Aging of the somatosensory system: a translational perspective

Plantar cutaneous sensation is independently associated with postural balance and lower limb motor function in older adults: the Shizuoka study

PURPOSE

A relationship between decreased plantar cutaneous sensation and impaired balance function has been reported in patients with peripheral neuropathy and diabetes. This cross-sectional study aimed to investigate the relationship between plantar sensation and postural balance, as well as the association between plantar sensation and sarcopenia-related motor function in community-dwelling older adults.

METHODS

The participants included 1659 community-dwelling older adults with a mean age of 74 ± 5 years, of which 43% were male patients. Plantar cutaneous sensation thresholds were assessed using an automatic plantar sensation testing device. Postural balance was measured using one-leg standing (OLS) time. Grip strength, five-time sit-to-stand (STS) time, and normal gait speed were measured as components of muscle strength and physical function related to sarcopenia. The skeletal muscle mass index (SMI) and leg phase angle were obtained using bioelectrical impedance analysis.

RESULTS

Age, sex, body mass index, and leg phase angle, but not SMI and grip strength, were independently associated with the plantar sensation threshold. Plantar sensation threshold was independently associated with the OLS time (P = 0.001) and STS time (P = 0.001) after adjusting for potential confounders. No significant association was found between plantar sensation threshold and normal gait speed (P = 0.741).

CONCLUSION

Plantar sensation was independently associated with postural balance and lower limb function in community-dwelling older adults. The assessment of plantar sensation could be useful for identifying factors contributing to poor postural balance and lower limb motor function.

Influence of age and feedback modality on the proprioceptive sense of force: insights from motor unit recordings

The primary purpose of our study was to compare the influence of feedback modality (visual vs. auditory) on force-reproduction accuracy in middle-aged and older adults. As a secondary objective, we investigated whether expected differences would be reflected in the neural drive sent to a hand muscle during the task. Participants (n = 42; 40-84 yr) performed a force-reproduction task with the first dorsal interosseus muscle at two target forces [5% and 20% of maximal voluntary contraction (MVC)]. Each trial involved a target phase that was guided by visual or auditory feedback and then a reproduction phase without feedback. The neural drive was characterized by measures of force steadiness and motor unit discharge characteristics during the target phase. Force-reproduction accuracy at the lower target force declined with increasing age and with visual feedback compared with auditory feedback. In contrast, there was no evidence of an effect of age or condition on force-reproduction accuracy at the moderate target force (20% MVC). Force steadiness was worse and motor unit coherence in the delta and beta bands was greater when the task was guided by auditory feedback at both target forces. These findings indicate that greater accuracy during the low-force task in the auditory-feedback condition was accompanied by a noisier control signal and differences in motor unit coherence in the delta and beta bands during the target phase.NEW & NOTEWORTHY The sense of force can be assessed with force-reproduction tasks, which typically involve visual feedback of the applied force during the target phase. Middle-aged and older adults improved force-reproduction accuracy when using auditory instead of visual feedback. This effect was accompanied by an increase in motor unit coherence in the beta band. This provides evidence for different sensorimotor processing of proprioceptive inputs when these sensory modalities are used to provide feedback of the applied force.

Paired corticospinal-motoneuronal stimulation enhances ballistic motor learning and corticospinal plasticity in older adults

Late adulthood is accompanied by declines in manual motor performance and reduced neuroplasticity, which can influence the effects of motor practice and learning. Corticomotoneuronal (CM) connectivity can be targeted non-invasively through individualized paired corticospinal-motoneuronal stimulation (PCMS) to prime ballistic motor learning in young adults. However, the priming effects of PCMS on motor output and ballistic motor learning in older adults remain unexplored. Part one of this study investigates ballistic motor performance and learning in young (20-30 years) and older (65-75 years) adults as within-session changes in peak acceleration of rapid index finger flexions and delayed retention 1 week later. The results demonstrate that older adults display lower maximal acceleration compared to young adults and smaller improvements with practice, indicating inferior learning and low levels of delayed retention. Part two of the study investigates the effects of PCMS on motor learning and corticospinal excitability in older adults. Corticospinal excitability was assessed throughout the experiment by recording motor evoked potentials from the first dorsal interosseous. PCMS increased subsequent ballistic learning and corticospinal excitability after practice compared to SHAM. Importantly, combined PCMS and motor practice also enhanced long-term retention, and performance remained enhanced 7 days later. This means that PCMS effectively reinstated the otherwise absent long-term learning in older adults. We demonstrate that PCMS primes experience-dependent plasticity accompanying motor learning resulting in long-term benefits on motor performance in older adults. These findings highlight the potential of PCMS to enhance the effects of motor practice and benefit functional abilities in older adults. KEY POINTS: Late adulthood is associated with reduced activation of spinal motoneurons during vigorous movements, resulting in slower and less precise movements. Older adults (aged 65-75 years) display lower ballistic motor performance compared to younger adults (aged 20-30 years); furthermore, older adults exhibit smaller improvements during practice, and lower retention. A single session of paired corticospinal-motoneuronal stimulation (PCMS) increases corticospinal excitability and primes within-session ballistic motor learning in older adults. A single session of PCMS improves long-term retention following ballistic motor learning. We provide proof-of-principle that PCMS represents a potential strategy to enhance the effects of motor practice and counteract age-related decline in motor function.

Contributions and future potential of animal models for geroscience research on sensory systems

Sensory systems mediate our social interactions, food intake, livelihoods, and other essential daily functions. Age-related decline and disease in sensory systems pose a significant challenge to healthy aging. Research on sensory decline in humans is informative but can often be difficult, subject to sampling bias, and influenced by environmental variation. Study of animal models, including mice, rats, rabbits, pigs, cats, dogs, and non-human primates, plays a complementary role in biomedical research, offering advantages such as controlled conditions and shorter lifespans for longitudinal study. Various species offer different advantages and limitations but have provided key insights in geroscience research. Here we review research on age-related decline and disease in vision, hearing, olfaction, taste, and touch. For each sense, we provide an epidemiological overview of impairment in humans, describing the physiological processes and diseases for each sense. We then discuss contributions made by research on animal models and ideas for future research. We additionally highlight the need for integrative, multimodal research across the senses as well as across disciplines. Long-term studies spanning multiple generations, including on species with longer life spans, are also highly valuable. Overall, integrative studies of appropriate animal models have high translational potential for clinical applications, the development of novel diagnostics, therapies, and medical interventions and future research will continue to close gaps in these areas. Research on animal models to improve understanding of the biology of the aging senses and improve the healthspan and additional research on sensory systems hold special promise for new breakthroughs.

Skin tactile perception is associated with longitudinal gait performance in middle-aged and older Japanese community dwellers

BACKGROUND

Skin tactile perception may indicate frailty in older adults. Although gait performance is crucial for diagnosing frailty, its association with skin tactile perception has not yet been explored.

OBJECTIVES

To examine the association between skin tactile perception and changes in step length, cadence, and gait speed in middle-aged and older adults.

DESIGN

A longitudinal study (mean follow-up: 10.8 years) SETTING: Community-based survey PARTICIPANTS: A total of 1,403 middle-aged and older adults (aged 40-79 years, 53.6 % men) from the National Institute for Longevity Sciences-Longitudinal Study of Aging were included in this study. These participants completed the baseline survey (1997-2000) and at least two follow-up surveys (2000-2012), had no history of cerebrovascular disease, rheumatoid arthritis, or Parkinson's disease, and had complete data with no outliers in skin tactile perception measurements.

MEASUREMENTS

Skin tactile perception was assessed using a two-point discrimination test. Step length (cm), cadence (steps/min), and gait speed (m/min) were evaluated on an 11-m walkway at a usual speed.

RESULTS

The mean age of participants was 56.4 years. After full adjustment, mixed-effects models with splines revealed that the association between skin tactile perception and gait parameters varied with age. In adults aged 60 and above, we observed non-linear relationships between skin tactile perception and gait parameters. A consistent inflection point around 10 mm in tactile perception was identified across different age groups and gait parameters.

CONCLUSIONS

Among community-dwelling middle-aged and older Japanese adults, skin tactile perception was associated with changes in gait parameters, particularly in those aged 60 and above. The 10-mm threshold in tactile perception may serve as a critical indicator for predicting changes in gait performance. Skin tactile perception tests may prove clinically useful for screening patients at elevated risk of impaired gait performance.

Movement control of the cervical spine declines with aging: a cross-sectional study

BACKGROUND

Previous studies suggest that cervical spine position sense declines with age, while the relationship between aging and cervical spine movement control remains unknown.

OBJECTIVE

To investigate the relationship between age and cervical spine movement control in asymptomatic adults.

METHODS

One hundred five asymptomatic adults (21-79 years old) were included. The Butterfly test (performed with an inertial measurement unit) was used to assess movement control of the cervical spine, in which participants tracked an unpredictable moving target with active head and neck movements at three different movement path difficulty levels (3 repetitions each). The determined parameters were amplitude accuracy (AA), time on target (ToT), undershoot (U) and overshoot (O). Spearman's rank correlation coefficient and simple linear regression analysis were used to assess the relationship between age and each parameter.

