scholarly journals Soft tissue deformations explain most of the mechanical work variations of human walking

2021 ◽  
Author(s):  
Tim J. van der Zee ◽  
Arthur D. Kuo
Keyword(s):  
Soft Tissue ◽  
Soft Tissues ◽  
Metabolic Cost ◽  
Step Length ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Whole Body ◽  
Human Walking ◽  
Negative Work ◽  
Tissue Deformations

AbstractHumans perform mechanical work during walking, some by leg joints actuated by muscles, and some by passive, dissipative soft tissues. Dissipative losses must be restored by active muscle work, potentially in amounts sufficient to cost substantial metabolic energy. The most dissipative, and therefore costly, walking conditions might be predictable from the pendulum-like dynamics of the legs. If pendulum behavior is systematic, it may also predict the work distribution between active joints and passive soft tissues. We therefore tested whether the overall negative work of walking, and the fraction due to soft tissue dissipation, are both predictable by a pendulum model across a wide range of conditions. The model predicts whole-body negative work from the leading leg’s impact with ground (termed the Collision), to increase with the squared product of walking speed and step length. We experimentally tested this in humans (N = 9) walking in 26 different combinations of speed (0.7 – 2.0 m·s-1) and step length (0.5 – 1.1 m), with recorded motions and ground reaction forces. Whole-body negative Collision work increased as predicted (R2= 0.73), with a consistent fraction of about 63% (R2= 0.88) due to soft tissues. Soft tissue dissipation consistently accounted for about 56% of the variation in total whole-body negative work. During typical walking, active work to restore dissipative losses could account for 31% of the net metabolic cost. Soft tissue dissipation, not included in most biomechanical studies, explains most of the variation in negative work of walking, and could account for a substantial fraction of the metabolic cost.Summary statementSoft tissue deformations dissipate substantial energy during human walking, as predicted by a simple walking model.

scholarly journals Soft tissue deformations explain most of the mechanical work variations of human walking

2021 ◽  
Author(s):  
Tim J. van der Zee ◽  
Arthur D. Kuo
Keyword(s):  
Soft Tissue ◽  
Soft Tissues ◽  
Metabolic Cost ◽  
Step Length ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Whole Body ◽  
Negative Work ◽  
Work Distribution ◽  
Wide Range

Humans perform mechanical work during walking, some by leg joints actuated by muscles, and some by passive, dissipative soft tissues. Dissipative losses must be restored by active muscle work, potentially in amounts sufficient to cost substantial metabolic energy. The most dissipative, and therefore costly, walking conditions might be predictable from the pendulum-like dynamics of the legs. If this behavior is systematic, it may also predict the work distribution between active joints and passive soft tissues. We therefore tested whether the overall negative work of walking, and the fraction due to soft tissue dissipation, are both predictable by a simple dynamic walking model across a wide range of conditions. The model predicts whole-body negative work from the leading leg's impact with ground (termed the Collision), to increase with the squared product of walking speed and step length. We experimentally tested this in humans (N=9) walking in 26 different combinations of speed (0.7 – 2.0 m·s−1) and step length (0.5 – 1.1 m), with recorded motions and ground reaction forces. Whole-body negative Collision work increased as predicted (R2=0.73), with a consistent fraction of about 63% (R2=0.88) due to soft tissues. Soft tissue dissipation consistently accounted for about 56% of the variation in total whole-body negative work, across a wide range of speed and step length combinations. During typical walking, active work to restore dissipative losses could account for 31% of the net metabolic cost. Soft tissue dissipation, not included in most biomechanical studies, explains most of the variation in negative work of walking, and could account for a substantial fraction of the metabolic cost.

scholarly journals Using a simple rope-pulley system that mechanically couples the arms, legs, and treadmill reduces the metabolic cost of walking

