@article{roy_zheng_kamper_hu_2023, title={Concurrent and Continuous Prediction of Finger Kinetics and Kinematics via Motoneuron Activities}, volume={70}, ISSN={["1558-2531"]}, DOI={10.1109/TBME.2022.3232067}, abstractNote={Objective: Robust neural decoding of intended motor output is crucial to enable intuitive control of assistive devices, such as robotic hands, to perform daily tasks. Few existing neural decoders can predict kinetic and kinematic variables simultaneously. The current study developed a continuous neural decoding approach that can concurrently predict fingertip forces and joint angles of multiple fingers. Methods: We obtained motoneuron firing activities by decomposing high-density electromyogram (HD EMG) signals of the extrinsic finger muscles. The identified motoneurons were first grouped and then refined specific to each finger (index or middle) and task (finger force and dynamic movement) combination. The refined motoneuron groups (separate matrix) were then applied directly to new EMG data in real-time involving both finger force and dynamic movement tasks produced by both fingers. EMG-amplitude-based prediction was also performed as a comparison. Results: We found that the newly developed decoding approach outperformed the EMG-amplitude method for both finger force and joint angle estimations with a lower prediction error (Force: 3.47±0.43 vs 6.64±0.69% MVC, Joint Angle: 5.40±0.50° vs 12.8±0.65°) and a higher correlation (Force: 0.75±0.02 vs 0.66±0.05, Joint Angle: 0.94±0.01 vs 0.5±0.05) between the estimated and recorded motor output. The performance was also consistent for both fingers. Conclusion: The developed neural decoding algorithm allowed us to accurately and concurrently predict finger forces and joint angles of multiple fingers in real-time. Significance: Our approach can enable intuitive interactions with assistive robotic hands, and allow the performance of dexterous hand skills involving both force control tasks and dynamic movement control tasks.}, number={6}, journal={IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING}, author={Roy, Rinku and Zheng, Yang and Kamper, Derek G. G. and Hu, Xiaogang}, year={2023}, month={Jun}, pages={1911–1920} }
 @article{jadelis_ellis_kamper_saul_2023, title={Cosimulation of the index finger extensor apparatus with finite element and musculoskeletal models}, volume={157}, ISSN={["1873-2380"]}, DOI={10.1016/j.jbiomech.2023.111725}, abstractNote={Musculoskeletal modeling has been effective for simulating dexterity and exploring the consequences of disability. While previous approaches have examined motor function using multibody dynamics, existing musculoskeletal models of the hand and fingers have difficulty simulating soft tissue such as the extensor mechanism of the fingers, which remains underexplored. To investigate the extensor mechanism and its impact on finger motor function, we developed a finite element model of the index finger extensor mechanism and a cosimulation method that combines the finite element model with a multibody dynamic model. The finite element model and cosimulation were validated through comparison with experimentally derived tissue strains and fingertip endpoint forces respectively. Tissue strains predicted by the finite element model were consistent with the experimentally observed strains of the 9 postures tested in cadaver specimens. Fingertip endpoint forces predicted using the cosimulation were well aligned in both force (difference within 0.60 N) and direction (difference within 30°with experimental results. Sensitivity of the extensor mechanism to changes in modulus and adhesion configuration were evaluated for ± 50% of experimental moduli, presence of the radial and ulnar adhesions, and joint capsule. Simulated strains and endpoint forces were found to be minimally sensitive to alterations in moduli and adhesions. These results are promising and demonstrate the ability of the cosimulation to predict global behavior of the extensor mechanism, while enabling measurement of stresses and strains within the structure itself. This model could be used in the future to predict the outcomes for different surgical repairs of the extensor mechanism.}, journal={JOURNAL OF BIOMECHANICS}, author={Jadelis, Christopher T. and Ellis, Benjamin J. and Kamper, Derek G. and Saul, Katherine R.}, year={2023}, month={Aug} }
 @article{hinson_berman_filer_kamper_hu_huang_2023, title={Offline Evaluation Matters: Investigation of the Influence of Offline Performance on Real-Time Operation of Electromyography-Based Neural-Machine Interfaces}, volume={31}, ISSN={["1558-0210"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85144812628&partnerID=MN8TOARS}, DOI={10.1109/TNSRE.2022.3226229}, abstractNote={There has been a debate on the most appropriate way to evaluate electromyography (EMG)-based neural-machine interfaces (NMIs). Accordingly, this study examined whether a relationship between offline kinematic predictive accuracy (R2) and user real-time task performance while using the interface could be identified. A virtual posture-matching task was developed to evaluate motion capture-based control and myoelectric control with artificial neural networks (ANNs) trained to low (R2 ≈ 0.4), moderate (R2 ≈ 0.6), and high ( $\text {R}^{\vphantom {\text {D}^{\text {a}}}{2}} \approx 0.8$ ) offline performance levels. Twelve non-disabled subjects trained with each offline performance level decoder before evaluating final real-time posture matching performance. Moderate to strong relationships were detected between offline performance and all real-time task performance metrics: task completion percentage (r = 0.66, p < 0.001), normalized task completion time (r = −0.51, p = 0.001), path efficiency (r = 0.74, p < 0.001), and target overshoots (r = −0.79, p < 0.001). Significant improvements in each real-time task evaluation metric were also observed between the different offline performance levels. Additionally, subjects rated myoelectric controllers with higher offline performance more favorably. The results of this study support the use and validity of offline analyses for optimization of NMIs in myoelectric control research and development.}, journal={IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING}, author={Hinson, Robert M. and Berman, Joseph and Filer, William and Kamper, Derek and Hu, Xiaogang and Huang, He}, year={2023}, pages={680–689} }
 @article{roy_kamper_hu_2023, title={Optimized Model Selection for Concurrent Decoding of Finger Kinetics and Kinematics}, volume={11}, ISSN={["2169-3536"]}, DOI={10.1109/ACCESS.2023.3246950}, abstractNote={Myoelectric-based motor intent detection is typically used to interface with assistive devices. However, the intent detection performance is sensitive to interference of electromyogram (EMG) signals. Recently, EMG signals are decomposed into motor units (MU) firing activities, and neuron binary firing activities can be used to predict motor output in a continuous manner. Different functions that map MU firings to motor output have been implemented, and both composite MU firing frequency and individual MU firing frequency have been used. It is unclear whether one mapping function outperform others. Accordingly, we evaluated three MU-based finger kinetic and kinematic prediction models, by varying the number of MUs and the method of including MU firings into the regression model. We also compared the performance of three EMG amplitude-based models with varying number of channels. We performed MU decomposition in advance for real-time implementations. Our results showed that individual firing frequency of five MUs provided the lowest estimation error (force: 4.66±0.36 %MVC; joint angle: 4.81±0.49°) and highest correlation (force: 0.86±0.01; joint angle: 0.93±0.01) with the measured motor outputs, when compared with mapping method using the populational firing frequency of all MUs or the populational firing frequency of a group of MUs with similar firing activities. The results indicated that firing information at the population level may mask critical information of individual MU firings. These findings allowed us to identify the optimal models for concurrent and continuous finger force and joint angle estimation. A combination of the minimal level of complexity and high accuracy make these models suitable for real-time control of assistive robotic devices.}, journal={IEEE ACCESS}, author={Roy, Rinku and Kamper, Derek G. G. and Hu, Xiaogang}, year={2023}, pages={17348–17358} }
 @article{roy_xu_kamper_hu_2022, title={A generic neural network model to estimate populational neural activity for robust neural decoding}, volume={144}, ISSN={["1879-0534"]}, DOI={10.1016/j.compbiomed.2022.105359}, abstractNote={Robust and continuous neural decoding is crucial for reliable and intuitive neural-machine interactions. This study developed a novel generic neural network model that can continuously predict finger forces based on decoded populational motoneuron firing activities. We implemented convolutional neural networks (CNNs) to learn the mapping from high-density electromyogram (HD-EMG) signals of forearm muscles to populational motoneuron firing frequency. We first extracted the spatiotemporal features of EMG energy and frequency maps to improve learning efficiency, given that EMG signals are intrinsically stochastic. We then established a generic neural network model by training on the populational neuron firing activities of multiple participants. Using a regression model, we continuously predicted individual finger forces in real-time. We compared the force prediction performance with two state-of-the-art approaches: a neuron-decomposition method and a classic EMG-amplitude method. Our results showed that the generic CNN model outperformed the subject-specific neuron-decomposition method and the EMG-amplitude method, as demonstrated by a higher correlation coefficient between the measured and predicted forces, and a lower force prediction error. In addition, the CNN model revealed more stable force prediction performance over time. Overall, our approach provides a generic and efficient continuous neural decoding approach for real-time and robust human-robot interactions.}, journal={COMPUTERS IN BIOLOGY AND MEDICINE}, author={Roy, Rinku and Xu, Feng and Kamper, Derek G. and Hu, Xiaogang}, year={2022}, month={May} }
 @article{phan_nguyen_vermillion_kamper_lee_2022, title={Abnormal proximal-distal interactions in upper-limb of stroke survivors during object manipulation: A pilot study}, volume={16}, ISSN={["1662-5161"]}, DOI={10.3389/fnhum.2022.1022516}, abstractNote={Despite its importance, abnormal interactions between the proximal and distal upper extremity muscles of stroke survivors and their impact on functional task performance has not been well described, due in part to the complexity of upper extremity tasks. In this pilot study, we elucidated proximal–distal interactions and their functional impact on stroke survivors by quantitatively delineating how hand and arm movements affect each other across different phases of functional task performance, and how these interactions are influenced by stroke. Fourteen subjects, including nine chronic stroke survivors and five neurologically-intact subjects participated in an experiment involving transport and release of cylindrical objects between locations requiring distinct proximal kinematics. Distal kinematics of stroke survivors, particularly hand opening, were significantly affected by the proximal kinematics, as the hand aperture decreased and the duration of hand opening increased at the locations that requires shoulder abduction and elbow extension. Cocontraction of the extrinsic hand muscles of stroke survivors significantly increased at these locations, where an increase in the intermuscular coherence between distal and proximal muscles was observed. Proximal kinematics of stroke survivors was also affected by the finger extension, but the cocontraction of their proximal muscles did not significantly increase, suggesting the changes in the proximal kinematics were made voluntarily. Our results showed significant proximal-to-distal interactions between finger extension and elbow extension/shoulder abduction of stroke survivors exist during their functional movements. Increased cocontraction of the hand muscles due to increased neural couplings between the distal and proximal muscles appears to be the underlying mechanism.}, journal={FRONTIERS IN HUMAN NEUROSCIENCE}, author={Phan, Thanh and Nguyen, Hien and Vermillion, Billy C. and Kamper, Derek G. and Lee, Sang Wook}, year={2022}, month={Nov} }
