Proprioceptive impairments in high fall risk older adults: the effect of mechanical calf vibration on postural balance

Assessing postural stability in flatfoot using a time-in-boundary method during single-leg standing

Flatfoot, a foot deformity characterized by the collapse of the arch, significantly impacts an individual's balance and stability. This study explored postural adjustments and sway excursions in individuals with and without flatfoot using the Time-in-Boundary method. This method assessed relative stability by exploring various center of pressure radius thresholds during three trials of single-leg stance. We observed significant interactions in threshold levels (F = 4.37, p = 0.04) and normalized relative stable times (F = 7.64, p = 0.01), particularly in the initial trials. Initially, the flatfoot group showed marked decreases in stable times at 10 mm, 15 mm, and 20 mm thresholds, which expanded to 25 mm and 30 mm in subsequent trials. Despite a significant decrease in stability at the 30 mm threshold in early trials, participants exhibited improved stability control as trials progressed. This enhancement likely reflects a combination of a learning effect and an increased understanding of the task requirements, underscoring the adaptability of postural control systems to the biomechanical challenges posed by flatfoot. The Time-in-Boundary method has proven to be an effective tool for clinicians to assess postural control, playing a vital role in developing customized rehabilitation strategies for individuals with flatfoot.

Percentage of decline in individual proprioceptors in older adults

[Purpose] Although standing balance and functions of each proprioceptor decline with age in older adults, data regarding the types and percentages of proprioceptors susceptible to decline are unavailable. In this study, we investigated the rate of decline in each proprioceptor area in older adults and also the effect of aging on the association between postural balance and proprioception. [Participants and Methods] This study performed between November 2012 and July 2022 included both young and older adults. Vibration stimuli were applied to the gastrocnemius and lumbar multifidus muscles at 30-250 Hz to assess the effects of the easily attenuated proprioceptors. The independent t-test showed a decline in proprioception in older adults. A χ2 test was performed to determine proprioceptors that were susceptible to attenuation in older adults. [Results] The results revealed that many older adults had reduced muscle spindles (low and high frequencies) in their lower legs and trunk (low frequency). [Conclusion] Proprioceptive ability is lower in older adults than in younger individuals. Therefore, activation programs to treat the reduced intrinsic receptive responsiveness may be required for rehabilitation of older adults.

What are the temporal and physical characteristics of locally applied vibration that modulate balance in older adults? - A systematic review of the literature

BACKGROUND

Compromised balance is known to contribute to falls, which are associated with increased morbidity and mortality for older adults. Evidence suggests that the application of local vibration to the lower limbs of older adults has the potential to modulate balance.

RESEARCH QUESTION

To identify the temporal and mechanical parameters of vibration applied locally to the lower limbs of older adults that modulate measures of balance, and to define the short- and long-term effects of vibration on balance in this population.

METHODS

The PRISMA 2020 guidelines were used to conduct a systematic search including the PUBMED, EMBASE, and Scopus databases to identify peer-reviewed literature where vibration was applied to the lower limbs of older adults to modulate balance. Data was extracted using a study-specific data extraction form and risk of bias assessed. Where possible, effect sizes were calculated.

RESULTS

Of 7777 records screened, ten randomised controlled trials and 43 prospective laboratory-based studies met the inclusion criteria. Vibration frequencies ranged from 1 to 272 Hz, most studies (n=41) used ≤100 Hz. Amplitude ranged from 0.2 to 3.0 mm, most studies (n=28) used ≤1 mm. Effects of short-term vibration (applied for seconds to hours) were measured during and/or immediately after application. Short-term suprathreshold perceived muscle/tendon vibration had a 'large' destabilising effect size on balance in healthy older adults, but little or no effect on older fallers. Short-term subthreshold vibration to the soles of the feet had a 'small' stabilising effect size. Suprathreshold muscle, tendon or sole vibration applied for 10-30 min over days to weeks improved balance measures, but most (8 of 10) had increased risk of bias.

SIGNIFICANCE

The heterogeneity of methodology, populations, and vibration and balance parameters precluded conclusions about the relative effects of lower limb vibration in older adults. However, these results suggest that the application of local vibration to the lower limbs of older adults can modulate balance in the short- and long-term.

Assessing the role of ankle and hip joint proprioceptive information in balance recovery using vibratory stimulation

Background

Previous work suggests that proprioceptive information from ankle and hip are crucial in maintaining balance during upright standing; however, the contribution of these proprioceptive information during stepping balance recovery in not clear. The goal of the current study was to assess the role of ankle and hip proprioceptive information on balance recovery performance by manipulating type 1a afferent in muscle spindles using vibratory stimulation.

Methods

Twenty healthy young participants were recruited (age = 22.2 ± 2.7 years) and were randomly assigned to balance recovery sessions with either ankle or hip stimulation. Trip-like perturbations were imposed using a modified treadmill setup with a protecting harness. Vibratory stimulation was imposed bilaterally on ankle and hip muscles to expose participants to three condition of no-vibration, 40Hz vibration, and 80Hz vibration. Kinematics of the trunk and lower-extremities were measured using wearable sensors to characterize balance recovery performance. Outcomes were response time, recovery step length, trunk angle during toe-off and heel-strike of recovery stepping, and required time for full recovery.

