2024
Bashatah, Ahmed; Mukherjee, Biswarup; Rima, Afsana; Patwardhan, Shriniwas; Otto, Paul; Sutherland, Robert; King, Erica L.; Lancaster, Brandon; Aher, Abhishek; Gibson, Gabriel; Marzi, Laura De; Taghizadeh, Zahra; Acuña, Samuel; Chitnis, Parag V.; Sikdar, Siddhartha
Wearable Ultrasound System Using Low-Voltage Time Delay Spectrometry for Dynamic Tissue Imaging Journal Article
In: IEEE Transactions on Biomedical Engineering, vol. 71, no. 11, pp. 3232–3243, 2024, ISSN: 1558-2531.
@article{bashatah2024wearable,
title = {Wearable Ultrasound System Using Low-Voltage Time Delay Spectrometry for Dynamic Tissue Imaging},
author = {Ahmed Bashatah and Biswarup Mukherjee and Afsana Rima and Shriniwas Patwardhan and Paul Otto and Robert Sutherland and Erica L. King and Brandon Lancaster and Abhishek Aher and Gabriel Gibson and Laura De Marzi and Zahra Taghizadeh and Samuel Acuña and Parag V. Chitnis and Siddhartha Sikdar},
doi = {10.1109/TBME.2024.3414419},
issn = {1558-2531},
year = {2024},
date = {2024-11-01},
urldate = {2024-10-28},
journal = {IEEE Transactions on Biomedical Engineering},
volume = {71},
number = {11},
pages = {3232–3243},
abstract = {Objective: Wearable ultrasound is emerging as a new paradigm of real-time imaging in freely moving humans and has wide applications from cardiovascular health monitoring to human gesture recognition. However, current wearable ultrasound devices have typically employed pulse-echo imaging which requires high excitation voltages and sampling rates, posing safety risks, and requiring specialized hardware. Our objective was to develop and evaluate a wearable ultrasound system based on time delay spectrometry (TDS) that utilizes low-voltage excitation and significantly simplified instrumentation. Methods: We developed a TDS-based ultrasound system that utilizes continuous, frequency-modulated sweeps at low excitation voltages. By mixing the transmit and receive signals, the system digitizes the ultrasound signal at audio frequency (kHz) sampling rates. Wearable ultrasound transducers were developed, and the system was characterized in terms of imaging performance, acoustic output, thermal characteristics, and applications in musculoskeletal imaging. Results: The prototype TDS system is capable of imaging up to 6 cm of depth with signal-to-noise ratio of up to 42 dB at a spatial resolution of 0.33 mm. Acoustic and thermal radiation measurements were within clinically safe limits for continuous ultrasound imaging. We demonstrated the ability to use a 4-channel wearable system for dynamic imaging of muscle activity. Conclusion: We developed a wearable ultrasound imaging system using TDS to mitigate challenges with pulse echo-based wearable ultrasound imaging systems. Our device is capable of high-resolution, dynamic imaging of deep-seated tissue structures and is safe for long-term use. Significance: This work paves the way for low-voltage wearable ultrasound imaging devices with significantly reduced hardware complexity.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Objective: Wearable ultrasound is emerging as a new paradigm of real-time imaging in freely moving humans and has wide applications from cardiovascular health monitoring to human gesture recognition. However, current wearable ultrasound devices have typically employed pulse-echo imaging which requires high excitation voltages and sampling rates, posing safety risks, and requiring specialized hardware. Our objective was to develop and evaluate a wearable ultrasound system based on time delay spectrometry (TDS) that utilizes low-voltage excitation and significantly simplified instrumentation. Methods: We developed a TDS-based ultrasound system that utilizes continuous, frequency-modulated sweeps at low excitation voltages. By mixing the transmit and receive signals, the system digitizes the ultrasound signal at audio frequency (kHz) sampling rates. Wearable ultrasound transducers were developed, and the system was characterized in terms of imaging performance, acoustic output, thermal characteristics, and applications in musculoskeletal imaging. Results: The prototype TDS system is capable of imaging up to 6 cm of depth with signal-to-noise ratio of up to 42 dB at a spatial resolution of 0.33 mm. Acoustic and thermal radiation measurements were within clinically safe limits for continuous ultrasound imaging. We demonstrated the ability to use a 4-channel wearable system for dynamic imaging of muscle activity. Conclusion: We developed a wearable ultrasound imaging system using TDS to mitigate challenges with pulse echo-based wearable ultrasound imaging systems. Our device is capable of high-resolution, dynamic imaging of deep-seated tissue structures and is safe for long-term use. Significance: This work paves the way for low-voltage wearable ultrasound imaging devices with significantly reduced hardware complexity.
Acuña, Samuel A.; Peixoto, Nathalia; Matto, Holly; Sikdar, Siddhartha
Addressing Societal Challenges through Graduate-level Community-engaged Design Projects (Traditional Research Paper) Proceedings Article
In: American Society for Engineering Education Annual Conference & Exposition, 2024.
@inproceedings{acuna2024addressing,
title = {Addressing Societal Challenges through Graduate-level Community-engaged Design Projects (Traditional Research Paper)},
author = {Samuel A. Acuña and Nathalia Peixoto and Holly Matto and Siddhartha Sikdar},
url = {https://peer.asee.org/46521},
year = {2024},
date = {2024-06-01},
urldate = {2024-06-01},
booktitle = {American Society for Engineering Education Annual Conference & Exposition},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Acuña, Samuel A.
A Practical Research Methods Course That Teaches How to Be a Successful Biomedical Engineering Graduate Student Journal Article
In: Biomedical Engineering Education, vol. 4, pp. 295-304, 2024, ISSN: 2730-5945.
