantified in patients with CSM and is worse when compared to a normal population. Long tract signs and cord compression in imaging translates to worse balance in myelopathic patients. The use of quantitative Romberg measurements help evaluate balance in CSM.

Using Augmented Reality with Older Adults in the Community to Select Design Features for an Age-Friendly Park: A Pilot Study

Sedentary behavior is prevalent in older adults. Older adults often underutilize public parks for exercising because the parks do not support their needs and preferences. Engaging older adults on the redesign of parks may help promote active lifestyles. The objectives of this pilot study were to evaluate (1) the effects of wearing augmented reality (AR) and virtual reality (VR) glasses on balance; (2) the effects of different virtual walls separating the walking trail from the roadway on older adults' gait, and (3) the preferences of the participants regarding wall design and other features. The participants were ten older adults (68 ± 5 years) who lived within two miles from the park. Balance and gait were assessed using a force plate and an instrumented mat. It was feasible to use AR with older adults in the park to evaluate features for redesign. Motion sickness was not an issue when using AR glasses, but balance was affected when wearing VR goggles. The area of postural sway increased approximately 25% when wearing AR glasses, and it increased by close to 70% when wearing VR goggles compared to no glasses. This difference is clinically relevant; however, we did not have enough power to identify the differences as statistically significant because of the small sample size and large variability. Different walls did not significantly affect the participants' gait either because they did not alter the way they walked or because the holograms were insufficiently realistic to cause changes. The participants preferred a transparent wall rather than tall or short solid walls to separate the park from the roadway.

Impact of Extremity Manipulation on Postural Sway Characteristics: A Preliminary, Randomized Crossover Study

OBJECTIVE

Evaluate multisegmental postural sway after upper- vs lower-extremity manipulation.

METHODS

Participants were healthy volunteers (aged 21-40 years). Upper- or lower-extremity manipulations were delivered in a randomized crossover design. Postural assessments were made pre-post manipulation, in floor and rocker board conditions. Analysis included traditional balance measures of pathlength and range and sample entropy (SampEn) to examine the temporal structure of sway of the head, trunk, and surface.

RESULTS

No statistical changes in pathlength or sway range on the ground surface condition were observed. No increases in the amount of sway occurred in any condition. Chiropractic manipulation of either upper or lower extremities led to reductions in traditional measures of postural control on the rocker board. In the anteroposterior direction (sagittal plane), lower-extremity manipulation led to increased trunk SampEn while on the ground, and conversely a decreased SampEn while on the rocker board. In the mediolateral rocker board condition (frontal plane), manipulation elicited a change in SampEn that differed according to site of manipulation; upper-extremity manipulation increased SampEn, whereas lower-extremity manipulation reduced SampEn.

CONCLUSION

Both upper- and lower-extremity manipulation influenced several measures of postural sway on both the ground and the rocker board. Lower-extremity manipulation improved the organization of sway at the trunk (anteroposterior direction) and the board (mediolateral direction). Given the reduction and reorganization of sway metrics seen in this study, we propose extending this line of research to the elderly who are at greatest risk of increased sway and falls.

Does variability in motor output at individual joints predict stride time variability in gait? Influences of age, sex, and plane of motion

Old age is associated with variability in gait motor output, particularly in females, and is linked to fall risk. However, little is known about how older age and sex affect variability in the outputs of individual joints, and how these variabilities contribute to the collective gait output. Healthy adults aged 18-99 years (N = 102, 57 females) completed six trials of straight walking at self-selected speed. Stride time variability (coefficient of variation) and variabilities of lower limb tridimensional joint angles (standard deviations: SD) were calculated. Age * Sex (A * S) mixed models were conducted on all measures and year-by-year rates of change were subsequently estimated. Correlations and stepwise linear regression analyses were computed between joint angular variabilities and stride time variability. Each year of age was associated with 0.022% higher stride time variability (A: p = .002), 0.07° lower variability in peak ankle dorsiflexion (A: p = .004), 0.002-0.098° higher variability in mean ankle inversion/eversion, mean pelvic obliquity, and pelvic rotation range of motion (A: p < .05), and 0.024° higher variability in knee flexion/extension range of motion in males (A * S: p = .003). Higher variability in mean ankle and hip flexion/extension and in mean ankle inversion/eversion correlated with (ρ = 0.211-0.336; ps < 0.05) and independently predicted higher stride time variability (ps < 0.05), together explaining 21.9% of variance. Results suggest that higher stride time variability with older age may be produced by a shift from sagittal plane variability to frontal plane variability at the ankle.

