Attentional demands for postural control: the effects of aging and sensory reintegration

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

BACKGROUND

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

RESEARCH QUESTION

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

METHODS

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

RESULTS

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

SIGNIFICANCE

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

Sleep quality and its association with anxiety, stress, sleep-related beliefs and attitudes and postural control in young adults: a cross-sectional study

OBJECTIVES

Adequate sleep is essential for young adults, as this age group primarily consists of students, job seekers, and working people constantly managing a hectic lifestyle. Poor quality of sleep, which is essential for physical and mental well-being in the short and long term, can result in impaired overall health. However, there exists a gap in the literature regarding the factors affecting sleep among young adults. Hence, the objective of this study was to find the prevalence of sleep-related parameters (sleep health, hygiene, and sleep-related beliefs and attitudes) and potential risk factors for sleep quality and to investigate the association between sleep and postural control in young adults.

METHODS

This prospective, cross-sectional, analytical study included 181 young adults, 113 (62.43 %) females, and 68 (37.57 %) males, with a mean age of 23.82 ± 2.88 years. Sleep quality, health, beliefs, hygiene, stress, anxiety, and depression were assessed using questionnaires. Postural control was assessed using center of pressure (COP) indices.

RESULTS

The overall prevalence of poor sleep quality was 79.01 % among young adults. Multiple linear regression showed that predictors explained 44 % of sleep quality variance (adjusted R square=0.44, f (12,168) = 20.91, p<0.05). Poor sleep-related beliefs and attitudes (95 % CI [0.037, 0.679], p=0.029), higher perceived stress (95 % CI [0.005, 0.219], p=0.039), higher anxiety severity (95 % CI [0.108, 0.526], p=0.003), and poor COP stability index A/P (95 % CI [4.986, 11.248], p=0.00) were found to be significant predictors of poor sleep quality.

CONCLUSIONS

High anxiety and stress, and poor dysfunctional beliefs and attitudes about sleep are predictors of poor sleep quality in young adults. These factors may significantly affect sleep quality and the experience of restful sleep among young adults. Also, poor sleep quality is associated with reduced postural control (decreased stability in the A/P direction). These findings are crucial for improving young adults' overall health and well-being, as poor sleep is highly prevalent among this age group.

The relationship between postural control and cognitive functioning following Zumba dancing in middle-aged women: A randomized clinical trial

This study aimed to investigate the effect of 12-week Zumba dancing on postural control and cognitive parameters and the correlations between these parameters in middle-aged women. Thirty-eight women, aged between 50 and 60 years, were randomly allocated to a Zumba group (ZG) or control group. Postural control and cognitive functions [working memory (WM) and reaction time (RT)] were assessed before and after 12 weeks of a Zumba dancing program using a stabilometric force platform, Corsi Block-Tapping Task and Simple RT tests, respectively. The results indicate that ZG showed significantly (p<.01) better balance performances when standing on a stable surface in both visual conditions [firm surface with eyes opened (EO) (20,9%) and eyes closed (EC) (12.3%)]. However, when standing on an unstable surface in both visual conditions (foam surface with EO/EC), the ZG showed no significant improvement in postural control. It seems that the benefits of Zumba on postural control depend on the sensory condition. Besides, 12-week Zumba dancing was not sufficient to significantly enhance cognitive performances (RT/WM) performances. These cognitive performances were related to postural control in challenging conditions and can be considered an effective tool for monitoring postural performances following an intervention program. Clinicians should, therefore, focus on interventions that boost cognitive functions in middle-aged women to achieve optimal postural control, mainly in challenging conditions, in order to prevent the risk and fear of falls as well as the incidence of falling.

Effect of 12-Week-Zumba Training on Postural Balance, Lower Limb Strength, Mood and Quality of Life in Postmenopausal Women

We aimed to investigate 12-week-Zumba training effects on physical and psychological parameters, and quality of life (QoL) in postmenopausal women. Forty-two postmenopausal women were randomly allocated to a control group or a Zumba group (ZG). Postural balance, lower limb strength, mood level, and QoL were assessed before and after the 12-week-Zumba training. The ZG showed significantly better balance performances under all conditions such as on firm and foam surfaces with opened and closed eyes as well as improvements in limb strength, mood and QoL compared to their baselines. Thereby, 12-week-Zumba training was effective in improving postural balance, limb strength, mood and, QoL in postmenopausal women.

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

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

The effect of different types of cognitive tasks on postural sway fluctuations in older and younger adults: A nonlinear study

BACKGROUND

There are numerous types of cognitive tasks classified as mental tracking (MT), working memory (WM), reaction time (RT), discrimination and decision-making and verbal fluency (VF). However, limited studies have investigated the effects of cognitive task type on postural control in older adults.

PURPOSE

s: The aim of this study was to investigate the effect of aging and several types of cognitive tasks on postural control in terms of nonlinear analysis.

METHOD

Postural control was investigated under 6 conditions (single task and dual-task with RT; easy and difficult VF; easy and difficult WM; easy and difficult MT. Outcome measurements were the max Lyapunov, entropy, and correlation dimension at anteroposterior (AP) and mediolateral (ML) directions.

RESULTS

The results revealed that within the older group, the AP & ML max Lyapunov at dual-task with difficult WM and MT was significantly higher than all other conditions. In addition, the older group had lower AP entropy at dual-task with easy VF, difficult WM, and easy as well as difficult MT.

CONCLUSION

The results can be useful to understand the postural control mechanisms and to detect the alterations following aging and applying different types of cognitive tasks. In addition, the investigated parameters can be a basis for identifying postural control deficiencies.

The Effects of Listening to Music on Postural Balance in Middle-Aged Women

Listening to music has been found to influence postural balance in both healthy participants and certain patients, whereas no study investigates such effects among healthy middle-aged women. Thus, this study aimed to investigate the effect of music on postural balance in middle-aged women. Twenty-six healthy women aged between 50 and 55 years participated in this study. A stabilometric platform was used to assess their postural balance by recording the mean center of pressure velocity (VmCOP) in the eyes-opened (OE) and -closed (EC) conditions on both firm and foam surfaces. Our results showed that listening to an excerpt of Mozart's Jupiter significantly decreased the VmCOP values in two sensory conditions (firm surface/EO: (p < 0.01; 95% CI: 0.27 to 2.22); foam surface/EC: (p < 0.001; 95% CI: 0.48 to 2.44)), but not in the other two conditions (firm surface/EC and foam surface/EO). We concluded that listening to Mozart's symphony improved postural performance in middle-aged women, even in challenged postural conditions. These enhancements could offer great potential for everyday functioning.

Association of impaired cognitive function with balance confidence, static balance, dynamic balance, functional mobility, and risk of falls in older adults with depression

Objectives

Increased depression severity has been linked to cognitive impairment (CI). Importantly, CI is a known risk factor for impaired balance and falls. Therefore, this study aims to explore the relationship between CI and neuromuscular functions and secondarily it aims to find out if CI is a potential predictor for neuromuscular functions deficits in depressed elderly.

Methods

Eighty-four depressed elderly participated in the study. Assessment for CI symptoms were done using Mini Mental Status Examination (MMSE) in subjects having confirmed depression. Neuromuscular functions such as balance confidence, static and dynamic balance, functional mobility, and fall risk were subjectively assessed using Activities-specific Balance Confidence (ABC) Scale, Berg Balance Scale (BBS), Timed Up and Go (TUG) Test, and Performance Oriented Mobility Assessment (POMA), respectively.

