Static and dynamic proprioceptive recognition through vibrotactile stimulation

Proprioception provides information regarding the state of an individual's limb in terms of static position and kinesthesia (dynamic movement). When such feedback is lost or impaired, the performance of dexterous control of our biological limbs or assistive devices tends to deteriorate. In this study, we determined if external vibratory stimulation patterns could allow for the perception of a finger's static position and kinesthesia. Using four tactors and two stimulus levels, eight vibratory settings corresponded to eight discrete finger positions. The transition patterns between these eight settings corresponded to kinesthesia. Three experimental blocks assessed the perception of a finger's static position, speed, and movement (amplitude and direction). Our results demonstrated that both position and kinesthesia could be recognized with over 93% accuracy. The outcomes suggest that vibratory stimulus can inform subjects of static and dynamic aspects of finger proprioception. This sensory stimulation approach can be implemented to improve outcomes in clinical populations with sensory deficits, and to enhance user experience when users interact with assistive devices.

Dance-like actions are complex visual stimuli involving multiple changes in body posture across time and space. Visual perception research has demonstrated a difference between the processing of dynamic body movement and the processing of static body posture. Yet, it is unclear whether this processing dissociation continues during the retention of body movement and body form in visual working memory (VWM). When observing a dance-like action, it is likely that static snapshot images of body posture will be retained alongside dynamic images of the complete motion. Therefore, we hypothesized that, as in perception, posture and movement would differ in VWM. Additionally, if body posture and body movement are separable in VWM, as form- and motion-based items, respectively, then differential interference from intervening form and motion tasks should occur during recognition. In two experiments, we examined these hypotheses. In Experiment 1, the recognition of postures and movements was tested in conditions in which the formats of the study and test stimuli matched (movement-study to movement-test, posture-study to posture-test) or mismatched (movement-study to posture-test, posture-study to movement-test). In Experiment 2, the recognition of postures and movements was compared after intervening form and motion tasks. These results indicated that (1) the recognition of body movement based only on posture is possible, but it is significantly poorer than recognition based on the entire movement stimulus, and (2) form-based interference does not impair memory for movements, although motion-based interference does. We concluded that, whereas static posture information is encoded during the observation of dance-like actions, body movement and body posture differ in VWM.

BackgroundAbnormal dynamic knee moments and variations of static foot posture are risk factors for chronic lower limb injury development. However, relationships between the two have yet to be established in...

Objective: To examine the effect of proprioceptive information during postural control in strabismic children.Methods: Postural stability was recorded with a platform (Techno Concept®) in 12 strabismic children aged from 4.9 to 10 years and data were compared to that of 12 control age-matched children. Two postural positions were performed: Romberg and Tandem. Two postural conditions: without and with foam pad. We analyzed the surface area, the length, the mean speed of the center of pressure (CoP) and the effect of proprioceptive information.Results: Strabismic children are more instable than control age-matched children. The surface, the length and the mean speed of CoP are significantly higher in strabismic children than in control age-matched children. Both groups are more instable in Tandem position than in Romberg position. Finally, strabismic children use more proprioceptive information than control age-matched children.Conclusion: For both Romberg and Tandem position, strabismic children are more instable than control age-matched children. Strabismic children use proprioceptive information more than control age-matched children to control their posture.Significance: Proprioceptive inputs are important for control posture particularly for strabismic population.

The effect of wrist surgery on the kinematic consistency of joint axis reconstruction in a static posture.

Deep vein thrombosis (DVT) can lead to life-threatening disorders; however, it can only be recognized after its symptom appear. This study proposed a novel method that can detect the early stage of DVT using electromyography (EMG) signals with vibration stimuli using the convolutional neural networks (CNN) algorithm. The feasibility of the method was tested with eight legs before and after the surgical induction of DVT at nine-time points. Furthermore, perfusion pressure (PP), intracompartmental pressure (IP), and shear elastic modulus (SEM) of the tibialis anterior were also collected. In the proposed method, principal component analysis (PCA) and CNN were used to analyze the EMG data and classify it before and after the DVT stages. The cross-validation was performed in two strategies. One is for each leg and the other is the leave-one-leg-out (LOLO), test without any predicted information, for considering the practical diagnostic tool. The results showed that PCA-CNN can classify before and after DVT stages with an average accuracy of 100% (each leg) and 68.4±20.5% (LOLO). Moreover, all-time points (before induction of DVT and eight-time points after DVT) were classified with an average accuracy of 72.0±11.9% which is substantially higher accuracy than the chance levels (11% for 9-class classification). Based on the experimental results in the pig model, the proposed CNN-based method can classify the before- and after-DVT stages with high accuracy. The experimental results can provide a basis for further developing an early diagnostic tool for DVT using only EMG signals with vibration stimuli.