 @article{barry_kamper_stoykov_triandafilou_roth_2022, title={Characteristics of the severely impaired hand in survivors of stroke with chronic impairments}, volume={29}, ISSN={["1945-5119"]}, DOI={10.1080/10749357.2021.1894660}, abstractNote={ABSTRACT Background Diminished sensorimotor control of the hand is one of the most common outcomes following stroke. This hand impairment substantially impacts overall function and quality of life; standard therapy often results in limited improvement. Mechanisms of dysfunction of the severely impaired post-stroke hand are still incompletely understood, thereby impeding the development of new targeted treatments. Objective To identify and determine potential relationships among the mechanisms responsible for hand impairment following stroke Methods This cohort study observed stroke survivors (n = 95) with severe, chronic hand impairment (Chedoke-McMaster Hand score = 2–3). Custom instrumentation created precise perturbations and measured kinematic responses. Muscle activation was recorded through electromyography. Strength, spasticity, muscle relaxation time, and muscle coactivation were quantified. Results Maximum grip strength in the paretic hand was only 12% of that achieved by the nonparetic hand, and only 6 of 95 participants were able to produce any net extension force. Despite force deficits, spastic reflex response of the finger flexor evoked by imposed stretch averaged 90.1 ± 26.8% of maximum voluntary activation, relaxation time averaged 3.8 ± 0.8 seconds, and coactivation during voluntary extension exceeded 30% of maximum contraction, thereby resulting in substantial net flexion. Surprisingly, these hypertonicity measures were not significantly correlated with each other. Conclusions Survivors of severe, chronic hemiparetic stroke experience profound weakness of both flexion and extension that arises from increased involuntary antagonist activation and decreased voluntary activation. The lack of correlation amongst hypertonicity measures suggests that these phenomena may arise from multiple, potentially independent mechanisms that could require different treatments.}, number={3}, journal={TOPICS IN STROKE REHABILITATION}, author={Barry, Alexander J. and Kamper, Derek G. and Stoykov, Mary Ellen and Triandafilou, Kristen and Roth, Elliot}, year={2022}, month={Apr}, pages={181–191} }
 @article{seo_kamper_ramakrishnan_harvey_finetto_schranz_scronce_coupland_howard_blaschke_et al._2022, title={Effect of novel training to normalize altered finger force direction post-stroke: study protocol for a double-blind randomized controlled trial}, volume={23}, ISSN={["1745-6215"]}, DOI={10.1186/s13063-022-06224-w}, abstractNote={Abstract Background Functional task performance requires proper control of both movement and force generation in three-dimensional space, especially for the hand. Control of force in three dimensions, however, is not explicitly treated in current physical rehabilitation. To address this gap in treatment, we have developed a tool to provide visual feedback on three-dimensional finger force. Our objective is to examine the effectiveness of training with this tool to restore hand function in stroke survivors. Methods Double-blind randomized controlled trial. All participants undergo 18 1-h training sessions to practice generating volitional finger force of various target directions and magnitudes. The experimental group receives feedback on both force direction and magnitude, while the control group receives feedback on force magnitude only. The primary outcome is hand function as measured by the Action Research Arm Test. Other outcomes include the Box and Block Test, Stroke Impact Scale, ability to direct finger force, muscle activation pattern, and qualitative interviews. Discussion The protocol for this clinical trial is described in detail. The results of this study will reveal whether explicit training of finger force direction in stroke survivors leads to improved motor control of the hand. This study will also improve the understanding of neuromuscular mechanisms underlying the recovery of hand function. Trial registration ClinicalTrials.gov NCT03995069 . Registered on June 21, 2019}, number={1}, journal={TRIALS}, author={Seo, Na Jin and Kamper, Derek G. and Ramakrishnan, Viswanathan and Harvey, Jillian B. and Finetto, Christian and Schranz, Christian and Scronce, Gabrielle and Coupland, Kristen and Howard, Keith and Blaschke, Jenna and et al.}, year={2022}, month={Apr} }
 @article{mccall_hu_kamper_2022, title={Exploring Kinetic and Kinematic Finger Individuation Capability in Children With Hemiplegic Cerebral Palsy}, ISSN={["1558-688X"]}, DOI={10.1177/00315125221145220}, abstractNote={While fine manual dexterity develops over time, the extent to which children show independent control of their digits in each hand and the impact of perinatal brain injury on this individuation have not been well quantified. Our goal in this study was to assess and compare finger force and movement individuation in 8–14 year old children with hemiplegic cerebral palsy (hCP; n = 4) and their typically developing peers (TD; n = 10). We evaluated finger force individuation with five independent load cells and captured joint movement individuation with video tracking. We observed no significant differences in individuation indices between the dominant and non-dominant hands of TD children, but individuated force and movement were substantially reduced in the paretic versus non paretic hands of children with hCP (p < 0.001). In TD participants, the thumb tended to have the greatest level of independent control. This small sample of children with hCP showed substantial loss of individuation in the paretic hand and some deficits in the non-paretic hand, suggesting possible benefit from targeted training of digit independence in both hands for children with CP.}, journal={PERCEPTUAL AND MOTOR SKILLS}, author={McCall, James V. and Hu, Xiaogang and Kamper, Derek G.}, year={2022}, month={Dec} }
 @misc{mccall_ludovice_elliott_kamper_2022, title={Hand function development of children with hemiplegic cerebral palsy: A scoping review}, volume={15}, ISSN={["1875-8894"]}, DOI={10.3233/PRM-200714}, abstractNote={PURPOSE
Hemiplegic cerebral palsy (hCP) typically impacts sensorimotor control of the hand, but comprehensive assessments of the hands of children with hCP are relatively rare. This scoping review summarizes the development of hand function for children with hCP.


METHODS
This scoping review focused on the development of hand function in children with hCP. Electronic databases (PubMed, PEDro, Web of Science, CINAHL, and SpringerLink) were searched to identify studies assessing hand function in children with hCP. The search was performed using keywords (e.g., "hemiplegia"). An iterative approach verified by two authors was used to select the studies. Articles which reported quantitative data for children with hCP on any items of a specified set of hand evaluations were included. Measures were sorted into three categories: quantitative neuromechanics, clinical assessments, and clinical functional evaluations.


RESULTS
Initial searches returned 1536 articles, 131 of which were included in the final review. Trends between assessment scores and age were examined for both hands.


CONCLUSION
While several studies have evaluated hand function in children with hCP, the majority relied on clinical scales, assessments, or qualitative descriptions. Further assessments of kinematics, kinetics, and muscle activation patterns are needed to identify the underlying impairment mechanisms that should be targeted for treatment.}, number={1}, journal={JOURNAL OF PEDIATRIC REHABILITATION MEDICINE}, author={McCall, James V and Ludovice, Miranda C. and Elliott, Catherine and Kamper, Derek G.}, year={2022}, pages={211–228} }
 @article{flint_li_wang_vaidya_barry_ghassemi_tomic_brkic_ripley_liu_et al._2022, title={Noninvasively recorded high-gamma signals improve synchrony of force feedback in a novel neurorehabilitation brain-machine interface for brain injury}, volume={19}, ISSN={["1741-2552"]}, DOI={10.1088/1741-2552/ac7004}, abstractNote={Objective. Brain injury is the leading cause of long-term disability worldwide, often resulting in impaired hand function. Brain–machine interfaces (BMIs) offer a potential way to improve hand function. BMIs often target replacing lost function, but may also be employed in neurorehabilitation (nrBMI) by facilitating neural plasticity and functional recovery. Here, we report a novel nrBMI capable of acquiring high-γ (70–115 Hz) information through a unique post-traumatic brain injury (TBI) hemicraniectomy window model, and delivering sensory feedback that is synchronized with, and proportional to, intended grasp force. Approach. We developed the nrBMI to use electroencephalogram recorded over a hemicraniectomy (hEEG) in individuals with TBI. The nrBMI empowered users to exert continuous, proportional control of applied force, and provided continuous force feedback. We report the results of an initial testing group of three human participants with TBI, along with a control group of three skull- and motor-intact volunteers. Main results. All participants controlled the nrBMI successfully, with high initial success rates (2 of 6 participants) or performance that improved over time (4 of 6 participants). We observed high-γ modulation with force intent in hEEG but not skull-intact EEG. Most significantly, we found that high-γ control significantly improved the timing synchronization between neural modulation onset and nrBMI output/haptic feedback (compared to low-frequency nrBMI control). Significance. These proof-of-concept results show that high-γ nrBMIs can be used by individuals with impaired ability to control force (without immediately resorting to invasive signals like electrocorticography). Of note, the nrBMI includes a parameter to change the fraction of control shared between decoded intent and volitional force, to adjust for recovery progress. The improved synchrony between neural modulations and force control for high-γ signals is potentially important for maximizing the ability of nrBMIs to induce plasticity in neural circuits. Inducing plasticity is critical to functional recovery after brain injury.}, number={3}, journal={JOURNAL OF NEURAL ENGINEERING}, author={Flint, Robert D. and Li, Yongcheng and Wang, Po T. and Vaidya, Mukta and Barry, Alex and Ghassemi, Mohammad and Tomic, Goran and Brkic, Nenad and Ripley, David and Liu, Charles and et al.}, year={2022}, month={Jun} }
