Works (39)

Updated: August 26th, 2023 21:18

2023 review

Age-related changes in gait biomechanics and their impact on the metabolic cost of walking: Report from a National Institute on Aging workshop

[Review of ]. EXPERIMENTAL GERONTOLOGY, 173.

author keywords: Mobility; Fatigue; Muscle energetics; Wearable technology; Tendon
MeSH headings : United States; Biomechanical Phenomena; National Institute on Aging (U.S.); Walking; Gait
TL;DR: How gait mechanics and energy cost change with aging, the potential neuromuscular mechanisms and role of connective tissue in these changes, and cutting-edge interventions and technologies that may be used to measure and improve gait and mobility in older adults are highlighted. (via Semantic Scholar)
Source: Web Of Science
Added: June 19, 2023

2023 journal article

The influence of induced gait asymmetry on joint reaction forces

JOURNAL OF BIOMECHANICS, 153.

By: E. McCain*, M. Dalman n, M. Berno n, T. Libera n, M. Lewek*, G. Sawicki*, K. Saul n

author keywords: Musculoskeletal modeling; Simulation; Joint restriction; Joint reaction force
MeSH headings : Humans; Gait / physiology; Knee Joint / physiology; Lower Extremity / physiology; Knee; Walking / physiology; Biomechanical Phenomena
TL;DR: While joint restriction results in increased limb loading, reductions in muscle forces counteract changes in limb loading such that JRFs were relatively unchanged, similar to other JRFs investigated. (via Semantic Scholar)
UN Sustainable Development Goal Categories
3. Good Health and Well-being (OpenAlex)
Source: Web Of Science
Added: June 12, 2023

2021 journal article

Isolating the energetic and mechanical consequences of imposed reductions in ankle and knee flexion during gait

JOURNAL OF NEUROENGINEERING AND REHABILITATION, 18(1).

By: E. McCain n, T. Libera n, M. Berno n, G. Sawicki*, K. Saul n & M. Lewek*

author keywords: Biomechanics; Gait; Ankle; Knee; Metabolic cost
MeSH headings : Adaptation, Physiological / physiology; Adult; Ankle; Ankle Joint / physiology; Biomechanical Phenomena; Female; Gait / physiology; Humans; Knee Joint / physiology; Male; Range of Motion, Articular / physiology; Walking; Young Adult
TL;DR: As expected, reduced ankle motion, either without ( restricted-ank) or in addition to knee restriction (restricted-a + k) yielded significant increase in net metabolic rate when compared with the braced condition, and the relative increase in metabolic cost was significantly larger with restricted-a'+’k when compared to restricted-knee condition. (via Semantic Scholar)
Source: Web Of Science
Added: March 15, 2021

2021 journal article

Neuromechanics and Energetics of Walking With an Ankle Exoskeleton Using Neuromuscular-Model Based Control: A Parameter Study

FRONTIERS IN BIOENGINEERING AND BIOTECHNOLOGY, 9.

By: B. Shafer*, S. Philius n, R. Nuckols*, J. McCall n, A. Young* & G. Sawicki*

author keywords: powered ankle exoskeleton; neuromuscular model; locomotion neuromechanics; human walking; muscle electromyography; metabolic energy cost; plantarflexor muscle-tendon mechanics
TL;DR: An ankle exoskeleton controller is developed that uses a neuromuscular model (NMM) comprised of a Hill type musculotendon driven by a simple positive force feedback reflex loop to capture the adaptive behavior of the human plantarflexors during natural gait. (via Semantic Scholar)
Source: Web Of Science
Added: May 10, 2021

2021 article

Reduced Achilles Tendon Stiffness Disrupts Calf Muscle Neuromechanics in Elderly Gait

Krupenevich, R. L., Beck, O. N., Sawicki, G. S., & Franz, J. R. (2021, July 16). GERONTOLOGY.

