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Human balance and posture control during standing and walking

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Abstract

The common denominator in the assessment of human balance and posture is the inverted pendulum model. If we focus on appropriate versions of the model we can use it to identify the gravitational and acceleration perturbations and pinpoint the motor mechanisms that can defend against any perturbation.We saw that in quiet standing an ankle strategy applies only in the AP direction and that a separate hip load/unload strategy by the hip abd/adductors is the totally dominant defence in the ML direction when standing with feet side by side. In other standing positions (tandem, or intermediate) the two mechanisms still work separately, but their roles reverse. In the tandem position ML balance is an ankle mechanism (invertors/evertors) while in the AP direction a hip load/unloading mechanism dominates.During initiation and termination of gait these two separate mechanisms control the trajectory of the COP to ensure the desired acceleration and deceleration of the COM. During initiation the initial acceleration of the COM forward towards the stance limb is achieved by a posterior and lateral movement of the COP towards the swing limb. After this release phase there is a sudden loading of the stance limb which shifts the COP to the stance limb. The COM is now accelerated forward and laterally towards the future position of the swinging foot. Also ML shifts of the COP were controlled by the hip abductors/adductors and all AP shifts were under the control of the ankle plantar/dorsiflexors. During termination the trajectory of both COM and COP reverse. As the final weight-bearing on the stance foot takes place the COM is passing forward along the medial border of that foot. Hyperactivity of that foot's plantarflexors takes the COP forward and when the final foot begins to bear weight the COP moves rapidly across and suddenly stops at a position ahead of the future position of the COM. Then the plantarflexors of both feet release and allow the COP to move posteriorly and approach the COM and meet it as quiet stance is achieved. The inverted pendulum model permitted us to understand the separate roles of the two mechanisms during these critical unbalancing and rebalancing periods.During walking the inverted pendulum model explained the dynamics of the balance of HAT in both the AP and ML directions. Here the model includes the couple due to the acceleration of the weight-bearing hip as well as gravitational perturbations. The exclusive control of AP balance and posture are the hip extensors and flexors, while in the ML direction the dominant control is with the hip abductors with very minor adductor involvement. At the ankle the inverted pendulum model sees the COM passing forward along the medial border to the weight-bearing foot. The model predicts that during single support the body is falling forward and being accelerated medially towards the future position of the swing foot. The model predicts an insignificant role of the ankle invertors/evertors in the ML control. Rather, the future position of the swing foot is the critical variable or more specifically the lateral displacement from the COM at the start of single support. The position is actually under the control of the hip abd/adductors during the previous early swing phase.The critical importance of the hip abductors/adductors in balance during all phases of standing and walking is now evident. This separate mechanism is important from a neural control perspective and clinically it focuses major attention on therapy and potential problems with some surgical procedures. On the other hand the minuscule role of the ankle invertors/evertors is important to note. Except for the tandem standing position these muscles have negligible involvement in balance control.

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... By using a single force plate, the understanding of balance control concerns how postural sway changes in both directions (AP and ML) [26], and how it associates with the center of gravity (CoG) [27] or with the limits of the basis of support [28]. Winter [29] argued that feet placement in quiet standing should affect CoP; therefore, to improve the understanding of balance control, he proposed to use two force plates and evaluated different feet positions [30][31][32]. Duarte and Zatsiorsky [33] discussed what happens when feet are free to stay and move on the force plate, describing the CoP migration patterns. ...
... Since these studies, diverse approaches were used regarding the number of force plates and foot placement. One study aimed to assess each limb behavior during two pyramids using two force plates (one foot in each), considering the CoPnet as the weighted sum of CoPleft and CoPright [3,29], as presented below: ...
... where Fz left and Fz right are the vertical GRF of the left and right foot, respectively. When only one foot was on the ground, the CoP was within that foot's plantar surface; if both feet were in contact with the ground, the CoP was somewhere within the basis of support, depending on the position of the vertical projection of the CoG, the relative weight on each foot and their position [29]. To distinguish the CoP measured from a force plate and the CoP calculated from two force plates, CoP net can be defined according to Equation (1) [29]. ...
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The biomechanical analysis of Acrobatic Gymnastics elements has not been extensively explored in scientific research to date. Due to the increased challenge of implementing experimental protocols and collecting data from multiple individuals, it is required to develop strategies that allow a safe, valid and reproducible methodology. This work aims to collect information and systematically analyze the biomechanical approach in Acrobatic Gymnastics to date. A search was conducted in the Web of Science, Scopus, EBSCO, PubMed and ISBS databases. After the selection and quality-control phases, fourteen documents were included. The results revealed that the biomechanical research in Acrobatics has been focused on balance evaluation, in which the force plate and the center of pressure are the most used instrument and variable, respectively. Research has been focused on kinetics evaluation. Kinematics analysis of pair/group elements would provide scientific answers to unresolved problems, considering that Gymnastics provides almost limitless possibilities to study human motion. Researchers should focus on the type of element, difficulty degree, main characteristics, relationship between the instrument and floor surface specificity and safety conditions. We encourage gymnastics clubs and coaches to establish networks with biomechanics laboratories, allowing to bridge the gap between research and practice.
... These results are very important for people with PD, as reduced ROM of the trunk and arm swing has been shown as a marker of early PD [26]. Trunk rotation during walking plays a critical role in successful locomotion and contributes to gait stability among older people [28][29][30] and PD [31]. Axial rigidity of the hips and trunk in people with PD is associated with motor signs (e.g., poor mobility and postural instability) [31]. ...
... Axial rigidity of the hips and trunk in people with PD is associated with motor signs (e.g., poor mobility and postural instability) [31]. Reduced lateral and rotational trunk motion during gait is a sign of impaired dynamic balance and increased fall risk [28,31]. Arm swing aids dynamic stability and efficiency of gait [28][29][30] and people with PD have decreased RoM and increased asymmetry in arm swing compared to healthy controls, even when newly diagnosed [32]. ...
... Reduced lateral and rotational trunk motion during gait is a sign of impaired dynamic balance and increased fall risk [28,31]. Arm swing aids dynamic stability and efficiency of gait [28][29][30] and people with PD have decreased RoM and increased asymmetry in arm swing compared to healthy controls, even when newly diagnosed [32]. Mobility Rehab is unique in providing real-time measures of arm swing and trunk lateral stability while walking, in addition to spatial and temporal gait metrics of the lower body. ...
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We tested the feasibility of one session of treadmill training using a novel physical therapist assisted system (Mobility Rehab) using wearable sensors on the upper and lower limbs of 10 people with Parkinson’s disease (PD). Participants performed a 2-min walk overground before and after 15 min of treadmill training with Mobility Rehab, which included an electronic tablet (to visualize gait metrics) and five Opal sensors placed on both the wrists and feet and on the sternum area to measure gait and provide feedback on six gait metrics (foot-strike angle, trunk coronal range-of-motion (ROM), arm swing ROM, double-support duration, gait-cycle duration, and step asymmetry). The physical therapist used Mobility Rehab to select one or two gait metrics (from the six) to focus on during the treadmill training. Foot-strike angle (effect size (ES) = 0.56, 95% Confidence Interval (CI) = 0.14 to 0.97), trunk coronal RoM (ES = 1.39, 95% CI = 0.73 to 2.06), and arm swing RoM (ES = 1.64, 95% CI = 0.71 to 2.58) during overground walking showed significant and moderate-to-large ES following treadmill training with Mobility Rehab. Participants perceived moderate (60%) and excellent (30%) effects of Mobility Rehab on their gait. No adverse events were reported. One session of treadmill training with Mobility Rehab is feasible for people with mild-to-moderate PD.
... The culmination of this response is to adjust foot placement, which defines the base of support (BOS), so that the vertical ground reaction force can create a torque that counterbalances gravity's effect on the dynamical state (position, velocity, and momentum) of the Center of Mass (COM) [15,17,19]. Thus, the objective of the neuromuscular system is to relocate the center of pressure (COP), the point of application of the ground reaction force, to attenuate and redirect the falling COM to maintain upright posture [15,20,21]. Previous research suggests that feedback mechanisms are sensitive to age-associated changes meaning that, compared to their younger counterparts, older adults show increased delays in detecting perturbation onset and executing the recovery response [15][16][17]22]. ...
... Trips occur when the swinging leg impacts an external object impeding its forward progression [15]. This creates a destabilizing scenario as the dynamical state of the COM, during single support, is already ahead of the COP and outside the BOS [15,20,23]. Thus, stability is only achieved by appropriate foot placement of the swinging leg at upcoming initial-contact [20]. ...
... This creates a destabilizing scenario as the dynamical state of the COM, during single support, is already ahead of the COP and outside the BOS [15,20,23]. Thus, stability is only achieved by appropriate foot placement of the swinging leg at upcoming initial-contact [20]. However, obstacle impact not only obstructs the swinging leg's trajectory, but the collision also imparts a forward rotation on the COM [15,24]. ...
Article
Background Trips and slips increase fall risk for young and older adults. To examine recovery responses, studies utilized treadmill and/or over-ground methods to simulate real-world perturbations. However, differences in the recovery response between treadmill and over-ground perturbations remain unexamined. Research Question To assess the current literature on the reactive recovery responses between over-ground- and split-belt treadmill trips and slips as well as the effect of aging on these responses. Methods PubMed, Medline, Web of Science, SCOPUS, and Cochrane databases were searched for publications examining trips and slips in healthy young, healthy older adults, and older adults who fall. Included articles were in English, full-text accessible, and biomechanically quantified the reactive recovery responses for slips and trips during either over-ground or split-belt treadmill protocols. The initial database search yielded 1075 articles and 31 articles were included after title, abstract, and full-text screening. Results For slips, 7 articles utilized lubricated surfaces while 5 articles used treadmills. Further, 3 studies examined differences between older and younger adults. For trips, 9 articles utilized obstacles and 7 used treadmills. Further, 4 articles examined differences between older and young adults and 1 article only examined older adults during over-ground trips. For both perturbations, treadmill and over-ground protocols demonstrated similar anteroposterior destabilization on the center of mass. In the mediolateral direction, over-ground slips consistently found a lateral destabilization while treadmill articles did not examine this direction. Foot placement recovery responses varied less for both perturbation directions on a treadmill compared to over-ground. Significance Although treadmill and over-ground perturbations destabilize the center of mass similarly, the recovery response to these perturbations were different on treadmills. Specifically, recovery responses were more consistent for both slips and trips on treadmills. As older adults have difficulty in perturbation recovery scaling, treadmills may be limited in their ability to investigate the variety of aging impairments on perturbation recovery responses.
... To date, there is only limited and partly 26 inconsistent research available which specifically addressed this question for VR 27 room-scale applications. Briefly summarized, researchers found a decrease in stride 28 length [19], a decrease of walking speed, step length, and an increase of double support 29 [20], while others reported a decrease in cadence [21]. In addition, Janeh et al. [22] 30 reported that the decrease of walking speed during walking in the VR compared to the 31 real-world did not normalize even during prolonged exposure to the VR environment. ...