 @article{vargas_huang_zhu_kamper_hu_2022, title={Resembled Tactile Feedback for Object Recognition Using a Prosthetic Hand}, volume={7}, ISSN={["2377-3766"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85136090957&partnerID=MN8TOARS}, DOI={10.1109/LRA.2022.3196958}, abstractNote={Tactile feedback in the hand is essential for interaction with objects. Here, we evaluated how artificial tactile sensation affected the recognition of object properties using a myoelectrically controlled prosthetic hand. Electromyogram signals from the flexor and extensor finger muscles were used to continuously control either prosthetic joint velocity or position. Participants grasped objects of varying shape or size using the prosthetic hand. Tactile feedback was evoked by transcutaneous nerve stimulation along the participant's upper arm and modulated based on the prosthetic-object contact force. Multi-channel electrical stimulation targeted the median and ulnar nerve bundles to produce resembled tactile sensations at distinct hand regions. The results showed that participants could gauge the onset timing of tactile feedback to discern object shape and size. We also found that the position-controller led to a greater recognition accuracy of object size compared with velocity-control, potentially due to supplemental joint position information from muscle activation level. Our findings demonstrate that non-invasive tactile feedback can enable effective object shape and size recognition during prosthetic control. The evaluation of tactile feedback across myoelectric controllers can help understand the interplay between sensory and motor pathways involved in the control of assistive devices.}, number={4}, journal={IEEE ROBOTICS AND AUTOMATION LETTERS}, author={Vargas, Luis and Huang, He and Zhu, Yong and Kamper, Derek and Hu, Xiaogang}, year={2022}, month={Oct}, pages={10977–10984} }
 @article{hinson jr_saul_kamper_huang_2022, title={Sensitivity analysis guided improvement of an electromyogram-driven lumped parameter musculoskeletal hand model}, volume={141}, ISSN={["1873-2380"]}, url={http://dx.doi.org/10.1016/j.jbiomech.2022.111200}, DOI={10.1016/j.jbiomech.2022.111200}, abstractNote={EMG-driven neuromusculoskeletal models have been used to study many impairments and hold great potential to facilitate human–machine interactions for rehabilitation. A challenge to successful clinical application is the need to optimize the model parameters to produce accurate kinematic predictions. In order to identify the key parameters, we used Monte-Carlo simulations to evaluate the sensitivities of wrist and metacarpophalangeal (MCP) flexion/extension prediction accuracies for an EMG-driven, lumped-parameter musculoskeletal model. Four muscles were modeled with 22 total optimizable parameters. Model predictions from EMG were compared with measured joint angles from 11 able-bodied subjects. While sensitivities varied by muscle, we determined muscle moment arms, maximum isometric force, and tendon slack length were highly influential, while passive stiffness and optimal fiber length were less influential. Removing the two least influential parameters from each muscle reduced the optimization search space from 22 to 14 parameters without significantly impacting prediction correlation (wrist: 0.90 ± 0.05 vs 0.90 ± 0.05, p = 0.96; MCP: 0.74 ± 0.20 vs 0.70 ± 0.23, p = 0.51) and normalized root mean square error (wrist: 0.18 ± 0.03 vs 0.19 ± 0.03, p = 0.16; MCP: 0.18 ± 0.06 vs 0.19 ± 0.06, p = 0.60). Additionally, we showed that wrist kinematic predictions were insensitive to parameters of the modeled MCP muscles. This allowed us to develop a novel optimization strategy that more reliably identified the optimal set of parameters for each subject (27.3 ± 19.5%) compared to the baseline optimization strategy (6.4 ± 8.1%; p = 0.004). This study demonstrated how sensitivity analyses can be used to guide model refinement and inform novel and improved optimization strategies, facilitating implementation of musculoskeletal models for clinical applications.}, journal={JOURNAL OF BIOMECHANICS}, publisher={Elsevier BV}, author={Hinson Jr, Robert Jr and Saul, Katherine and Kamper, Derek and Huang, He}, year={2022}, month={Aug} }
 @article{kamper_barry_bansal_stoykov_triandafilou_vidakovic_seo_roth_2022, title={Use of cyproheptadine hydrochloride (HCl) to reduce neuromuscular hypertonicity in stroke survivors: A Randomized Trial}, volume={31}, ISSN={["1532-8511"]}, DOI={10.1016/j.jstrokecerebrovasdis.2022.106724}, abstractNote={The goal of this study was to examine how the administration and dosing of the anti-serotonergic medication cyproheptadine hydrochloride (HCl) affects involuntary muscle hypertonicity of the spastic and paretic hands of stroke survivors.A randomized, double-blinded, placebo-controlled longitudinal intervention study was performed as a component of a larger clinical trial. 94 stroke survivors with chronic, severe hand impairment, rated as levels 2 or 3 on the Chedoke-McMaster Stroke Assessment Stage of Hand (CMSA-H), were block randomized to groups receiving doses of cyproheptadine HCl or matched doses of placebo. Doses were increased from 4 mg BID to 8 mg TID over 3 weeks. Outcomes were assessed at baseline and after each of the three weeks of intervention. Primary outcome measure was grip termination time; other measures included muscle strength, spasticity, coactivation of the long finger flexors, and recording of potential adverse effects such as sleepiness and depression.89 participants (receiving cyproheptadine HCl: 44, receiving placebo: 45) completed the study. The Cyproheptadine group displayed significant reduction in grip termination time, in comparison with the Placebo group (p<0.05). Significant change in the Cyproheptadine group (45% time reduction) was observed after only one week at the 4mg BID dosage. The effect was pronounced for those participants in the Cyproheptadine group with more severe hand impairment (CMSA-H level 2) at baseline. Conversely, no significant effect of Group * Session interaction was observed for spasticity (p=0.6) or coactivation (p=0.53). There were no significant changes in strength (p=0.234) or depression (p=0.441) during the trial.Use of cyproheptadine HCl was associated with a significant reduction in relaxation time of finger flexor muscles, without adversely affecting voluntary strength, although spasticity and coactivation were unchanged. Decreasing the duration of involuntary flexor activity can facilitate object release and repeated prehensile task performance.Clinical Trial number: NCT02418949.}, number={10}, journal={JOURNAL OF STROKE & CEREBROVASCULAR DISEASES}, author={Kamper, Derek and Barry, Alexander and Bansal, Naveen and Stoykov, Mary Ellen and Triandafilou, Kristen and Vidakovic, Lynn and Seo, NaJin and Roth, Elliot}, year={2022}, month={Oct} }
 @article{zheng_shin_kamper_hu_2021, title={Automatic Detection of Contracting Muscle Regions via the Deformation Field of Transverse Ultrasound Images: A Feasibility Study}, volume={49}, ISSN={["1573-9686"]}, DOI={10.1007/s10439-020-02557-2}, abstractNote={Accurate identification of contracting muscles can help us to understand the muscle function in both physiological and pathological conditions. Conventional electromyography (EMG) have limited access to deep muscles, crosstalk, or instability in the recordings. Accordingly, a novel framework was developed to detect contracting muscle regions based on the deformation field of transverse ultrasound images. We first estimated the muscle movements in a stepwise calculation, to derive the deformation field. We then calculated the divergence of the deformation field to locate the expanding or shrinking regions during muscle contractions. Two preliminary experiments were performed to evaluate the feasibility of the developed algorithm. Using concurrent intramuscular EMG recordings, Experiment I verified that the divergence map can capture the activity of superficial and deep muscles, when muscles were activated voluntarily or through electrical stimulation. Experiment II verified that the divergence map can only capture contracting muscles but not muscle shortening during passive movements. The results demonstrated that the divergence can individually capture the activity of muscles at different depths, and was not sensitive to muscle shortening during passive movements. The proposed framework can automatically detect the regions of contracting muscle, and could potentially serve as a tool to assess the functions of a group of muscles concurrently.}, number={1}, journal={ANNALS OF BIOMEDICAL ENGINEERING}, author={Zheng, Yang and Shin, Henry and Kamper, Derek G. and Hu, Xiaogang}, year={2021}, month={Jan}, pages={354–366} }
 @article{mccall_kamper_2021, title={High Compliance Pneumatic Actuators to Promote Finger Extension in Stroke Survivors}, ISSN={["1558-4615"]}, DOI={10.1109/EMBC46164.2021.9629782}, abstractNote={Compliant pneumatic systems are well suited for wearable robotic applications. The actuators are lightweight, conformable to irregular shapes, and tolerant of uncontrolled degrees of freedom. These attributes are especially desirable for hand exoskeletons given their space and mass constraints. Creating active digit extension with these exoskeletons is especially critical for clinical populations such as stroke survivors who often have great difficulty opening their paretic hand. To achieve active digit extension with a soft actuator, we have created pneumatic chambers that lie along the palmar surface of the digits. These chambers can directly extend the digits when pressurized. We present a characterization of the extension force and passive flexion resistance generated by these pneumatic chambers across a range of joint angles as a function of cross-sectional shape, dimension, and wall thickness. The chambers were fabricated out of DragonSkin 20 using custom molds and were tested on a custom jig. Extension forces created at the end of the chamber (where fingertip contact would occur) exceeded 3.00 N at relatively low pressure (48.3 kPa). A rectangular cross-section generated higher extension force than a semi-obround cross-sectional shape. Extension force was significantly higher (p < 0.05) for actuators with the highest wall thickness compared to those with the thinnest walls. In comparison to previously used polyurethane actuators, the DragonSkin actuators had a much higher extension force for a similar passive bending resistance. Passive bending resistance of the chamber (simulating finger flexion) did not vary significantly with actuator shape, wall thickness, width, or depth. The flexion resistance, however, could be significantly reduced by applying a vacuum. These results provide guidance in designing pneumatic actuators for assisting finger extension and resisting unwanted flexion in the fingers.}, journal={2021 43RD ANNUAL INTERNATIONAL CONFERENCE OF THE IEEE ENGINEERING IN MEDICINE & BIOLOGY SOCIETY (EMBC)}, author={McCall, James V and Kamper, Derek G.}, year={2021}, pages={4588–4591} }
 @misc{vertongen_kamper_smit_vallery_2021, title={Mechanical Aspects of Robot Hands, Active Hand Orthoses, and Prostheses: A Comparative Review}, volume={26}, ISSN={["1941-014X"]}, DOI={10.1109/TMECH.2020.3014182}, abstractNote={The large interest in robot hands and active hand prostheses has in recent years been joined by that in active hand orthoses. Despite the differences in intended uses, these three categories of artificial hand devices share key characteristics. Examination of the commonalities could stimulate future design. Thus, in this article, we undertook a comparative review of publications describing robot hands, active prostheses, and active orthoses, with a focus on mechanical structure, actuation principle, and transmission. Out of a total of 510 papers identified through the literature search, 72 publications were included in a focused examination. We identified trends in the design of artificial hands and gaps in the literature. After comparing their mechanical aspects, we propose recommendations for future development.}, number={2}, journal={IEEE-ASME TRANSACTIONS ON MECHATRONICS}, author={Vertongen, Jens and Kamper, Derek G. and Smit, Gerwin and Vallery, Heike}, year={2021}, month={Apr}, pages={955–965} }