By: R. Krupenevich n, O. Beck*, G. Sawicki* & J. Franz n

author keywords: Aging; Biomechanics; Stiffness; Energy expenditure; Muscle mechanics; Ankle exoskeleton
MeSH headings : Achilles Tendon / physiology; Aged; Ankle / physiology; Ankle Joint / physiology; Biomechanical Phenomena / physiology; Gait / physiology; Humans; Muscle, Skeletal / physiology; Walking / physiology
TL;DR: The hypothesis that age-related declines in Achilles tendon stiffness increase the metabolic cost of walking due to less economical calf muscle contractions and increased proximal joint work is explored. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 2, 2021

2021 journal article

Reduced joint motion supersedes asymmetry in explaining increased metabolic demand during walking with mechanical restriction

JOURNAL OF BIOMECHANICS, 126.

By: E. McCain n, M. Berno n, T. Libera n, M. Lewek*, G. Sawicki* & K. Saul n

author keywords: Gait; Asymmetry; Metabolic cost; Degrees of freedom; Joint restriction
MeSH headings : Ankle Joint; Biomechanical Phenomena; Gait; Humans; Knee Joint; Walking
TL;DR: The results emphasize symmetry is not by definition metabolically optimal, indicate that the mechanics underlying symmetry are meaningful, and suggest that available degrees of freedom should be considered in designing future interventions. (via Semantic Scholar)
Source: Web Of Science
Added: October 12, 2021

2020 journal article

Impact of elastic ankle exoskeleton stiffness on neuromechanics and energetics of human walking across multiple speeds

JOURNAL OF NEUROENGINEERING AND REHABILITATION, 17(1).

By: R. Nuckols* & G. Sawicki*

author keywords: Locomotion; Wearable robotics; Plantarflexors; Spring-loaded; Lower-limb joints; Biomechanics; Metabolic cost; Compliant
MeSH headings : Adult; Ankle Joint / physiology; Biomechanical Phenomena / physiology; Energy Metabolism / physiology; Exoskeleton Device; Female; Humans; Male; Muscle, Skeletal / physiology; Walking / physiology
TL;DR: The relationship between the non-weighted sum of soleus and tibialis activation rate and metabolic cost indicates that muscle activation may drive metabolic demand in exoskeleton systems, and elastic ankle exoskeletons with low rotational stiffness reduce users’ metabolic cost at slow and fast but not intermediate walking speed. (via Semantic Scholar)
Source: Web Of Science
Added: July 13, 2020

2020 journal article

Older Adults Overcome Reduced Triceps Surae Structural Stiffness to Preserve Ankle Joint Quasi-Stiffness During Walking

JOURNAL OF APPLIED BIOMECHANICS, 36(4), 209–216.

By: R. Krupenevich n, W. Clark n, G. Sawicki* & J. Franz n

author keywords: Achilles tendon; activation; aging; plantar flexor; biofeedback
TL;DR: Despite age-related reductions during isolated contractions, ankle joint quasi-stiffness was maintained in older adults during walking, which may be governed via activation-mediated increases in muscle stiffness. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: August 17, 2020

2019 journal article

Development of a Novel Gait Analysis Tool Measuring Center of Pressure for Evaluation of Canine Chronic Thoracolumbar Spinal Cord Injury

Journal of Neurotrauma, 36(21), 3018–3025.

By: M. Lewis*, K. Williams*, T. Langley*, L. Jarvis*, G. Sawicki* & N. Olby n

author keywords: center of pressure; chronic spinal cord injury; dogs; locomotion; postural control
MeSH headings : Animals; Dogs; Gait Analysis / instrumentation; Lumbar Vertebrae; Postural Balance / physiology; Spinal Cord Injuries / veterinary; Thoracic Vertebrae
TL;DR: COP analysis and body weight support measurements offer information about post-injury locomotion and further development is needed before consideration as an outcome measure to complement validated gait analysis methods in dogs with SCI. (via Semantic Scholar)
UN Sustainable Development Goal Categories
3. Good Health and Well-being (Web of Science; OpenAlex)
Sources: Web Of Science, NC State University Libraries, Crossref
Added: June 24, 2019

2019 journal article

Mechanics and energetics of post-stroke walking aided by a powered ankle exoskeleton with speed-adaptive myoelectric control

JOURNAL OF NEUROENGINEERING AND REHABILITATION, 16.