Results

Pearson's analysis revealed that there was moderate positive linear-correlation between MMSE and BBS (R = 0.382, p = <0.001) and between MMSE and ABC (R = 0.229, p = 0.036*). Further, regression analysis (R 2) revealed that MMSE significantly predicted the neuromuscular functions using BBS [F(1, 82) = 14.013, p < 0.001, with an R 2 of 0.146] and ABC [F(1, 82) = 4.545, p= 0.036*, with an R 2 of 0.053].

Conclusion

Results of this study points to an impaired CI as a possible factor in development of neuromuscular function impairment in depressed elderly.

The Influence of Listening to Preferred versus Non-Preferred Music on Static and Dynamic Balance in Middle-Aged Women

Although many women perform postural tasks while listening to music, no study has investigated whether preferred music has different effects than non-preferred music. Thus, this study aimed to explore the effects of listening to preferred versus non-preferred music on postural balance among middle-aged women. Twenty-four women aged between 50 and 55 years were recruited for this study. To assess their static balance, a stabilometric platform was used, recording the mean center of pressure velocity (CoPVm), whereas the timed up and go test (TUGT) was used to assess their dynamic balance. The results showed that listening to their preferred music significantly decreased their CoPVm values (in the firm-surface/eyes-open (EO) condition: (p < 0.05; 95% CI [-0.01, 2.17])). In contrast, when the women were listening to non-preferred music, their CoPVm values significantly (p < 0.05) increased compared to the no-music condition in all the postural conditions except for the firm-surface/EO condition. In conclusion, listening to music has unique effects on postural performance, and these effects depend on the genre of music. Listening to preferred music improved both static and dynamic balance in middle-aged women, whereas listening to non-preferred music negatively affected these performances, even in challenged postural conditions.

Effects of 12 weeks of caffeine supplementation and Zumba training on postural balance and cognitive performances in middle-aged women

The researchers aimed to examine the effect of 12-week supplementing (100 mg/day) caffeine with Zumba training on postural and cognitive performances in middle-aged women. Fifty-six middle-aged women who participated in this study, were randomized into; a caffeine-Zumba (CZG), Zumba (ZG) and control groups. In two-testing sessions, postural balance was evaluated using a stabilometric platform, and for cognitive performances, Simple Reaction Time and Corsi Block-Tapping Task tests were used. We found that ZG and CZG showed a significant improvement in postural balance on the firm surface condition (p < .05) in the post- compared to pretest session. Whereas, ZG showed no significant improvement in postural performance on the foam surface condition. Only CZG revealed significant enhancements (p < .05) in cognitive and postural, in the foam surface condition, performances. In conclusion, supplementing caffeine with 12-week Zumba training was effective in improving both cognitive and postural balance, even in challenging conditions, performances in middle-aged women.

The impact of anthropometric measures on plantar pressure distribution in male handball players and non-athletes: A cross-sectional study

BACKGROUND

Increasing body anthropometry brings substantial spinal stress, which influences the spinal curvatures; this in turn may affect the foot plantar pressure distribution.

OBJECTIVES

This study investigated the impact of body anthropometry on static plantar pressure distribution and their relationship among handball players and non-athletes subjects.

METHODS

Thirty handball players aged from 21 to 26 years, and thirty age-matched non-athletes subjects aged from 21 to 28 years participated in this study. The spinal lordosis and kyphosis angles, trunk length, pelvic tilting, and pelvic rotation were evaluated using Formetric 4-dimensions and the Pedoscan device was used to assess the plantar pressure distribution.

RESULTS

The handball players were significantly taller, heavier, and have a long trunk length than non-athletes group (p < 0.05), and a significantly increased thoracic kyphosis, forefeet pressure distribution compared to non-athletes group (p < 0.05). The handball players had a significantly increased forefeet pressure distribution compared to the rearfeet pressure distribution (p < 0.05), a high positive correlation between body height, and both trunk length and kyphosis angle (r = 0.932, 0.665 respectively), and the body height showed a high positive correlation with the forefeet pressure distribution (r = 0.665). There was a high positive correlation between the handball players' thoracic kyphosis and forefeet pressure distribution (r = 0.751).

CONCLUSION

Increasing the handball players' body height was related to increased thoracic kyphosis and forefeet pressure distribution compared to non-athletes subjects. Additionally, the kyphotic posture of handball players is associated with increasing the total forefeet pressure distribution compared to the total rearfeet pressure distribution.

Effect of age on postural performance and control strategies during changes in visual input and dual-tasking stances

Background

With age, people begin to experience deterioration in standing balance, especially when sensory input is suddenly removed or added. Here, we sought to explore the effects of age on postural performance and postural control strategies.

Methods

The convenience sample consisted of 15 young, 10 middle-aged, and 14 elderly healthy adults. They were instructed to stand with their feet together in four randomly administered conditions involving visual input removal/addition and single-/dual-tasking. Dual-tasking involved continuous subtraction by 3s.

Results

Postural sway displacement in the two older groups seemed larger than that in the younger group; however, neither the main effect of group (F_{2, 36} = 1.152, p = .327) nor the group × time interaction effect (F_{4, 27} = 0.229, p = .922) was significant. Greater stiffness of the lower leg muscles was observed in the vision-addition condition than in the vision-removal condition in only the elderly group (t₁₃ = -2.755, p = .016). The dual-tasking condition resulted in smaller sway displacement (F_{1, 36} = 7.690, p = .009) and greater muscle stiffness (F_{1, 36} = 5.495, p = .025). In the vision-removal condition, the increase in muscle stiffness due to dual-tasking was significantly larger in the middle-aged (t₉ = -3.736, p = .005) and elderly groups (t₁₃ = -2.512, p = .026).

Conclusions

In healthy older individuals, age-related changes were observed in control strategies used to maintain standing balance upon changes in visual input. The dual-task paradigm induced the use of an ankle-stiffening strategy in middle-aged and elderly adults.

Cognitive-motor interference during standing stance across different postural and cognitive tasks in individuals with Down syndrome

BACKGROUND

Individuals with Down syndrome (DS) presented both cognitive and motor impairments that could influence each other. Therefore, exploring cognitive-motor interference during standing stance is relevant in this population.

AIMS

This study explored the dual task (DT) effects on postural balance during diverse cognitive tasks and sensory manipulations in individuals with DS, compared to those with typical development (TD).

METHODS AND PROCEDURES

Fifteen adolescents with DS (age = 14.26 ± 1.27 years; height = 1.50 ± 0.02; weight = 46.46 ± 4.03 kg; BMI =20.54 ± 1.51 kg/m²) and thirteen with TD (age = 14.07 ± 1.11 years; height = 1.50 ± 0.05; weight = 44.92 ± 4.15 kg; BMI =19.77 ± 0.94 kg/m²) participated in this study. Postural and cognitive performances for the selective span task (SST) and the verbal fluency (VF) were recorded during single task (ST) and DT conditions. Postural conditions were: firm eyes open (firm-EO), firm eyes closed (firm-EC) and foam-EO. Motor and cognitive DT costs (DTC) were calculated and analyzed across these different cognitive and postural conditions.