Human Balance in Response to Continuous, Predictable Translations of the Support Base: Integration of Sensory Information, Adaptation to Perturbations, and the Effect of Age, Neuropathy and Parkinson’s Disease

This short narrative review article moves from early papers that described the behaviour of healthy subjects balancing on a motorized platform continuously translating in the antero-posterior direction. Research from the laboratories of two of the authors and related investigations on dynamic balancing behaviour are briefly summarized. More recent findings challenging time-honoured views are considered, such as the statement that vision plays a head-in-space stabilizing role. The time interval to integrate vision or its withdrawal in the balancing pattern is mentioned as well. Similarities and differences between ageing subjects and patients with peripheral or central disorders are concisely reported. The muscle activities recorded during the translation cycles suggest that vision and amplitude changes of the anticipatory postural activities play a predominant role in controlling dynamic balance during prolonged administration of the predictable perturbation. The potential of this paradigm for rehabilitation of balance problems is discussed.

Deactivation of somatosensory and visual cortices during vestibular stimulation is associated with older age and poorer balance

Aging is associated with peripheral and central declines in vestibular processing and postural control. Here we used functional MRI to investigate age differences in neural vestibular representations in response to pneumatic tap stimulation. We also measured the amount of body sway in multiple balance tasks outside of the MRI scanner to assess the relationship between individuals' balance ability and their vestibular neural response. We found a general pattern of activation in canonical vestibular cortex and deactivation in cross modal sensory regions in response to vestibular stimulation. We found that activation amplitude of the vestibular cortex was correlated with age, with younger individuals exhibiting higher activation. Deactivation of visual and somatosensory regions increased with age and was associated with poorer balance. The results demonstrate that brain activations and deactivations in response to vestibular stimuli are correlated with balance, and the pattern of these correlations varies with age. The findings also suggest that older adults exhibit less sensitivity to vestibular stimuli, and may compensate by differentially reweighting visual and somatosensory processes.

Failure on the Foam Eyes Closed Test of Standing Balance Associated With Reduced Semicircular Canal Function in Healthy Older Adults

OBJECTIVES

Standing on foam with eyes closed (FOEC) has been characterized as a measure of vestibular function; however, the relative contribution of vestibular function and proprioceptive function to the FOEC test has not been well described. In this study, the authors investigate the relationship between peripheral sensory systems (vestibular and proprioception) and performance on the FOEC test in a cohort of healthy adults.

DESIGN

A total of 563 community-dwelling healthy adults (mean age, 72.7 [SD, 12.6] years; range, 27 to 93 years) participating in the Baltimore Longitudinal Study of Aging were tested. Proprioceptive threshold (PROP) was evaluated with passive motion detection at the right ankle. Vestibulo-ocular reflex (VOR) gain was measured using video head impulses. Otolith function was measured with cervical and ocular vestibular-evoked myogenic potentials. Participants stood on FOEC for 40 sec while wearing BalanSens (BioSensics, LLC, Watertown, MA) to quantify center of mass sway area. A mixed-model multiple logistic regression was used to examine the odds of passing the FOEC test based on PROP, VOR, cervical vestibular-evoked myogenic potential, and ocular vestibular-evoked myogenic potential function in a multisensory model while controlling for age and gender.

RESULTS

The odds of passing the FOEC test decreased by 15% (p < 0.001) for each year of increasing age and by 8% with every 0.1 reduction in VOR gain (p = 0.025). Neither PROP nor otolith function was significantly associated with passing the FOEC test.

CONCLUSIONS

Failure to maintain balance during FOEC may serve as a proxy for rotational vestibular contributions to postural control. Semicircular canals are more sensitive to low-frequency motion than otoliths that may explain these relationships because standing sway is dominated by lower frequencies. Lower VOR gain and increased age independently decreased the odds of passing the test.

Age-related changes in leg proprioception: implications for postural control

In addition to being a prerequisite for many activities of daily living, the ability to maintain steady upright standing is a relevant model to study sensorimotor integrative function. Upright standing requires managing multimodal sensory inputs to produce finely tuned motor output that can be adjusted to accommodate changes in standing conditions and environment. The sensory information used for postural control mainly arises from the vestibular system of the inner ear, vision, and proprioception. Proprioception (sense of body position and movement) encompasses signals from mechanoreceptors (proprioceptors) located in muscles, tendons, and joint capsules. There is general agreement that proprioception signals from leg muscles provide the primary source of information for postural control. This is because of their exquisite sensitivity to detect body sway during unperturbed upright standing that mainly results from variations in leg muscle length induced by rotations around the ankle joint. However, aging is associated with alterations of muscle spindles and their neural pathways, which induce a decrease in the sensitivity, acuity, and integration of the proprioceptive signal. These alterations promote changes in postural control that reduce its efficiency and thereby may have deleterious consequences for the functional independence of an individual. This narrative review provides an overview of how aging alters the proprioceptive signal from the legs and presents compelling evidence that these changes modify the neural control of upright standing.

