Static Balance Conditions Research Articles

Development, modeling and analysis of a differential lever-bridge amplification mechanism

The displacement amplification mechanism is commonly utilized in micro/nano-manipulating systems to enhance the output stroke of piezoelectric actuators. Aiming at large amplification ratio, this paper proposes a symmetrical dual-stage amplification mechanism consisting of a differential lever mechanism and a half-bridge mechanism. With consideration of the coupling effect between the dual-stage amplification mechanism, a kinematic modeling method is developed for the symmetrical differential lever-bridge hybrid (SDLBH) mechanism on top of the static balance and constraint conditions of the branch chain. In particular, the force-deformation relationship of the flexible hinge is derived according to the flexibility matrix method. Based on the path constraint conditions of the branch chain, the static equilibrium equation as well as the displacement constraint conditions are obtained. Consequently, the input-output model of the SDLBH mechanism is established, which is capable of accurately predicting the amplification ratio and the mechanical stiffness. Finite element simulations and real time experiments on the SDLBH prototype effectively validate the mechanical performance as well as the accuracy of proposed modeling method. The performance sensitivity of the developed SDLBH mechanism is further analyzed by the Taguchi method, aiming to offer the optimization guideline for real applications.

Force Analysis of Statically Balanced Serially Connected Manipulators Using Springs Based on Torque Compatibilities Associated With Accumulative Joint Angles

AbstractForce analysis with regard to serial connected manipulators is discussed thoroughly in the past. However, force analysis of statically balanced manipulator using springs has not been widely addressed because spring forces and motions do not share an immediate association. In this article, spring forces are represented as accumulative joint angles of links crossed by springs and attached angles/lengths of springs. Torque equilibrium equations regarding the preconnected joint of a typical link as contributed by gravity force and spring force can be inwardly formed link by link from the end link. Compatibility with the same accumulative joint angle can be formulated under static balance conditions. Hence, spring attachment parameters such as spring stiffness and attachment lengths are constrained by given link properties and spring attachment angles. Thus, spring forces can be determined by a chosen set of stiffness and attached lengths of springs, and the joint reaction force can then be determined. Example figures of 3-degrees-of-freedom (DOFs) manipulators show that joint reaction forces are reduced by 22.6%, 40.1%, and 75.7% at joints 1, 2, and 3, respectively, than those without springs. It is found that besides balancing gravity, the statically balanced manipulator is with lower joint reaction forces. Hence, the manipulator can be more lightweight by using compact joints and links with the same material. Furthermore, the static and dynamic performance of the manipulator can be improved by the effect of reduced joint reaction forces as well.

Disparity between Perceptual Fall Risk and Physiological Fall Risk in Older Cannabis Users: A Pilot Study.

Aging is associated with cognitive decline and increased fall risk. Cognitive impairment is associated with cannabis use, which is increasing among older adults. Perceptual and physiological fall risk are discordant in some older adults, but whether cannabis use influences this association is unknown. The purpose of this study was to investigate possible disparities between perceptual and physiological fall risk in older cannabis users. Eight older medical cannabis users and eight sex- and age-matched non-users provided data on perceptual and physiological fall risk. Group differences were assessed, and perceptual fall risk was correlated with physiological fall risk. Perceptual risk and most of the physiological fall risk variables were equivalent between the groups. However, cannabis users performed significantly worse on unipedal stance than non-users. In addition, perceptual fall risk had weak correlations with physiological fall risk in the users (Spearman’s rho = 0.17–0.41) and moderate-strong correlations in non-users (rho = −0.18–0.67). Cannabis users might have a discrepancy between perceptual and physiological fall risk. Because both concepts play a role in quality of life, identifying strategies to improve them may have significant benefits. Future studies investigating additional perceptual (e.g., cognition, fear of falling, depression, anxiety), physiological (e.g., more challenging static and dynamic balance conditions), and general fall risk are warranted.