OUTCOMES AND RESULTS

In the DS group, postural performance was significantly (p < 0.001) altered during all DT conditions, compared to the ST situation. Moreover, the motor DTC was significantly (p < 0.001) higher while performing the VF task than the SST. However, in the control group, postural performance was significantly (p < 0.001) impaired only while performing the VF test in the DT-Firm EO condition. For both groups, cognitive performances were significantly (p < 0.05) altered in all DT conditions compared to the ST one.

CONCLUSION

Adolescents with DS are more prone to DT effects on postural balance than those with TD.

Interaction of Hearing and Balance

There is increasingly assumed that, in addition to visual, vestibular and somatosensory afferents, hearing also plays a role in the regulation of balance. It seems that, especially in old age, progressive hearing loss is associated with a decrease in postural control. Several studies investigated this relationship in normal-hearing people, in patients with conventional hearing aids and with implantable hearing systems, as well as in patients with vestibular disorders. Despite the inhomogeneous study situation and lack of evidence, hearing seems to interact with the balance regulation system with potentially stabilizing effect. Furthermore, insights into audiovestibular interaction mechanisms could be achieved, which could possibly be integrated into therapeutic concepts of patients with vestibular disorders. However, further prospective controlled studies are necessary to bring this issue to an evidence-based level.

USING THE SENSORY INTEGRATION TECHNIQUE FOR PEOPLE WITH AUTISM SPECTRUM DISORDERS DURING TRAINING AT THE CLIMBING SECTION

OBJECTIVE

Aim: To analyze the practical application of the sensory integration technique for individuals with autism spectrum disorder at a climbing section, and to investigate the impact of physical activity on improving their proprioceptive and vestibular systems.

PATIENTS AND METHODS

Materials and Methods: The method of included participant observation at the climbing classes with constant recording the behavior (desirable and undesirable) was used. The sensory screening (developed by J. Ayres) was applied for recording and determining the sensory systems of the people with ASD before the start of training and again after a month. The scale of Sensory Integration and Praxis Tests (SIPT) was used for assessing certain aspects of participants' sensory processing or perception according to the goals set during the climbing classes.

RESULTS

Results: The results of the research showed that the application of the sensory integration technique for individuals with ACD at a climbing section promoted the dynamics of changes in their sensory system during training considering the characteristics of their sensory system. The positive changes were observed in the way the people with ACD felt about their own bodies and their involvement in sports activities that in its turn made it possible to be active and develop their sensory system. It has been identified that while planning training for the people with ASD it is necessary to take into account sensory modulation (reading sensory signals) and apply exercises for stimulating sensory sensations that will improve the motor activity of persons with ASD, their social interaction, and safety, as well.

CONCLUSION

Conclusions: During training at the climbing section sensory information processing of the individuals with ASD have the impact on their body control, hand-eye coordination, and hand sensitivity during training. The improvement of sensory information processing in its turn enables people with ASD to master climbing.

Neurometabolic correlates of posturography in normal aging and older adults with mild cognitive impairment: Evidence from a 1H-MRS study

Proton magnetic resonance spectroscopy (¹H-MRS) holds promise for revealing and understanding neurodegenerative processes associated with cognitive and functional impairments in aging. In the present study, we examined the neurometabolic correlates of balance performance in 42 cognitively intact older adults (healthy controls - HC) and 26 older individuals that were diagnosed with mild cognitive impairment (MCI). Neurometabolite ratios of total N-acetyl aspartate (tNAA), glutamate-glutamine complex (Glx), total choline (tCho) and myo-inositol (mIns) relative to total creatine (tCr) were assessed using single voxel ¹H-MRS in four different brain regions. Regions of interest were the left hippocampus (HPC), dorsal posterior cingulate cortex (dPCC), left sensorimotor cortex (SM1), and right dorsolateral prefrontal cortex (dlPFC). Center-of-pressure velocity (Vcop) and dual task effect (DTE) were used as measures of balance performance. Results indicated no significant group differences in neurometabolite ratios and balance performance measures. However, our observations revealed that higher tCho/tCr and mIns/tCr in hippocampus and dPCC were generic predictors of worse balance performance, suggesting that neuroinflammatory processes in these regions might be a driving factor for impaired balance performance in aging. Further, we found that higher tNAA/tCr and mIns/tCr and lower Glx/tCr in left SM1 were predictors of better balance performance in MCI but not in HC. The latter observation hints at the possibility that individuals with MCI may upregulate balance control through recruitment of sensorimotor pathways.

The effect of a trunk stabilization exercise program using weight loads on balance and gait in stroke patients: A randomized controlled study

BACKGROUND: The effects of trunk stabilization exercise programs and exercises applying weight loads for stroke patients are well presented. However, there is not enough objective research to prove the effects of trunk stabilization exercise programs using weight loads for stroke patients. OBJECTIVE: In this study, a trunk stabilization exercise program using weight loads was performed to investigate its impact on the balance and gait ability of stroke patients. METHODS: Thirty patients with stroke were randomly divided into three groups. Experiment group 1 followed a trunk stabilization exercise program using weight loads, experiment group 2 followed a trunk stabilization exercise program, and the control group followed general physiotherapy. Patients’ balance ability was assessed using balance measurement equipment BT-4 (postural sway area (PSA), postural sway length (PSL), limit of stability (LOS)), Berg Balance Scale (BBS), and Time Up and Go test (TUG). Gait speed was measured to examine gait ability. RESULT: After the intervention, the PSA, PFSL in experimental groups 1 and 2 decreased but that of the control group increased. BBS, TUG, and LOS scores of experimental group 1 were significantly improved compared to experimental group 2 and the control group. Also, gait speed was significantly improved in experimental group 1 compared to experimental group 2 and the control group. CONCULSION: This study may be used as a basic material for an effective trunk stabilization exercise method for stroke patients and might be of significance as an intervention method for stroke patients requiring long-term treatment.

Less Vibrotactile Feedback Is Effective to Improve Human Balance Control during Sensory Cues Alteration

For individuals with altered sensory cues, vibrotactile feedback improves their balance control. However, should vibrotactile feedback be provided every time balance control is compromised, or only one-third of the time their balance is compromised? We hypothesized that vibrotactile feedback would improve balance control more when provided every time their balance is compromised. Healthy young adults were randomly assigned to two groups: group 33% feedback (6 males and 6 females) and group 100% feedback (6 males and 6 females). Vibrotactile feedbacks related to the body's sway angle amplitude and direction were provided, while participants stood upright on a foam surface with their eyes closed. Then, we assessed if balance control improvement lasted when the vibrotactile feedback was removed (i.e., post-vibration condition). Finally, we verified whether or not vibrotactile feedback unrelated to the body's sway angle and direction (sham condition) altered balance control. The results revealed no significant group difference in balance control improvement during vibrotactile feedback. Immediately following vibrotactile feedback, both groups reduced their balance control commands; body sway velocity and the ground reaction forces variability decreased. For both groups, unrelated vibrotactile feedback worsened balance control. These results confirmed that participants processed and implemented vibrotactile feedback to control their body sways. Less vibrotactile feedback was effective in improving balance control.