... 52 For this reason a more specific analysis is needed to better understand potential 53 effects of VR on our gait behavior. Gait is a dynamic motor task where the Center of 54 Mass (COM) is held outside of the base of support (BoS) for the majority of the gait 55 cycle, hereby defined as dynamic balance [28]. In this scenario, stability is achieved by 56 the neuromuscular system counteracting the gravitational and joint reaction forces 57 acting on the upper body to avert an uncontrolled fall [28]. ...
... Gait is a dynamic motor task where the Center of 54 Mass (COM) is held outside of the base of support (BoS) for the majority of the gait 55 cycle, hereby defined as dynamic balance [28]. In this scenario, stability is achieved by 56 the neuromuscular system counteracting the gravitational and joint reaction forces 57 acting on the upper body to avert an uncontrolled fall [28]. One of the primary 58 mechanisms to counteract these forces and maintain dynamic balance is through 59 effective foot placement [28][29][30]. ...
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This study analyzed the effects of walking freely in Virtual Reality (VR) compared to walking in the real-world on dynamic balance and postural control. For this purpose nine male and twelve female healthy participants underwent standard 3D gait analysis while walking randomly in a real laboratory and in a room-scale overground VR environment resembling the real laboratory. The VR was delivered to participants by a head-mounted-display which was operated wirelessly and calibrated to the real-world. Dynamic balance was assessed with three outcomes: the Margin of Stability (MOS) in the anteroposterior (AP-MOS) and mediolateral (ML-MOS) directions at initial-contact, the relationship between the mediolateral Center of Mass (COM) position and acceleration at mid-stance with subsequent step width, and trunk kinematics during the entire gait cycle. We observed increased mediolateral (ML) trunk linear velocity variability, an increased coupling of the COM position and acceleration with subsequent step width, and a decrease in AP-MOS while walking in VR, but no change in ML-MOS when walking in VR. We conclude that walking in VR results in a less reliable optical flow, indicated by increased mediolateral trunk kinematic variability, which seems to be compensated by the participants by slightly reweighing sensorimotor input and thereby consciously tightening the coupling between the COM and foot placement to avoid a loss of balance. Our results are particularly valuable for future developers who want to use VR to support gait analysis and rehabilitation.
... "Balance is a generic term describing the dynamics of body posture to prevent falling" (Winter, 1995, 194). The operation of the sensorimotor system regulating balance can be observed by describing the pathway of the vertical ground reaction force, also known as center of pressure (COP; Winter, 1995). In other terms, the COP based variables describe the motor activity generated to steer the body's sway and not the actual movement of the center of mass (Winter, 1995). ...
... The operation of the sensorimotor system regulating balance can be observed by describing the pathway of the vertical ground reaction force, also known as center of pressure (COP; Winter, 1995). In other terms, the COP based variables describe the motor activity generated to steer the body's sway and not the actual movement of the center of mass (Winter, 1995). Nevertheless, for consistency with other publications, we will discuss COP-based variables, as a proxy measure of body sway. ...
... For example, if vision is removed, sway variables such as velocity or range may slightly increase (Roman-Liu, 2018). During quiet standing with approximately parallel feet, sway on the sagittal plane predominantly means rotation around the ankle and muscle activity at the ankle (Winter, 1995). Rotation at the hip also occurs but plays a smaller role under these conditions (Creath et al., 2005). ...
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Background Fear of movement is thought to interfere with the recovery from low back pain (LBP). To date, the relationship between fear of movement and postural balance has not been adequately elucidated. Recent findings suggest that more specific fears need to be assessed and put in relation to a specific movement task. We propose that the fear to bend the trunk in a certain direction is distinctly related to the amount of postural sway in different directions. Therefore, our aim was to investigate whether fear of movement in general and fear of bending the trunk in a certain plane is related to postural sway. Methods Data was collected from participants with LBP during two assessments ~3 weeks apart. Postural sway was measured with a force-platform during quiet standing with the eyes closed. Fear of movement was assessed with an abbreviated version of the Tampa Scale of Kinesiophobia (TSK-11) and custom items referring to fear of bending the trunk in the sagittal and the frontal plane. Results Based on data from 25 participants, fear of bending the trunk in the frontal plane was positively related to displacement in the sagittal and frontal plane and to velocity in the frontal plane ( χ ² = 4.35, p = 0.04; χ ² = 8.15, p = 0.004; χ ² = 9.79, p = 0.002). Fear of bending the trunk in the sagittal plane was not associated with any direction specific measure of sway. A positive relation of the TSK-11 with velocity of the frontal plane ( χ ² = 7.14, p = 0.008) was found, but no association with undirected measures of sway. Discussion Fear of bending the trunk in the frontal plane may be especially relevant to postural sway under the investigated stance conditions. It is possible that fear of bending the trunk in the frontal plane could interfere with balance control at the hip, shifting the weight from side to side to control balance. Conclusion For the first time the directional relationship of fear of movement and postural sway was studied. Fear of bending the trunk in the frontal plane was positively associated with several measures of postural sway.
... VIB-PR are often measured on a force platform using variables related to center of pressure (COP) displacements. Linear COP variables measured during different postural conditions without vibration are recognized as valid and reliable to assess postural control and to provide an estimation for the risk of falling [9][10][11]. For example, higher amplitude or velocity of COP displacements observed in older individuals during a bipodal stance would likely reflect less efficient postural control mechanisms and increased risk of falling [9]. ...
... Different underlying mechanisms are likely at play between the early and later patterns of VIB-PR. Based on the inverted pendulum [11] and sensory re-weighting theories [14,23] for postural control, the sensory information originating from VIB of ankle tendons first results in a quick response from the vibrated muscle to counteract their perceived stretching and maintain balance. This first response was evident in Fig 1 (and in others [1]), that is, the small COP displacement in the opposite direction during the first 0.5 s after VIB start. ...
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Background The vibration-induced postural reaction paradigm (VIB-PR) offers a unique way for investigating sensorimotor control mechanisms. Measures of VIB-PR are usually calculated from the whole VIB period, yet recent evidence proposed that distinctive mechanisms are likely at play between the early vs. later phases of the postural reaction. Objectives The present work verified if spatiotemporal analyses of center of pressure (COP) displacements can detect differences between these early/later phases of VIB-PR. Also, we further characterized the intra/inter-individual variability of COP measurements, since the underlying variability of VIB-PR remains largely unexplored. Methods Twenty young volunteers realized two experimental conditions of bipodal stance with eyes closed: (i) bilateral VIB of tibialis anterior (TIB) and (ii) Achilles’ (ACH) tendons. Each condition consisted of five trials and lasted 30 s as follows: 10 s baseline, 10 s VIB and 10 s post-VIB. Linear COP variables (antero-posterior (AP) amplitude & velocity) were computed for both VIB and post-VIB periods using the following time-windows: early 2 s, the later 8 s and the whole 10 s duration. Intra- and inter-individual variability were respectively estimated using the standard error of the measurement and the coefficient of variation. Both variability metrics were obtained using five vs. the first three trials. Results Significant contrasts were found between time-windows for both VIB and post-VIB periods. COP variables were generally higher during the early 2 s phase compared to the later 8 s phase for both TIB [mean difference between 8 s– 2 s phases: Amplitude AP = -1.11 ± 1.14 cm during VIB and -2.99 ± 1.31 during post-VIB; Velocity AP = -1.17 ± 0.86 cm/s during VIB and -3.13 ± 1.31 cm/s during post-VIB] and ACH tendons [Amplitude AP = -0.37 ± 0.98 cm during VIB and -3.41 ± 1.20 during post-VIB; Velocity AP = -0.31 ± 0.59 cm/s during VIB and -3.89 ± 1.52 cm/s during post-VIB]. Most within- and between-subject variability scores were below 30% and using three instead of five trials had no impact on variability. VIB-PR patterns were quite similar within a same person, but variable behaviors were observed between individuals during the later phase. Conclusion Our study highlights the relevance of identifying and separately analyzing distinct phases within VIB-PR patterns, as well as characterizing how these patterns vary at the individual level.
... Balance is defined as the dynamics of posture control that prevents falls in an individual [1]. Several sensory and motor responses participate in the balance control process to keep the center of mass of the body within the support base [2], [3]. ...
... This difference between the AP and ML directions could be explained by the strategies used for balance control during standing described by Winter [1]. During quiet standing and small perturbations, the ankle strategy, which relies on the ankle's plantar flexor / dorsiflexor muscles alone, is sufficient to control balance. ...
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The prevalence and impact of balance impairments and falls in older adults have motivated several studies on the characterization of human balance. This study aimed to determine the ability of recurrence quantification analysis (RQA) measures to characterize balance control during quiet standing in young and older adults and to discriminate between different fall risk groups. We analyze center pressure trajectories in the medial-lateral and anterior-posterior directions from a publicly available static posturography dataset that contains tests acquired under four vision-surface testing conditions. Participants were retrospectively classified as young adults (age<60, n=85), non-fallers (age≥60, falls=0, n=56), and fallers (age≥60, falls≥1, n=18). Mixed ANOVA and post hoc analyzes were performed to test for differences between groups. For CoP fluctuations in the anterior-posterior direction, all RQA measures showed significantly higher values for young than older adults when standing on a compliant surface, indicating less predictable and stable balance control among seniors under testing conditions where sensory information is restricted or altered. However, no significant differences between non-fallers and fallers were observed. These results support the use of RQA to characterize balance control in young and old adults, but not to discriminate between different fall risk groups.
... Indeed, voluntary sideways steps is a more active displacement because it requires more central nervous system involvement, in contrast to rhythmic forward walking, which is mainly passive and relies on the spontaneous pendular dynamics of lower limbs [16]. Voluntary sideways steps could also specifically target the strengthening of the frontal plane hip muscles (abductors/ adductors) which play an essential role in stabilizing the head, arms, and trunk in the frontal plane during standing and walking [17]. Moreover, the feasibility and benefits of a 6-week non-targeted sideways steps intervention in a small group of community-dwelling adults in their seventies have already been demonstrated [18]. ...
... Our gait speed results are slightly lower than or compatible with the speed of similarly aged adults living in residential care facilities (0.4±0.2m s −1 ) [39] and the definition of household ambulators (<0.40m s −1 ) [42]. The Tinetti score was 20 [18][19][20][21] points in the STEP group and 18 [16][17][18][19][20][21][22][23][24][25] in the CTRL group. These scores are also consistent with the results of a study conducted on old adult nursing home residents (20 points) [43]. ...