 @article{thielbar_triandafilou_barry_yuan_nishimoto_johnson_stoykov_tsoupikova_kamper_2020, title={Home-based Upper Extremity Stroke Therapy Using a Multiuser Virtual Reality Environment: A Randomized Trial}, volume={101}, ISSN={["1532-821X"]}, DOI={10.1016/j.apmr.2019.10.182}, abstractNote={To compare participation and subjective experience of participants in both home-based multiuser virtual reality (VR) therapy and home-based single-user (SU) VR therapy.Crossover, randomized trial.Initial training and evaluations occurred in a rehabilitation hospital; the interventions took place in participants' homes.Survivors of stroke with chronic upper extremity impairment (N=20).Four weeks of in-home treatment using a custom, multiuser virtual reality system (VERGE): 2 weeks of both multiuser (MU) and SU versions of VERGE. The order of presentation of SU and MU versions was randomized such that participants were divided into 2 groups, First MU and First SU.We measured arm displacement during each session (m) as the primary outcome measure. Secondary outcome measures include time participants spent using each MU and SU VERGE and Intrinsic Motivation Inventory scores. Fugl-Meyer Assessment of Motor Recovery After Stroke Upper Extremity (FMA-UE) score and compliance with prescribed training were also evaluated. Measures were recorded before, midway, and after the treatment. Activity and movement were measured during each training session.Arm displacement during a session was significantly affected the mode of therapy (MU: 414.6m, SU: 327.0m, P=.019). Compliance was very high (99% compliance for MU mode and 89% for SU mode). Within a given session, participants spent significantly more time training in the MU mode than in the SU mode (P=.04). FMA-UE score improved significantly across all participants (Δ3.2, P=.001).Multiuser VR exercises may provide an effective means of extending clinical therapy into the home.}, number={2}, journal={ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION}, author={Thielbar, Kelly O. and Triandafilou, Kristen M. and Barry, Alexander J. and Yuan, Ning and Nishimoto, Arthur and Johnson, Joelle and Stoykov, Mary Ellen and Tsoupikova, Daria and Kamper, Derek G.}, year={2020}, month={Feb}, pages={196–203} }
 @article{lee_qiu_fischer_conrad_kamper_2020, title={Modulation of finger muscle activation patterns across postures is coordinated across all muscle groups}, volume={124}, ISSN={["1522-1598"]}, DOI={10.1152/jn.00088.2020}, abstractNote={Successful grasp requires that grip forces be properly directed between the fingertips and the held object. Changes in digit posture significantly affect the mapping between muscle force and fingertip force. Joint torques must subsequently be altered to maintain the desired force direction at the fingertips. Our current understanding of the roles of hand muscles in force production remains incomplete, as past studies focused on a limited set of postures or force directions. To thoroughly examine how hand muscles adapt to changing external (force direction) and internal (posture) conditions, activation patterns of six index finger muscles were examined with intramuscular electrodes in 10 healthy subjects. Participants produced submaximal isometric forces in each of six orthogonal directions at 9 different finger postures. Across force directions, participants significantly altered activation patterns to accommodate postural changes in the interphalangeal joint angles, but not changes in the metacarpophalangeal joint angles. Modulation of activation levels of the extrinsic hand muscles, particularly the extensors, were as great as those of intrinsic muscles, suggesting that both extrinsic/intrinsic muscles were involved in creating the desired forces. Despite considerable between-subject variation in the absolute activation patterns, PCA revealed that participants used similar strategies to accommodate the postural changes. The changes in muscle coordination also helped increase joint impedance to stabilize the endpoint force direction, counteracting the increased signal-dependent motor noise that arises with greater magnitude of muscle activation as interphalangeal joints flexed. These results highlight the role of the extrinsic muscles in controlling fingertip force direction across finger postures.}, number={2}, journal={JOURNAL OF NEUROPHYSIOLOGY}, author={Lee, Sang Wook and Qiu, Dan and Fischer, Heidi C. and Conrad, Megan O. and Kamper, Derek G.}, year={2020}, month={Aug}, pages={330–341} }
 @article{barry_triandafilou_stoykov_bansal_roth_kamper_2020, title={Survivors of Chronic Stroke Experience Continued Impairment of Dexterity But Not Strength in the Nonparetic Upper Limb}, volume={101}, ISSN={["1532-821X"]}, DOI={10.1016/j.apmr.2020.01.018}, abstractNote={Objective To investigate the performance of the less affected upper limb in people with stroke compared with normative values. To examine less affected upper limb function in those whose prestroke dominant limb became paretic and those whose prestroke nondominant limb became paretic. Design Cohort study of survivors of chronic stroke (7.2±6.7y post incident). Setting The study was performed at a freestanding academic rehabilitation hospital. Participants Survivors of chronic stroke (N=40) with severe hand impairment (Chedoke-McMaster Stroke Assessment rating of 2-3 on Stage of Hand) participated in the study. In 20 participants the prestroke dominant hand (DH) was tested (nondominant hand [NH] affected by stroke), and in 20 participants the prestroke NH was tested (DH affected by stroke). Interventions Not applicable. Main Outcome Measure Jebsen-Taylor Hand Function Test. Data from survivors of stroke were compared with normative age- and sex-matched data from neurologically intact individuals. Results When combined, DH and NH groups performed significantly worse on fine motor tasks with their nonparetic hand relative to normative data (P<.007 for all measures). Even the participants who continued to use their prestroke DH as their primary hand after the stroke demonstrated reduced fine motor skills compared with normative data. In contrast, grip strength was not significantly affected in either group of survivors of stroke (P>.140). Conclusions Survivors of stroke with severe impairment of the paretic limb continue to present significant upper extremity impairment in their nominally nonparetic limb even years after stroke. This phenomenon was observed regardless of whether the DH or NH hand was primarily affected. Because this group of survivors of stroke is especially dependent on the nonparetic limb for performing functional tasks, our results suggest that the nonparetic upper limb should be targeted for rehabilitation.}, number={7}, journal={ARCHIVES OF PHYSICAL MEDICINE AND REHABILITATION}, author={Barry, Alexander J. and Triandafilou, Kristen M. and Stoykov, Mary Ellen and Bansal, Naveen and Roth, Elliot J. and Kamper, Derek G.}, year={2020}, month={Jul}, pages={1170–1175} }
 @article{thielbar_spencer_tsoupikova_ghassemi_kamper_2020, title={Utilizing multi-user virtual reality to bring clinical therapy into stroke survivors' homes}, volume={33}, ISSN={["1545-004X"]}, DOI={10.1016/j.jht.2020.01.006}, abstractNote={Introduction Lifespans after the occurrence of a stroke have been lengthening, but most stroke survivors will experience chronic impairment. Directed, repetitive practice may reduce deficits, but clinical access is often limited by a variety of factors, such as transportation. Purpose of the Study To introduce a multiuser virtual reality platform that can be used to promote therapist-client interactions when the client is at home. Methods The Virtual Environment for Rehabilitative Gaming Exercises encourages exploration of the hand workspace by enabling multiple participants, located remotely and colocated virtually, to interact with the same virtual objects in the shared virtual space. Each user controls an avatar by corresponding movement of his or her own body segments. System performance with stroke survivors was evaluated during longitudinal studies in a laboratory environment and in participants' homes. Active arm movement was tracked throughout therapy sessions for both studies. Results Stroke survivors achieved considerable arm movement while using the system. Mean voluntary hand displacement, after accounting for trunk displacement, was greater than 350 m per therapy session for the Virtual Environment for Rehabilitative Gaming Exercises system. Compliance for home-based therapy was quite high, with 94% of all scheduled sessions completed. Having multiple players led to longer sessions and more arm movement than when the stroke survivors were trained alone. Conclusions Multiuser virtual reality offers a relatively inexpensive means of extending clinical therapy into home and enabling family and friends to support rehabilitation efforts, even when physically remote from each other.}, number={2}, journal={JOURNAL OF HAND THERAPY}, author={Thielbar, Kelly and Spencer, Nicole and Tsoupikova, Daria and Ghassemi, Mohammad and Kamper, Derek}, year={2020}, pages={246–253} }
 @article{ghassemi_triandafilou_barry_stoykov_roth_mussa-ivaldi_kamper_ranganathan_2019, title={Development of an EMG-Controlled Serious Game for Rehabilitation}, volume={27}, ISSN={["1558-0210"]}, DOI={10.1109/TNSRE.2019.2894102}, abstractNote={A majority of the seven million stroke survivors in the U.S. have hand impairments, adversely affecting performance of a variety of activities of daily living, because of the fundamental role of the hand in performing functional tasks. Disability in stroke survivors is largely attributable to damaged neuronal pathways, which result in inappropriate activation of muscles, a condition prevalent in distal upper extremity muscles following stroke. While conventional rehabilitation methods focus on the amplification of existing muscle activation, the effectiveness of therapy targeting the reorganization of pathological activation patterns is often unexplored. To encourage modulation of activation level and exploration of the activation workspace, we developed a novel platform for playing a serious game through electromyographic control. This system was evaluated by a group of neurologically intact subjects over multiple sessions held on different days. Subjects were assigned to one of two groups, training either with their non-dominant hand only (unilateral) or with both hands (bilateral). Both groups of subjects displayed improved performance in controlling the cursor with their non-dominant hand, with retention from one session to the next. The system holds promise for rehabilitation of control of muscle activation patterns.}, number={2}, journal={IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING}, author={Ghassemi, Mohammad and Triandafilou, Kristen and Barry, Alex and Stoykov, Mary Ellen and Roth, Elliot and Mussa-Ivaldi, Ferdinando A. and Kamper, Derek G. and Ranganathan, Rajiv}, year={2019}, month={Feb}, pages={283–292} }