Findings

Ankle vibratory stimulation elicited main effects on reaction time and recovery step length (p < 0.002); reaction time and recovery step length increased by 23.0% and 21.2%, respectively, on average across the conditions. Hip vibratory stimulation elicited significant increase in the full recovery time (p = 0.019), with 55.3% increase on average across the conditions.

Interpretation

Current findings provided evidence that vibratory stimulation can affect the balance recovery performance, causing a delayed recovery initiation and an impaired balance refinement after the recovery stepping when applied to ankle and hip muscles, respectively.

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.

Normalized stability time analysis within the boundaries between adults with and without fear of falling

BACKGROUND

The unilateral stance test, measured by the center of pressure (COP), has been widely used to identify balance deficits. However, there is a critical gap in understanding the specific COP thresholds on postural stability in adults with a fear of falling (FOF).

AIMS

To investigate the normalized stability time, which was defined as the ratio of time spent within stability boundaries to the total test duration, under different visual conditions and specific thresholds between adults with and without FOF.

METHODS

Twenty-one older adults with FOF and 22 control subjects completed the unilateral limb standing test in eyes-open and eyes-closed conditions. Normalized stability times were computed based on five pre-determined COP sway range thresholds: 10 mm, 15 mm, 20 mm, 25 mm, and 30 mm.

RESULTS

Receiver operating characteristic analysis determined the diagnostic accuracy of FOF. There were significant differences in the effects of both visual conditions (F = 46.88, p = 0.001) and threshold settings (F = 119.38, p = 0.001) on stability time between groups. The FOF group significantly reduced normalized stability time at the 10 mm COP threshold under eyes-closed conditions (t = - 1.95, p = 0.03).

DISCUSSION

The findings highlight the heightened sensitivity of the 10 mm COP threshold in identifying group variances in postural stability when eyes are closed. Moreover, the FOF group displayed a marked reduction in stability duration based on visual scenarios and normalized thresholds.

CONCLUSION

The study highlights the need to account for both COP boundaries and visual conditions in adults with FOF. When assessing postural control during unilateral stances, clinicians must also give attention to non-visual cues.

Biological Responses to Local Vibratory Stimulation for the Lower Legs and Lower Back and Criterion Values Based on Sweep Frequencies of Healthy Individuals: An Observational Study

Declining proprioceptive function is associated with problems such as lower back pain and falls. Therefore, we developed a vibration device using sweep frequency to evaluate several proprioceptors with different response frequency ranges. This study aimed to elucidate the biological responses of healthy individuals to vibratory stimulation at different sites and frequency ranges and to propose cutoff values to determine the decline in proprioceptive function. Mechanical vibration was separately applied to the lower legs and lower back, and proprioceptive function was evaluated by defining the ratio of the center of pressure (CoP) in the anteroposterior direction during mechanical vibration to that during no vibration in the three frequency ranges. The cut-off value was defined as the mean value, with the standard deviation subtracted for each indicator. The cut-off values were higher in the lower legs than in the lower back at all frequency ranges and in the 30-53 Hz and 56-100 Hz frequency ranges for both the lower legs and lower back. In healthy individuals, 9.9% and 8.6% were below the cut-off values in the 30-53 Hz and 56-100 Hz frequency ranges for the lower legs, respectively.

The Effects of Vibratory and Acoustic Stimulations on Postural Control in Healthy People: A Systematic Review

Research on human posture and balance control has grown in recent years, leading to continued advances in their understanding. The ability to maintain balance is attributed to the interplay of the visual, vestibular, and somatosensory systems, although an important role is also played by the auditory system. The lack or deficit in any of these systems leads to a reduced stability that may be counterbalanced by the integration of all the remaining sensory information. Auditory and vibratory stimulation have been found to be useful to enhance balance alongside daily activities either in healthy or pathological subjects; nevertheless, while widely investigated, the literature relating to these approaches is still fragmented. This review aims at addressing this by collecting, organising, and discussing all the literature to date on the effects of the various acoustic and vibratory stimulation techniques available on static upright posture in healthy subjects. In addition, this review intends to provide a solid and comprehensive starting point for all the researchers interested in these research areas. A systematic search of the literature was performed and a total of 33 articles (24 on vibratory stimulation and 9 on acoustic stimulation) were included in our analysis. For all articles, several elements were highlighted including: the study sample, the characteristics of the stimulations, the recording instruments, the experimental protocols, and outcomes. Overall, both stimulations analysed were found to have a positive effect on balance but more research is needed to align those alternative approaches to the traditional ones.