Reduced vestibular function is associated with longer, slower steps in healthy adults during normal speed walking

BACKGROUND

Vestibular signals contribute to balance and walking. With aging, vestibular function declines and gait speed decreases. Vestibular loss contributes to decreasing gait speed, but this influence could be linked to spatial and/or temporal aspects of gait. We investigated the relationship between vestibular function (semicircular canal and otolith function) and spatial and temporal gait parameters in a cohort of adults.

METHODS

113 community-dwelling healthy adults (mean age 72.2 (14.6) years) participating in the Baltimore Longitudinal Study of Aging were tested. Horizontal semicircular canal (SCC) function was evaluated using quantitative vestibulo-ocular reflex gain. Otolith function was measured with cervical and ocular vestibular evoked myogenic potentials. Gait kinematics were collected during normal speed walking. Multiple linear regressions examined the association between spatial and temporal gait parameters and SCC and otolith function separately, controlling for age, gender, height, and either cadence (for spatial gait outcomes) or stride length (for temporal gait outcomes) to account for gait speed effects.

RESULTS

Vestibular SCC function was significantly associated with both spatial and temporal gait parameters. Every 0.1 decrease in SCC function resulted in longer stride length (β = -.04 m, p = 0.004), longer stance time (β = 15.8 ms, p < 0.003), and a slower cadence (β = -2.1 steps/minute, p < 0.001). Otolith function was not associated with any gait parameter.

CONCLUSIONS

Reduced horizontal SCC function was associated with longer, slower steps in a cohort of healthy adults. These results indicate that vestibular signals contribute to specific spatial and temporal aspects of gait thought to contribute to upright balance.

Concurrent Validity of Postural Sway Measures in Older Adults with Cognitive Impairment

Aims

To examine concurrent validity of inertial sensor (APDM ISway) versus force plate center of pressure (COP) measures of postural sway in cognitively impaired older adults.

Methods

Participants, mean age 85.6 (SD 4.8), were tested in 4 static standing conditions: (1) eyes open/normal base, (2) eyes open/narrow base, (3) eyes closed/normal base, and (4) eyes closed/narrow base. ISway and COP measures were collected.

Results

Strong correlations between ISway trunk sway smoothness [ISway JERK, (m ² /s ⁵ )] and COP path length (r = 0.67-0.85) and COP mean velocity (r = 0.77-0.87); also ISway total sway acceleration path length/trail duration [ISway PATH, (m²/s²)] and COP path length (r = 0.77-0.87) and COP mean velocity (r = 0.77-0.91). Increased sway was detected in narrow versus normal base and eyes closed versus open conditions (P = .001).

Conclusions

APDM ISway demonstrated concurrent validity to force-plate COP and changes in postural sway were detected between conditions.

Community-dwelling adults with a history of falling report lower perceived postural stability during a foam eyes closed test than non-fallers

Perceived postural stability has been reported to decrease as sway area increases on firm surfaces. However, changes in perceived stability under increasingly challenging conditions (e.g., removal of sensory inputs) and the relationship with sway area are not well characterized. Moreover, whether perceived stability varies as a function of age or history of falls is unknown. Here we investigate how perceived postural stability is related to sway area and whether this relationship varies as a function of age and fall history while vision and proprioceptive information are manipulated. Sway area was measured in 427 participants from the Baltimore Longitudinal Study of Aging while standing with eyes open and eyes closed on the floor and a foam cushion. Participants rated their stability [0 (completely unstable) to 10 (completely stable)] after each condition, and reported whether they had fallen in the past year. Perceived stability was negatively associated with sway area (cm²) such that individuals who swayed more felt less stable across all conditions (β = - 0.53, p < 0.001). Perceived stability decreased with increasing age (β = - 0.019, p < 0.001), independent of sway area. Fallers had a greater decline in perceived stability across conditions (F = 2.76, p = 0.042) compared to non-fallers, independent of sway area. Perceived postural stability declined as sway area increased during a multisensory balance test. A history of falling negatively impacts perceived postural stability when vision and proprioception are simultaneously challenged. Perceived postural stability may provide additional information useful for identifying individuals at risk of falls.