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Background Side-stepping is a potential exercise program to reduce fall risk in community-dwelling adults in their seventies, but it has never been tested in nursing home residents. This was a pilot quasi-experimental study to examine the feasibility and potential mobility and balance benefits of an intervention based on voluntary non-targeted side-stepping exercises in nursing home residents who fall recurrently. Methods Twenty-two participants were recruited and non-randomly assigned to an intervention group ( $$n=$$ n = 11, side-stepping exercises, STEP) participating in an 8-week protocol and to a control group ( $$n =$$ n = 11, usual physiotherapy care, CTRL). They were clinically assessed at 4-time points: baseline, after 4 and 8 weeks, and after a 4-week follow-up period (usual physiotherapy care). Statistical differences between time points were assessed with a Friedman repeated measures ANOVA on ranks or a one-way repeated measures ANOVA. Results Compared to baseline, significant benefits were observed in the STEP group at 8 weeks for the Timed Up and Go ( $$p =$$ p = 0.020) and 6-minute walking test ( $$p =$$ p = 0.001) as well as for the Berg Balance Scale ( $$p =$$ p = 0.041) and Mini motor test ( $$p =$$ p = 0.026). At follow-up, the Tinetti Performance Oriented Mobility Assessment and Berg Balance Scale significantly worsened in the STEP group ( $$p =$$ p = 0.009 and $$p<$$ p < 0.001, respectively). No significant differences were found between the groups at the same time points. Conclusions Our intervention was feasible and improved mobility and balance after almost 8 weeks. Studies with larger samples and randomized control trials are needed to consolidate our preliminary observations and confirm the deterioration of some tests when side-stepping exercises are discontinued. Trial registration Identifier: ISRCTN13584053. Retrospectively registered 01/09/2022.
... Postural stability is defined as the ability to maintain a person's center of gravity within the base of support (BOS) and is achieved by coordinating movements across several joints with the help of the postural control feedback systems (visual, vestibular, and proprioception) [5]. Being bipedal makes human postural control and locomotion unique, with static postures assumed with both or one foot on the ground, while locomotion involves phases during which only one foot is in contact with the ground during walking and no foot in contact with the ground during running [5]. ...
... Postural stability is defined as the ability to maintain a person's center of gravity within the base of support (BOS) and is achieved by coordinating movements across several joints with the help of the postural control feedback systems (visual, vestibular, and proprioception) [5]. Being bipedal makes human postural control and locomotion unique, with static postures assumed with both or one foot on the ground, while locomotion involves phases during which only one foot is in contact with the ground during walking and no foot in contact with the ground during running [5]. The fundamental prerequisite for a fall includes; an initial loss of balance induced by a perturbation such as a slip, trip, misstep or a collision and a failure of the balance recovery mechanisms to counteract the destabilization [6]. ...
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While design modifications present on work boots improve safety, they may not always provide optimal human performance during work tasks. Understanding the impact of these different design features on biomechanical and physiological postural control and locomotion variables can aid in better design modifications that can provide a safe and efficient human performance. This brief review focuses on a series of studies conducted by the current research team, that have tested three different work boots (SB: high-top steel-toed work boots; TB: high-top tactical work boots; SR: low-top slip-resistant work boots). The series of studies included testing of these work boots or combinations of them under acute and chronic simulated occupational workloads, assessing biomechanical variable such as postural stability, gait, slips, and muscle activity, as well as physiological variables such as heart rate, energy expenditure, oxygen consumption, and pain perception. The impact of each of the work boots and their design feature on postural control and locomotion are summarized from these studies’ previously published literature. Finally, work boot design suggestions for optimal human performance are provided for better work boot selection, modification, and design.
... Düzenli egzersiz çalışmaları altüst olmuş homeostatik mekanizmaların normal fizyolojik sınırlar içerinde çalışmasını sağlamaktadır (Pedersen ve Hoffman;2000, Madden ve Felten;1995). Fiziksel aktivite ya da egzersiz de başlangıçta organizmanın iç koşullarını değiştiren, iç dengeyi bozan bir strestir. Bu streslere karşı, vücutta iç ortam koşullarının sabit tutulmasını sağlayacak otonomik sistemler bulunmaktadır. ...
... İç ve dış koşulların değişmesi, fiziksel ya da mental stres durumları, değişen çevre koşulları gibi faktörler vücudun denge durumunu bozar. Bu dengenin korunması için mücadele eden sistem noroendokrin sistemdir (Pedersen ve Hoffman;2000, Madden ve Felten;1995). Egzersiz organizmanın koşullarını değiştiren ve dengeyi bozan bir strestir. Bu streslere karşı vücutta, organizmanın iç ortamının dengede kalmasını sağlayan otonomik sistemler yer almaktadır. ...
... When standing still, the centre of pressure (COP) moves to control postural sway [6]. Therefore, examining COP movement during quiet standing can inform how well balance is controlled. ...
... In quiet standing, the COP moves to control postural sway [6]. Therefore, the magnitude of COP fluctuations can be used as a proxy measure for the amount of postural sway [34]. ...
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Background People with stroke often have asymmetric motor impairment. Investigating asymmetries in, and dynamic properties of, centre of pressure movement during quiet standing can inform how well balance is controlled. Research question What are the test-retest reliabilities of novel measures of quiet standing balance control in people with chronic stroke? Methods Twenty people with chronic stroke (>6 months post-stroke), who were able to stand for at least 30 seconds without support, were recruited. Participants completed two 30-second quiet standing trials in a standardized position. Novel measures of quiet standing balance control included: symmetry of variability in centre of pressure displacement and velocity, between-limb synchronization, and sample entropy. Root mean square of centre of pressure displacement and velocity in the antero-posterior and medio-lateral directions were also calculated. Intraclass correlation coefficients (ICCs) were used to determine test-retest reliability, and Bland-Altman plots were created to examine proportional biases. Results ICC 3,2 were between 0.79 and 0.95 for all variables, indicating ‘good’ to ‘excellent’ reliability (>0.75). However, ICC 3,1 for symmetry indices and between-limb synchronization were <0.75. Bland-Altman plots revealed possible proportional biases for root mean square of medio-lateral centre of pressure displacement and velocity and between-limb synchronization, with larger between-trial differences for participants with worse values. Significance These findings suggest that centre of pressure measures extracted from a single 30-second quiet standing trial may have sufficient reliability for some research studies in chronic stroke. However, for clinical applications, the average of at least two trials may be required.
... The balance of people with amputation was first studied by quantifying the postural sway of the subjects [7]. Winter et al. [8] defined the balance as a generic term describing the dynamics of body posture to prevent falling and modeled the human balance during quiet standing using an inverted pendulum model. Thus, the static balance is defined as the ability to keep the vertical projection of the center of mass (COM) within the base of support. ...
... Thus, the static balance is defined as the ability to keep the vertical projection of the center of mass (COM) within the base of support. According to the inverted pendulum model, the center of pressure (COP) is defined as the point of location of the vertical ground reaction force vector [8]. Hof et al. [9] described three mechanisms allowing humans to maintain their balance: the ankle, the hip and the stepping strategies. ...
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After a transtibial amputation, the prosthetic foot aims at replacing the missing ankle joint. Due to alteration of proprioception and mobility, the static balance of amputees is challenging. The stiffness of most of the usual prosthetic feet cannot adapt according to the situation. Thus, the control of the user’s balance is closely related to the ankle stiffness value. The aim of this study is to evaluate both the impact of the ankle stiffness and the visual system on static balance. In order to avoid bias relative to different levels of residual proprioception among individuals, the study has been carried out on healthy subjects wearing lower limb prosthetic simulators under each foot. This configuration could be considered as a relevant model to isolate the effect of the stiffness. Eleven subjects wearing prosthetic feet with different modules were asked to remain as static as possible both with open eyes (OE) and closed eyes (CE). The center of pressure (COP) displacements and the joint angles range of motion (ROM) were experimentally assessed. The length of the major axis of the COP 95% confidence ellipse was projected on the antero-posterior direction (AP range). Linear regression models of the AP range and joint angles ROM as a function of the situation (OE and CE) and of the normalized ankle stiffness were created. A one-way analysis of variance test was performed on the model of the AP range. Linear regression coefficients and 95% confidence intervals (CI) were calculated between the AP range and the normalized ankle stiffness and between the joint angles ROM and the normalized ankle stiffness both in OE and CE. This study confirmed that static balance decreases when ankle stiffness decreases. The results also showed that a visual system alteration amplifies more significantly the decrease of static balance of people wearing prosthetic feet and has no significant influence on non-amputated subjects. The slope of the linear regression for the AP range according to the normalized ankle stiffness was equal to −9.86 (CI: −16.03, −3.69) with CE and −2.39 (CI: −4.94, 0.17) with OE. Both the normalized ankle stiffness and the visual system had a significant impact on the AP range (pvalue<0.05). The ankle stiffness is an interesting parameter as it has a high impact on the gait and on the static balance of the users and it must be controlled to properly design prosthetic feet.
... One often invokes an in-place postural response without changing foot configuration to stay balanced. In platform standing studies, individuals flex the ankle to small perturbations, and as the perturbation increases, individuals may rely on the hips to regain balance [13]. Sometimes, one requires a change-insupport response by taking a step or reaching for support to regain stability [14], [15]. ...
... In standing perturbation studies, receptors near the area of the perturbation respond first [13]. Thus, platform perturbations would initially cause ankle flexion with TA and MG muscle responses. ...
... The main pathways of transmission of proprioceptive and exteroceptive information are via the dorsal column medial lemniscal pathway, posterior and anterior spinocerebellar tracts, and spinoreticular tracts [7], sending feedback information to the cortex to correct movements or to adapt to changes in the environment [8]. When a disease impairs the postural somatosensorial system, the static balance significantly worsens with eyes closed as compensation by the visual sensory system is no longer possible [9], and because the somatosensorial system has a greater contribution to balance than the vestibular system [6,10]. ...
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Motor and somatosensory pathway dysfunction due to degeneration of long tracts in hereditary spastic paraplegias (HSP) indicates that postural abnormalities may be a relevant disease feature. However, balance assessments have been underutilized to study these conditions. How does the static balance of individuals with HSP with eyes open and closed differ from healthy controls, and how does it relate to disease severity? This cross-sectional case–control study assessed the static balance of 17 subjects with genetically confirmed HSP and 17 healthy individuals, evaluating the center of pressure (COP) variables captured by a force platform. The root-mean-square of velocities and mean of displacements amplitudes in mediolateral and anteroposterior axes were correlated with disease severity. All COP parameters’ performances were significantly impaired in HSP subjects compared to controls (p < 0.001 for all comparisons). COP with eyes open and closed differed for all variables within the HSP group, whereas in the control group, differences were observed only for anteroposterior velocity and amplitude. Spastic Paraplegia Rating Scale presented moderate direct correlations with the most COP variables (Rho = − 0.520 to − 0.736). HSP individuals presented significant postural instability with eyes open and to a greater extent with eyes closed, corroborating the clinical findings of somatosensorial and proprioceptive pathways dysfunction. The degrees of proprioceptive and motor impairments are mutually correlated, suggesting that similar pathophysiological mechanisms operate for the degeneration of these long tracts. COP parameters can be seen as disease severity biomarkers of HSP, and they should be assessed in future clinical trials.
... Thus, describing the upright position in terms of one single link between ankle and head (as in a pendulum) is incorrect. The study of the postural control within the inverted pendulum model allowed scientists to describe three strategies for achieving the upright stance: the ankle, the hip and the stepping strategies [11,78]. In order to maintain a stable standing position, the ankle strategy restores the body by changing the angle of the ankle joint, while keeping the other joints rigid. ...