Factors associated with falls in patients with knee osteoarthritis: A cross-sectional study

Falls represent an important adverse effect associated with knee osteoarthritis and result in a significant financial burden on the healthcare system. Therefore, identification of fall predictors is essential to minimize fall incidence. However, few studies have investigated falls and fall predictors, particularly focused on the fear of falls and proprioception. In this study, we investigated significant fall predictors in patients with knee osteoarthritis in Malang, Indonesia. Our findings may serve as useful guidelines to develop geriatric fall prevention programs. This cross-sectional survey using purposive sampling was performed between April and July 2021 and included 372 participants. We recorded the following data: sociodemographic and medical history questionnaire responses, visual analog scale scores, Hopkins falls grading scale scores, Fall Efficacy Scale-International scores, proprioception test findings, knee injury and osteoarthritis outcome score (KOOS), range of motion (ROM), chair stand test and the timed up and go test performance. Data were analyzed using the chi-square and t tests, and multivariate logistic regression to determine significant fall predictors. Multivariate logistic regression analysis showed a lower risk of falls in patients with better proprioception and ROM than in the other groups (odds ratio 0.55 vs 0.96). The risk of falls was higher in patients with higher KOOS symptoms, fear of falls, diagnosis of low back pain and diabetes mellitus, and increased body mass index than in the other groups (odds ratio 1.41, 2.65, 1.27, 3.45, and 1.10, respectively. Our study shows that knee proprioception and ROM serve as protective factors against falls, whereas KOOS symptoms, fear of falls, low back pain, diabetes mellitus, and body mass index were associated with a high risk of falls, with diabetes mellitus and fear of falls being the most significant risk factors. These findings may be useful to policy makers to develop a fall prevention program that can be implemented in community health care centers across Indonesia to deliver individualized, person-centered care and improve fall prevention strategies through a systematic process comprising evaluation, intervention, and monitoring to minimize fall risk.

Impaired ankle inversion proprioception during walking is associated with fear of falling in older adults

Background

Ankle proprioception plays a critical role in lower limb movement control. However, the relationship between ankle proprioception and fear of falling (FOF) in older people is still unclear.

Objective

(1) This study aims to develop a new device for measuring ankle inversion proprioceptive discrimination sensitivity during walking, i.e., the Ankle Inversion Discrimination Apparatus–Walking (AIDAW), and assess the test–retest reliability of the AIDAW in both young and older adults; (2) to evaluate the discriminant validity of the measure by comparing ankle proprioception during walking between the two groups; and (3) to explore convergent validity by determining to what extent the AIDAW proprioceptive scores correlate with Fall Efficacy Scale-International (FES-I) scores.

Materials and methods

The AIDAW was purpose-built to test ankle inversion proprioceptive discrimination sensitivity during walking. The area under the receiver operating curve (AUC) was calculated as the proprioceptive discrimination score. In total, 54 adults volunteered. Test–retest reliability was evaluated in 12 young and 12 older adults, and another 15 young and 15 older adults completed the comparison study. FOF was assessed by using the FES-I.

Results

The test–retest reliability intraclass correlation coefficient ICC _(3,1) value for the whole group was 0.76 (95% CI: 0.52–0.89). The ICC values of the young and older groups were 0.81 (95% CI: 0.46–0.94) and 0.71 (95% CI: 0.26–0.91), respectively. The Minimal Detectable Change with 90% confidence (MDC₉₀) values for the young and older groups were 0.03 and 0.11, respectively. There was a significant difference between the AIDAW proprioceptive sensitivity scores for the young and older groups (0.78 ± 0.04 vs. 0.72 ± 0.08, F = 5.06, p = 0.033). Spearman’s correlation analysis showed that the FES-I scores were significantly and negatively correlated with the AIDAW scores (rho = −0.61, p = 0.015), with higher FOF associated with worse ankle proprioception.

Conclusion

The AIDAW is a reliable and valid device for measuring ankle proprioception during walking in both young and older adults. Ankle inversion proprioceptive discrimination sensitivity during walking was found to be impaired in the elderly compared to young adults. This impairment was found to be strongly associated with FOF, suggesting that assessment and intervention for ankle proprioception in this population are needed to reduce the risk of falls.

Electromyographic responses to unexpected Achilles tendon vibration-induced perturbations during standing in young and older people

This study aimed to investigate age-related differences in electromyographic (EMG) responses to unexpected Achilles tendon vibration (ATV) perturbations while standing blindfold. ATV with variable and random duration (12-15 s) and rest periods (20-24 s) was applied on 18 young and 16 older volunteers. The anterior/posterior center of pressure (CoP) and the soleus (SOL) and tibialis anterior (TA) EMG were analyzed for 1 s before and 8 s after the ATV onset and offset. ATV induced a posterior shift of CoP in both groups, with more pronounced shift in the older group. During ATV onset, the older group demonstrated less SOL and more TA EMG increase compared to the young group. During the first 0.5 s of ATV offset, SOL EMG was decreased in both age groups, while TA showed a burst of EMG activity that was greater in the older group. No difference in the latencies of EMG peaks or valleys was observed between the groups. It is concluded that ATV induces greater posterior CoP shift in older adults, and they adopt a recovery strategy, characterized by a decreased SOL activation and an increased TA activation. These differences are possibly attributed to the increased fear of falling, decreased limits of stability and reduced capacity of older people to reweight their sensory inflow when proprioception is distorted.

