Mediolateral Center Of Pressure Research Articles

The immediate effect of physical activity on standing balance in healthy and balance‐impaired older people

To determine if standing balance was affected by moderate levels of physical activity in healthy young, healthy older and balance-impaired older adults. Thirty-one healthy young, 33 healthy older and 22 balance-impaired older adults took part. Centre of pressure (COP) motion was measured before and immediately after participants undertook 14 minutes of self-paced, moderate intensity physical activity. All groups responded in a similar manner. Following the physical activity circuit, mediolateral COP displacement and standard deviation of mediolateral COP position increased by 5% and 17%, respectively. Anteroposterior COP displacement and COP standard deviation, and total COP displacement, did not change. All changes were small compared with the magnitude of the group differences. A small increase in fall risk may exist immediately following physical activity and older people may need to exercise caution following moderate intensity bouts of physical activity to prevent falling.

Poster 40: The Relationship Between Center of Pressure Variability and Gait Function Following Stroke

Objective: To determine the association between variability in the (1) center of pressure (COP) length and temporal symmetry and (2) mediolateral (ML) COP position and sensorimotor control, among people with stroke during gait. Design: Descriptive analysis. Setting: Motor control laboratory in a rehabilitation hospital. Participants: A convenience sample of community-dwelling stroke survivors. Intervention: Each participant was asked to walk a distance of 7m over a pressure-sensitive mat at their preferred pace and as fast as they could safely walk.

Lateral Trunk Displacement and Stability During Sit-to-Stand Transfer in Relation to Foot Placement in Patients With Hemiparesis

Background. In hemiparetic individuals, sit-to-stand (STS) transfer is characterized by asymmetric weight-bearing and altered trunk kinematics that can be improved by positioning the affected foot behind the nonaffected one. Objective. To examine the influence of frontal trunk kinematics on medio-lateral displacements of the center of pressure (CP) during STS performed with the feet placed in 2 different positions, as well as relationships between these parameters, medio-lateral stability, and clinical scores of the participants. Methods. Eighteen patients with chronic stroke and 15 control individuals were evaluated during sit-to-stand transfers either in spontaneous foot position or with their affected or dominant foot placed behind, respectively. Medio-lateral CP, pelvis, and shoulder displacement were analyzed using 3D kinematic and kinetic data recordings of the whole task. Motor and sensory impairment, spasticity, muscle strength, and equilibrium were evaluated by standard scales. The possible time during which a participant could prevent a fall (minimal time-to-contact) was used as a stability index. Results. Spontaneously, the deviation of the CP of stroke participants paralleled the tilt of the trunk toward the nonaffected side, as early as the first third of the task. With the affected foot placed behind, trunk position did not differ from those of control participants who executed the transfer spontaneously. Hemiparetic participants were less stable than control participants. Placement of the feet had no significant effect on the stability of either group. Stability was strongly associated with better motor scores on the Chedoke-McMaster Stroke Assessment. Conclusions. In hemiparetic individuals, improving STS symmetry by positioning the affected foot behind the nonaffected one did not decrease medio-lateral stability, which was associated with the level of stroke-related motor impairments.

Applying stabilometry in characterizing floor sitting modes of women

Abstract The study elucidates the applicability of stabiolomety in evaluating floor sitting modes and characterizing the center of pressure (CoP) displacement patterns of women in sitting. The measurement included quantifying the stabilometric dimensions while women (N=10) seated on the piezoelectric force platform in different modes—such as squatting, left leg crossed, right leg vertically bent at knee, and vice versa, both legs bent at knee without pelvic support, legs extended and locked at knee, sideways sitting with legs folded. The principal component analysis of 10 CoP dimensions yielded three-component model, describing (1) the size, radius, and range of the CoP oscillation, (2) the trajectory (trace) length and velocity of CoP displacement, and (3) the directional CoP displacement, such as anterio-posterior (AP) and medio-lateral (ML) displacements. Detailed one-way repeated measures ANOVA showed that the sitting modes had discernable effects on the amplitude deviations as well as velocity parameters derived from CoP co-ordinates. The extending of legs caused the body to move largely in the AP direction, and also markedly influenced the CoP trajectory length as well as the velocity of CoP displacements, indicating greater instability in the postures. Knee bent modes as well as sideways sitting resulted in larger ML excursion of CoP. Squatting with both legs crossed had equilateral AP and ML CoP displacement with least velocity of displacement, and identified as a more stable floor seated posture. Eleven envelopes of CoP trace patterns were characterized in terms of ML, AP, centralized, diffused, and multi-centric CoP movement from its barycenter. The CoP trace patterns did not indicate one pattern—one posture relationship; however, the centralized CoP displacement was most prevalent in squatting as well as sideways sitting postures. The diffused nature of displacement was dominant in knee bent postures. The ML butterfly and AP patterns were evenly present in extended legs, locked at knee postures and in without pelvic support knee bent posture. The first of the kind study reflects a broadened scope of stabilometry in profiling functional measures of postural balance of women in floor sitting modes. Relevance to industry The postural stability/instability is a crucial concern to mitigate risk potentials of spinal and musculo-skeletal injuries at workplaces. The stabilometry is a promising approach to ascertain and characterize women's floor sitting modes, for neurological, orthopedic, and ergonomics applications.