RESULTS

A significant relationship was demonstrated between advancing age and the AA, ToT and U parameters for all three movement path difficulty levels (p ≤ .001), but not for the O parameter (p > .05). Advancing age explained 19.8-30.4%, 24.5-30.8% and 33.7-37.2% of the variance in the AA, ToT, and U parameters, respectively.

CONCLUSION

The results suggest that cervical spine movement control declines with aging in an asymptomatic population. Clinicians may need to monitor potential deficits in cervicocephalic kinesthesia in older asymptomatic adults, as these impairments may have a considerable impact on their functional abilities.

Individual joint contributions to forward propulsion during treadmill walking in women with hip osteoarthritis

As we age, reliance on the ankle musculature for push-off during walking reduces and increased reliance on the hip musculature is observed. It is unclear how joint pathology like osteoarthritis may affect this distal-to-proximal redistribution of propulsion. Here, we revisited a proof-of-concept study to study the effect of split-belt treadmill training, designed to reduce step length asymmetry, on forward propulsion during walking. Eleven women with hip osteoarthritis and five age-matched control participants walked on an instrumented split-belt treadmill at their preferred speed (hip osteoarthritis: 0.73 ± 0.11 m/s; controls: 0.59 ± 0.26 m/s). Women with hip osteoarthritis had less ankle power and propulsive force than controls, and greater hip contributions to forward propulsion on their involved limb. Following split-belt treadmill training, propulsive force increased on the involved limb. Five of 11 participants experienced a change in redistribution ratio that was greater than the minimal clinically meaningful difference. These "responders" had greater variability in pre-training redistribution ratio compared to non-responders. Women with hip osteoarthritis had poorer propulsive gait mechanics than controls yet split-belt treadmill training improved propulsive force. Redistribution ratio also changed in participants with high baseline variability. Our results suggest that split-belt treadmill training may be beneficial to people with hip osteoarthritis who have high variability in walking parameters. Further, the age-related shift to increased hip contributions to propulsion across populations of older adults may be due to increased variability during walking.

Older Individuals Do Not Show Task Specific Variations in EEG Band Power and Finger Force Coordination

OBJECTIVE

Controlling and coordinating finger force is crucial for performing everyday tasks and maintaining functional independence. Aging naturally weakens neural, muscular, and musculoskeletal systems, leading to compromised hand motor function. This decline reduces cortical activity, finger force control and coordination in older adults.

OBJECTIVE

To investigate independently the EEG band power and finger force coordination in older individuals and compare the results with young healthy adults.

METHODS

Twenty healthy young adults aged 20-30 (26.96 ± 2.68) and fourteen older adults aged 58-72 (62.57 ± 3.58) participated in this study. Participants held the instrumented handle gently for five seconds then lifted and held it for an additional five seconds in the two conditions: fixed (thumb platform secured) and free condition (thumb platform may slide on slider).

RESULTS

In the older individuals there was no difference observed in the finger force synergy indices, and EEG beta band power between the two task conditions. However, in the young group synergy indices and EEG beta band power were less in free condition compared to fixed condition. Additionally, in the fixed condition, older adults showed a reduced synergy indices and reduced EEG beta band power than the young adults.

CONCLUSION

Older participants exhibited consistent synergy indices and beta band power across conditions, while young adults adjusted strategies based on tasks. Task-dependent finger force synergy indices were observed in young adults, contrasting with older individuals Additionally, it is suggested that EEG band power and synergy indices may be related, indicating potential associations between EEG activity and finger force coordination.

Aging Alters the Sense of Force but Not the Sense of Position in the Wrist and Ankle Joints

INTRODUCTION

The impact of aging on proprioceptive senses remains an open question. As the senses of position and force may rely on different neural substrates, we investigated the effect of aging on both senses to provide original and more comprehensive data on age-related changes in proprioception.

METHODS

The senses of position and force were assessed in several conditions using position- and force-reproduction tasks in young (20-40 years) and older (60-90 years) adults in the wrist (experiment 1, n = 41, 20 older adults) and ankle joints (experiment 2, n = 46, 24 older adults).

RESULTS

In both experiments, older adults exhibited larger force-reproduction errors than young adults at low (5% maximal force, p < 0.001) but not moderate forces (20% maximal force, p > 0.056). No age-related decline was observed for position-reproduction errors (p > 0.30), regardless of movement amplitude. Rare weak-to-moderate correlations were observed between position- and force-reproduction errors (r ≤ 0.53, p ≥ 0.009).

CONCLUSION

In wrist and ankle joints, the age-related decline in proprioception is limited to the sense of force, especially for low forces. This nonuniform decline in proprioception across proprioceptive senses and testing conditions could reflect a decline in the central processing of proprioceptive information.

Aging-associated sensory decline and Alzheimer's disease

Multisensory decline is common as people age, and aging is the primary risk of Alzheimer's Disease (AD). Recent studies have begun to shed light on the possibility that age-related sensory decline could accelerate AD pathogenesis, or be a prodromal indicator of AD. Sensory impairments, specifically in taste and smell, often emerge before cognitive symptoms in AD, indicating their potential as early biomarkers. Olfactory dysfunction has been frequently associated with AD and may offer valuable insights into early detection. Hearing impairment is significantly associated with AD, but its causal impact on AD progression remains unclear. The review also discusses visual and tactile deficits in AD, including retinal thinning and changes in tactile perception, highlighting their links to disease progression. Focusing on molecular mechanisms, the review explores the roles of amyloid-β (Aβ) accumulation and tau protein pathology in sensory decline and their bidirectional relationship with AD. In summary, the evidence presented conclusively supports advocating for an integrated approach to understanding AD and sensory decline, to enhance early detection, implementing preventive strategies, and developing therapeutic interventions for AD. This approach underscores the significance of sensory health in addressing neurodegenerative diseases, particularly AD.

A multi-modal evaluation of experimental pain and psychological function in women with carpometacarpal osteoarthritis

Objective

Thumb carpometacarpal osteoarthritis (CMC1 OA) is a prevalent and debilitating condition that lacks effective treatments. Understanding the multidimensional pain experience across CMC1 OA disease stages is crucial to improving treatment outcomes. This study examined how radiographic CMC1 OA severity is associated with physical, psychological, and somatosensory function.

Method

Thirty-one women with early-stage (Eaton-Littler 1-2) or end-stage (Eaton-Littler 3-4) radiographic CMC1 OA completed validated questionnaires to assess pain, disability, and psychological function. Additionally, experimental pain was measured in each participant using quantitative sensory testing (QST) (mechanical, pressure, vibratory, thermal) at seven body sites (thenar, hypothenar, brachioradialis bi-laterally; quadriceps on affected side). Cohort differences (early-vs. end-stage) across all variables were analyzed using a multivariable modeling approach that included fixed effects and interactions; notably, age was controlled as a confounder.

Results

End-stage CMC1 OA participants had higher scores in the pain (p ​= ​0.01) and function (p ​= ​0.02) portions of the AUSCAN assessment, self-reported disability of the DASH questionnaire (p ​= ​0.04), and painDETECT scores (p ​= ​0.03), indicating greater pain and disability compared to early-stage participants. Additionally, end-stage CMC1 OA participants demonstrated reduced vibratory detection and heat pain thresholds at multiple body sites (p's ​< ​0.05), with significant interactions observed across the mechanical and cold stimuli.

Conclusion

Findings revealed women with end-stage CMC1 OA exhibited increased neuropathic pain characteristics and somatosensory loss compared to those with early-stage CMC1 OA. These results underscore the importance of addressing both peripheral and centralized pain mechanisms and the need for multimodal approaches in the treatment of CMC1 OA.

The effect of age and proprioceptive illusion susceptibility on gait

OBJECTIVE

Age-related gait decline has been associated with impaired proprioception, one's internal awareness of spatial location and movement. Although impaired proprioception has further been linked to greater susceptibility to proprioceptive illusions, it is unclear the impact such susceptibility has on gait and its interaction with age. The purpose of this study was to address these uncertainties.

METHODS

We measured proprioceptive illusions induced by muscle spindle manipulation and gait in young and older adults. We also compared illusory measures with traditionally used joint position matching to examine if illusory susceptibility can reveal proprioceptive impairments.

RESULTS

We found no effect of age on proprioceptive illusion susceptibility or joint position matching error. Compared to non-perceivers, illusion perceivers across both age groups showed greater joint matching error, suggesting reduced proprioceptive acuity. Consistent with previous studies, older adults had reduced cadence, gait velocity, and step length compared to young adults in both single- and dual-task walking. Interestingly, illusion perceivers, regardless of age, showed reduced cadence and step width compared to non-perceivers.

CONCLUSIONS

Our results suggest that gait impairments observed in those who perceive these proprioceptive illusions are age-independent, potentially rooted in deteriorated proprioception.

SIGNIFICANCE

This is the first study to examine these relations.

Balance training in older adults enhances feedback control after perturbations

Background

As we age, avoiding falls becomes increasingly challenging. While balance training can mitigate such challenges, the specific mechanisms through which balance control improves remains unclear.