 @article{vaidya_flint_wang_barry_li_ghassemi_tomic_yao_carmona_mugler_et al._2019, title={Hemicraniectomy in Traumatic Brain Injury: A Noninvasive Platform to Investigate High Gamma Activity for Brain Machine Interfaces}, volume={27}, ISSN={["1558-0210"]}, DOI={10.1109/TNSRE.2019.2912298}, abstractNote={Brain–machine interfaces (BMIs) translate brain signals into control signals for an external device, such as a computer cursor or robotic limb. These signals can be obtained either noninvasively or invasively. Invasive recordings, using electrocorticography (ECoG) or intracortical microelectrodes, provide higher bandwidth and more informative signals. Rehabilitative BMIs, which aim to drive plasticity in the brain to enhance recovery after brain injury, have almost exclusively used non-invasive recordings, such electroencephalography (EEG) or magnetoencephalography (MEG), which have limited bandwidth and information content. Invasive recordings provide more information and spatiotemporal resolution, but do incur risk, and thus are not usually investigated in people with stroke or traumatic brain injury (TBI). Here, in this paper, we describe a new BMI paradigm to investigate the use of higher frequency signals in brain-injured subjects without incurring significant risk. We recorded EEG in TBI subjects who required hemicraniectomies (removal of a part of the skull). EEG over the hemicraniectomy (hEEG) contained substantial information in the high gamma frequency range (65–115 Hz). Using this information, we decoded continuous finger flexion force with moderate to high accuracy (variance accounted for 0.06 to 0.52), which at best approaches that using epidural signals. These results indicate that people with hemicraniectomies can provide a useful resource for developing BMI therapies for the treatment of brain injury.}, number={7}, journal={IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING}, author={Vaidya, Mukta and Flint, Robert D. and Wang, Po T. and Barry, Alex and Li, Yongcheng and Ghassemi, Mohammad and Tomic, Goran and Yao, Jun and Carmona, Carolina and Mugler, Emily M. and et al.}, year={2019}, month={Jul}, pages={1467–1472} }
 @article{barry_murray_kamper_2018, title={Development of a dynamic index finger and thumb model to study impairment}, volume={77}, ISSN={["1873-2380"]}, DOI={10.1016/j.jbiomech.2018.06.017}, abstractNote={Modeling of the human hand provides insight for explaining deficits and planning treatment following injury. Creation of a dynamic model, however, is complicated by the actions of multi-articular tendons and their complex interactions with other soft tissues in the hand. This study explores the creation of a musculoskeletal model, including the thumb and index finger, to explore the effects of muscle activation deficits. The OpenSim model utilizes physiological axes of rotation at all joints, passive joint torques, and appropriate moment arms. The model was validated through comparison with kinematic and kinetic experimental data. Simulated fingertip forces resulting from modeled musculotendon loading largely fell within one standard deviation of experimental ranges for most index finger and thumb muscles, although agreement in the sagittal plane was generally better than for the coronal plane. Input of experimentally obtained electromyography data produced the expected simulated finger and thumb motion. Use of the model to predict the effects of activation deficits on pinch force production revealed that the intrinsic muscles, especially first dorsal interosseous (FDI) and adductor pollicis (ADP), had a substantial impact on the resulting fingertip force. Reducing FDI activation, such as might occur following stroke, altered fingertip force direction by up to 83° for production of a dorsal fingertip force; reducing ADP activation reduced force production in the thumb by up to 62%. This validated model can provide a means for evaluating clinical interventions.}, journal={JOURNAL OF BIOMECHANICS}, author={Barry, Alexander J. and Murray, Wendy M. and Kamper, Derek G.}, year={2018}, month={Aug}, pages={206–210} }
 @article{lee_vermillion_geed_dromerick_kamper_2018, title={Impact of Targeted Assistance of Multiarticular Finger Musculotendons on the Coordination of Finger Muscles During Isometric Force Production}, volume={26}, ISSN={["1558-0210"]}, DOI={10.1109/tnsre.2018.2800052}, abstractNote={Neurological injuries often cause degraded motor control. While rehabilitation efforts typically focus on movement kinematics, abnormal muscle activation patterns are often the primary source of impairment. Muscle-based therapies are likely more effective than joint-based therapy. In this paper, we examined the feasibility of biomimetic input mimicking the action of human musculotendons in altering hand muscle coordination. Twelve healthy subjects produced a submaximal isometric dorsal fingertip force, while a custom actuator provided assistance mirroring the actions of either the extrinsic extensor or the intrinsic muscles of the index finger. The biomimetic inputs reduced the activation level of all task-related muscles, but the degree of change was different across the muscles, resulting in significant changes in their coordination (co-contraction ratios) and force-electromyography correlations. Each biomimetic assistance particularly increased the neural coupling between its targeted muscle and the antagonist muscle. Subjects appeared to fully take advantage of the assistance, as they provided minimal level of effort to achieve the task goal. The targeted biomimetic assistance may be used to retrain activation patterns post-stroke by effectively modulating connectivity between the muscles in the functional context and could be beneficial to restore hand function and reduce disability.}, number={3}, journal={IEEE TRANSACTIONS ON NEURAL SYSTEMS AND REHABILITATION ENGINEERING}, author={Lee, Sang Wook and Vermillion, Billy C. and Geed, Shashwati and Dromerick, Alexander W. and Kamper, Derek G.}, year={2018}, month={Mar}, pages={619–628} }
 @article{conrad_qiu_hoffmann_zhou_kamper_2017, title={Analysis of muscle fiber conduction velocity during finger flexion and extension after stroke}, volume={24}, ISSN={1074-9357 1945-5119}, url={http://dx.doi.org/10.1080/10749357.2016.1277482}, DOI={10.1080/10749357.2016.1277482}, abstractNote={Abstract Background: Stroke survivors experience greater strength deficits during finger extension than finger flexion. Prior research indicates relatively little observed weakness is directly attributable to muscle atrophy. Changes in other muscle properties, however, may contribute to strength deficits. Objectives: This study measured muscle fiber conduction velocity (MFCV) in a finger flexor and extensor muscle to infer changes in muscle fiber-type after stroke. Methods: Conduction velocity was measured using a linear EMG surface electrode array for both extensor digitorum communis and flexor digitorum superficialis in 12 stroke survivors with chronic hand hemiparesis and five control subjects. Measurements were made in both hands for all subjects. Stroke survivors had either severe (n = 5) or moderate (n = 7) hand impairment. Results: Absolute MFCV was significantly lower in the paretic hand of severely impaired stroke patients compared to moderately impaired patients and healthy control subjects. The relative MFCV between the two hands, however, was quite similar for flexor muscles across all subjects and for extensor muscles for the neurologically intact control subjects. However, MFCV for finger extensors was smaller in the paretic as compared to the nonparetic hand for both groups of stroke survivors. Conclusions: One explanation for reduced MFCV may be a type-II to type-I muscle fiber, especially in extrinsic extensors. Clinically, therapists may use this information to develop therapeutic exercises targeting loss of type-II fiber in extensor muscles.}, number={4}, journal={Topics in Stroke Rehabilitation}, publisher={Informa UK Limited}, author={Conrad, Megan O. and Qiu, Dan and Hoffmann, Gilles and Zhou, Ping and Kamper, Derek G.}, year={2017}, month={Jan}, pages={262–268} }
 @inproceedings{hollingshead_henry-etesse_tankere_kamper_tan_2017, title={Characterization of hysteresis in resistive bend sensors}, DOI={10.1109/werob.2017.8383842}, abstractNote={Sensing of finger joint rotation can be difficult due to the hand's many degrees-of-freedom within a small space. The low profile and lightweight of resistive bend sensors make their use in measuring joint rotation an option. Certain properties of the bend sensors have been investigated, however investigation of the effect of hysteresis when bending and straightening the sensor has not been investigated. In this study, two inch resistive sensors were bent from 0° to 90° and back to 0° while measuring the voltage output. Three calibration models were fitted to the measured data and used to determine the sensor's accuracy and hysteresis effects. Both the quadratic and cubic fits demonstrated strong non-monotonic behavior at low bend angles. Using the exponential model, a hysteresis effect of 9.2% was observed. Accuracy at low bend angles improved by approximately 5° when the effect of hysteresis was considered.}, booktitle={2017 International Symposium on Wearable Robotics and Rehabilitation (WEROB)}, author={Hollingshead, R. L. and Henry-Etesse, L. and Tankere, E. and Kamper, D. and Tan, T.}, year={2017}, pages={54–55} }
 @article{qiu_lee_amine_kamper_2017, title={Intersegmental kinetics significantly impact mapping from finger musculotendon forces to fingertip forces}, volume={65}, ISSN={0021-9290}, url={http://dx.doi.org/10.1016/J.JBIOMECH.2017.10.004}, DOI={10.1016/J.JBIOMECH.2017.10.004}, abstractNote={Predicting the fingertip force vector resulting from excitation of a given muscle remains a challenging but essential task in finger biomechanical modeling. While the conversion of musculotendon force to fingertip force can significantly be affected by finger posture, current techniques utilizing geometric moment arms may not capture such complex postural effects. Here, we attempted to elucidate the postural effects on the mapping between musculotendon force and fingertip force through in vitro experiments. Computer-controlled tendon loading was implemented on the 7 index finger musculotendons of 5 fresh-frozen cadaveric hands across different postures. The resulting fingertip forces/moments were used to compute the effective static moment arm (ESMA), relating tendon force to joint torque, at each joint. The ESMAs were subsequently modeled in three different manners: independent of joint angle; dependent only upon the corresponding joint angle; or dependent upon all joint angles. We found that, for the reconstruction of the fingertip force vector, the multi-joint ESMA model yielded the best outcome, both in terms of direction and magnitude of the vector (mean reconstruction error <4° in direction and <2% in the magnitude), which indicates that intersegmental force transmission through a joint is affected by the posture of neighboring joints. Interestingly, the ESMA model that considers geometric changes of individual joints, the standard model used in biomechanical stimulations, often yielded worse reconstruction results than the simple constant-value ESMA model. Our results emphasize the importance of accurate description of the multi-joint dependency of the conversion of tendon force to joint moment for proper prediction of fingertip force direction.}, journal={Journal of Biomechanics}, publisher={Elsevier BV}, author={Qiu, Dan and Lee, Sang Wook and Amine, Mukarram and Kamper, Derek G.}, year={2017}, month={Dec}, pages={82–88} }
 @inbook{ghassemi_ranganathan_barry_triandafilou_kamper_2017, title={Introduction of an EMG-Controlled Game to Facilitate Hand Rehabilitation After Stroke}, ISBN={9783319466682 9783319466699}, ISSN={2195-3562 2195-3570}, url={http://dx.doi.org/10.1007/978-3-319-46669-9_75}, DOI={10.1007/978-3-319-46669-9_75}, abstractNote={Stroke survivors often have difficulty creating the proper muscle activation patterns to perform functional tasks. We have developed an electromyographically (EMG)-controlled game to assist stroke survivors in rehabilitating activation patterns. Players must produce specific EMG patterns in order to move a cursor throughout a computer screen. We ran a pilot study with neurologically intact subjects playing the game on three separate days. Significant carryover in improvement of activation was seen from one day to the next.}, booktitle={Converging Clinical and Engineering Research on Neurorehabilitation II}, publisher={Springer International Publishing}, author={Ghassemi, Mohammad and Ranganathan, Rajiv and Barry, Alex and Triandafilou, K. and Kamper, Derek}, year={2017}, pages={451–455} }