Cardio‐postural interactions and aging

Introduction: Until recently cardiovascular and postural reflexes have been looked at as independent control systems. In this study we propose an interaction between these two systems, particularly in relation to the maintenance of venous return through skeletal muscle pump in conditions of impaired vascular control or increased venous pooling. We investigated this “cardio‐postural” interaction with aging. Methods: Healthy elderly and young subjects were tested in a sit to stand test. Mediolateral centre of pressure (COP) trajectory, as well as non‐invasive heart rate and blood pressure data were collected in two test conditions (eyes open or eyes closed) in randomized order. Data was collected in over a 10 minute period in two equal phases (sitting followed by standing). A power spectral density analysis was performed for mediolateral sway and BP for each subject. Results: Postural sway power was higher in elderly subjects with distinctive low frequency peaks (<0.1 Hz) that matched peaks found in blood pressure. Both COP and BP data had variation in the higher frequency range (0.15–0.25 Hz) that corresponded to respiration. The observed increase, with age, in postural sway in a region corresponding to low frequency blood pressure variation may represent an increase in skeletal muscle pump activity to maintain blood pressure in the elderly due to a reduction in baroreflex with age. Funded by Simon Fraser University.

Stance and sensory feedback influence on postural dynamics

This study examined the effects of ice-induced plantar desensitization and the withdrawal of visual feedback on the magnitude and time-dependent structure of postural sway variability. The magnitude of variability was quantified as the area of an ellipse enclosing 95% of the center of pressure (COP) time-series during normal and tandem stances. The same time-series were also analyzed using Approximate Entropy (ApEn) and Cross-Approximate Entropy (CrossApEn) as indices of irregularity and asynchrony between the mediolateral and anteroposterior COP motions. Variability increased during tandem stance and this increase was compounded by both visual feedback withdrawal and cutaneous desensitization. Both ApEn (mediolateral and anteroposterior COP motion) and CrossApEn increased with the withdrawal of visual feedback during the tandem stance, but decreased significantly during normal stance. The results of the study demonstrate that plantar desensitization only affected the magnitude of sway variability but did not alter its time-dependent structure. Contrasting effects on the structure of postural sway variability with visual feedback withdrawal were observed during the different stances, highlighting the role of task demands in postural dynamics.

Free moment contribution to quiet standing in able-bodied and scoliotic girls

Adolescent idiopathic scoliosis girls are known to display standing imbalance. In addition to a motor deficit problem, the axial torsion of the spine and trunk torsion could reflect an imbalance around the vertical axis. Unlike the excursion of the center of pressure (COP), the forces and moments were rarely addressed to characterize the quiet standing balance. Nonetheless, one dynamical parameter, called free moment (T(V)), representing the vertical torque on the feet can reflect the oscillation around the vertical axis associated to the standing imbalance. The objectives of this study were to test if the free moment variability can be utilized to characterize standing balance in a group of able-bodied and non-treated scoliotic girls and to determine if it was associated with that of the COP among each group of subjects tested. Forty-six adolescent girls with half of them presenting an adolescent idiopathic scoliosis were tested during quiet standing balance. Standing balance was assessed with the subjects standing upright and bare feet on a force plate. RMS and range of COP excursions and free moment were calculated. The scoliotic group displayed higher variability in COP excursion by about 24% than the able-bodied girls. Similarly, the T(V) RMS (P = 0.00136) and range (P = 0.00197) were statistically higher by about 42% in the scoliotic group. The variability of T(V) was associated with that of the COP in both groups. In the medio-lateral direction, the significant correlations between the RMS and range of the free moment and those of the COP were about 0.7 for the able-bodied group and 0.5 for the medio-lateral COP range for the scoliotic group girls. Along the antero-posterior axis, the only statistically significant correlations were observed for the scoliotic group. The free moment variability about the COP measured during quiet standing can be suggestive of an asymmetry control of the trunk around the vertical axis during standing balance. Its variability was more pronounced in scoliotic girls and was associated with the antero-posterior COP variability reflecting both biomechanical and motor control deficits. Free moment calculation could be a supplement insight into the standing balance of scoliotic subjects.