Article
Objective: The observers use the optic flow to control self-motion. However, the current state of knowledge indicates that it is difficult to understand how optic flow is used by the visual system without a direct measurement of the changes in the flow patterns caused by eye movements during natural behaviour. The purpose of this literature review is to highlight the importance of the integration between optic flow and eye movements for postural control. Methods: A literature review of the electronic papers through July 2022 was independently performed by three investigators. The selection of the studies was made by a search on PubMed, Scopus, and Google Scholar with two groups of selected keywords. We excluded papers performed on subjects with pathologies, children, and the elderly. Results: The results of this literature analysis highlight that eye movements are required to drive visual motion processing and heading perception in both static and dynamic contexts. Conclusion: Although we now know many neural mechanisms that process heading direction from the optic flow field, a consideration of optic flow patterns relative to gaze direction provides more detailed information on how the retinal flow field is used to control body balance. Doi: 10.28991/ESJ-2022-06-06-020 Full Text: PDF
... Maintaining balance is based on the broad integration of the activities of various human body systems: vestibular, visual, somatosensory, and motor systems (Nashner, 1997). The functions of the sensory systems ensure the control of head movements in space, the movement of individual body segments in relation to each other or contact with external objects (Winter, 1995;Ivanenko and Gurfinkel, 2018). Their hierarchy changes depending on the conditions in which the stability control processes must take place. ...
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The aim of this study is to determine the influence of training and selection on postural stability and its relationship with the sports level of judo practitioners aged 11–14 years. The study group consisted of 21 children judokas, aged 11–12, and 80 of their non-training peers, as well as 19 adolescent judokas, aged 13–14, and 76 of their non-training peers. The judokas were surveyed during regional championships. The level of achievement was determined by the place taken in the tournament. The balance was assessed with the use of a CQ Stab 2P stabilographic platform (CQ Elektronik System, Poland). The device recorded the position of the foot center of pressure (COP) from 6 sensors; 3 of them being located in each platform plate. The following parameters describing the movement of the foot COP were analyzed: total path length calculated in both axes (SP); mean COP inclination (MA), size of the surface area delineated by COP (SA); mean COP frequency (MF). Significantly higher values of SP, MA, and SA were noted in non-training children (aged 11–12), while MF values were significantly higher in young judokas. The same regularity was found in the older age group. Upon comparing the means between children judokas and adolescent judokas, significant differences were noted in the case of SP and MF. In both cases, higher mean values were found in the younger judoka group. A similar comparison in the non-training group indicates statistically significant better values of all analyzed indicators in the 13–14 year-old group, except for MF. Upon examining the relationship between the values of the parameters characterizing the balance level and the sports level, both in the group of training children and adolescents, insignificant values of correlation coefficients were obtained.
... One of the main measures for the analysis of PC in different contexts is center of pressure (COP), which is the point of the vertical ground reaction force vector that corresponds to the weighted average of all pressures on the surface of the area in contact with the ground (Winter, 1995). Thus, PC can be analyzed based on COP variables furnished by a force plate, which provides information on the neuromuscular and biomechanical control mechanisms used for maintaining PC (Nardone & Schieppati, 2010). ...
Article
The postural system requires the sensory systems to maintain postural control (PC). Blind subjects use the somatosensory system to keep PC whereas sighted subjects use the visual system. So what happens to PC when challenging the sensory systems? We analyzed the center of pressure (COP) in ten blind and 10 sighted subjects under conditions: eyes open/closed (interference of visual system) and on firm/foam surfaces (interference of somatosensory system). We found that under the condition of eyes open on a firm surface, the blind subjects relied on the somatosensory system, whereas sighted subjects relied on the visual system. However, when eyes closed and on foam surface, similar behavior was found in both groups for all COP variables. In general blind subjects use their somatosensory system as the main sensory input to maintain PC.
... Balance is fundamental to humans of all ages, but becomes increasingly critical with aging (Winter, 1995). Among the studies showing an effect of age on balance, the obtained results were mainly related to a larger decline in postural stability under multitask conditions (e.g., Granacher et al., 2011;Huxhold et al., 2006; for reviews, see Boisgontier et al., 2013;Petrigna et al., 2021). ...
Article
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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.
... Balance is one of the basic abilities of the human body to accomplish complex motor movements [1,2]. The assessment of balance in sports performance analysis is also an essential research direction in sports science today. ...
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Balance ability is one of the important factors in measuring human physical fitness and a common index for evaluating sports performance. Its quality directly affects the coordination ability of human movements and plays an important role in human productive activities. In the field of sports, balance ability is an important indicator of athletes’ selection and training. How to objectively analyze balance performance becomes a problem for every non-professional sports enthusiast. Therefore, in this paper, we used a dataset of lower limb collected by inertial sensors to extract the feature parameters, then designed a RUS Boost classifier for unbalanced data whose basic classifier was SVM model to predict three classifications of balance degree, and, finally, evaluated the performance of the new classifier by comparing it with two basic classifiers (KNN, SVM). The result showed that the new classifier could be used to evaluate the balanced ability of lower limb, and performed higher than basic ones (RUS Boost: 72%; KNN: 60%; SVM: 44%). The results meant the established classification model could be used for and quantitative assessment of balance ability in initial screening and targeted training.
... Human balance control can be assessed biomechanically by the relationship between the body center of mass (CoM) and the base of support, measured by the Center of Pressure (CoP) position. As long as the CoM remains within the base of support a person remains stable without balance corrections in static situations (Winter, 1995). This approach was applied to dynamic situations, such as walking, with the extrapolated center of mass (XCoM) concept , which contains both CoM position and velocity (Pai and Patton, 1997) to describe the body's instantaneous stability in dynamic situations. ...
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Dynamic balance control during human walking can be described by the distance between the mediolateral (ML) extrapolated center of mass (XCoM) position and the base of support, the margin of stability (MoS). The ML center of mass (CoM) position during treadmill walking can be estimated based on kinematic data (marker-based method) and a combination of ground reaction forces and center of pressure positions (GRF-based method). Here, we compare a GRF-based method with a full-body marker-based method for estimating the ML CoM, ML XCoM and ML MoS. Fifteen healthy adults walked on a dual-belt treadmill at comfortable walking speed for three minutes. Kinetic and kinematic data were collected and analyzed using a GRF-based and marker-based method to compare the ML CoM, ML XCoM and ML MoS. High correlation coefficients (r > 0.98) and small differences (Root Mean Square Difference < 0.0072 m) in ML CoM and ML XCoM were found between the GRF-based and marker-based methods. The GRF-based method resulted in larger ML XCoM excursion (0.0118 ± 0.0074 m) and smaller ML MoS values (0.0062 ± 0.0028 m) than the marker-based method, but these differences were consistent across participants. In conclusion, the GRF-based method is a valid method to determine the ML CoM, XCoM and MoS. One should be aware of higher ML XCoM and smaller ML MoS values in the GRF-based method when comparing absolute values between studies. The GRF-based method strongly reduces measurement times and can be used to provide real-time CoM-CoP feedback during treadmill gait training.
... Normal postural stability enables fine-tuned dynamic actions and movement in everyday settings [1]. An intact postural system can adeptly compensate for intrinsic and external perturbations for an individual to safely and efficiently navigate the natural world [2]. ...
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Background and aim: The significant risk of falling in older adults 65 years or older presents a substantial problem for these individuals, their caretakers, and the health-care system at large. As the proportion of older adults in the United States is only expected to grow over the next few decades, a better understanding of physiological and cortical changes that make an older adult more susceptible to a fall is crucial. Prior studies have displayed differences in postural dynamics and stability in older adults with a fall history (FH) and those who are non-fallers (NF), suggesting surplus alterations that occur in some older adults (i.e., FH group) in addition to the natural aging process. Methods: The present study measured postural dynamics while the FH, NF, and young adult (YA) groups performed continuous postural maintenance. In addition, electroencephalography activity was recorded while participants performed upright postural stance to examine any group differences in cortical areas involved in postural control. Results: As expected, older participants (FH and NF) exhibited worse postural stability, as evidenced by increased excursion, compared to the YA group. Further, while NF and YA show increased alpha activity in occipital areas during the most demanding postural task (eyes closed), the FH group did not show any differences in occipital alpha power between postural tasks. Conclusions: As alpha activity reflects suppression of bottom-up processing and thus diversion of cognitive resources toward postural centers during more demanding postural maintenance, deficits in this regulatory function in the FH group are a possible impaired cortical mechanism putting these individuals at greater fall risk. Relevance for patients: Impaired inhibitory function in older adults may impact postural control and increase their risk of falling. Interventions that aim at addressing cortical processing deficits may improve postural stability and facilitate independent living in this population.
... The excursion in the anteroposterior (AP) and mediolateral (ML) directions, the total path length, and the 95 % confidence area ellipse were calculated and scaled to participant height for comparison. Total path length and ellipse area during quiet standing, which are a basis of COP movement, are representative of overall stability [35]. Dynamic balance was assessed in two variables: 1) the symmetry ratio (amputated/intact) of spatiotemporal parameters [36] and 2) gait variability quantified by the coefficient of variation (CV = SD/mean x 100) of spatiotemporal parameters [37]. ...
Article
Background: More than half of patients with lower-limb amputation who use socket prostheses experience at least one fall annually. These falls are primarily attributed to reduced proprioception which negatively affects balance. A promising alternative to socket prostheses are osseointegrated prostheses that involve direct fixation of the prosthetic limb to the residual limb through a bone-anchored implant, yet its effect on balance remains unknown. Research question: Do osseointegrated prostheses change static and dynamic balance, as well as patient reported measures of balance confidence, compared to a socket prosthesis? Methods: A sample of 10 patients with unilateral transfemoral amputation scheduled to undergo prosthesis osseointegration were enrolled (6 F/4 M, BMI: 26.7 ± 2.9 kg/m2, Age: 46.1 ± 6.3 years). Motion capture data during quiet standing (eyes opened and eyes closed) and overground walking at a self-selected speed, and the Activities-Specific Balance Confidence (ABC) scale, were collected before (with socket prosthesis) and 12-months following osseointegration. Postural sway via the center of pressure (COP), variability of spatiotemporal parameters, and ABC scores were compared using a repeated measures design before and after osseointegration. Results: Following prosthesis osseointegration, COP path length and 95 % confidence ellipse area were reduced during quiet standing (d = 0.75, P = 0.09; d = 0.52, P = 0.29, respectively) and the variability of step width and length were reduced during overground walking (d = 0.50, P = 0.06; d = 0.72, P = 0.06, respectively). Furthermore, patients reported significantly improved ABC scores with an osseointegrated prosthesis compared to a socket prosthesis (d = -1.36, P = 0.01). Significance: Improvements in postural sway, reductions in gait variability, and greater balance confidence indicate that osseointegrated prostheses improve balance for people with unilateral transfemoral amputation.
... A potential neglected factor in treatment protocols for PFP is postural control [5,[11][12][13][14]. Postural control involves a complex integration of visual, vestibular and somatosensory systems based on reflex actions occurring to maintain balance [15][16][17]. Considering people with PFP have impaired H-reflex [18,19], it is reasonable to expect that people with PFP will have alterations in other neuromuscular reflexes which may impact balance. Additionally, the presence of pain in people with PFP may also lead to impairments in postural control [20,21]. ...