Reliability of hip joint position sense tests using a clinically applicable measurement tool in elderly participants with unilateral hip osteoarthritis

Hip joint proprioception is vital in maintaining posture and stability in elderly individuals. Examining hip joint position sense (JPS) using reliable tools is important in contemporary clinical practice. The objective of this study is to evaluate the intra-rater and inter-rater reliability of hip JPS tests using a clinically applicable measurement tool in elderly individuals with unilateral hip osteoarthritis (OA). Sixty-two individuals (mean age = 67.5 years) diagnosed with unilateral hip OA participated in this study. The JPS tests were evaluated using a digital inclinometer in hip flexion and abduction directions. The absolute difference between target and reproduced angle (repositioning error) in degrees was taken to measure JPS accuracy. The intraclass correlation coefficient (ICC (2.k), was used to assess the reliability. The Intra rater-reliability for hip JPS tests showed very good agreement in the lying position (hip flexion-ICC = 0.88–0.92; standard error of measurement (SEM) = 0.06–0.07, hip abduction-ICC = 0.89–0.91; SEM = 0.06–0.07) and good agreement in the standing position (hip flexion-ICC = 0.69–0.72; SEM = 0.07, hip abduction-ICC = 0.66–0.69; SEM = 0.06–0.08). Likewise, inter-rater reliability for hip JPS tests demonstrated very good agreement in the lying position (hip flexion-ICC = 0.87–0.89; SEM = 0.06–0.07, hip abduction-ICC = 0.87–0.91; SEM = 0.07) and good agreement in the standing position (hip flexion-ICC = 0.64–0.66; SEM = 0.08, hip abduction-ICC = 0.60–0.72; SEM = 0.06–0.09). The results support the use of hip JPS tests in clinical practice and should be incorporated in assessing and managing elderly participants with hip OA.

Cortical pathways during Postural Control: new insights from functional EEG source connectivity

Postural control is a complex feedback system that relies on vast array of sensory inputs in order to maintain a stable upright stance. The brain cortex plays a crucial role in the processing of this information and in the elaboration of a successful adaptive strategy to external stimulation preventing loss of balance and falls. In the present work, the participants postural control system was challenged by disrupting the upright stance via a mechanical skeletal muscle vibration applied to the calves. The EEG source connectivity method was used to investigate the cortical response to the external stimulation and highlight the brain network primarily involved in high-level coordination of the postural control system. The cortical network reconfiguration was assessed during two experimental conditions of eyes open and eyes closed and the network flexibility (i.e. its dynamic reconfiguration over time) was correlated with the sample entropy of the stabilogram sway. The results highlight two different cortical strategies in the alpha band: the predominance of frontal lobe connections during open eyes and the strengthening of temporal-parietal network connections in the absence of visual cues. Furthermore, a high correlation emerges between the flexibility in the regions surrounding the right temporo-parietal junction and the sample entropy of the CoP sway, suggesting their centrality in the postural control system. These results open the possibility to employ network-based flexibility metrics as markers of a healthy postural control system, with implications in the diagnosis and treatment of postural impairing diseases.

Isolated post-traumatic astereognosis: a case-based review

INTRODUCTION

Astereognosis is the tactile inability to recognize objects placed in the palms by touch with the eyes closed or blind-folded in the presence of intact primary sensory modalities. Stereognosis is usually considered a function of the contralateral sensory cerebral cortex. However, lesions of several anatomic areas and pathologic entities have been reported to be associated with astereognosis. Only two previous reports linked traumatic injury to isolated astereognosis: following surgical evacuation of traumatic parietal extradural hematoma and following bullet injury in the neck in 1992 and 1919, respectively.

METHODS AND RESULTS

All the pertinent literature was analyzed, focusing on the relevant definitions, clinical spectra, pathoanatomical processes, assessment, management, and outcomes of astereognosis. Also, an illustrative case was presented. The case highlights isolated post-traumatic left hand astereognosis in a 17-year-old boy following a blunt trauma to the head which resulted in a non-hemorrhagic contusion of the right post-central gyrus.

CONCLUSIONS

Post-traumatic isolated astereognosis is a rare and probably underreported sequel of traumatic brain injury. Neurosurgeons need to be more sensitive to the assessment and detection of subtle stereognostic deficits in general and in trauma patients in particular. Other anatomical areas, in addition to the contralateral post-central gyrus, may be considered in the pathogenesis of astereognosis with the involvement of the dorsal column medial lemniscus tract such as the brainstem, foramen magnum, and the cervical spinal cord. To the best of our knowledge, this rare case report is considered the second report on astereognosis following head trauma, and the third report on astereognosis following trauma in general.

Postural Stability in Individuals with and without Sacroiliac Joint Dysfunction Before and After Pelvic Belt Application

Background: Sacroiliac Joint Dysfunction (SIJD) is considered an origin of low-back pain. It can change the motor control strategy and postural control (PC). Objectives: We aimed to find any probable differences in PC between subjects with and without SIJD and determine the effects of the pelvic belt (PB) on PC. Methods: Thirty-eight subjects were assigned into two equal groups with and without SIJD. They started to walk from the place marked on a force plate for 10 seconds after hearing an auditory signal and performed three attempts for each foot. They repeated six more ones with PB. Raw data were imported to an excel software (version 2007) spreadsheet to calculate the reaction time (RT) and anticipatory postural adjustment (APA) as the components of PC. Results: Our results showed a significant difference in RT between the SIJD-affected and non-affected sides (P = 0.035), but there was no significant difference in APA (P = 0.057). There were significant differences in RT and APAs between the control and SIJD-affected side groups (P = 0.001 and P = 0.010, respectively). The PB application showed a significant difference in RT and APAs of the SIJD-affected side (P = 0.001 and P = 0.047, respectively). Conclusions: It seems pain could lead to the postural sway into instability and change the motor control strategy. The proprioception signals from the neuromuscular system of SIJ improved after PB. Therefore, PB, as a feasible tool, can be recommended for PC improvement.