By: E. McCain n, T. Dick*, T. Giest n, R. Nuckols*, M. Lewek*, K. Saul n, G. Sawicki*

author keywords: Ankle mechanics; Exoskeleton; Trailing limb angle; Propulsion; Myoelectric control; Electromyography; Metabolic cost; Hemiparesis; Stroke rehabilitation; Walking
MeSH headings : Adult; Ankle Joint / physiology; Biomechanical Phenomena / physiology; Electromyography / methods; Exoskeleton Device; Female; Humans; Male; Middle Aged; Stroke Rehabilitation / instrumentation; Walking / physiology; Walking Speed / physiology
TL;DR: The results suggest that despite appropriate scaling of ankle assistance by the exoskeleton controller, suboptimal limb posture limited the conversion of exoskeletons assistance into forward propulsion. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: June 4, 2019

2017 journal article

A benchtop biorobotic platform for in vitro observation of muscle-tendon dynamics with parallel mechanical assistance from an elastic exoskeleton

JOURNAL OF BIOMECHANICS, 57, 8–17.

By: B. Robertson n, S. Vadakkeveedu n & G. Sawicki n

author keywords: Biomechanics; Elastic exoskeleton; Muscle-tendon mechanics; Unconstrained work loops; Biorobotics
MeSH headings : Animals; Biomechanical Phenomena; Elasticity; Gravitation; Locomotion / physiology; Muscle, Skeletal / physiology; Ranidae; Robotics / instrumentation; Tendons / physiology
TL;DR: Findings from this study suggest that the increased natural resonant frequency of the artificially stiffened MTU+Exo system, along with invariant movement frequencies, may underlie observed limits on the benefits of exoskeleton assistance. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Source: Web Of Science
Added: August 6, 2018

2017 article

An In Vitro Approach for Directly Observing Muscle-Tendon Dynamics with Parallel Elastic Mechanical Assistance

CONVERGING CLINICAL AND ENGINEERING RESEARCH ON NEUROREHABILITATION II, VOLS 1 AND 2, Vol. 15, pp. 643–647.

By: G. Sawicki n & B. Robertson*

TL;DR: A novel benchtop approach is offered by introducing a ‘smart’ robotic interface into the framework of biological muscle-tendon work loop experiments in order to simulate the local dynamical environment muscles experience in vivo during locomotion with exoskeleton assistance. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2017 journal article

Quantifying center of pressure variability in chondrodystrophoid dogs

The Veterinary Journal, 226, 26–31.

By: S. Blau n, L. Davis n, A. Gorney n, C. Dohse n, K. Williams n, J. Lim n, W. Pfitzner n, E. Laber n, G. Sawicki n, N. Olby n

author keywords: Locomotion; Kinematics; Center of gravity
MeSH headings : Animals; Biomechanical Phenomena; Cartilage / growth & development; Dog Diseases / physiopathology; Dogs / anatomy & histology; Dogs / physiology; Gait; Species Specificity; Spinal Cord Injuries / physiopathology; Spinal Cord Injuries / veterinary
TL;DR: In conclusion, COP variability can be measured consistently in dogs, and a range of COP variability for normal chondrodystrophoid dogs has been determined to provide a baseline for future studies on dogs with spinal cord injury. (via Semantic Scholar)
UN Sustainable Development Goal Categories
3. Good Health and Well-being (Web of Science; OpenAlex)
Sources: Web Of Science, Crossref, NC State University Libraries
Added: August 6, 2018

2017 journal article

The springs of time-limited bullfrog jumps and slow-preparation grasshopper leaps are tuned to their muscle dynamics

Integrative and Comparative Biology, 57, E390–390.

By: M. Rosario, G. Sutton, S. Patek & G. Sawicki

Source: NC State University Libraries
Added: August 6, 2018

2016 journal article

A Simple Model to Estimate Plantarflexor Muscle-Tendon Mechanics and Energetics During Walking With Elastic Ankle Exoskeletons

IEEE TRANSACTIONS ON BIOMEDICAL ENGINEERING, 63(5), 914–923.

