Modeling the Efficiency of Movement: From Individual Muscles to Whole Organism

2009 ◽  
Author(s):  
Brian R. Umberger ◽  
Alexis D. Gidley
Keyword(s):  
Energy Consumption ◽  
Energy Input ◽  
Mechanical Energy ◽  
Human Movement ◽  
Metabolic Energy ◽  
Energy Output ◽  
Whole Body ◽  
Similar Data ◽  
Invasive Approach

In the context of human movement, efficiency is defined as the ratio of mechanical energy output (work) to metabolic energy input [1,2]. It is straightforward to determine whole-body efficiency in a task such as pedaling a bicycle ergometer. In this case, work is computed from the ergometer load and pedaling cadence, and metabolic energy is determined from pulmonary gas exchange. It is also relatively straightforward to determine the efficiency of contraction in isolated muscle preparations, where the work done is easily measured, and energy input can be inferred from heat production or oxygen consumption. However, our understanding of the efficiency of muscle function during locomotion, and how this contributes to organismal efficiency, is incomplete [1]. The ability to determine efficiency of individual muscles as they perform work in vivo would greatly enhance our understating in this area. Experimental measurement of both work and metabolic energy consumption in muscles during dynamic activities is currently limited to isolated applications in non-human animals [3]. Similar data could be obtained using computational modeling and simulation techniques, provided that estimates could be obtained for both muscle work and muscle metabolic energy consumption. This non-invasive approach would open the door to investigations in humans as well as other species. Therefore, the primary purpose of this study was to determine efficiency at both the organismal and muscular levels for bicycle pedaling, using a musculoskeletal modeling approach. A secondary purpose was to identify factors that account for between-muscle differences in efficiency.

scholarly journals Energy Efficient Microwave Irradiation of Sago Bark Waste (SBW) for Bioethanol Production

2013 ◽  
Vol 701 ◽  
pp. 249-253 ◽  
Author(s):  
T. Saravana Kannan ◽  
A.S. Ahmed ◽  
Ani Farid Nasir
Keyword(s):  
Energy Consumption ◽  
Microwave Irradiation ◽  
Energy Input ◽  
Energy Savings ◽  
Ethanol Yield ◽  
Energy Output ◽  
Bioethanol Production ◽  
Microwave Pretreatment ◽  
Theoretical Yield ◽  
Sago Bark

The energy efficiency of microwave irradiation for bioethanol production from sago bark waste (SBW) was studied. The maximum sugar yield of 62.6 % was reached at the biomass loading 20% (w/w). The high ethanol yield of 60.2% theoretical yield, ethanol concentration 30.67 g/l was achieved by diluted sulfuric acid supported microwave irradiation with 40% (w/w) biomass loading at 60 h fermentation. The energy consumption of microwave irradiation to produce 1 g sugar and 1 g ethanol was calculated separately. The lowest energy consumption was noticed while biomass loading and energy input were fixed at 40 % (w/w) and 33 kJ (1100 W for 30 s) respectively, and it is amounted to 1.27 and 1.76 kJ to produce 1 g of sugar after enzymatic hydrolysis and 1 g ethanol after fermentation, individually. Usually, 1 g ethanol can produce approximately 27 kJ of energy, and therefore, the energy input for the microwave pretreatment was only 7% of the energy output. The microwave irradiation technique established for SBW to produce ethanol succeeded in 80% energy savings for producing 1 g ethanol compared to rape straw by microwave pretreatment previously reported.

scholarly journals PVDF-TrFE Electroactive Polymer Mechanical-to-Electrical Energy Harvesting Experimental Bimorph Structure

MRS Advances ◽  
2017 ◽  
Vol 2 (56) ◽  
pp. 3441-3446 ◽  
Author(s):  
William G. Kaval ◽  
Robert A. Lake ◽  
Ronald A. Coutu
Keyword(s):  
Energy Harvesting ◽  
Vibrational Energy ◽  
Mechanical Energy ◽  
Low Frequency ◽  
Human Movement ◽  
Electrical Energy ◽  
Mechanical Analysis ◽  
Electroactive Polymer ◽  
Energy Output ◽  
Piezoelectric Energy