Massage enhances recovery following exercise-induced muscle damage in older adults

To examine efficacy of cold water immersion (CWI) and massage as recovery techniques on joint position sense, balance, and fear of falling following exercise-induced muscle damage in older adults. Seventy-eight older men and women performed a single bout of strength training on the calf muscles (3 exercises with 4 sets of 10 reps with 75% of 1RM) to induce muscle damage. After the damaging exercise, participants received either a 15-minute massage on calf muscles, or a CWI of the lower limb in cold water (15 ± 1°C) for 15 minute, or passive rest. Interventions were applied immediately after the exercise protocol and at 24, 48, and 72 hours post-exercise. Muscle pain, calf muscle strength, joint position sense, dynamic balance, postural sway, and fear of falling were measured at each time point. Repeated application of massage after EIMD relieved muscle pain, attenuated the loss of muscle strength and joint position senses, reduce balance impairments, and fear of falling in older adults (P ≤ .05). However, repeated applications of CWI, despite relieving muscle pain (P ≤ .05), did not attenuate the loss of muscle strength, joint position senses, balance impairments, and fear of falling. CWI had only some modest effects on muscle pain, but massage attenuated EIMD symptoms and the related impairments in muscle strength, joint position sense, balance, and postural sway in untrained older individuals. Therefore, older exercisers who plan to participate in strength training can benefit from massage for recovery from muscle damage indices and balance to decrease falling risk during the days following strength training.

The effect of vibratory stimulation on the timed-up-and-go mobility test: a pilot study for sensory-related fall risk assessment

Effects of localized lower-extremity vibration on postural balance have been reported. The purpose of the current study was to investigate the effect of low-frequency vibration of calf muscles on the instrumented Timed-Up-and-Go (iTUG) test among older adults. Older adults were recruited and classified to low (n=10, age=72.9±2.8 years) and high fall risk (n=10, age=83.6±9.6) using STEADI. Vibratory system (30Hz or 40Hz), was positioned on calves along with wearable motion sensors. Participants performed the iTUG test three times, under conditions of no-vibration, 30Hz, and 40Hz vibration. Percentage differences in duration of iTUG components were calculated comparing vibration vs no-vibration conditions. Significant between-group differences were observed in iTUG (p=0.03); high fall risk participants showed reduction in the duration of turning (-10 % with 30Hz; p=0.15 and -15 % with 40Hz; p=0.03) and turning and sitting (-18 % with 30Hz; p=0.02 and -10 % with 40Hz; p=0.08). However, vibration increased turning (+18 % with 30Hz; p=0.20 and +27 % with 40Hz; p=0.12) and turning and sitting duration (+27 % with 30Hz; p=0.11 and +47 % with 40Hz; p=0.12) in low fall risk participants. Findings suggest that lower-extremity vibration affects dynamic balance; however, the level of this influence may differ between low and high fall risk older adults, which can potentially be used for assessing aging-related sensory deficits.

Influence of age on the frequency characteristics of the soleus muscle response to Achilles tendon vibration during standing

KEY POINTS

Proprioceptive sensory information from the ankle joint is critical for the control of upright posture and balance. We examined the influence of age (n = 54 healthy adults, 20-82 years old) on lower limb muscle responses to proprioceptive perturbations evoked by Achilles tendon vibration during standing. The frequency bandwidth of the muscle response became narrower, and the gain (the muscle response relative to the stimulus) and scaling (increases in response amplitude with increases in stimulus amplitude) decreased with age. Mechanics of the muscle-tendon unit (mechanical admittance) did not differ with age during standing, and thus probably did not mediate the age-related changes observed in soleus muscle responses to vibration. These findings add to our understanding of how altered proprioceptive responses may contribute to impaired mobility and falls with ageing.

ABSTRACT

Proprioceptive information from the ankle joint plays an important role in the control of upright posture and balance. Ageing influences many components of the sensorimotor system, which leads to poor mobility and falls. However, little is known about the influence of age on the characteristics of short latency muscle responses to proprioceptive stimuli during standing across frequencies that are encoded by muscle spindles. We examined the frequency characteristics of the soleus muscle response to noisy (10-115 Hz) Achilles tendon vibration during standing in 54 healthy adults across a broad age range (20-82 years). The results showed the frequency bandwidth of the soleus response (vibration-electromyography coherence) became progressively narrower with ageing. Coherence was significantly lower in middle-aged relative to young adults between ∼7-11 and 28-62 Hz, lower in older relative to middle-aged adults between ∼30-50 Hz and lower in older relative to young adults between ∼7-64 Hz. Muscle response gain was similar between age groups at low frequencies, although gain was lower in older relative to young adults between ∼28-54 Hz. Across the age range, the response amplitude (peak-to-peak cross-covariance) and the scaling of the response with stimulus amplitude were both negatively correlated with age. Muscle-tendon mechanics (admittance) did not differ with age, suggesting this did not mediate differences in soleus responses. Our findings suggest there is a progressive change in the soleus response to proprioceptive stimuli with ageing during standing, which could contribute to poorer mobility and falls.