@article{acuna2024practical,
title = {A Practical Research Methods Course That Teaches How to Be a Successful Biomedical Engineering Graduate Student},
author = {Samuel A. Acuña},
doi = {10.1007/s43683-024-00135-9},
issn = {2730-5945},
year = {2024},
date = {2024-06-01},
urldate = {2024-06-01},
journal = {Biomedical Engineering Education},
volume = {4},
pages = {295-304},
abstract = {Should your department offer a course on how to be a scientist and a successful graduate student? We offer this course at George Mason University as a mandatory part of the graduate curriculum, but this is not common practice for graduate biomedical engineering programs. Graduate education in biomedical engineering is evolving rapidly, with an increasing demand for fundamental research skills, interdisciplinary skills, and professional development. We believe that graduate students will be more successful in their research activities if they are explicitly taught these skills at the beginning of their graduate coursework. This paper describes the design of this course in our bioengineering department.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Should your department offer a course on how to be a scientist and a successful graduate student? We offer this course at George Mason University as a mandatory part of the graduate curriculum, but this is not common practice for graduate biomedical engineering programs. Graduate education in biomedical engineering is evolving rapidly, with an increasing demand for fundamental research skills, interdisciplinary skills, and professional development. We believe that graduate students will be more successful in their research activities if they are explicitly taught these skills at the beginning of their graduate coursework. This paper describes the design of this course in our bioengineering department.
2023
Engdahl, Susannah M.; Acuña, Samuel A.; Kaliki, Rahul R.; Sikdar, Siddhartha
Sonomyography for Control of Upper-Limb Prostheses: Current State and Future Directions Journal Article
In: Journal of Prosthetics and Orthotics, pp. 10.1097/JPO.0000000000000482, 2023, ISSN: 1040-8800.
@article{engdahl2023sonomyography,
title = {Sonomyography for Control of Upper-Limb Prostheses: Current State and Future Directions},
author = {Susannah M. Engdahl and Samuel A. Acuña and Rahul R. Kaliki and Siddhartha Sikdar},
doi = {10.1097/JPO.0000000000000482},
issn = {1040-8800},
year = {2023},
date = {2023-08-01},
urldate = {2023-08-18},
journal = {Journal of Prosthetics and Orthotics},
pages = {10.1097/JPO.0000000000000482},
abstract = {Problem Statement~ Despite the recent advancements in technology, many individuals with upper-limb loss struggle to achieve stable control over multiple degrees of freedom in a prosthesis. There is an ongoing need to develop noninvasive prosthesis control modalities that could improve functional patient outcomes. Proposed Solution~ Ultrasound-based sensing of muscle deformation, known as sonomyography, is an emerging sensing modality for upper-limb prosthesis control with the potential to significantly improve functionality. Sonomyography enables spatiotemporal characterization of both superficial and deep muscle activity, making it possible to distinguish the contributions of individual muscles during functional movements and derive a large set of independent prosthesis control signals. Using sonomyography to control a prosthesis has shown great promise in the research literature but has not yet been fully adapted for clinical use. This article describes the implementation of sonomyography for upper-limb prosthesis control, ongoing technological development, considerations for deploying this technology in clinical settings, and recommendations for future study. Clinical Relevance~ Sonomyography may soon become a clinically viable modality for upper-limb prosthesis control that could offer prosthetists an additional solution when selecting optimal treatment plans for their patients.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Problem Statement~ Despite the recent advancements in technology, many individuals with upper-limb loss struggle to achieve stable control over multiple degrees of freedom in a prosthesis. There is an ongoing need to develop noninvasive prosthesis control modalities that could improve functional patient outcomes. Proposed Solution~ Ultrasound-based sensing of muscle deformation, known as sonomyography, is an emerging sensing modality for upper-limb prosthesis control with the potential to significantly improve functionality. Sonomyography enables spatiotemporal characterization of both superficial and deep muscle activity, making it possible to distinguish the contributions of individual muscles during functional movements and derive a large set of independent prosthesis control signals. Using sonomyography to control a prosthesis has shown great promise in the research literature but has not yet been fully adapted for clinical use. This article describes the implementation of sonomyography for upper-limb prosthesis control, ongoing technological development, considerations for deploying this technology in clinical settings, and recommendations for future study. Clinical Relevance~ Sonomyography may soon become a clinically viable modality for upper-limb prosthesis control that could offer prosthetists an additional solution when selecting optimal treatment plans for their patients.
2022
Schroeder, Megan J.; Acuña, Samuel A.; Krishnan, Chandramouli; Dhaher, Yasin Y.
Can Increased Locomotor Task Difficulty Differentiate Knee Muscle Forces After Anterior Cruciate Ligament Reconstruction? Journal Article
In: Journal of Applied Biomechanics, vol. 38, no. 2, pp. 84–94, 2022.
@article{schroeder2022can,
title = {Can Increased Locomotor Task Difficulty Differentiate Knee Muscle Forces After Anterior Cruciate Ligament Reconstruction?},
author = {Megan J. Schroeder and Samuel A. Acuña and Chandramouli Krishnan and Yasin Y. Dhaher},
doi = {10.1123/jab.2021-0215},
year = {2022},
date = {2022-04-01},
journal = {Journal of Applied Biomechanics},
volume = {38},
number = {2},
pages = {84–94},
publisher = {Human Kinetics},
address = {Champaign IL, USA},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Acuña, Samuel A.; Tyler, Mitchell E.; Thelen, Darryl G.
Individuals with Chronic Mild-to-Moderate Traumatic Brain Injury Exhibit Decreased Neuromuscular Complexity During Gait Journal Article
In: Neurorehabilitation and Neural Repair, vol. 36, no. 4-5, pp. 317–327, 2022, ISSN: 1545-9683.