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Daisey Vega ◽  
Christopher J. Arellano
Keyword(s):  
Metabolic Cost ◽  
Metabolic Energy ◽  
Metabolic Effects ◽  
Whole Body ◽  
Walking Ability ◽  
Arm Swing ◽  
Pulley System ◽  
Young Subjects ◽  
Walking Recovery ◽  
Set Up

Abstract Background Emphasizing the active use of the arms and coordinating them with the stepping motion of the legs may promote walking recovery in patients with impaired lower limb function. Yet, most approaches use seated devices to allow coupled arm and leg movements. To provide an option during treadmill walking, we designed a rope-pulley system that physically links the arms and legs. This arm-leg pulley system was grounded to the floor and made of commercially available slotted square tubing, solid strut channels, and low-friction pulleys that allowed us to use a rope to connect the subject’s wrist to the ipsilateral foot. This set-up was based on our idea that during walking the arm could generate an assistive force during arm swing retraction and, therefore, aid in leg swing. Methods To test this idea, we compared the mechanical, muscular, and metabolic effects between normal walking and walking with the arm-leg pulley system. We measured rope and ground reaction forces, electromyographic signals of key arm and leg muscles, and rates of metabolic energy consumption while healthy, young subjects walked at 1.25 m/s on a dual-belt instrumented treadmill (n = 8). Results With our arm-leg pulley system, we found that an assistive force could be generated, reaching peak values of 7% body weight on average. Contrary to our expectation, the force mainly coincided with the propulsive phase of walking and not leg swing. Our findings suggest that subjects actively used their arms to harness the energy from the moving treadmill belt, which helped to propel the whole body via the arm-leg rope linkage. This effectively decreased the muscular and mechanical demands placed on the legs, reducing the propulsive impulse by 43% (p < 0.001), which led to a 17% net reduction in the metabolic power required for walking (p = 0.001). Conclusions These findings provide the biomechanical and energetic basis for how we might reimagine the use of the arms in gait rehabilitation, opening the opportunity to explore if such a method could help patients regain their walking ability. Trial registration: Study registered on 09/29/2018 in ClinicalTrials.gov (ID—NCT03689647).

scholarly journals Checklist and Scoring System for the Assessment of Soft Tissue Preservation in CT Examinations of Human Mummies: Application to the Tyrolean Iceman

2017 ◽  
Vol 189 (12) ◽  
pp. 1152-1160
Author(s):  
Stephanie Panzer ◽  
Patrizia Pernter ◽  
Dario Piombino-Mascali ◽  
Rimantas Jankauskas ◽  
Stephanie Zesch ◽  
...  
Keyword(s):  
Soft Tissue ◽  
Scoring System ◽  
Soft Tissues ◽  
Whole Body ◽  
Slice Thickness ◽  
Tissue Preservation ◽  
Soft Tissue Preservation ◽  
Whole Body Ct ◽  
Organ Systems ◽  
Tyrolean Iceman

Purpose Soft tissues make a skeleton into a mummy and they allow for a diagnosis beyond osteology. Following the approach of structured reporting in clinical radiology, a recently developed checklist was used to evaluate the soft tissue preservation status of the Tyrolean Iceman using computed tomography (CT). The purpose of this study was to apply the “Checklist and Scoring System for the Assessment of Soft Tissue Preservation in CT Examinations of Human Mummies” to the Tyrolean Iceman, and to compare the Iceman’s soft tissue preservation score to the scores calculated for other mummies. Materials and Methods A whole-body (CT) (SOMATOM Definition Flash, Siemens, Forchheim, Germany) consisting of five scans, performed in January 2013 in the Department of Radiodiagnostics, Central Hospital, Bolzano, was used (slice thickness 0.6 mm; kilovolt ranging from 80 to 140). For standardized evaluation the “CT Checklist and Scoring System for the Assessment of Soft Tissue Preservation in Human Mummies” was used. Results All checkpoints under category “A. Soft Tissues of Head and Musculoskeletal System” and more than half in category “B. Organs and Organ Systems” were observed. The scoring system accounted for a total score of 153 (out of 200). The comparison of the scores between the Iceman and three mummy collections from Vilnius, Lithuania, and Palermo, Sicily, as well as one Egyptian mummy resulted in overall higher soft tissue preservation scores for the Iceman. Conclusion Application of the checklist allowed for standardized assessment and documentation of the Iceman’s soft tissue preservation status. The scoring system allowed for a quantitative comparison between the Iceman and other mummies. The Iceman showed remarkable soft tissue preservation. Key Points  Citation Format

scholarly journals Disentangling the energetic costs of step time asymmetry and step length asymmetry in human walking

