scholarly journals Assessing Postural Instability and Cybersickness Through Linear and Angular Displacement

2019 ◽  
pp. 001872081988125 ◽  
Author(s):  
Christopher Widdowson ◽  
Israel Becerra ◽  
Cameron Merrill ◽  
Ranxiao Frances Wang ◽  
Steven LaValle
Keyword(s):  
Postural Stability ◽  
Center Of Pressure ◽  
Angular Displacement ◽  
Convincing Evidence ◽  
Constant Speed ◽  
Fluctuation Analysis ◽  
Common Belief ◽  
Variable Speed ◽  
Severity Scores ◽  
Anterior Posterior

Objective: To examine the hypothesis that constant speed is more comfortable than variable speed profiles and may minimize cybersickness. Background: Current best practices for virtual reality (VR) content creation suggest keeping any form of acceleration as short and infrequent as possible to mitigate cybersickness. Methods: In Experiment 1, participants experienced repetitions of simulated linear motion, and in Experiment 2, they experienced repetitions of a circular motion. Three speed profiles were tested in each experiment. Each trial lasted 2 min while standing. Cybersickness was measured using the Simulator Sickness Questionnaire (SSQ) and operationally defined in terms of total severity scores. Postural stability was measured using a Wii Balance Board and operationally defined in terms of center of pressure (COP) path length. Postural measures were decomposed into anterior-posterior and medial-lateral axes and subjected to detrended fluctuation analysis. Results: For both experiments, no significant differences were observed between the three speed profiles in terms of cybersickness or postural stability, and none of the baseline postural measures could predict SSQ scores for the speed profile conditions. An axis effect was observed in both experiments such that normalized COP movement was significantly greater along the anterior-posterior axis than the medial-lateral axis. Conclusion: Results showed no convincing evidence to support the common belief that constant speed is more comfortable than variable speed profiles for scenarios typical of VR applications. Application: The present findings offer guidelines for the design of locomotion techniques involving traversal in VR environments.

scholarly journals Effect of Toe Type on Static Balance in Ballet Dancers

2020 ◽  
Vol 35 (1) ◽  
pp. 35-41
Author(s):  
Momoko Kizawa ◽  
Toshito Yasuda ◽  
Hiroaki Shima ◽  
Katsunori Mori ◽  
Seiya Tsujinaka ◽  
...  
Keyword(s):  
Postural Stability ◽  
Center Of Pressure ◽  
Ground Reaction Forces ◽  
Bipedal Stance ◽  
Ballet Dancers ◽  
Maximum Range ◽  
Trajectory Length ◽  
Reaction Forces ◽  
Second Toe ◽  
Anterior Posterior

OBJECTIVES: Some forefoot shapes are ideal for pointe work in ballet. Egyptian-type, with the hallux being longest and the remaining toes decreasing in size, and Greek-type, with the second toe longer than the hallux, are considered less optimal for pointe work. Square-type, with the second toe the same length as the hallux, is considered optimal. This study compared postural stability in the bipedal stance, demi pointe, and en pointe between ballet dancers with the two toe types using a stabilometer. METHODS: This study included 25 Japanese ballet academy dancers who had received ballet lessons for at least 6 years. Toes were categorized into Egyptian-type (n=14) and square-type (n=11). Bipedal stance, demi pointe, and en pointe were tested. Center of pressure (COP) parameters were calculated from ground-reaction forces using two force plates: total trajectory length (LNG), velocities of anterior-posterior (VAP) and medial-lateral directions (VML), and maximum range displacement in the anterior-posterior (MAXAP) and medial-lateral directions (MAXML). Mann-Whitney U-tests were used to examine differences in COP parameters. RESULTS: There were no differences in parameters during bipedal stance or demi pointe. However, dancers with Egyptian-type toes had significantly greater LNG (p<0.01), VML (p=0.01), MAXML (p<0.01), and MAXAP (p=0.03) during en pointe. CONCLUSIONS: Ballet dancers with Egyptian-type toes demonstrated greater displacement in the medial-lateral and anterior-posterior directions during en pointe. Ballet dancers should be aware of toe types and sway character to optimize ballet training and balance.

scholarly journals Postural-Stability Tests That Identify Individuals With Chronic Ankle Instability

