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Shafahi, Ali, Mahyar Najibi, Zheng Xu, John Dickerson, Larry S. Davis, and Tom Goldstein. "Universal Adversarial Training." Proceedings of the AAAI Conference on Artificial Intelligence 34, no. 04 (April 3, 2020): 5636–43. http://dx.doi.org/10.1609/aaai.v34i04.6017.
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Standard adversarial attacks change the predicted class label of a selected image by adding specially tailored small perturbations to its pixels. In contrast, a universal perturbation is an update that can be added to any image in a broad class of images, while still changing the predicted class label. We study the efficient generation of universal adversarial perturbations, and also efficient methods for hardening networks to these attacks. We propose a simple optimization-based universal attack that reduces the top-1 accuracy of various network architectures on ImageNet to less than 20%, while learning the universal perturbation 13× faster than the standard method.To defend against these perturbations, we propose universal adversarial training, which models the problem of robust classifier generation as a two-player min-max game, and produces robust models with only 2× the cost of natural training. We also propose a simultaneous stochastic gradient method that is almost free of extra computation, which allows us to do universal adversarial training on ImageNet.
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Gorman, Jamie C., Nancy J. Cooke, and Polemnia G. Amazeen. "Training Adaptive Teams." Human Factors: The Journal of the Human Factors and Ergonomics Society 52, no. 2 (April 2010): 295–307. http://dx.doi.org/10.1177/0018720810371689.
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Objective: We report an experiment in which three training approaches are compared with the goal of training adaptive teams. Background: Cross-training is an established method in which team members are trained with the goal of building shared knowledge. Perturbation training is a new method in which team interactions are constrained to provide new coordination experiences during task acquisition. These two approaches, and a more traditional procedural approach, are compared. Method: Assigned to three training conditions were 26 teams. Teams flew nine simulated uninhabited air vehicle missions; three were critical tests of the team’s ability to adapt to novel situations. Team performance, response time to novel events, and shared knowledge were measured. Results: Perturbation-trained teams significantly outperformed teams in the other conditions in two out of three critical test missions. Cross-training resulted in significant increases in shared teamwork knowledge and highest mean performance in one critical test. Procedural training led to the least adaptive teams. Conclusion: Perturbation training allows teams to match coordination variability during training to demands for coordination variability during posttraining performance. Although cross-training has adaptive benefits, it is suggested that process-oriented approaches, such as perturbation training, can lead to more adaptive teams. Application: Perturbation training is amenable to simulation-based training, where perturbations provide interaction experiences that teams can transfer to novel, real-world situations.
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Burne, Graham, and Christopher Tack. "Overhead Perturbation Training." Strength and Conditioning Journal 39, no. 3 (June 2017): 87–93. http://dx.doi.org/10.1519/ssc.0000000000000280.
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Dusane, Shamali, and Tanvi Bhatt. "Mixed slip-trip perturbation training for improving reactive responses in people with chronic stroke." Journal of Neurophysiology 124, no. 1 (July 1, 2020): 20–31. http://dx.doi.org/10.1152/jn.00671.2019.
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Block perturbation training led to development of favorable reactive responses to counteract treadmill-based, slip-like and trip-like stance perturbations among people with chronic stroke. During mixed block, previously acquired adaptive changes in reactive responses from slip-block training were not maintained, probably due to interference offered by trip block. Instead, on trip-like perturbations, trip block-induced adaptation was maintained and continued to show further improvement. Our findings might provide future direction for designing effective mixed perturbation training paradigms to counteract both opposing perturbation types.
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Taylor, Jeffrey B. "Lower Extremity Perturbation Training." Strength and Conditioning Journal 33, no. 2 (April 2011): 76–83. http://dx.doi.org/10.1519/ssc.0b013e318211aaaa.
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Mansfield, Avril, Amy L. Peters, Barbara A. Liu, and Brian E. Maki. "Effect of a Perturbation-Based Balance Training Program on Compensatory Stepping and Grasping Reactions in Older Adults: A Randomized Controlled Trial." Physical Therapy 90, no. 4 (April 1, 2010): 476–91. http://dx.doi.org/10.2522/ptj.20090070.
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BackgroundCompensatory stepping and grasping reactions are prevalent responses to sudden loss of balance and play a critical role in preventing falls. The ability to execute these reactions effectively is impaired in older adults.ObjectiveThe purpose of this study was to evaluate a perturbation-based balance training program designed to target specific age-related impairments in compensatory stepping and grasping balance recovery reactions.DesignThis was a double-blind randomized controlled trial.SettingThe study was conducted at research laboratories in a large urban hospital.ParticipantsThirty community-dwelling older adults (aged 64–80 years) with a recent history of falls or self-reported instability participated in the study.InterventionParticipants were randomly assigned to receive either a 6-week perturbation-based (motion platform) balance training program or a 6-week control program involving flexibility and relaxation training.MeasurementsFeatures of balance reactions targeted by the perturbation-based program were: (1) multi-step reactions, (2) extra lateral steps following anteroposterior perturbations, (3) foot collisions following lateral perturbations, and (4) time to complete grasping reactions. The reactions were evoked during testing by highly unpredictable surface translation and cable pull perturbations, both of which differed from the perturbations used during training.ResultsCompared with the control program, the perturbation-based training led to greater reductions in frequency of multi-step reactions and foot collisions that were statistically significant for surface translations but not cable pulls. The perturbation group also showed significantly greater reduction in handrail contact time compared with the control group for cable pulls and a possible trend in this direction for surface translations.LimitationsFurther work is needed to determine whether a maintenance program is needed to retain the training benefits and to assess whether these benefits reduce fall risk in daily life.ConclusionPerturbation-based training shows promise as an effective intervention to improve the ability of older adults to prevent themselves from falling when they lose their balance.
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Epro, G., A. Mierau, C. McCrum, M. Leyendecker, G. P. Brüggemann, and K. Karamanidis. "Retention of gait stability improvements over 1.5 years in older adults: effects of perturbation exposure and triceps surae neuromuscular exercise." Journal of Neurophysiology 119, no. 6 (June 1, 2018): 2229–40. http://dx.doi.org/10.1152/jn.00513.2017.
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The plantarflexors play a crucial role in recovery from sudden disturbances to gait. The objective of this study was to investigate whether medium (months)- or long(years)-term exercise-induced enhancement of triceps surae (TS) neuromuscular capacities affects older adults’ ability to retain improvements in reactive gait stability during perturbed walking acquired from perturbation training sessions. Thirty-four adult women (65 ± 7 yr) were recruited to a perturbation training group ( n = 13) or a group that additionally completed 14 wk of TS neuromuscular exercise ( n = 21), 12 of whom continued with the exercise for 1.5 yr. The margin of stability (MoS) was analyzed at touchdown of the perturbed step and the first recovery step following eight separate unexpected trip perturbations during treadmill walking. TS muscle-tendon unit mechanical properties and motor skill performance were assessed with ultrasonography and dynamometry. Two perturbation training sessions (baseline and after 14 wk) caused an improvement in the reactive gait stability to the perturbations (increased MoS) in both groups. The perturbation training group retained the reactive gait stability improvements acquired over 14 wk and over 1.5 yr, with a minor decay over time. Despite the improvements in TS capacities in the additional exercise group, no benefits for the reactive gait stability following perturbations were identified. Therefore, older adults’ neuromotor system shows rapid plasticity to repeated unexpected perturbations and an ability to retain these adaptations in reactive gait stability over a long time period, but an additional exercise-related enhancement of TS capacities seems not to further improve these effects. NEW & NOTEWORTHY Older adults’ neuromotor system shows rapid plasticity to repeated exposure to unexpected perturbations to gait and an ability to retain the majority of these adaptations in reactive recovery responses over a prolonged time period of 1.5 yr. However, an additional exercise-related enhancement of TS neuromuscular capacities is not necessarily transferred to the recovery behavior during unexpected perturbations to gait in older adults.