@article{acuna2022individuals,
title = {Individuals with Chronic Mild-to-Moderate Traumatic Brain Injury Exhibit Decreased Neuromuscular Complexity During Gait},
author = {Samuel A. Acuña and Mitchell E. Tyler and Darryl G. Thelen},
doi = {10.1177/15459683221081064},
issn = {1545-9683},
year = {2022},
date = {2022-04-01},
urldate = {2022-05-10},
journal = {Neurorehabilitation and Neural Repair},
volume = {36},
number = {4-5},
pages = {317–327},
publisher = {SAGE Publications Inc STM},
abstract = {BackgroundSynergy analysis provides a means of quantifying the complexity of neuromuscular control during gait. Prior studies have shown evidence of reduced neuromuscular complexity during gait in individuals with neurological disorders associated with stroke, cerebral palsy, and Parkinson?s disease.ObjectiveThe purpose of this study was to investigate neuromuscular complexity during gait in individuals who experienced a prior traumatic brain injury (TBI) that resulted in chronic balance deficits.MethodsWe measured and analyzed lower extremity electromyographic data during treadmill and overground walking for 44 individuals with residual balance deficits from a mild-to-moderate TBI at least 1~year prior. We also tested 20 unimpaired controls as a comparison. Muscle synergies were calculated for each limb using non-negative matrix factorization of the activation patterns for 6 leg muscles. We quantified neuromuscular complexity using Walk-DMC, a normalized metric of the total variance accounted for by a single synergy, in which a Walk-DMC score of 100 represents normal variance accounted for. We compared group average synergy structures and inter-limb similarity using cosine similarity. We also quantified each individual?s gait and balance using the Sensory Organization Test, the Dynamic Gait Index, and the Six-Minute Walk Test.ResultsNeuromuscular complexity was diminished for individuals with a prior TBI. Walk-DMC averaged 92.8 ± 12.3 for the TBI group during overground walking, which was significantly less than seen in controls (100.0 ± 10.0). Individuals with a prior TBI exhibited 13% slower overground walking speeds than controls and reduced performance on the Dynamic Gait Index (18.5 ± 4.7 out of 24). However, Walk-DMC measures were insufficient to stratify variations in assessments of gait and balance performance. Group average synergy structures were similar between groups, although there were considerable between-group differences in the inter-limb similarity of the synergy activation vectors.ConclusionsIndividuals with gait and balance deficits due to a prior TBI exhibit evidence of decreased neuromuscular complexity during gait. Our results suggest that individuals with TBI exhibit similar muscle synergy weightings as controls, but altered control of the temporal activation of these muscle weightings.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
BackgroundSynergy analysis provides a means of quantifying the complexity of neuromuscular control during gait. Prior studies have shown evidence of reduced neuromuscular complexity during gait in individuals with neurological disorders associated with stroke, cerebral palsy, and Parkinson?s disease.ObjectiveThe purpose of this study was to investigate neuromuscular complexity during gait in individuals who experienced a prior traumatic brain injury (TBI) that resulted in chronic balance deficits.MethodsWe measured and analyzed lower extremity electromyographic data during treadmill and overground walking for 44 individuals with residual balance deficits from a mild-to-moderate TBI at least 1~year prior. We also tested 20 unimpaired controls as a comparison. Muscle synergies were calculated for each limb using non-negative matrix factorization of the activation patterns for 6 leg muscles. We quantified neuromuscular complexity using Walk-DMC, a normalized metric of the total variance accounted for by a single synergy, in which a Walk-DMC score of 100 represents normal variance accounted for. We compared group average synergy structures and inter-limb similarity using cosine similarity. We also quantified each individual?s gait and balance using the Sensory Organization Test, the Dynamic Gait Index, and the Six-Minute Walk Test.ResultsNeuromuscular complexity was diminished for individuals with a prior TBI. Walk-DMC averaged 92.8 ± 12.3 for the TBI group during overground walking, which was significantly less than seen in controls (100.0 ± 10.0). Individuals with a prior TBI exhibited 13% slower overground walking speeds than controls and reduced performance on the Dynamic Gait Index (18.5 ± 4.7 out of 24). However, Walk-DMC measures were insufficient to stratify variations in assessments of gait and balance performance. Group average synergy structures were similar between groups, although there were considerable between-group differences in the inter-limb similarity of the synergy activation vectors.ConclusionsIndividuals with gait and balance deficits due to a prior TBI exhibit evidence of decreased neuromuscular complexity during gait. Our results suggest that individuals with TBI exhibit similar muscle synergy weightings as controls, but altered control of the temporal activation of these muscle weightings.
Engdahl, Susannah M.; Acuña, Samuel A.; King, Erica L.; Bashatah, Ahmed; Sikdar, Siddhartha
First Demonstration of Functional Task Performance Using a Sonomyographic Prosthesis: A Case Study Journal Article
In: Frontiers in Bioengineering and Biotechnology, vol. 10, pp. 876836, 2022, ISSN: 2296-4185.