Time-to-Boundary Measures of Postural Control during Single Leg Quiet Standing

A novel approach to quantifying postural stability in single leg stance is assessment of time-to-boundary (TTB) of center of pressure (COP) excursions. TTB measures estimate the time required for the COP to reach the boundary of the base of support if it were to continue on its instantaneous trajectory and velocity, thus quantifying the spatiotemporal characteristics of postural control. Our purposes were to examine: (a) the intrasession reliability of TTB and traditional COP-based measures of postural control, and (b) the correlations between these measures. Twenty-four young women completed three 10-second trials of single-limb quiet standing on each limb. Traditional measures included mean velocity, standard deviation, and range of mediolateral (ML) and anterior-posterior (AP) COP excursions. TTB variables were the absolute minimum, mean of minimum samples, and standard deviation of minimum samples in the ML and AP directions. The intrasession reliability of TTB measures was comparable to traditional COP based measures. Correlations between TTB and traditional COP based measures were weaker than those within each category of measures, indicating that TTB measures capture different aspects of postural control than traditional measures. TTB measures provide a unique method of assessing spatiotemporal characteristics of postural control during single limb stance.

2.27 Controlling stability in challenging environments:Effects of ageing on modulation of rapid stepping reactions

A rapid step up was compared with a rapid step forward to assess the challenge they posed to postural stability in the medio-lateral (ML) direction. The center of pressure (COP) motion, and hip abductor muscle activity were compared between the two tasks in nine young healthy subjects. Analysis revealed that in the step up task there was a greater range and velocity of medio-lateral COP motion, an earlier gluteus medius onset time and a larger magnitude of gluteus medius activity than in the step forward task. The step up task appears to provide a greater challenge to ML postural stability than a step forward and thus may be an appropriate paradigm for the investigation of medio-lateral postural instability.

Muscular and centre of pressure response to sudden release of load in symmetric and asymmetric stoop lifting tasks

Sudden changes in load during asymmetric lifting may be associated with a particularly high risk of loss of balance and spinal injury. Centre of pressure (COP) motions and electromyographic responses of trunk and lower limb muscles were studied in 10 normal male volunteers during sudden release of 20, 40, 60 and 80 N stoop lifting loads in symmetric and asymmetric postures. Similar overall COP responses and muscular response strategies to sudden release of load were seen in both postures, although the asymmetric posture showed a larger medio-lateral COP displacements and greater co-contraction asymmetries. While sudden release of load in asymmetric stoop lifting does not seem to involve a greater risk of fall than symmetric lifting, the muscular response results in more complex and asymmetric loading of the trunk, indicating greater localised segmental loading and therefore increased risk of tissue injury.

Changes in the standing posture of stroke patients during rehabilitation

The aim of this study was to analyze the changes in the standing center of pressure (COP) in a hemiplegic adult population at the beginning and the end of in-patient rehabilitation. The trajectory of the COP was recorded on a force platform and was analyzed in terms of the frequency spectra of the center of gravity (COG), and the frequency spectra of the COP minus COG, a derived measure of neuromuscular stiffness. The study population consisted of eight hemiplegic subjects, median age of 53.5 years (range 27-79 years). The median interval between stroke and the first series of measures was 31 days (range 4-127) and the median interval between the two measures was 47.5 days (range 12-92). All the subjects were treated in an inpatient setting in a Neurorehabilitation Center. Our results showed that following rehabilitation, there was a reduction in the amplitude of the medio-lateral frequency spectra of the COP from a median of 5.651 mm (range 3.13-14.05) at the first measurement to 4.408 mm (range 2.40-8.58) at the second measurement. These changes were significant (p<0.05). Significant changes were also observed in the measure of COP minus COG, from 1.324 mm (range 0.92-2.63) on the first measure to 0.917 mm (range 0.46-1.53) on the second measure. In conclusion, the medio-lateral COP trajectory of hemiplegic subjects significantly improved during rehabilitation. We hypothesized that a major component of this improvement was the decrease in neuromuscular stiffness of the adductor and abductor muscles of the hips.

