Standing Balance Control Research Articles

Balance performance when responding to visual stimuli in patients with Benign Paroxysmal Positional Vertigo (BPPV).

Patients with Benign Paroxysmal Positional Vertigo (BPPV) often report a sensation of disequilibrium before treatment with the canalith repositioning maneuvers. Apart from vestibular information, visual input also contributes to balance control. How visual stimuli influence balance control in BPPV patients is unclear. To investigate the influence of visual stimuli on balance performance in BPPV patients. Three groups of participants, patients with BPPV, and healthy young and older adults, were instructed to stand under three conditions: 1) eyes open (EO); 2) while watching a static picture via a video display; and 3) while watching a rotating visual scene. Antero-posterior (AP), lateral (ML), and total sway path during standing were analyzed. In all conditions, patients with BPPV showed significantly larger AP, ML and total sway path than young, whereas older adults only showed significantly larger AP and total sway path than young adults. During the visual stimuli, all participants exhibited significantly increased AP and total sway while watching a static image and a moving scene as compared with the EO condition. Patients with BPPV have similar balance control to older adults, but poorer balance control than young adults. The reduced lack of standing balance control in the coronal plane of patients with BPPV, might affect balance strategy after external perturbations.

Proprioceptive Weighting Ratio for Balance Control in Static Standing Is Reduced in Elderly Patients With Non-Specific Low Back Pain: Erratum.

Proprioceptive Weighting Ratio for Balance Control in Static Standing Is Reduced in Elderly Patients With Non-Specific Low Back Pain: Erratum.

Effect of proprioceptive neuromuscular facilitation (PNF) on standing balance control among post stroke patients

Stroke is a neurological deficit that result of brain malfunction. Approximately 10% of post-stroke patients have coordination disorders while sitting, standing and walking. This coordination disorder is caused by several factors such as muscle tone, motoric, sensory, perception, balance, motion pattern, and associative reactions. Coordination disorder in posts-troke patients can be treated with Proprioceptive Neuromuscular Facilitation (PNF). PNF is a method of exercise therapy that aims to facilitate the neuromuscular system by stimulating proprioceptive which in the end will be achieved coordinated ability or movement. This study aim was to determine the difference between the coordination level of the PNF exercise frequency given in post-stroke patients. This research is quasi experimental with research design two group pretest-posttest time design. The sample was 20 people with 6x and 12x PNF exercise frequency. Main measure that used is a non-equilibrium coordination test pre and post PNF exercise. The result showed Mann Whitney U test was obtained p value of 0.006 (P<0.05) which there were differences between PNF exercise frequency given in post-stroke patients.

Dynamical Analysis of Standing Balance Control on Sloped Surfaces in Individuals with Lumbar Disc Herniation

The changes of balance control mechanism caused by lumbar disc herniation (LDH) has not been well understood. This study aimed to investigate the effects of LDH on the balance control during standing on sloped surfaces. Ten patients with LDH and 10 gender- and age-matched healthy subjects were instructed to stand quietly on a sloped surface at −5°, 0° or +5°, respectively. The trajectories of the center of pressure (COP) of each individual limb and the full-body were recorded. Cross recurrence quantification analysis (CRQA) was applied to assess the coordination of COP components at the anterior-posterior and medial-lateral directions. The patients with LDH presented magnified inter-limb load asymmetry and had more deterministic components in the COP coordination of the less-affected limb and the full-body than the healthy subjects. The LDH led to decreased dynamical degree of freedom and less flexibility in bidirectional controlling the center of mass simultaneously. The effects of sensorimotor deficits due to LDH could be more obviously exhibited as standing on a declined rather than an inclined surface. This study shed light on the effects of LDH on standing balance control and may facilitate to develop novel strategies for evaluation of LDH.

Analysis of center of mass acceleration and muscle activation in hemiplegic paralysis during quiet standing.