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Gorman, Jamie C., Nancy J. Cooke, Jennifer L. Winner, Jasmine L. Duran, Harry K. Pedersen, and Amanda R. Taylor. "Knowledge Training versus Process Training: The Effects of Training Protocol on Team Coordination and Performance." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 51, no. 4 (October 2007): 382–86. http://dx.doi.org/10.1177/154193120705100449.
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Three-person teams controlling a simulated unmanned aerial vehicle underwent different training regimes in order to assess the effect of process-based and knowledge-based training on team coordination and performance. Coordination and performance were assessed during training and eight to eleven weeks after training. Process training consisted of either enforcing a rigid coordination process or forcing teams to coordinate in different ways through the introduction of perturbations. Knowledge training consisted of cross-training teams on each others roles. Results indicate that process training had a significant effect on team coordination. In addition, the qualitative nature of coordination flexibility changed from training to retention for process versus knowledge trained teams, with process teams behaving flexibly at retention. Perturbation process training led to significantly higher team performance under high workload. Rigid process training lead to significantly lower performance in one of the retention missions.
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Ramakrishnan, Ramya, Chongjie Zhang, and Julie Shah. "Perturbation Training for Human-Robot Teams." Journal of Artificial Intelligence Research 59 (July 31, 2017): 495–541. http://dx.doi.org/10.1613/jair.5390.
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In this work, we design and evaluate a computational learning model that enables a human-robot team to co-develop joint strategies for performing novel tasks that require coordination. The joint strategies are learned through "perturbation training," a human team-training strategy that requires team members to practice variations of a given task to help their team generalize to new variants of that task. We formally define the problem of human-robot perturbation training and develop and evaluate the first end-to-end framework for such training, which incorporates a multi-agent transfer learning algorithm, human-robot co-learning framework and communication protocol. Our transfer learning algorithm, Adaptive Perturbation Training (AdaPT), is a hybrid of transfer and reinforcement learning techniques that learns quickly and robustly for new task variants. We empirically validate the benefits of AdaPT through comparison to other hybrid reinforcement and transfer learning techniques aimed at transferring knowledge from multiple source tasks to a single target task. We also demonstrate that AdaPT's rapid learning supports live interaction between a person and a robot, during which the human-robot team trains to achieve a high level of performance for new task variants. We augment AdaPT with a co-learning framework and a computational bi-directional communication protocol so that the robot can co-train with a person during live interaction. Results from large-scale human subject experiments (n=48) indicate that AdaPT enables an agent to learn in a manner compatible with a human's own learning process, and that a robot undergoing perturbation training with a human results in a high level of team performance. Finally, we demonstrate that human-robot training using AdaPT in a simulation environment produces effective performance for a team incorporating an embodied robot partner.
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Silkman, Carrie, Matthew Hoch, and Jennifer McKeon. "Perturbation Training Prior to ACL Reconstruction." Athletic Therapy Today 15, no. 3 (May 2010): 11–13. http://dx.doi.org/10.1123/att.15.3.11.
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Lee, Anna, Tanvi Bhatt, Xuan Liu, Yiru Wang, Shuaijie Wang, and Yi-Chung (Clive) Pai. "Can Treadmill Slip-Perturbation Training Reduce Longer-Term Fall Risk Upon Overground Slip Exposure?" Journal of Applied Biomechanics 36, no. 5 (October 1, 2020): 298–306. http://dx.doi.org/10.1123/jab.2019-0211.
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The purpose was to examine and compare the longer-term generalization between 2 different practice dosages for a single-session treadmill slip-perturbation training when reexposed to an overground slip 6 months later. A total of 45 older adults were conveniently assigned to either 24 or 40 slip-like treadmill perturbation trials or a third control group. Overground slips were given immediately after initial training, and at 6 months after initial training in order to examine immediate and longer-term effects. The performance (center of mass stability and vertical limb support) and fall percentage from the laboratory-induced overground slips (at initial posttraining and at 6 mo) were measured and compared between groups. Both treadmill slip-perturbation groups showed immediate generalization at the initial posttraining test and longer-term generalization at the 6-month retest. The higher-practice-dosage group performed significantly better than the control group (P < .05), with no difference between the lower-practice-dosage and the control groups at the 6-month retest (P > .05). A single session of treadmill slip-perturbation training showed a positive effect for reducing older adults’ fall risk for laboratory-induced overground slips. A higher-practice dosage of treadmill slip perturbations could be more beneficial for further reducing fall risk.
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Mansfield, Avril, Jennifer S. Wong, Jessica Bryce, Svetlana Knorr, and Kara K. Patterson. "Does Perturbation-Based Balance Training Prevent Falls? Systematic Review and Meta-Analysis of Preliminary Randomized Controlled Trials." Physical Therapy 95, no. 5 (May 1, 2015): 700–709. http://dx.doi.org/10.2522/ptj.20140090.
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BackgroundOlder adults and individuals with neurological conditions are at an increased risk for falls. Although physical exercise can prevent falls, certain types of exercise may be more effective. Perturbation-based balance training is a novel intervention involving repeated postural perturbations aiming to improve control of rapid balance reactions.PurposeThe purpose of this study was to estimate the effect of perturbation-based balance training on falls in daily life.Data SourcesMEDLINE (1946–July 2014), EMBASE (1974–July 2014), PEDro (all dates), CENTRAL (1991–July 2014), and Google Scholar (all dates) were the data sources used in this study.Study SelectionRandomized controlled trials written in English were included if they focused on perturbation-based balance training among older adults or individuals with neurological conditions and collected falls data posttraining.Data ExtractionTwo investigators extracted data independently. Study authors were contacted to obtain missing information. A PEDro score was obtained for each study. Primary outcomes were proportion of participants who reported one or more falls (ie, number of “fallers”) and the total number of falls. The risk ratio (proportion of fallers) and rate ratio (number of falls) were entered into the analysis.>Data SynthesisEight studies involving 404 participants were included. Participants who completed perturbation-based balance training were less likely to report a fall (overall risk ratio=0.71; 95% confidence interval=0.52, 0.96; P=.02) and reported fewer falls than those in the control groups (overall rate ratio=0.54; 95% confidence interval=0.34, 0.85; P=.007).LimitationsStudy authors do not always identify that they have included perturbation training in their intervention; therefore, it is possible that some appropriate studies were not included. Study designs were heterogeneous, preventing subanalyses.ConclusionsPerturbation-based balance training appears to reduce fall risk among older adults and individuals with Parkinson disease.
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Chander, Harish, Sachini N. K. Kodithuwakku Arachchige, Christopher M. Hill, Alana J. Turner, Shuchisnigdha Deb, Alireza Shojaei, Christopher Hudson, Adam C. Knight, and Daniel W. Carruth. "Virtual-Reality-Induced Visual Perturbations Impact Postural Control System Behavior." Behavioral Sciences 9, no. 11 (November 12, 2019): 113. http://dx.doi.org/10.3390/bs9110113.
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Background: Virtual reality (VR) is becoming a widespread tool in rehabilitation, especially for postural stability. However, the impact of using VR in a “moving wall paradigm” (visual perturbation), specifically without and with anticipation of the perturbation, is unknown. Methods: Nineteen healthy subjects performed three trials of static balance testing on a force plate under three different conditions: baseline (no perturbation), unexpected VR perturbation, and expected VR perturbation. The statistical analysis consisted of a 1 × 3 repeated-measures ANOVA to test for differences in the center of pressure (COP) displacement, 95% ellipsoid area, and COP sway velocity. Results: The expected perturbation rendered significantly lower (p < 0.05) COP displacements and 95% ellipsoid area compared to the unexpected condition. A significantly higher (p < 0.05) sway velocity was also observed in the expected condition compared to the unexpected condition. Conclusions: Postural stability was lowered during unexpected visual perturbations compared to both during baseline and during expected visual perturbations, suggesting that conflicting visual feedback induced postural instability due to compensatory postural responses. However, during expected visual perturbations, significantly lowered postural sway displacement and area were achieved by increasing the sway velocity, suggesting the occurrence of postural behavior due to anticipatory postural responses. Finally, the study also concluded that VR could be used to induce different postural responses by providing visual perturbations to the postural control system, which can subsequently be used as an effective and low-cost tool for postural stability training and rehabilitation.