Normative Data for the BTrackS Balance Test of Postural Sway: Results from 16,357 Community-Dwelling Individuals Who Were 5 to 100 Years Old

BACKGROUND

Postural sway is routinely assessed because increased postural sway is associated with poorer performance of activities of daily living, higher rates of residential care, and increased risk of falling. Force plate technology is one of the most sensitive and objective means of assessing postural sway in the clinic.

OBJECTIVE

The aim of this study was to provide the first set of normative data for the BTrackS Balance Test (BBT) of postural sway.

DESIGN

The design was descriptive and population based.

METHODS

BBT results from 16,357 community-dwelling individuals who were 5 to 100 years old were accumulated and assessed for effects of age, sex, height, and weight. Percentile rankings were calculated for significant groupings.

RESULTS

BBT results were dependent on age and sex but not height or weight. Therefore, percentile rankings were determined for male and female individuals in each age category, with no consideration of participant height or weight.

LIMITATIONS

Data were collected by third-party practitioners with various backgrounds in more than 50 locations across the United States and Canada. There was an imbalance in the sample sizes for age and sex groupings.

CONCLUSIONS

The findings of this study represent the largest normative dataset ever published for postural sway results. Normative data on the BBT can assist in determining abnormalities in postural sway, which have been linked to negative clinical outcomes.

Postural sway normative data across the adult lifespan: Results from 6280 individuals on the Balance Tracking System balance test

AIM

Postural sway measured using force plate technology is a known risk factor for falls in older adults, but is currently underutilized due to the high cost and lack of portability issues associated with most force plate systems. The Balance Tracking System (BTrackS) is a new force plate that alleviates these barriers and has potential for widespread use. The present study provides important normative data for the BTrackS Balance Test of postural sway that improves its translational value to the field of gerontology.

METHODS

BTrackS Balance Test postural sway results were accumulated from 6280 community-dwelling individuals across the adult lifespan. Data were assessed for effects of age, sex and body size. Stratified percentile rankings were then calculated.

RESULTS

BTrackS Balance Test results were dependent on age and sex, but not body size. Percentile rankings were, therefore, determined across various age groups for men and women separately, with no consideration of participant body size. A novel interaction was found between the age and sex factors, suggesting enhanced postural sway ability for women that becomes more pronounced with older age.

CONCLUSIONS

The results of the present study represent one of the largest sets of normative postural sway data ever published. These data translate directly into the field of gerontology as a tool for determining abnormalities in postural sway, which have been linked to various poor outcomes in older adults, such as high fall risk. Geriatr Gerontol Int 2018; 18: 1225-1229.

Vestibular Dysfunction and Difficulty with Driving: Data from the 2001-2004 National Health and Nutrition Examination Surveys

BACKGROUND AND OBJECTIVE

There is growing understanding of the role of vestibular function in spatial navigation and orientation. Individuals with vestibular dysfunction demonstrate impaired performance on static and dynamic tests of spatial cognition, but there is sparse literature characterizing how these impairments might affect individuals in the real-world. Given the important role of visuospatial ability in driving a motor vehicle, we sought to evaluate whether individuals with vestibular dysfunction might have increased driving difficulty.

MATERIALS AND METHODS

We used data from the 2001-2004 National Health and Nutrition Examination Surveys to evaluate the influence of vestibular dysfunction in driving difficulty in a nationally representative sample of U.S. adults aged ≥50 years (n = 3,071). Vestibular function was measured with the modified Romberg test. Furthermore, since vestibular dysfunction is a known contributor to falls risk, we assessed whether individuals with vestibular dysfunction and concomitant driving difficulty were at an increased risk of falls.

RESULTS

In multivariate analyses, vestibular dysfunction was associated with a twofold increased odd of driving difficulty (odds ratio 2.16, 95% CI 1.57, 2.98). Among participants with vestibular dysfunction, concomitant driving difficulty predicted an increased risk of falls that was significantly higher than in participants with vestibular dysfunction only (odds ratio 13.01 vs. 2.91, p < 0.0001).

CONCLUSION

This study suggests that difficulty driving may be a real-world manifestation of impaired spatial cognition associated with vestibular loss. Moreover, driving difficulty may be a marker of more severe vestibular dysfunction.