Hemiplegic paralysis after stroke may augment postural instability and decrease the balance control ability for standing. The center of mass acceleration (COMacc) is considered to be an effective indicator of postural stability for standing balance control. However, it is less studied how the COMacc could be affected by the muscle activities on lower-limbs in post-stroke hemiplegic patients. This study aimed to examine the effects of hemiplegic paralysis in post-stroke individuals on the amplitude and structural variabilities of COMacc and surface electromyography (sEMG) signals during quiet standing. Eleven post-stroke hemiplegic patients and the same number of gender- and age-matched healthy volunteers participated in the experiment. The sEMG signals of tibialis anterior (TA) and lateral gastrocnemius (LG) muscles of the both limbs, and the COMacc in the anterior-posterior direction with and without visual feedback (VF vs. NVF) were recorded simultaneously during quiet standing. The sEMG and COMacc were analyzed using root mean square (RMS) or standard deviation (SD), and a modified detrended fluctuation analysis based on empirical mode decomposition (EMD-DFA). Results showed that the SD and the scale exponent α of EMD-DFA of the COMacc from the patients were significantly higher than the values from the controls under both VF (p < 0.01) and NVF (p < 0.001) conditions. The RMSs of TA and LG on the non-paretic limbs were significantly higher than those on paretic limbs (p < 0.05) for both the patients and controls (p < 0.05). The TA of both the paretic and non-paretic limbs of the patients showed augmented α values than the TA of the controls (p < 0.05). The α of the TA and LG of non-paretic limbs, and the α of COMacc were significantly increased after removing visual feedback in patients (p < 0.05). These results suggested an increased amplitude variability but decreased structural variability of COMacc, associated with asymmetric muscle contraction between the paretic and the non-paretic limbs in hemiplegic paralysis, revealing a deficiency in integration of sensorimotor information and a loss of flexibility of postural control due to stroke.

Analisis Postur Kerja dalam Operasi Pemanenan Kayu: Pemuatan Log Secara Manual

Lifting, pushing, and pulling activities combined with excessive material load and intense repetition have been reported to trigger excessive pressure on the lumbar disk (L5/S1). Using a static biomechanical approach (3DSSPP Version 7 software), this study presents empirical evidence proving that log loading activities with manual techniques are jobs that pose a high risk of injury to workers, indicated by (1) very high lifting index value (10), (2) compressive force that exceeds the maximum permissible limit of 6500 N, (3) difficult standing balance control, and (4) high potential of localized musculoskeletal fatigue in the workers. Musculoskeletal disorders analysis (using the Standardized Nordic Questionnaire instrument) shows intense disturbances in the lower back, shoulders, upper back, and hands. Interventions to reduce injury to the workers can be carried out by substituting work techniques (using aids devices), improving work administration (improving the standard operating procedure, supervision), and wearing anti-slip work shoes.

The effects of distraction on threat-related changes in standing balance control

Research indicates that threat-induced changes in standing balance are associated with shifts in attention focus. This study investigated whether distracting attention modifies threat-induced changes in standing balance. Twenty-five healthy young adults stood without (No Threat) and with (Threat) the possibility of receiving a temporally unpredictable anteroposterior support surface translation. In both conditions, participants completed a distractor task that consisted of counting how often a pre-selected letter occurred in an auditory sequence, or no distractor task. Emotional responses to threat were quantified using electrodermal activity and self-report measures, while attention focus was quantified using self-report. Centre of pressure (COP) was measured to assess changes in standing balance. Results indicate that postural threat induced an emotional response, as well as broad shifts in attention focus and changes in standing balance. Distracting attention with a cognitive task mitigated threat-induced increases in medium-frequency COP displacements (0.5–1.8 Hz). These results provide support for a relationship between threat-related changes in balance control and attention focus.

Adaptation of emotional state and standing balance parameters following repeated exposure to height-induced postural threat

Height-induced postural threat influences standing balance control. However, it is unknown if minimizing individuals’ emotional response to threat moderates this relationship. This study repeatedly exposed individuals to height-induced postural threat to determine if reducing the emotional response to threat influences standing balance control. Sixty-eight young adults completed a series of standing trials at LOW (0.8 m above ground, away from edge) and HIGH (3.2 m above ground, at edge) postural threat conditions. Emotional state was assessed using self-report and electrodermal measures. Standing balance was assessed through analysis of centre of pressure (COP) movement and lower leg electromyographic activity. Individuals’ emotional response to threat was attenuated following repeated threat exposure. However, threat-induced changes in standing balance were largely preserved. When initially threatened, individuals leaned backward and demonstrated smaller amplitude and higher frequency of COP adjustments; these balance outcomes did not change following repeated threat exposure. Only high frequency COP oscillations (>1.8 Hz) and ankle muscle co-contraction showed any adaptation; regression analyses showed that these behavioural adaptations were accounted for by a combination of emotional and cognitive state changes. This suggests that some threat-induced standing balance changes are more closely linked with the emotional response to threat than others, and are therefore amendable to intervention.

