Postural Control Mechanisms Research Articles

ＳＤＡ法を用いた姿勢制御能の加齢変化の解析

Falling is one of the most common and serious problems because advancing age has been associated with muscle weakness and deterioration of postural control system. The mechanisms contributing to age-related increases in ability of postural control and falls in the elderly remain unclear. The purpose of the stabilogram diffusion analysis(SDA)method was to study change of the mechanism of postural control between young and elderly generation. Any parameters of SDA were compared with several parameters of body sway derived from recordings of the center of pressure(COP)with the aid of a static force platform. The subjects were48healthy young volunteers(age: 18-64yeas, mean±S. D: 33. 6±14. 6years)and41 healthy elderly volunteers(age: 65-87years, mean±S. D: 77.7±4.3years). They quietly stood on a static force plat form with o pen and closing eyes for thirty seconds. The following results were indicated. 1. The elderly group was a significantly than the young group greater in the Diffusion constant Drs and the mean square critical displacement when eyes open and eyes closed. 2. On the elderly group, the correlation between SDA parameters and COP parameters was found to be greater in the closing eye condition than that in the open eye condition. 3. The correlations between diffusion coefficient and the range o f anterior-posterior was greater than the correlations between the diffusion coefficients and the range of medio-lateral. Thus, the muscle of the tibialis anterior and the planter muscles was suggested.

Effects of visually simulated roll motion on vection and postural stabilization

BackgroundVisual motion often provokes vection (the induced perception of self-motion) and postural movement. Postural movement is known to increase during vection, suggesting the same visual motion signal underlies vection and postural control. However, self-motion does not need to be consciously perceived to influence postural control. Therefore, visual motion itself may affect postural control mechanisms. The purpose of the present study was to investigate the effects of visual motion and vection on postural movements during and after exposure to a visual stimulus motion.MethodsEighteen observers completed four experimental conditions, the order of which was counterbalanced across observers. Conditions corresponded to the four possible combinations of rotation direction of the visually simulated roll motion stimulus and the two different visual stimulus patterns. The velocity of the roll motion was held constant in all conditions at 60 deg/s. Observers assumed the standard Romberg stance, and postural movements were measured using a force platform and a head position sensor affixed to a helmet they wore. Observers pressed a button when they perceived vection. Postural responses and psychophysical parameters related to vection were analyzed.ResultsDuring exposure to the moving stimulus, body sway and head position of all observers moved in the same direction as the stimulus. Moreover, they deviated more during vection perception than no-vection-perception, and during no-vection-perception than no-visual-stimulus-motion. The postural movements also fluctuated more during vection-perception than no-vection-perception, and during no-vection-perception than no-visual-stimulus-motion, both in the left/right and anterior/posterior directions. There was no clear habituation for vection and posture, and no effect of stimulus type.ConclusionOur results suggested that visual stimulus motion itself affects postural control, and supported the idea that the same visual motion signal is used for vection and postural control. We speculated that the mechanisms underlying the processing of visual motion signals for postural control and vection perception operate using different thresholds, and that a frame of reference for body orientation perception changed along with vection perception induced further increment of postural sway.

Identification of Aging Effects on the Control of Upright Stance Using a Local Maximum Wavelet Transform Method

The purpose of this study was to investigate aging effects on the mechanisms of postural control during upright stance, and specifically the use of proprioceptive feedback on this control. Thirty-two healthy individuals participated, equally divided among younger (19–22 years) and older groups (54–68 years) and genders. Experimental trials involved several sessions of quiet stance on a firm surface with eyes closed. Center of pressure (COP) data were obtained from a force platform and processed using a new local maximum wavelet transform method. The critical time interval (CTI) derived from this method was proposed to describe the activation period of proprioceptive function, which is mainly influenced by the proprioceptive feedback loop. A reduced CTI was assumed to indicate poorer control based on proprioceptive input. Results showed that younger participants' CTI significantly increased from the first experimental session to consecutive experimental sessions in both the mediolateral (ML) and anteroposteriorer (AP) directions. However, older participates' CTI did not exhibit significant differences between the first and the consequent experimental sessions in either direction. This result suggests that the adaptability of proprioceptive function was impaired with age. Younger adults' CTIs were significantly larger than those of older adults in both ML and AP directions, indicating that among older adults stance control based on proprioceptive function was significantly impaired due to aging.