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König, Matthias, Gaspar Epro, John Seeley, Wolfgang Potthast, and Kiros Karamanidis. "Retention and generalizability of balance recovery response adaptations from trip perturbations across the adult life span." Journal of Neurophysiology 122, no. 5 (November 1, 2019): 1884–93. http://dx.doi.org/10.1152/jn.00380.2019.
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For human locomotion, varying environments require adjustments of the motor system. We asked whether age affects gait balance recovery adaptation, its retention over months, and the transfer of adaptation to an untrained reactive balance task. Healthy adults (26 young, 27 middle-aged, and 25 older; average ages 24, 52, and 72 yr, respectively) completed two tasks. The primary task involved treadmill walking: either unperturbed (control; n = 39) or subject to unexpected trip perturbations (training; n = 39). A single trip perturbation was repeated after a 14-wk retention period. The secondary transfer task, before and after treadmill walking, involved sudden loss of balance in a lean-and-release protocol. For both tasks, the anteroposterior margin of stability (MoS) was calculated at foot touchdown. For the first (i.e., novel) trip, older adults required one more recovery step ( P = 0.03) to regain positive MoS compared with younger, but not middle-aged, adults. However, over several trip perturbations, all age groups increased their MoS for the first recovery step to a similar extent (up to 70%) and retained improvements over 14 wk, although a decay over time was found for older adults ( P = 0.002; middle-aged showing a tendency for decay: P = 0.076). Thus, although adaptability in reactive gait stability control remains effective across the adult life span, retention of adaptations over time appears diminished with aging. Despite these robust adaptations, the perturbation training group did not show superior improvements in the transfer task compared with age-matched controls (no differences in MoS changes), suggesting that generalizability of acquired fall-resisting skills from gait-perturbation training may be limited. NEW & NOTEWORTHY The human neuromotor system preserves its adaptability across the adult life span. However, although adaptability in reactive gait stability control remains effective as age increases, retention of recovery response adaptations over time appears to be reduced with aging. Furthermore, acquired fall-resisting skills from single-session perturbation training seem task specific, which may limit the generalizability of such training to the variety of real-life falls.
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Sheehan, Riley C., Christopher A. Rábago, Jonathan H. Rylander, Jonathan B. Dingwell, and Jason M. Wilken. "Use of Perturbation-Based Gait Training in a Virtual Environment to Address Mediolateral Instability in an Individual With Unilateral Transfemoral Amputation." Physical Therapy 96, no. 12 (December 1, 2016): 1896–904. http://dx.doi.org/10.2522/ptj.20150566.
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Abstract Background and Purpose Roughly 50% of individuals with lower limb amputation report a fear of falling and fall at least once a year. Perturbation-based gait training and the use of virtual environments have been shown independently to be effective at improving walking stability in patient populations. An intervention was developed combining the strengths of the 2 paradigms utilizing continuous, walking surface angle oscillations within a virtual environment. This case report describes walking function and mediolateral stability outcomes of an individual with a unilateral transfemoral amputation following a novel perturbation-based gait training intervention in a virtual environment. Case Description The patient was a 43-year-old male veteran who underwent a right transfemoral amputation 7+ years previously as a result of a traumatic blast injury. He used a microprocessor-controlled knee and an energy storage and return foot. Outcomes Following the intervention, multiple measures indicated improved function and stability, including faster self-selected walking speed and reduced functional stepping time, mean step width, and step width variability. These changes were seen during normal level walking and mediolateral visual field or platform perturbations. In addition, benefits were retained at least 5 weeks after the final training session. Discussion The perturbation-based gait training program in the virtual environment resulted in the patient's improved walking function and mediolateral stability. Although the patient had completed intensive rehabilitation following injury and was fully independent, the intervention still induced notable improvements to mediolateral stability. Thus, perturbation-based gait training in challenging simulated environments shows promise for improving walking stability and may be beneficial when integrated into a rehabilitation program.
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Rogers, Mark W., Robert A. Creath, Vicki Gray, Janice Abarro, Sandy McCombe Waller, Brock A. Beamer, and John D. Sorkin. "Comparison of Lateral Perturbation-Induced Step Training and Hip Muscle Strengthening Exercise on Balance and Falls in Community-Dwelling Older Adults: A Blinded Randomized Controlled Trial." Journals of Gerontology: Series A 76, no. 9 (February 6, 2021): e194-e202. http://dx.doi.org/10.1093/gerona/glab017.
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Abstract Background This factorial, assessor-blinded, randomized, and controlled study compared the effects of perturbation-induced step training (lateral waist-pulls), hip muscle strengthening, and their combination, on balance performance, muscle strength, and prospective falls among older adults. Methods Community-dwelling older adults were randomized to 4 training groups. Induced step training (IST, n = 25) involved 43 progressive perturbations. Hip abduction strengthening (HST, n = 25) utilized progressive resistance exercises. Combined training (CMB, n = 25) included IST and HST, and the control performed seated flexibility/relaxation exercises (SFR, n = 27). The training involved 36 sessions for a period of 12 weeks. The primary outcomes were the number of recovery steps and first step length, and maximum hip abduction torque. Fall frequency during 12 months after training was determined. Results Overall, the number of recovery steps was reduced by 31% and depended upon the first step type. IST and CMB increased the rate of more stable single lateral steps pre- and post-training than HST and SFR who used more multiple crossover and sequential steps. The improved rate of lateral steps for CMB exceeded the control (CMB/SFR rate ratio 2.68). First step length was unchanged, and HST alone increased hip torque by 25%. Relative to SFR, the fall rate ratios (falls/person/year) [95% confidence interval] were CMB 0.26 [0.07–0.90], IST 0.44 [0.18–1.08], and HST 0.30 (0.10–0.91). Conclusions Balance performance through stepping was best improved by combining perturbation and strength training and not strengthening alone. The interventions reduced future falls by 56%–74% over the control. Lateral balance perturbation training may enhance traditional programs for fall prevention.
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Jakobsen, Markus D., Emil Sundstrup, Mikkel Brandt, Kenneth Jay, Per Aagaard, and Lars L. Andersen. "Effect of Workplace- versus Home-Based Physical Exercise on Muscle Response to Sudden Trunk Perturbation among Healthcare Workers: A Cluster Randomized Controlled Trial." BioMed Research International 2015 (2015): 1–11. http://dx.doi.org/10.1155/2015/902896.
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Objectives. The present study investigates the effect of workplace- versus home-based physical exercise on muscle reflex response to sudden trunk perturbation among healthcare workers.Methods. Two hundred female healthcare workers (age: 42 [SD 11], BMI: 24 [SD 4], and pain intensity: 3.1 [SD 2.2] on a scale of 0–10) from 18 departments at three hospitals were randomized at the cluster level to 10 weeks of (1) workplace physical exercise (WORK) performed in groups during working hours for 5×10 minutes per week and up to 5 group-based coaching sessions on motivation for regular physical exercise, or (2) home-based physical exercise (HOME) performed during leisure time for 5×10 minutes per week. Mechanical and neuromuscular (EMG) response to randomly assigned unloading and loading trunk perturbations and questions of fear avoidance were assessed at baseline and 10-week follow-up.Results. Nogroup by timeinteraction for the mechanical trunk response and EMG latency time was seen following the ten weeks (P= 0.17–0.75). However, both groups demonstrated within-group changes (P<0.05) in stopping time during the loading and unloading perturbation and in stopping distance during the loading perturbation. Furthermore, EMG preactivation of the erector spinae and fear avoidance were reduced more following WORK than HOME (95% CI −2.7–−0.7 (P<0.05) and −0.14 (−0.30 to 0.02) (P=0.09)), respectively. WORK and HOME performed 2.2 (SD: 1.1) and 1.0 (SD: 1.2) training sessions per week, respectively.Conclusions. Although training adherence was higher following WORK compared to HOME this additional training volume did not lead to significant between-group differences in the responses to sudden trunk perturbations. However, WORK led to reduced fear avoidance and reduced muscle preactivity prior to the perturbation onset, compared with HOME. This trial is registered with Clinicaltrials.gov (NCT01921764).