A static sound source can improve postural stability during walking

BACKGROUND: During walking, postural stability is controlled by visual, vestibular and proprioceptive input. The auditory system uses acoustic input to localize sound sources. For some static balance conditions, the auditory influence on posture was already proven. Little is known about the impact of auditory inputs on balance in dynamic conditions. OBJECTIVE: This study is aimed at investigating postural stability of walking tasks in silence and sound on condition to better understand the impact of auditory input on balance in movement. METHODS: Thirty participants performed: walking (eyes open), tandem steps, walking with turning head and walking over barriers. During each task, acoustic condition changed between silence and presented noise through an earth-fixed loudspeaker located at the end of the walking distance. Body sway velocity was recorded close to the body’s center of gravity. RESULTS: A decreased body sway velocity was significant for walking (eyes open), tandem steps and walking over barriers when noise was presented. Those auditory stimuli did not affect sway velocity while walking with turning head. The posture has probably improved due to the localization ability when walking with the head facing forward, while the localization ability was impaired when turning the head. CONCLUSIONS: The localization ability of a fixed sound source through the auditory system has a significant but limited impact on posture while walking.

Accuracy analysis of spatial multi-loop mechanism effected by paired bearings support joint clearance

The primary objective of this work is to present a three-dimensional (3D) clearance model of the paired bearings support joint (PBS-joint) and address the influence of PBS-joint clearance on the accuracy of the spatial multi-loop mechanism. Through the synthetic use of the vector and homogeneous coordinate transformation methods, the 3D clearance model of the PBS-joint is obtained on the basis of the static balance condition. When clearance is equated as a spatial virtual link, the error space solution models of serial mechanism and single-loop mechanism are developed respectively according to the Denavit-Hartenberg method and the geometric closure condition. The error space standardization solution model of the multi-loop mechanism is then presented through improving the low-layer loop sequence description method of the topological structure relations. Finally, the application in the basic loop mechanism is demonstrated to discuss the procedures adopted in this work and the influence of the PBS-joint clearance. Results show that the PBS-joint clearance may cause the error on the point with a 3D deviation transmission path to deviate the normal distribution. Moreover, the plane-joint clearance model may not yield an accurate analysis of the spatial mechanism.

Robotic evaluation of fall risk in older people: Results on trunk parameters in static and dynamic balance conditions by hunova robot

Maintaining balance depends on the integration of sensory, proprioceptive and vestibular information to appropriately adjust movements responses to different postural conditions. hunova is a new robotic device developed and validated to perform functional evaluation and sensorimotor rehabilitation of lower limbs and trunk in static and dynamic environments. Aim of this study was to evaluate balance parameters in older subjects with different risk of fall. One hundred subjects aged ≥ 65 years (mean age 77.17 ± 6.49 SD years) were enrolled. According to the number of falls in the last 12 months, participants were allocated to low, medium or high-risk of fall. Balance was evaluated by hunova in static, unstable and perturbating conditions, in both standing/seated positions and with open/closed eyes. Parameters were: sway area (SA), path length (PL), range of oscillations in anterior-posterior (OAP) and mediolateral directions (OML) in both platform and trunk oscillations. Statistical analysis was carried out by means of Kruskal–Wallis test on medians and Spearman correlation test. Older fallers had higher trunk PL both in unstable [fallers, median (IQR): 32.5 (23.35) vs. non-faller 43.79 (29.21) (deg), P < 0.01] and moving [fallers 35.94 (22.12) vs. non-faller 45.27 (31.29) (deg), P < 0.05] platform in standing with open eyes condition. Trunk SA and OML were significantly different in subjects with different fall risk classes in perturbating conditions when seated with closed eyes. Trunk parameters in unstable and perturbating conditions showed also a strong and significative correlation with age ( P < 0.01). Hunova robot was able to detect physiological components involved in balance maintenance in older subjects with different fall risk. This evaluation could be crucial to prevent falls and to plan rehabilitation programs in older subjects at different risk of falls.

Validity and Reliability of a Portable Balance Tracking System, BTrackS, in Older Adults.