The control of upright stance in young, elderly and persons with Parkinson's disease

The aims of the present study are twofold: (1) to compare the postural control mechanisms of young and elderly people as well as in Parkinson's disease (PD) patients during quiet standing and (2) to assess the impact of a stooped posture on these mechanisms. All subjects were required to maintain both a side-by-side and a 45° foot position. Elderly subjects performed a third condition where they were requested to mimic the stooped posture as adopted by PD subjects. The net centre of pressure (COP net) and centre of mass (COM) profiles in the anterior/posterior (A/P) and medial/lateral (M/L) planes were analyzed. The COP net signal was recorded from two force plates and was categorized in two mechanisms: an ankle mechanism (COP c ) and a load/unload hip mechanism (COP v ). The results showed similar postural control mechanisms in young, elderly and PD subjects. When the feet were side-by-side, the COP net was controlled by the ankle plantar/dorsiflexors (COP c ) in the A/P direction, while by the hip abductor/adductors (COP v ) controlled in the M/L direction. When the feet were in the 45° position, both the ankle and hip mechanisms contributed to the COP net. However, the PD subjects showed significant smaller RMS amplitudes compared to the elderly people in the 45° foot position and in the stooped posture. These findings suggest that PD subjects resort to a stiffening strategy to control their balance in postural tasks that imply a mixed control (ankle and hip mechanisms) but have adapted to their stooped posture.

How a plantar pressure-based, tongue-placed tactile biofeedback modifies postural control mechanisms during quiet standing

The purpose of the present study was to determine the effects of a plantar pressure-based, tongue-placed tactile biofeedback on postural control mechanisms during quiet standing. To this aim, 16 young healthy adults were asked to stand as immobile as possible with their eyes closed in two conditions of No-biofeedback and Biofeedback. Centre of foot pressure (CoP) displacements, recorded using a force platform, were used to compute the horizontal displacements of the vertical projection of the centre of gravity (CoG( v )) and those of the difference between the CoP and the vertical projection of the CoG (CoP-CoG( v )). Analysis of the CoP-CoG( v ) displacements showed larger root mean square (RMS) and mean power frequencies (MPF) in the Biofeedback than in the No-biofeedback condition. Stabilogram-diffusion analysis further showed a concomitant increased spatial and reduced temporal transition point co-ordinates at which the corrective processes were initiated and an increased persistent behaviour of the CoP-CoG( v ) displacements over the short-term region. Analysis of the CoG( v ) displacements showed decreased RMS and increased MPF in the Biofeedback relative to the No-biofeedback condition. Stabilogram-diffusion analysis further indicated that these effects mainly stem from reduced spatio-temporal transition point co-ordinates at which the corrective process involving CoG( v ) displacements is initiated and an increased anti-persistent behaviour of the CoG( v ) displacements over the long-term region. Altogether, the present findings suggest that the main way the plantar pressure-based, tongue-placed tactile biofeedback improves postural control during quiet standing is via both a reduction of the correction thresholds and an increased efficiency of the corrective mechanism involving the CoG( v ) displacements.