2014 ◽  
Vol 49 (1) ◽  
pp. 15-23 ◽  
Author(s):  
Shelley W. Linens ◽  
Scott E. Ross ◽  
Brent L. Arnold ◽  
Richard Gayle ◽  
Peter Pidcoe
Keyword(s):  
Postural Stability ◽  
Center Of Pressure ◽  
Ankle Instability ◽  
Force Plate ◽  
Area Under The Curve ◽  
Balance Test ◽  
Hop Test ◽  
Cutoff Scores ◽  
Star Excursion Balance Test ◽  
Anterior Posterior

Context: Chronic ankle instability (CAI) is characterized by repeated ankle sprains, which have been linked to postural instability. Therefore, it is important for clinicians to identify individuals with CAI who can benefit from rehabilitation. Objective: To assess the likelihood that CAI participants will exhibit impaired postural stability and that healthy control participants will exhibit better test performance values. Design: Case-control study. Setting: Laboratory. Patients or Other Participants: People with CAI (n = 17, age = 23 ± 4 years, height = 168 ± 9 cm, weight = 68 ± 12 kg) who reported ankle “giving-way” sensations and healthy volunteers (n = 17, age = 23 ± 3 years, height = 168 ± 8 cm, weight = 66 ± 12 kg). Intervention(s): Participants performed 7 balance tests: Balance Error Scoring System (BESS), time in balance, foot lift, single-legged stance on a force plate, Star Excursion Balance Test, side hop, and figure-of-8 hop. Main Outcome Measure(s): Balance was quantified with errors (score) for the BESS, length of time balancing (seconds) for time-in-balance test, frequency of foot lifts (score) for foot-lift test, velocity (cm/s) for all center-of-pressure velocity measures, excursion (cm) for center-of-pressure excursion measures, area (cm2) for 95% confidence ellipse center-of-pressure area and center-of-pressure rectangular area, time (seconds) for anterior-posterior and medial-lateral time-to-boundary (TTB) measures, distance reached (cm) for Star Excursion Balance Test, and time (seconds) to complete side-hop and figure-of-8 hop tests. We calculated area-under-the-curve values and cutoff scores and used the odds ratio to determine if those with and without CAI could be distinguished using cutoff scores. Results: We found significant area-under-the-curve values for 4 static noninstrumented measures, 3 force-plate measures, and 3 functional measures. Significant cutoff scores were noted for the time-in-balance test (≤25.89 seconds), foot-lift test (≥5), single-legged stance on the firm surface (≥3 errors) and total (≥14 errors) on the BESS, center-of-pressure resultant velocity (≥1.56 cm/s), standard deviations for medial-lateral (≤1.56 seconds) time-to-boundary and anterior-posterior (≤3.78 seconds) time-to-boundary test, posteromedial direction on the Star Excursion Balance Test (≤0.91), side-hop test (≥12.88 seconds), and figure-of-8 hop test (≥17.36 seconds). Conclusions: Clinicians can use any of the 10 significant measures with their associated cutoff scores to identify those who could benefit from rehabilitation that reestablishes postural stability.

Postural Stability Assessment of University Marching Musicians Using Force Platform Measures

2016 ◽  
Vol 31 (3) ◽  
pp. 174-178
Author(s):  
Trevor D Magnotti ◽  
Danielle McElhiney ◽  
Jeffrey A Russell
Keyword(s):  
Postural Stability ◽  
Center Of Pressure ◽  
Force Platform ◽  
Lower Extremity Injury ◽  
Assessment Protocol ◽  
Eyes Closed ◽  
Unstable Surface ◽  
Lateral Plane ◽  
Mean Differences ◽  
Anterior Posterior

Lower extremity injury is prevalent in marching musicians, and poor postural stability is a possible risk factor for this. The external load of an instrument may predispose these performers to injury by decreasing postural stability. The purpose of this study was to determine the relationship between instrument load and static and dynamic postural stability in this population. Fourteen university marching musicians were recruited and completed a balance assessment protocol on a force platform with and without their instrument. Mean center of pressure (CoP) displacement was then calculated for each exercise in the anterior/posterior and medial/lateral planes. Mean anterior/posterior CoP displacement significantly increased in the instrument condition for the static surface, eyes closed, 2 feet condition (p≤0.005; d=0.89). No significant differences were found in the medial/lateral plane between non-instrument and instrument conditions. Significant differences were not found between test stance conditions independent of group. Comparisons between the non-instrument-loaded and instrument-loaded conditions revealed possible significance of instrument load on postural stability in the anterior/posterior plane. Mean differences indicated that an unstable surface created a greater destabilizing effect on postural stability than instrument load.