ABSTRACTResearch of electrostrictive polymers has generated new opportunities for harvesting energy from the surrounding environment and converting it into usable electrical energy. Electroactive polymer (EAP) research is one of the new opportunities for harvesting energy from the natural environment and converting it into usable electrical energy. Piezoelectric ceramic based energy harvesting devices tend to be unsuitable for low-frequency mechanical excitations such as human movement. Organic polymers are typically softer and more flexible therefore translated electrical energy output is considerably higher under the same mechanical force. In addition, cantilever geometry is one of the most used structures in piezoelectric energy harvesters, especially for mechanical energy harvesting from vibrations. In order to further lower the resonance frequency of the cantilever microstructure, a proof mass can be attached to the free end of the cantilever. Mechanical analysis of an experimental bimorph structure was provided and led to key design rules for post-processing steps to control the performance of the energy harvester. In this work, methods of materials processing and the mechanical to electrical conversion of vibrational energy into usable energy were investigated. Materials such as polyvinyledenedifluoridetetra-fluoroethylene P(VDF-TrFE) copolymer films (1um thick or less) were evaluated and presented a large relative permittivity and greater piezoelectric β-phase without stretching. Further investigations will be used to identify suitable micro-electromechanical systems (MEMs) structures given specific types of low-frequency mechanical excitations (10-100Hz).

scholarly journals Does Elastic Energy Enhance Work and Efficiency in the Stretch-Shortening Cycle?

1997 ◽  
Vol 13 (4) ◽  
pp. 389-415 ◽  
Author(s):  
Gerrit Jan van Ingen Schenau ◽  
Maarten F. Bobbert ◽  
Arnold de Haan
Keyword(s):  
Elastic Energy ◽  
Mechanical Energy ◽  
Mechanical Efficiency ◽  
The Body ◽  
Metabolic Energy ◽  
Whole Body ◽  
Levels Of Organization ◽  
Cyclic Movements ◽  
Stretch Shortening Cycle ◽  
Different Levels

This target article addresses the role of storage and reutilization of elastic energy in stretch-shortening cycles. It is argued that for discrete movements such as the vertical jump, elastic energy does not explain the work enhancement due to the prestretch. This enhancement seems to occur because the prestretch allows muscles to develop a high level of active state and force before starting to shorten. For cyclic movements in which stretch-shortening cycles occur repetitively, some authors have claimed that elastic energy enhances mechanical efficiency. In the current article it is demonstrated that this claim is often based on disputable concepts such as the efficiency of positive work or absolute work, and it is argued that elastic energy cannot affect mechanical efficiency simply because this energy is not related to the conversion of metabolic energy into mechanical energy. A comparison of work and efficiency measures obtained at different levels of organization reveals that there is in fact no decisive evidence to either support or reject the claim that the stretch-shortening cycle enhances muscle efficiency. These explorations lead to the conclusion that the body of knowledge about the mechanics and energetics of the stretch-shortening cycle is in fact quite lean. A major challenge is to bridge the gap between knowledge obtained at different levels of organization, with the ultimate purpose of understanding how the intrinsic properties of muscles manifest themselves underin-vivo-like conditions and how they are exploited in whole-body activities such as running. To achieve this purpose, a close cooperation is required between muscle physiologists and human movement scientists performing inverse and forward dynamic simulation studies of whole-body exercises.

scholarly journals MODELING AND SIMULATION OF SKELETAL MUSCLE BASED ON METABOLISM PHYSIOLOGY

2020 ◽  
Vol 20 (09) ◽  
pp. 2040018
Author(s):  
MONAN WANG ◽  
JIALIN HAN ◽  
QIYOU YANG
Keyword(s):  
Skeletal Muscle ◽  
Energy Metabolism ◽  
Calcium Ion ◽  
Energy Systems ◽  
Metabolic Energy ◽  
Ion Concentration ◽  
Whole Body ◽  
Muscle Energy Metabolism ◽  
Calcium Ion Transport

Skeletal muscle energy metabolism plays a very important role in controlling movement of the whole body and has important theoretical guidance for making exercise training plans and losing weight. In this paper, we developed a mathematical model of skeletal muscle excitation–contraction pathway based on the energy metabolism that links excitation to contraction to explore the effects of different metabolic energy systems on calcium ion changes and the force during skeletal muscle contraction. In this paper, a membrane potential model, a calcium cycle model, a cross-bridge dynamics model and an energy metabolism model were established. Finally, the physiological phenomenon of calcium ion transport and calcium ion concentration change of the sarcoplasm was simulated. The results show that the phosphagen system has the fastest metabolic rate and the phosphagen system has the largest impact on the explosive power of skeletal muscle exercise. The specific characteristics of the three metabolic energy systems supporting skeletal muscle movement in vivo were also analyzed in detail.

scholarly journals Wpływ emisji energii z terenów zurbanizowanych i szlaków komunikacyjnych na zmiany w rozwoju ekosystemów w ich otoczeniu

2012 ◽  
Vol 10 (2) ◽  
pp. 73-85
Author(s):  
Urszula Kaźmierczak ◽  
Andrzej Kulczycki
Keyword(s):  
Energy Consumption ◽  
Statistical Analysis ◽  
Human Health ◽  
Chemical Reactions ◽  
Environmental Effects ◽  
Acoustic Waves ◽  
Urban Areas ◽  
Small Area ◽  
Energy Input ◽  
Mechanical Energy