By: G. Sawicki n & N. Khan

author keywords: Ankle exoskeleton; computer simulation; elastic energy storage; energetics; Hill-type muscle model; human walking; metabolic cost; muscle-tendon dynamics; plantarflexors (PF)
MeSH headings : Ankle / physiology; Biomechanical Phenomena / physiology; Exoskeleton Device; Humans; Models, Biological; Muscle, Skeletal / physiology; Tendons / physiology; Walking / physiology
TL;DR: The combination of disrupted muscle-tendon dynamics and the need to produce compensatory forces/moments to maintain overall net ankle moment invariance could explain the “sweet spot” in metabolic performance at intermediate ankle exoskeleton stiffness. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2016 journal article

A cyber expert system for auto-tuning powered prosthesis impedance control parameters

Annals of Biomedical Engineering, 44(5), 1613–1624.

By: H. Huang n, D. Crouch n, M. Liu n, G. Sawicki n & D. Wang n

Contributors: H. Huang n, D. Crouch n, M. Liu n, G. Sawicki n & D. Wang n

MeSH headings : Ankle Joint; Electric Impedance; Female; Gait; Humans; Knee Joint; Knee Prosthesis; Male; Walking
TL;DR: A novel cyber expert system that encoded HME tuning decisions as computer rules to auto-tune control parameters for a powered knee (passive ankle) prosthesis and observed normative prosthetic knee kinematics and improved or slightly improved gait symmetry and step width within each subject. (via Semantic Scholar)
UN Sustainable Development Goal Categories
Sources: NC State University Libraries, NC State University Libraries, ORCID
Added: August 6, 2018

2016 journal article

Adding Stiffness to the Foot Modulates Soleus Force-Velocity Behaviour during Human Walking

SCIENTIFIC REPORTS, 6.

By: K. Takahashi*, M. Gross*, H. Werkhoven*, S. Piazza* & G. Sawicki n

MeSH headings : Ankle / physiology; Biomechanical Phenomena / physiology; Foot / physiology; Gait / physiology; Humans; Muscle, Skeletal / physiology; Walking / physiology
TL;DR: This work investigated foot-ankle interplay during walking by adding stiffness to the foot through shoes and insoles and characterized the resulting changes in in vivo soleus muscle-tendon mechanics using ultrasonography. (via Semantic Scholar)
UN Sustainable Development Goal Categories
5. Gender Equality (Web of Science)
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2016 journal article

Modeling age-related changes in muscle-tendon dynamics during cyclical contractions in the rat gastrocnemius

JOURNAL OF APPLIED PHYSIOLOGY, 121(4), 1004–1012.

By: N. Danos*, N. Holt*, G. Sawicki n & E. Azizi*

author keywords: aging; elastic energy; cost of locomotion; fibrosis; ankle joint work
MeSH headings : Aging / physiology; Animals; Computer Simulation; Elastic Modulus / physiology; Male; Models, Biological; Muscle, Skeletal / physiology; Oscillometry; Rats; Rats, Inbred F344; Stress, Mechanical; Tendons / physiology; Tensile Strength / physiology
TL;DR: The results suggest that the observed increase in the metabolic cost of locomotion with aging may be in part due to the recruitment of additional muscles to compensate for the reduced work at the primary MTU. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2016 journal article

Muscle-spring dynamics in time-limited, elastic movements

author keywords: muscle-spring interaction; elastic energy storage; muscle dynamics; time-limited loading; fixed-end contraction; spring stiffness
MeSH headings : Animals; Biomechanical Phenomena; Grasshoppers / physiology; Movement; Muscle Contraction; Muscle, Skeletal / physiology; Ranidae / physiology; Tendons / physiology
TL;DR: The findings demonstrate the significance of evolutionary variation in tendon and apodeme properties to realistic jumping contexts as well as the importance of considering the effect of muscle dynamics and behavioural constraints on energy storage in muscle–spring systems. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
15. Life on Land (Web of Science)
Source: Web Of Science
Added: August 6, 2018

2015 journal article

A neuromechanics-based powered ankle exoskeleton to assist walking post-stroke: a feasibility study

JOURNAL OF NEUROENGINEERING AND REHABILITATION, 12.