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Background Growing evidence supports that exercise therapy is effective for patellofemoral pain (PFP) rehabilitation. Nevertheless, the improvements have been reported not to be sustained in the long term, suggesting that the current protocols may not comprehend all required functional factors to provide a consistent recovery. A potential neglected factor in treatment protocols for PFP is postural control. However, it is unclear whether this population presents balance impairments or the influence of postural control on pain and function during rehabilitation programmes. Objective To investigate whether (Q1) balance is impaired in people with PFP compared to controls, (Q2) conservative interventions are effective to improve balance in people with PFP, and (Q3) balance exercises are effective to improve pain and function in people with PFP. Data sources Medline, Embase, CINAHL, SPORTDiscus, Web of Science and Cochrane Library, supplemented by hand searching of reference lists, citations and relevant systematic reviews in the field. Methods A systematic review with meta-analysis was conducted according to the Cochrane recommendations and reported according to the PRISMA statement recommendations. We included cross-sectional studies comparing balance between people with and without PFP; and randomised controlled trials verifying the effect of conservative intervention on balance and the effect of balance intervention on pain and function in people with PFP. The risk of bias was assessed using the Epidemiological Appraisal Instrument for cross-sectional studies and the Physiotherapy Evidence Database scale for randomised controlled trials. Results From 15,436 records, 57 studies (Q1 = 28, Q2 = 23, Q3 = 14) met the eligibility criteria. Meta-analyses indicated that people with PFP have worse anteroposterior (very low grade evidence, standardised mean difference [SMD] = 1.03, 95% CI 0.40–1.66) and mediolateral (moderate grade evidence, SMD = 0.87, 95% CI 0.31–1.42) balance compared to controls. Moderate grade evidence indicated that overall balance is not affected in people with PFP (SMD = 0.38, 95% CI − 0.05–0.82). Low to very low grade evidence indicates that interventions are ineffective for mediolateral (SMD = 0.01, 95% CI − 0.51–0.53) and overall (SMD = 0.49, 95% CI − 0.14–1.11) balance improvements, and low grade evidence indicates that interventions are effective to improve anteroposterior balance (SMD = 0.64, 95% CI 0.04–1.23). Moderate to low grade evidence indicated that balance interventions are effective to reduce pain (SMD = 0.82, 95% CI 0.26–1.38) and improve function (SMD = 0.44, 95% CI 0.09–0.80) when measured using questionnaires; and very low grade evidence indicated no efficacy for function measured via functional tests (SMD = 0.73, 95% CI − 0.16–1.61). Conclusion People with PFP likely present balance deficits compared to asymptomatic people. There was insufficient evidence to support the efficacy of interventions to improve or modify balance in people with PFP. Also, there was insufficient evidence to support the efficacy of balance exercises to improve pain and function in people with PFP. Trial Registration The present systematic review was registered in PROSPERO (CRD42018091717).
... The COP at a given moment in time is the location of resultant vertical ground reaction force vector. The position of the COP under foot directly reflect the neural control of muscle force for body stabilization [17,18]. Recently, it has been shown that traditional linear COP characteristics (e.g. ...
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Background In recent years the use of sample entropy (SampEn) to evaluate the complexity of the locomotor system in human gait data has gained in popularity. However, it has been suggested that SampEn is sensitive to various input parameters and signal preprocessing methods. This study quantified the effects of different temporal and spatial normalization approaches and various lengths of the template vector (m) on SampEn calculations. The discriminatory ability of SampEn was studied by comparing two walking conditions. Methods Twenty-three participants (seven males, 55.7 ± 8.5 years, 165.7 ± 7.9 cm, 80.5 ± 16.7 kg) walked on a treadmill with preferred (Vpref) and maximum (Vmax) speed. Data were segmented and resampled (SEGM), resampled and spatially normalized (NORM), resampled and detrended (ZERO). Results For vertical ground reaction force (vGRF) and center of pressure in anterio-posterior direction (COPap), in both walking conditions, SampEn was generally sensitive to the vector length and not to the data processing, except for COPap in ZERO, m = 2, 4. For the COPml SampEn behaved oppositely, it was sensitive to preprocessing method and not to the m length. The regularity of COPap and vGRF in all processed signals increased in Vmax condition. For the COPml only two signals, WHOLE and ZERO, revealed increased complexity caused by more demanding walking conditions. Conclusions SampEn was able to discriminate between different walking conditions in all analyzed variables, but not in all signals. Depending on evaluated variable, SampEn was susceptible in different way for the m level and processing method. Hence, these should be checked and selected for each variable independently. For future studies evaluating influence of walking velocity on COP and vGRF regularity during treadmill walking it is advised to use raw time series. Furthermore, to maintain template vector which represents biological relevance it is advised to detect highest frequencies present in analyzed signals and evaluate minimal time interval which can reflect change caused by response of a neuromuscular system. During evaluating treadmill walking measured with 100 Hz sampling frequency it is recommended to adopt m from 6 to 10, when average stride time is up to about 1 s.
... The observed lack of arm movement effects on OLS performance can most likely be explained by "ceiling effects". Precisely, this task is representative of steady-state static balance control, where the center of mass can relatively easily be held over the base of support [15]. Thus, arm movements have no additional positive influence on stance duration. ...
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Objective Studies have shown that balance performance is better in gymnasts compared to age-/sex-matched controls and further studies revealed superior performance when arms were free to move during assessment of balance. However, it is unknown whether free arm movement during balance testing differentially affects balance performance with respect to sports expertise (i.e., gymnasts are less affected than age-/sex-matched controls). Therefore, we investigated the effect of arm movement on balance performance in young female gymnasts compared to age-/sex-matched controls while performing balance tasks with various difficulty levels. Results In both samples, balance performance (except for the timed one-legged stance) was significantly better during free compared to restricted arm movement conditions and this was especially observed in the highest task difficulty condition of the 3-m beam walking backward test. These findings revealed that balance performance is positively affected by free arm movements, but this does not seem to be additionally influenced by the achieved expertise level in young gymnasts.
... The study of the control mechanism in charge of the equilibrium of human bipedal posture has attracted the attention of numerous researchers Winter (1995), Vette et al. (2010b), Fok et al. (2021a). Noting that the studies about postural stability are essential to improve the understanding of self-balance mechanisms of the human body. ...
Conference Paper
In this work, we investigate the human quiet stance regulation problem using a single-link inverted pendulum model in the sagittal plane via the ankle joint's passive/active torques' actions. The active torque consists of ankle muscle contractions that are activated by the delayed action of the Central Nervous System (neural controller). The passive torque is related to the intrinsic mechanical properties of the muscle-tendon-ligament component. The failure of the human quiet stance is then directly related to the failure of one or both types of torques. We propose to model the neural controller as a delayed Proportional-Derivative-Acceleration controller acting on the ankle joint's angular position. By using the multiplicity-induced-dominancy property, the critical time delay of the motor control and the critical ankle-joint stiffness are both investigated.
... Thus, parameter estimates for each repetition were based on segments of 110 seconds. Mechanisms regulating balance in AP and medio-lateral direction differ [53]; therefore, directional measures were used to quantify balance in addition to measures irrespective of the direction on the 2D plane (global). The trajectory of the COP was described by the mean absolute displacement from the mean COP (AP, medio-lateral, and global), and by corresponding velocities, graphically represented in Multimedia Appendix 2 [54]. ...
Article
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Ewing sarcoma (EwS) is characterized by EWSR1-ETS fusion transcription factors converting polymorphic GGAA microsatellites (mSats) into potent neo-enhancers. Although the paucity of additional mutations makes EwS a genuine model to study principles of cooperation between dominant fusion oncogenes and neo-enhancers, this is impeded by the limited number of well-characterized models. Here we present the Ewing Sarcoma Cell Line Atlas (ESCLA), comprising whole-genome, DNA methylation, transcriptome, proteome, and chromatin immunoprecipitation sequencing (ChIP-seq) data of 18 cell lines with inducible EWSR1-ETS knockdown. The ESCLA shows hundreds of EWSR1-ETS-targets, the nature of EWSR1-ETS-preferred GGAA mSats, and putative indirect modes of EWSR1-ETS-mediated gene regulation, converging in the duality of a specific but plastic EwS signature. We identify heterogeneously regulated EWSR1-ETS-targets as potential prognostic EwS biomarkers. Our freely available ESCLA (http://r2platform.com/escla/) is a rich resource for EwS research and highlights the power of comprehensive datasets to unravel principles of heterogeneous gene regulation by chimeric transcription factors.
... To quantify postural stability, usually, the Center of Pressure (CoP) is calculated using a force plate (Rhea et al., 2014). During standing, the CoP is the point representing the weighted average of the sum of the vertical ground reaction forces exerted by both feet onto the force plate (Winter, 1995). Typically, lower CoP displacements are referred to as a more stable stance (Palmieri et al., 2002). ...
Article
The effect of different human body part stimuli in mental rotation tasks (MRTs) on postural stability was investigated in two dual-task experiments. There were significant differences within egocentric MRTs (Experiment 1, N = 46): Hand and foot stimuli tended to cause more body sway than whole-body figures and showed increased body sway for higher rotation angles in the MRTs. In object-based MRTs (Experiment 2, N = 109) different stimuli did not evoke different levels of body sway, but higher rotation angles led to higher body sway. Both experiments showed a stabilizing effect of MRTs compared to the control condition. Exploratorily analyses identified reaction time in MRTs as a significant predictor of body sway. The results suggest a heterogeneous impact of mental rotation on postural stability.
... The foot placement strategy modulates the relation between the COM and BOS at relatively low actuation costs, because it only requires movement of the swing leg. Consequently, foot placement is the dominant mechanism to maintain balance in the mediolateral (ML) direction during walking in healthy subjects [13,14]. Literature suggests that ML foot placement is based on COM kinematics [15][16][17][18][19]. ...
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Background: Impaired balance during walking is a common problem in people with incomplete spinal cord injury (iSCI). To improve walking capacity, it is crucial to characterize balance control and how it is affected in this population. The foot placement strategy, a dominant mechanism to maintain balance in the mediolateral (ML) direction during walking, can be affected in people with iSCI due to impaired sensorimotor control. This study aimed to determine if the ML foot placement strategy is impaired in people with iSCI compared to healthy controls. Methods: People with iSCI (n = 28) and healthy controls (n = 19) performed a two-minute walk test at a self-paced walking speed on an instrumented treadmill. Healthy controls performed one extra test at a fixed speed set at 50% of their preferred speed. To study the foot placement strategy of a participant, linear regression was used to predict the ML foot placement based on the ML center of mass position and velocity. The accuracy of the foot placement strategy was evaluated by the root mean square error between the predicted and actual foot placements and was referred to as foot placement deviation. Independent t-tests were performed to compare foot placement deviation of people with iSCI versus healthy controls walking at two different walking speeds. Results: Foot placement deviation was significantly higher in people with iSCI compared to healthy controls independent of walking speed. Participants with iSCI walking in the self-paced condition exhibited 0.40 cm (51%) and 0.33 cm (38%) higher foot placement deviation compared to healthy controls walking in the self-paced and the fixed-speed 50% condition, respectively. Conclusions: Higher foot placement deviation in people with iSCI indicates an impaired ML foot placement strategy in individuals with iSCI compared to healthy controls.