Purpose: We planned this study to bring attention to the somatosensory impairments in patients with multiple sclerosis (PwMS) and to investigate relationship of somatosensory impairments with dynamic postural stability and upper extremity motor function.Methods: Seven males and 23 females, 30 patients with mean EDSS 2.9 (SD = 1.4), aged between 18 and 65 years (mean = 41.43 ± 14.90 years) were included in this clinical study. Light touch sensorial assessment was made with Semmes Weinstein monofilament test and proprioception by distal proprioception test. Hand strength was measured by the Jamar dynamometer, fine motor skill was examined with nine-hole peg test, functional reach test in sitting and standing position was applied. Nottingham Extended Activities of Daily Living Scale (NEADLS) was used to measure everyday activities.Results: We found a negative and moderate correlation between FRT in standing and light touch of the middle of the heel (right: –0.515), metatarsal bone (right r: 0.453, left r: –0.426), and medial of the foot (right r: –0.462). There was a negative and moderate correlation between NEADLS and light touch of the metatarsal bone (right r: –0.564, left r: –0.472), medial of the foot (right r: –0.531, left r: –0.479), and lateral of the foot (right r: –0.526). We found a positive and moderate correlation between proprioception of the ankle (right r: 0.421 left r: 0.588) and NEADLS.Conclusions: We found impairment in light touch and proprioception and, associations between sensorial functions and dynamic postural stability in PwMS. Also impaired sensorial functions cause dependent patients in daily living activities. In the assessment of balance and falling risk, independency in daily living activities; foot light touch and proprioception sense should be taken into account, hence it may provide guidance in planning rehabilitation programmes.Abbreviations: MS: multiple sclerosis; PwMS: patients with multiple sclerosis; VAS: visual analogue scale; FRT: functional reach test; 9-HPT: Nine-hole peg test; EDSS: The Expanded Disability Status Scale; NEADLS: Nottingham Extended Activities of Daily Living Scale

Patient compliance is important when assessing movement, particularly in a free-living environment when patients are asked to don their own accelerometers. Reducing the number of accelerometers could increase patient compliance. The aims of this study were (1) to determine and compare the validity of different accelerometer combinations and placements for a previously developed posture and dynamic movement identification algorithm. Custom-built activity monitors, each containing one tri-axial accelerometer, were placed on the ankles, right thigh, and waist of 12 healthy adults. Subjects performed a protocol in the laboratory including static orientations of standing, sitting, and lying down, and dynamic movements of walking, jogging, transitions between postures, and fidgeting to simulate free-living activity. When only one accelerometer was used, the thigh was found to be the optimal placement to identify both movement and static postures, with a misclassification error of 10%, and demonstrated the greatest accuracy for walking/fidgeting and jogging classification with sensitivities and positive predictive value (PPVs) greater than 93%. When two accelerometers were used, the waist-thigh accelerometers identified movement and static postures with greater accuracy than the thigh-ankle accelerometers (with a misclassification error of 11% compared to 17%). However, the thigh-ankle accelerometers demonstrated the greatest accuracy for walking/ fidgeting and jogging classification with sensitivities and PPVs greater than 93%. Movement can be accurately classified in healthy adults using tri-axial accelerometers placed on one or two of the following sites: waist, thigh, or ankle. Posture and transitions require an accelerometer placed on the waist and an accelerometer placed on the thigh.

Influence of a passive trunk exoskeleton on subjective physical strain and perceived discomfort during simulated tasks with static trunk flexion posture and dynamic lifting Objective: The influence of a passive back-supporting exoskeleton on perceived physical strain and discomfort was investigated in two occupational tasks. Methods: Thirty-six men (average age 26 years) performed simulated occupational tasks with and without the Laevo® exoskeleton in a balanced and randomised within-subject design. One of the activities was a dynamic lifting task (2 x 5 lifting processes, 11.6 kg load), which was performed with and without exoskeleton in a stoop (stretched knees) and squat position (flexed knees). The second activity was a 90-second sorting task with a static and 40° flexed upper body posture. Subjective physical strain was recorded by the “physical demand” dimension of the NASA-TLX questionnaire, discomfort by an 11-level numeric rating scale. The localisation of discomfort was also reported. The differences between the conditions with and without exoskeleton were analysed for both tasks and lifting postures (stretched vs. flexed knees). Results: With exoskeleton, there was always a small reduction in perceived physical strain levels (p < 0.05). Discomfort was rare, low and mainly in the lower back. For the sorting task with exoskeleton, the median level of discomfort intensity was one point lower (p < 0.05) than without exoskeleton. The frequency of discomfort was also lower with exoskeleton. There were no differences in the intensity of discomfort during dynamic lifting. When the exoskeleton was applied during lifting with stretched knee joints, the frequency of discomfort was slightly reduced; no differences occurred with flexed knee joints. Conclusion: The main potential of the studied exoskeleton appears to lie in activities with a static bent upper body posture. Longitudinal studies with a randomised controlled design are necessary to evaluate whether the possible potential described here is relevant to the prevention of work-related back complaints. Keywords: workplace design – back pain – assistive device