A Comprehensive Review of Pain Interference on Postural Control: From Experimental to Chronic Pain

Motor control, movement impairment, and postural control recovery targeted in rehabilitation could be affected by pain. The main objective of this comprehensive review is to provide a synthesis of the effect of experimental and chronic pain on postural control throughout the available literature. After presenting the neurophysiological pathways of pain, we demonstrated that pain, preferentially localized in the lower back or in the leg induced postural control alteration. Although proprioceptive and cortical excitability seem modified with pain, spinal modulation assessment might provide a new understanding of the pain phenomenon related to postural control. The literature highlights that the motor control of trunk muscles in patient presenting with lower back pain could be dichotomized in two populations, where the first over-activates the trunk muscles, and the second under-activates the trunk muscles; both generate an increase in tissue loading. Taking all these findings into account will help clinician to provide adapted treatment for managing both pain and postural control.

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

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

Influence of serial subtraction tasks on transient characteristics of postural control

We sought to better understand the influence of cognitive perturbations on transient aspects of postural control. Twenty healthy, younger adults had their postural control assessed during eyes open quiet stance. Participants completed three different conditions that either had no cognitive perturbation present, an easy cognitive perturbation (i.e., serial subtraction by ones), or a more difficult cognitive perturbation (i.e., serial subtraction by sevens). All trials finished with 60 s of undisturbed eyes open quiet stance, which was the focus of the balance assessment. 95% confidence ellipse area (EA) was calculated for 5-s epochs throughout the trial. The difference in EA from the first epoch after participants started (onset) or stopped (offset) the cognitive task to the last epoch of the trial (i.e., 55-60 s after perturbation) was used to characterize transient postural control behavior. Functional near-infrared spectroscopy was also used to quantify changes in prefrontal cortex activation during the counting tasks to support interpretation of the transient balance findings. There was a significant effect of condition for transient balance characteristics following a cognitive perturbation (P < 0.001), with greater transient increases in postural sway for both difficult (Cohen's d = 0.40, P < 0.001) and easier (Cohen's d = 0.29, P = 0.013) cognitive perturbations relative to no cognitive perturbation. The onset of cognitive tasks was also associated with greater transient increases in postural sway than the offset of the cognitive tasks (Cohen's d = 0.24, P = 0.019). The functional near-infrared spectroscopy data indicated that a significant decrease in deoxygenated hemoglobin was observed for left Brodmann area 46 for both the subtraction by ones (T = -3.97; Benjamini-Hochberg significance value (q) = 0.008) and subtraction by sevens (T = -3.11; q = 0.036) conditions relative to the baseline condition. The subtraction by sevens condition was also associated with a relative increase in deoxygenated hemoglobin for the right Brodmann area 9 (T = 3.36; q = 0.026) compared to the subtraction by ones condition. In conclusion, serial subtraction can elicit transient increases in postural sway, with more difficult tasks and the onset of the cognitive-motor challenge exhibiting magnified effects. Additionally, even the cessation of a cognitive task (i.e., serial subtraction) can be associated with lingering perturbing effects on balance control.

Age-related enhancement in visuomotor learning by a dual-task

Many daily activities require performance of multiple tasks integrating cognitive and motor processes. While the fact that both processes go through deterioration and changes with aging has been generally accepted, not much is known about how aging interacts with stages of motor skill acquisition under a cognitively demanding situation. To address this question, we combined a visuomotor adaptation task with a secondary cognitive task. We made two primary findings beyond the expected age-related performance deterioration. First, while young adults showed classical dual-task cost in the early motor learning phase dominated by explicit processes, older adults instead strikingly displayed enhanced performance in the later stage, dominated by implicit processes. For older adults, the secondary task may have facilitated a shift to their relatively intact implicit learning processes that reduced reliance on their already-deficient explicit processes during visuomotor adaptation. Second, we demonstrated that consistently performing the secondary task in learning and re-learning phases can operate as an internal task-context and facilitate visuomotor memory retrieval later regardless of age groups. Therefore, our study demonstrated age-related similarities and differences in integrating concurrent cognitive load with motor skill acquisition which, may in turn, contributes to the understanding of a shift in balance across multiple systems.

Haptic Information Improvement on Postural Sway is Information-Dependent But Not Influenced by Cognitive Task

Young adults reduce their sway in both light touch (LT) and anchor systems (AS), however, the cognitive involvement in these tasks is unknown. This study investigated postural control in young adults standing upright using either LT or AS, concomitantly with a cognitive task (counting). Nine adults (26 ± 7.4 years) stood in the upright tandem stance with eyes closed, with/without LT, AS (force <2 N), and a cognitive task. The mean sway amplitude of the trunk, right wrist, and shoulder ellipse area, as well as the mean force during LT and AS were obtained. The cognitive task did not influence the magnitude of trunk sway or the mean force in the LT and AS conditions. The trunk sway magnitude was reduced in the AS and even further in LT. Wrist and shoulder variability was larger in the AS than in the LT. Based on these results, we conclude that enhanced sensory cues provided by LT and AS reduce trunk sway with little or no attentional demands.

Does Time of Day influence postural control and gait? A review of the literature

BACKGROUND

Like many physiologic processes, Time of Day may influence postural control and gait. A better understanding of diurnal variations in postural control and gait may help to improve diagnoses, reduce falls, and optimize rehabilitation and training routines. This review summarizes the current literature that addresses these questions.

RESEARCH QUESTION

Does time of day affect postural control and gait?

METHODS

We searched PubMed, Google Scholar, and IEEE using a combination of keyword and MeSH terms. We included papers that studied human subjects and assessed gait or postural control as a function of time of day. We evaluated the quality of the identified papers based on nine assessment criteria and analyzed them considering the topic (postural control or gait), age, and characteristics of the conducted assessments. We then quantitatively synthesized the results across studies using a meta-analytical approach (i.e., Hedges' g model).

RESULTS

Twenty-two papers considered the relationship between time of day and postural control, and eleven considered the relationship between time of day and gait. Six studies found that postural control was best in the morning, four described postural control being best in the afternoon, four described optimal postural control in the evening, and eight reported no time of day effect. Two studies found gait best in the morning, five described gait best in the afternoon, two described optimal gait in the evening, and two reported no time of day effect. The results of the quantitative analysis suggest that both postural control and gait were best in the evening.

SIGNIFICANCE

While there is no clear consensus on whether there is a time of day effect for postural control and gait, the findings of this review provide initial evidence suggesting that a small but statistically significant effect exists in favor of the evening. Standardized testing, including repeated and continuous evaluations, may help provide more definitive information on time of day influences on postural control and gait.

Validity and reliability of video analysis to evaluate ankle proprioceptive reintegration during postural control

BACKGROUND

The ability to dynamically reintegrate proprioceptive signals after they have been perturbated is impaired in certain pathologies. Evaluation of proprioceptive reintegration is useful for clinical practice but currently requires expensive laboratory tools. We developed a simple method, accessible to clinicians.

RESEARCH QUESTION

Is two-dimensional (2D) video analysis of earlobe displacement a valid and reliable tool for the evaluation of ankle proprioceptive reintegration following muscle vibration?