By: K. Takahashi n, M. Lewek* & G. Sawicki n

author keywords: Stroke; Exoskeleton; Gait; Rehabilitation; Ankle
MeSH headings : Aged; Aged, 80 and over; Ankle; Ankle Joint; Artificial Limbs; Biomechanical Phenomena; Bionics; Electromyography; Energy Metabolism; Feasibility Studies; Female; Foot; Humans; Male; Mechanical Phenomena; Middle Aged; Paresis / rehabilitation; Prosthesis Design; Robotics; Stroke Rehabilitation; Walking
TL;DR: This feasibility study demonstrated that the exoskeleton can enhance paretic ankle moment, and appeared to reduce the net metabolic power gradually with each 5 minute repetition, though no statistical significance was found. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2015 journal article

Individual limb mechanical analysis of gait following stroke

JOURNAL OF BIOMECHANICS, 48(6), 984–989.

By: C. Mahon n, D. Farris*, G. Sawicki n & M. Lewek*

author keywords: Stroke; Hemiplegia; Rehabilitation; Gait; Mechanics
MeSH headings : Aged; Chronic Disease; Exercise Test; Extremities / physiopathology; Female; Gait / physiology; Humans; Male; Middle Aged; Stroke / physiopathology; Walking / physiology
TL;DR: Comparison of individual limb mechanical gait asymmetries during the step-to-step transitions, single-support and over a complete stride between two groups of individuals following stroke stratified by gait speed suggests that limb power output may be dominated by vertical components, which are required for upright support. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2015 article

More is not always better: Modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics (vol 9, 046018, 2014)

Bioinspiration & Biomimetics, Vol. 10.

By: B. Robertson, D. Farris & G. Sawicki

Source: NC State University Libraries
Added: August 6, 2018

2015 journal article

Power amplification in an isolated muscle-tendon unit is load dependent

JOURNAL OF EXPERIMENTAL BIOLOGY, 218(22), 3700–3709.

By: G. Sawicki n, P. Sheppard* & T. Roberts*

author keywords: Muscle-tendon system; Elastic energy; Power amplification; Catch mechanism; Acceleration; Jumping
MeSH headings : Animals; Biomechanical Phenomena; Elasticity; Energy Transfer; Locomotion / physiology; Muscle Contraction; Muscle, Skeletal / physiology; Rana catesbeiana / physiology; Tendons / physiology
TL;DR: Power amplification in a compliant muscle-tendon unit is maximal for intermediate inertial-gravitational loads and can be enhanced by a trigger and catch mechanism for small loads. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2015 journal article

Reducing the energy cost of human walking using an unpowered exoskeleton

NATURE, 522(7555), 212-+.

By: S. Collins*, M. Wiggin n & G. Sawicki n

MeSH headings : Ankle / physiology; Artificial Limbs; Bionics / instrumentation; Bionics / methods; Energy Metabolism; Female; Foot / physiology; Humans; Leg / physiology; Male; Muscle, Skeletal / physiology; Walking / physiology; Young Adult
TL;DR: This work built a lightweight elastic device that acts in parallel with the user's calf muscles, off-loading muscle force and thereby reducing the metabolic energy consumed in contractions, and shows that the metabolic rate of human walking can be reduced by an unpowered ankle exoskeleton. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2015 journal article

Revisiting the mechanics and energetics of walking in individuals with chronic hemiparesis following stroke: from individual limbs to lower limb joints

JOURNAL OF NEUROENGINEERING AND REHABILITATION, 12.