Methods

We investigated the impact of balance training in older adults on feedback control after perturbations, focusing on kinematic balance recovery strategies and muscle synergy activation. Twenty older adults aged over 65 underwent short-term (one session) and long-term (3-weeks, 10 sessions) balance training, and their recovery from unpredictable mediolateral perturbations was assessed. Perturbations consisted of 8° rotations of a robot-controlled platform on which participants were balancing on one leg. We measured full-body 3D kinematics and activation of 15 leg and trunk muscles, from which linear and rotational kinematic balance recovery responses and muscle synergies were obtained.

Results

Our findings revealed improved balance performance after long-term training, characterized by reduced centre of mass acceleration and (rate of change of) angular momentum. Particularly during the later stage of balance recovery the use of angular momentum to correct centre of mass displacement was reduced after training, decreasing the overshoot in body orientation. Instead, more ankle torque was used to correct centre of mass displacement, but only for perturbations in medial direction. These situation and strategy specific changes indicate adaptations in feedback control. Activation of muscle synergies during balance recovery was also affected by training, specifically the synergies responsible for leg stiffness and ankle torques. Training effects on angular momentum and the leg stiffness synergy were already evident after short-term training.

Conclusion

We conclude that balance training in older adults refines feedback control through the tuning of control strategies, ultimately enhancing the ability to recover balance.

Age differences in spatial memory are mitigated during naturalistic navigation

Spatial navigation deficits are often observed among older adults on tasks that require navigating virtual reality (VR) environments on a computer screen. We investigated whether these age differences are attenuated when tested in more naturalistic and ambulatory virtual environments. In Experiment 1, young and older adults navigated a variant of the Morris Water Maze task in each of two VR conditions: a desktop VR condition which required using a mouse and keyboard to navigate, and an ambulatory VR condition which permitted unrestricted locomotion. In Experiment 2, we examined whether age- and VR-related differences in spatial performance were affected by the inclusion of additional spatial cues. In both experiments, older adults navigated to target locations less precisely than younger individuals in the desktop condition. Age differences were significantly attenuated, however, when tested in the ambulatory VR environment. These findings underscore the importance of developing naturalistic assessments of spatial memory and navigation.

Alpha band oscillations in common synaptic input are explanatory of the complexity of isometric knee extensor muscle torque signals

We investigated whether the strength of oscillations in common synaptic input was explanatory of knee extensor (KE) torque signal complexity during fresh and fatigued submaximal isometric contractions, in adults aged from 18 to 90 years. The discharge times of motor units were derived from the vastus lateralis muscle of 60 participants using high-density surface EMG, during 20 s isometric KE contractions at 20% of maximal voluntary contraction, performed before and after a fatiguing repeated isometric KE contraction protocol at 60% of maximal voluntary contraction. Within-muscle coherence Z-scores were estimated using frequency-domain coherence analysis, and muscle torque complexity was assessed using multiscale entropy analysis and detrended fluctuation analysis. Alpha band (5-15 Hz) coherence was found to predict 23.1% and 31.4% of the variance in the complexity index under 28-scales (CI-28) and detrended fluctuation analysis α complexity metrics, respectively, during the fresh contractions. Delta, alpha and low beta band coherence were significantly increased due to fatigue. Fatigue-related changes in alpha coherence were significantly predictive of the fatigue-related changes in CI-28 and detrended fluctuation analysis α. The fatigue-related increase in sample entropy from scales 11 to 28 of the multiscale entropy analysis curves was significantly predicted by the increase in the alpha band coherence. Age was not a contributory factor to the fatigue-related changes in within-muscle coherence and torque signal complexity. These findings indicate that the strength of alpha band oscillations in common synaptic input can explain, in part, isometric KE torque signal complexity and the fatigue-related changes in torque signal complexity.

Cognitive functions explain discrete parameters of normal walking and dual-task walking, but not postural sway in quiet stance among physically active older people

BACKGROUND

Postural control is dependent on the central nervous system's accurate interpretation of sensory information to formulate and execute adequate motor actions. Research has shown that cognitive functions are associated with both postural control and fall risk, but specific associations are not established. The aim of this study was to explore how specific components of everyday postural control tasks are associated with both general and specific cognitive functions.

METHODS

Forty-six community-dwelling older adults reported their age, sex, physical activity level, falls and fall-related concerns. The following cognitive aspects were assessed: global cognition, executive functions, processing speed and intraindividual variability. Postural control was quantified by measuring postural sway in quiet stance, walking at a self-selected pace, and walking while performing a concurrent arithmetical task. Separate orthogonal projections of latent structures models were generated for each postural control outcome using descriptive and cognitive variables as explanatory variables.

RESULTS

Longer step length and faster gait speed were related to faster processing speed and less intraindividual variability in the choice reaction test. Moreover, longer step length was also related to less fall-related concerns and less severe fall-related injuries, while faster gait speed was also related to female sex and poorer global cognition. Lower dual-task cost for gait speed was explained by the executive function inhibition and faster processing speed. Postural sway in quiet stance was not explained by cognitive functions.

CONCLUSIONS

Cognitive functions explained gait speed and step length during normal walking, as well as the decrease of gait speed while performing a concurrent cognitive task. The results suggest that different cognitive processes are important for different postural control aspects. Postural sway in quiet stance, step time and gait variability seem to depend more on physical and automatic processes rather than higher cognitive functions among physically active older people. The relationships between cognitive functions and postural control likely vary depending on the specific tasks and the characteristics of different populations.

Effects of gait retraining in knee joint position sense

BACKGROUND

Joint position sense (JPS) is crucial for maintaining posture, protecting joints, and carrying out daily activities such as walking. Studies show that exercises to strengthen muscles and improve proprioception can positively impact JPS during passive and less complex activities. Evidence suggests that motor training can effectively enhance sensory function, including JPS, due to the extensive connections between the motor cortex and somatosensory areas. Gait retraining using real-time feedback has improved outcomes among patients with musculoskeletal disorders. The effect of gait retraining on JPS has not been investigated. This study assessed the effects of gait retraining to reduce knee extension in joint position sense in individuals with knee hyperextension walking patterns.

METHODS

Ten women with asymptomatic knee hyperextension (KH) >5° during overground walking participated in this study. Sagittal-plane kinematics were assessed using a three-dimensional (3D) motion analysis system. The JPS was assessed using the Knee Position Active Reproduction Test. The knee with the highest hyperextension was the focus of the gait retraining intervention, which consisted of six 1-h sessions using verbal instructions and visual kinematic feedback. Comparisons of peak knee extension during walking and knee JPS overall error (RMSE) were made using a paired t-test.

RESULTS

Gait retraining intervention significantly reduced knee extension angle during walking (83.8 % change; p < 0.001; Cohen's d = -1.6) and improved knee JPS (62 % change; p = 0.023; Cohen's d = 0.8) post-training. In addition, the improvements in joint kinematics (36.7 % change; p = 0.005; Cohen's d = -1.2) and JPS (52.6 % change; p = 0.015; Cohen's d = 0.9) were observed in the untrained knee.

SIGNIFICANCE

Gait retraining can improve joint position sense. This study addresses a gap in our understanding of how gait retraining can influence JPS. Our results corroborate that gait retraining is an evolving and promising strategy for improving gait outcomes, particularly in individuals with KH walking patterns.

Evaluating Joint Angle Data for Clinical Assessment Using Multidimensional Inverse Kinematics with Average Segment Morphometry

Movement analysis is a critical tool in understanding and addressing various disabilities associated with movement deficits. By analyzing movement patterns, healthcare professionals can identify the root causes of these alterations, which is essential for preventing, diagnosing, and rehabilitating a broad spectrum of medical conditions, disabilities, and injuries. With the advent of affordable motion capture technologies, quantitative data on patient movement is more accessible to clinicians, enhancing the quality of care. Nonetheless, it is crucial that these technologies undergo rigorous validation to ensure their accuracy in collecting and monitoring patient movements, particularly for remote healthcare services where direct patient observation is not possible. In this study, motion capture technology was used to track upper extremity movements during a reaching task presented in virtual reality. Kinematic data was then calculated for each participant using a scaled dynamic inertial model. The goal was to evaluate the accuracy of joint angle calculations using inverse kinematics from motion capture relative to the typical movement redundancy. Shoulder, elbow, radioulnar, and wrist joint angles were calculated with models scaled using either direct measurements of each individual's arm segment lengths or those lengths were calculated from individual height using published average proportions. The errors in joint angle trajectories calculated using the two methods of model scaling were compared to the inter-trial variability of those trajectories. The variance of this error was primarily within the normal range of variability between repetitions of the same movements. This suggests that arm joint angles can be inferred with good enough accuracy from motion capture data and individual height to be useful for the clinical assessment of motor deficits.

Exploring the control of whole-body angular momentum in young and elderly based on the virtual pivot point concept

While walking, ground reaction forces point from the centre of pressure to the neighbourhood of a focal point, namely the virtual pivot point (VPP), that adjusts angular momentum around the centre of mass (CoM). This study explores how age and speed affect the VPP quality and position during walking. Analysing an experimental dataset reveals high quality of the VPP in the sagittal plane for both young and elderly groups, regardless of speed. However, in the frontal plane, the VPP quality decreases with increasing speed, with elderly participants exhibiting significantly lower quality. Although not a direct measure of balance, VPP quality reflects changes in whole-body angular momentum owing to ageing and speed. Additionally, a template model is used to reproduce the VPP quality and position trends observed in the experiment. Simulation results highlight the sensitivity of VPP quality to leg force feedback and show that changing VPP height has minimal effect on gait speed. Furthermore, energy redistribution occurs through increased hip extension and leg damping, associated with a greater horizontal VPP distance from the CoM, observed in elderly walking. This study shows promise for analysing gait based on VPP, potentially aiding clinical interventions and supporting locomotion in the elderly.