METHODS

Thirty-eight healthy individuals underwent vibration of the triceps surae while standing on a force plate (FP). Anterior (sagittal plane) earlobe displacement ('overshoot') was recorded at vibration cessation using 2D video analysis and rated by 3 blind examiners. Correlation analysis was performed between earlobe and center of pressure displacement (dCoP, recorded with the FP) to determine validity. Intra and interrater reliability were determined by calculation of the intraclass correlation coefficient (ICC), change in the mean (CiM), standard error of measurement (SEM) and the minimal detectable change (MDC).

RESULTS AND SIGNIFICANCE

Strong positive correlations (r = 0.82-0.94, p < .001) were found between video and FP data. Intra- and interrater reliability were excellent (ICC from 0.99 to 1.00 and from 0.90 to 0.97 respectively). For intrarater analysis, the CiM was 0.01 cm, SEM were 0.27 cm (95% CI: 0.23-0.33) and 3.43% (95% CI: 2.92-4.20) and the MDC was 0.74 cm. For interrater reliability, the CiM ranged from - 0.81-0.55 cm, the SEM from 0.61 to 1.12 cm and the MDC from 1.69 to 3.10 cm. 2D video analysis of anterior (sagittal) earlobe displacement is therefore a valid and reliable method to assess postural recovery following muscle vibration. This simple method could be used by clinicians to evaluate the ability of the central nervous system to reintegrate proprioceptive signals from the ankle. Further studies are needed to assess its validity in individuals with proprioceptive impairment.

Cortical Activity During Postural Recovery in Response to Predictable and Unpredictable Perturbations in Healthy Young and Older Adults: A Quantitative EEG Assessment

Introduction:

To investigate the effects of predictable and unpredictable external perturbations on cortical activity in healthy young and older adults.

Methods:

Twenty healthy older and 19 healthy young adults were exposed to predictable and unpredictable external perturbations, and their cortical activity upon postural recovery was measured using a 32-channel quantitative encephalography. The absolute spectral power and coherence z-scores of cortical waves were analyzed through a 3-way mixed ANOVA.

Results:

During postural recovery from predictable perturbations, older adults exhibited higher frontoparietal beta power and higher alpha and beta coherence during the late-phase recovery than the young individuals. After unpredictable perturbations, the older group showed lower alpha power in the early phase and higher beta power in the late phase as compared to the young group. Results for the group × time and group × location interactions in the older group showed a higher alpha and beta coherence over the late phase, a higher alpha coherence in F3–P3 and F4–P4 regions, and a higher beta coherence in the F4–P4 region compared to the younger group.

Conclusion:

Our results revealed that the cortical activation after external perturbations increases with aging, particularly in frontoparietal areas. A shift from automatic (subcortical level) to attentional (cortical level) processing may reflect the contribution of attentional resources for postural recovery from an external threat in older individuals.

Proprioceptive postural control strategies differ among non-injured athletes

Postural control during complex tasks requires adequate sensory integration and somaesthetic reweighting: suboptimal postural strategies can lead to injury. We assessed the ability of healthy athletes to reweight somaesthetic signals during postural perturbations on different surfaces. Thirty-five young (16 ± 1 years), healthy, elite handball players participated in this cross-sectional study. Proprioceptive reweighting was evaluated via vibration of the triceps surae and lumbar muscles on firm and foam surfaces. Postural variables and the electromyographic activity of the gluteus medius (GM), semitendinosus (ST) and fibularis longus (FL) were recorded during the PRE (10 s), VIBRATION (20 s) and POST (20 s) periods. Ankle proprioception was predominantly used on the firm compared to foam support. However, two opposing behaviours were observed: a "rigid" strategy in which reliance on ankle proprioception increased on the foam, and a "plastic" strategy that involved a proximal shift of proprioceptive reliance (p < 0.001). The plastic strategy was associated with a more effective recovery of balance after vibration cessation (p < 0.05). ST activation was higher during POST in the rigid strategy and did not return to the PRE level (p < 0.05) whereas it did in the plastic strategy. Proprioceptive strategies for postural control are highly variable and future studies should evaluate their contribution to injury.

Vibration of the Whole Foot Soles Surface Using an Inexpensive Portable Device to Investigate Age-Related Alterations of Postural Control

Background: Standing on a foam surface is used to investigate how aging affect the ability to keep balance when somatosensory inputs from feet soles become unreliable. However, since standing on foam also affects the efficacy of postural adjustments, the respective contributions of sensory and motor components are impossible to separate. This study tested the hypothesis that these components can be untangled by comparing changes of center of pressure (CoP) parameters induced by standing on a foam pad vs. a novel vibration (VIB) platform developed by our team and targeting feet soles’ mechanoreceptors.

Methods: Bipedal postural control of young (n = 20) and healthy elders (n = 20) was assessed while standing barefoot on a force platform through 3 randomized conditions: (1) Baseline (BL); (2) VIB; and (3) Foam. CoP Amplitude and Velocity in the antero-posterior/medio-lateral (AP/ML) directions and COP Surface were compared between conditions and groups.

Findings: Both VIB and Foam increased CoP parameters compared to BL, but Foam had a significantly greater impact than VIB for both groups. Young and Old participants significantly differed for all three Conditions. However, when correcting for BL levels of postural performance, VIB-related increase of COP parameters was no longer different between groups, conversely to Foam.

Interpretation: Although both VIB and Foam highlighted age-related differences of postural control, their combined use revealed that “motor” and “sensory” components are differently affected by aging, the latter being relatively unaltered, at least in healthy/active elders. The combined used of these methods could provide relevant knowledge to better understand and manage postural impairments in the aging population.

The Effects of Exergaming on Sensory Reweighting and Mediolateral Stability of Women Aged Over 60: Usability Study

Background

Older adults tend to experience difficulties in switching quickly between various reliable sensory inputs, which ultimately may contribute to an increased risk of falls and injuries. Sideward falls are the most frequent cause of hip fractures among older adults. Recently, exergame programs have been confirmed as beneficial tools for enhancing postural control, which can reduce the risk of falls. However, studies to explore more precisely which mechanism of exergaming directly influences older women’s ability to balance are still needed.

Objective

Our aim was to evaluate, in a single-group pretest/posttest/follow-up usability study, whether Kinect exergame balance training might have a beneficial impact on the sensory reweighting in women aged over 60.

Methods

A total of 14 healthy women (mean age 69.57 [SD 4.66] years, mean body mass index 26.21 [SD 2.6] kg/m²) participated in the study. The volunteers trained with the commercially available games of Kinect for Xbox 360 console 3 times (30 minutes/session) a week over a 6-week period (total of 18 visits). Participants’ postural sway in both the anteroposterior (AP) and mediolateral (ML) directions was recorded with NeuroCom Balance Master 6.0. To assess and measure postural sensory reweighting, the Modified Clinical Test of Sensory Interaction in Balance was used, where volunteers were exposed to various changes in visual (eyes open or eyes closed) and surface conditions (firm or foam surface).

Results

In the ML direction, the Kinect exergame training caused a significant decrease in the sway path on the firm surface with the eyes open (P<.001) and eyes closed (P=.001), and on the foam surface with the eyes open (P=.001) and eyes closed (P<.001) conditions compared with baseline data. The follow-up measurements when compared with the baseline data showed a significant change in the sway path on the firm surface with the eyes open (P<.001) and eyes closed (P<.001) conditions, as well as on the foam surface with the eyes open (P=.003) and eyes closed (P<.001) conditions. Besides, on the firm surface, there were no significant differences in sway path values in the AP direction between the baseline and the posttraining measurements (eyes open: P=.49; eyes closed: P=.18). Likewise, on the foam surface, there were no significant differences in sway path values in the AP direction under both eyes open (P=.24) and eyes closed (P=.84) conditions.