Cortical dynamics of sensorimotor information processing associated with balance control in adolescents with and without idiopathic scoliosis

ObjectiveThis study aims at examining the cortical dynamics of sensorimotor information processing related to balance control in participants with adolescent idiopathic scoliosis (AIS) and in age-matched controls (CTL). MethodsCortical dynamics during standing balance control were assessed in 13 girls with AIS and 13 age-matched controls using electroencephalography. Time-frequency analysis were used to determine frequency power during ankle proprioception alteration (ankle tendons co-vibration interval) or reintegration of ankle proprioception (post-vibration interval) with or without vision. ResultsBalance control did not differ between groups. In the co-vibration interval, a significant suppression in alpha (8–12 Hz) and beta (13–30 Hz) band power and a significant increase in theta (4–7 Hz) band power were found respectively in the vision and non-vision condition in the AIS group compared to the CTL group. In the post-vibration interval, significant suppressions in beta (13–30 Hz) and gamma (30–50 Hz) band power were observed in the AIS group in the non-vision condition. ConclusionParticipants with AIS showed brain oscillations differences compared to CTL in the sensorimotor cortex while controlling their balance in various sensory conditions. SignificanceFuture study using evaluation of cortical dynamics could serve documenting whether rehabilitation programs have an effect on sensorimotor function in AIS.

Proprioceptive Weighting Ratio for Balance Control in Static Standing Is Reduced in Elderly Patients With Non-Specific Low Back Pain.

A cross-sectional, observational study. The aim of this study was to determine a specific proprioceptive control strategy during postural balance in elderly patients with non-specific low back pain (NSLBP) and non-LBP (NLBP). Proprioceptive decline is an important risk factor for decreased balance control in elderly patients with NSLBP. The resulting reduction in proprioception in the trunk or lower legs may contribute to a reduction in postural sway. This study aims to determine the specific proprioceptive control strategy used during postural balance in elderly patients with NSLBP and NLBP and to assess whether this strategy is related to proprioceptive decline in NSLBP. Pressure displacement centers were determined in 28 elderly patients with NSLBP and 46 elderly patients with NLBP during upright stances on a balance board without the benefit of vision. Gastrocnemius and lumbar multifidus muscle vibratory stimulations at 30, 60, and 240 Hz, respectively, were applied to evaluate the relative contributions of the different proprioceptive signals (relative proprioceptive weighting ratio, RPW) used in postural control. Compared to elderly patients with NLBP, those with NSLBP had a lower RPW at 240 Hz and significantly higher RPW at 30 Hz. A logistic regression analysis showed that RPW at 240 Hz was independently associated with NSLBP after controlling for confounding factors. Elderly patients with NSLBP decreased their reliance on ankle strategy (RPW at 240 Hz) and hip strategy (RPW at 30 Hz) proprioceptive signals during balance control. The inability to control hip and ankle strategies indicates a deficit of postural control and is hypothesized to result from proprioceptive impairment. Moreover, elderly patients with NSLBP are at higher risk for lower leg proprioceptive decrease (240 Hz) through the NSLBP exacerbation. 4.

Generation of Human-Like Movement from Symbolized Information.

An important function missing from current robotic systems is a human-like method for creating behavior from symbolized information. This function could be used to assess the extent to which robotic behavior is human-like because it distinguishes human motion from that of human-made machines created using currently available techniques. The purpose of this research is to clarify the mechanisms that generate automatic motor commands to achieve symbolized behavior. We design a controller with a learning method called tacit learning, which considers system–environment interactions, and a transfer method called mechanical resonance mode, which transfers the control signals into a mechanical resonance mode space (MRM-space). We conduct simulations and experiments that involve standing balance control against disturbances with a two-degree-of-freedom inverted pendulum and bipedal walking control with humanoid robots. In the simulations and experiments on standing balance control, the pendulum can become upright after a disturbance by adjusting a few signals in MRM-space with tacit learning. In the simulations and experiments on bipedal walking control, the robots realize a wide variety of walking by manually adjusting a few signals in MRM-space. The results show that transferring the signals to an appropriate control space is the key process for reducing the complexity of the signals from the environment and achieving diverse behavior.