@article{engdahl2022first,
title = {First Demonstration of Functional Task Performance Using a Sonomyographic Prosthesis: A Case Study},
author = {Susannah M. Engdahl and Samuel A. Acuña and Erica L. King and Ahmed Bashatah and Siddhartha Sikdar},
url = {https://www.frontiersin.org/journals/bioengineering-and-biotechnology/articles/10.3389/fbioe.2022.876836/full},
issn = {2296-4185},
year = {2022},
date = {2022-01-01},
urldate = {2022-01-01},
journal = {Frontiers in Bioengineering and Biotechnology},
volume = {10},
pages = {876836},
abstract = {Ultrasound-based sensing of muscle deformation, known as sonomyography, has shown promise for accurately classifying the intended hand grasps of individuals with upper limb loss in offline settings. Building upon this previous work, we present the first demonstration of real-time prosthetic hand control using sonomyography to perform functional tasks. An individual with congenital bilateral limb absence was fitted with sockets containing a low-profile ultrasound transducer placed over forearm muscle tissue in the residual limbs. A classifier was trained using linear discriminant analysis to recognize ultrasound images of muscle contractions for three discrete hand configurations (rest, tripod grasp, index finger point) under a variety of arm positions designed to cover the reachable workspace. A prosthetic hand mounted to the socket was then controlled using this classifier. Using this real-time sonomyographic control, the participant was able to complete three functional tasks that required selecting different hand grasps in order to grasp and move one-inch wooden blocks over a broad range of arm positions. Additionally, these tests were successfully repeated without retraining the classifier across 3~hours of prosthesis use and following simulated donning and doffing of the socket. This study supports the feasibility of using sonomyography to control upper limb prostheses in real-world applications.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Ultrasound-based sensing of muscle deformation, known as sonomyography, has shown promise for accurately classifying the intended hand grasps of individuals with upper limb loss in offline settings. Building upon this previous work, we present the first demonstration of real-time prosthetic hand control using sonomyography to perform functional tasks. An individual with congenital bilateral limb absence was fitted with sockets containing a low-profile ultrasound transducer placed over forearm muscle tissue in the residual limbs. A classifier was trained using linear discriminant analysis to recognize ultrasound images of muscle contractions for three discrete hand configurations (rest, tripod grasp, index finger point) under a variety of arm positions designed to cover the reachable workspace. A prosthetic hand mounted to the socket was then controlled using this classifier. Using this real-time sonomyographic control, the participant was able to complete three functional tasks that required selecting different hand grasps in order to grasp and move one-inch wooden blocks over a broad range of arm positions. Additionally, these tests were successfully repeated without retraining the classifier across 3~hours of prosthesis use and following simulated donning and doffing of the socket. This study supports the feasibility of using sonomyography to control upper limb prostheses in real-world applications.
Majdi, Joseph A.; Acuña, Samuel A.; Chitnis, Parag V.; Sikdar, Siddhartha
Toward a Wearable Monitor of Local Muscle Fatigue during Electrical Muscle Stimulation Using Tissue Doppler Imaging Journal Article
In: Wearable Technologies, vol. 3, pp. e16, 2022.
@article{majdi2022wearable,
title = {Toward a Wearable Monitor of Local Muscle Fatigue during Electrical Muscle Stimulation Using Tissue Doppler Imaging},
author = {Joseph A. Majdi and Samuel A. Acuña and Parag V. Chitnis and Siddhartha Sikdar},
doi = {10.1017/wtc.2022.10},
year = {2022},
date = {2022-01-01},
journal = {Wearable Technologies},
volume = {3},
pages = {e16},
publisher = {Cambridge University Press},
edition = {2022/07/20},
abstract = {Electrical muscle stimulation (EMS) is widely used in rehabilitation and athletic training to generate involuntary muscle contractions. However, EMS leads to rapid muscle fatigue, limiting the force a muscle can produce during prolonged use. Currently available methods to monitor localized muscle fatigue and recovery are generally not compatible with EMS. The purpose of this study was to examine whether Doppler ultrasound imaging can assess changes in stimulated muscle twitches that are related to muscle fatigue from electrical stimulation. We stimulated five isometric muscle twitches in the medial and lateral gastrocnemius of 13 healthy subjects before and after a fatiguing EMS protocol. Tissue Doppler imaging of the medial gastrocnemius recorded muscle tissue velocities during each twitch. Features of the average muscle tissue velocity waveforms changed immediately after the fatiguing stimulation protocol (peak velocity: -38%,~p~= .022;~time-to-zero velocity: +8%,~p~= .050). As the fatigued muscle recovered, the features of the average tissue velocity waveforms showed a return towards their baseline values similar to that of the normalized ankle torque. We also found that features of the average tissue velocity waveform could significantly predict the ankle twitch torque for each participant (R2~=~0.255–0.849,~p~< .001). Our results provide evidence that Doppler ultrasound imaging can detect changes in muscle tissue during isometric muscle twitch that are related to muscle fatigue, fatigue recovery, and the generated joint torque. Tissue Doppler imaging may be a feasible method to monitor localized muscle fatigue during EMS in a wearable device.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Electrical muscle stimulation (EMS) is widely used in rehabilitation and athletic training to generate involuntary muscle contractions. However, EMS leads to rapid muscle fatigue, limiting the force a muscle can produce during prolonged use. Currently available methods to monitor localized muscle fatigue and recovery are generally not compatible with EMS. The purpose of this study was to examine whether Doppler ultrasound imaging can assess changes in stimulated muscle twitches that are related to muscle fatigue from electrical stimulation. We stimulated five isometric muscle twitches in the medial and lateral gastrocnemius of 13 healthy subjects before and after a fatiguing EMS protocol. Tissue Doppler imaging of the medial gastrocnemius recorded muscle tissue velocities during each twitch. Features of the average muscle tissue velocity waveforms changed immediately after the fatiguing stimulation protocol (peak velocity: -38%,~p~= .022;~time-to-zero velocity: +8%,~p~= .050). As the fatigued muscle recovered, the features of the average tissue velocity waveforms showed a return towards their baseline values similar to that of the normalized ankle torque. We also found that features of the average tissue velocity waveform could significantly predict the ankle twitch torque for each participant (R2~=~0.255–0.849,~p~< .001). Our results provide evidence that Doppler ultrasound imaging can detect changes in muscle tissue during isometric muscle twitch that are related to muscle fatigue, fatigue recovery, and the generated joint torque. Tissue Doppler imaging may be a feasible method to monitor localized muscle fatigue during EMS in a wearable device.