Conclusions

The improved posturography measurements of the sway path in the ML direction might suggest that the Kinect exergame balance training may have effects on sensory reweighting, and thus on the balance of women aged over 60. Based on these results, Kinect exergaming may provide a safe and potentially useful tool for improving postural stability in the crucial ML direction, and thus it may help reduce the risk of falling.

Kinematic Analysis of Dance-Based Exergaming: A Cross-Sectional Study

BACKGROUND

Recent studies demonstrate improvements in both postural stability and mobility among aging populations and those with stroke who are exposed to dance-based exergaming (DBExG). However, age-related deficits and aging with cortical pathology may lead to distinct movement adaptation patterns during DBExG, which could impact therapeutic outcomes.

AIM

The aim of this study was to examine the movement kinematics (postural stability and mobility) of healthy older adults, older adults with stroke, and young adults for different paces of dance during DBExG.

METHOD

The study included 33 particpants (11 participant from each group of healthy older adults, older adults with chronic stroke, and healthy young adults) who performed the DBExG using slow- (SP), medium- (MP), and fast-paced (FP) songs with movements in the anteroposterior (AP) and mediolateral (ML) directions. Center of mass (CoM) sway area, excursion (Ex), and peaks as well as hip, knee, and ankle joint excursions were computed.

RESULTS

Results of the study revealed that CoM sway areas and Exs were greater for healthy young adults than for older adults with stroke for the SP dance (p < 0.05) and that there were significantly more AP CoM peaks for young adults than for healthy older adults and those with stroke for the FP dance (p < 0.05). Young adults also exhibited greater hip and ankle Exs than older adults with stroke (p < 0.05) for all song paces. Similarly, knee and ankle Exs were greater for healthy older adults than for older adults with stroke for all song paces (p < 0.05).

CONCLUSION

The quantitative evaluation and comparison of the movement patterns presented for the three groups could provide a foundation for both assessing and designing therapeutic DBExG protocols for these populations.

Medical aromatherapy in geriatric syndrome

Geriatric syndromes are symptoms and signs, such as falls, incontinence, delirium, pressure ulcers, dysphagia and so on, that often threaten the independence of older adults, rather than the disease itself. Although the syndromes are very common in older people, it is difficult to treat those by modern medicine due to their complexity. To mitigate the intractable geriatric symptoms, we review the efficacy of aromatherapy, especially for dysphagia, dyspnea, cognitive dysfunction and falls in geriatric syndrome. Olfactory stimulation using a volatile black pepper oil on institutional residents improved the swallowing reflex, which is a crucial risk factor of aspiration pneumonia. Brain imaging study showed that olfactory stimulation using volatile black pepper oil activated cerebral regions of the anterior cingulate and the insular cortex, which play a role in controlling appetite and swallowing. Also, aromatherapy with volatile l-menthol decreased the sense of dyspnea and improved the efficacy of exercise therapy. The fragrance of the combination of rosemary and lemon oils in the morning, and the combination of lavender and orange oils in the night-time were reported to improve cognition and behavioural and psychological symptoms of dementia, respectively. Also, the combination of lavender and lemon balm oils was reported to be effective for irritability-related agitation in older adults. Furthermore, aromatherapy with lavender fragrance could improve both static and dynamic balance, resulting in a reduction in the number of fallers and the incidence rate in older people. Thus, aromatherapy is a promising remedy for geriatric syndrome. Geriatr Gerontol Int 2021; 21: 377-385.

Sensory reweighting in frail aged adults: Are the balance deficiencies mainly compensated by visual or podal dependences?

BACKGROUND

Postural control is based on the integration of different sensory inputs. The process of scaling the relative importance of these sensory cues (visual, vestibular and proprioceptive) depends on individuals and creates sensory preferences, leading to sensory dependences when one particular source is preponderant. In this context, the literature showed a frequent visual dependence (visual inputs weighting) in aged adults. However, the somaesthetic inputs can also be prioritised in a podal-dependent profile. In the frail aged adults, none study has shown the distribution of these two dependences.

RESEARCH QUESTION

Which sensory orientation profile is preferentially adopted by frail aged males and females?

METHODS

In this cross-sectional study, we compared 33 frail aged adults to 16 non frail aged adults during a static postural control task in three conditions on a force platform: i) a standard condition, ii) a no-vision condition and iii) a foam condition. An analysis with the factor sex was also performed in each group of participants.

RESULTS

The analysis of stabilometric parameters (mean velocity and mean velocity variance) highlighted a significant difference in no-vision or foam conditions when compared to the standard condition in frail aged males and only in the foam condition when compared to the standard condition for females in the frail group. No significant difference was observed between conditions in the control group.

SIGNIFICANCE

Our study showed the predominance of both visual and podal information in frail aged adults when controlling their posture. Considering the sex factor, frail males were more dependents to their visual cues than frail females. This result should be used when designing the rehabilitation programs in this population.

Obesity impairs performing and learning a timing perception task regardless of the body position

Obesity has been associated with poorer sensorimotor performance. However, it remains unclear whether these obesity-related impairments can be mitigated by practice. In the present study, we sought to investigate the effects of practice on performing and learning a temporal estimation task, in women with and without obesity. The experimental task consisted of synchronizing the arrival of two rectangles at a target point. Limited to the pressing of a switch, the task was intended to minimize possible muscular fatigue, self-generated perturbations to balance and the need to accelerate/decelerate body segments. Participants were allowed to choose the displacement velocity of the rectangle they controlled and were informed that they would not be offered any choice over it during a test to come. To control for the effect of different body positions on sensorimotor performance and learning, the 19 women with obesity (BMI = 40.0 + 7.33, age = 44.2 + 6.6) and 20 without obesity (BMI = 22.3 + 1.95, age = 43 + 6.9) were assigned into 4 groups, according to their BMI and body position assumed during practice (standing upright with feet together or sitting). As no significant differences concerning body position were found, the data were reanalysed disregarding this factor. Results revealed that while both groups reduced errors during the Acquisition, participants with obesity showed poorer performance (Acquisition) and sensorimotor learning (Transfer). Given the experimental task and adopted procedures, our results tend to support the hypothesis that hindered perception and/or integration of sensory information is associated with obesity.

Biomechanical assessment while using production tables on mast climbing work platforms

The objective of this study was to assess the impact of using alternative mast climbing work platform (MCWP) designs on trunk motion and postural stability with masonry workers while performing bricklaying and stepping down tasks using a conventional MCWP setting (i.e. with a step deck) as well as two types of production tables (straight- and L-shaped). The trunk angles and postural sway parameters of twenty-five masonry workers were recorded for the following tasks: (1) standing on a simulated MCWP and laying bricks on an adjacent wall, and (2) stepping down onto the step deck to get into position for doing the bricklaying task. Results indicated that the use of the L-shaped production table resulted in the lowest trunk ranges of motion and significantly reduced the workers' trunk angles in all three planes when compared to both the straight-shaped production table and the conventional approach of not using a production table. Data showed that both body sway velocity and area were significantly reduced when using either one of the production tables. The use of production tables significantly reduced impact sway forces when workers stepped from the main platform to the step deck. The use of production tables on MCWPs improved workers' postures and overall stability, which could reduce the risk of injury.