 @inproceedings{qian_anjos_balasubramanian_stilson_balcer_hatsopoulos_kamper_2017, title={Using monkey hand exoskeleton to explore finger passive joint movement response in primary motor cortex}, DOI={10.1109/embc.2017.8037642}, abstractNote={While neurons in primary motor cortex (M1) have been shown to respond to sensory stimuli, exploration of this phenomenon has proven challenging. Accurate and repeatable presentation of sensory inputs is difficult. Here, we describe a novel paradigm to study response to joint motion and fingertip force. We employed a custom exoskeleton to drive index finger metacarpophalangeal joint (MCP) of a macaque to follow sinusoid trajectories at 4 different frequencies (0.2, 0.5, 1, 2Hz) and 2 movement ranges (68.4, 34.2 degrees). We highlight results of a specific M1 unit that displayed sensitivity to direction (more active during flexion than extension), frequency (greater firing rate at higher frequencies), and movement amplitude (higher rate at larger amplitude). Joint movement trajectories were accurately reconstructed from this single unit with mean R2 =0.64 ± 0.13. The exoskeleton holds promise for examination of sensory feedback. In addition, it can be used as an external device controlled by a brain-machine interface (BMI) system. The proprioceptive related units in M1 may contribute to improving BMI control performance.}, booktitle={Proceedings of annual international conference of the ieee engineering}, author={Qian, K. and Anjos, L. A. and Balasubramanian, K. and Stilson, K. and Balcer, C. and Hatsopoulos, N. G. and Kamper, D. G.}, year={2017}, pages={3624–3627} }
 @article{wang_jones_shastri_qian_kamper_sarkar_2016, title={Design and evaluation of an actuated exoskeleton for examining motor control in stroke thumb}, volume={30}, ISSN={0169-1864 1568-5535}, url={http://dx.doi.org/10.1080/01691864.2015.1105867}, DOI={10.1080/01691864.2015.1105867}, abstractNote={Chronic hand impairment is common following stroke. This paper presents an actuated thumb exoskeleton (ATX) to facilitate research in examining motor control and hand rehabilitation. The ATX presented in this work aims to provide independent bi-directional actuation in each of the 5 degrees of freedom (DOF) of the thumb using a novel flexible shaft-based mechanism that has 5 active DOF and 3 passive DOF. A prototype has been built and experiments have been conducted to measure the allowable workspace at the thumb and evaluate the kinematic and kinetic performance of the ATX. The experimental results show that the ATX is able to provide individual actuation at all five thumb joints with high joint velocity and torque capacities. Further improvement and future work are discussed.}, number={3}, journal={Advanced Robotics}, publisher={Informa UK Limited}, author={Wang, Furui and Jones, Christopher L. and Shastri, Milind and Qian, Kai and Kamper, Derek G. and Sarkar, Nilanjan}, year={2016}, month={Feb}, pages={165–177} }
 @article{tsoupikova_stoykov_corrigan_thielbar_vick_li_triandafilou_preuss_kamper_2015, title={Virtual Immersion for Post-Stroke Hand Rehabilitation Therapy}, volume={43}, ISSN={0090-6964 1573-9686}, url={http://dx.doi.org/10.1007/S10439-014-1218-Y}, DOI={10.1007/S10439-014-1218-Y}, abstractNote={Stroke is the leading cause of serious, long-term disability in the United States. Impairment of upper extremity function is a common outcome following stroke, often to the detriment of lifestyle and employment opportunities. While the upper extremity is a natural target for therapy, treatment may be hampered by limitations in baseline capability as lack of success may discourage arm and hand use. We developeda virtual reality (VR) system in order to encourage repetitive task practice. This system combined an assistive glove with a novel VR environment. A set of exercises for this system was developed to encourage specific movements. Six stroke survivors with chronic upper extremity hemiparesis volunteered to participate in a pilot study in which they completed 18 one-hour training sessions with the VR system. Performance with the system was recorded across the 18 training sessions. Clinical evaluations of motor control were conducted at three time points: prior to initiation of training, following the end of training, and 1 month later. Subjects displayed significant improvement on performance of the virtual tasks over the course of the training, although for the clinical outcome measures only lateral pinch showed significant improvement. Future expansion to multi-user virtual environments may extend the benefits of this system for stroke survivors with hemiparesis by furthering engagement in the rehabilitation exercises.}, number={2}, journal={Annals of Biomedical Engineering}, publisher={Springer Science and Business Media LLC}, author={Tsoupikova, Daria and Stoykov, Nikolay S. and Corrigan, Molly and Thielbar, Kelly and Vick, Randy and Li, Yu and Triandafilou, Kristen and Preuss, Fabian and Kamper, Derek}, year={2015}, month={Jan}, pages={467–477} }
 @article{triandafilou_kamper_2014, title={Carryover Effects of Cyclical Stretching of the Digits on Hand Function in Stroke Survivors}, volume={95}, ISSN={0003-9993}, url={http://dx.doi.org/10.1016/J.APMR.2014.04.008}, DOI={10.1016/J.APMR.2014.04.008}, abstractNote={Objective To investigate the longevity and cumulative impact of multiple sessions of passive, cyclical stretching of the digits on hand function in subacute stroke survivors. Design Before-after trial with intervention repeated on 3 consecutive days. Setting Research laboratory. Participants Individuals (N=27) with moderate to severe hand impairment, 2 to 6 months (subacute, n=12) and >7 months (chronic, n=15) poststroke. Interventions Subjects wore an actuated glove orthosis that cyclically moved their fingers and thumb from a relaxed/flexed posture into neutral extension for 30 minutes on 3 consecutive days. Main Outcome Measures Three hand-specific tasks from the Graded Wolf Motor Function Test, Box and Block Test (BBT), grip strength, and lateral pinch strength. Recordings were taken before stretching and at 3 time points, each separated by 30 minutes after completion of stretching on each day. Results Significant improvement was observed immediately after the stretching for both groups. Improvements in the subacute group were largely maintained up to 1 hour poststretching, with significant carryover from day to day for some outcomes measures such as the BBT (P=.006) and grip strength (P=.012). In contrast, improvements after stretching for the chronic group were transient, with the changes largely dissipating over time and no significant cumulative effect across days. Conclusions Cyclical stretching of the digits had a lasting and reinforcing effect on improving hand motor control for subacute stroke survivors. Incorporation of cyclical stretching before active hand therapy may prove to be a beneficial treatment for stroke survivors, especially during the subacute phase of recovery.}, number={8}, journal={Archives of Physical Medicine and Rehabilitation}, publisher={Elsevier BV}, author={Triandafilou, Kristen M. and Kamper, Derek G.}, year={2014}, month={Aug}, pages={1571–1576} }
 @article{qian_traylor_lee_ellis_weiss_kamper_2014, title={Mechanical properties vary for different regions of the finger extensor apparatus}, volume={47}, ISSN={0021-9290}, url={http://dx.doi.org/10.1016/J.JBIOMECH.2014.06.035}, DOI={10.1016/J.JBIOMECH.2014.06.035}, abstractNote={The extensor apparatus, an aponeurosis that covers the dorsal side of each finger, transmits force from a number of musculotendons to the phalanges. Multiple tendons integrate directly into the structure at different sites and the extensor apparatus attaches to the phalanges at multiple points. Thus, prediction of the force distribution within the extensor apparatus, or hood, and the transmission to the phalanges is challenging, especially as knowledge of the underlying mechanical properties of the tissue is limited. We undertook quantification of some of these properties through material testing of cadaver specimens. We punched samples at specified locations from 19 extensor hood specimens. Material testing was performed to failure for each sample with a custom material testing device. Testing revealed significant differences in ultimate load, ultimate strain, thickness, and tangent modulus along the length of the extensor hood. Specifically, thickness, ultimate load, and ultimate strain were greater in the more proximal sections of the extensor hood, while the tangent modulus was greater in the more distal sections. The variations in mechanical properties within the hood may impact prediction of force transmission and, thus, should be considered when modeling the action of the extensor apparatus. Across the extensor hood, tangent modulus values were substantially smaller than values reported for other soft tissues, such as the Achilles tendon and knee ligaments, while ultimate strains were much greater. Thus, the tissue in the extensor apparatus seems to have greater elasticity, which should be modeled accordingly.}, number={12}, journal={Journal of Biomechanics}, publisher={Elsevier BV}, author={Qian, Kai and Traylor, Kay and Lee, Sang Wook and Ellis, Benjamin and Weiss, Jeffrey and Kamper, Derek}, year={2014}, month={Sep}, pages={3094–3099} }
 @article{triandafilou_kamper_2012, title={Investigation of hand muscle atrophy in stroke survivors}, volume={27}, ISSN={0268-0033}, url={http://dx.doi.org/10.1016/j.clinbiomech.2011.10.002}, DOI={10.1016/j.clinbiomech.2011.10.002}, abstractNote={Background Weakness is often profound in the contralesional hand after stroke. Relative contributions of various neural and mechanical mechanisms to this impairment, however, have not been quantified. In this study, the extent of one potential contributor, muscle atrophy, was noninvasively assessed in index finger musculature using ultrasonographic techniques. Methods Twenty-five stroke survivors (45–65 years old) with severe hand impairment resulting from a stroke occurring 2–4 years prior participated, along with 10 age-matched control subjects. Muscle cross sectional area and thickness were geometrically measured from ultrasound images on both limbs of participants. Findings Muscle size on the paretic limb of stroke survivors was smaller for all 7 hand muscles investigated. An average difference of 15% (SD 4) was seen for muscle cross sectional area and 11% (SD 2) for muscle thickness, while the difference between the dominant and non-dominant limbs for control subjects (6% (SD 2) and 1% (SD 4) for the muscle cross sectional area and muscle thickness, respectively) was not significant. Interpretation Although muscle atrophy was detected in the paretic limb following stroke, it is not explanatory of the marked impairment in strength seen in this stroke population. However, other alterations in muscle morphology, such as fatty infiltrations and changes in fiber structure, may contribute to the emergent muscle weakness post-stroke.}, number={3}, journal={Clinical Biomechanics}, publisher={Elsevier BV}, author={Triandafilou, Kristen M. and Kamper, Derek G.}, year={2012}, month={Mar}, pages={268–272} }
