Learning complex upper-limb movements through practicing movement elements.

Upper-limb complex movements constitute a major part of our daily activities. Research shows complex movements are generated by sequences of movement elements represented by a unimodal bell-shaped velocity curve. We utilized this understanding in the field of motor skill acquisition and hypothesized that practicing a movement element of a complex movement trajectory will facilitate the performance on the respective complex movement trajectory. To test this, we designed an experiment where the control group learned a full complex trajectory, whereas the two elemental groups learned two different movement elements of the complex trajectory. The two main outcome measures explaining the performance were accuracy and speed. The elemental groups, after training on movement elements, significantly improved their speed and accuracy when tested on the full complex trajectory. The result illustrated that training on a movement element of a complex trajectory benefited the performance of the full complex trajectory. The two elemental groups showed similar improvements in the performance of the complex motor skill, despite obtaining training on different movement elements of the same complex movement. The findings show that complex movements can be learned by practicing their movement elements.

Manipulating device-to-body forces in passive exosuit: An experimental investigation on the effect of moment arm orientation using passive back-assist exosuit emulator.

Passive exosuits have been vastly researched in the past decade for lifting tasks to alleviate the mechanical loading on the spine and reduce the lower back muscle activities in lifting tasks. Despite promising advantages of exosuits, factors such as comfort directly influence the user's acceptability of such body-worn devices. Exosuits' routing/anchoring points, which transmit device-to-body forces, remain the leading cause of discomfort among users. In the present study, we sought to investigate the effect of the routing element, that is, the "moment arm," in altering the device-to-body forces and perceived discomfort. We first presented a simplified human-exosuit model to establish insight into the effect of the moment arm on the device-to-body forces acting at the shoulder (FS) and waist (FW). Further, an experimental investigation was conducted on 10 participants with six different exosuit moment arm configurations (C1, C2, C3, C4, C5, and C6) to investigate their effect on the device-to-body forces, perceived discomfort, and muscle activity using a passive back-assist exosuit emulator in a lifting/lowering task. Configuration C4 was found to be most beneficial in reducing device-to-body forces at the shoulder and waist by up to 44.6 and 22.2%, respectively, during lifting. Subjective scores also comprehended with the device-to-body forces, indicating that C4 produces significantly less discomfort for participants. The outcome of the study illustrates the importance of selecting an appropriate moment arm configuration for passive back support exosuits in alleviating the device-to-body forces and perceived discomfort.

Vibratory cue training elicits anticipatory postural responses to an external perturbation.

Anticipatory postural adjustments (APAs) represent the feedforward mechanism of neuromuscular control essential for maintaining balance under predictable perturbations. The importance of vision as a distal sensory modality in the generation of APAs is well established. However, the capabilities of external cues in generating APAs are less explored. In the present study, vibratory cue was investigated for its reliability among healthy individuals in generating anticipatory response under external perturbation in the absence of vision. Ten participants, in quiet stance, were provided with external perturbation in the form of pendulum impact in anterior-posterior (AP) direction under conditions of: both vision and vibratory cue absent; vision present but vibratory cue was absent; vision and vibratory cue both were present; only vibratory cue is present with vision being absent. EMG activities of the leg muscles and displacement of center of pressure (COP) in AP direction were recorded. The data were later analyzed and quantified in the time frame of anticipatory and compensatory phases. The results showed that with training, participants were able to generate significant APAs relying on the vibratory cue alone. Improvement in APAs was accompanied by minimizing the need for larger CPA and improved stability (COP displacement) under perturbation. The study outcome indicates the possibility of using vibratory cues for APA-based interventions.

Lower limb rehabilitation robotics: The current understanding and technology.

BACKGROUND: With the increasing rate of ambulatory disabilities and rise in the elderly population, advance methods to deliver the rehabilitation and assistive services to patients have become important. Lower limb robotic therapeutic and assistive aids have been found to improve the rehabilitation outcome. OBJECTIVE: The article aims to present the updated understanding in the field of lower limb rehabilitation robotics and identify future research avenues. METHODS: Groups of keywords relating to assistive technology, rehabilitation robotics, and lower limb were combined and searched in EMBASE, IEEE Xplore Digital Library, Scopus, Web of Science and Google Scholar database. RESULTS: Based on the literature collected from the databases we provide an overview of the understanding of robotics in rehabilitation and state of the art devices for lower limb rehabilitation. Technological advancements in rehabilitation robotic architecture (sensing, actuation and control) and biomechanical considerations in design have been discussed. Finally, a discussion on the major advances, research directions, and challenges is presented. CONCLUSIONS: Although the use of robotics has shown a promising approach to rehabilitation and reducing the burden on caregivers, extensive and innovative research is still required in both cognitive and physical human-robot interaction to achieve treatment efficacy and efficiency.

Lower limb rehabilitation using multimodal measurement of sit-to-stand and stand-to-sit task.