... It would not be an exaggeration to say that the practice of most of the techniques in Karate is actually oriented towards concentrating power at a precise time and in a specific location. However, according to a circle of Bulgarian traumatologists, strength, in a traumatic sense, can also be the ability of the athlete through muscle contraction to create a counteraction to the externally applied kinetic energy to certain units of the musculoskeletal system or the body as a whole (Takov, Tivchev, 1996). In this sense, muscle strength will have a protective role not only in relation to the externally directed kinetic energy imparted by another moving body -an object, another athlete but also to the forces that arise inside the elements of the musculoskeletal system during movements as a component of the combat load and the subsequent risk of injuries. ...
Conference Paper
Introduction. As a sport to which more and more young people are turning to, Karate, and especially its most prominent martial art associated injuries, is gaining more and more importance in our present. Unfortunately, little is known about the kinematic characteristics while performing Mae-Geri front kick Shotokan Karate. Special emphasis will be placed on the goal of this fighting technique - more skillful control and effective use of body segments by well-trained fighters will allow maximum acceleration and reaching the adversary both faster and yet-in controlled fashion, without the risk of the injury of both participants in the match The aim of this study will be to compare the kinematic characteristics of the lower limbs when performing a specific fighting technique (Mae-Geri kick) by Karate athletes from two different groups according to rank/sports experience, in relation to the sustained traumatism. Methods and methodology of the study. For this purpose, a kinematic analysis was performed by video registration (with a digital camera Casio ZR 200 with a frame rate of 120 frames/sec) and subsequent image processing of the video to measure kinematic parameters with a software product (SkilSpector). In our initial experiment, 18 of the 22 Karate fighters belonged to two distinct groups (9 black belts from I and II dan, and 9 from 1 to 3 kyu). Results and analysis. According to our comparative analysis, we can assume that the Bulgarian Karate athletes are: both on equal grounds based on kinematic characteristics of the Mae-Geri front kick execution, yet also leading their international counterparts in terms of lower frequency of traumatic injuries in key regions of the body and types of injuries. In turn, the resulting increase in injuries in the group of high-performance athletes (1-3) kyu is mainly explained by the increase in self-confidence, executing riskier attacks with higher chances of interception and resulting in injury by their adversary, allowing our Bulgarian elite Karate fighters to stand out (from I dan and up) for which this type of injury is mostly exception.
... Technical skills are essential in distinguishing players and could determine their level (2). Nevertheless, basketball requires the players with or without the ball to execute movements such as passing and receiving the ball while balancing on one leg, looking in the same or the opposite direction, to have constant visual contact with their teammates and opponents during physical contact are required to shoot (3). Basketball players change rules, jump, and run, exerting a great deal of overload on the lower limbs (4,5). ...
... Balance control is an essential component of many daily activities and sports. Balance has been previously described as the body position dynamics that lessen the danger of or avoid the act of falling [81]. However, balance control can deteriorate across the lifespan or after injuries, leading to slow gait [54], postural instability [35], and fall risk [77]. ...
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Dynamic balance is an essential skill for the human upright gait; therefore, regular balance training can improve postural control and reduce the risk of injury. Even slight variations in walking conditions like height or ground conditions can significantly impact walking performance. Virtual reality is used as a helpful tool to simulate such challenging situations. However, there is no agreement on design strategies for balance training in virtual reality under stressful environmental conditions such as height exposure. We investigate how two different training strategies, imitation learning, and gamified learning, can help dynamic balance control performance across different stress conditions. Moreover, we evaluate the stress response as indexed by peripheral physiological measures of stress, perceived workload, and user experience. Both approaches were tested against a baseline of no instructions and against each other. Thereby, we show that a learning-by-imitation approach immediately helps dynamic balance control, decreases stress, improves attention focus, and diminishes perceived workload. A gamified approach can lead to users being overwhelmed by the additional task. Finally, we discuss how our approaches could be adapted for balance training and applied to injury rehabilitation and prevention.
... In the standing position, individuals have to control their balance, because they sway at all time (Winter 1995;Ivanenko and Gurfinkel 2018). In the literature, postural control is usually considered as the primary task of the brain as individuals need to avoid falling (Woollacott and Shumway-Cook 2002;Swan et al. 2004). ...
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The literature on postural control highlights that task performance should be worse in challenging dual tasks than in a single task, because the brain has limited attentional resources. Instead, in the context of visual tasks, we assumed that (i) performance in a visual search task should be better when standing than when sitting and (ii) when standing, postural control should be better when searching than performing the control task. 32 and 16 young adults participated in studies 1 and 2, respectively. They performed three visual tasks (searching to locate targets, free-viewing and fixating a stationary cross) displayed in small images (visual angle: 22°) either when standing or when sitting. Task performance, eye, head, upper back, lower back and center of pressure displacements were recorded. In both studies, task performance in searching was as good (and clearly not worse) when standing as when sitting. Sway magnitude was smaller during the search task (vs. other tasks) when standing but not when sitting. Hence, only when standing, postural control was adapted to perform the challenging search task. When exploring images, and especially so in the search task, participants rotated their head instead of their eyes as if they used an eye-centered strategy. Remarkably in Study 2, head rotation was greater when sitting than when standing. Overall, we consider that variability in postural control was not detrimental but instead useful to facilitate visual task performance. When sitting, this variability may be lacking, thus requiring compensatory movements.
... Asterisks (*) indicate significant difference lateral side during the early-to-mid swing phase of the swing leg, this lateral pulling force appeared to elevate a speed of the CoM motion toward the lateral side (Fig. 5A), which might augment the body's momentum that the swing leg had to regulate after the leg was landed on the belt (i.e., stance phase). Thus, it is possible that the central nervous system (CNS) may need to generate additional torques by enhancing the muscle activation of the hip abductors and adductors, which are crucial muscle groups for lateral balance control during walking (Winter 1995), to counteract the increased mediolateral momentum and stabilize the standing leg. Specifically, the hip adductor muscles are the antagonists to gluteus medius (i.e., abductors), and enhanced co-activation of those muscle pairs might improve the mechanical impedance of hip joint (Hogan 1984), contributing to greater stability of the standing leg in response to the increased mediolateral momentum; see Fig. 2. In addition, the increased speed of the CoM toward the lateral side during the swing phase of the swing leg might also increase the stretching of hip adductors of the contralateral standing leg. ...
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The purpose of this study was to determine whether the control of lateral balance can be improved by applying repeated lateral perturbation force to the pelvis during swing versus stance phase walking in individuals with spinal cord injury (SCI). Fourteen individuals with incomplete SCI were recruited in this study. Each participant visited the lab once and was tested in two experimental sessions that consisted of (1) treadmill walking with bilateral perturbation force applied to the pelvis in the lateral direction during either swing or stance phase of each leg and (2) overground walking pre- and post-treadmill walking. Applying the swing-phase perturbation during walking induced a greater increase in the muscle activation of hip abductors and ankle plantar flexors and a greater improvement in lateral balance control after the removal of perturbation force, in comparison to the results of the stance-phase perturbation condition (P ≤ 0.03). Participants also exhibited a greater reduction in overground step width and a greater improvement in overground walking speed after a session of treadmill walking practice with the swing-phase perturbation, compared with the result of the stance-phase perturbation (P = 0.01). These findings suggest that applying perturbation force to the pelvis during the swing phase of gait while walking may enhance muscle activities of hip abductors and improve lateral balance control in individuals with SCI. A walking practice with the swing-phase pelvis perturbation can be used as a rehabilitation approach to improve the control of lateral balance during walking in people with SCI.
... However, during deeper squat (i.e., 60° knee flexion), the normal DKV group was able to switch to hip abduction. When the athlete has poor control of the hip, particularly the gluteus medius muscle, the loaded hip tends to shift into adduction (28) and further cause the femur to rotate internally and the tibia to abduct (i.e., valgus position) (7,29). ...
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Introduction: Introduction: Knee valgus which also known as dynamic knee valgus (DKV), is frequently linked to non-contact lower-limb injuries, especially in females. This retrospective study aims to compare the kinematic variables of lower limb joints in physically active females with normal versus excessive DKV during single leg squat (SLS) at 45° and 60° knee flexion. Methods: Based on the outcomes of drop vertical jump screening test, 34 females were recruited and divided into two groups (i.e., normal and excessive DKV). Participants performed SLS at 45° and 60° knee flexion with three-dimensional motion capture and analysis. The kinematic variables of lower limb joints at both knee flexion of SLS were compared across groups using independent T-test. Results: During 45° SLS with the dominant limb, the normal DKV group performed significantly greater hip adduction angle (4.49±3.25°, t(32) = 2.371, p= 0.024) than the excessive DKV group (1.426±4.23°). During 60° SLS with the dominant limb, the normal DKV group showed knee adduction (0.223±0.07°, t(16.048) = 10.707, p=0.001) while the excessive DKV group showed knee abduction (-4.478±1.81°). Conclusion: Females with excessive DKV showed significantly different lower limb kinematics and motion control strategy compared to females with normal range of DKV. The findings highlighted the importance of DKV screening among physically active females, and the rationale for prescribing individualized exercise intervention to prevent lower limb non-contact injuries.
... Here, we define the body position for a single step (z Bn ; Fig 1C) as the midpoint between the two feet [1,83]. This definition of z Bn is strongly correlated to the lateral center-of-mass (CoM) position at each heel strike ( [84]; S1 Text). By selecting appropriate foot placements, {z L , z R }, humans can regulate both their body position and step width,{z Bn , w n } [1], via: ...
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To successfully traverse their environment, humans often perform maneuvers to achieve desired task goals while simultaneously maintaining balance. Humans accomplish these tasks primarily by modulating their foot placements. As humans are more unstable laterally, we must better understand how humans modulate lateral foot placement. We previously developed a theoretical framework and corresponding computational models to describe how humans regulate lateral stepping during straight-ahead continuous walking. We identified goal functions for step width and lateral body position that define the walking task and determine the set of all possible task solutions as Goal Equivalent Manifolds (GEMs). Here, we used this framework to determine if humans can regulate lateral stepping during non -steady-state lateral maneuvers by minimizing errors consistent with these goal functions. Twenty young healthy adults each performed four lateral lane-change maneuvers in a virtual reality environment. Extending our general lateral stepping regulation framework, we first re-examined the requirements of such transient walking tasks. Doing so yielded new theoretical predictions regarding how steps during any such maneuver should be regulated to minimize error costs, consistent with the goals required at each step and with how these costs are adapted at each step during the maneuver. Humans performed the experimental lateral maneuvers in a manner consistent with our theoretical predictions. Furthermore, their stepping behavior was well modeled by allowing the parameters of our previous lateral stepping models to adapt from step to step. To our knowledge, our results are the first to demonstrate humans might use evolving cost landscapes in real time to perform such an adaptive motor task and, furthermore, that such adaptation can occur quickly–over only one step. Thus, the predictive capabilities of our general stepping regulation framework extend to a much greater range of walking tasks beyond just normal, straight-ahead walking.