scholarly journals Minimal shoes improve stability and mobility in persons with a history of falls

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Tomasz Cudejko ◽  
James Gardiner ◽  
Asangaedem Akpan ◽  
Kristiaan D’Août
Keyword(s):  
Fall Prevention ◽  
Postural Stability ◽  
Center Of Pressure ◽  
Stability Margin ◽  
Timed Up And Go ◽  
Balance Test ◽  
Margin Of Stability ◽  
Eyes Open ◽  
History Of ◽  
Falls In Older Adults

AbstractPostural and walking instabilities contribute to falls in older adults. Given that shoes affect human locomotor stability and that visual, cognitive and somatosensory systems deteriorate during aging, we aimed to: (1) compare the effects of footwear type on stability and mobility in persons with a history of falls, and (2) determine whether the effect of footwear type on stability is altered by the absence of visual input or by an additional cognitive load. Thirty participants performed standing and walking trials in three footwear conditions, i.e. conventional shoes, minimal shoes, and barefoot. The outcomes were: (1) postural stability (movement of the center of pressure during eyes open/closed), (2) walking stability (Margin of Stability during normal/dual-task walking), (3) mobility (the Timed Up and Go test and the Star Excursion Balance test), and (4) perceptions of the shoes (Monitor Orthopaedic Shoes questionnaire). Participants were more stable during standing and walking in minimal shoes than in conventional shoes, independent of visual or walking condition. Minimal shoes were more beneficial for mobility than conventional shoes and barefoot. This study supports the need for longitudinal studies investigating whether minimal footwear is more beneficial for fall prevention in older people than conventional footwear.

scholarly journals Effects of white Gaussian noise on dynamic balance in healthy young adults

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Ziyou Zhou ◽  
Can Wu ◽  
Zhen Hu ◽  
Yujuan Chai ◽  
Kai Chen ◽  
...  
Keyword(s):  
Young Adults ◽  
Gaussian Noise ◽  
Center Of Pressure ◽  
Dynamic Balance ◽  
White Gaussian Noise ◽  
Fluctuation Analysis ◽  
Balance Performance ◽  
Short Term ◽  
Crossover Point ◽  
Short Time

AbstractIt has been known that short-time auditory stimulation can contribute to the improvement of the balancing ability of the human body. The present study aims to explore the effects of white Gaussian noise (WGN) of different intensities and frequencies on dynamic balance performance in healthy young adults. A total of 20 healthy young participants were asked to stand at a dynamic balance force platform, which swung along the x-axis with an amplitude of ± 4° and frequency of 1 Hz. Their center of pressure (COP) trajectories were recorded when they were stimulated by WGN of different intensities (block 1) and different frequencies (block 2). A traditional method and detrended fluctuation analysis (DFA) were used for data preprocessing. The authors found that only with 75–85 dB WGN, the COP parameters improved. WGN frequency did not affect the dynamic balance performance of all the participants. The DFA results indicated stimulation with 75 dB WGN enhanced the short-term index and reduced the crossover point. Stimulation with 500 Hz and 2500 Hz WGN significantly enhanced the short-term index. These results suggest that 75 dB WGN and 500 Hz and 2500 Hz WGN improved the participants’ dynamic balance performance. The results of this study indicate that a certain intensity of WGN is indispensable to achieve a remarkable improvement in dynamic balance. The DFA results suggest that WGN only affected the short-term persistence, indicating the potential of WGN being considered as an adjuvant therapy in low-speed rehabilitation training.