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Mynark, Richard G., and David M. Koceja. "Down training of the elderly soleus H reflex with the use of a spinally induced balance perturbation." Journal of Applied Physiology 93, no. 1 (July 1, 2002): 127–33. http://dx.doi.org/10.1152/japplphysiol.00007.2001.
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The purpose of this study was to determine the ability of the elderly central nervous system to modulate spinal reflex output to functionally decrease a spinally induced balance perturbation. In this case, the soleus H reflex was used as the source of perturbation. Therefore, decreasing (down training) of the soleus H reflex was necessary to counteract this perturbation and to better maintain postural control. In addition to assessing the effect of this perturbation on the H reflex, static postural stability was measured to evaluate possible functional effects. Ten healthy young subjects (age: 27.0 ± 4.6 yr) and 10 healthy elderly subjects (age: 71.4 ± 5.1 yr) participated in this study. Subjects underwent balance perturbation on 2 consecutive days. On day 1 of perturbation, significant down training of the soleus H reflex was demonstrated in both young (−20.4%) and elderly (−18.7%) subjects. On day 2 of perturbation, significant down training of the soleus H reflex was again demonstrated in both young (−24.6%) and elderly (−21.0%) subjects. Analysis of static stability after the 2 days of balance perturbation revealed a significant 10.1% decrease in the area of sway in elderly subjects. In conclusion, this study demonstrated that healthy, elderly subjects compared with young subjects were equally capable of down training the soleus H reflex in response to a balance perturbation. Furthermore, the improvement in static stability through balance training may provide further evidence that balance can be retrained and rehabilitated in subjects with decreased reflex function.
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Guzy, Lawrence T., William B. Albery, and Chuck Goodyear. "Vibrotactile stimulators and virtual 3-D audio countermeasures, training and motion sickness symptoms with a simulated graveyard spin illusion." Journal of Vestibular Research 18, no. 5-6 (April 1, 2009): 287–94. http://dx.doi.org/10.3233/ves-2008-185-605.
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The vestibular system by itself is incapable of effectively compensating for the graveyard spin illusion. We examined two countermeasures, i.e., efficacy of vibrotactile stimulation around the waist and virtual 3-D audio presented independently and jointly for controlling a simulated graveyard spin. We also examined: a) additional training with these countermeasures to improve "intuitiveness;" b) included non-perturbation trials along with perturbation trials; and c) monitored changes in well-being as measured by a motion sickness scale from pre- to post-test and immediately following each trial. Ten volunteers received two training and two test sessions. The somatogyral illusion was generated by accelerating a chair for 24 s until it attained a peak rotation of 120°/s and then stopped. Over the ensuing 40 s the chair rotated in one of two random perturbation patterns or remained stationary. During this period, participants were required to eliminate all movements of the chair by turning a knob in the opposite direction of perceived rotation. For the control trials, participants relied solely on vestibular signals to cancel perceived movements. For the experimental trials, vibrotactile stimulation around the waist, virtual 3-D audio, or both were presented. The mean Cancellation Error (CE) for the control trials was 52°/s. The application of the countermeasures significantly reduced the CE. Additional training and testing did not improve intuitiveness. Perturbations to the chair resulted in a higher CE than no perturbations. Motion sickness symptoms showed no differences from pre- to post-test and very rarely reported after each trial.
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EsmaeiliMahani, V., L. Bouyer, D. Kairy, A. Lamontagne, J. O. Dyer, and C. Duclos. "Unpredictable gait perturbation training improves balance and gait abilities more than gait training without perturbations in individuals post-stroke." Annals of Physical and Rehabilitation Medicine 61 (July 2018): e212-e213. http://dx.doi.org/10.1016/j.rehab.2018.05.491.
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Fitzgerald, G. Kelley, Michael J. Axe, and Lynn Snyder-Mackler. "The Efficacy of Perturbation Training in Nonoperative Anterior Cruciate Ligament Rehabilitation Programs for Physically Active Individuals." Physical Therapy 80, no. 2 (February 1, 2000): 128–40. http://dx.doi.org/10.1093/ptj/80.2.128.
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AbstractBackground and Purpose. Treatment techniques involving perturbations of support surfaces may induce compensatory muscle activity that could improve knee stability and increase the likelihood of returning patients to high-level physical activity. The purpose of this study was to determine the efficacy of augmenting standard nonoperative anterior cruciate ligament (ACL) rehabilitation programs with a perturbation training program. Subjects. Twenty-six patients with an acute ACL injury or ruptures of ACL grafts participated in the study. Subjects had to have a unilateral ACL injury, be free of concomitant multiple ligament or meniscal damage requiring surgical repair, and pass a screening examination designed to identify patients who had the potential to return to high-level physical activity with nonoperative treatments. Subjects also had to be regular participants in level I activities (eg, soccer, football, basketball) or level II activities (eg, racquet sports, skiing, construction work). Methods. Subjects were randomly assigned to either a group that received a standard rehabilitation program (standard group) or a group that received the standard program augmented with a perturbation training program (perturbation group). Treatment outcome was determined from scores on the Knee Outcome Survey's Activities of Daily Living Scale (ADLS) and Sports Activity Scale, a global rating of knee function, scores on a series of single-limb hop tests, measurements of maximum isometric quadriceps femoris muscle force output, and the group frequency of unsuccessful rehabilitation. Unsuccessful rehabilitation was defined as the occurrence of an episode of giving way of the knee or failure to maintain the functional status of a rehabilitation candidate on retesting. Results. More subjects had unsuccessful rehabilitation in the standard group compared with the perturbation group. There was a within-group × time interaction for the ADLS, global rating of knee function, and crossover hop test scores. These scores decreased from posttraining to the 6-month follow-up for the standard group. Conclusion and Discussion. Although both the standard program and the perturbation training program may allow subjects to return to high-level physical activity, the perturbation training program appears to reduce the risk of continued episodes of giving way of the knee during athletic participation, and it allows subjects to maintain their functional status for longer periods.
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González-Díaz, Humberto, Lázaro G. Pérez-Montoto, and Florencio M. Ubeira. "Model for Vaccine Design by Prediction of B-Epitopes of IEDB Given Perturbations in Peptide Sequence, In Vivo Process, Experimental Techniques, and Source or Host Organisms." Journal of Immunology Research 2014 (2014): 1–15. http://dx.doi.org/10.1155/2014/768515.
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Perturbation methods add variation terms to a known experimental solution of one problem to approach a solution for a related problem without known exact solution. One problem of this type in immunology is the prediction of the possible action of epitope of one peptide after a perturbation or variation in the structure of a known peptide and/or other boundary conditions (host organism, biological process, and experimental assay). However, to the best of our knowledge, there are no reports of general-purpose perturbation models to solve this problem. In a recent work, we introduced a new quantitative structure-property relationship theory for the study of perturbations in complex biomolecular systems. In this work, we developed the first model able to classify more than 200,000 cases of perturbations with accuracy, sensitivity, and specificity >90% both in training and validation series. The perturbations include structural changes in >50000 peptides determined in experimental assays with boundary conditions involving >500 source organisms, >50 host organisms, >10 biological process, and >30 experimental techniques. The model may be useful for the prediction of new epitopes or the optimization of known peptides towards computational vaccine design.
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Liu, Jian, Miaozong Wu, James McIntosh, and Yi-Po Chiu. "Aging Effect on Gait Symmetry After Perturbation Training." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 60, no. 1 (September 2016): 1027–30. http://dx.doi.org/10.1177/1541931213601238.
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Fall accident is a growing concern for the aging workforce. Reducing fall injuries has been identified as a primary strategic goal in the National Occupational Research Agenda. The objective of the study was to investigate the interaction effect between aging and a novel Automated Walkway Surface Perturbation Training (AWSPT) on kinematic gait asymmetry. Five older adults and five gender-matched younger adults were involved in a laboratory study. Three- dimensional linear accelerations of left and right knee joints were measured via two Inertial Measurement Units (IMUs) during both before and after training sessions. Gait asymmetry was quantified by the percentage difference between peak knee resultant acceleration normalized to the average peak knee resultant acceleration. The results indicated significant training effect on Gait Asymmetry Index (GAI). Neither the interaction effect nor the aging effect was found to be significant. In conclusion, the current study provided evidence supporting the effectiveness of AWSPT in improving gait symmetry during normal walking. Such findings support the potential application of AWSPT in reducing risk of falling as well as in gait rehabilitation.