This article aims to draw attention to the hitherto unexplored and scarcely noticed the problem of the effects of the consumption of increasing amounts of energy to human health and ecosystems exposed to emissions processed in the phase of energy consumption. Ever-increasing amounts of energy are consumed in relatively small urban areas, in communication routes, and in airport areas. As far as Poland is concerned, these areas represent less than 10% of the country. For such a small area the energy consumed is converted to other forms of energy, much of which is emitted into the environment. These emissions primarily include heat and various forms of mechanical energy, mainly that of acoustic waves. It studies the effect of noise on the health of people living in the vicinity of highways, as well as studies of ecosystems in the surrounding routes. There is still no explanation for the reasons for this phenomenon, as research in this area has been mainly carried out at the level of statistical analysis. The article has pointed out the possible causes of this phenomenon. The new theory of catalysis demonstrates the effect of mechanical energy input on the direction and rate of chemical reactions. This effect can also be significant in the case of biochemical reactions. Finally, the paper points out the need and direction of research, conducted at various levels, to determine and explain the environmental effects of increasing energy consumption, other than the greenhouse one.

scholarly journals Habitual foot strike pattern does not affect simulated Triceps Surae muscle metabolic energy consumption during running

2019 ◽  
Author(s):  
Wannes Swinnen ◽  
Wouter Hoogkamer ◽  
Friedl De Groote ◽  
Benedicte Vanwanseele
Keyword(s):  
Energy Consumption ◽  
Triceps Surae ◽  
Metabolic Energy ◽  
Whole Body ◽  
Optimization Approach ◽  
Joint Work ◽  
Energy Models ◽  
Triceps Surae Muscle ◽  
Direct Measurements ◽  
Foot Strike

AbstractFoot strike pattern affects ankle joint work and Triceps Surae muscle-tendon dynamics during running. Whether these changes in muscle-tendon dynamics also affect Triceps Surae muscle energy consumption is still unknown. In addition, as the Triceps Surae muscle accounts for a substantial amount of the whole body metabolic energy consumption, changes in Triceps Surae energy consumption may affect whole body metabolic energy consumption. However, direct measurements of muscle metabolic energy consumption during dynamic movements is hard. Model-based approaches can be used to estimate individual muscle and whole body metabolic energy consumption based on Hill type muscle models. In this study, we use an integrated experimental and dynamic optimization approach to compute muscle states (muscle forces, lengths, velocities, excitations and activations) of 10 habitual mid-/forefoot striking and 9 habitual rearfoot striking runners while running at 10 and 14 km/h. The Achilles tendon stiffness of the musculoskeletal model was adapted to fit experimental ultrasound data of the Gastrocnemius medialis muscle during ground contact. Next, we calculated Triceps Surae muscle and whole body metabolic energy consumption using four different metabolic energy models provided in literature. Neither Triceps Surae metabolic energy consumption (p > 0.35), nor whole body metabolic energy consumption (p > 0.14) was different between foot strike patterns, regardless of the energy model used or running speed tested. Our results provide new evidence that mid-/forefoot and rearfoot strike pattern are metabolically equivalent.

Use of Toxicokinetics in Risk Assessment Based on In Vitro Data

1993 ◽  
Vol 21 (2) ◽  
pp. 173-180
Author(s):  
Gunnar Johanson
Keyword(s):  
Risk Assessment ◽  
Whole Body ◽  
External Exposure ◽  
Target Dose ◽  
Toxic Response ◽  
Route Of Exposure ◽  
Vitro Data ◽  
In Vitro Data

This presentation addresses some aspects of the methodology, advantages and problems associated with toxicokinetic modelling based on in vitro data. By using toxicokinetic models, particularly physiologically-based ones, it is possible, in principle, to describe whole body toxicokinetics, target doses and toxic effects from in vitro data. Modelling can be divided into three major steps: 1) to relate external exposure (applied dose) of xenobiotic to target dose; 2) to establish the relationship between target dose and effect (in vitro data, e.g. metabolism in microsomes, partitioning in tissue homogenates, and toxicity in cell cultures, are useful in both steps); and 3) to relate external exposure to toxic effect by combining the first two steps. Extrapolations from in vitro to in vivo, between animal and man, and between high and low doses, can easily be carried out by toxicokinetic simulations. In addition, several factors that may affect the toxic response by changing the target dose, such as route of exposure and physical activity, can be studied. New insights concerning the processes involved in toxicity often emerge during the design, refinement and validation of the model. The modelling approach is illustrated by two examples: 1) the carcinogenicity of 1,3-butadiene; and 2) the haematotoxicity of 2-butoxyethanol. Toxicokinetic modelling is an important tool in toxicological risk assessment based on in vitro data. Many factors, some of which can, and should be, studied in vitro, are involved in the expression of toxicity. Successful modelling depends on the identification and quantification of these factors.