PURPOSE: Assistive and rehabilitation devices are dependent upon detecting the user intent through physiological and kinematics changes. Rising from a chair and vice-versa have been less investigated for the purpose of rehabilitation-aids. This study investigates the muscle activation along with trunk and knee biomechanics in sagittal plane during sit-to-stand and stand-to-sit transfer. METHOD: Nine healthy participants (age 25.67 ± 3.27 years) were measured for flexion/extension of knee and trunk, and for surface electromyography (EMG) of vastus lateralis (VL) and biceps femoris (BF) of both the legs at a speed of 100 beats per minute while performing sit-to-stand and stand-to-sit task. RESULTS: The knee flexion angles at peak EMG-RMS (root mean square envelope of EMG) were significantly different for the two tasks (p = 0.002). Also, for each muscle, EMG-RMS peak was obtained at significantly different knee angle within the same task (p = 0.046). EMG work done (WD) was also found to be significantly different for the intervened muscles (p = 0.002). CONCLUSIONS: Trunk flexion together with VL showed an earlier onset in sit-to-stand task, which might form an important modality for detecting human intention to perform the activity. However, for stand-to-sit task, some other muscle group in conjunction to BF may be useful for detecting the human intention. The understanding from the study could be used as a first step in devising multimodal control for assistive devices aiding sit-to-stand and stand-to-sit transfers. That would be a novel approach to fuse the data of postural deviation into the EMG signal to achieve lower limb rehabilitation or in prosthetic control.Implications for rehabilitationMulti-modal sensor fusion can be used for realtime monitoring of patient biomechanics.Development of control algorithms for assistive devices aiding sit-stand transfers.Sensor fusion will help in achieving greater robotic compliance rehabilitation.

Finite Element Analysis (FEA) of Perpendicular Plating Versus Conventional Plating in Mandibular Symphysis Fracture.

AIM AND OBJECTIVE: To perform the comparative finite element analysis of conventional and perpendicular plating in mandibular symphyseal fracture. MATERIAL AND METHOD: Two FE model of mandible were developed and symphyseal fracture was created in both of them. Each fractured model was fixed by conventional method 2.0 mm system and perpendicular method 2.00 mm system. Stresses which developed in plates and mandible after application of load were observed in the model. RESULTS: Results of the study indicated that perpendicular method was more resistant to displacing forces and rest of the parameters was within the permitted limits. CONCLUSION: Perpendicular method was reasonably effective as conventional method of fixation for mandibular symphyseal fracture.

Ergonomics investigation for orientation of the handles of wood routers.

OBJECTIVES: Improperly designed hand tools not only expose workers to potential health risks but also hamper their productivity. This study tries to improve the ergonomics of wood routing tasks, suggesting better handle orientations for hand-held wood routers. METHODS: Seven different handle combinations were tested over two routing tasks (beading and dado) with regard to perceived discomfort, electromyography (EMG) of biceps brachii and extensor carpi radialis brevis and hand-arm vibrations (HAV). RESULTS: Handles with 30° and 60° inclinations were found more comfortable than previous 90° handle inclinations for routing tasks. Perceived discomfort in the dado task was found to be significantly higher than in the beading task (p < 0.001); EMG activity also supported this observation. However, EMG data showed no significant difference for the different handles used in the study. No worthwhile reduction was obtained in HAV levels for the modified wooden handles compared to initial plastic handles. Relevance to industry. The ergonomic intervention in wood routers described in this article will contribute to the existing knowledge of ergonomics of handle design and will aid the designers/engineers to design such tool handles that may reduce the risk of work-related musculoskeletal disorders/hand-arm vibration syndrome in workers using wood routers.

Role of 1.5 mm microplates in treatment of symphyseal fracture of mandible: A stress analysis based comparative study.

AIMS AND OBJECTIVES: To perform comparative finite element analysis (FEA)for 2.0 mm standard miniplate and 1.5 mm microplate in isolated symphyseal mandibular fractures. MATERIAL AND METHOD: Two FE models of mandible were developed and symphyseal fracture was created in both of them. Each fractured model was reduced and fixed using two mini plates and two microplates, respectively according Champ's principle. Stresses thus developed in the plates after application of masticatory load were observed in the models. RESULTS: Results of the study indicated there was no significant difference in the stresses developed in either of the bone plating system. CONCLUSION: 1.5 mm Microplates can be used in place of 2.0 mm miniplates in isolated symphyseal fractures of the mandible.

Evaluation of Wound Morphology of Sclerotomy Sites of Sutureless Vitrectomy Using Spectralis Anterior Segment Optical Coherence Tomography.

PURPOSE: The aim of the study was to evaluate wound morphology in vivo in eyes undergoing sutureless vitrectomy. DESIGN: This was a prospective consecutive case series. METHODS: Twenty eyes undergoing sutureless vitrectomy were evaluated using anterior segment optical coherence tomography on days 1, 15, and 30. Ten eyes each belonged to 23-gauge (group A) and 25-gauge (group B). Scans were taken on the incision sites. Group A cases were further divided into group A1 and A2 on the basis of the surgical time of less than 15 minutes' and more than 15 minutes' duration, respectively. RESULTS: On day 1, the mean outer and inner incision diameters in group A were 236.6 and 146 µm, and those for group B were 118.6 and 90 µm. A significant decrease (P < 0.0001) in both the port sizes was observed in both groups' follow-up. Group B showed significant decrease (P < 0.0001) in the port sizes on l follow-up as compared with group A. Group A1 had smaller incision size as compared with group A2 on the first postoperative day, although not statistically significant(P > 0.05). CONCLUSIONS: In both groups, the sclerotomy incisions showed good healing at 1-month duration. The 25-gauge sclerotomies showed better healing characteristics of wound morphology as compared with the 23-gauge sclerotomies.

Wavelength scaling of high harmonic generation close to the multiphoton ionization regime.

We study the wavelength scaling of high harmonic generation efficiency with visible driver wavelengths in the transition between the tunneling and the multiphoton ionization regimes where the Keldysh parameter is around unity. Our experiment shows a less dramatic wavelength scaling of efficiency than the conventional case for near- and mid-IR driver wavelengths, and it is well explained by a generalized three-step model for increased Keldysh parameters that employs complex ionization times in addition to the nonadiabatic ionization. The complex ionization time is critical to avoid the divergence when replacing the quasistatic ionization model by the more general nonadiabatic ionization model. Together, the two modifications present a consistent description of the influence of the atomic potential on the rescattering process in the intermediate Keldysh regime.