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Nawasreh, Zakariya, David Logerstedt, Mathew Failla, and Lynn Snyder-Mackler. "No difference between mechanical perturbation training with compliant surface and manual perturbation training on knee functional performance after ACL rupture." Journal of Orthopaedic Research® 36, no. 5 (November 28, 2017): 1391–97. http://dx.doi.org/10.1002/jor.23784.
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Howard, Ian S., James N. Ingram, and Daniel M. Wolpert. "Context-Dependent Partitioning of Motor Learning in Bimanual Movements." Journal of Neurophysiology 104, no. 4 (October 2010): 2082–91. http://dx.doi.org/10.1152/jn.00299.2010.
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Human subjects easily adapt to single dynamic or visuomotor perturbations. In contrast, when two opposing dynamic or visuomotor perturbations are presented sequentially, interference is often observed. We examined the effect of bimanual movement context on interference between opposing perturbations using pairs of contexts, in which the relative direction of movement between the two arms was different across the pair. When each perturbation direction was associated with a different bimanual context, such as movement of the arms in the same direction versus movement in the opposite direction, interference was dramatically reduced. This occurred over a short period of training and was seen for both dynamic and visuomotor perturbations, suggesting a partitioning of motor learning for the different bimanual contexts. Further support for this was found in a series of transfer experiments. Having learned a single dynamic or visuomotor perturbation in one bimanual context, subjects showed incomplete transfer of this learning when the context changed, even though the perturbation remained the same. In addition, we examined a bimanual context in which one arm was moved passively and show that the reduction in interference requires active movement. The sensory consequences of movement are thus insufficient to allow opposing perturbations to be co-represented. Our results suggest different bimanual movement contexts engage at least partially separate representations of dynamics and kinematics in the motor system.
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Nawasreh, Zakariya, David Logerstedt, Adam Marmon, and Lynn Snyder-Mackler. "Clinical and Biomechanical Efficacies of Mechanical Perturbation Training After Anterior Cruciate Ligament Rupture." Journal of Sport Rehabilitation 28, no. 8 (November 1, 2019): 877–86. http://dx.doi.org/10.1123/jsr.2017-0363.
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Context:Manual perturbation training improves knee functional performance and mitigates abnormal gait in patients with anterior cruciate ligament (ACL) rupture. However, manual perturbation training is time- and labor-intensive for therapists.Objective:To investigate whether perturbation training administered using a mechanical device can provide effects similar to manual training on clinical measures and knee biomechanics after ACL rupture.Design:Prospective cohort (therapeutic) study. A 2 × 2 analysis of variance was used for statistical analysis.Setting:A clinical and biomechanical laboratory.Patients:Eighteen level I/II patients with acute ACL ruptures participated in this preliminary study.Intervention:Nine patients received mechanical perturbation training on an automated mechanical device (mechanical group), and 9 patients received manual perturbation training (manual group).Outcome Measures:Patients completed performance-based testing (quadriceps strength and single-legged hop tests), patient-reported questionnaires (Knee Outcome Survey-Activities of Daily Living Scale, Global Rating Score, and International Knee Documentation Committee 2000), and 3-dimensional gait analysis before (pretesting) and after (posttesting) training.Results:There was no significant group-by-time interaction found for all measures (P ≥ .18). Main effects of time were found for International Knee Documentation Committee 2000 (pretesting: 69.10 [10.95], posttesting: 75.14 [7.19]), knee excursion during weight-acceptance (pretesting: 16.01° [3.99°]; posttesting: 17.28° [3.99°]) and midstance (pretesting: 14.78° [4.13°]; posttesting: 16.92° [4.53°]) and external knee-flexion moment (pretesting: 0.43 [0.11] N m/kg/m; posttesting: 0.48 [0.11] N m/kg/m) (P ≤ .04). After accounting for pretesting groups’ differences, the mechanical group scored significantly higher on triple hops (mechanical: 96.73% [6.65%]; manual: 84.97% [6.83%]) and 6-m timed hops (mechanical: 102.07% [9.50%]; manual: 91.21 [9.42%]) (P ≤ .047) compared with manual group.Conclusion:The clinical significance of this study is the mechanical perturbation training produced effects similar to manual training, with both training methods were equally effective at improving patients’ perception of knee function and increasing knee excursion and external flexion moment during walking after acute ACL rupture. Mechanical perturbation training is a potential treatment to improve patients’ functional and biomechanical outcomes after ACL rupture.
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Lurie, Jon D., Alexandra B. Zagaria, Lisa Ellis, Dawna Pidgeon, Kathleen M. Gill-Body, Christina Burke, Kurt Armbrust, Sharil Cass, Kevin F. Spratt, and Christine M. McDonough. "Surface Perturbation Training to Prevent Falls in Older Adults: A Highly Pragmatic, Randomized Controlled Trial." Physical Therapy 100, no. 7 (January 30, 2020): 1153–62. http://dx.doi.org/10.1093/ptj/pzaa023.
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Abstract Background Falls are the leading cause of injuries among older adults, and trips and slips are major contributors to falls. Objective The authors sought to compare the effectiveness of adding a component of surface perturbation training to usual gait/balance training for reducing falls and fall-related injury in high-risk older adults referred to physical therapy. Design This was a multi-center, pragmatic, randomized, comparative effectiveness trial. Setting Treatment took place within 8 outpatient physical therapy clinics. Patients This study included 506 patients 65+ years of age at high fall risk referred for gait/balance training. Intervention This trial evaluated surface perturbation treadmill training integrated into usual multimodal exercise-based balance training at the therapist’s discretion versus usual multimodal exercise-based balance training alone. Measurements Falls and injurious falls were assessed with a prospective daily fall diary, which was reviewed via telephone interview every 3 months for 1 year. A total of 211/253 (83%) patients randomized to perturbation training and 210/253 (83%) randomized to usual treatment provided data at 3-month follow-up. At 3 months, the perturbation training group had a significantly reduced chance of fall-related injury (5.7% versus 13.3%; relative risk 0.43) but no significant reduction in the risk of any fall (28% versus 37%, relative risk 0.78) compared with usual treatment. Time to first injurious fall showed reduced hazard in the first 3 months but no significant reduction when viewed over the entire first year. Limitations The limitations of this trial included lack of blinding and variable application of interventions across patients based on pragmatic study design. Conclusion The addition of some surface perturbation training to usual physical therapy significantly reduced injurious falls up to 3 months posttreatment. Further study is warranted to determine the optimal frequency, dose, progression, and duration of surface perturbation aimed at training postural responses for this population.
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Nguyen, Katrina P., Weiwei Zhou, Erin McKenna, Katrina Colucci-Chang, Laurence C. Jayet Bray, Eghbal A. Hosseini, Laith Alhussein, Meena Rezazad, and Wilsaan M. Joiner. "The 24-h savings of adaptation to novel movement dynamics initially reflects the recall of previous performance." Journal of Neurophysiology 122, no. 3 (September 1, 2019): 933–46. http://dx.doi.org/10.1152/jn.00569.2018.