2021 ◽  
Author(s):  
Jan Stenum ◽  
Julia T. Choi
Keyword(s):  
Energy Cost ◽  
Metabolic Cost ◽  
Step Length ◽  
Human Walking ◽  
Metabolic Power ◽  
Healthy Human ◽  
Time Asymmetry ◽  
Double Support ◽  
Post Stroke ◽  
The Cost

The metabolic cost of walking in healthy individuals increases with spatiotemporal gait asymmetries. Pathological gait, such as post-stroke, often has asymmetry in step lengths and step times which may contribute to an increased energy cost. But paradoxically, enforcing step length symmetry does not reduce metabolic cost of post-stroke walking. The isolated and interacting costs of asymmetry in step times and step lengths remain unclear, because previous studies did not simultaneously enforce spatial and temporal gait asymmetries. Here, we delineate isolated costs of asymmetry in step times and step lengths in healthy human walking. We first show that the cost of step length asymmetry is predicted by the cost of taking two non-preferred step lengths (one short and one long), but that step time asymmetry adds an extra cost beyond the cost of non-preferred step times. The metabolic power of step time asymmetry is about 2.5 times greater than the cost of step length asymmetry. Furthermore, the costs are not additive when walking with asymmetric step times and step lengths: metabolic power of concurrent asymmetry in step lengths and step times is driven by the cost of step time asymmetry alone. The metabolic power of asymmetry is explained by positive mechanical power produced during single support phases to compensate for a net loss of center of mass power incurred during double support phases. These data may explain why metabolic cost remains invariant to step length asymmetry in post-stroke walking and suggests how effects of asymmetry on energy cost can be attenuated.

Develop a Flexible Regenerative Exoskeleton to Assist Walking

2018 ◽  
Author(s):  
Longhan Xie ◽  
Xiaodong Li
Keyword(s):  
Kinetic Energy ◽  
Human Body ◽  
Lower Limb ◽  
Metabolic Cost ◽  
Lower Limbs ◽  
Metabolic Energy ◽  
Lower Limb Exoskeleton ◽  
Negative Work ◽  
Lower Limb Muscles ◽  
Assisting Device

During walking, human lower limbs accelerate and decelerate alternately, during which period the human body does positive and negative work, respectively. Muscles provide power to all motions and cost metabolic energy both in accelerating and decelerating the lower limbs. In this work, the lower-limb biomechanics of walking was analyzed and it revealed that if the negative work performed during deceleration can be harnessed using some assisting device to then assist the acceleration movement of the lower limb, the total metabolic cost of the human body during walking can be reduced. A flexible lower-limb exoskeleton was then proposed; it is worn in parallel to the lower limbs to assist human walking without consuming external power. The flexible exoskeleton consists of elastic and damping components that are similar to physiological structure of a human lower limb. When worn on the lower limb, the exoskeleton can partly replace the function of the lower limb muscles and scavenge kinetic energy during lower limb deceleration to assist the acceleration movement. Besides, the generator in the exoskeleton, serving as a damping component, can harvest kinetic energy to produce electricity. A prototype of the flexible exoskeleton was developed, and experiments were carried out to validate the analysis. The experiments showed that the exoskeleton could reduce the metabolic cost by 3.12% at the walking speed of 4.5 km/h.