Rehabilitation for hamstring injuries

BACKGROUND: Hamstring injuries are a common musculoskeletal disorder, particularly among athletes. Many factors have been associated with these injuries including motor control and strength, soft tissue length and postural alignment. Well‐established rehabilitation protocols are commonly used in the treatment of this condition, but their effectiveness remains questionable.OBJECTIVES: To evaluate the effectiveness of all rehabilitation strategies employed to promote the return to full strength, range of movement and function of those individuals presenting with all forms of hamstring injury, regardless of site, severity, onset or level of chronicity.SEARCH STRATEGY: We searched the Cochrane Bone, Joint and Muscle Trauma Group Specialised Register (to January 2006), CENTRAL (The Cochrane Library 2006, Issue 1), MEDLINE, EMBASE, PEDro – The Physiotherapy Evidence Database, CINAHL, AMED, SPORTDiscus and reference lists of articles. Date of last search: February 2006. No language restrictions were applied.SELECTION CRITERIA: Selected studies were randomized controlled trials or randomized comparative trials, investigating the effect of at least one rehabilitation strategy, in isolation or combination with another, compared with another strategy or control, performed on individuals presenting with hamstring injuries.DATA COLLECTION AND ANALYSIS: Two review authors performed study selection. Three review authors performed data extraction and methodological quality assessment. Any disagreement was resolved by discussion.MAIN RESULTS: Three trials were included in the review. The main results present limited evidence over a range of techniques and patient groups. There was no trial of intervention versus rest. Only two small trials compared times to return to normal function, and definition of this outcome varied between studies. The first trial, involving 80 athletes, suggested stretching four times a day instead of just once and resulted in a statistically significant reduction in time to return to normal function (mean difference (MD) −1.8 days, 95% confidence interval (CI) −2.15 to −1.45, P<0.001). The second trial, with 24 participants from a diverse sporting background, found that progressive agility and trunk stabilization exercises and icing did not achieve a statistically significant reduction in time to return to full function when compared to stretching and progressive resistance exercises and icing (MD −14.5 days, 95% CI −30.64 to 1.64, P=0.08). The third trial, conducted with 20 non‐athletes, suggests there was no evidence of effect with manual therapy on soft tissue length (MD 10.4°, 95% CI −3.19 to 23.99 in favor of manual therapy, P=0.13), on hamstring muscle peak torque (MD −0.7 foot‐pounds, 95% CI −18.45 to 17.05 in favor of control, P=0.94), or on quadriceps femoris muscle peak torque (MD −22.1 foot‐pounds, 95% CI −59.00 to 14.80 in favor of control, P=0.24) following a single treatment.AUTHORS' CONCLUSIONS: There is limited evidence to suggest that rate of recovery can be increased with an increased daily frequency of hamstring stretching exercises. Consideration should be given to the lumbar spine, sacroiliac and pelvic alignment and postural control mechanisms when managing hamstring injuries. Lumbar stability and pelvic motor control may also be factors in reducing the rate of recurrence of hamstring injury. Until further evidence is available, current practice and widely published rehabilitation protocols cannot either be supported or refuted.

Assessment and Treatment for Postural Control Mechanism due to a Lesion of the Central Nervous System

神経学的障害を持つ患者が機能的活動を再獲得するための過程において，患者が持つ潜在能力を適正に捉え，その顕在化を阻害している因子を改善することは，その評価と治療的アプローチにおける課題である。これらの患者の多くは姿勢制御不全を来たし，機能的活動の阻害因子となっている。随意運動としての行動の発現には姿勢制御が先行すること，姿勢制御のためには異なる種類の多くの感覚入力が必要である事などを考慮すると，姿勢制御を獲得する過程が適応行動の神経基盤として重要であると考える。本稿では臨床的な視点での姿勢制御の構成要素に注目し，神経学的障害を持つ患者の評価と治療的アプローチについて述べる。

The Effects of Muscle Forces on Ankle Joint Kinetics during Postural Balance Control

We assessed the effects of muscle forces on ankle joint kinetics during postural balance control of human boy. Nine male subjects (mean age of 25.8 yrs) participated in the experiment. An ankle joint model assumed ball and socket joint was used, which was capable of three dimensional rotations. A six-camera VICON system was used for motion analysis. Waist pulling system and force platform were adopted for forward sway and GRF (ground reaction force) measurement. We used linear optimization programs to calculate the variation of muscle forces and angular displacements of shank and foot segments. With the experimental data and linear programs, we could calculate joint reaction forces, and bone-on-bone forces. The results presented in this study give us the insights to understand the roles of lower limb muscles during postural balance control and ankle injury mechanism.

Analysis of Human Postural Control during Spontaneous Sway Using an Optimal Control Model

Models of human postural control aid in understanding human capabilities and limitations, and may facilitate a reduction in injuries related to loss-of-balance. Such a model is presented here to simulate and interpret the postural control system during spontaneous sway. The human body was represented by a simple inverted pendulum, with the neural controller assumed to be an optimal controller that generates spontaneous sway according to a certain performance criterion. In order to accurately simulate existing experimental data, an optimization procedure was used to specify the set of model parameters. Ten independent simulations were performed for both young and older adults. Aging effects were then analyzed based on the simulation results. The results showed that this model was able to simulate some center-of-pressure measures reported in experimental studies, and indicated potential changes in postural control mechanisms caused by aging.