The Reliance on Vestibular Information During Standing Balance Control Decreases With Severity of Vestibular Dysfunction.

The vestibular system is involved in gaze stabilization and standing balance control. However, it is unclear whether vestibular dysfunction affects both processes to a similar extent. Therefore, the objective of this study was to determine how the reliance on vestibular information during standing balance control is related to gaze stabilization deficits in patients with vestibular dysfunction. Eleven patients with vestibular dysfunction and twelve healthy subjects were included. Gaze stabilization deficits were established by spontaneous nystagmus examination, caloric test, rotational chair test, and head impulse test. Standing balance control was assessed by measuring the body sway (BS) responses to continuous support surface rotations of 0.5° and 1.0° peak-to-peak while subjects had their eyes closed. A balance control model was fitted on the measured BS responses to estimate balance control parameters, including the vestibular weight, which represents the reliance on vestibular information. Using multivariate analysis of variance, balance parameters were compared between patients with vestibular dysfunction and healthy subjects. Robust regression was used to investigate correlations between gaze stabilization and the vestibular weight. Our results showed that the vestibular weight was smaller in patients with vestibular dysfunction than in healthy subjects (F = 7.67, p = 0.011). The vestibular weight during 0.5° peak-to-peak support surface rotations decreased with increasing spontaneous nystagmus eye velocity (ρ = −0.82, p < 0.001). In addition, the vestibular weight during 0.5° and 1.0° peak-to-peak support surface rotations decreased with increasing ocular response bias during rotational chair testing (ρ = −0.72, p = 0.02 and ρ = −0.67, p = 0.04, respectively). These findings suggest that the reliance on vestibular information during standing balance control decreases with the severity of vestibular dysfunction. We conclude that particular gaze stabilization tests may be used to predict the effect of vestibular dysfunction on standing balance control.

Contributions to lateral balance control in ambulatory older adults.

In older adults, impaired control of standing balance in the lateral direction is associated with the increased risk of falling. Assessing the factors that contribute to impaired standing balance control may identify areas to address to reduce falls risk. To investigate the contributions of physiological factors to standing lateral balance control. Two hundred twenty-two participants from the Pittsburgh site of the Health, Aging and Body Composition Study had lateral balance control assessed using a clinical sensory integration balance test (standing on level and foam surface with eyes open and closed) and a lateral center of pressure tracking test using visual feedback. The center of pressure was recorded from a force platform. Multiple linear regression models examined contributors of lateral control of balance performance, including concurrently measured tests of lower extremity sensation, knee extensor strength, executive function, and clinical balance tests. Models were adjusted for age, body mass index, and sex. Larger lateral sway during the sensory integration test performed on foam was associated with longer repeated chair stands time. During the lateral center of pressure tracking task, the error in tracking increased at higher frequencies; greater error was associated with worse executive function. The relationship between sway performance and physical and cognitive function differed between women and men. Contributors to control of lateral balance were task-dependent. Lateral standing performance on an unstable surface may be more dependent upon general lower extremity strength, whereas visual tracking performance may be more dependent upon cognitive factors. Lateral balance control in ambulatory older adults is associated with deficits in strength and executive function.

Low back pain development differentially influences centre of pressure regularity following prolonged standing

Occupations requiring prolonged periods of static standing are associated with the development of low back pain (LBP). Certain individuals are susceptible to LBP development during prolonged standing (pain developers, PDs) while others are not (non-pain developers, NPDs). Linear centre of pressure (COP) measures suggest that standing balance control is negatively influenced following prolonged standing, and that PDs and NPDs may be differentially affected. The objective of this study was to determine if nonlinear standing balance control, quantified on COP, using sample entropy, is altered after 2-h of standing. Thirty two participants stood for 2-h. Separate 2-min standing trials, performed with eyes open and eyes closed, were collected before and after the 2-h standing protocol. Sample entropy, median power frequency and RMS amplitude of the COP time-series, was calculated from the 2-min standing trials for all participants. For comparison, participants were classified, post hoc, as PDs or NPDs according to visual analog scale pain scores. Sample entropy decreased after 2-h of standing for both PDs and NPDs, however, the decrease for NPDs was only 21% of the decrease observed in PDs. This study demonstrated that nonlinear control of upright standing changes after 2- hours of standing, resulting in an increase in COP regularity post 2- hours of standing for both PDs and NPDs. PDs displayed a greater change in COP regularity, which is supported by the theory that increased COP regularity occurs with pain/pathology

Both standing and postural threat decrease Achilles' tendon reflex inhibition from tendon electrical stimulation.