Falls are the leading cause of disability, injury, hospital admission, and injury-related death among older adults. Balance limitations have consistently been identified as predictors of falls and increased fall risk. Field measures of balance are limited by issues of subjectivity, ceiling effects, and low sensitivity to change. The gold standard for measuring balance is the force plate; however, its field use is untenable due to high cost and lack of portability. Thus, a critical need is observed for valid objective field measures of balance to accurately assess balance and identify limitations over time. The purpose of this study was to examine the concurrent validity and 3-day test-retest reliability of Balance Tracking System (BTrackS) in community-dwelling older adults. Minimal detectable change values were also calculated to reflect changes in balance beyond measurement error. Postural sway data were collected from community-dwelling older adults (N = 49, mean [SD] age = 71.3 [7.3] years) with a force plate and BTrackS in multitrial eyes open (EO) and eyes closed (EC) static balance conditions. Force sensors transmitted BTrackS data via a USB to a computer running custom software. Three approaches to concurrent validity were taken including calculation of Pearson product moment correlation coefficients, repeated-measures ANOVAs, and Bland-Altman plots. Three-day test-retest reliability of BTrackS was examined in a second sample of 47 community-dwelling older adults (mean [SD] age = 75.8 [7.7] years) using intraclass correlation coefficients and MDC values at 95% CI (MDC95) were calculated. BTrackS demonstrated good validity using Pearson product moment correlations (r > 0.90). Repeated-measures ANOVA and Bland-Altman plots indicated some BTrackS bias with center of pressure (COP) values higher than FP COP values in the EO (mean [SD] bias = 4.0 [6.8]) and EC (mean [SD] bias = 9.6 [12.3]) conditions. Test-retest reliability using intraclass correlation coefficients (ICC2.1 was excellent (0.83) and calculated MDC95 for EO (9.6 cm) and EC (19.4 cm) and suggested that postural sway changes of these amounts are meaningful. BTrackS showed some bias with values exceeding force plate values in both EO and EC conditions. Excellent test-retest reliability and resulting MDC95 values indicated that BTrackS has the potential to identify meaningful changes in balance that may warrant intervention. BTrackS is an objective measure of balance that can be used to monitor balance in community-dwelling older adults over time. It can reliably identify changes that may require further attention (eg, fall-prevention strategies, declines in physical function) and shows promise for assessing intervention efficacy in this growing segment of the population.

Real-time visual feedback of COM and COP motion properties differentially modifies postural control structures.

The experiment was setup to investigate the control of human quiet standing through the manipulation of augmented visual information feedback of selective properties of the motion of two primary variables in postural control: center of pressure (COP) and center of mass (COM). Five properties of feedback information were contrasted to a no feedback dual-task (watching a movie) control condition to determine the impact of visual real-time feedback on the coordination of the joint motions in postural control in both static and dynamic one-leg standing postures. The feedback information included 2D COP or COM position and macro variables derived from the COP and COM motions, namely virtual time-to-contact (VTC) and the COP-COM coupling. The findings in the static condition showed that the VTC and COP-COM coupling feedback conditions decreased postural motion more than the 2D COP or COM positional information. These variables also induced larger sway amplitudes in the dynamic condition showing a more progressive search strategy in exploring the stability limits. Canonical correlation analysis (CCA) found that COP-COM coupling contributed less than the other feedback variables to the redundancy of the system reflected in the common variance between joint motions and properties of sway motion. The COP-COM coupling had the lowest weighting of the motion properties to redundancy under the feedback conditions but overall the qualitative pattern of the joint motion structures was preserved within the respective static and dynamic balance conditions.

A coupling extended multiscale finite element method for dynamic analysis of heterogeneous saturated porous media

A coupling extended multiscale finite element method (CEMsFEM) is developed for the dynamic analysis of heterogeneous saturated porous media. The coupling numerical base functions are constructed by a unified method with an equivalent stiffness matrix. To improve the computational accuracy, an additional coupling term that could reflect the interaction of the deformations among different directions is introduced into the numerical base functions. In addition, a kind of multi-node coarse element is adopted to describe the complex high-order deformation on the boundary of the coarse element for the two-dimensional dynamic problem. The coarse element tests show that the coupling numerical base functions could not only take account of the interaction of the solid skeleton and the pore fluid but also consider the effect of the inertial force in the dynamic problems. On the other hand, based on the static balance condition of the coarse element, an improved downscaling technique is proposed to directly obtain the satisfying microscopic solutions in the CEMsFEM. Both one-dimensional and two-dimensional numerical examples of the heterogeneous saturated porous media are carried out, and the results verify the validity and the efficiency of the CEMsFEM by comparing with the conventional finite element method. Copyright © 2015 John Wiley & Sons, Ltd.