By: D. Farris n, A. Hampton n, M. Lewek* & G. Sawicki n

author keywords: Locomotion; Individual limbs method; Mechanical power; Metabolic power; Joint power; Inverse dynamics; Stroke
MeSH headings : Aged; Ankle Joint / physiopathology; Biomechanical Phenomena; Calorimetry, Indirect; Chronic Disease; Energy Metabolism; Female; Gait; Hip Joint / physiopathology; Humans; Joints / physiopathology; Knee Joint / physiopathology; Locomotion; Lower Extremity / physiopathology; Male; Mechanical Phenomena; Middle Aged; Paresis / etiology; Paresis / physiopathology; Self-Help Devices; Stroke / complications; Stroke / physiopathology
TL;DR: A comparison of the mechanics and energetics of hemiparetic and unimpaired walking at a matched speed highlighted the need to target improving paretic ankle push-off via therapy or assistive technology in order to reduce the metabolic cost of hemIParetic walking. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2015 journal article

Six degree-of-freedom analysis of hip, knee, ankle and foot provides updated understanding of biomechanical work during human walking

JOURNAL OF EXPERIMENTAL BIOLOGY, 218(6), 876–886.

By: K. Zelik*, K. Takahashi n & G. Sawicki n

author keywords: Biomechanics; Foot work; Gait analysis; Inverse dynamics; Joint work; Mechanical work
MeSH headings : Adult; Ankle Joint / physiology; Biomechanical Phenomena; Female; Foot / physiology; Hip Joint / physiology; Humans; Knee Joint / physiology; Male; Walking; Young Adult
TL;DR: Six degree-of-freedom (6DOF) analysis of hip–knee–ankle–foot better captures energy changes of the body during gait than conventional 3DOF joint work estimates, revealing increased work contributions from the hip. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2015 journal article

Timing matters: tuning the mechanics of a muscle-tendon unit by adjusting stimulation phase during cyclic contractions

JOURNAL OF EXPERIMENTAL BIOLOGY, 218(19), 3150–3159.

By: G. Sawicki n, B. Robertson n, E. Azizi* & T. Roberts*

author keywords: Muscle-tendon interaction; Muscle stimulation phase; Work loop; Elastic energy storage and return; Terrestrial locomotion
MeSH headings : Animals; Biomechanical Phenomena; Locomotion / physiology; Muscle Contraction / physiology; Muscle, Skeletal / physiology; Rana catesbeiana / physiology; Tendons / physiology
TL;DR: During cyclic contractions of a muscle–tendon unit, the timing of muscle stimulation onset determines whether the muscle acts like a force producing strut, energy generating motor or energy absorbing brake. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2014 journal article

Exploiting elasticity: Modeling the influence of neural control on mechanics and energetics of ankle muscle-tendons during human hopping

JOURNAL OF THEORETICAL BIOLOGY, 353, 121–132.

By: B. Robertson n & G. Sawicki n

author keywords: Plantarflexors; Locomotion; Muscle mechanics; Metabolic cost; Elastic mechanisms
MeSH headings : Ankle / physiology; Basal Metabolism; Biomechanical Phenomena; Elasticity; Energy Metabolism / physiology; Humans; Models, Biological; Motor Activity / physiology; Muscle Contraction / physiology; Muscle, Skeletal / physiology; Nervous System Physiological Phenomena; Tendons / physiology
TL;DR: Frequency and amplitude of stimulation both played integral roles in determining CE F-L operating point, with both higher frequency and amplitude generally corresponding to lower CE strains, reduced injury risk, and elimination of the need for passive force generation in the CE parallel elastic element (PEE). (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2014 journal article

More is not always better: modeling the effects of elastic exoskeleton compliance on underlying ankle muscle-tendon dynamics

BIOINSPIRATION & BIOMIMETICS, 9(4).

By: B. Robertson n, D. Farris n & G. Sawicki n

author keywords: elastic ankle exoskeleton; muscle-tendon interaction; mechanics; energetics; hopping; ultrasound
MeSH headings : Biomimetics / instrumentation; Computer Simulation; Computer-Aided Design; Elastic Modulus / physiology; Equipment Design; Equipment Failure Analysis; Humans; Man-Machine Systems; Models, Biological; Movement / physiology; Muscle Contraction / physiology; Muscle, Skeletal / physiology; Orthotic Devices; Robotics / instrumentation; Tendons / physiology
TL;DR: A simple, predictive model of human neuromechanical adaptation to a passive elastic exoskeleton applied at the ankle joint during a functional task concluded that both of these outcomes cannot be achieved simultaneously, and that one must come at the detriment of the other in a spring-assisted compliant MTU. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2014 journal article

Musculoskeletal modelling deconstructs the paradoxical effects of elastic ankle exoskeletons on plantar-flexor mechanics and energetics during hopping

JOURNAL OF EXPERIMENTAL BIOLOGY, 217(22), 4018–4028.