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.

Assessing fall risk in osteoporosis patients: a comparative study of age-matched fallers and nonfallers

This study aimed to investigate sway parameters and physical activity level of the age/gender-matched older adults with osteoporosis faller and nonfaller patients. By examining these factors, our objective was to understand how these faller and nonfaller groups with osteoporosis differed particularly in terms of balance capabilities and their impact on physical activity levels. We recruited 24 patients with osteoporosis: 12 who reported a fall within a year before recruitment (fallers) and 12 without falls (nonfallers). Given the close association between biochemical markers of musculoskeletal health such as serum calcium, parathyroid hormone (PTH), Vitamin D, and renal function, we compared these markers in both groups. As a result, elderly individuals with osteoporosis and with a history of falls within the preceding year indicated significantly higher sway velocity (P = 0.012*), sway area (P < 0.001*), and sway path length (P = 0.012*). Furthermore, fallers had significantly lower calcium (P = 0.02*) and Parathyroid hormone (PTH) (P = 0.02*), as well as higher Alkaline Phosphatase (ALP) (P = 0.02*) as compared to nonfallers despite similar vitamin D and creatinine levels. In conclusion, diminished biochemical factors in the osteoporosis faller group could possibly cause postural instability resulting in lower physical activity levels in the osteoporosis fall group and increasing the risk of falls.

Comparison of effects of Otago exercise program vs gaze stability exercise on balance and fear of fall in older adults: A randomized trial

BACKGROUND

Fall occurrences and the associated risk of injury are debilitating and major health concerns in the older population. Several interventions have been investigated and implemented to address the needs of balance impairments and to reduce the increased risk of falls. This study aimed to compare the effectiveness of the Otago exercise program (OEP) and gaze stability exercises (GSE) on balance and the risk of falls in older adults residing at an old age home facility.

METHODS

Thirty elderly participants were equally and randomly divided into 2 groups: Group OEP received the OEP, and group GSE received GSE for 8 weeks (thrice a week). In addition, both groups also performed core muscle-strengthening exercises. The outcome measures were the Berg balance scale (BBS) and the Fall efficacy scale-International (FES-I).

RESULTS

The interventions resulted in significant improvements (P < .001) in both outcome measures in both groups. The mean pretest BBS scores of groups OEP and GSE increased from 40.4 and 39.2 to the mean post-test scores of 48 and 45.2, respectively. Similarly, the mean pretest FES-I scores of groups OEP and GSE also improved from 39.47 and 40.4 to the mean post-test scores of 32.73 and 36.07. The between-group comparison showed greater improvement (P < .05) in OEP group in both variables.

CONCLUSIONS

OEP and GSE were found to be beneficial rehabilitation programs in improving balance and fear of falls in healthy older adults. However, the OEP was found to be a more effective intervention and may allow better balance and fall prevention improvements.

TRIAL REGISTRATION

The study has been registered in clinicaltrials.gov (ID: NCT05781776; on 23/03/2023).

Cross-cultural validation of the Berg balance scale to assess balance among Hungarian institutionalised older adults

PURPOSE

To translate the Berg Balance Scale (BBS) to Hungarian and to evaluate the psychometric characteristics of the Hungarian version (HU-BBS).

METHODS

In total, 150 institutionalised older adults were recruited for the study. Eighty-one participants completed the retesting. Internal consistency, intra- and inter-rater reliability, and 95% limits of agreement of the HU-BBS were examined. Construct validity was assessed through convergent, discriminant, and known-group validity.

RESULTS

The overall Cronbach's alpha was 0.943. The intra- and inter-rater reliability was excellent (intraclass correlation coefficient > 0.92). The Bland-Altman analysis revealed a mean inter-rater difference of 0.284 [-2.193-2.744] and a mean intra-rater difference of 0.259 [-2.657-3.162]. Regarding convergent validity, the HU-BBS was correlated with the functional status (r = 0.833), Timed Up and Go test (r= -0.824), and age (r= -0.606). The HU-BBS scores of women were similar to those of men (p = 0.104), showing discriminant validity. Additionally, the HU-BBS scores were lower among faller than among non-faller participants (p ˂ 0.0001), establishing known-group validity.

CONCLUSIONS

Translation and cultural adaptation of the original scale was successful. The HU-BBS proved to be a reliable, valid tool confirming that it can be used in future clinical and scientific work on Hungarian older adults.Implications for rehabilitationInstitutionalised older adults are vulnerable and at a high risk of developing further decline in postural control, contributing to an increase in limited functional mobility and risk for falls.The Berg Balance Scale is a widely used tool originally developed to measure postural control in older adults.The Hungarian version of the Berg Balance Scale tested on institutionalised older adults shows excellent test-retest reliability, good internal consistency, and acceptable convergent construct validity.The Hungarian version of the Berg Balance Scale is a valid and reliable tool for measuring postural control among Hungarian-speaking institutionalised older adults both in clinical practice and scientific studies.

Common synaptic inputs and persistent inward currents of vastus lateralis motor units are reduced in older male adults

Although muscle atrophy may partially account for age-related strength decline, it is further influenced by alterations of neural input to muscle. Persistent inward currents (PIC) and the level of common synaptic inputs to motoneurons influence neuromuscular function. However, these have not yet been described in the aged human quadriceps. High-density surface electromyography (HDsEMG) signals were collected from the vastus lateralis of 15 young (mean ± SD, 23 ± 5 y) and 15 older (67 ± 9 y) men during submaximal sustained and 20-s ramped contractions. HDsEMG signals were decomposed to identify individual motor unit discharges, from which PIC amplitude and intramuscular coherence were estimated. Older participants produced significantly lower knee extensor torque (p < 0.001) and poorer force tracking ability (p < 0.001) than young. Older participants also had lower PIC amplitude (p = 0.001) and coherence estimates in the alpha frequency band (p < 0.001) during ramp contractions when compared to young. Persistent inward currents and common synaptic inputs are lower in the vastus lateralis of older males when compared to young. These data highlight altered neural input to the clinically and functionally important quadriceps, further underpinning age-related loss of function which may occur independently of the loss of muscle mass.

Tai Chi counteracts age-related somatosensation and postural control declines among older adults

Objective

To investigate the effect of a 16-week Tai Chi practice on strength, tactile sensation, kinesthesia, and static postural control among older adults of different age groups.

Methods

This is a quasi-experimental study. Thirteen participants aged 60-69 years (60-69yr), 11 aged 70-79 years (70-79yr), and 13 aged 80-89 years (80-89yr) completed 16 weeks of 24-form Tai Chi practice. Their ankle and hip peak torque, tactile sensation, ankle and knee kinesthesia, and the root mean square of the center of pressure (Cop-RMS) were measured before (week 0) and after (week 17) practice.

Results

80-89yr showed less ankle plantar/dorsiflexion and hip abduction peak torques (p = 0.003, p < 0.001, p = 0.001), and a greater ankle plantar/dorsiflexion kinesthesia (p < 0.001, p = 0.002) than 60-69yr and 70-79yr. Greater ankle plantar/dorsiflexion and hip abduction torques (p = 0.011, p < 0.001, p = 0.045), improved arch and heel tactile sensation (p = 0.040, p = 0.009), and lower knee flexion/extension kinesthesia (p < 0.001, p = 0.044) were observed at week 17. The significant group*practice interaction for the fifth metatarsal head tactile sensation (p = 0.027), ankle plantar/dorsiflexion kinesthesia (p < 0.001, p = 0.004), and the CoP-RMS in the mediolateral direction (p = 0.047) only in 80-89yr revealed greater improvement at week 17.

Conclusion

Tai Chi practice increased strength, tactile sensation, kinesthesia, and static postural control among older adults. Tai Chi practice improved tactile, kinesthesia sensations, and static postural control among older adults over 80, who presented with worse strength and kinesthesia than their younger counterparts. Tai Chi practice offers a safe exercise option for those aged over 80 to encourage improvements in sensorimotor control.

Safety, tolerability and blinding efficiency of non-invasive deep transcranial temporal interference stimulation: first experience from more than 250 sessions

Objective. Selective neuromodulation of deep brain regions has for a long time only been possible through invasive approaches, because of the steep depth-focality trade-off of conventional non-invasive brain stimulation (NIBS) techniques.Approach. An approach that has recently emerged for deep NIBS in humans is transcranial Temporal Interference Stimulation (tTIS). However, a crucial aspect for its potential wide use is to ensure that it is tolerable, compatible with efficient blinding and safe.Main results. Here, we show the favorable tolerability and safety profiles and the robust blinding efficiency of deep tTIS targeting the striatum or hippocampus by leveraging a large dataset (119 participants, 257 sessions), including young and older adults and patients with traumatic brain injury. tTIS-evoked sensations were generally rated as 'mild', were equivalent in active and placebo tTIS conditions and did not enable participants to discern stimulation type.Significance. Overall, tTIS emerges as a promising tool for deep NIBS for robust double-blind, placebo-controlled designs.