Golgi tendon organs (GTOs) and associated Ib reflexes contribute to standing balance, but the potential impacts of threats to standing balance on Ib reflexes are unknown. Tendon electrical stimulation to the Achilles' tendon was used to probe changes in Ib inhibition in medial gastrocnemius with postural orientation (lying prone vs. upright standing; experiment 1) and height-induced postural threat (standing at low and high surface heights; experiment 2). Ib inhibition was reduced while participants stood upright, compared to lying prone (42.2%); and further reduced when standing in the high, compared to low, threat condition (32.4%). These experiments will impact future research because they demonstrate that tendon electrical stimulation can be used to probe Ib reflexes in muscles engaged in standing balance. These results provide novel evidence that human short-latency GTO-Ib reflexes are dependent upon both task, as evidenced by changes with postural orientation, and context, such as height-induced postural threat during standing. Golgi tendon organ Ib reflexes are thought to contribute to standing balance control, but it is unknown if they are modulated when people are exposed to a postural threat. We used a novel application of tendon electrical stimulation (TStim) to elicit Ib inhibitory reflexes in the medial gastrocnemius, while actively engaged in upright standing balance, to examine (a) how Ib reflexes to TStim are influenced by upright stance, and (b) the effects of height-induced postural threat on Ib reflexes during standing. TStim evoked short-latency (<47ms) inhibition apparent in trigger-averaged rectified EMG, which was quantified in terms of area, duration and mean amplitude of inhibition. In order to validate the use of TStim in a standing model, TStim-Ib inhibition was compared from conditions where participants were lying prone vs. standing upright. TStim evoked Ib inhibition in both conditions; however, significant reductions in Ib inhibition area (42.2%) and duration (32.9%) were observed during stance. Postural threat, manipulated by having participants stand at LOW (0.8m high, 0.6m from edge) and HIGH (3.2m, at edge) elevated surfaces, significantly reduced Ib inhibition area (32.4%), duration (16.4%) and amplitude (24.8%) in the HIGH, compared to LOW, threat condition. These results demonstrate TStim is a viable technique for investigating Ib reflexes in standing, and confirm Ib reflexes are modulated with postural orientation. The novel observation of reduced Ib inhibition with elevated postural threat reveals that human Ib reflexes are context dependent, and the human Ib reflex pathways are modulated by threat or emotional processing centres of the CNS.

Precise coding of ankle angle and velocity by human calf muscle spindles

Human standing balance control requires the integration of sensory feedback to produce anticipatory, stabilizing ankle torques. However, the ability of human triceps surae muscle spindles to provide reliable sensory feedback regarding the small, slow ankle movements that occur during upright standing has recently come under question. We performed microneurography to directly record axon potentials from single muscle spindle afferents in the human triceps surae during servo-controlled movement of the ankle joint. To simulate movements of the ankle while standing, we delivered random 90-s dorsiflexion/plantar flexion oscillations of the ankle joint, with a peak-to-peak amplitude of 0.7° and frequency content below 0.5Hz. In roughly half of the trials (46%), participants held a low-level, near-isometric contraction of the triceps surae muscles. We demonstrate that afferent activity in a population of muscle spindles closely reflects ankle movements at frequencies and amplitudes characteristic of human standing. Four out of five soleus spindles, and three out of seven gastrocnemius spindles coded for at least a single frequency component of anteroposterior ankle rotation. Concatenating within muscles, coherence was significantly greater for soleus spindles at all stimulus frequencies. Voluntary contraction of the parent muscle reduced spindle sensitivity, but only significantly near the mean power frequency of the stimulus (∼0.3Hz). In conclusion, these results provide direct evidence that triceps surae muscle spindles are potentially capable of providing important sensory feedback for the control of human standing balance.