... Therefore, it is important for a physiotherapist to evaluate the APAs quantitatively in functional tasks, especially when performed by subjects with PD. APAs have been examined in the step motion at gait initiation with a shift of the center of pressure (COP) to the stance limb side (Crenna and Frigo, 1991;Winter, 1995) and lumbar accelerations (Onuma et al., 2021a(Onuma et al., , 2021bRocchi, Mancini, Chiari, and Cappello, 2006). Previous studies in individuals with PD reported decreased posterior lateral displacement of the COP as well as lumbar acceleration toward the stance side (Mancini et al., 2009;Schlenstedt et al., 2018). ...
Article
Objective To investigate a smartphone-enabled quantitative evaluation of anticipatory postural adjustments (APA) during one-leg stance (OLS) movements among individuals with Parkinson’s disease (PD). Methods This cross-sectional study included 10 young controls, 10 older individuals, and 13 individuals with PD. A smartphone and accelerometer were attached to the participants’ lower back (L5), and the movements of the lower back toward the stance side during OLS were measured. For acceleration, the time to the peak value in the stance direction (peak latency [PL]) and the amount of displacement to the peak value in the stance direction (peak magnitude [PM]) were analyzed as APA characteristics. Additionally, the measured PL was divided by the PM for each group to obtain the APA ratio (APAr) as a new index. Results Individuals with PD showed a delayed PL and decreased PM (vs. young controls: p = .002 for PL, p < .001 for PM) (vs. older individuals: p = .022 for PL, p = .001 for PM). The APAr clustered the young controls, older individuals, and individuals with PD. According to the receiver operating characteristic curve the APAr value was 0.95, and individuals in the PD group were identified (i.e. area under the curve: 0.98; sensitivity: 85.0%; specificity: 100%). Moreover the APAr was correlated with severity and balance ability in individuals with PD (p = .015 for NFOG-Q, p = .028 for UPDRS, p = .036 for TUG, p = .015 for Mini-BESTest, p = .018 for OLS time). Conclusions This smartphone-based evaluation using the APAr index was reflective of disease severity and decreased balance ability among individuals with PD. The facilitation of this measurement can help clinicians and physiotherapists quantitatively evaluate the APA of individuals with PD at laboratories and hospitals as well as in home environments.
... This effect discrepancy between sacrum and sternum LDE may be due to the proximity of the former sensor to the CoM, which despite its greater excursion when carrying a weapon (Birrell and Haslam 2008) or loaded, is more tightly controlled through increased stiffness (Holt et al. 2003), for example, in order to maintain stability (Best et al. 2019). The latter also extends to explain similar findings in the LDE directional analyses and may further supports the notion of the CoM as the main controlled variable in human motion (Winter 1995). A study exploring the effects on stability (LDE) of a backpack carrying an in-or out-of-phase inverted pendulum found a reduced motion of the CoM and increased stability in both conditions compared to a fixed pendulum (Best et al. 2019). ...
Article
Gait stability in soldiers can be affected by task constraints that may lead to injuries. This study determined the effects of weapon handling and speed on gait stability in seventeen soldiers walking on a treadmill with and without a replica weapon at self-selected (SS), 3.5 km h⁻¹, 5.5 kmh⁻¹, and 6.5 km h⁻¹ while carrying a 23-kg load. Local dynamic stability was measured using accelerometry at the sacrum (LDESAC) and sternum (LDESTR). No significant weapon and speed interaction were found. A significant effect of speed for the LDESAC, and a significant effect of speed and weapon for the LDESTR were found. Per plane analyses showed that the weapon effect was consistent across all directions for the LDESTR but not for LDESAC. Weapon handling increased trunk but did not affect pelvis stability. Speed decreased stability when walking slower than SS and increased when faster. These findings can inform injury prevention strategies in the military.
... Additionally, the effects of mental fatigue were magnified during more challenging postural control tasks, such as when both the eyes were closed and the support surface was unstable. In these sensory conditions, maintaining balance becomes more challenging because visual and somatosensory information (i.e., crucial sensory information for balance control) are removed or altered, resulting in increased postural sway (Winter 1995;Marigold et al. 2005;Roerdink et al. 2006;Varas-Diaz et al. 2020). These findings indicate that mental fatigue may result in greater balance control detriments when sensory information is limited. ...
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The relationship between cognitive demands and postural control is controversial. Mental fatigue paradigms investigate the attentional requirements of postural control by assessing balance after a prolonged cognitive task. However, a majority of mental fatigue research has focused on cognition and sports performance, leaving balance relatively underexamined. The purpose of this paper was to systematically review the existing literature on mental fatigue and balance control. We conducted a comprehensive search on PubMed and Web of Science databases for studies comparing balance performance pre- to post-mental fatigue or between a mental fatigue and control group. The literature search resulted in ten relevant studies including both volitional (n = 7) and reactive (n = 3) balance measures. Mental fatigue was induced by various cognitive tasks which were completed for 20–90 min prior to balance assessment. Mental fatigue affected both volitional and reactive balance, resulting in increased postural sway, decreased accuracy on volitional tasks, delayed responses to perturbations, and less effective balance recovery responses. These effects could have been mediated by the depletion of attentional resources or impaired sensorimotor perception which delayed appropriate balance-correcting responses. However, the current literature is limited by the number of studies and heterogeneous mental fatigue induction methods. Future studies are needed to confirm these postulations and examine the effects of mental fatigue on different populations and postural tasks. This line of research could be clinically relevant to improve safety in occupational settings where individuals complete extremely long durations of cognitive tasks and for the development of effective fall-assessment and fall-prevention paradigms.
Article
IntroductionOptimal trunk control relies on adequate musculoskeletal, motor, and somatosensory systems that are often affected in people with Alzheimer’s disease (AD). Therefore, the aim of this study was to compare trunk control between people with AD and healthy older adults, and investigate the relationship between trunk control and balance, gait, functional mobility, and fear of falling in people with AD.Methods The study was completed with 35 people with AD and 33 healthy older adults with matching age and gender. Trunk control was evaluated with Trunk Impairment Scale (TIS); balance with Berg Balance Scale (BBS), Functional Reach Test (FRT), One-Leg Standing Test (OLST) and Five-Repeat Sit-and-Stand Test (5STS); gait with Dynamic Gait Index (DGI); functional mobility with Timed Up and Go (TUG) Test; fear of falling with Falls Efficacy Scale-International (FES-I).ResultsBBS, FRT, OLST, and DGI scores were lower and 5STS and TUG Test scores were higher in people with AD compared to healthy older adults (p < 0.05). There was no difference in FES-I score between people with AD and healthy older adults (p > 0.05). TIS was associated with BBS, FRT, OLST, 5STS, DGI, TUG Test, and FES-I (r between − 0.341 and 0.738; p < 0.05 for all).Conclusion Trunk control is affected and related with balance, gait, functional mobility, and fear of falling in people with AD. For this reason, we think that trunk control should be evaluated in the early period, and applications for trunk control should be included in rehabilitation approaches in order to improve balance, gait, functional mobility, and reduce fear of falling.
Article
Perturbations in sitting posture, represented by the center of mass (COM) of the upper body, provide critical information for analyzing balance control. While the COM is generally measured by an optical motion capture system, it is not practical. In a previous study, we proposed a method to estimate the COM during standing from a force platform under the feet based on inverted pendulum models. However, it is unclear whether the technique can be applied to the sitting posture. Furthermore, it is also unclear whether two force platforms under the buttocks and the feet would be required if it could be applied. The purpose of this study is to estimate the upper body COM of a subject sitting on a backless seat from one or two force platforms and to validate the estimation accuracy by comparing the results to those from an optical motion capture system. For considering forces acting from the lower limbs, it is necessary to adopt a mechanical model that includes the lower limbs and to use a force platform under the feet in addition to those on the seat. We compared estimation accuracy between the models with and without lower limbs in three conditions: rest sitting, voluntary sway, and seat sway with an electric cart. The result indicated a clear difference between the two models, and the model considering lower limbs had high accuracy. Since the present method is a practical and highly accurate method of sitting posture, it may be applied in the analysis of low back pain and motion sickness.
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Virtual time-to-contact (VTC) is a promising approach for investigating postural balance control. However, current VTC calculation approaches are limited as they (1) cannot be used to evaluate directional components of balance, and (2) only assess a single, temporal aspect of balance control. This study introduces a new approach for VTC calculation, namely directional VTC, expanding VTC to assess temporal, spatial, and control aspects of balance. Three case studies were conducted across varying populations and conditions as a proof-of-concept of the presented method. The first study examined quiet stance on a firm surface in people with Parkinson's disease (PD; n = 10) in comparison to their healthy peers (n = 10). The second and third studies assessed balance control of healthy individuals under challenging environments. Ten healthy individuals participated in standing tasks on compliant ground surfaces, while another ten on oscillatory ground surfaces, all simulated by a dual-axis robotic platform. Preliminary results not only provided a closer look at balance control with multiple aspects, including temporal, spatial, and control aspects, but also showed how different aspects of balance changed due to neurological diseases (Case Study I) or challenging standing grounds (Case Studies II and III). This study advances our understanding of posture biomechanics and its clinical applications.
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Aging is associated with neurodegeneration and a loss of muscle function, especially in lower-limb muscles. While caffeine may augment muscle force generation through multiple effects on the central nervous system, no studies have yet compared the effects of caffeine on force-generating capacity between younger and older men, who might respond differently due to age-related changes in the structures on which caffeine acts. In a double-blind, controlled trial, 22 younger (25 ± 5 years) and 21 older (68 ± 6 years) men were tested for isometric plantarflexor torque on two separate days (2–7 days apart) before and 60 min after ingesting 3 mg/kg (∼2 cups of coffee) of caffeine or placebo. No effects of caffeine ingestion on peak torque or rate of torque development were detected in either older or younger men. Therefore, 3 mg/kg of caffeine may not acutely counteract age-related decreases in force capacity of the functionally important plantarflexor muscles.
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In this study, we investigated trainees’ adaptation by conducting static balance training in a tandem standing posture. The horizontal tensile force loads in the front, back, left, and right directions were applied using pneumatic artificial muscles. We analyzed the adaptation that occurred during training by changing the direction of the horizontal tensile load on the lumbar region according to the tendency of the trainee. We conducted the experiments using the following protocol. Ten trainees participated in the experiment. In Phase 1, we applied loads in four directions the same number of times in random order to investigate the weak direction in the balance of each trainee. In Phase 2, we measured five trainees in each group: Group 1 was trained in the same way as Phase 1, and Group 2 was intensively trained in two directions in which the balance found in Phase 1 was difficult to maintain. In Phase 3, we performed the same experiment as in Phase 1. We analyzed the adaptation of the trainees using the margin of stability (MoS), a balance evaluation index. We compared the experimental results of Phases 1 and 3. In Group 1, the tendency for improvement in balance was unclear. On the other hand, the balance index in Group 2 improved in four out of five trainees in both the front-back and left-right directions. These results suggest that the training method concentrating on the weak direction could provide a clear directionality to the training effect.