2021
Acuña, Samuel A.; Bashatah, Ahmed; Chitnis, Parag V.; Sikdar, Siddhartha
Measuring Signal Quality in Low Power Wearable Ultrasound Imaging Proceedings
Acoustical Society of America, vol. 150, no. 4, 2021, ISSN: 0001-4966.
@proceedings{acuna2021measuring,
title = {Measuring Signal Quality in Low Power Wearable Ultrasound Imaging},
author = {Samuel A. Acuña and Ahmed Bashatah and Parag V. Chitnis and Siddhartha Sikdar},
doi = {10.1121/10.0007727},
issn = {0001-4966},
year = {2021},
date = {2021-10-01},
urldate = {2021-10-01},
journal = {The Journal of the Acoustical Society of America},
volume = {150},
number = {4},
pages = {A90-A90},
publisher = {Acoustical Society of America},
keywords = {},
pubstate = {published},
tppubtype = {proceedings}
}
2019
Acuña, Samuel A; Ebrahimi, Anahid; Pomeroy, Robin L; Martin, Jack A; Thelen, Darryl G
Achilles Tendon Shear Wave Speed Tracks the Dynamic Modulation of Standing Balance Journal Article
In: Physiological Reports, vol. 7, no. 23, pp. e14298, 2019, ISSN: 2051-817X.
@article{acuna2019achilles,
title = {Achilles Tendon Shear Wave Speed Tracks the Dynamic Modulation of Standing Balance},
author = {Samuel A Acuña and Anahid Ebrahimi and Robin L Pomeroy and Jack A Martin and Darryl G Thelen},
doi = {10.14814/phy2.14298},
issn = {2051-817X},
year = {2019},
date = {2019-12-01},
journal = {Physiological Reports},
volume = {7},
number = {23},
pages = {e14298},
publisher = {John Wiley & Sons, Ltd},
abstract = {Abstract Standing balance performance is often characterized by sway, as measured via fluctuations of the center of pressure (COP) under the feet. For example, COP metrics can effectively delineate changes in balance under altered sensory conditions. However, COP is a global metric of whole-body dynamics and thus does not necessarily lend insight into the underlying musculotendon control. We have previously shown that shear wave tensiometers can track wave speeds in tendon as a surrogate measure of the load transmitted by the muscle-tendon unit. The purpose of this study was to investigate whether shear wave metrics have sufficient sensitivity to track subtle variations in Achilles tendon loading that correspond with postural sway. Sixteen healthy young adults (26 ± 5 years) stood for 10 s with their eyes open and closed. We simultaneously recorded COP under the feet and shear wave speed in the right Achilles tendon. We found that Achilles tendon shear wave speed closely tracked (r $>$ 0.95) dynamic fluctuations of the COP in the anteroposterior direction. Achilles tendon wave speed fluctuations significantly increased during standing with eyes closed, mirroring increases in COP fluctuations. These results demonstrate that tendon wave speed can track the subtle variations in Achilles tendon loading that modulate COP in standing. Hence, shear wave tensiometry exhibits the sensitivity to investigate the muscular control of quiet standing, and may also be useful for investigating other fine motor and force steadiness tasks.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Abstract Standing balance performance is often characterized by sway, as measured via fluctuations of the center of pressure (COP) under the feet. For example, COP metrics can effectively delineate changes in balance under altered sensory conditions. However, COP is a global metric of whole-body dynamics and thus does not necessarily lend insight into the underlying musculotendon control. We have previously shown that shear wave tensiometers can track wave speeds in tendon as a surrogate measure of the load transmitted by the muscle-tendon unit. The purpose of this study was to investigate whether shear wave metrics have sufficient sensitivity to track subtle variations in Achilles tendon loading that correspond with postural sway. Sixteen healthy young adults (26 ± 5 years) stood for 10 s with their eyes open and closed. We simultaneously recorded COP under the feet and shear wave speed in the right Achilles tendon. We found that Achilles tendon shear wave speed closely tracked (r $>$ 0.95) dynamic fluctuations of the COP in the anteroposterior direction. Achilles tendon wave speed fluctuations significantly increased during standing with eyes closed, mirroring increases in COP fluctuations. These results demonstrate that tendon wave speed can track the subtle variations in Achilles tendon loading that modulate COP in standing. Hence, shear wave tensiometry exhibits the sensitivity to investigate the muscular control of quiet standing, and may also be useful for investigating other fine motor and force steadiness tasks.
Acuña, Samuel Alberto
Altered Neuromuscular Control of Gait Following Traumatic Brain Injury and Targeted Neuromodulation to Improve Motor Function PhD Thesis
The University of Wisconsin–Madison, 2019.