By: D. Farris n, J. Hicks*, S. Delp* & G. Sawicki n

author keywords: Assistive robotics; Dynamics simulation; Energetics; Locomotion; Metabolic energy; Muscle mechanics
MeSH headings : Adult; Ankle Joint / physiology; Biomechanical Phenomena; Electromyography; Energy Metabolism / physiology; Gait / physiology; Humans; Male; Models, Theoretical; Muscle, Skeletal / physiology; Orthotic Devices; Tendons / physiology
TL;DR: A musculoskeletal model of the human leg and a model of muscle energetics in simulations of muscle–tendon dynamics during hopping with and without elastic ankle exoskeletons showed that the total rate of metabolic energy consumption by ankle muscles was not significantly reduced by an ankleExoskeleton. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2013 journal article

Elastic ankle exoskeletons reduce soleus muscle force but not work in human hopping

JOURNAL OF APPLIED PHYSIOLOGY, 115(5), 579–585.

By: D. Farris n, B. Robertson n & G. Sawicki n

author keywords: ultrasound; fascicle; tendon; metabolic power; plantar flexors
MeSH headings : Adult; Ankle / physiology; Ankle Joint / physiology; Electromyography / methods; Energy Metabolism / physiology; Humans; Leg / physiopathology; Male; Muscle, Skeletal / physiology; Tendons / physiology; Walking / physiology
TL;DR: The findings highlighted that parallel assistance to a muscle with appreciable series elasticity may have some negative consequences, and that the metabolic cost associated with generating force may be more pronounced than the cost of doing work for these muscles. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2013 journal article

Estimation of Quasi-Stiffness and Propulsive Work of the Human Ankle in the Stance Phase of Walking

PLOS ONE, 8(3).

By: K. Shamaei*, G. Sawicki n & A. Dollar*

MeSH headings : Adult; Ankle / physiology; Ankle Joint / physiology; Biomechanical Phenomena; Female; Gait; Humans; Leg / physiology; Male; Regression Analysis; Stress, Mechanical; Walking
TL;DR: This work aims to establish statistical models that allow us to predict the ankle quasi-stiffness and net mechanical work for adults walking on level ground and discusses how these models provide a useful framework and foundation for designing subject- and gait-specific prosthetic and exoskeletal devices designed to emulate biological ankle function during level ground walking. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2013 journal article

Estimation of Quasi-Stiffness of the Human Hip in the Stance Phase of Walking

PLOS ONE, 8(12).

By: K. Shamaei*, G. Sawicki n & A. Dollar*

MeSH headings : Adult; Biomechanical Phenomena; Female; Gait / physiology; Hip / anatomy & histology; Hip / physiology; Hip Joint / anatomy & histology; Hip Joint / physiology; Humans; Male; Models, Statistical; Orthotic Devices; Range of Motion, Articular / physiology; Regression Analysis; Walking / physiology
TL;DR: This work presents a framework for selection of subject-specific quasi-stiffness of hip orthoses and exoskeletons, and other devices that are intended to emulate the biological performance of this joint during walking. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2013 journal article

Estimation of Quasi-Stiffness of the Human Knee in the Stance Phase of Walking

PLOS ONE, 8(3).

By: K. Shamaei*, G. Sawicki n & A. Dollar*

MeSH headings : Biomechanical Phenomena; Gait / physiology; Humans; Knee Joint / physiology; Locomotion / physiology; Models, Theoretical; Walking / physiology
TL;DR: A generalized inverse dynamics analysis approach identifies key independent variables needed to predict knee quasi-stiffness during walking, including gait speed, knee excursion, and subject height and weight, and provides a useful framework and foundation for selecting subject-specific stiffness for prosthetic and exoskeletal devices designed to emulate biological knee function during walking. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2012 journal article

Elastic recoil can either amplify or attenuate muscle-tendon power, depending on inertial vs. fluid dynamic loading

JOURNAL OF THEORETICAL BIOLOGY, 313, 68–78.