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Humans rapidly adapt reaching movements in response to perturbations (e.g., manipulations of movement dynamics or visual feedback). Following a break, when reexposed to the same perturbation, subjects demonstrate savings, a faster learning rate compared with the time course of initial training. Although this has been well studied, there are open questions on the extent early savings reflects the rapid recall of previous performance. To address this question, we examined how the properties of initial training (duration and final adaptive state) influence initial single-trial adaptation to force-field perturbations when training sessions were separated by 24 h. There were two main groups that were distinct based on the presence or absence of a washout period at the end of day 1 (with washout vs. without washout). We also varied the training duration on day 1 (15, 30, 90, or 160 training trials), resulting in 8 subgroups of subjects. We show that single-trial adaptation on day 2 scaled with training duration, even for similar asymptotic levels of learning on day 1 of training. Interestingly, the temporal force profile following the first perturbation on day 2 matched that at the end of day 1 for the longest training duration group that did not complete the washout. This correspondence persisted but was significantly lower for shorter training durations and the washout subject groups. Collectively, the results suggest that the adaptation observed very early in reexposure results from the rapid recall of the previously learned motor recalibration but is highly dependent on the initial training duration and final adaptive state. NEW & NOTEWORTHY The extent initial readaptation reflects the recall of previous motor performance is largely unknown. We examined early single-trial force-field adaptation on the second day of training and distinguished initial retention from recall. We found that the single-trial adaptation following the 24-h break matched that at the end of the first day, but this recall was modified by the training duration and final level of learning on the first day of training.
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Handelzalts, Shirley, Michal Kenner-Furman, Ganit Gray, Nachum Soroker, Guy Shani, and Itshak Melzer. "Effects of Perturbation-Based Balance Training in Subacute Persons With Stroke: A Randomized Controlled Trial." Neurorehabilitation and Neural Repair 33, no. 3 (February 15, 2019): 213–24. http://dx.doi.org/10.1177/1545968319829453.
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Background: Reactive balance responses are critical for fall prevention. Perturbation-based balance training (PBBT) has shown a positive effect in reducing the risk of falls among older adults and persons with Parkinson’s disease. Objective: To explore the effect of a short-term PBBT on reactive balance responses, performance-based measures of balance and gait and balance confidence. Methods: Thirty-four moderate-high functioning, subacute persons with stroke (PwS) (lower extremity Fugl-Meyer score 29.2 ± 4.3; Berg Balance Scale [BBS] score 43.8 ± 9.5, 42.0 ± 18.7 days after stroke onset) hospitalized in a rehabilitation setting were randomly allocated to PBBT (n = 18) and weight shifting and gait training (WS>) (n = 16). Both groups received 12 training sessions, 30 minutes each, for a period of 2.5 weeks. PBBT included unexpected balance perturbations during standing and treadmill walking, WS> included weight shifting in standing and treadmill walking without perturbations. The main outcome measures, that is, multiple step-threshold and fall-threshold were examined at baseline, immediately postintervention, and about 5 weeks postintervention. The secondary outcome measures, that is, BBS, 6-minute walk test (6MWT), 10-meter walk test (10MWT), and Activity-specific Balance Confidence (ABC) scale were examined at baseline and immediately postintervention. Results: Compared with the WS> group, immediately postintervention participants in the PBBT group showed higher multiple-step thresholds in response to forward and backward surface translations (effect size [ES] = 1.07 and ES = 1.10, respectively) and moderate ES in the ABC scale (ES = 0.74). No significant differences were found in fall-threshold, BBS, 6MWT, and 10MWT between the groups. Conclusions: Inclusion of perturbation training during rehabilitation of PwS improved reactive balance and balance confidence.
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Nawasreh, Zakariya, Mathew Failla, Adam Marmon, David Logerstedt, and Lynn Snyder-Mackler. "Comparing the effects of mechanical perturbation training with a compliant surface and manual perturbation training on joints kinematics after ACL-rupture." Gait & Posture 64 (July 2018): 43–49. http://dx.doi.org/10.1016/j.gaitpost.2018.05.027.
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Chmielewski, Terese L., Wendy J. Hurd, Katherine S. Rudolph, Michael J. Axe, and Lynn Snyder-Mackler. "Perturbation Training Improves Knee Kinematics and Reduces Muscle Co-contraction After Complete Unilateral Anterior Cruciate Ligament Rupture." Physical Therapy 85, no. 8 (August 1, 2005): 740–49. http://dx.doi.org/10.1093/ptj/85.8.740.
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Abstract Background and Purpose. Dynamic knee stabilization strategies of people who successfully compensate for the absence of an anterior cruciate ligament (ACL) (“copers”) are different from those of people who do not compensate well for the injury (“noncopers”). Early after injury, certain patients (“potential copers”) can increase the likelihood of successfully compensating for the injury by participating in 10 sessions of perturbation training. The purpose of this study was to determine how perturbation training alters muscle co-contraction and knee kinematics in potential copers. Subjects. Seventeen individuals with acute, unilateral ACL rupture who were categorized as potential copers and 17 subjects without injuries who were matched by age, sex, and activity level were recruited for this study. Methods. Motion analysis and electromyographic data were collected as subjects walked across a stationary or moving platform (horizontal translation) before and after perturbation training. Results. Before training, potential copers had higher co-contraction indexes and lower peak knee flexion angles than subjects without injuries. After training, potential copers' movement patterns more closely resembled those of subjects without injuries (ie, they showed reduced co-contraction indexes and increased peak knee flexion angles during stance). Discussion and Conclusion. Perturbation training reduced quadriceps femoris-hamstring muscle and quadriceps femoris-gastrocnemius muscle co-contractions and normalized knee kinematics in individuals with ACL rupture who were classified as potential copers. Findings from this study provide evidence for a mechanism by which perturbation training acts as an effective intervention for promoting coordinated muscle activity in a select population of people with ACL rupture.
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Thangavel, P., and T. Kathirvalavakumar. "Training feedforward networks using simultaneous perturbation with dynamic tunneling." Neurocomputing 48, no. 1-4 (October 2002): 691–704. http://dx.doi.org/10.1016/s0925-2312(01)00639-7.
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Wang, Chunhua, Lin Xiong, Jingru Sun, and Wei Yao. "Memristor-based neural networks with weight simultaneous perturbation training." Nonlinear Dynamics 95, no. 4 (December 18, 2018): 2893–906. http://dx.doi.org/10.1007/s11071-018-4730-z.
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de Sousa, Patricia Nascimento, Marina Brito Silva, Andrea Cristina de Lima-Pardini, and Luis Augusto Teixeira. "Resistance Strength Training’s Effects on Late Components of Postural Responses in the Elderly." Journal of Aging and Physical Activity 21, no. 2 (April 2013): 208–21. http://dx.doi.org/10.1123/japa.21.2.208.
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The effect of resistance strength training on different phases of reactive postural responses to upright-stance perturbation was assessed in elderly women. Perturbation to body balance was produced by fast arm movements aiming at lifting different loads in either certain or uncertain contexts. Results from center-of-pressure analysis showed that lifting a light load under uncertainty led to more body sway than under certainty. Resistance strength training led to short periods of body sway in the compensation phase and to decreased variability in the stabilization phase of postural responses. These results suggest that neuromuscular adaptation from resistance strength training benefits late phases of postural responses to perturbation of body balance in the elderly.
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Zhu, Lingchen, Entao Liu, and James H. McClellan. "Sparse-promoting full-waveform inversion based on online orthonormal dictionary learning." GEOPHYSICS 82, no. 2 (March 1, 2017): R87—R107. http://dx.doi.org/10.1190/geo2015-0632.1.
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Full-waveform inversion (FWI) delivers high-resolution images of the subsurface by minimizing iteratively the misfit between recorded and calculated seismic data. We have attacked this misfit successfully with the Gauss-Newton method and sparsity-promoting regularization based on fixed multiscale transforms that permit significant subsampling of the seismic data when the model perturbation at each FWI data-fitting iteration can be represented with sparse coefficients. Rather than using analytical transforms with predefined dictionaries to achieve sparse representation, we developed an adaptive transform called the sparse orthonormal transform (SOT), whose dictionary is learned from many small training patches taken from the model perturbations in previous iterations. The patch-based dictionary is constrained to be orthonormal and trained with an online approach to provide the best sparse representation of the complex features and variations in the entire model perturbation. The complexity of the training method is proportional to the cube of the number of samples in one small patch. By incorporating compressive subsampling and the adaptive SOT-based representation into the Gauss-Newton least-squares problem for each FWI iteration, the model perturbation can be recovered after an [Formula: see text]-norm sparsity constraint is applied on the SOT coefficients. Numerical experiments on synthetic models determined that the SOT-based sparsity-promoting regularization can provide robust FWI results with reduced computation.