@phdthesis{acuna2019altered,
title = {Altered Neuromuscular Control of Gait Following Traumatic Brain Injury and Targeted Neuromodulation to Improve Motor Function},
author = {Samuel Alberto Acuña},
year = {2019},
date = {2019-01-01},
school = {The University of Wisconsin–Madison},
abstract = {Gait and balance disorders are common among individuals who have experienced a traumatic brain injury (TBI). Prior studies have shown that individuals with TBI tend to walk slower, take smaller steps, and have increased mediolateral sway. However, symptoms and severity vary considerably between subjects, making the neuropathology of gait difficult to characterize and to inform targeted interventions. Traditional rehabilitation protocols provide little improvement after the first few months post-injury, leaving many individuals with chronic balance impairments. Interventions that can accelerate neuroplasticity or enhance sensorimotor integration are desperately needed to improve motor function in individuals with a prior TBI. This dissertation examines changes in the neuromuscular control of gait as a result of a mild to moderate traumatic brain injury and explores targeted neurorehabilitation modalities that may improve motor function. The first two chapters characterize neuromuscular coordination in chronic TBI patients and examine relationships between these quantitative motor control metrics and clinical assessments of gait function. The third chapter tests the hypothesis that neuromuscular coordination of gait can be fundamentally altered by using noninvasive neuromodulation to enhance plasticity during gait and balance rehabilitation exercises. The fourth chapter documents an exploratory study of gait and balance using sub-sensory vibratory stimulation to enhance somatosensation when visual information is disrupted. This dissertation demonstrates the potential application of noninvasive neuromodulation to improve gait and balance for individuals with a prior TBI.},
keywords = {},
pubstate = {published},
tppubtype = {phdthesis}
}
Gait and balance disorders are common among individuals who have experienced a traumatic brain injury (TBI). Prior studies have shown that individuals with TBI tend to walk slower, take smaller steps, and have increased mediolateral sway. However, symptoms and severity vary considerably between subjects, making the neuropathology of gait difficult to characterize and to inform targeted interventions. Traditional rehabilitation protocols provide little improvement after the first few months post-injury, leaving many individuals with chronic balance impairments. Interventions that can accelerate neuroplasticity or enhance sensorimotor integration are desperately needed to improve motor function in individuals with a prior TBI. This dissertation examines changes in the neuromuscular control of gait as a result of a mild to moderate traumatic brain injury and explores targeted neurorehabilitation modalities that may improve motor function. The first two chapters characterize neuromuscular coordination in chronic TBI patients and examine relationships between these quantitative motor control metrics and clinical assessments of gait function. The third chapter tests the hypothesis that neuromuscular coordination of gait can be fundamentally altered by using noninvasive neuromodulation to enhance plasticity during gait and balance rehabilitation exercises. The fourth chapter documents an exploratory study of gait and balance using sub-sensory vibratory stimulation to enhance somatosensation when visual information is disrupted. This dissertation demonstrates the potential application of noninvasive neuromodulation to improve gait and balance for individuals with a prior TBI.
Acuña, Samuel A; Francis, Carrie A; Franz, Jason R; Thelen, Darryl G
The Effects of Cognitive Load and Optical Flow on Antagonist Leg Muscle Coactivation during Walking for Young and Older Adults Journal Article
In: Journal of Electromyography and Kinesiology, vol. 44, pp. 8–14, 2019, ISSN: 1050-6411.
@article{acuna2019effects,
title = {The Effects of Cognitive Load and Optical Flow on Antagonist Leg Muscle Coactivation during Walking for Young and Older Adults},
author = {Samuel A Acuña and Carrie A Francis and Jason R Franz and Darryl G Thelen},
doi = {10.1016/j.jelekin.2018.11.003},
issn = {1050-6411},
year = {2019},
date = {2019-01-01},
journal = {Journal of Electromyography and Kinesiology},
volume = {44},
pages = {8–14},
abstract = {The purpose of this study was to compare how healthy aging interacts with environments that challenge cognitive load and optical flow to affect antagonist leg muscle coactivation during walking. We measured leg muscle activity in sixteen older adults (70.4 ± 4.2 years) and twelve young adults (23.6 ± 3.9 years) walking on a treadmill at their preferred speed while watching a speed-matched virtual hallway. Cognitive load was challenged using a dual-task to interfere with available attentional resources. Optical flow was challenged using perturbations designed to create a perception of lateral imbalance. We found antagonist coactivation increased with aging, independent of condition. We also found that, compared to unperturbed walking, only in the presence of optical flow perturbations did the older adults increase their antagonist coactivation. Antagonist coactivation in the young adults was not affected by either condition. Our findings provide evidence that antagonist leg muscle coactivation in healthy older adults is more sensitive to walking environments that challenge optical flow than environments that challenge cognitive load. As increased antagonist coactivation may indicate compromised balance, these findings may be relevant in the design of living environments to reduce falls risk.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
The purpose of this study was to compare how healthy aging interacts with environments that challenge cognitive load and optical flow to affect antagonist leg muscle coactivation during walking. We measured leg muscle activity in sixteen older adults (70.4 ± 4.2 years) and twelve young adults (23.6 ± 3.9 years) walking on a treadmill at their preferred speed while watching a speed-matched virtual hallway. Cognitive load was challenged using a dual-task to interfere with available attentional resources. Optical flow was challenged using perturbations designed to create a perception of lateral imbalance. We found antagonist coactivation increased with aging, independent of condition. We also found that, compared to unperturbed walking, only in the presence of optical flow perturbations did the older adults increase their antagonist coactivation. Antagonist coactivation in the young adults was not affected by either condition. Our findings provide evidence that antagonist leg muscle coactivation in healthy older adults is more sensitive to walking environments that challenge optical flow than environments that challenge cognitive load. As increased antagonist coactivation may indicate compromised balance, these findings may be relevant in the design of living environments to reduce falls risk.
Acuña, Samuel A; Zunker, John D; Thelen, Darryl G
The Effects of Sub-Threshold Vibratory Noise on Visuomotor Entrainment during Human Walking and Standing in a Virtual Reality Environment Journal Article
In: Human Movement Science, vol. 66, pp. 587–599, 2019, ISSN: 0167-9457.