The Mobility Capabilities of Persons With Adolescent Idiopathic Scoliosis

An analysis of differences among healthy elementary school children and those with adolescent idiopathic scoliosis (AIS), and between groups of individuals with AIS with different Cobb angles. To research the differences in dynamic balance among adolescents with a variety of postural statuses and verify the sensitivity value of the Cobb angle. Assuming the biomechanical and functional particularities of the children with AIS, there is a need for an earlier diagnosis. The participants' balance (left and right step test) was estimated using electromyography and the reaction of base power on the platform. Discriminant analysis confirmed a significant difference between the participants with AIS and healthy persons on the left step test. The values of the lumbal erector muscles, right gluteus, and side-to-side reaction of the force platform are more pronounced than the other variables. There is no significant difference among the participants with various Cobb angles. The dynamic balance tests contribute to the AIS screening process. The pathologic form of AIS and lateralization highly affect dynamic balance. The study confirmed the neurophysicians' claims of the neuroplasticity of the central nervous system. In addition, the research illustrated the compensational functioning of mobility, especially when there is a lack of normal mobility forms, and there are weak postural control mechanisms and proprioception. There was no proof of the value of the Cobb angle as a clinical method and a measurement of the functional capabilities of the participants in the screening process.

Postural control in older adults with cognitive dysfunction

Older adults with dementia are at greater risk for falls and for significant injury than cognitively intact older adults. The cause of falls in older adults is multifactorial, and there appears to be additional contributing factors to falls in older adults with cognitive dysfunction. This paper presents a review of the literature on falls in older adults with cognitive dysfunction. The purpose of this paper is to identify changes in the postural control mechanisms of older adults with cognitive dysfunction that may contribute to the increased risk of falls noted with this population. By developing a better understanding of the particular physical, physiological and perceptual changes that occur in older adults with dementia, healthcare providers may be better able to address the special needs of this population, thus hopefully minimising injury and mortality that may occur as a result of falling.

Leg orientation as a clinical sign for pusher syndrome

BackgroundEffective control of (upright) body posture requires a proper representation of body orientation. Stroke patients with pusher syndrome were shown to suffer from severely disturbed perception of own body orientation. They experience their body as oriented 'upright' when actually tilted by nearly 20° to the ipsilesional side. Thus, it can be expected that postural control mechanisms are impaired accordingly in these patients. Our aim was to investigate pusher patients' spontaneous postural responses of the non-paretic leg and of the head during passive body tilt.MethodsA sideways tilting motion was applied to the trunk of the subject in the roll plane. Stroke patients with pusher syndrome were compared to stroke patients not showing pushing behaviour, patients with acute unilateral vestibular loss, and non brain damaged subjects.ResultsCompared to all groups without pushing behaviour, the non-paretic leg of the pusher patients showed a constant ipsiversive tilt across the whole tilt range for an amount which was observed in the non-pusher subjects when they were tilted for about 15° into the ipsiversive direction.ConclusionThe observation that patients with acute unilateral vestibular loss showed no alterations of leg posture indicates that disturbed vestibular afferences alone are not responsible for the disordered leg responses seen in pusher patients. Our results may suggest that in pusher patients a representation of body orientation is disturbed that drives both conscious perception of body orientation and spontaneous postural adjustment of the non-paretic leg in the roll plane. The investigation of the pusher patients' leg-to-trunk orientation thus could serve as an additional bedside tool to detect pusher syndrome in acute stroke patients.

Changes in Postural Sway and Its Fractions in Conditions of Postural Instability

We investigated changes in postural sway and its fractions associated with manipulations of the dimensions of the support area. Nine healthy adults stood as quietly as possible, with their eyes open, on a force plate as well as on 5 boards with reduced support area. The center of pressure (COP) trajectory was computed and decomposed into rambling (Rm) and trembling (Tr) trajectories. Sway components were quantified using RMS (root mean square) value, average velocity, and sway area. During standing on the force plate, the RMS was larger for the anterior-posterior (AP) sway components than for the mediolateral (ML) components. During standing on boards with reduced support area, sway increased in both directions. The increase was more pronounced when standing on boards with a smaller support area. Changes in the larger dimension of the support area also affected sway, but not as much as changes in the smaller dimension. ML instability had larger effects on indices of sway compared to AP instability. The average velocity of Rm was larger while the average velocity of Tr was smaller in the AP direction vs. the ML direction. The findings can be interpreted within the hypothesis of an active search function of postural sway. During standing on boards with reduced support area, increased sway may by itself lead to loss of balance. The findings also corroborate the hypothesis of Duarte and Zatsiorsky that Rm and Tr reveal different postural control mechanisms.