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Aprigliano, Federica, Dario Martelli, Peppino Tropea, Guido Pasquini, Silvestro Micera, and Vito Monaco. "Aging does not affect the intralimb coordination elicited by slip-like perturbation of different intensities." Journal of Neurophysiology 118, no. 3 (September 1, 2017): 1739–48. http://dx.doi.org/10.1152/jn.00844.2016.
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This study was aimed at verifying whether aging modifies intralimb coordination strategy during corrective responses elicited by unexpected slip-like perturbations delivered during steady walking on a treadmill. To this end, 10 young and 10 elderly subjects were asked to manage unexpected slippages of different intensities. We analyzed the planar covariation law of the lower limb segments, using the principal component analysis, to verify whether elevation angles of older subjects covaried along a plan before and after the perturbation. Results showed that segments related to the perturbed limbs of both younger and older people do not covary after all perturbations. Conversely, the planar covariation law of the unperturbed limb was systematically held for younger and older subjects. These results occurred despite differences in spatio-temporal and kinematic parameters being observed among groups and perturbation intensities. Overall, our analysis revealed that aging does not affect intralimb coordination during corrective responses induced by slip-like perturbation, suggesting that both younger and older subjects adopt this control strategy while managing sudden and unexpected postural transitions of increasing intensities. Accordingly, results corroborate the hypothesis that balance control emerges from a governing set of biomechanical invariants, that is, suitable control schemes (e.g., planar covariation law) shared across voluntary and corrective motor behaviors, and across different sensory contexts due to different perturbation intensities, in both younger and older subjects. In this respect, our findings provide further support to investigate the effects of specific task training programs to counteract the risk of fall. NEW & NOTEWORTHY This study was aimed at investigating how aging affects the intralimb coordination of lower limb segments, described by the planar covariation law, during unexpected slip-like perturbations of increasing intensity. Results revealed that neither the aging nor the perturbation intensity affects this coordination strategy. Accordingly, we proposed that the balance control emerges from an invariant set of control schemes shared across different sensory motor contexts and despite age-related neuromuscular adaptations.
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Cereceres, Patrick A., Christina Carrera, Fabricio Saucedo, and Feng Yang. "Treadmill-based Perturbation Training For Preventing Falls Among Young Adults." Medicine & Science in Sports & Exercise 49, no. 5S (May 2017): 685. http://dx.doi.org/10.1249/01.mss.0000518811.11732.fb.
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Liu, Jian. "Aging effect on risk of slipping after walkway perturbation training." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 57, no. 1 (September 2013): 101–3. http://dx.doi.org/10.1177/1541931213571024.
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Logerstedt, David, Lynn Snyder-Mackler, and Michael J. Axe. "Knee Function Following Perturbation Training In Potential Copers And Noncopers." Medicine & Science in Sports & Exercise 41 (May 2009): 353. http://dx.doi.org/10.1249/01.mss.0000355624.10578.74.
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Konin, Jeff G., and Marc R. Bernier. "Perturbation and Agility Training in the Rehabilitation of Soccer Athletes." Athletic Therapy Today 8, no. 3 (May 2003): 20–22. http://dx.doi.org/10.1123/att.8.3.20.
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Hurd, Wendy J., Terese L. Chmielewski, and Lynn Snyder-Mackler. "Perturbation-enhanced neuromuscular training alters muscle activity in female athletes." Knee Surgery, Sports Traumatology, Arthroscopy 14, no. 1 (June 4, 2005): 60–69. http://dx.doi.org/10.1007/s00167-005-0624-y.
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Teixeira, Luis A., Renato Moraes, Jacques Duysens, Michael L. Madigan, and Tibor Hortobágyi. "Which mechanisms underlie sensorimotor adaptations to perturbation-based balance training?" Brazilian Journal of Motor Behavior 14, no. 3 (September 1, 2020): 94–96. http://dx.doi.org/10.20338/bjmb.v14i3.195.
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Ofori, Ernest Kwesi, Shuaijie Wang, and Tanvi Bhatt. "Validity of Inertial Sensors for Assessing Balance Kinematics and Mobility during Treadmill-Based Perturbation and Dance Training." Sensors 21, no. 9 (April 28, 2021): 3065. http://dx.doi.org/10.3390/s21093065.
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Inertial sensors (IS) enable the kinematic analysis of human motion with fewer logistical limitations than the silver standard optoelectronic motion capture (MOCAP) system. However, there are no data on the validity of IS for perturbation training and during the performance of dance. The aim of this present study was to determine the concurrent validity of IS in the analysis of kinematic data during slip and trip-like perturbations and during the performance of dance. Seven IS and the MOCAP system were simultaneously used to capture the reactive response and dance movements of fifteen healthy young participants (Age: 18–35 years). Bland Altman (BA) plots, root mean square errors (RMSE), Pearson’s correlation coefficients (R), and intraclass correlation coefficients (ICC) were used to compare kinematic variables of interest between the two systems for absolute equivalency and accuracy. Limits of agreements (LOA) of the BA plots ranged from −0.23 to 0.56 and −0.21 to 0.43 for slip and trip stability variables, respectively. The RMSE for slip and trip stabilities were from 0.11 to 0.20 and 0.11 to 0.16, respectively. For the joint mobility in dance, LOA varied from −6.98–18.54, while RMSE ranged from 1.90 to 13.06. Comparison of IS and optoelectronic MOCAP system for reactive balance and body segmental kinematics revealed that R varied from 0.59 to 0.81 and from 0.47 to 0.85 while ICC was from 0.50 to 0.72 and 0.45 to 0.84 respectively for slip–trip perturbations and dance. Results of moderate to high concurrent validity of IS and MOCAP systems. These results were consistent with results from similar studies. This suggests that IS are valid tools to quantitatively analyze reactive balance and mobility kinematics during slip–trip perturbation and the performance of dance at any location outside, including the laboratory, clinical and home settings.
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Mohamed Suhaimy, Mohamed Suhair Bin, Yoshiro Okubo, Phu D. Hoang, and Stephen R. Lord. "Reactive Balance Adaptability and Retention in People With Multiple Sclerosis: A Systematic Review and Meta-Analysis." Neurorehabilitation and Neural Repair 34, no. 8 (June 6, 2020): 675–85. http://dx.doi.org/10.1177/1545968320929681.
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Aim. To compare reactive balance in people with multiple sclerosis (MS) with healthy controls and to examine the ability of people with MS to adapt their reactive balance and retain training effects. Data Sources. Electronic databases (PubMed, EMBASE, PsychINFO) and reference lists of included articles from inception to February 25, 2019. Study Selection. Case-control and intervention studies that assessed reactive balance using mechanical perturbations in people with a confirmed diagnosis of MS. Results. Meta-analyses of 9 studies (n = 342) showed that people with MS have significantly worse reactive balance than healthy controls (standardized mean difference [SMD] 0.78, 95% CI 0.44-1.11, P < .0001, I2 = 47%). Specifically, people with MS have greater center of mass displacements (SMD 0.41, 95% CI 0.05-0.77, P = .02, I2 = 9%) and longer response times (MD (ms) 31.45, 95% CI 19.91-42.98, P < .0001, I2 = 75%) in response to standing perturbations than healthy controls. Subsequent meta-analyses revealed training comprising repeated exposure to perturbations improved response times ( P < .001) and training effects on response times could be retained for 24 hours ( P < .001) in people with MS. Conclusions. Reactive balance assessments can highlight functional impairments related to falls in people with MS, and perturbation training can acutely improve reactive balance control and such improvements can be retained for 24 hours in this population. Systematic review registration number: CRD42019126130.
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Tajali, Shirin, Mina Rouhani, Mohammad Mehravar, Hossein Negahban, Elham Sadati, and Ali E. Oskouei. "Effects of External Perturbations on Anticipatory and Compensatory Postural Adjustments in Patients with Multiple Sclerosis and a Fall History." International Journal of MS Care 20, no. 4 (July 1, 2018): 164–72. http://dx.doi.org/10.7224/1537-2073.2016-098.