@article{acuna2019effectsa,
title = {The Effects of Sub-Threshold Vibratory Noise on Visuomotor Entrainment during Human Walking and Standing in a Virtual Reality Environment},
author = {Samuel A Acuña and John D Zunker and Darryl G Thelen},
doi = {10.1016/j.humov.2019.06.009},
issn = {0167-9457},
year = {2019},
date = {2019-01-01},
journal = {Human Movement Science},
volume = {66},
pages = {587–599},
abstract = {Humans will naturally synchronize their posture to the motion of a visual surround, but it is unclear if this visuomotor entrainment can be attenuated with an increased sensitivity to somatosensory information. Sub-threshold vibratory noise applied to the Achilles tendons has proven to enhance ankle proprioception through the phenomenon of stochastic resonance. Our purpose was to compare visuomotor entrainment during walking and standing, and to understand how this entrainment might be attenuated by applying sub-threshold vibratory noise over the Achilles tendons. We induced visuomotor entrainment during standing and treadmill walking for ten subjects (24.5 ± 2.9 years) using a speed-matched virtual hallway with continuous mediolateral perturbations at three different frequencies. Vibrotactile motors over the Achilles tendons provided noise (0–400 Hz) with an amplitude set to 90% of each participant's sensory threshold. Mediolateral sacrum, C7, and head motion was greatly amplified (4–8× on average) at the perturbation frequencies during walking, but was much less pronounced during standing. During walking, individuals with greater mediolateral head motion at the fastest perturbation frequency saw the greatest attenuation of that motion with applied noise. Similarly, during standing, individuals who exhibited greater postural sway (as measured by the center of pressure) also saw the greatest reductions in sway with sub-threshold noise applied in three of our summary metrics. Our results suggest that, at least for healthy young adults, sub-threshold vibratory noise over the Achilles tendons can slightly improve postural control during disruptive mediolateral visual perturbations, but the applied noise does not substantially attenuate visuomotor entrainment during walking or standing.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Humans will naturally synchronize their posture to the motion of a visual surround, but it is unclear if this visuomotor entrainment can be attenuated with an increased sensitivity to somatosensory information. Sub-threshold vibratory noise applied to the Achilles tendons has proven to enhance ankle proprioception through the phenomenon of stochastic resonance. Our purpose was to compare visuomotor entrainment during walking and standing, and to understand how this entrainment might be attenuated by applying sub-threshold vibratory noise over the Achilles tendons. We induced visuomotor entrainment during standing and treadmill walking for ten subjects (24.5 ± 2.9 years) using a speed-matched virtual hallway with continuous mediolateral perturbations at three different frequencies. Vibrotactile motors over the Achilles tendons provided noise (0–400 Hz) with an amplitude set to 90% of each participant's sensory threshold. Mediolateral sacrum, C7, and head motion was greatly amplified (4–8× on average) at the perturbation frequencies during walking, but was much less pronounced during standing. During walking, individuals with greater mediolateral head motion at the fastest perturbation frequency saw the greatest attenuation of that motion with applied noise. Similarly, during standing, individuals who exhibited greater postural sway (as measured by the center of pressure) also saw the greatest reductions in sway with sub-threshold noise applied in three of our summary metrics. Our results suggest that, at least for healthy young adults, sub-threshold vibratory noise over the Achilles tendons can slightly improve postural control during disruptive mediolateral visual perturbations, but the applied noise does not substantially attenuate visuomotor entrainment during walking or standing.
2018
Joseph E Michaelis Samuel A Acuña, Josh D Roth
Intervention designed to increase interest in engineering for low-interest, K-12 girls did so for boys and girls Proceedings Article
In: American Society for Engineering Educations Annual Conference & Exposition, 2018.
@inproceedings{nokey,
title = {Intervention designed to increase interest in engineering for low-interest, K-12 girls did so for boys and girls},
author = {Samuel A Acuña, Joseph E Michaelis, Josh D Roth, Joseph D Towles},
url = {https://peer.asee.org/intervention-designed-to-increase-interest-in-engineering-for-low-interest-k-12-girls-did-so-for-boys-and-girls},
doi = {10.18260/1-2–30713},
year = {2018},
date = {2018-06-23},
urldate = {2018-06-23},
booktitle = {American Society for Engineering Educations Annual Conference & Exposition},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
Acuña, Samuel A; Tyler, Mitchell E; Danilov, Yuri P; Thelen, Darryl G
Abnormal Muscle Activation Patterns Are Associated with Chronic Gait Deficits Following Traumatic Brain Injury Journal Article
In: Gait & Posture, vol. 62, pp. 510–517, 2018, ISSN: 0966-6362.