Article
Application of anodal trans-cranial direct current stimulation (a-tDCS) versus cathodal tDCS (c-tDCS) can influence the physiological results of tDCS intervention on postural control and balance in patients or healthy adults. According to the evidence, some studies demonstrated that postural control or balance is facilitated by the application of the a-tDCS more than the c-tDCS. On the other hand, some studies indicated that there were no significant differences between a-tDCS and c-tDCS. In contrast, other studies have shown a more significant effect of c-tDCS than a-tDCS on postural control and balance. This study aimed to systematically review the studies which investigated the effectiveness of a-tDCS and c-tDCS intervention on postural control and balance. The search was performed from databases in Google Scholar, PubMed, Elsevier, Medline, Ovid, and Science Direct with the keywords of balance, balance test, postural control, postural stability, postural sway, posture, postural balance, trans-cranial direct current stimulation, tDCS, neuromodulator, neurostimulation, tDCS, a-tDCS or anodal tDCS, c-tDCS or cathodal tDCS from 2000 to 2022. The results confirmed that the study population was a key factor in determining the study's findings. Data meta-analysis showed no significant differences between active tDCS and sham tDCS on postural control in healthy individuals (P > 0.05). In addition, the results indicated the efficacy of both a-tDCS over the affected motor cortex (M1) and c-tDCS over unaffected M1 as compared to sham tDCS on postural improvement in patients with stroke (P < 0.05), however, there were no differences between the two techniques on posture and balance in these patients.
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Identification of pathological gait is the most direct application of gait analysis. The purpose of the study is to investigate the dynamics of human walking over a complete gait cycle. Level-walking experiments were performed by two-dimensional (2D) motion analysis using a digital video camera (Sony, 25 Hz) and two force plates. Kinematic data were obtained from the trajectories of 7 reflective markers using SkillSpector software (ver. 1.2.4). MATLAB software (ver. 8.1) has been adopted in this work to obtain Pedotti diagram and for inverse dynamics computations. Digital low pass Butterworth filter with zero phase-shift and cutoff frequency of 4.5 Hz was used. Joints' angular displacement, forces, and moments were obtained during gait cycle. The study was made on fourteen healthy volunteers (10 males and 4 females); a male with cerebral palsy, and an old female underwent unilateral knee arthroplasty. These data can be used as standard measures in pathology studies, as input to theoretical joint models, and as input to mechanical joint simulators.
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It has been shown that when humans lean in various directions, the central nervous system (CNS) recruits different motoneuron pools for task completion; common units that are active during different leaning directions, and unique units that are active in only one leaning direction. We used high-density surface electromyography (HD-sEMG) to examine if motor unit (MU) firing behaviour was dependent on leaning direction, muscle (medial and lateral gastrocnemius; soleus), limits of stability, or whether a MU is considered common or unique. Fourteen healthy participants stood on a force platform and maintained their center of pressure in five different leaning directions. HD-sEMG recordings were decomposed into MU action potentials and the average firing rate (AFR), coefficient of variation (CoV ISI ) and firing intermittency were calculated on the MU spike trains. During the leaning directions that demanded larger force production, both unique and common units had higher firing rates (F = 31.31, p < 0.0001). However, the unique units achieved higher firing rates compared to the common units (mean estimate difference = 3.48 Hz, p < 0.0001). The CoV ISI increased across directions for the unique units but not for the common units (F = 23.65. p < 0.0001). Finally, intermittent activation of MUs was dependent on the leaning direction (F = 11.15, p < 0.0001), with less intermittent activity occurring during diagonal and forward-leaning directions. These results provide evidence that the CNS can preferentially control separate motoneuron pools within the ankle plantarflexors during voluntary leaning tasks for the maintenance of standing balance.
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In quiet standing with feet side by side the motor control sites were investigated in the anterior/posterior (A/P) and medial/lateral (M/L) directions. In the A/P direction the left and right limb center of pressure (COP) changes were quite synchronized while in the M/L direction they were antiphase. In the A/P direction the total body net COP changes were virtually 100% controlled by the right and left COP changes. However, in the M/L direction the right and left COP changes contributed almost nothing to the net COP changes. Rather, the M/L postural control was dominated by a loading/unloading response. Thus the ankle strategy in postural control in this natural standing condition is limited to the A/P direction. Based on a closed link kinematic chain we would postulate this M/L loading/unloading control to be under the control of the hip abductors/adductors.
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Research to date has shown that the large inertial load of the head-arms-trunk (HAT) is controlled within a few degrees in both the frontal and sagittal planes over the gait cycle. Also, there are limited reports of major attenuation of the head anteroposterior () acceleration in spite of large inertial perturbations at the hips during weight bearing. These findings prompted further investigations into the kinematics and the active control of upper body balance. The first experiment found that the head acceleration was significantly attenuated (0.48 m s−2) compared with the hip (1.91 m s−2) and that the attenuation was gradual from the lumbar level to the neck. A second experiment recorded the EMG profiles of the paraspinal muscles at every second vertebrae level from C7 to L4. The results demonstrated a ‘top-down’ anticipatory control which stabilized the head first, then the cervical level, the thoracic level, and finally the lumbar level. Because of the lack of stretching of these paraspinal muscles and the incorrect polarity of the otolith acceleration, it was argued that this balance control was anticipatory and not reflex.
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Movement is performed against a background of subtle postural adjustments that counteract destabilizing forces imposed by the movement. Despite the importance of these postural adjustments to the safe and efficient performance of movement, little is known about the properties of these postural accompaniments. The purpose of this article is twofold. First, it provides a review of properties of postural adjustments that accompany a variety of limb and trunk movements. Second, a schema for the coordination of posture and movement is proposed. This schema suggests that a central nervous system model of body dynamics is essential to anticipatory control of posture during movement.
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This study examines the roles of somatosensory and vestibular information in the coordination of postural responses. The role of somatosensory information was examined by comparing postural responses of healthy control subjects prior to and following somatosensory loss due to hypoxic anesthesia of the feet and ankles. The role of vestibular information was evaluated by comparing the postural responses of control subjects and patients with bilateral vestibular loss. Postural responses were quantified by measuring 1) spatial and temporal characteristics of leg and trunk EMG activation; 2) ankle, knee, and hip joint kinematics, and 3) surface forces in response to anterior and posterior surface translations under different visual and surface conditions. Results showed that neither vestibular nor somatosensory loss resulted in delayed or disorganized postural responses. However, both types of sensory deficits altered the type of postural response selected under a given set of conditions. Somatosensory loss resulted in an increased hip strategy for postural correction, similar to the movement strategy used by control subjects while standing across a shortened surface. Vestibular loss resulted in a normal ankle strategy but lack of a hip strategy, even when required for the task of maintaining equilibrium on a shortened surface. Neither somatosensory nor vestibular loss resulted in difficulty in utilizing remaining sensory information for orientation during quiet stance. These results support the hypothesis that cutaneous and joint somatosensory information from the feet and ankles may play an important role in assuring that the form of postural movements are appropriate for the current biomechanical constraints of the surface and/or foot. The results also suggest that vestibular information is necessary in controlling equilibrium in a task requiring use of the hip strategy. Thus, both somatosensory and vestibular sensory information play important roles in the selection of postural movement strategies appropriate for their environmental contexts.
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The effect of the direction of unexpected horizontal perturbations of stance on the organization of automatic postural responses was studied in human subjects. We recorded EMG activity from eight proximal and distal muscles acting on joints of the legs and hip known to be involved in postural corrections, while subjects stood on an hydraulic platform. Postural responses to horizontal motion of the platform in 16 different directions were recorded. The amplitude of the EMG responses of each muscle studied varied continuously as perturbation direction was changed. The directions for which an individual muscle showed measurable EMG activity were termed the muscle's "angular range of activation". There were several differences in the response characteristics of the proximo-axial muscles as opposed to the distal ones. Angular ranges of activity of the distal muscles were unipolar and encompassed a range of less than 180 degrees. These muscles responded with relatively constant onset latencies when they were active. Proximo-axial muscles, acting on the upper leg and hip showed larger angular ranges of activation with bimodal amplitude distributions and/or onset latency shifts as perturbation direction changed. While there were indications of constant temporal relationships between muscles involved in responses to perturbations around the sagittal plane, the onset latency relationships for other directions and the response amplitude relationships for all directions varied continuously as perturbation direction was changed. Responses were discrete in that for any particular perturbation direction there appeared to be a single unique response. Thus, while the present results do not refute the hypothesis that automatic postural responses may be composed of mixtures of a few elemental synergies, they suggest that composition of postural responses is a complex process that includes perturbation direction as a continuous variable.
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Normal subjects performed bilaterally symmetric rapid elbow flexions or extensions ("focal movements") while standing. Specific patterns of electromyographic activity in leg and trunk muscles ("associated postural adjustments") were seen for each type of movement. The biomechanical significance of these postural adjustments was analysed by means of the ground reaction forces and motion of the various body segments. Experimental data were compared with that from a theoretical model of the body consisting of a six segment kinetic chain with rigid links. Distinct patterns of the ground reaction forces with elbow flexion were opposite in direction to those seen with elbow extension. Movements of the various body segments were small and specific for a certain focal movement. Dynamic perturbations arising from the arm movement in an anteroposterior direction were found to be compensated by postural adjustments, whereas vertical perturbations were not compensated. The muscular activity acting about different joints in the different movements was found to correlate with the predictions of activity needed to compensate for net joint reaction moments arising from the focal movement. Motion of the various body segments could be understood as resulting from the interplay of the net reaction moments and the net muscular moments at the different joints. Dynamic postural requirements are accomplished by a precise active compensation initiated before the focal movement.
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We studied the extent to which automatic postural actions in standing human subjects are organized by a limited repertoire of central motor programs. Subjects stood on support surfaces of various lengths, which forced them to adopt different postural movement strategies to compensate for the same external perturbations. We assessed whether a continuum or a limited set of muscle activation patterns was used to produce different movement patterns and the extent to which movement patterns were influenced by prior experience. Exposing subjects standing on a normal support surface to brief forward and backward horizontal surface perturbations elicited relatively stereotyped patterns of leg and trunk muscle activation with 73- to 110-ms latencies. Activity began in the ankle joint muscles and then radiated in sequence to thigh and then trunk muscles on the same dorsal or ventral aspect of the body. This activation pattern exerted compensatory torques about the ankle joints, which restored equilibrium by moving the body center of mass forward or backward. This pattern has been termed the ankle strategy because it restores equilibrium by moving the body primarily around the ankle joints. To successfully maintain balance while standing on a support surface short in relation to foot length, subjects activated leg and trunk muscles at similar latencies but organized the activity differently. The trunk and thigh muscles antagonistic to those used in the ankle strategy were activated in the opposite proximal-to-distal sequence, whereas the ankle muscles were generally unresponsive. This activation pattern produced a compensatory horizontal shear force against the support surface but little, if any, ankle torque. This pattern has been termed the hip strategy, because the resulting motion is focused primarily about the hip joints. Exposing subjects to horizontal surface perturbations while standing on support surfaces intermediate in length between the shortest and longest elicited more complex postural movements and associated muscle activation patterns that resembled ankle and hip strategies combined in different temporal relations. These complex postural movements were executed with combinations of torque and horizontal shear forces and motions of ankle and hip joints. During the first 5-20 practice trials immediately following changes from one support surface length to another, response latencies were unchanged. The activation patterns, however, were complex and resembled the patterns observed during well-practiced stance on surfaces of intermediate lengths.(ABSTRACT TRUNCATED AT 400 WORDS)
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