Real-time Positioning Among Nursing Home Residents Living With Dementia: A Case Study

Dementia contributes to the development of pressure injuries (PrIs).

PURPOSE

This study describes the real-time body positions of 2 nursing home (NH) residents, residing in the United States and living with dementia, to inform development of PrI prevention strategies tailored to individual risk profiles.

METHODS

As part of a larger study, eligible residents were fitted with a triaxial accelerometer sensor placed on the anterior chest to monitor body positions 24-hours daily through a 4-week monitoring period. The current study used an observational, prospective design during routine repositioning events for 2 residents. A convenience sample of 2 residents from a single NH wing who were considered moderately at risk for PrI development (Braden Scale score 13-14) with a Brief Interview for Mental Status score in the severely impaired range were selected based on nursing staff recommendation.

RESULTS

Sensor data showed that both residents, although "chairfast" according to the Braden Scale, spent <5% in an upright position and the great majority of time reclining at an angle <50%. One (1) resident demonstrated a persistent side preference.

CONCLUSIONS

Wearable sensors are not a long-term solution for protecting those with dementia from PrI formation but do provide a crude picture of overall body positions throughout the 24-hour day that may inform individualized PrI prevention strategies. Studies including large samples of NH residents living with dementia are warranted.

Multi-System Physical Exercise Intervention for Fall Prevention and Quality of Life in Pre-Frail Older Adults: A Randomized Controlled Trial

Effective interventions for indicated fall prevention are necessary for older adults with frailty. We aimed to determine the effectiveness of a Multi-system Physical Exercise (MPE) for fall prevention and Health-Related Quality of Life (HRQOL) in pre-frail older adults. This randomized control trial with allocation concealment included 72 adults aged 65 and above, identified as pre-frailty and with mild and moderate fall risk scores measured by the Physiological Profile Assessment (PPA). Randomly, using block randomization, participants were divided into two groups: an MPE group (n = 36) and a control group (n = 36). The intervention consisted mainly of proprioception, muscle strengthening, reaction time, and balance training and was carried out three days per week for 12 weeks. The primary outcome was fall risk assessed using PPA at 12 weeks post-baseline and at a 24 week follow-up. Significant differences were found in the improvement in fall risk, proprioception, muscle strength, reaction time and postural sway, and fear of fall scores in the MPE group compared with controls at week 12 and 24. In addition, HRQOL had increased significantly in the MPE group in comparison to controls. The MPE program significantly increased muscle strength and improved proprioception, reaction time, and postural sway leading to fall risk reduction in older adults with pre-frailty. Therefore, the MPE program is recommended for used in day-to-day primary care practice in the pre-frail population.

Relationship between postural stability and fall risk in elderly people with lumbar spondylosis during local vibratory stimulation for proprioception: a retrospective study

Purpose: Reduced proprioception affects fall risks in elderly people with lumbar spondylosis. The decrease in proprioception in the trunk or lower legs may contribute to a decline in postural stability. We aimed to investigate the association between proprioceptive postural stability and fall risks in elderly individuals with lumbar spondylosis.Materials and Methods: In this retrospective study, the centre-of-pressure displacement was determined in elderly individuals with lumbar spondylosis during upright stance while standing on a Wii Balance Board with their eyes closed (fall-risk group, n = 55; non-fall-risk group, n = 60). Vibratory stimulations at 30 Hz were applied to the lumbar multifidus and gastrocnemius to evaluate the relative contributions of proprioceptive signals used in postural control (relative proprioceptive weighting ratio).Results: Compared with the non-fall-risk group, the fall-risk group displayed a high relative proprioceptive weighting ratio (p = 0.024). Relative proprioceptive weighting ratio (odds ratio, 1.1; 95% confidence interval: 1.004-1.109) was independently associated with fall risks after adjusting for confounding factors. Among variables related to fall risk, the relative proprioceptive weighting ratio was a significant factor (p < 0.035).Conclusion: The fall-risk group of elderly individuals with lumbar spondylosis was dependent on the ankle strategy. The fall risk in elderly people with lumbar spondylosis could be due to over-dependence on the input from muscle spindles in the gastrocnemius.

Can motor function uncertainty and local instability within upper-extremity dual-tasking predict amnestic mild cognitive impairment and early-stage Alzheimer's disease?