The Mechanism of Postural Balance Control of High-Heeled Women

High-heeled women have been identified with balance control problems. The purposes of this study were to objectively quantify the displacements and velocities of center-of-pressure (COP) of body during waist pulling and to compare the differences between barefooted and high-heeled situations. We used a waist pulling system which has three different magnitudes to sway the subjects. We found that the kinematic information of barefooted and high-heeled women’s COP is very important in understanding the mechanism of postural balance control of women in every-day life. In the high-heeled’s case, the displacement of COP increases by 9% (1kg), 33% (2kg), 44% (3kg) as against bare footed. Also the velocity of COP grows two times than that of the bare footed. COP analysis in postural balance study of high-heeled women is considered useful in development of the safety systems that prevent high-heeled women from falling.

Reflex control of the spine and posture: a review of the literature from a chiropractic perspective.

ObjectiveThis review details the anatomy and interactions of the postural and somatosensory reflexes. We attempt to identify the important role the nervous system plays in maintaining reflex control of the spine and posture. We also review, illustrate, and discuss how the human vertebral column develops, functions, and adapts to Earth's gravity in an upright position. We identify functional characteristics of the postural reflexes by reporting previous observations of subjects during periods of microgravity or weightlessness.BackgroundHistorically, chiropractic has centered around the concept that the nervous system controls and regulates all other bodily systems; and that disruption to normal nervous system function can contribute to a wide variety of common ailments. Surprisingly, the chiropractic literature has paid relatively little attention to the importance of neurological regulation of static upright human posture. With so much information available on how posture may affect health and function, we felt it important to review the neuroanatomical structures and pathways responsible for maintaining the spine and posture. Maintenance of static upright posture is regulated by the nervous system through the various postural reflexes. Hence, from a chiropractic standpoint, it is clinically beneficial to understand how the individual postural reflexes work, as it may explain some of the clinical presentations seen in chiropractic practice.MethodWe performed a manual search for available relevant textbooks, and a computer search of the MEDLINE, MANTIS, and Index to Chiropractic Literature databases from 1970 to present, using the following key words and phrases: "posture," "ocular," "vestibular," "cervical facet joint," "afferent," "vestibulocollic," "cervicocollic," "postural reflexes," "spaceflight," "microgravity," "weightlessness," "gravity," "posture," and "postural." Studies were selected if they specifically tested any or all of the postural reflexes either in Earth's gravity or in microgravitational environments. Studies testing the function of each postural component, as well as those discussing postural reflex interactions, were also included in this review.DiscussionIt is quite apparent from the indexed literature we searched that posture is largely maintained by reflexive, involuntary control. While reflexive components for postural control are found in skin and joint receptors, somatic graviceptors, and baroreceptors throughout the body, much of the reflexive postural control mechanisms are housed, or occur, within the head and neck region primarily. We suggest that the postural reflexes may function in a hierarchical fashion. This hierarchy may well be based on the gravity-dependent or gravity-independent nature of each postural reflex. Some or all of these postural reflexes may contribute to the development of a postural body scheme, a conceptual internal representation of the external environment under normal gravity. This model may be the framework through which the postural reflexes anticipate and adapt to new gravitational environments.ConclusionVisual and vestibular input, as well as joint and soft tissue mechanoreceptors, are major players in the regulation of static upright posture. Each of these input sources detects and responds to specific types of postural stimulus and perturbations, and each region has specific pathways by which it communicates with other postural reflexes, as well as higher central nervous system structures. This review of the postural reflex structures and mechanisms adds to the growing body of posture rehabilitation literature relating specifically to chiropractic treatment. Chiropractic interest in these reflexes may enhance the ability of chiropractic physicians to treat and correct global spine and posture disorders. With the knowledge and understanding of these postural reflexes, chiropractors can evaluate spinal configurations not only from a segmental perspective, but can also determine how spinal dysfunction may be the ultimate consequence of maintaining an upright posture in the presence of other postural deficits. These perspectives need to be explored in more detail.