Effect of detomidine on postural sway in horses

AbstractThe objective of this study was to apply postural sway analysis to measure balance deficits after intravenous administration of detomidine. Six healthy horses were treated intravenously with detomidine (10 μg kg−1, 20 μgkg−1) and saline in random order, with three days between treatments. Postural sway was measured immediately after administration and at 15 min intervals until 120 min had elapsed. Horses stood squarely with all four hooves on a force platform, while the location of the centre of pressure (COP) was recorded continuously for 10 s at 1000 Hz. Five 10 s recordings were analysed and average values calculated for mediolateral COP range of motion, craniocaudal COP range of motion, mean COP radius, COP area and mean COP velocity. All COP variables increased immediately after sedation, but generally returned to normal limits within 15 and 30 min of detomidine administration at 10 and 20 μg kg−1, respectively. The head was lowered for at least 90 min after administration. Balance is affected by detomidine and normal balance is regained later after a higher dose. Procedures requiring balance should not be performed within 15–30 min of detomidine administration. COP variables are a good indicator of the effect of sedation on postural sway, but head position is not.

Interaction between Attention Demanding Motor and Cognitive Tasks and Static Postural Stability

Background: Due to the often-reported decrease in postural stability in the elderly, it is important to understand factors that may contribute to reduced postural stability. It is possible that attention-demanding focal tasks performed concurrent with postural regulation influence postural stability. Objective: This study utilized dual-task methodology to determine if motor or cognitive focal tasks interact with center of pressure (COP) excursion during static bipedal stance in healthy young and healthy elderly subjects (n = 18). Methods: The cognitive task involved silently solving an orally-presented multi-step arithmetic problem over a 30-second period. The motor task was a 30-second bilateral static finger-thumb pinch task performed at 10% of maximal voluntary contraction with a pair of pinch-force transducers. Each focal task was performed separately, and in a condition in which both tasks were performed simultaneously. COP excursion was compared in quiet standing (no focal task) and during performance of the focal tasks with full vision and with vision occluded. Results: Performance on the focal tasks was unaffected by increased postural demands during stance as compared to a seated baseline condition. This was the case for both age groups, and for the full vision and occluded vision conditions. Medio-lateral COP excursion was reduced over the quiet standing pretest condition when attentional focus was on the cognitive task, suggesting that COP was influenced centrally during cognition. In contrast, COP excursion increased over the quiet standing pretest condition when performing the motor focal task, suggesting a reduced ability to suppress sway when the motor system was concurrently occupied with a voluntary task that shared the same input-output resources. Conclusion: The ability to share attentional resources among focal and postural tasks was similar in healthy young and elderly subjects.

Noise-enhanced balance control in older adults.

Somatosensory information is critical to balance control and fall prevention in older adults. Recently, it has been shown that low-level input noise (electrical or mechanical) can enhance the sensitivity of the human somatosensory system. In this study, we tested the effect of low-level electrical noise, applied at the knee, on balance control in 13 healthy elderly volunteers. Subjects performed multiple single-legged stance trials with imperceptible electrical noise applied at the knee during half of the trials. Balance performance was characterized using a force platform to measure the displacement of the center of pressure (COP) under the subject's stance foot. Seven sway parameters were extracted from the COP time series. Improved balance was defined as a reduction in postural sway as indicated by decreases in the COP measures. Six of the seven sway parameters decreased with electrical noise. Three of these parameters decreased significantly ( < 0.05), and a fourth parameter was borderline significant. Averaged across subjects, the application of electrical noise resulted in a 3.8% reduction in mediolateral COP standard deviation ( = 0.04), a 5.4% decrease in the maximum anteroposterior COP excursion ( = 0.03), a 3.1% reduction in the COP path length ( = 0.04), and a 7.8% decrease in swept area ( = 0.05). The results suggest that imperceptible electrical noise, when applied to the knee, can enhance the balance performance of healthy older adults. These findings suggest that electrical noise-based devices may be effective in improving balance control in elderly people.