By: C. Richards* & G. Sawicki n

author keywords: Muscle power amplification; Gearing; Mechanical advantage; Mathematical model; Inertial and viscous loads
MeSH headings : Animals; Biomechanical Phenomena / physiology; Computer Simulation; Elasticity; Hydrodynamics; Models, Biological; Muscle Contraction / physiology; Muscle, Skeletal / physiology; Tendons / physiology; Xenopus laevis
TL;DR: The model predicts that for fluid loads, the benefit from a compliant tendon is modest, and when the system is 'poorly tuned' (i.e., inappropriate EMA), MT power attenuation can be severe. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2012 journal article

Human medial gastrocnemius force-velocity behavior shifts with locomotion speed and gait

PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA, 109(3), 977–982.

By: D. Farris n & G. Sawicki n

author keywords: muscle mechanics; biomechanics; preferred transition speed
MeSH headings : Adult; Behavior / physiology; Biomechanical Phenomena / physiology; Elasticity / physiology; Female; Gait / physiology; Humans; Locomotion / physiology; Male; Muscle, Skeletal / anatomy & histology; Muscle, Skeletal / physiology; Walking / physiology; Young Adult
TL;DR: MG fascicle velocity may be a key factor that limits the speeds humans choose to walk at, and may explain the transition from walking to running. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2012 journal article

The influence of a unilateral fixed ankle on metabolic and mechanical demands during walking in unimpaired young adults

JOURNAL OF BIOMECHANICS, 45(14), 2405–2410.

By: C. Wutzke*, G. Sawicki n & M. Lewek*

author keywords: Gait; Biomechanics; Metabolic cost; Ankle
MeSH headings : Adult; Ankle; Energy Metabolism; Female; Hip; Humans; Male; Muscle Strength; Orthopedic Fixation Devices; Walking
TL;DR: It is suggested that walking with reduced ankle power increases metabolic demand due to the redistribution of mechanical power generation from highly efficient ankle muscle-tendons to less efficient hip muscle-Tendons. (via Semantic Scholar)
UN Sustainable Development Goal Categories
7. Affordable and Clean Energy (OpenAlex)
Source: Web Of Science
Added: August 6, 2018

2012 journal article

The mechanics and energetics of human walking and running: a joint level perspective

JOURNAL OF THE ROYAL SOCIETY INTERFACE, 9(66), 110–118.

By: D. Farris n & G. Sawicki n

author keywords: locomotion; speed; mechanical power; efficiency; cost of transport
MeSH headings : Adult; Ankle Joint / physiology; Biomechanical Phenomena; Calorimetry, Indirect; Energy Metabolism; Female; Gait; Hip Joint / physiology; Humans; Knee Joint / physiology; Male; Running; Walking
TL;DR: Changing from walking to running resulted in a significant shift in power production from the hip to the ankle which may explain the higher efficiency of running at speeds above 2.0 m s−1 and shed light on a potential mechanism behind the walk–run transition. (via Semantic Scholar)
Source: Web Of Science
Added: August 6, 2018

2011 conference paper

Influence of parallel spring-loaded exoskeleton on ankle muscle-tendon dynamics during simulated human hopping

2011 Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC), 583–586.

By: B. Robertson n & G. Sawicki n

MeSH headings : Achilles Tendon / physiology; Ankle Joint / physiology; Computer Simulation; Humans; Locomotion / physiology; Models, Biological; Muscle Contraction / physiology; Muscle, Skeletal / physiology; Orthotic Devices; Robotics / methods; Therapy, Computer-Assisted / methods
TL;DR: It is found that, in most cases, uniform cyclic mechanical power production of the coupled system is achieved and unassisted power production can be reproduced throughout parameter space by trading off decreases in muscle activation with increases in ankle exoskeleton spring stiffness. (via Semantic Scholar)
Source: NC State University Libraries
Added: August 6, 2018

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