Sway patterns in orthostatic tremor: Impairment of postural control mechanisms

Sway parameters in orthostatic tremor (OT) patients were compared with age-matched controls. The effects of vision (eyes open or closed), stance width (feet apart or together), and external support (with or without) on sway and 14-18 Hz energy were measured. Sway in OT patients decreased in the presence of each of the stabilizing factors but the extent of benefit obtained by OT patients was significantly less than controls for support for the sagittal plane (22% vs. 42% decrease; P < 0.01) and feet apart in the mediolateral plane (38% vs. 65% decrease; P < 0.01). Three patients with proprioceptive loss also had a reduced response to these factors. Energy in the 14-18 Hz range did not always change in parallel with sway levels. Vision suppresses activity at the OT frequency in patients. Postural control mechanisms in OT remain responsive to postural conditions, but patients differ significantly from normals in the degree of their responsiveness. OT appears to have disruption of the normal generation or processing of proprioceptive signals as one of its important components.

Postural control and detection of slip/fall initiation in the elderly population

One of the common causes of morbidity and mortality in workplaces is related to slips or falls. Reaction to external disturbances, such as slips or falls, requires a process of perturbation detection and control of motion changes. Postural control is a common mechanism to compensate unexpected displacements of the body. The ability of postural control diminishes with ageing or neuropathy. In this study, two controlled groups, diabetics and non-diabetics in the elderly population, were investigated to compare how different postural control mechanisms would relate to the detection of perturbation and regain of balance. The ultra-low-vibration Sliding Linear Investigative Platform for Analyzing Lower Limb Stability SYSTEM was used to measure the biomechanical changes of posture and perturbation detection. In phase 1 of the analysis, static measures during quiet standing were considered to investigate the relationship between postural stability and perturbation detection capability. In phase 2 of the analysis, dynamic measures during an occurrence of perturbation were analysed. Statistical tests and linear logistic regression models were applied to find differences of postural control mechanisms and to build a predictive model for perturbation detection quantitatively. It is anticipated that the results of this study will contribute to more comprehensive understanding of postural control mechanisms and design of slip/fall prevention programmes.

Acute Effects of a Single Bout of Resistance Exercise on Postural Control in Elderly Persons

Many elderly persons are engaging in resistance exercise to counter muscle atrophy due to aging. Here, the acute effects of resistance exercise on postural control mechanisms were examined. Postural control was quantified by mean square center-of-pressure displacements were calculated utilizing force vectors in accordance with previously developed equations. Stabilogram-diffusion plots utilized the displacements as data points after curve-fitting techniques were applied. Two regions, representing the open-loop and closed-loop postural control mechanisms, are shown by the plots and separated at the critical point, which represents the shift in control mechanisms. 21 older adults (age M=71.2, SD=3.84, range 66-81 years) performed three sets of 10-12 repetitions for six resistance exercises for the lower extremity until fatigue. Immediately after exercise, postural stability was reduced. This was represented by a shift of the critical point to the right, indicating an increase in open-loop control. Since resistance training has an acute negative effect on postural control, it is advised to assist elderly clients carefully and immediately after resistance training.

Detecting and Understanding Differences in Postural Sway. Focus on “A New Interpretation of Spontaneous Sway Measures Based on a Simple Model of Human Postural Control”

Postural sway during quiet standing reflects the interplay between destabilizing forces acting on the body and actions by the postural control system to prevent a loss of balance. Hence, balance impairments caused by altered sensory, motor, or central nervous function related to such factors as

NEUROMUSCULAR RESPONSES OF TRAINED BALLET DANCERS TO POSTURAL PERTURBATIONS

The balance of trained ballet dancers and non-dancer controls was mechanically perturbed in order to evaluate the time of onset of muscle activation and the consistency of muscle activation. Results supported the prediction that ballet dancers have significantly faster long-latency (LL) neuromuscular responses than controls and are significantly more consistent in muscle activation. These findings indicate a superior postural control mechanism in trained dancers and may explain the ability of dancers to maintain static balances over a small base of support.