Visual-vestibular interactions in postural control during the execution of a dynamic task.

The purpose of this experiment was to determine the interaction between visual and vestibular information during the transition from quiet standing to the completion of a forward step. Six subjects were asked to take one step forward at the sound of an audio tone, with their eyes open or closed, and terminate the step in a standing position. During stimulation trials, galvanic vestibular stimulation (GVS) was delivered 1500 ms before the auditory cue. GVS was delivered at an intensity three-fold that of each subject's quiet stance threshold with either stimulus right, left or no stimulation. Force data were collected from three forceplates for the calculation of centre of pressure (CoP), and kinematic data were used to calculate centre of mass (CoM) and body trajectories. In quiet stance all subjects responded to the GVS perturbation by demonstrating upper body segment roll and whole body sway towards the anode electrode. Unexpectedly, in the presence of vision during quiet stance, the upper body roll response was not attenuated, even though the CoP sway patterns were reduced when vision was available. During the initiation phase of the step, despite ongoing GVS stimulation, there were no significant effects seen in CoM, CoP or upper body roll responses. During step execution, however, both CoM displacement and upper body roll demonstrated significant effects and both responses were significantly reduced when subjects' eyes were open. Analysis of the medio-lateral CoP integrals also indicated a strong stimulation effect between conditions late in the execution phase, which were largely attenuated with vision. The results suggest that the importance of visual and vestibular information varies depending on the phase of the task. In addition, the different integration between visual and vestibular input during quiet standing suggests a dual role for vestibular information. We propose that vestibular information in quiet standing has a role in maintaining whole body postural stability, as well as playing an integral role in the alignment of the body segments in preparation for proper movement execution. Vision was demonstrated to differentially attenuate these responses based on the phase of the task. Thus, visual and vestibular information appear to be integrated differently across the different phases of a forward-stepping task.

Walking strategy in diabetic patients with peripheral neuropathy.

Diabetic neuropathic patients show a peculiar loading pattern of the foot, which led us to hypothesize that a substantial modification exists in their deambulatory strategy. The aim of the present study was to support this hypothesis by quantifying the changes of the loading patterns and by monitoring the excursion of center of pressure (COP) during gait. -A total of 21 healthy volunteers (C) and 61 diabetic patients were evaluated: 27 diabetic subjects without neuropathy (D), 19 with neuropathy (DN), and 15 with previous neuropathic ulcer (DPU). A piezo-dynamometric platform was used to record the foot-to-floor interaction by measuring loading time and the instantaneous COP position during the stance phase of gait. Loading time was significantly longer in neuropathic patients than in control subjects (DPU: 816.8 +/- 150 ms; DN: 828.6 +/- 152 ms; D: 766.5 +/- 89.9 ms; C: 723.7 +/- 65.7 ms; P < 0.05). COP excursion along the medio-lateral axis of the foot clearly decreased from C to DPU groups (C: 6.41 +/- 0.1 cm; D: 4.88 +/- 0.2 cm; DN: 4.57 +/- 0.1 cm; DPU: 3.36 +/- 0.1 cm; P < 0.05) as well as COP excursion along the longitudinal axis for the DPU group only (C: 26.6 +/- 1 cm; D: 26.9 +/- 1 cm; DN: 27.2 +/- 1 cm; DPU: 24.2 +/- 1 cm; P < 0.05). COP integrals were significantly reduced for all pathological classes (DPU: 14.2 +/- 8 cm(2); DN: 25.8 +/- 6 cm(2); D: 27.7 +/- 3 cm(2); C: 38.6 +/- 6 cm(2); P < 0.05). The accurate quantification of loading patterns and of COP excursions and integrals highlights changes of foot-to-floor interaction in diabetic neuropathic patients. The decreased medio-lateral and longitudinal COP excursions and corresponding changes of loading times and patterns support our hypothesis that a change in the walking strategy of diabetic patients with peripheral neuropathy does occur.

The effects of stochastic galvanic vestibular stimulation on human postural sway.