Predicting Falls in Older Adults

Accelerometers have been evaluated extensively regarding their ability to assess postural sway. Horizontal center of mass (COM) accelerations have been reported to be positively associated fall risk in older adult populations. In fact, we previously reported that an accelerometer-based balance assessment (ABA) was superior to select clinical measures at retrospectively discriminating fallers from non-fallers. PURPOSE: Understanding that a retrospective analysis of fall risk is inherently flawed, we aimed to prospectively evaluate the ABA. METHODS: Ninety-three independent community-living otherwise healthy older adults (age 86±6 years) were recruited from multiple facilities. For the baseline assessment, participants completed the ABA (8 static balance tasks), Timed Up-and-Go (TUG), Berg Balance Scale (BBS), and the Activities-Specific Balance Confidence (ABC) Scale. Participants were then called weekly for 12 months to evaluate falls after the baseline assessment. We then compared outcomes from the ABA and clinical assessments between participants who never fell, participants who fell once, and participants who fell two or more times during the follow-up period. RESULTS: During the 12-month follow-up, 22/93 (24%) of the participants fell once and 32/93 (34%) fell at least twice. The average root mean square of the horizontal COM accelerations across the 8 ABA static balance conditions for non-fallers, one time fallers, and multiple fallers (0.0126 ± 0.0049 g, 0.0122 ± 0.0030 g, and 0.0129 ± 0.0042 g, respectively) were statistically similar. Likewise, there were no significant differences between non-fallers, one time fallers, and multiple fallers with respect to the TUG (15.7 ± 12.0 s, 17.1 ± 10.2 s, and 12.8 ± 4.7 s, respectively), BBS (46.7 ± 7.4, 45.1 ± 10.1, and 47.3 ± 5.1, respectively), or the ABC Scale (69.6 ± 19.1, 68.0 ± 16.2, and 65.8 ± 18.1, respectively). CONCLUSIONS: In this 12-month prospective study, 58% of our study population fell at least once, but baseline performance on the ABA, TUG, BBS, and ABC Scale was not significantly associated with future single or multiple falls.

The Static Unbalance Analysis and Its Measurement System For Gimbals Axes of an Inertial Stabilization Platform

Abstract To reduce the influence of the static unbalance on an infrared missile guidance system, a new static unbalance measure system for the gimbals axes has been developed. Considering the coupling effects caused by a mass eccentricity, the static balance condition and measure sequence for each gimbal axis are obtained. A novel static unbalance test approach is proposed after analyzing the dynamic model of the measured gimbal axis. This approach is to drive the measured gimbal axis to do sinusoidal reciprocating motion in a small angle and collect its drive currents in real time. Then the static unbalance of the measured gimbal axis can be obtained by the current multi-cycle integration. Also a measuring system using the proposed approach has been developed. A balanced simulator is used to verify the proposed approach by the load and repeatability tests. The results show the proposed approach enhances the efficiency of the static unbalance measurement, and the developed measuring system is able to achieve a high precision with a greater stability.

Vibration perception threshold in relation to postural control and fall risk assessment in elderly

Purpose: This study investigates (i) the potential discriminative role of a clinical measure of peripheral neuropathy (PN) in assessing postural performance and fall risk and (ii) whether the integration of a simple screening vibration perception threshold (VPT) for PN in any physical (fall risk) assessment among elderly should be recommended, even if they do not suffer from DM. Method: One hundred and ninety-five elderly were entered in a four-group model: DM with PN (D+; n = 75), DM without PN (D−; n = 28), non-diabetic elderly with idiopathic PN (C+; n = 31) and non-diabetic elderly without PN (C−; n = 61). Posturographic sway parameters were captured during different static balance conditions (AMTI AccuGait, Watertown, MA). VPT, fall data, Mini-Mental State Examination and Clock Drawing Test were registered. Two-factor repeated-measures ANOVA was used to compare between groups and across balance conditions. Results: The groups with PN demonstrated a strikingly comparable, though bigger sway, and a higher prospective fall incidence than their peers without PN. Conclusions: The indication of PN, irrespective of its cause, interferes with postural control and fall incidence. The integration of a simple screening for PN (like bio-thesiometry) in any fall risk assessment among elderly is highly recommended.Implications for RehabilitationThe indication of peripheral neuropathy (PN), irrespective of its cause, interferes with postural control and fall incidence.Therefore, the integration of a simple screening for PN (like bio-thesiometry) in any fall risk assessment among elderly is highly recommended.It might be useful to integrate somatosensory stimulation in rehabilitation programs designed for fall prevention.