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Abstract Background: Although previous studies have investigated postural adjustment mechanisms in patients with multiple sclerosis (MS), it seems that no study has yet investigated the relationship between anticipatory and compensatory postural adjustments (APAs and CPAs, respectively) and falls. Methods: Seventeen MS fallers, 17 MS nonfallers, and 15 controls were exposed to a series of expected and unexpected backward pull perturbations applied at the trunk level. The electrical activity of 12 leg and trunk muscles as well as center of pressure displacement were recorded. Results: The MS fallers had delayed muscle activity onsets compared with MS nonfallers and controls. In addition, a significantly lower level of muscle activity during APAs was detected in MS fallers compared with controls. Moreover, in the unexpected condition of perturbation, significantly smaller CPA was observed in MS fallers compared with controls. Both groups of patients with MS required more time to stabilize their center of pressure after both types of perturbations compared with controls. Conclusions: The inability to produce efficient APAs and CPAs during perturbations may explain the high rates of postural instability and falls in patients with MS. Findings from this study provide a background for the development of perturbation-based training programs aimed at balance improvement and fall prevention by restoring mechanisms underlying balance impairments.
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Shu, Hai, and Hongtu Zhu. "Sensitivity Analysis of Deep Neural Networks." Proceedings of the AAAI Conference on Artificial Intelligence 33 (July 17, 2019): 4943–50. http://dx.doi.org/10.1609/aaai.v33i01.33014943.
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Deep neural networks (DNNs) have achieved superior performance in various prediction tasks, but can be very vulnerable to adversarial examples or perturbations. Therefore, it is crucial to measure the sensitivity of DNNs to various forms of perturbations in real applications. We introduce a novel perturbation manifold and its associated influence measure to quantify the effects of various perturbations on DNN classifiers. Such perturbations include various external and internal perturbations to input samples and network parameters. The proposed measure is motivated by information geometry and provides desirable invariance properties. We demonstrate that our influence measure is useful for four model building tasks: detecting potential ‘outliers’, analyzing the sensitivity of model architectures, comparing network sensitivity between training and test sets, and locating vulnerable areas. Experiments show reasonably good performance of the proposed measure for the popular DNN models ResNet50 and DenseNet121 on CIFAR10 and MNIST datasets.
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Fitzgerald, G. Kelley, John D. Childs, Tara M. Ridge, and James J. Irrgang. "Agility and Perturbation Training for a Physically Active Individual With Knee Osteoarthritis." Physical Therapy 82, no. 4 (April 1, 2002): 372–82. http://dx.doi.org/10.1093/ptj/82.4.372.
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Abstract Background and Purpose. People with knee osteoarthritis (OA) sometimes report episodes of knee instability that limit their activities of daily living. The episodes of instability are similar to those reported by people with knee ligament injuries. The authors believe that modifications of interventions that are used to promote knee stability in individuals with knee ligament injuries can be used to enhance knee stability and function in people with knee OA. The purpose of this case report is to describe the development and implementation of an agility and perturbation training program that was used in conjunction with traditional rehabilitation activities for a patient with knee OA. Case Description. The patient was a 73-year-old woman with a diagnosis of bilateral knee OA. Her chief complaints were knee pain and episodes of partial“giving way” at the knee during walking, stair climbing, and participation in tennis and golf. The patient participated in 12 treatment sessions at a frequency of 2 visits per week. The rehabilitation program consisted of lower-extremity stretching, strengthening and endurance exercises that were supplemented with a variety of walking-based agility training techniques, and perturbation training techniques. Outcome. At the completion of rehabilitation, the patient was able to walk on level surfaces and stairs and return to playing golf and tennis without episodes of instability and with reduced pain. Discussion. Supplementing rehabilitation programs for people with knee OA with a modified agility and perturbation training program may assist them in returning to higher levels of physical activity with less pain and instability following rehabilitation. Further research is needed to determine the role of agility and perturbation training in people with knee OA.
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Feng, Huijie, Chunpeng Wu, Guoyang Chen, Weifeng Zhang, and Yang Ning. "Regularized Training and Tight Certification for Randomized Smoothed Classifier with Provable Robustness." Proceedings of the AAAI Conference on Artificial Intelligence 34, no. 04 (April 3, 2020): 3858–65. http://dx.doi.org/10.1609/aaai.v34i04.5798.
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Recently smoothing deep neural network based classifiers via isotropic Gaussian perturbation is shown to be an effective and scalable way to provide state-of-the-art probabilistic robustness guarantee against ℓ2 norm bounded adversarial perturbations. However, how to train a good base classifier that is accurate and robust when smoothed has not been fully investigated. In this work, we derive a new regularized risk, in which the regularizer can adaptively encourage the accuracy and robustness of the smoothed counterpart when training the base classifier. It is computationally efficient and can be implemented in parallel with other empirical defense methods. We discuss how to implement it under both standard (non-adversarial) and adversarial training scheme. At the same time, we also design a new certification algorithm, which can leverage the regularization effect to provide tighter robustness lower bound that holds with high probability. Our extensive experimentation demonstrates the effectiveness of the proposed training and certification approaches on CIFAR-10 and ImageNet datasets.
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VARGA, T., and H. BUNKE. "OFFLINE HANDWRITING RECOGNITION USING SYNTHETIC TRAINING DATA PRODUCED BY MEANS OF A GEOMETRICAL DISTORTION MODEL." International Journal of Pattern Recognition and Artificial Intelligence 18, no. 07 (November 2004): 1285–302. http://dx.doi.org/10.1142/s0218001404003666.
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A perturbation model for the generation of synthetic textlines from existing cursively handwritten lines of text produced by human writers is presented. The goal of synthetic textline generation is to improve the performance of an offline cursive handwriting recognition system by providing it with additional training data. It can be expected that by adding synthetic training data the variability of the training set improves, which leads to a higher recognition rate. On the other hand, synthetic training data may bias a recognizer towards unnatural handwriting styles, which could lead to a deterioration of the recognition rate. In this paper the proposed perturbation model is evaluated under several experimental conditions, and it is shown that significant improvement of the recognition performance is possible even when the original training set is large and the textlines are provided by a large number of different writers.
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Gray, Vicki L., Masahiro Fujimoto, and Mark W. Rogers. "Lateral Perturbation-Induced and Voluntary Stepping in Fallers and Nonfallers After Stroke." Physical Therapy 100, no. 9 (June 12, 2020): 1557–67. http://dx.doi.org/10.1093/ptj/pzaa109.
Full textAbstract:
Abstract Objective A loss of balance poststroke from externally induced perturbations or during voluntary movements is often recovered by stepping. The purpose of this study was to characterize stepping behavior during lateral induced waist-pull perturbations and voluntary steps in community-dwelling fallers and nonfallers with chronic stroke. Methods This study used a cohort design. Thirty participants >6 months poststroke were exposed to 24 externally triggered lateral waist-pull perturbations and 20 voluntary steps. Balance tolerance limit (BTL) (transition from single to multiple steps) and first step type were determined for the waist-pull perturbations. Step parameters of initiation time, velocity, first step length, and clearance were calculated at and above BTL and for the voluntary steps. Hip abductor/adductor torque, foot cutaneous sensation, and self-reported falls that occurred 6 months prior were evaluated. Results Twelve participants were classified retrospectively as fallers and 18 as nonfallers. Fallers had a reduced BTL and took more medial first steps than nonfallers. Above BTL, no between-group differences were found in medial steps. At BTL, the nonparetic step clearance was reduced in fallers. Above BTL, fallers took longer to initiate a paretic and nonparetic step and had a reduced nonparetic step length and clearance compared with nonfallers. There was a between-group difference in step initiation time for voluntary stepping with the paretic leg (P < .05). Fallers had a reduced paretic abductor torque and impaired paretic foot cutaneous sensation. Conclusion A high fall rate poststroke necessitates effective fall prevention strategies. Given that more differences were found during perturbation-induced stepping between fallers and nonfallers, further research assessing perturbation-induced training on reducing falls is needed. Impact Falls assessments should include both externally induced perturbations along with voluntary movements in determining the fall risk.