A FAST COMPUTATION METHOD FOR SOFT TISSUE DEFORMATIONS SIMULATION BASED ON SELF-SELECTION ALGORITHM FOR EMBEDDED OPERATING AREA

2017 ◽  
Vol 17 (07) ◽  
pp. 1740016
Author(s):  
MONAN WANG ◽  
ZHIYONG MAO ◽  
XIANJUN AN
Keyword(s):  
Soft Tissue ◽  
Soft Tissues ◽  
Nonlinear Problems ◽  
Rectus Femoris ◽  
Computation Method ◽  
Biomechanical Models ◽  
Simulation Based ◽  
Material Nonlinear ◽  
Tissue Deformations ◽  
Tissue Models

This study used biomechanical models of soft tissues based on combined exponential and polynomial models. Finite element methods were used to solve material nonlinear and geometrically nonlinear problems of soft tissue models. This involved assigning a screening coefficient in the model-accelerated computing process to filter the units involved in the calculation. The screening coefficient controlled both the accuracy of the results of simulation and the computing speed through setting up a subset of finite elements. The fast computer method based on the screening coefficient was applied to the rectus femoris simulation.

scholarly journals DIGITAL RECONSTRUCTION OF SOFT-TISSUE STRUCTURES IN FOSSILS

2016 ◽  
Vol 22 ◽  
pp. 101-117 ◽  
Author(s):  
Stephan Lautenschlager
Keyword(s):  
Soft Tissue ◽  
Soft Tissues ◽  
Imaging Techniques ◽  
Analytical Techniques ◽  
Computational Imaging ◽  
Whole Body ◽  
Element Analysis ◽  
Digital Reconstruction ◽  
New Information ◽  
Tissue Structures

AbstractIn the last two decades, advances in computational imaging techniques and digital visualization have created novel avenues for the study of fossil organisms. As a result, paleontology has undergone a shift from the pure study of physically preserved bones and teeth, and other hard tissues, to using virtual computer models to study specimens in greater detail, restore incomplete specimens, and perform biomechanical analyses. The rapidly increasing application of these techniques has further paved the way for the digital reconstruction of soft-tissue structures, which are rarely preserved or otherwise available in the fossil record. In this contribution, different types of digital soft-tissue reconstructions are introduced and reviewed. Provided examples include methodological approaches for the reconstruction of musculature, endocranial components (e.g., brain, inner ear, and neurovascular structures), and other soft tissues (e.g., whole-body and life reconstructions). Digital techniques provide versatile tools for the reconstruction of soft tissues, but given the nature of fossil specimens, some limitations and uncertainties remain. Nevertheless, digital reconstructions can provide new information, in particular if interpreted in a phylogenetically grounded framework. Combined with other digital analytical techniques (e.g., finite element analysis [FEA], multibody dynamics analysis [MDA], and computational fluid dynamics [CFD]), soft-tissue reconstructions can be used to elucidate the paleobiology of extinct organisms and to test competing evolutionary hypotheses.

Relationships between energy expenditure and positive and negative mechanical work in repetitive lifting and lowering

1994 ◽  
Vol 77 (1) ◽  
pp. 420-426 ◽  
Author(s):  
M. P. De Looze ◽  
H. M. Toussaint ◽  
D. A. Commissaris ◽  
M. P. Jans ◽  
A. J. Sargeant
Keyword(s):  
Energy Cost ◽  
Weight Lifting ◽  
Mechanical Work ◽  
Metabolic Energy ◽  
Data Set ◽  
Negative Work ◽  
Repetitive Lifting ◽  
The Cost ◽  
Muscle Actions ◽  
Isometric Muscle

Determining the separate energy costs of the positive and negative mechanical work in repetitive lifting or lowering is quite complex, as a mixture of both work components will always be involved in the up- and downward motion of the lifter's body mass. In the current study, a new method was tested in which coefficients specifically related to the positive and negative work were estimated by multiple regression on a data set of weight-lifting and weight-lowering tasks. The energy cost was obtained from oxygen uptake measurements. The slopes of the regression lines for energy cost and mechanical work were steeper for positive than for negative work. The cost related to the negative work was approximately 0.3–0.5 times the cost of the positive work. This finding is well in line with data obtained directly from other isolated activities of either positive or negative work (e.g., ladder climbing vs. descending). However, the intercept values of the regression lines were not significantly different from zero or were even negative. This was most likely due to the metabolic energy not related to processes that yield mechanical work (e.g., isometric muscle actions) that was not constant among trials.