 @article{conrad_kamper_2012, title={Isokinetic strength and power deficits in the hand following stroke}, volume={123}, ISSN={1388-2457}, url={http://dx.doi.org/10.1016/j.clinph.2011.10.004}, DOI={10.1016/j.clinph.2011.10.004}, abstractNote={The purpose of this study was to compare the torque production in the paretic and non-paretic hands during isokinetic tasks following stroke.We compared torque and power production at the MCP joint of chronic stroke survivors during isometric and isokinetic tasks. We also recorded surface electromyography (EMG) activity in the forearm muscles.Isokinetic torque production at all velocities was less than that produced during isometric trials. Both torque and power produced by the paretic hand was substantially impaired. Deficits were substantially greater in extension than flexion trials. EMG data suggests that excessive co-contraction of agonist and antagonist muscles does not greatly affect isokinetic torque production at the MCP joint.The fact that movement velocity produces larger deficits in torque and power production may explain why patients who have limited strength impairments still experience functional deficits.This study demonstrates that strength testing of stroke survivors under isometric conditions may underestimate the overall level of impairment.}, number={6}, journal={Clinical Neurophysiology}, publisher={Elsevier BV}, author={Conrad, Megan O. and Kamper, Derek G.}, year={2012}, month={Jun}, pages={1200–1206} }
 @article{seo_fischer_bogey_rymer_kamper_2011, title={Effect of a serotonin antagonist on delay in grip muscle relaxation for persons with chronic hemiparetic stroke}, volume={122}, ISSN={1388-2457}, url={http://dx.doi.org/10.1016/j.clinph.2010.10.035}, DOI={10.1016/j.clinph.2010.10.035}, abstractNote={To investigate if, following stroke, sustained involuntary activity after voluntary contraction (e.g., grip) of the long finger flexor muscles of the paretic hand is attributable to augmented serotonin release from brainstem pathways, affecting excitability of spastic motoneurons.This single-dose placebo-controlled study examined whether a serotonin receptor (5-HT2) antagonist, cyproheptadine hydrochloride, could reduce delay in muscle relaxation of a key paretic long finger flexor muscle immediately after grip for persons with stroke. Time to initiate the long finger flexor muscle contraction, grip and pinch strengths, and clinical hand function scores (the Action Research Arm Test and the Box and Block Test) were also assessed.Cyproheptadine hydrochloride reduced mean delays in finger relaxation (n=13; from 7.2 to 4.1 s; SEM=1.2 s; p=.026) in comparison to placebo, while leaving grip and pinch strengths and time to initiate the muscle contraction largely unaffected. Reduction in the relaxation time alone did not lead to increased clinical hand function scores.The findings support the supposition that monoaminergic brainstem pathways may be disinhibited following stroke, thereby resulting in increased delays in muscle relaxation.Treatments to reduce delay in muscle relaxation may facilitate hand rehabilitation in persons with stroke.}, number={4}, journal={Clinical Neurophysiology}, publisher={Elsevier BV}, author={Seo, Na Jin and Fischer, Heidi W. and Bogey, Ross A. and Rymer, William Z. and Kamper, Derek G.}, year={2011}, month={Apr}, pages={796–802} }
 @article{seo_fischer_bogey_rymer_kamper_2011, title={Use of Visual Force Feedback to Improve Digit Force Direction During Pinch Grip in Persons With Stroke: A Pilot Study}, volume={92}, ISSN={0003-9993}, url={http://dx.doi.org/10.1016/j.apmr.2010.08.016}, DOI={10.1016/j.apmr.2010.08.016}, abstractNote={To investigate whether visual feedback of digit force directions for the index fingertip and thumb tip during repeated practice of grip force production can correct the digit force directions for persons with stroke during grip assessments. Following stroke, the paretic fingers generate digit forces with a higher than normal proportion of shear force to compression force during grip. This misdirected digit force may lead to finger-object slip and failure to stably grasp an object.A case series.Laboratory.Persons (N=11) with severe chronic hand impairment after stroke.Four training sessions during which participants practiced directing the index finger and thumb forces in various target directions during pinch using visual feedback.Digit force direction during pinch and clinical hand function scores were measured before and immediately after the training.Study participants were able to redirect the digit force closer to the direction perpendicular to the object surface and increase their hand function scores after training. The mean ratio of the shear force to the normal force decreased from 58% to 41% (SD, 17%), the mean Box and Block Test score increased from 1.4 to 3.4 (SD, 2.0), and the mean Action Research Arm Test score increased from 10.8 to 12.1 (SD, 1.3) (P<.05 for all 3 measures).Repeated practice of pinch with visual feedback of force direction improved grip force control in persons with stroke. Visual feedback of pinch forces may prove valuable as a rehabilitation paradigm for improving hand function.}, number={1}, journal={Archives of Physical Medicine and Rehabilitation}, publisher={Elsevier BV}, author={Seo, Na Jin and Fischer, Heidi W. and Bogey, Ross A. and Rymer, William Z. and Kamper, Derek G.}, year={2011}, month={Jan}, pages={24–30} }
 @article{seo_rymer_kamper_2010, title={Altered digit force direction during pinch grip following stroke}, volume={202}, ISSN={0014-4819 1432-1106}, url={http://dx.doi.org/10.1007/s00221-010-2193-7}, DOI={10.1007/s00221-010-2193-7}, abstractNote={This study examined grip force development in individuals with hemiparesis following unilateral stroke. Eleven patients with chronic stroke with severe hand impairment and five age-matched neurologically intact subjects grasped an instrumented object between the index finger and thumb while fingertip forces, digit posture, and muscle electromyographic activity were recorded. We tested a range of different grip conditions with varying grip sizes, object stability, and grip force level. We found that fingertip force direction in the paretic digits deviated from the direction normal to the grip surface by more than twice as much as for asymptomatic digits. Additionally, the paretic thumb had, on average, 18% greater deviation of grip force direction than the paretic index finger. This large deviation of finger force direction for the paretic digits was consistently observed regardless of grip size, grip force level, and object stability. Due to the large deviation of the force direction from the normal direction, the paretic digits slipped and moved more than 1 cm during 55% of all grasping trials. A regression analysis suggests that this altered grip force direction was associated with altered hand muscle activation patterns, but not with the posture at which the digit made contact with the object. Therapies to redirect the force direction at the digits may improve stroke survivors' ability to stably grip an object.}, number={4}, journal={Experimental Brain Research}, publisher={Springer Science and Business Media LLC}, author={Seo, Na Jin and Rymer, William Z. and Kamper, Derek G.}, year={2010}, month={Feb}, pages={891–901} }
 @article{cruz_kamper_2010, title={Use of a Novel Robotic Interface to Study Finger Motor Control}, volume={38}, ISSN={0090-6964 1573-9686}, url={http://dx.doi.org/10.1007/s10439-009-9845-4}, DOI={10.1007/s10439-009-9845-4}, abstractNote={Stroke is the leading cause of permanent adult disability in the U.S., frequently resulting in chronic motor impairments. Rehabilitation of the upper limb, particularly the hand, is especially important as arm and hand deficits post-stroke limit the performance of activities of daily living and, subsequently, functional independence. Hand rehabilitation is challenging due to the complexity of motor control of the hand. New instrumentation is needed to facilitate examination of the hand. Thus, a novel actuated exoskeleton for the index finger, the FingerBot, was developed to permit the study of finger kinetics and kinematics under a variety of conditions. Two such novel environments, one applying a spring-like extension torque proportional to angular displacement at each finger joint and another applying a constant extension torque at each joint, were compared in 10 stroke survivors with the FingerBot. Subjects attempted to reach targets located throughout the finger workspace. The constant extension torque assistance resulted in a greater workspace area (p < 0.02) and a larger active range of motion for the metacarpophalangeal joint (p < 0.01) than the spring-like assistance. Additionally, accuracy in terms of reaching the target was greater with the constant extension assistance as compared to no assistance. The FingerBot can be a valuable tool in assessing various hand rehabilitation paradigms following stroke.}, number={2}, journal={Annals of Biomedical Engineering}, publisher={Springer Science and Business Media LLC}, author={Cruz, E. G. and Kamper, D. G.}, year={2010}, month={Feb}, pages={259–268} }
 @article{iwamuro_cruz_connelly_fischer_kamper_2008, title={Effect of a Gravity-Compensating Orthosis on Reaching After Stroke: Evaluation of the Therapy Assistant WREX}, volume={89}, ISSN={0003-9993}, url={http://dx.doi.org/10.1016/j.apmr.2008.04.022}, DOI={10.1016/j.apmr.2008.04.022}, abstractNote={Within-subjects repeated-measures design evaluating reaching with and without the Therapy Assistant Wilmington Robotic Exoskeleton (WREX).Laboratory.Stroke survivors (N=10) with chronic upper-extremity hemiparesis.Not applicable.Arm movement kinematics (Optotrak Certus motion detection system), muscle activity for biceps, triceps, anterior deltoid, and brachioradialis muscles (bipolar surface electromyography).Significant improvements of reaching distance occurred for all subjects across all targets (P<.001) when using the Therapy Assistant WREX. While the self-selected peak speed of hand movement during the reach decreased significantly with the Therapy Assistant WREX (P<.001), use of the Therapy Assistant WREX led to improved quality of movement as signified by a decrease in jerk (P<.001) and a shift in the timing of the peak speed to an earlier point in the movement (P<.001). Electromyographic muscle activity analysis showed that use of the Therapy Assistant WREX led to a reduction in biceps activity across all targets during the reach (P<.05), in conjunction with a marginally significant reduction in activity of the anterior deltoid (P<.055). No changes were observed in triceps (P=.47) or brachioradialis activity (P=.28).By reducing requirements for shoulder activation, the Therapy Assistant WREX improved reaching performance among stroke survivors compared with free reaching, thereby potentially facilitating practice of functional tasks.}, number={11}, journal={Archives of Physical Medicine and Rehabilitation}, publisher={Elsevier BV}, author={Iwamuro, Bridget T. and Cruz, Erik G. and Connelly, Lauri L. and Fischer, Heidi C. and Kamper, Derek G.}, year={2008}, month={Nov}, pages={2121–2128} }