IMU-Based Kinematics Estimation Accuracy Affects Gait Retraining Using Vibrotactile Cues

Wearable sensing using inertial measurement units (IMUs) is enabling portable and customized gait retraining for knee osteoarthritis. However, the vibrotactile feedback that users receive directly depends on the accuracy of IMU-based kinematics. This study investigated how kinematic errors impact an individual's ability to learn a therapeutic gait using vibrotactile cues. Sensor accuracy was computed by comparing the IMU-based foot progression angle to marker-based motion capture, which was used as ground truth. Thirty subjects were randomized into three groups to learn a toe-in gait: one group received vibrotactile feedback during gait retraining in the laboratory, another received feedback outdoors, and the control group received only verbal instruction and proceeded directly to the evaluation condition. All subjects were evaluated on their ability to maintain the learned gait in a new outdoor environment. We found that subjects with high tracking errors exhibited more incorrect responses to vibrotactile cues and slower learning rates than subjects with low tracking errors. Subjects with low tracking errors outperformed the control group in the evaluation condition, whereas those with higher error did not. Errors were correlated with foot size and angle magnitude, which may indicate a non-random bias. The accuracy of IMU-based kinematics has a cascading effect on feedback; ignoring this effect could lead researchers or clinicians to erroneously classify a patient as a non-responder if they did not improve after retraining. To use patient and clinician time effectively, future implementation of portable gait retraining will require assessment across a diverse range of patients.

Improvement of postural control in the frail older adults through foot care: A pre- and post-intervention study

Frailty in older adults often leads to foot issues, increasing fall-related fracture risk. Mechanoreceptors, the pressure receptors in the foot sole, are pivotal for postural control. Foot problems can impair mechanoreceptor function, compromising balance. This study aimed to examine the effect of foot care on postural control in frail older adults. Forty-eight participants underwent a five-month monthly foot care intervention. Measurements were taken before and after this intervention. Participants stood for 45 s in a static, open-eyed position on a stabilometer. Center-of-pressure (CoP) analysis included total trajectory length, integrated triangle area, rectangular area, and range of motion in anterior-posterior and medio-lateral directions. Results indicated that foot care significantly increased toe ground contact area by 1.3 times and improved anterior-posterior motion control during static standing. Enhanced postural control resulted from improved skin condition due to foot care that intensified mechanoreceptor signal input and improved postural control output. These findings underscore the potential for reducing fracture risks in older adults through proactive foot care. The study highlights the vital role of foot care in enhancing postural control, with broader implications for aging population well-being and safety.

Early sleep after action observation plus motor imagery improves gait and balance abilities in older adults

Action observation plus motor imagery (AOMI) is a rehabilitative approach to improve gait and balance performance. However, limited benefits have been reported in older adults. Early sleep after motor practice represents a strategy to enhance the consolidation of trained skills. Here, we investigated the effects of AOMI followed by early sleep on gait and balance performance in older adults. Forty-five older adults (mean age: 70.4 ± 5.2 years) were randomized into three groups performing a 3-week training. Specifically, AOMI-sleep and AOMI-control groups underwent observation and motor imagery of gait and balance tasks between 8:00 and 10:00 p.m. or between 8:00 and 10:00 a.m. respectively, whereas Control group observed landscape video-clips. Participants were assessed for gait performance, static and dynamic balance and fear of falling before and after training and at 1-month follow-up. The results revealed that early sleep after AOMI training sessions improved gait and balance abilities in older adults compared to AOMI-control and Control groups. Furthermore, these benefits were retained at 1-month after the training end. These findings suggested that early sleep after AOMI may represent a safe and easy-applicable intervention to minimize the functional decay in older adults.

Visual Field Dependence Persists in Age-Related Central Visual Field Loss

Purpose

To examine whether the age-related increase in visual field dependence persists in older adults with central field loss (CFL).

Methods

Twenty individuals with CFL were grouped into participants with age-related binocular CFL (CFL, n = 9), age-related monocular CFL/relative scotomata (mCFL, n = 8), and CFL occurring at a young age (yCFL, n = 3). Seventeen controls were age-matched to the older CFL groups (OA) and three to the yCFL group (yOA). Participants judged the tilt direction of a rod presented at various orientations under conditions with and without a visual reference. Visual field dependence was determined as the difference in judgment bias between trials with and without the visual reference. Visual field dependence was examined between groups and relative to visual acuity and contrast sensitivity.

Results

All older groups performed similarly without the visual reference. The CFL group showed greater visual field dependence than the OA group (Mann-Whitney U test; U = 39, P = 0.045). However, there was no group difference when considering all three older groups (Kruskal-Wallis ANOVA; H(2, N = 34) = 4.31, P = 0.116). Poorer contrast sensitivity correlated with greater visual field dependence (P = 0.017; ρ = -0.43).

Conclusions

Visual field dependence persists in older adults with CFL and seems exacerbated in those with dense binocular scotomata. This could be attributed to the sensitivity of the spared peripheral retina to orientation and motion cues. The relationship with contrast sensitivity further suggests that a decline in visual function is associated with an increase in visual field dependence beyond the effects of normal aging. These observations can guide tailored care and rehabilitation in older adults with CFL.

Speech-Identification During Standing as a Multitasking Challenge for Young, Middle-Aged and Older Adults

While listening, we commonly participate in simultaneous activities. For instance, at receptions people often stand while engaging in conversation. It is known that listening and postural control are associated with each other. Previous studies focused on the interplay of listening and postural control when the speech identification task had rather high cognitive control demands. This study aimed to determine whether listening and postural control interact when the speech identification task requires minimal cognitive control, i.e., when words are presented without background noise, or a large memory load. This study included 22 young adults, 27 middle-aged adults, and 21 older adults. Participants performed a speech identification task (auditory single task), a postural control task (posture single task) and combined postural control and speech identification tasks (dual task) to assess the effects of multitasking. The difficulty levels of the listening and postural control tasks were manipulated by altering the level of the words (25 or 30 dB SPL) and the mobility of the platform (stable or moving). The sound level was increased for adults with a hearing impairment. In the dual-task, listening performance decreased, especially for middle-aged and older adults, while postural control improved. These results suggest that even when cognitive control demands for listening are minimal, interaction with postural control occurs. Correlational analysis revealed that hearing loss was a better predictor than age of speech identification and postural control.

Reduced tactile sensitivity is associated with mild cognitive impairment

BACKGROUND

Sensory impairment has been related to age-associated cognitive decline. While these associations were investigated primarily in the auditory and visual domain, other senses such as touch have rarely been studied. Thus, it remains open whether these results are specific for particular sensory domains, or rather point to a fundamental role of sensory deficits in cognitive decline.

METHODS

Data from 31 participants with mild cognitive impairment (MCI), 46 participants with frailty, and 23 non-clinical control participants (NCCs) were included. We assessed sensory function using visual acuity and contrast sensitivity, hearing threshold, and mechanical detection threshold. Cognitive function in participants with MCI was assessed using associative memory performance. Group differences on sensory thresholds were tested using analyses of covariance with age, sex, and years of education as covariates. Associations between measures within participants with MCI were evaluated using Spearman correlations.

FINDINGS

We found a significant difference in mechanical detection threshold between the groups (p < 0.001, η2 = 0.18). Participants with MCI showed significantly reduced tactile sensitivity compared to participants with frailty and NCCs. In participants with MCI, lower associative memory performance was significantly related to reduced tactile sensitivity (rs = 0.39, p = 0.031) and auditory acuity (rs = 0.41, p = 0.022).

INTERPRETATION

Our results indicate that reduced tactile sensitivity is related to cognitive decline. Prospective studies should investigate the age-related alterations of multimodal sensory processes and their contribution to dementia-related processes.

FUNDING

Deutsche Forschungsgemeinschaft (FL 156/41-1) and a grant of the Hector-Stiftung II, Weinheim, Germany.

Age-related impairments and influence of visual feedback when learning to stand with unexpected sensorimotor delays

Background

While standing upright, the brain must accurately accommodate for delays between sensory feedback and self-generated motor commands. Natural aging may limit adaptation to sensorimotor delays due to age-related decline in sensory acuity, neuromuscular capacity and cognitive function. This study examined balance learning in young and older adults as they stood with robot-induced sensorimotor delays.

Methods

A cohort of community dwelling young (mean = 23.6 years, N = 20) and older adults (mean = 70.1 years, N = 20) participated in this balance learning study. Participants stood on a robotic balance simulator which was used to artificially impose a 250 ms delay into their control of standing. Young and older adults practiced to balance with the imposed delay either with or without visual feedback (i.e., eyes open or closed), resulting in four training groups. We assessed their balance behavior and performance (i.e., variability in postural sway and ability to maintain upright posture) before, during and after training. We further evaluated whether training benefits gained in one visual condition transferred to the untrained condition.