Does the transcranial direct current stimulation improve dual-task postural control in young healthy adults?

Some studies have suggested that postural balance improved after a single session of transcranial direct current stimulation (tDCS), whereas others have found minimal, if any, effects on postural performance. To address the issue of replication in tDCS studies, we re-tested the anodal tDCS effects of left dorsolateral prefrontal cortex while performing a dual-task by increasing the attentional demands associated with more challenging proprioceptive conditions. Twenty-four young adults (mean age: 21.3 ± 1.2 years) were randomly divided into two groups (a "real tDCS" vs. a "sham tDCS" group) were asked to maintain a quiet stance on a force platform. Eight trials were conducted, with eyes open and eyes closed, standing on a firm and foam surface and performing a simple and dual-task (backward counting). The postural performance was assessed by various centre-of-pressure parameters before and immediately after a 20-min tDCS session. No main effect of group and no interaction considering this factor were observed, regardless of the centre-of-pressure variables (all p values > 0.1). No evidence of a more efficient postural control emerged after a tDCS session. Beyond promising research on tDCS to maximize cognitive and behavioural enhancement, the current results indicate that caution needs to be taken when drawing firm conclusions, at least in young healthy adults.

Effects of adiposity on postural control and cognition in older adults

BACKGROUND

Understanding the impacts of increased adiposity on postural control and cognitive deficits in adults is critical for health practitioners in recommending or prescribing effective weight loss regimens. Despite prior work in this area, the knowledge of increased adiposity impacts on postural control and cognitive deficits in older adults (OAs) is still limited.

RESEARCH QUESTION

The purposes of the current study were: (a) to assess the relationship between postural measures and adiposity measures by using regression model analyses and, (b) to examine the impacts of increased adiposity and age on cognitive performance.

METHODS

A total of thirty (30) individuals aged 60+ years participated in the study. Participants were classified into three groups based upon their BMI scores at the onset of the study. The normal weight (NW) (BMI: 18.5-24.9 kg/m²), the overweight (OW) (BMI: 25-29.9 kg/m²), and the obese (OB) groups (BMI: 30-40 kg/m²) each had five females and five males. Participants were required to perform two test sessions: (1) anthropometry assessment and body composition scanning; and (2) evaluation of plantar tactile function, postural control, and cognitive function.

RESULTS

Overall, our findings indicate that increased adiposity in OAs is associated with declines in both cognitive function and postural control.

SIGNIFICANCE

Our data also indicate that measures such as BMI and abdominal fat mass amounts/ratios offer the best insight to the impact of adiposity on cognitive function and postural control measures. However, further work is still needed to clarify the mechanistic links between adiposity and cognitive-postural deficits.

Interactions Between Different Age-Related Factors Affecting Balance Control in Walking

Maintaining balance during walking is a continuous sensorimotor control problem. Throughout the movement, the central nervous system has to collect sensory data about the current state of the body in space, use this information to detect possible threats to balance and adapt the movement pattern to ensure stability. Failure of this sensorimotor loop can lead to dire consequences in the form of falls, injury and death. Such failures tend to become more prevalent as people get older. While research has established a number of factors associated with higher risk of falls, we know relatively little about age-related changes of the underlying sensorimotor control loop and how such changes are related to empirically established risk factors. This paper approaches the problem of age-related fall risk from a neural control perspective. We begin by summarizing recent empirical findings about the neural control laws mapping sensory input to motor output for balance control during walking. These findings were established in young, neurotypical study populations and establish a baseline of sensorimotor control of balance. We then review correlates for deteriorating balance control in older adults, of muscle weakness, slow walking, cognitive decline, and increased visual dependency. While empirical associations between these factors and fall risk have been established reasonably well, we know relatively little about the underlying causal relationships. Establishing such causal relationships is hard, because the different factors all co-vary with age and are difficult to isolate empirically. One option to analyze the role of an individual factor for balance control is to use computational models of walking comprising all levels of the sensorimotor control loop. We introduce one such model that generates walking movement patterns from a short list of spinal reflex modules with limited supraspinal modulation for balance. We show how this model can be used to simulate empirical studies, and how comparison between the model and empirical results can indicate gaps in our current understanding of balance control. We also show how different aspects of aging can be added to this model to study their effect on balance control in isolation.

Postural sway changes during static standing with concurrent task in children with traumatic brain injury

OBJECTIVE

To investigate the effects of concurrent tasks (motor and cognitive) on postural control performance in children with traumatic brain injury (TBI) compared to typically developing (TD) control subjects.

METHODS

Sixteen children with TBI (aged 11.63+/-1.89 years) and 22 TD controls (aged 11.41+/-2.24 years) participated in this case-control study. This study was conducted between May 2016 and March 2017. Each child performed static standing under 3 different conditions: single, concurrent motor, and concurrent cognitive task. Postural control performance measure includes sway area, anterior-posterior (AP) sway velocity, medio-lateral (ML) sway velocity, AP sway distance and ML sway distance as measured using the APDM Mobility Lab (Oregon, Portland). A repeated-measure analysis of variance was used to analyse the data.

RESULTS

We found that children with TBI showed significantly more deterioration in postural control performance than TD children (p<0.05). Both concurrent tasks (motor and cognitive) significantly decreased postural control performance in both groups with more pronounced changes in children with TBI than that of the TD controls.

CONCLUSION

The results demonstrated that, performing concurrent tasks (motor and cognitive) during upright standing resulted in deterioration of postural control performance. The existence of cognitive and balance impairment in children with TBI will possibly cause concurrent tasks to be more complex and demands greater attention compared to single task.

The effects of aging on the distribution and strength of correlated neural inputs to postural muscles during unperturbed bipedal stance

The present study investigated the effects of aging on the distribution of common descending neural drives to main postural muscles acting on the ankle, knee, hip, and lower trunk. The presence, distribution, and strength of these drives were assessed using intermuscular coherence estimations at a low-frequency band (0-55 Hz). Ten healthy older adults (68.7 ± 3.5 years) with no recent history of falls and ten healthy younger adults (26.8 ± 2.7 years) performed bipedal stances with eyes either opened or closed. Electromyographic (EMG) signals of six postural muscles were recorded. Estimations of intermuscular coherence were obtained from fifteen muscle pairs and four muscle groups. In general, single-pair and pooled coherence analyzes revealed significant levels of signal synchronization within 1-10 Hz. Significant common drives to anterior, posterior, and antagonist muscle groups were observed for both cohorts of participants. However, older participants showed significantly stronger EMG-EMG synchronization in the frequency domain compared to younger participants. It seems that age-related sarcopenia, visual-vestibular-proprioceptive decline, cortical activation increase, presynaptic inhibition modulation decrease, and co-contraction increase had a major impact on strengthening the common drives to the aforementioned muscle groups. Differently from young adults, the absence of visual inputs did not reduce the magnitude of signal synchronization in older adults. These results suggest that the aging central nervous system seems to organize similar arrangements of common drives to postural antagonist muscles at different joints, and to postural muscles pushing the body either forward or backward when visual information is not available.