It is known that the illusory displacement of a vibrated limb can be transferred to a nonvibrated contacted limb. The purpose of this study was to quantify and compare the transferred illusory displacements occurring in the intrapersonal and near-personal space. In two tasks, 8 male and 8 female blindfolded subjects estimated (1) the height of the left elbow and (2) the height of an external object located at the same height as the left elbow, by the proprioception of the right arm which was Subject to illusory displacement. If the internal representation of the left elbow in one's body schema could provide precise information of its static position independently of the proprioception of the right arm, the perceived displacement of the right arm might be smaller when influenced by proprioceptive information from the static left arm, than when in contrast instead with an object which is not a body part. There was no difference in the estimation of illusory displacement between male and female subjects and between right and left arms. No significant difference was observed between transferred displacements of the left elbow and the object. This means that the perception of limb position sensed by the proprioception of another limb can be distorted as easily as the perception of location of an external object. This suggests that the internal representation of static limb position is not enough to provide the correct information of current limb position in the absence of vision.

BackgroundThere are some motion platforms for radiotherapy quality assurance. However, no platform with two drive systems that can move along three axes is available.PurposeThe purpose of this study is to develop a dynamic motion platform with two drive systems capable of three‐axis motion and to evaluate its motion performance.MethodsThe developed moving platform had two drive systems that use the same equipment. Each axis of the platform used can support a maximum load of 10 kg. The motors for moving the platform in each direction are capable of a drive stroke up to 40 mm. The drive speed is 30 mm/s at maximum load fluctuation. To evaluate the static positional accuracy of this system with an arbitrary input movement, the XYZ position of each axis was measured using a coordinate measuring machine operating from 0 to 40 mm at 10 mm intervals. In addition, the accuracy of dynamic motion was verified with Sine waveform inputs of different patterns to the three axes for approximately 60 s, and they were compared with the resulting detected signals by SyncTrax.ResultsThe two drive systems were successfully operated on three axes by using independent control systems. For static position, the accuracies were within 0.2 mm, 0.05 mm, and 0.14 mm for lateral, longitudinal, and vertical directions, respectively. For dynamic motion, the mean absolute errors in the X, Y, and Z axes between the platform inputs and SyncTrax detected signals were 0.14 ± 0.10 mm, 0.16 ± 0.12 mm, and 0.16 ± 0.11 mm, respectively.ConclusionsA new dynamic platform for radiation therapy with two drive systems capable of three‐axis motion was developed, and the positional accuracy of the drive axes was confirmed to be less than 0.2 mm.

Designing Robust and Automated Treatment Plans Utilizing Dynamic Couch Motion With Automated Treatment Planning: Delivering Dose to a New Dimension ― Part B

Dimensional changes of the neuroforamina in subaxial cervical spine during in vivo dynamic flexion-extension

Observational study of static and dynamic foot postures in professional baseball players. Throughout the course of a professional baseball season, running, cutting, and sprinting activities can produce a breakdown in players' foot function, causing overuse injuries. To investigate the relationship between static and dynamic foot postures; to determine the occurrence of abnormal foot postures in professional baseball players and the incidence of overuse injuries in the lower extremity; and to compare the foot postures of pitchers to those of positional players. The foot postures of 74 professional baseball players were evaluated at rest and during gait. Measures of static foot posture were obtained with a goniometer and included the subtalar neutral position, forefoot/rearfoot position, ankle joint dorsiflexion, tibial angle in standing, and calcaneal angle in standing. The FootTrak motion analysis system provided measures of dynamic foot posture (rearfoot supination and pronation) during the stance phase of gait. A questionnaire was completed by players who reported previous lower extremity injuries. The chi-square statistic was used to determine the associations between forefoot position (varus or valgus) and the amount of foot pronation during gait. The forefoot varus and calcaneal valgus in standing was significantly associated with the maximum pronation during the stance phase of gait. Of the 65 players who demonstrated excessive pronation (> 8 degrees), 28 (43%) also reported a previous lower extremity injury. No statistically significant difference occurred, however, between injured and uninjured players with respect to the mean values of static or dynamic foot posture. In addition, foot postures were not associated with a player's position. Selected measures of static rearfoot and forefoot postures may have value in predicting dynamic rearfoot movement during the stance phase of gait. Excessive pronation in the baseball players we studied was not found to be a significant contributing factor in the development of overuse injuries.

100. The Dubousset Functional Test: a baseline analysis of a novel, multidomain assessment of physical function and balance