Results

All participants, regardless of age or visual training condition, improved their balance performance through training to stand with the imposed delay. Compared to young adults, however, older adults had larger postural oscillations at all stages of the experiments, exhibited less relative learning to balance with the delay and had slower rates of balance improvement. Visual feedback was not required to learn to stand with the imposed delay, but it had a modest effect on the amount of time participants could remain upright. For all groups, balance improvements gained from training in one visual condition transferred to the untrained visual condition.

Conclusion

Our study reveals that while advanced age partially impairs balance learning, the older nervous system maintains the ability to recalibrate motor control to stand with initially destabilizing sensorimotor delays under differing visual feedback conditions.

Effects of Type II Diabetes on Proprioception during a Reach to Pinch Task

Older adults with type II diabetes (T2D) are at risk of developing nerve disorders that result in functional impairment. Most work in proprioceptive dysfunction in older adults with T2D has focused on functional deficits of the lower limb. The purpose of this study was to examine proprioceptive effects of T2D on the upper limb in older adults. Kinematic performance of a reach-to-pinch action toward a virtual target was assessed in a T2D group (60+ years old with T2D) and a healthy age- and sex-matched control group. Tactile and vibratory thresholds did not differ between T2D and controls. Task accuracy via mean pinch location was significantly worse for persons with T2D (pwT2D) with differences in wrist extension/flexion (ex/fl), wrist abduction/adduction (ab/ad), 1st carpometacarpal (CMC) ab/ad, 2nd metacarpophalangeal (MCP2) ex/fl, MCP2 ab/ad, and digit 1 and hand transport trajectories. Group differences persisted with consideration of body mass index; sex differences in task accuracy emerged. Findings indicate that proprioception of the upper extremity is altered in pwT2D such that they exhibit a unique aperture position and aiming strategy during a reach-to-pinch action. These findings characterize functional sensorimotor impairment of the upper limb in pwT2D with respect to workspaces without visual or tactile feedback.

Age differences in spatial memory are mitigated during naturalistic navigation

Spatial navigation deficits in older adults are well documented. These findings are often based on experimental paradigms that require using a joystick or keyboard to navigate a virtual desktop environment. In the present study, we investigated whether age differences in spatial memory are attenuated when tested in a more naturalistic and ambulatory virtual environment. In Experiment 1, cognitively normal young and older adults navigated a virtual variant of the Morris Water Maze task in each of two virtual reality (VR) conditions: a desktop VR condition which required using a mouse and keyboard to navigate and an immersive and ambulatory VR condition which permitted unrestricted locomotion. In Experiment 2, we examined whether age- and VR-related differences in spatial performance were affected by the inclusion of additional spatial cues in an independent sample of young and older adults. In both experiments, older adults navigated to target locations less precisely than did younger individuals in the desktop condition, replicating numerous prior studies. These age differences were significantly attenuated, however, when tested in the fully immersive and ambulatory environment. These findings underscore the importance of developing naturalistic and ecologically valid measures of spatial memory and navigation, especially when performing cross-sectional studies of cognitive aging.

The influence of diabetes and age-related degeneration on body balance control during static standing: a study based on plantar center-of-pressure trajectories and principal component analysis

BACKGROUND

Aging and diabetes can impair the balance function of the elderly and diabetic patients and increase their fall risk. This study aimed to assess the shaking amplitude of the center-of-pressure (CoP) during static standing, to analyze the effects of aging and diabetes on the balance control.

MATERIALS AND METHODS

This cross-sectional observational study, compared the balance performance of 20 healthy younger adults (27.65 ± 5.60 years), 16 healthy older adults (58.88 ± 3.54 years) and 15 diabetic patients (58.33 ± 5.33 years) in four static standing conditions on a force plate: horizontal, anteroposterior (AP), left and right slope planes (5° angles on AP, left and right directions, respectively). The trajectory coordinates of the CoP over time were recorded and analyzed by principal components analysis to obtain the 95% confidence ellipse and its parameters: angle, major and minor axes lengths, and area. The balance indicators were compared among the three groups using one-way analysis of variance (ANOVA), Brown-Forsythe test or Kruskal-Wallis H test, depending on the normality and homogeneity of variance assumptions.

RESULTS

The diabetic group had a significantly larger confidence ellipse area than the healthy younger adults on the horizontal plane (P = 0.032) and than the healthy older adults on the horizontal (P = 0.036), AP slope (P = 0.023), and right ML slope (P = 0.037) planes. There were no significant differences in the major axis length of the confidence ellipse among the three groups. The diabetic group had a significantly longer minor axis length than the healthy younger adults on the AP slope (P = 0.039), left ML slope (P = 0.045) and right ML slope (P = 0.016) planes and than the healthy older adults on the AP slope (P = 0.007), left ML slope (P = 0.035) and right ML slope (P = 0.012) planes.

CONCLUSIONS

The balance control of diabetic patients is decreased compared with healthy younger and older people, and the body swing amplitude increases mainly in the direction of minor axis of confidence ellipse during static standing, while the swing amplitude in the direction of the major axis has no significant change. Evaluating the balance function of diabetic patients can help clinicians identify people with fall risk early and intervene early, thereby reducing the occurrence of fall events in this population.

"PNP slows down" - linearly-reduced whole body joint velocities and altered gait patterns in polyneuropathy

Introduction

Gait disturbances are a common consequence of polyneuropathy (PNP) and a major factor in patients' reduced quality of life. Less is known about the underlying mechanisms of PNP-related altered motor behavior and its distribution across the body. We aimed to capture whole body movements in PNP during a clinically relevant mobility test, i.e., the Timed Up and Go (TUG). We hypothesize that joint velocity profiles across the entire body would enable a deeper understanding of PNP-related movement alterations. This may yield insights into motor control mechanisms responsible for altered gait in PNP.

Methods

20 PNP patients (61 ± 14 years) and a matched healthy control group (CG, 60 ± 15 years) performed TUG at (i) preferred and (ii) fast movement speed, and (iii) while counting backward (dual-task). We recorded TUG duration (s) and extracted gait-related parameters [step time (s), step length (cm), and width (cm)] during the walking sequences of TUG and calculated center of mass (COM) velocity [represents gait speed (cm/s)] and joint velocities (cm/s) (ankles, knees, hips, shoulders, elbows, wrists) with respect to body coordinates during walking; we then derived mean joint velocities and ratios between groups.

Results

Across all TUG conditions, PNP patients moved significantly slower (TUG time, gait speed) with prolonged step time and shorter steps compared to CG. Velocity profiles depend significantly on group designation, TUG condition, and joint. Correlation analysis revealed that joint velocities and gait speed are closely interrelated in individual subjects, with a 0.87 mean velocity ratio between groups.

Discussion

We confirmed a PNP-related slowed gait pattern. Interestingly, joint velocities in the rest of the body measured in body coordinates were in a linear relationship to each other and to COM velocity in space coordinates, despite PNP. Across the whole body, PNP patients reduce, on average, their joint velocities with a factor of 0.87 compared to CG and thus maintain movement patterns in terms of velocity distributions across joints similarly to healthy individuals. This down-scaling of mean absolute joint velocities may be the main source for the altered motor behavior of PNP patients during gait and is due to the poorer quality of their somatosensory information.

Clinical Trial Registration

https://drks.de/search/de, identifier DRKS00016999.

Postural stability in strabismus and amblyopia

BACKGROUND

Postural control is a complex skill based on the collaboration of dynamic sensory mechanisms, namely the visual, vestibular, and somatosensory systems.

METHODS

A literature survey regarding postural stability in strabismus and amblyopia was conducted using databases in order to collect data for a narrative review of published reports and available literature.

RESULTS

The results of the literature survey were analyzed to provide an overview of the current knowledge of postural stability in strabismus and amblyopia. The results revealed that although postural control depends on the fundamental integration of three essential components (the visual, vestibular, and somatosensory systems), the role of vision is critical in postural stability. Once normal binocular vision is undesirably disrupted in childhood by some reason, especially in strabismus and/or amblyopia, balance is also affected. Abnormal balance affects coordination in gross and fine motor controls in school-age children and results in weakened academic performance and delayed social progress. It also impacts a child's general health, self-esteem, and safety.

CONCLUSIONS

Binocular vision is imperative for the maturation and preservation of balance control in children, as balance performance is reduced in strabismus and/or amblyopia.

Aging deteriorates the ability to discriminate the weight of an object during an action observation task

The ability to predict the weight of objects is important for skilled and dexterous manipulation during activities of daily living. The observation of other people moving objects might represent an important source of information on object features and help to plan the correct motor interaction with it. In aging, an impaired ability to evaluate the object weight might have negative drawbacks in term of the safety of the person. The aim of this study was to investigate the role of aging in the ability to discriminate the object weight during action observation. Twenty older adults (Old) and twenty young subjects (Young) performed a two-interval forced-choice task consisting in the observation of a couple of videos showing an actor moving a box of different weights. The observer had to evaluate which video showed the heavier box. Handgrip strength was acquired from all subjects. Sensitivity analysis was performed and psychometric curves were built on participants' responses. The results showed a diminished sensitivity in the object weight discrimination in Old than in Young group. The analysis of the psychometric curves revealed that this impairment pertained both the light and heavy boxes and the minimum difference to discriminate different weights was greater in Old than in Young. At last, the sensitivity and the discrimination ability significantly correlated with individuals' handgrip strength. These findings allow us to deeply characterize the impairments older adults have in discriminating the weight of an object moved by another individual.