In this study, we examined the uncertainty and local instability of motor function for cognitive impairment screening using a previously validated upper-extremity function (UEF). This approach was established based upon the fact that elders with an impaired executive function have trouble in the simultaneous execution of a motor and a cognitive task (dual-tasking). Older adults aged 65 years and older were recruited and stratified into 1) cognitive normal (CN), 2) amnestic MCI of the Alzheimer's type (aMCI), and 3) early-stage Alzheimer's Disease (AD). Participants performed normal-paced repetitive elbow flexion without counting and while counting backward by ones and threes. The influence of cognitive task on motor function was measured using uncertainty (measured by Shannon entropy), and local instability (measured by the largest Lyapunov exponent) of elbow flexion and compared between cognitive groups using ANOVAs, while adjusting for age, sex, and BMI. We developed logistic ordinal regression models for predicting cognitive groups based on these nonlinear measures. A total of 81 participants were recruited, including 35 CN (age = 83.8 ± 6.9), 30 aMCI (age = 83.9 ± 6.9), and 16 early AD (age = 83.2 ± 6.6). Uncertainty of motor function demonstrated the strongest associations with cognitive impairment, with an effect size of 0.52, 0.88, and 0.51 for CN vs. aMCI, CN vs. AD, and aMCI vs. AD comparisons, respectively. Ordinal logistic models predicted cognitive impairment (aMCI and AD combined) with a sensitivity and specificity of 0.82. The findings accentuate the potential of employing nonlinear dynamical features of motor functions during dual-tasking, especially uncertainty, in detecting cognitive impairment.

A study protocol for a randomized controlled trial evaluating vibration therapy as an intervention for postural training and fall prevention after distal radius fracture in elderly patients

Background

Fractures of the distal radius are one of the most common osteoporotic fractures in elderly men and women. These fractures are a particular health concern amongst the elderly, who are at risk of fragility fractures, and are associated with long-term functional impairment, pain and a variety of complications. This is a sentinel event, as these fractures are associated with a two to four times increased risk of subsequent hip fractures in elderly patients. This is an important concept, as it is well established that these patients have an increased risk of falling. Fall prevention is therefore crucial to decrease further morbidity and mortality. The purpose of this study is to investigate the effect of low-magnitude high-frequency vibration (LMHFV) on postural stability and prevention of falls in elderly patients post distal radius fracture.

Methods

This is a prospective single-blinded randomized controlled trial. Two hundred patients will be recruited consecutively with consent, and randomized to either LMHFV (n = 100) or a control group (n = 100). The primary outcome is postural stability measured by the static and dynamic ability of patients to maintain centre of balance on the Biodex Balance System SD. Secondary outcomes are the occurrence of fall(s), the health-related quality of life 36-item short form instrument, the Timed Up and Go test for basic mobility skills, compliance and adverse events. Outcome assessments for both groups will be performed at baseline (0 month) and at 6 weeks, 3 months and 6 months time points.

Discussion

Previous studies have stressed the importance of reducing falls after distal radius fracture has occurred in elderly patients, and an effective intervention is crucial. Numerous studies have proven vibration therapy to be effective in improving balancing ability in normal patients; However, no previous study has applied the device for patients with fractures. Our study will attempt to translate LMHFV to patients with fractures to improve postural stability and prevent recurrent falls. Positive results would provide a large impact on the prevention of secondary fractures and save healthcare costs.

Trial registration

ClinicalTrials.gov, NCT03380884. Registered on 21 December 2017.

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.

The association between cognition and dual-tasking among older adults: the effect of motor function type and cognition task difficulty

Background

Dual-task actions challenge cognitive processing. The usefulness of objective methods based on dual-task actions to identify the cognitive status of older adults has been previously demonstrated. However, the properties of select motor and cognitive tasks are still debatable. We investigated the effect of cognitive task difficulty and motor task type (walking versus an upper-extremity function [UEF]) in identifying cognitive impairment in older adults.

Methods

Older adults (≥65 years) were recruited, and cognitive ability was measured using the Montreal Cognitive Assessment (MoCA). Participants performed repetitive elbow flexion under three conditions: 1) at maximum pace alone (Single-task); and 2) while counting backward by ones (Dual-task 1); and 3) threes (Dual-task 2). Similar single- and dual-task gait were performed at normal speed. Three-dimensional kinematics were measured for both motor functions using wearable sensors.

Results

One-hundred older adults participated in this study. Based on MoCA score <20, 21 (21%) of the participants were considered cognitively impaired (mean age =86±10 and 85±5 for cognitively impaired and intact participants, respectively). Within ANOVA models adjusted with demographic information, UEF dual-task parameters, including speed and range-of-motion variability were significantly higher by 52% on average, among cognitively impaired participant (p<0.01). Logistic models with these UEF parameters plus age predicted cognitive status with sensitivity, specificity, and area under curve (AUC) of 71%, 81% and 0.77 for Dual-task 1. The corresponding values for UEF Dual-task 2 were 91%, 73% and 0.81, respectively. ANOVA results were non-significant for gait parameters within both dual-task conditions (p>0.26).

Conclusion

This study demonstrated that counting backward by threes within a UEF dual-task experiment was a pertinent and challenging enough task to detect cognitive impairment in older adults. Additionally, UEF was superior to gait as the motor task component of the dual-task. The UEF dual-task could be applied as a quick memory screen in a clinical setting.