Agreement of Three Posturographic Force Plates in the Assessment of Postural Stability

This study was designed to assess how the results obtained for three different posturographic platforms agreed with each other in an assessment of static postural stability. The study included 111 young healthy participants. A measurement of postural stability was made for each participant, with their eyes open and then closed, on each platform in a random order. The Romberg ratio, path length, and center of pressure (COP) area were analyzed. For all measures, significant differences (p < 0.05) were observed among the three force plates. The highest Spearman's rank correlation was observed between Alfa vs. CQStab2P (0.20 to 0.38), and the lowest between Alfa vs. AccuGait (-0.19 to 0.09). Similar results were obtained for the concordance correlation coefficient (0.10 to 0.22 for Alfa vs. CQStab2P and -0.6 to 0.02 for Alfa vs. AccuGait). Bland-Altman analysis for values standardized (z-scores) against AccuGait indicated a low level of agreement between compared platforms, with the largest error between AccuGait vs. Alfa, and a slightly lower error between AccuGait vs. CQStab2P or Alfa vs. CQStab2P. The 95% limits of agreement ranged from 2.38 to 7.16 (Alfa vs. AccuGait), 2.09 to 5.69 (CQStab2P vs. AccuGait), and 1.39 to 7.44 (AccuGait vs. Alfa) in COP length with eyes open and COP length Romberg ratio, respectively. Special care is recommended when comparing values relating to COPs from different devices that are analyzed by different software. Moreover, unperturbed stance tests among young healthy adults can be questioned as a valid postural control parameter.

Effects on Postural Kinematics of Performing a Cognitive Task During Upright Standing

The execution of cognitive tasks is known to alter postural sway during standing, but the underlying mechanisms are still debated. This study investigated how performing a mental task modified balance control during standing. We required 15 healthy adult males to maintain an upright stance under conditions of simply relaxing and maintaining normal quiet standing (control condition) or while performing a secondary cognitive task (mental arithmetic). Under each condition, we measured the participants' center of pressure and used kinematic measurements for a quantitative evaluation of postural control modulation. We calculated the standard deviation of the joint angles (ankle, knee, and hip) and the estimated joint stiffness to measure joint mobility changes in postural control. To estimate the kinematic pattern of covariation among these joints, we used uncontrolled manifold analysis, an assessment of the strength of multijoint coordination. Compared to normal standing, executing the cognitive task while standing led to reduced movements of the ankle and hip joints. There were no significant differences in ankle stiffness or uncontrolled manifold ratios between the conditions. Our results suggest that when performing a secondary cognitive task during standing, neither changes in the modification of stiffness nor the strength of multijoint coordination (both of which preserve the center of mass position) explains changes in postural sway.

Comparing Balance Control Between Soccer Players and Non-Athletes During a Dynamic Lower Limb Reaching Task

Background: Balance control is an essential element of locomotion that enhances biomotor abilities and physical performance. Individuals with extensive soccer experience display superior static single leg balance control compared to athletes of other sports as well as non-athletes. However, during a match, players often encounter greater challenges to single leg balance that require rapid decision-making skills and dynamic stability. Purpose: The purpose of this study was to determine if individuals with extensive soccer training demonstrate superior single-leg balance control compared to non-athletes during a dynamic lower limb reaching task. Method: 22 varsity soccer players were matched with 21 non-athlete controls. Single-leg balance control was assessed during a Go/No-Go lower limb reaching task. Centre of pressure displacement (dCOP) was measured for both the dominant and non-dominant feet and compared between groups. Results: Soccer players displayed reduced dCOP during All Go trials compared to non-athletes, particularly in the medial-lateral plane. Additionally, soccer players displayed reduced anterior-posterior dCOP during Go/No-Go trials compared to non-athletes, particularly on their dominant foot. Conclusion: Athletes with soccer-specific training demonstrate improved executive control and use of proprioceptive information, which results in an improved ability to maintain single-support balance and corral COP during a dynamic visuomotor lower limb-reaching task. As such, balance training may be a useful addition to athlete training regimes to improve sport-specific performance. Future research would compare these results to athletes of other sports to explore balance control during a visuomotor reaching task and how it may differ based on sport training history.

People in early stages of Parkinson's disease are able to intentionally reweight the use of visual information for postural control

Background

Parkinson’s disease (PD) leads to several changes in motor control, many of them related to informational or cognitive overload. The aim of this study was to investigate the influence of knowledge and intention on the postural control performance and on the coupling between visual information and body sway in people with and without PD standing upright.

Methods

Participants were 21 people with PD (62.1 ± 7.2 years), stages 1 and 2 (Hoehn & Yahr scale), under dopaminergic medication, and 21 people in the control group (62.3 ± 7.1 years). Participants stood upright inside a moving room, performing seven trials of 60 s. In the first trial, the room remained motionless. In the others, the room oscillated at 0.2 Hz in the anterior-posterior direction: in the first block of three trials, the participants were not informed about the visual manipulation; in the second block of three trials, participants were informed about the room movement and asked to resist the visual influence. An OPTOTRAK system recorded the moving room displacement and the participants’ sway. The variables mean sway amplitude (MSA), coherence and gain were calculated.

Results

With no visual manipulation, no difference occurred between groups for MSA. Under visual manipulation conditions, people with PD presented higher MSA than control, and both groups reduced the sway magnitude in the resisting condition. Control group reduced sway magnitude by 6.1%, while PD group reduced by 11.5%. No difference was found between groups and between conditions for the coupling strength (coherence). For the coupling structure (gain), there was no group difference, but both groups showed reduced gain in the resisting condition. Control group reduced gain by 12.0%, while PD group reduced by 9.3%.

Conclusions

People with PD, under visual manipulation, were more influenced than controls, but they presented the same coupling structure between visual information and body sway as controls. People in early stages of PD are able to intentionally alter the influence of visual information.

Balance control mechanisms do not benefit from successive stimulation of different sensory systems

In humans, to reduce deviations from a perfect upright position, information from various sensory cues is combined and continuously weighted based on its reliability. Combining noisy sensory information to produce a coherent and accurate estimate of body sway is a central problem in human balance control. In this study, we first compared the ability of the sensorimotor control mechanisms to deal with altered ankle proprioception or vestibular information (i.e., the single sensory condition). Then, we evaluated whether successive stimulation of difference sensory systems (e.g., Achilles tendon vibration followed by electrical vestibular stimulation, or vice versa) produced a greater alteration of balance control (i.e., the mix sensory condition). Electrical vestibular stimulation (head turned ~90°) and Achilles tendon vibration induced backward body sways. We calculated the root mean square value of the scalar distance between the center of pressure and the center of gravity as well as the time needed to regain balance (i.e., stabilization time). Furthermore, the peak ground reaction force along the anteroposterior axis, immediately following stimulation offset, was determined to compare the balance destabilization across the different conditions. In single conditions, during vestibular or Achilles tendon vibration, no difference in balance control was observed. When sensory information returned to normal, balance control was worse following Achilles tendon vibration. Compared to that of the single sensory condition, successive stimulation of different sensory systems (i.e., mix conditions) increased stabilization time. Overall, the present results reveal that single and successive sensory stimulation challenges the sensorimotor control mechanisms differently.