 @article{lee_chen_towles_kamper_2008, title={Estimation of the effective static moment arms of the tendons in the index finger extensor mechanism}, volume={41}, ISSN={0021-9290}, url={http://dx.doi.org/10.1016/j.jbiomech.2008.02.008}, DOI={10.1016/j.jbiomech.2008.02.008}, abstractNote={A novel technique to estimate the contribution of finger extensor tendons to joint moment generation was proposed. Effective static moment arms (ESMAs), which represent the net effects of the tendon force on joint moments in static finger postures, were estimated for the 4 degrees of freedom (DOFs) in the index finger. Specifically, the ESMAs for the five tendons contributing to the finger extensor apparatus were estimated by directly correlating the applied tendon force to the measured resultant joint moments in cadaveric hand specimens. Repeated measures analysis of variance revealed that the finger posture, specifically interphalangeal joint angles, had significant effects on the measured ESMA values in 7 out of 20 conditions (four DOFs for each of the five muscles). Extensor digitorum communis and extensor indicis proprius tendons were found to have greater MCP ESMA values when IP joints are flexed, whereas abduction ESMAs of all muscles except extensor digitorum profundus were mainly affected by MCP flexion. The ESMAs were generally smaller than the moment arms estimated in previous studies that employed kinematic measurement techniques. Tendon force distribution within the extensor hood and dissipation into adjacent structures are believed to contribute to the joint moment reductions, which result in smaller ESMA values.}, number={7}, journal={Journal of Biomechanics}, publisher={Elsevier BV}, author={Lee, Sang Wook and Chen, Hua and Towles, Joseph D. and Kamper, Derek G.}, year={2008}, month={Jan}, pages={1567–1573} }
 @article{simone_sundarrajan_luo_jia_kamper_2007, title={A low cost instrumented glove for extended monitoring and functional hand assessment}, volume={160}, ISSN={0165-0270}, url={http://dx.doi.org/10.1016/j.jneumeth.2006.09.021}, DOI={10.1016/j.jneumeth.2006.09.021}, abstractNote={A wearable finger flexion monitor developed to measure hand function in individuals with hand dysfunction was evaluated for feasibility, measurement repeatability and reliability, fidelity of wireless transmission, and user acceptance. Configuration of the monitor allows use in situations when a traditional measurement glove cannot be worn. Five healthy individuals participated in the study of repeatability, while 10 healthy individuals and 10 individuals with acquired brain injury participated in trials to assess feasibility and user comfort. Repeatability results showed an overall error of 3.4 degrees , compared to 5.5 degrees and 5.7 degrees reported with other sensor gloves, and to manual measurements (5-8 degrees). Intraclass coefficient of reliability (using coefficient alpha) averaged 0.95. User feedback regarding comfort of the monitor was very high. Loss of data during wireless transmission was no greater than 1.2%. Results demonstrate that the monitor has a strong potential to be used as a tool for objective hand function evaluation in the home and community for both short- and long-term monitoring.}, number={2}, journal={Journal of Neuroscience Methods}, publisher={Elsevier BV}, author={Simone, Lisa K. and Sundarrajan, Nappinnai and Luo, Xun and Jia, Yicheng and Kamper, Derek G.}, year={2007}, month={Mar}, pages={335–348} }
 @article{li_kamper_rymer_2006, title={Effects of changing wrist positions on finger flexor hypertonia in stroke survivors}, volume={33}, ISSN={0148-639X 1097-4598}, url={http://dx.doi.org/10.1002/mus.20453}, DOI={10.1002/mus.20453}, abstractNote={We sought to establish whether spastic hypertonia results from changes in intrinsic muscle properties or from altered stretch reflex properties. We hypothesized that finger flexor spastic hypertonia is primarily of neural origin, and that the dynamics of spastic muscle responses to stretch should therefore reflect the dynamics of muscle spindle receptor responses. In 12 stroke survivors, we recorded torque and electromyographic (EMG) responses of extrinsic finger flexors to constant‐velocity rotation of the metacarpophalangeal (MCP) joints of the affected hand, over a range of initial muscle lengths. Stretch velocity was set to 6°, 50°, 150°, or 300° per second. Muscle length changes were imposed by changing wrist angle between 0°, 25°, and 50° of flexion. We found that reflex torque and EMG responses exhibited both velocity and length dependence, and there were significant interactions between velocity and length, replicating known characteristics of muscle spindle receptors. Our results support the hypothesis that finger flexor hypertonia is primarily of neural origin, and that it accurately reflects spindle receptor firing properties. Muscle Nerve 2006}, number={2}, journal={Muscle & Nerve}, publisher={Wiley}, author={Li, Sheng and Kamper, Derek G. and Rymer, William Zev}, year={2006}, month={Feb}, pages={183–190} }
 @article{kamper_fischer_cruz_2006, title={Impact of finger posture on mapping from muscle activation to joint torque}, volume={21}, ISSN={0268-0033}, url={http://dx.doi.org/10.1016/j.clinbiomech.2005.11.005}, DOI={10.1016/j.clinbiomech.2005.11.005}, abstractNote={<h2>Abstract</h2> <i>Background.</i> The mapping from muscle activation to joint torque production can be difficult to determine for the multi-articular muscles of the fingers. This relationship was examined in vivo as a function of posture in the index finger. <i>Methods.</i> Five healthy adults participated in an experiment in which the seven muscles of the index finger were sequentially electrically stimulated using intramuscular electrodes. Each muscle was stimulated at 12 different finger postures consisting of specified flexion of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints, while fingertip forces and moments were recorded. <i>Findings.</i> Repeated measures analysis of variance revealed that joint torques resulting from the stimulation were significantly dependent upon finger posture (<i>p</i><0.05). The magnitude of the change in joint torque across postures was generally greater than 60%. This value is much larger than the difference attributable to the increase in active muscle force that occurs at longer muscle length, in accordance with the force–length curve (10–20% for the estimated length changes). In addition, the relative distribution of the joint torques generated by a given muscle activation was dependent upon finger posture for the intrinsic muscles and the long finger flexors (<i>p</i><0.05); the ratio of one joint torque to another varied with posture for these muscles, in some cases by more than 50%. <i>Interpretation.</i> Joint torque is a product of both muscle force and the corresponding moment arm. As the change in active muscle force was limited, these data suggest that substantial changes in muscle moment arms occur with posture. Therefore, this postural dependence should be considered when constructing biomechanical models of the hand or planning tendon transfers for the fingers.}, number={4}, journal={Clinical Biomechanics}, publisher={Elsevier BV}, author={Kamper, Derek G. and Fischer, Heidi C. and Cruz, Erik G.}, year={2006}, month={May}, pages={361–369} }
 @article{cruz_kamper_2006, title={Kinematics of point-to-point finger movements}, volume={174}, ISSN={0014-4819 1432-1106}, url={http://dx.doi.org/10.1007/s00221-006-0416-8}, DOI={10.1007/s00221-006-0416-8}, abstractNote={The goal of this study was to examine the characteristics of planar fingertip movements with respect to the hand. Ten subjects with no known neuromuscular impairments performed a series of point-to-point movements with their dominant index fingertips. Subjects were instructed to move between five pairs of targets within the workspace of the index finger in each direction, for a total of ten separate movement tasks. We hypothesized that the trajectories with respect to the hand of these movements would exhibit curved paths contrary to the findings of similar hand path studies. The ratio of the path taken to the straight-line distance between the two targets was dependent upon the movement task (P < 0.01), as was the mean residual between the actual and straight-line paths (P < 0.001). For selected pairs of targets, these values were significantly different for the two opposing movement directions between a given pair of targets. This directional dependence of the curvature of the chosen finger-only trajectory observed in the initial protocol is incompatible with motor planning based solely on kinematic constraints, instead mechanical properties of the finger are likely incorporated.}, number={1}, journal={Experimental Brain Research}, publisher={Springer Science and Business Media LLC}, author={Cruz, E. G. and Kamper, D. G.}, year={2006}, month={Mar}, pages={29–34} }
 @article{kamper_fischer_cruz_rymer_2006, title={Weakness Is the Primary Contributor to Finger Impairment in Chronic Stroke}, volume={87}, ISSN={0003-9993}, url={http://dx.doi.org/10.1016/j.apmr.2006.05.013}, DOI={10.1016/j.apmr.2006.05.013}, abstractNote={To assess the relative contributions of several neurologic and biomechanic impairment mechanisms to overall finger and hand impairment in chronic hemiparetic stroke survivors.Repeated-measures design.Clinical research laboratory.Thirty stroke survivors with chronic hemiparesis. Fifteen subjects had severe hand motor impairment and 15 had moderate impairment, as measured with the Chedoke-McMaster Stroke Assessment.Not applicable.The biomechanic factors stiffness and resting flexion torque, together with the neurologic factors spasticity, strength, and coactivation, were quantified by using a custom hand manipulator, a dynamometer, and electromyographic recordings. Both passive and active rotations of the metacarpophalangeal joints of the fingers were examined.Although subjects in the severely impaired group exhibited statistically greater passive stiffness and resting flexion torque than their moderately impaired counterparts (P<.05), the overall effect of these biomechanic changes appeared small in relation to the deficits attributable to neurologic changes such as spasticity and, especially, weakness. In fact, weakness in grip strength and isometric extension accounted for the greatest portion of the variance between the 2 groups (eta(2)=.40 and eta(2)=.23, respectively).Thus, deficits in hand motor control after stroke seem to derive mainly from weakness, which may be attributable to the loss of descending corticospinal pathway activation of motoneurons.}, number={9}, journal={Archives of Physical Medicine and Rehabilitation}, publisher={Elsevier BV}, author={Kamper, Derek G. and Fischer, Heidi C. and Cruz, Erik G. and Rymer, William Z.}, year={2006}, month={Sep}, pages={1262–1269} }
 @article{kamper_barin_parnianpour_hemami_weed_2000, title={Simulation of the Seated Postural Stability of Healthy and Spinal Cord-Injured Subjects Using Optimal Feedback Control Methods}, volume={3}, ISSN={1025-5842 1476-8259}, url={http://dx.doi.org/10.1080/10255840008915256}, DOI={10.1080/10255840008915256}, abstractNote={Abstract A two-dimensional, biomechanical computer model was developed, using the software package Working Model1M, to simulate the postural control of seated individuals. Both able-bodied and spinal cord-injured subjects were represenied. The model incorporated active control of the upper body through full-state feedback. Specifically, a linear quadratic regulator scheme was implemented in the model. Nonlincaritics were included in the torque computations to mimic physiological constraints and disabiliiy. Interactions between the subject and the wheelchair were also included in the model. Simulation results were compared with those obtained from experiments in which the subjects had attempted to remain stable during the application of significant disturbance moments, similar to lhose experienced during braking in a vehicle. While subjects exhibited more complex control schemes, the model was able to simulate overall stability. Therefore, it is believed that the model could prove beneficial to future research examining the effects of various restraints on stability.}, number={2}, journal={Computer Methods in Biomechanics and Biomedical Engineering}, publisher={Informa UK Limited}, author={Kamper, D. and Barin, K. and Parnianpour, M. and Hemami, H. and Weed, H.}, year={2000}, month={Jan}, pages={79–93} }