Vibration Thresholds Using Conventional Audiometry are Clinically Useful Indicators of Postural Instability in Older Adults

BACKGROUND

 Falls are a major health concern with potentially dramatic consequences for people over 65 years of age. One crucial determinant in the risk of falls in older adults is postural control, a complex process that requires the contribution of different sensory modalities, namely visual, vestibular, auditory, and somatosensory. While there are well-established methods to screen for age-related vision, hearing, tactile, and vestibular impairments, there are very few widely available methods to screen for somatosensory function, but studies indicate that ankle audiometry (vibration thresholds) using a common B-71 bone vibrator can serve that purpose. To date, unfortunately, this technique has received little attention as a tool to measure postural instability in older adults.

PURPOSE

 The objective of the present study was to examine postural control in older adults with and without degradation of the somatosensory functions, as determined with ankle audiometry.

RESEARCH DESIGN

 This was standard group comparison.

STUDY SAMPLE

 In total, 36 healthy elderly aged between 65 and 80 years old were divided into two groups (low vibration threshold [n = 18] and high vibration threshold [n = 18]).

DATA COLLECTION AND ANALYSIS

 Standard audiometry, video head impulse test, vibration thresholds (big toe, ankle, and tibia), and static postural control task using a force platform were performed.

RESULTS

 Greater postural instability in participants with higher (worse) vibration thresholds as compared with participants with lower (better) vibration thresholds was observed even though both groups were comparable on hearing threshold and vestibular function.

CONCLUSION

 The results indicate that performing a simple vibration threshold evaluation, using a clinically available B-71 with a cut-off value of 42 dB hearing loss, could be an effective, fast, and easy-to-use procedure for detecting people at risk of falls.

Somatosensory Information in Skilled Motor Performance: A Narrative Review

Historically, research aimed at improving motor performance has largely focused on the neural processes involved in motor execution due to their role in muscle activation. However, accompanying somatosensory and proprioceptive sensory information is also vitally involved in performing motor skills. Here we review research from interdisciplinary fields to provide a description for how somatosensation informs the successful performance of motor skills as well as emphasize the need for careful selection of study methods to isolate the neural processes involved in somatosensory perception. We also discuss upcoming strategies of intervention that have been used to improve performance via somatosensory targets. We believe that a greater appreciation for somatosensation's role in motor learning and control will enable researchers and practitioners to develop and apply methods for the enhancement of human performance that will benefit clinical, healthy, and elite populations alike.

Comparison of static postural sway characteristics between pregnant and non-pregnant women

The present study aimed to compare the postural sway between pregnant and non-pregnant women during eight different sensory conditions including those in which vision, proprioception, and base of support are compromised. Forty primigravidae at the 32nd week of pregnancy and forty non-pregnant women who were matched for age and anthropometric measurements participated in this cross-sectional comparison study. Static posturography equipment was used to record the anteroposterior sway velocity, mediolateral sway velocity, and velocity moment during normal stance and when vision, proprioception, and base of support were compromised. Pregnant women (mean age: 25.4) demonstrated a larger median velocity moment and mean anteroposterior sway velocity compared to non-pregnant women (mean age:24.4) across all tested sensory conditions (p < 0.05). Although mediolateral sway velocity did not show any statistically significant difference, the ANCOVA results suggested that there was a statistically significant difference in mediolateral sway velocity in Eyes open feet apart condition on the firm surface [F (1,77, p = 0.030, η_p² = 0.121] and Eyes closed feet apart condition on the firm surface [F (1,77, p = 0.015, η_p² = 0.15] between pregnant and non-pregnant women. There was a larger velocity moment and anteroposterior postural sway velocity in pregnant women in their third trimester compared to non-pregnant women when exposed to different sensory conditions. Title: Comparison of static postural sway characteristics between pregnant and non-pregnant women.

Newly compiled Tai Chi (Bafa Wubu) promotes lower extremity exercise: a preliminary cross sectional study

BACKGROUND

Tai Chi (Bafa Wubu) is a new type of simplified Tai Chi widely practiced by Tai Chi enthusiasts that has developed and perfected simplified Tai Chi movement and enriched Tai Chi practice methods. When practicing, Tai Chi athletes and enthusiasts can choose the Bafa Wubu movements to practice according to their physical conditions. The purpose of this article is to discuss the mechanism by which Bafa Wubu promotes lower extremity exercise from the perspective of exercise biomechanics.

OBJECTIVES

This article aims to explore the scientific training methods and technical characteristics of Bafa Wubu, and its contribution to comprehensive exercise of the lower extremities, by analyzing the biomechanical characteristics of the lower extremities of participants who practice Bafa Wubu at different levels and by comparing their ground reaction force, lower limb joints, and muscles during Bafa Wubu.

METHODS

A total of 16 male participants were recruited and divided into an amateur group (N = 8) and a professional group (N = 8). The data were collected by a BTS 3D infrared-based motion capture system, and Kistler 3D force plate. The lower extremity joint forces and muscle strength were calculated by anybody simulation software with inverse dynamics.

RESULTS

During elbowing and leaning sideways with steps sideways (ELS), the ground reaction force of the professional group was significantly higher than that of the amateur group in the sagittal, vertical, and frontal axes (P < 0.01). While stepping forward, backward, and sideways, the professional group's joints loading at the hip, knee, and ankle was always higher in the vertical direction (P < 0.01). Furthermore, during warding off with steps forward (WOF), laying with steps forward (LF), and rolling back with steps backward (RBB), hip joint loading increased in the med-lat direction. During actions with steps backward and sideways, the professional group's ankle flexion/extension torque and hip abduction/rotation torque were significantly larger than those of the amateur group (P < 0.01). Different actions in Bafa Wubu activate muscles to different degrees, whereas the iliacus is mainly responsible for stabilizing postures when practitioners perform standing knee lifting motions.

CONCLUSIONS

Professional groups who have been practicing Tai Chi (Bafa Wubu) for a long time have higher ground reaction force, and the force on the three joints of the lower extremities is different for various movements, which has positive significance for exercising the joints of the lower extremities. In addition, various motions activate muscles of different types at different levels. For amateurs to practice different movements to stimulate the muscles, targeted areas of practice promote the lower extremity muscles' synergistic force. In summary, the muscles and joints of the lower extremity can obtain comprehensive and balanced exercise through Bafa Wubu.

Effects of Therapeutic Intervention on Spatiotemporal Gait Parameters in Adults With Neurologic Disorder: Systematic Review and Meta-analysis

OBJECTIVE

This systematic review and meta-analysis aimed to review and quantify the changes in gait parameters after therapeutic intervention in adults with neurologic disorders.

DATA SOURCES

A keyword search was performed in 4 databases: PubMed, CINAHL, Scopus, and Web of Science (01/2000-12/2021). We performed the search algorithm including all possible combinations of keywords. Full-text articles were examined further using forward/backward search methods.

STUDY SELECTION

Studies were thoroughly screened using the following inclusion criteria: Study design: randomized controlled trial; adults ≥55 years old with a neurologic disorder; therapeutic intervention; spatiotemporal gait characteristics; and language: English.

DATA EXTRACTION

A standardized data extraction form was used to collect the following methodological outcome variables from each of the included studies: author, year, population, age, sample size, and spatiotemporal gait parameters such as cadence, step length, step width, or double limb support. A meta-analysis was performed among trials presenting with similar characteristics, including study population and outcome measure. If heterogeneity was >50%, a random plot analysis was used; otherwise, a fixed plot analysis was done.

DATA SYNTHESIS

We included 25 out of 34 studies in our meta-analysis that examined gait in adults with neurologic disorders. All analyses used effect sizes and standard error and a P<.05(denoted by *) threshold was considered statistically significant. Overall, we found that sensory (SS) and electrical stimulation (ES) had the most significant effect on step length (SS: z=5.44*, ES: z=2.42*) and gait speed (SS: z=6.19*, ES: z=7.38*) in adults with Parkinson disease (PD). Although balance or physical activity interventions were not found to be effective in modifying step length in adults with PD, they showed a significant effect on gait speed. Further, physical activity had the most significant effect on cadence in adults with PD (z=2.84*) relative to sensory stimulation effect on cadence (z=2.59*). For stroke, conventional physical therapy had the most significant effect on step length (z=3.12*) and cadence (z=3.57*).

CONCLUSION

Sensory stimulation such as auditory and somatosensory stimulation while walking had the most significant effect on step length in adults with PD. We also found that conventional physical therapy did improve spatial gait parameters relative to other physical activity interventions in adults with PD and stroke.