scholarly journals Adipocyte PHLPP2 inhibition prevents obesity-induced fatty liver

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
KyeongJin Kim ◽  
Jin Ku Kang ◽  
Young Hoon Jung ◽  
Sang Bae Lee ◽  
Raffaela Rametta ◽  
...  
Keyword(s):  
Fatty Liver ◽  
Whole Body ◽  
Acid Oxidation ◽  
Chow Diet ◽  
Peroxisome Proliferator ◽  
Obese Mice ◽  
Ph Domain ◽  
Peroxisome Proliferator Activated Receptor

AbstractIncreased adiposity confers risk for systemic insulin resistance and type 2 diabetes (T2D), but mechanisms underlying this pathogenic inter-organ crosstalk are incompletely understood. We find PHLPP2 (PH domain and leucine rich repeat protein phosphatase 2), recently identified as the Akt Ser473 phosphatase, to be increased in adipocytes from obese mice. To identify the functional consequence of increased adipocyte PHLPP2 in obese mice, we generated adipocyte-specific PHLPP2 knockout (A-PHLPP2) mice. A-PHLPP2 mice show normal adiposity and glucose metabolism when fed a normal chow diet, but reduced adiposity and improved whole-body glucose tolerance as compared to Cre- controls with high-fat diet (HFD) feeding. Notably, HFD-fed A-PHLPP2 mice show increased HSL phosphorylation, leading to increased lipolysis in vitro and in vivo. Mobilized adipocyte fatty acids are oxidized, leading to increased peroxisome proliferator-activated receptor alpha (PPARα)-dependent adiponectin secretion, which in turn increases hepatic fatty acid oxidation to ameliorate obesity-induced fatty liver. Consistently, adipose PHLPP2 expression is negatively correlated with serum adiponectin levels in obese humans. Overall, these data implicate an adipocyte PHLPP2-HSL-PPARα signaling axis to regulate systemic glucose and lipid homeostasis, and suggest that excess adipocyte PHLPP2 explains decreased adiponectin secretion and downstream metabolic consequence in obesity.

scholarly journals Reducing the metabolic energy of walking and running using an unpowered hip exoskeleton

2021 ◽  
Vol 18 (1) ◽  
Author(s):  
Tiancheng Zhou ◽  
Caihua Xiong ◽  
Juanjuan Zhang ◽  
Di Hu ◽  
Wenbin Chen ◽  
...  
Keyword(s):  
Energy Consumption ◽  
Design Method ◽  
Metabolic Cost ◽  
Metabolic Energy ◽  
Spring Stiffness ◽  
Spatiotemporal Parameters ◽  
The Common ◽  
Hip Flexion ◽  
Optimal Stiffness ◽  
Insight Into

Abstract Background Walking and running are the most common means of locomotion in human daily life. People have made advances in developing separate exoskeletons to reduce the metabolic rate of walking or running. However, the combined requirements of overcoming the fundamental biomechanical differences between the two gaits and minimizing the metabolic penalty of the exoskeleton mass make it challenging to develop an exoskeleton that can reduce the metabolic energy during both gaits. Here we show that the metabolic energy of both walking and running can be reduced by regulating the metabolic energy of hip flexion during the common energy consumption period of the two gaits using an unpowered hip exoskeleton. Methods We analyzed the metabolic rates, muscle activities and spatiotemporal parameters of 9 healthy subjects (mean ± s.t.d; 24.9 ± 3.7 years, 66.9 ± 8.7 kg, 1.76 ± 0.05 m) walking on a treadmill at a speed of 1.5 m s−1 and running at a speed of 2.5 m s−1 with different spring stiffnesses. After obtaining the optimal spring stiffness, we recruited the participants to walk and run with the assistance from a spring with optimal stiffness at different speeds to demonstrate the generality of the proposed approach. Results We found that the common optimal exoskeleton spring stiffness for walking and running was 83 Nm Rad−1, corresponding to 7.2% ± 1.2% (mean ± s.e.m, paired t-test p < 0.01) and 6.8% ± 1.0% (p < 0.01) metabolic reductions compared to walking and running without exoskeleton. The metabolic energy within the tested speed range can be reduced with the assistance except for low-speed walking (1.0 m s−1). Participants showed different changes in muscle activities with the assistance of the proposed exoskeleton. Conclusions This paper first demonstrates that the metabolic cost of walking and running can be reduced using an unpowered hip exoskeleton to regulate the metabolic energy of hip flexion. The design method based on analyzing the common energy consumption characteristics between gaits may inspire future exoskeletons that assist multiple gaits. The results of different changes in muscle activities provide new insight into human response to the same assistive principle for different gaits (walking and running).

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