“Going Backward”: Effects of age and fatigue on posterior-directed falls in Parkinson disease

2021 ◽  
pp. 1-9
Author(s):  
Evan V. Papa ◽  
Rita M. Patterson ◽  
Nicoleta Bugnariu
Keyword(s):  
Postural Control ◽  
Parkinson Disease ◽  
Repeated Measures ◽  
Center Of Pressure ◽  
Angular Displacement ◽  
Reaction Times ◽  
Older Individuals ◽  
Peak Knee ◽  
Significant Difference ◽  
Fatiguing Exercise

BACKGROUND: Nearly half of persons with Parkinson disease (PD) report fatigue as a factor in their fall history. However, it is unknown whether these self-reported falls are caused by a sensation of fatigue or performance fatigue. OBJECTIVE: We sought to investigate the influences of performance fatigue and age on postural control in persons with PD. METHODS: Individuals with PD (n = 14) underwent postural control assessments before (T0) and immediately after (T1) fatiguing exercise. Biomechanical data were gathered on participants completing a treadmill-induced, posterior-directed fall. Performance fatigue was produced using lower extremity resistance exercise on an isokinetic ergometer. Repeated measures ANCOVAs were used with age as a covariate to determine the effects of performance fatigue on biomechanical variables. RESULTS: After adjustment for age, there was a statistically significant difference in peak center of pressure (COP) latency during the support phase of recovery. Pairwise comparisons demonstrated a decrease in peak ankle displacement from T0 to T1. Age was also found to be significantly related to reaction time and peak knee displacement while participants were fatigued. CONCLUSIONS: The decreased peak COP latency, along with decreased ankle angular displacement, suggest that persons with PD adopt a stiffening strategy in response to backward directed falls. Postural stiffening is not uncommon in persons with PD and could be a risk factor for falls. Older individuals with PD demonstrate slower mobility scores and decreased reaction times in the setting of fatigue, suggesting a combined effect of the aging and fatigue processes.

Comparing Standing Balance at Real and Virtual Elevated Environments

2002 ◽  
Vol 46 (26) ◽  
pp. 2169-2173
Author(s):  
Peter Simeonov ◽  
Hongwei Hsiao ◽  
Brian Dotson ◽  
Douglas Amnions
Keyword(s):  
Postural Balance ◽  
Occupational Safety ◽  
Center Of Pressure ◽  
Ground Level ◽  
Occupational Safety And Health ◽  
Visual Simulation ◽  
Mean Velocity ◽  
Deformable Surfaces ◽  
Safety And Health ◽  
Anterior Posterior

The study evaluated the efficacy of a surround-screen virtual reality (SSVR) system in simulating heights for studying human postural balance at elevation. Twenty four subjects performed standing tasks at 9-m elevation and ground level, on firm and deformable surfaces, in a real environment (RE) and a comparable virtual environment (VE). The RE was the interior of the high-bay laboratory at the National Institute for Occupational Safety and Health (NIOSH) in Morgantown, West Virginia; the VE simulated this environment in the SSVR system. Medial-lateral and anterior-posterior body sways and mean velocity of the human center-of-pressure displacement were collected using a force platform. The results indicated that the sway parameters were similar in VE and RE at elevation on both firm and deformable surfaces. At ground level, the sway parameters were significantly increased in the VE compared to the RE on a deformable surface, but not on a firm surface. It appears that visual simulation of elevated environments within a SSVR is adequate for studying the risk factors leading to losing balance and fall incidents.

Effects of Hand Vibration on Postural Stability

1992 ◽  
Vol 36 (10) ◽  
pp. 765-769
Author(s):  
Lisa Fletcher ◽  
Hee-Seok Park ◽  
Bernard J Martin
Keyword(s):  
Risk Factor ◽  
Postural Stability ◽  
Center Of Pressure ◽  
Environmental Context ◽  
Proprioceptive Information ◽  
Vibration Exposure ◽  
Dominant Hand ◽  
Erect Posture ◽  
Spatial Reference ◽  
Eyes Closed

The present work was aimed at defining the contribution of vibration-induced perturbation of hand proprioceptive/exteroceptive feedback on standing equilibrium. A vibrating handle, free in space or fixed to a stationary support, was held in the dominant hand while maintaining an erect posture on a force platform, eyes closed. Four arm positions were used. The results show that body sways increase significantly during hand vibration exposure when the handle is fixed. Significant shifts of the center of pressure COP are elicited in every situations. Furthermore, the shifts of the COP are clearly oriented in the direction of the handle when this latter is fixed. It is suggested that the proprioceptive information issued from the hand contributes to the elaboration of a spatial reference and to the control of posture as a function of the environmental context. These results indicate that hand vibration exposure can be considered as a risk factor which may contribute to fall accidents.

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