Mechanical work for step-to-step transitions is a major determinant of the metabolic cost of human walking

2002 ◽  
Vol 205 (23) ◽  
pp. 3717-3727 ◽  
Author(s):  
J. Maxwell Donelan ◽  
Rodger Kram ◽  
Arthur D. Kuo
Keyword(s):  
Metabolic Rate ◽  
Center Of Mass ◽  
Metabolic Cost ◽  
Step Length ◽  
Mechanical Work ◽  
Major Determinant ◽  
Fourth Power ◽  
Mass Motion ◽  
Step Frequency ◽  
Positive Work

SUMMARY In the single stance phase of walking, center of mass motion resembles that of an inverted pendulum. Theoretically, mechanical work is not necessary for producing the pendular motion, but work is needed to redirect the center of mass velocity from one pendular arc to the next during the transition between steps. A collision model predicts a rate of negative work proportional to the fourth power of step length. Positive work is required to restore the energy lost, potentially exacting a proportional metabolic cost. We tested these predictions with humans (N=9) walking over a range of step lengths(0.4-1.1 m) while keeping step frequency fixed at 1.8 Hz. We measured individual limb external mechanical work using force plates, and metabolic rate using indirect calorimetry. As predicted, average negative and positive external mechanical work rates increased with the fourth power of step length(from 1 W to 38 W; r2=0.96). Metabolic rate also increased with the fourth power of step length (from 7 W to 379 W; r2=0.95), and linearly with mechanical work rate. Mechanical work for step-to-step transitions, rather than pendular motion itself, appears to be a major determinant of the metabolic cost of walking.

scholarly journals Extra-osseous 99mTc methylene diphosphonate uptake detected enlargement of the knee joint in patient with polyarthritis

2017 ◽  
Vol 5 ◽  
pp. 2050313X1774182
Author(s):  
Maria Grazia Caprio ◽  
Mariarosaria Manganelli ◽  
Simona Limone ◽  
Massimiliano Sorbillo ◽  
Mario Quarantelli ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Soft Tissue ◽  
Bone Scintigraphy ◽  
Soft Tissues ◽  
Whole Body ◽  
Magnetic Resonance Imaging Scan ◽  
Resonance Imaging ◽  
Methylene Diphosphonate ◽  
Depth Analysis

Bone scintigraphy is a nuclear scanning test used to find abnormalities in the skeleton. Certain abnormal processes involving soft tissues can also cause skeletal accumulation of radiotracer during bone scintigraphy. We present a case of periarticular knee soft tissue 99mTc methylene diphosphonate uptake in a patient with asymmetric polyarthritis. A 33-year-old patient with asymmetric polyarthritis, skin lesions and joint pain underwent bone scintigraphy. Total body examination showed an extra-osseous uptake in periarticular soft tissue of knees joints. A detailed history checkup, physical examination and laboratory tests were carried out to understand the link between the extra-osseous uptake and the phosphonate binding in periarticular soft tissue. To improve the anatomical description of the soft tissue of the knees and to clarify the nature of the extra-skeletal 99mTc methylene diphosphonate uptake, magnetic resonance imaging scan was performed. 99mTc-labeled phosphonate binding has been reported in a number of extra-osseous conditions, but to our knowledge, there are a few cases showing bone tracer uptake in polyarthritis. In polyarthritic patients, whole-body bone scintigraphy were useful in examining the whole joints and detecting possible dubious extra-osseous uptake; in fact, it is able to select subjects who require further in-depth analysis, for example, magnetic resonance imaging.

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