Galvanic vestibular stimulation serves to modulate the continuous firing level of the peripheral vestibular afferents. It has been shown that the application of sinusoidally varying, bipolar galvanic currents to the vestibular system can lead to sinusoidally varying postural sway. Our objective was to test the hypothesis that stochastic galvanic vestibular stimulation can lead to coherent stochastic postural sway. Bipolar binaural stochastic galvanic vestibular stimulation was applied to nine healthy young subjects. Three different stochastic vestibular stimulation signals, each with a different frequency content (0-1 Hz, 1-2 Hz, and 0-2 Hz), were used. The stimulation level (range 0.4-1.5 mA, peak to peak) was determined on an individual basis. Twenty 60-s trials were conducted on each subject - 15 stimulation trials (5 trials with each stimulation signal) and 5 control (no stimulation) trials. During the trials, subjects stood in a relaxed, upright position with their head facing forward. Postural sway was evaluated by using a force platform to measure the displacements of the center of pressure (COP) under each subject's feet. Cross-spectral measures were used to quantify the relationship between the applied stimulus and the resulting COP time series. We found significant coherency between the stochastic vestibular stimulation signal and the resulting mediolateral COP time series in the majority of trials in 8 of the 9 subjects tested. The coherency results for each stimulation signal were reproducible from trial to trial, and the highest degree of coherency was found for the 1- to 2-Hz stochastic vestibular stimulation signal. In general, for the nine subjects tested, we did not find consistent significant coherency between the stochastic vestibular stimulation signals and the anteroposterior COP time series. This work demonstrates that, in subjects who are facing forward, bipolar binaural stochastic galvanic stimulation of the vestibular system leads to coherent stochastic mediolateral postural sway, but it does not lead to coherent stochastic anteroposterior postural sway. Our finding that the coherency was highest for the 1- to 2-Hz stochastic vestibular stimulation signal may be due to the intrinsic dynamics of the quasi-static postural control system. In particular, it may result from the effects of the vestibular stimulus simply being superimposed upon the quiet-standing COP displacements. By utilizing stochastic stimulation signals, we ensured that the subjects could not predict a change in the vestibular stimulus. Thus, our findings indicate that subjects can act as "responders" to galvanic vestibular stimulation.

Normal and shear strain distributions of the equine third metacarpal during locomotion: Characterizing bone's functional milieu

The study elucidates the applicability of stabiolomety in evaluating floor sitting modes and characterizing the center of pressure (CoP) displacement patterns of women in sitting. The measurement included quantifying the stabilometric dimensions while women (N=10) seated on the piezoelectric force platform in different modes—such as squatting, left leg crossed, right leg vertically bent at knee, and vice versa, both legs bent at knee without pelvic support, legs extended and locked at knee, sideways sitting with legs folded. The principal component analysis of 10 CoP dimensions yielded three-component model, describing (1) the size, radius, and range of the CoP oscillation, (2) the trajectory (trace) length and velocity of CoP displacement, and (3) the directional CoP displacement, such as anterio-posterior (AP) and medio-lateral (ML) displacements. Detailed one-way repeated measures ANOVA showed that the sitting modes had discernable effects on the amplitude deviations as well as velocity parameters derived from CoP co-ordinates. The extending of legs caused the body to move largely in the AP direction, and also markedly influenced the CoP trajectory length as well as the velocity of CoP displacements, indicating greater instability in the postures. Knee bent modes as well as sideways sitting resulted in larger ML excursion of CoP. Squatting with both legs crossed had equilateral AP and ML CoP displacement with least velocity of displacement, and identified as a more stable floor seated posture. Eleven envelopes of CoP trace patterns were characterized in terms of ML, AP, centralized, diffused, and multi-centric CoP movement from its barycenter. The CoP trace patterns did not indicate one pattern—one posture relationship; however, the centralized CoP displacement was most prevalent in squatting as well as sideways sitting postures. The diffused nature of displacement was dominant in knee bent postures. The ML butterfly and AP patterns were evenly present in extended legs, locked at knee postures and in without pelvic support knee bent posture. The first of the kind study reflects a broadened scope of stabilometry in profiling functional measures of postural balance of women in floor sitting modes.The postural stability/instability is a crucial concern to mitigate risk potentials of spinal and musculo-skeletal injuries at workplaces. The stabilometry is a promising approach to ascertain and characterize women's floor sitting modes, for neurological, orthopedic, and ergonomics applications.