@article{acuna2018abnormal,
title = {Abnormal Muscle Activation Patterns Are Associated with Chronic Gait Deficits Following Traumatic Brain Injury},
author = {Samuel A Acuña and Mitchell E Tyler and Yuri P Danilov and Darryl G Thelen},
doi = {10.1016/j.gaitpost.2018.04.012},
issn = {0966-6362},
year = {2018},
date = {2018-01-01},
journal = {Gait & Posture},
volume = {62},
pages = {510–517},
abstract = {Background Gait and balance disorders are common among individuals who have experienced a mild to moderate traumatic brain injury (TBI). However, little is known about how the neuromuscular control of gait is altered following a TBI. Research question Investigate the relationship between lower limb muscle activation patterns and chronic gait deficits in individuals who previously experienced a mild to moderate TBI. Methods Lower extremity electromyographic (EMG) signals were collected bilaterally during treadmill and overground walking in 44 ambulatory individuals with a TBI $>$1 year prior and 20 unimpaired controls. Activation patterns of TBI muscles were cross-correlated with normative data from control subjects to assess temporal phasing of muscle recruitment. Clinical assessments of gait and balance were performed using dynamic posturography, the dynamic gait index, six-minute walk test, and preferred walking speed. Results TBI subjects exhibited abnormal activation patterns in the tibialis anterior, medial gastrocnemius, and rectus femoris muscles during both overground and treadmill walking. Activation patterns of the vastus lateralis and soleus muscles did not differ from normal. There was considerable heterogeneity in performance on clinical balance and gait assessments. Abnormal muscle activation patterns were significantly correlated with variations in the dynamic gait index among the TBI subjects. Significance Individuals who have experienced a prior TBI do exhibit characteristic changes in the temporal coordination of select lower extremity muscles, which may contribute to impairments during challenging walking tasks.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Background Gait and balance disorders are common among individuals who have experienced a mild to moderate traumatic brain injury (TBI). However, little is known about how the neuromuscular control of gait is altered following a TBI. Research question Investigate the relationship between lower limb muscle activation patterns and chronic gait deficits in individuals who previously experienced a mild to moderate TBI. Methods Lower extremity electromyographic (EMG) signals were collected bilaterally during treadmill and overground walking in 44 ambulatory individuals with a TBI $>$1 year prior and 20 unimpaired controls. Activation patterns of TBI muscles were cross-correlated with normative data from control subjects to assess temporal phasing of muscle recruitment. Clinical assessments of gait and balance were performed using dynamic posturography, the dynamic gait index, six-minute walk test, and preferred walking speed. Results TBI subjects exhibited abnormal activation patterns in the tibialis anterior, medial gastrocnemius, and rectus femoris muscles during both overground and treadmill walking. Activation patterns of the vastus lateralis and soleus muscles did not differ from normal. There was considerable heterogeneity in performance on clinical balance and gait assessments. Abnormal muscle activation patterns were significantly correlated with variations in the dynamic gait index among the TBI subjects. Significance Individuals who have experienced a prior TBI do exhibit characteristic changes in the temporal coordination of select lower extremity muscles, which may contribute to impairments during challenging walking tasks.
2017
Francis, Carrie A; Michaelis, Joseph E; Acuña, Samuel A; Towles, Joseph
Impact of Biomechanics-Based Activities on Situational and Individual Interest among K-12 Students Proceedings Article
In: 2017 ASEE Annual Conference & Exposition, Columbus, OH, 2017, ISSN: 21535965.
@inproceedings{francis2017impact,
title = {Impact of Biomechanics-Based Activities on Situational and Individual Interest among K-12 Students},
author = {Carrie A Francis and Joseph E Michaelis and Samuel A Acuña and Joseph Towles},
url = {https://peer.asee.org/impact-of-biomechanics-based-activities-on-situational-and-individual-interest-among-k-12-students},
issn = {21535965},
year = {2017},
date = {2017-01-01},
urldate = {2017-01-01},
booktitle = {2017 ASEE Annual Conference & Exposition},
address = {Columbus, OH},
keywords = {},
pubstate = {published},
tppubtype = {inproceedings}
}
2014
Acuña, Samuel A; Smith, D M; Robinson, J M; Hawks, J C; Starbuck, P; King, D L; Ridge, S T; Charles, S K
Instrumented Figure Skating Blade for Measuring On-Ice Skating Forces Journal Article
In: Measurement Science and Technology, vol. 25, no. 12, pp. 125901, 2014, ISSN: 0957-0233.
@article{acuna2014instrumented,
title = {Instrumented Figure Skating Blade for Measuring On-Ice Skating Forces},
author = {Samuel A Acuña and D M Smith and J M Robinson and J C Hawks and P Starbuck and D L King and S T Ridge and S K Charles},
doi = {10.1088/0957-0233/25/12/125901},
issn = {0957-0233},
year = {2014},
date = {2014-12-01},
journal = {Measurement Science and Technology},
volume = {25},
number = {12},
pages = {125901},
abstract = {Competitive figure skaters experience substantial, repeated impact loading during jumps and landings. Although these loads, which are thought to be as high as six times body weight, can lead to overuse injuries, it is not currently possible to measure these forces on-ice. Consequently, efforts to improve safety for skaters are significantly limited. Here we present the development of an instrumented figure skating blade for measuring forces on-ice. The measurement system consists of strain gauges attached to the blade, Wheatstone bridge circuit boards, and a data acquisition device. The system is capable of measuring forces in the vertical and horizontal directions (inferior–superior and anterior–posterior directions, respectively) in each stanchion with a sampling rate of at least 1000 Hz and a resolution of approximately one-tenth of body weight. The entire system weighs 142 g and fits in the space under the boot. Calibration between applied and measured force showed excellent agreement (R $>$ 0.99), and a preliminary validation against a force plate showed good predictive ability overall (R $geq$ 0.81 in vertical direction). The system overestimated the magnitude of the first and second impact peaks but detected their timing with high accuracy compared to the force plate.},
keywords = {},
pubstate = {published},
tppubtype = {article}
}
Competitive figure skaters experience substantial, repeated impact loading during jumps and landings. Although these loads, which are thought to be as high as six times body weight, can lead to overuse injuries, it is not currently possible to measure these forces on-ice. Consequently, efforts to improve safety for skaters are significantly limited. Here we present the development of an instrumented figure skating blade for measuring forces on-ice. The measurement system consists of strain gauges attached to the blade, Wheatstone bridge circuit boards, and a data acquisition device. The system is capable of measuring forces in the vertical and horizontal directions (inferior–superior and anterior–posterior directions, respectively) in each stanchion with a sampling rate of at least 1000 Hz and a resolution of approximately one-tenth of body weight. The entire system weighs 142 g and fits in the space under the boot. Calibration between applied and measured force showed excellent agreement (R $>$ 0.99), and a preliminary validation against a force plate showed good predictive ability overall (R $geq$ 0.81 in vertical direction). The system overestimated the magnitude of the first and second impact peaks but detected their timing with high accuracy compared to the force plate.