A Novel Neurorehabilitation Approach for Neural Plasticity Overstimulation and Reorganization in Patients with Neurological Disorders

Neurological disorders are those that are associated with impairments in the nervous system. These impairments affect the patient’s activities of daily living. Recently, many advanced modalities have been used in the rehabilitation field to treat various neurological impairments. However, many of these modalities are available only in clinics, and some are expensive. Most patients with neurological disorders have difficulty reaching clinics. This review was designed to establish a new neurorehabilitation approach based on the scientific way to improve patients’ functional recovery following neurological disorders in clinics or at home. The human brain is a network, an intricate, integrated system that coordinates operations among billions of units. In fact, grey matter contains most of the neuronal cell bodies. It includes the brain and the spinal cord areas involved in muscle control, sensory perception, memory, emotions, decision-making, and self-control. Consequently, patients’ functional ability results from complex interactions among various brain and spinal cord areas and neuromuscular systems. While white matter fibers connect numerous brain areas, stimulating or improving non-motor symptoms, such as motivation, cognitive, and sensory symptoms besides motor symptoms may enhance functional recovery in patients with neurological disorders. The basic principles of the current treatment approach are established based on brain connectivity. Using motor, sensory, motivation, and cognitive (MSMC) interventions during rehabilitation may promote neural plasticity and maximize functional recovery in patients with neurological disorders. Experimental studies are strongly needed to verify our theories and hypothesis.

Altered cutaneous reflexes to non-noxious stimuli in the triceps surae of people with chronic incomplete spinal cord injury

Following spinal cord injury (SCI) task-dependent modulation of spinal reflexes are often impaired. To gain insight into the state of the spinal interneuronal pathways following injury, we studied the amplitude modulation of triceps surae cutaneous reflexes to non-noxious stimuli during standing and early-to-mid stance phase of walking in participants with and without chronic incomplete SCI. Reflex eliciting nerve stimulation was delivered to the superficial peroneal, sural, and distal tibial nerves about the ankle. Reflexes were analyzed in the short (SLR, 50-80 ms post stimulation onset) and the medium (MLR, 80-120 ms) latency response windows. Further, the relation between cutaneous and H-reflexes was also examined during standing. In participants without injuries the soleus SLR was modulated task-dependently with nerve specificity, and the soleus and medial gastrocnemius MLRs were modulated task-dependently. In contrast, participants with SCI, no task-dependent or nerve-specific modulation of triceps cutaneous reflexes was observed. The triceps surae cutaneous and H-reflexes were not correlated in either group (r = 0.01-0.37). The presence of cutaneous reflexes but the absence of significant amplitude modulation may suggest impaired function of spinal interneuronal pathways in this population. The lack of correlation between the cutaneous and H-reflexes may suggest that interneurons that are involved in H-reflex modulation and cutaneous reflex modulation do not receive common input, or the impact of the common input is outweighed by other input. Present findings highlight the importance of examining multiple spinal reflexes to better understanding spinal interneuronal pathways that affect motor control in people after SCI.

Balance effects of tactile stimulation at the foot

Balance relies on several types of sensory information, including somatosensory senses such as touch and position sense (proprioception). As these senses decline in older adults, there is a question of whether shoes limit somatosensory feedback from the floor. Textured insoles are designed to stimulate the soles of the feet to enhance tactile feedback. Textured insoles have shown balance benefits in some populations, but it is unclear if such tactile stimulation improves a person's balance even in cushioned athletic shoes, which dampen proprioceptive signals. Here we ask whether tactile vs. proprioceptive cues contribute differently to balance control in the healthy somatosensory system. We assessed balance in 20 healthy young adults under four footwear conditions: cushioned shoes with regular insoles, cushioned shoes with textured insoles, barefoot, and minimalist shoes. Each condition was evaluated using the Y-Balance Test (YBT) and the Balance Error Scoring System (BESS), validated tests of dynamic and static balance, respectively. YBT is a dynamic reaching test performed on one leg. The BESS includes various stance conditions with eyes closed. The results showed that footwear influenced dynamic balance only, with textured insoles leading to significantly better performance than barefoot and minimalist shoes did in the YBT. These results suggest that at least for dynamic balance, balance benefits of tactile stimulation from the textured insoles offset any dampening of proprioception caused by the athletic shoes' cushioning. Future research on how these conditions compare in older adults may lead to improved footwear recommendations to reduce fall risk and injuries for that population.

Brain Macro-Structural Alterations in Aging Rats: A Longitudinal Lifetime Approach

Aging is accompanied by macro-structural alterations in the brain that may relate to age-associated cognitive decline. Animal studies could allow us to study this relationship, but so far it remains unclear whether their structural aging patterns correspond to those in humans. Therefore, by applying magnetic resonance imaging (MRI) and deformation-based morphometry (DBM), we longitudinally screened the brains of male RccHan:WIST rats for structural changes across their average lifespan. By combining dedicated region of interest (ROI) and voxel-wise approaches, we observed an increase in their global brain volume that was superimposed by divergent local morphologic alterations, with the largest aging effects in early and middle life. We detected a modality-dependent vulnerability to shrinkage across the visual, auditory, and somato-sensory cortical areas, whereas the piriform cortex showed partial resistance. Furthermore, shrinkage emerged in the amygdala, subiculum, and flocculus as well as in frontal, parietal, and motor cortical areas. Strikingly, we noticed the preservation of ectorhinal, entorhinal, retrosplenial, and cingulate cortical regions, which all represent higher-order brain areas and extraordinarily grew with increasing age. We think that the findings of this study will further advance aging research and may contribute to the establishment of interventional approaches to preserve cognitive health in advanced age.

Relationships between cervical sagittal posture, muscle endurance, joint position sense, range of motion and level of smartphone addiction

BACKGROUND

Frequent smartphone use in a pathological way forces the user to adopt a compromised posture. This gradually results in changes to both the postural and musculoskeletal systems. This study's objectives were evaluation of head posture, muscle endurance, neck range of motion (ROM) and joint position sense in two separate smartphone user groups, one 'Addicted', the other 'Non-Addicted'.

METHODS

A sample of convenience (n = 60) was recruited from medical students (age 24.57 ± 4.38, 53.3% male) with a history of smartphones use > 2 h/day for 1-year. Based on the cut-off values of the smartphone addiction scale-short version (SAS-SV), participants were entered into each group (cut-off for male ≥ 31, female ≥ 33). Neck muscle endurance time, joint position error and cervical ROM, along with forward head posture parameters of craniovertebral angle (CVA), shoulder angle (SA), sagittal head angle (SHA) and forward head distance (FHD)) were evaluated. A Mann-Whitney test and Spearman correlation coefficient were used to determine the difference between groups and the correlations between variables.

RESULTS

The difference between 'Addicted' and 'Non-Addicted' groups was confirmed by the values for SAS-SV scores (25.23 ± 5.5 versus 43.9 ± 6.61) (p < 0.001). There were statistically significant differences between groups for the CVA and FHD parameters (p < 0.001). Further, the neck extensor muscle endurance (97 ± 3.79 versus 74.86 ± 2.23 s), was significantly different between groups (p = 0.010) but not after Bonferroni correction. There was no notable difference in the neck flexor muscle endurance, joint position error, SA, and SHA parameters between groups (p > 0.05).

CONCLUSIONS

There is a positive correlation between smartphone addiction and both decreased extensor muscle endurance and changes in neck postural alignment.

Relationship between proprioception and balance control among Chinese senior older adults

Background: Balance impairment is the most common risk factor for falls among older adults, with three potential factors (tactile sensation, proprioception, and muscle strength) being responsible for their balance control. However, controversies remain on whether or not balance control is related to the three contributors among older adults. Therefore, clarifying the above questions helps explain the mechanisms of increased falls among senior older adults. This study compares the balance control and the three factors and investigates their relationships among older adults of different ages. Methods: 166 participants ultimately passed the qualification assessment and were categorized into younger (YG, 60-69 years, n = 56), middle (MG, 70-79 years, n = 57), or older (OG, ≥80 years, n = 53) aged groups. Berg Balance Scale (BBS) performance, tactile sensation, proprioception, and muscle strength were tested. One-way ANOVA and partial correlation were performed to explore the differences between groups in BBS and its three potential contributors, along with the correlations between them within each age group. Results: Significant differences among the three groups were detected in BBS scores (p < 0.001), tactile sensation at the great toe (p = 0.015) and heel (p = 0.025), proprioception of knee flexion (p < 0.001) and extension (p < 0.001), and ankle plantarflexion (p < 0.001) and dorsiflexion (p < 0.001), and muscle strength of ankle plantarflexion (p < 0.001) and dorsiflexion (p < 0.001), and hip abduction (p < 0.001). Proprioception of knee flexion (r = -0.351, p = 0.009) and extension (r = -0.276, p = 0.041), and ankle plantarflexion (r = -0.283, p = 0.036), and muscle strength of ankle plantarflexion (r = 0.326, p = 0.015) and hip abduction (r = 0.415, p = 0.002) were correlated with BBS among the YG. Proprioception of ankle plantarflexion (r = -0.291, p = 0.030) and muscle strength of ankle plantarflexion (r = 0.448, p = 0.001) and dorsiflexion (r = 0.356, p = 0.007) were correlated with BBS among the MG. Muscle strength of ankle plantarflexion (r = 0.276, p = 0.039) and hip abduction (r = 0.324, p = 0.015) were correlated with BBS among the OG. Conclusion: YG and MG had better balance control, tactile sensation, proprioception, and muscle strength compared to OG. Proprioception correlated with balance control in YG and MG, but not in the OG. The worsen proprioception among the OG could be the key for increased falls. Exercise should be recommended to improve proprioception among senior older adults.