Preserved multisensory body representations in advanced age

The internal representation of the body emerges via the integration of multisensory body cues. Sensory signal transfer and the ability to integrate multisensory information deteriorate significantly with increasing age. However, there is little empirical evidence on age-related changes in body representations based on multisensory integration. Here, we used a standard paradigm for evaluating body representations based on multisensory integration, the rubber hand illusion, and compared the amount of proprioceptive drift and changes in perceived body ownership triggered by the integration of visual, tactile, and proprioceptive cues between younger and older adults. To account for potential age-related differences in the temporal stability of the illusion, proprioceptive drift was measured at five different time points. Our results show that older adults used synchronous visuo-tactile cues similarly to younger adults to update both the position of their own hand, and their feeling of ownership over the artificial hand. Independent of visuo-tactile synchrony, older adults perceived their hand as closer to their body than younger adults did, and showed a less stable representation of this in-depth hand position. This proprioceptive bias towards the body did not correlate with the strength of the illusion. Our results indicate that the integration of visual and tactile cues is largely preserved in advanced age when used to update limb position, whereas proprioception worsens with age. This may be linked to two different pathways that underlie changes in body representations over the life span.

Bone health, muscle properties and stretch-shortening cycle function of young and elderly males

The aim of this study was to examine bone, muscle, strength and stretch-shortening cycle (SSC) performance in young and elderly individuals with an ankle model to elucidate potential effects of ageing that have been suggested to influence fall risk. Moderately active young (n=10; age=22.3±1.3 yrs) and elderly (n=8; age=67.5±3.3 yrs) males completed a peripheral quantitative computed tomography scan on the dominant lower leg, maximal voluntary isometric plantarflexions (MVIP) and SSC tasks: a countermovement hop and drop hops from three different heights. Bone stress-strain index at 14% of the lower leg and muscle density, muscle cross-sectional area and muscle+bone cross-sectional area at 66% of the lower leg were all significantly greater (p≤0.05) in younger males than elderly males. Younger males also had significantly greater rate of force development and peak force during the MVIP when compared to the elderly. Younger males achieved significantly higher forces, velocities and hop heights during all SSC tasks than elderly males. Such information provides support for greater specificity in exercise interventions that prevent lower leg morphological and functional decrements in the ageing population.

Postural Strategy in Elderly, Middle-Aged, and Young People during Local Vibratory Stimulation for Proprioceptive Inputs

Proprioceptive input may greatly affect postural stability. However, the proprioceptive postural strategy in elderly, middle-aged, and young people has not been investigated sufficiently. Hence, in this study, we aimed to investigate differences in proprioceptive postural strategies of elderly, middle-aged, and young people. The center of pressure displacement was determined in 23 elderly, 23 middle-aged, and 23 young people during upright stance on a balance board with their eyes closed. Vibratory stimulations at 30, 60, and 240 Hz were applied to the lumbar multifidus (LM) and gastrocnemius (GS) muscles to evaluate the contributions of different proprioceptive signals used in balance control. Compared with middle-aged and young people, elderly people showed a high dependence on postural control of the GS at 30 Hz (p-values: Young and elderly: 0.033; middle-aged and elderly: 0.001). Moreover, compared with young people, elderly people were more dependent on postural control of the LM at 240 Hz (p = 0.016). There were no significant differences with respect to the GS at 60 and 240 Hz, and with respect to the LM at 30 and 60 Hz between the elderly, young, and middle-aged people. Thus, the postural control strategy of elderly people depends on the GS at 30 Hz.

Upper-extremity function prospectively predicts adverse discharge and all-cause COPD readmissions: a pilot study

Background

Frailty can inform management approaches for individuals with COPD. However, inpatient measures of frailty are seldom employed because they are time-consuming or inapplicable for bed-bound patients. We investigated the feasibility and potential of an innovative sensor-based upper-extremity function (UEF) test for frailty assessment in predicting adverse outcomes.

Methods

Hospitalized patients with COPD-related exacerbations (aged ≥55 years) were recruited and performed the UEF test within 24 hours of admission. UEF parameters were obtained and fed into our previously developed frailty model to calculate frailty status (non-frail, pre-frail, and frail) and frailty score (0: extreme resilience to 1: extreme frailty). In-hospital (length of stay) and post-discharge (discharge disposition, 30-day exacerbation with treatment, and all-cause 30-day readmission) outcomes were collected. Associations between UEF frailty and outcomes were investigated using ANOVA and logistic models adjusted for demographic data.

Results

In total, 42 patients were recruited. All participants were able to perform the UEF test. Based on UEF, participants were stratified into three groups of non-frail (n=6, frailty score =0.18±0.09), pre-frail (n=14, frailty score =0.45±0.09), and frail (n=22, frailty score =0.78±0.11). Both frailty status and frailty score were significantly associated with unfavorable discharge disposition (P<0.005) and all-cause 30-day readmission (P<0.05). On the other hand, UEF frailty measures were associated with neither hospital length of stay (P>0.5) nor 30-day exacerbation with treatment (P>0.70). Age was only significantly associated with unfavorable discharge disposition (P=0.048).

Conclusion

In agreement with previous work, the current findings underline the importance of measuring frailty for risk-stratification of COPD patients. The UEF was feasible and easily performed among all hospitalized COPD patients. In this study, we have shown that, using our quick and objective frailty measures, COPD patients can be prospectively risk-stratified in terms of unfavorable discharge disposition and all-cause 30-day readmissions.