Effect of expertise in shooting and Taekwondo on bipedal and unipedal postural control isolated or concurrent with a reaction-time task

It was hypothesized that training in ‘static balance’ or ‘dynamic balance’ sports has differential effects on postural control and its attention demands during quiet standing. In order to test this hypothesis, two groups of female athletes practicing shooting, as a ‘static balance’ sport, and Taekwondo, as a ‘dynamic balance’ sport, and a control group of non-physically active females voluntarily participated in this study. Postural control was assessed during bipedal and unipedal stance with and without performing a Go/No-go reaction time task. Visual and/or support surface conditions were manipulated in bipedal and unipedal stances in order to modify postural difficulty. Mixed model analysis of variance was used to determine the effects of dual tasking on postural and cognitive performance. Similar pattern of results were found in bipedal and unipedal stances, with Taekwondo practitioners displaying larger sway, shooters displaying lower sway and non-athletes displaying sway characteristics intermediate to Taekwondo and shooting athletes. Larger effect was found in bipedal stance. Single to dual-task comparison of postural control showed no significant effect of mental task on sway velocity in shooters, indicating less cognitive effort invested in balance control during bipedal stance. We suggest that expertise in shooting has a more pronounced effect on decreased sway in static balance conditions. Furthermore, shooters invest less attention in postures that are more specific to their training, i.e. bipedal stance.

Balance and Mobility Dysfunction and Falls Risk in Older People with Mild to Moderate Alzheimer Disease

This study aimed to identify the magnitude and type of balance and mobility impairments in people with Alzheimer disease by comparing their performance with that of older people without cognitive impairment. Twenty-five community-dwelling people with mild to moderate Alzheimer disease and a comparison group of 25 cognitively intact age- and sex-matched people completed a comprehensive balance and mobility assessment. This included computerized posturography measures of static and dynamic balance under various conditions, clinical balance, and mobility measures, and measures of falls and falls risk. The level of falls risk was higher in people with Alzheimer disease. Standing balance in people with Alzheimer disease was significantly impaired across a range of static and dynamic balance conditions. Activity level, gait, and mobility measures were also impaired, particularly turning and dual tasks. The findings of the study highlight the value of including balance screening as a routine component of early dementia assessment. This would allow for the early detection of balance dysfunction and the introduction of balance retraining before impairments progress to more advanced levels.

The kinematics and statics of manipulators

As the kinematics and statics play a very important role in determining the actuating inputs and the effective loads that the end-effector sustains, this article focuses on this issue and proposes an analytical process to study the forward and inverse kinematics and statics of spatial manipulators. As series manipulators and parallel manipulators show different features in kinematics and statics, this article discusses them separately. First, the forward and inverse velocity problems of the manipulator linkages are investigated with reciprocal screw theory. Then, the static balance conditions together with forward and inverse statics of the manipulator linkages are established through virtual power theory. In the kinematics analysis, the primary conditions for feasible motions of an end-effector are addressed through velocity screws. Illustrative examples indicate that the method proposed in this article can be used to guide the singularity identification, path planning, and feasible motion determination.

Role of vision and task complexity on soleus H-reflex gain

There exists extensive evidence supporting the presence of reflex modulation in humans during a variety of motor tasks. The soleus H-reflex has been shown to be modulated during static and dynamic balance conditions as well as during various motor tasks. The purpose of this study was to examine the effects of two different stance positions and visual conditions on soleus H-reflex gain in 15 apparently healthy adults (mean age = 30.27 ± 6.92 yrs). The soleus H-reflexes were examined in two experimental stance conditions: two-legged (stable) and one-leg (unstable), and two visual conditions: eyes open and eyes closed. To assess the reflex gain, subjects performed ten trials under each of the four conditions and a soleus H-reflex was elicited during the performance of each trial. For each condition the peak-to-peak amplitude of the H-reflex and the EMG activity 50 ms prior to the stimulus was recorded. Differences in the peak-to-peak amplitudes of the soleus H-reflex for the experimental conditions were compared with a 2 × 2 (Stance × Vision) repeated measures ANOVA. The level of significance was p < 0.05. Results demonstrated significant differences in reflex gain for both the vision ( F l,15 = 4.87, p < 0.05) and the stance condition ( F l,15 = 14.86, p < 0.05). Although both the stance condition and vision significantly affected the H-reflex gain, there was no interaction between these two variables ( F l,15 = 0.17). From these results, we conclude that H-reflex gain was decreased both as stance complexity increased and as visual inputs were removed. Consistent with previous reports, it may be speculated that changes in presynaptic inhibition to the soleus Ia fibers regulate these gain changes. We propose that vision and stability of stance affect soleus H-reflex gain, but do so without any interactive effects.