The effects of shoe heel counter on standing balance control

The effects of shoe heel counter on standing balance control

Stability Limits of Standing Postural Control in Young Male Ving Tsun Chinese Martial Art Practitioners: A Pilot Study in Hong Kong

This study aimed to compare the stability limits of standing balance control between Ving Tsun (VT) practitioners and non-practitioners. Four male VT practitioners (mean age ± standard deviation = 26.3 ± 5.0 years) and 4 healthy active male adults (mean age ± standard deviation = 21.5 ± 2.4 years) as controls participated in the study. Balance ability, specifically limits of stability (LOS) in standing, was assessed using the LOS test. Outcome measures included reaction time, movement velocity, maximum excursion, end-point excursion and directional control in the forward, backward, right and left directions. Results revealed that VT practitioners had lower LOS maximum excursion scores in the backward direction (17.6% lower, p = 0.020), and lower directional control scores in both the backward direction (8.6% lower, p = 0.042) and to the right side (7.7% lower, p = 0.043) compared to the controls. No significant between-group differences in other outcome variables were found (p > 0.05). VT practitioners showed inferior LOS balance performance in standing compared to non-practitioners in general, except that they seemed to have better maximum excursion in the forward direction (effect size = 0.951). Further randomized controlled trials are needed to confirm these results.

Vestibular control of standing balance is enhanced with increased cognitive load.

When cognitive load is elevated during a motor task, cortical inhibition and reaction time are increased; yet, standing balance control is often unchanged. This disconnect is likely explained by compensatory mechanisms within the balance system such as increased sensitivity of the vestibulomotor pathway. This study aimed to determine the effects of increased cognitive load on the vestibular control of standing balance. Participants stood blindfolded on a force plate with their head facing left and arms relaxed at their sides for two trials while exposed to continuous electrical vestibular stimulation (EVS). Participants either stood quietly or executed a cognitive task (double-digit arithmetic). Surface electromyography (EMG) and anterior-posterior ground-body forces (APF) were measured in order to evaluate vestibular-evoked balance responses in the frequency (coherence and gain) and time (cumulant density) domains. Total distance traveled for anterior-posterior center of pressure (COP) was assessed as a metric of balance variability. Despite similar distances traveled for COP, EVS-medial gastrocnemius (MG) EMG and EVS-APF coherence and EVS-TA EMG and EVS-MG EMG gain were elevated for multiple frequencies when standing with increased cognitive load. For the time domain, medium-latency peak amplitudes increased by 13-54% for EVS-APF and EVS-EMG relationships with the cognitive task compared to without. Peak short-latency amplitudes were unchanged. These results indicate that reliance on vestibular control of balance is enhanced when cognitive load is elevated. This augmented neural strategy may act to supplement divided cortical processing resources within the balance system and compensate for the acute neuromuscular modifications associated with increased cognitive demand.

Can augmented feedback facilitate learning a reactive balance task among older adults?

While concurrent augmented visual feedback of the center of pressure (COP) or center of gravity (COG) can improve quiet standing balance control, it is not known whether such feedback improves reactive balance control. Additionally, it is not known whether feedback of the COP or COG is superior. This study aimed to determine whether (1) concurrent augmented feedback can improve reactive balance control, and (2) feedback of the COP or COG is more effective. Forty-eight healthy older adults (60-75years old) were randomly allocated to one of three groups: feedback of the COP, feedback of the COG, or no feedback. The task was to maintain standing while experiencing 30s of continuous pseudo-random perturbations delivered by a moving platform. Participants completed 25 trials with or without feedback (acquisition), immediately followed by 5 trials without feedback (immediate transfer); 5 trials without feedback were completed after a 24-h delay (delayed transfer). The root mean square error (RMSE) of COP-COG, electrodermal level, and co-contraction index were compared between the groups and over time. All three groups reduced RMSE and co-contraction index from the start of the acquisition to the transfer tests, and there were no significant between-group differences in RMSE or co-contraction on the transfer tests. Therefore, all three groups learned the task equally well, and improved balance was achieved with practice via a more efficient control strategy. The two feedback groups reduced electrodermal level with practice, but the no-feedback group did not, suggesting that feedback may help to reduce anxiety.