Dynamic balancing of planar mechanisms using toric geometry

A mechanism is statically balanced if for any motion, it does not apply forces on the base. Moreover, if it does not apply torques on the base, the mechanism is said to be dynamically balanced. In this paper, a new method for determining the complete set of dynamically balanced planar four-bar mechanisms is presented. Using complex variables to model the kinematics of the mechanism, the static and dynamic balancing constraints are written as algebraic equations over complex variables and joint angular velocities. After elimination of the joint angular velocity variables, the problem is formulated as a problem of factorization of Laurent polynomials. Using tools from toric geometry including toric polynomial division, necessary and sufficient conditions for static and dynamic balancing of planar four-bar mechanisms are derived.

Dynamics Modeling and Simulation of a Bionic Swim Bladder System in Underwater Robotics

While considering that fish could suspend themselves under water and could enhance their mobility by adjusting its swim bladder, we have carried out research on a bionic swim bladder system in underwater robotics, which could amend the underwater robotics' static balance and controllability conditions even if the depth of water changes. First, this paper introduces the bio-swim bladder's structure and function. Second, it works out the dynamic model of the bionic swim bladder, and then it analyses the dynamic characteristic and effect of the bionic swim bladder system with the software Matlab/simulink. Finally, considering about the nonlinear relationship of the parameters in the model, this paper brings forward a dual-speed control method, which could make the effect of the bionic swim bladder non-coupling. The result of the simulation reveals that the bionic swim bladder could change the buoyancy and centroid distribution of the underwater robotics effectively and independently, bringing it into a balance state, under which the control and maneuverability could be enhanced.

Is balance different in women with and without stress urinary incontinence?

This study investigated whether there are differences in center of pressure (COP) displacement, trunk motion, and trunk muscle activity in women with and without stress urinary incontinence (SUI) during static balance tasks when the bladder is empty and moderately full. Subjects stood on a force plate during six static balance conditions: eyes open, eyes closed, standing on foam with eyes open, standing on foam with eyes closed, tandem stance, and standing on a short base. Electromyographic activity (EMG) of the pelvic floor (PF), abdominal, and erector spinae muscles were recorded using surface electrodes. Motion of the lumbar spine, pelvis, and hips was measured with four inclinometers. Trials were performed with the bladder empty, and when the subject reported a sensation of moderate bladder fullness after drinking 250-1,000 ml of water. Women with SUI had greater COP displacement (range and root mean square), and increased trunk muscle EMG during static balance tests compared to continent women. When tasks were performed with the bladder moderately full, COP displacement and abdominal muscle EMG were increased in both groups. This study demonstrates that women with SUI have decreased balance ability compared to continent women. Increased activity of the PF and trunk muscles in women with SUI may impair balance as a result of a reduced contribution of trunk movement to postural correction or compromised proprioceptive acuity. As compromised balance has been linked to falls risk, further research into balance deficits and falls prevalence in this population is warranted.

A speedy solution for balance and gait analysis: angular velocity measured at the centre of body mass

Falls are a serious problem for the elderly and others prone to fall. In particular, those over 65 years of age will suffer at least one fall a year and as a result will need cost-intensive medical treatment. Under these circumstances, an optimal clinical pathway should first identify those with a tendency to fall, second, pinpoint the disease-specific deficits in balance control and walking patterns, and third, offer the possibility through focused biofeedback training to reduce the number of falls suffered. This review describes new methods of assessing balance control in both static and dynamic balance conditions and their applications for balance rehabilitation. Technological advances and applied research have shown that body-worn sensors measuring angular velocity (gyroscopes) or the acceleration of the trunk can effectively quantify balance during stance and gait tasks, and can be used to detect potential fallers and discriminate between different balance disorders. Standing on foam support reveals balance deficits regardless of the underlying disease. Disease-specific balance deficits can be characterized by the pattern of trunk movements between various semi-stance and gait tasks. Angular velocity sensors have recently been shown to provide highly relevant information for use as biofeedback, or as an ambulatory device to record balance and gait performance over long periods of time in both clinical and natural living conditions. Angular velocity sensors can provide balance-relevant information directly to the clinician, and provide an important improvement on the complicated and time/cost-intensive techniques of traditional balance measurement systems.