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

2013 ◽  
Vol 115 (5) ◽  
pp. 579-585 ◽  
Author(s):  
Dominic James Farris ◽  
Benjamin D. Robertson ◽  
Gregory S. Sawicki
Keyword(s):  
Inverse Dynamics ◽  
Average Rate ◽  
Plantar Flexion ◽  
Metabolic Cost ◽  
Whole Body ◽  
Negative Consequences ◽  
Metabolic Power ◽  
Force Peak ◽  
Inverse Dynamics Analysis

Inspired by elastic energy storage and return in tendons of human leg muscle-tendon units (MTU), exoskeletons often place a spring in parallel with an MTU to assist the MTU. However, this might perturb the normally efficient MTU mechanics and actually increase active muscle mechanical work. This study tested the effects of elastic parallel assistance on MTU mechanics. Participants hopped with and without spring-loaded ankle exoskeletons that assisted plantar flexion. An inverse dynamics analysis, combined with in vivo ultrasound imaging of soleus fascicles and surface electromyography, was used to determine muscle-tendon mechanics and activations. Whole body net metabolic power was obtained from indirect calorimetry. When hopping with spring-loaded exoskeletons, soleus activation was reduced (30–70%) and so was the magnitude of soleus force (peak force reduced by 30%) and the average rate of soleus force generation (by 50%). Although forces were lower, average positive fascicle power remained unchanged, owing to increased fascicle excursion (+4–5 mm). Net metabolic power was reduced with exoskeleton assistance (19%). These 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.

ANALYSIS OF THE EFFECTS OF SPINE STABILIZATION EXERCISES USING A WHOLE BODY TILT DEVICE ON MUSCLE FORCES IN THE SPINE

2014 ◽  
Vol 14 (06) ◽  
pp. 1440003
Author(s):  
KAP-SOO HAN ◽  
CHANG HO YU ◽  
MYOUNG-HWAN KO ◽  
TAE KYU KWON
Keyword(s):  
Inverse Dynamics ◽  
The Elderly ◽  
Body Tilt ◽  
Whole Body ◽  
Muscle Forces ◽  
Activation Patterns ◽  
Muscle Strengthening ◽  
Spine Stabilization ◽  
Inverse Dynamics Analysis ◽  
The Right

The objective of the study was to investigate the effects of 3D stabilization exercises using a whole body tilt device on forces in the trunk, such as individual muscle forces and activation patterns, maximum muscle activities and spine loads. For this sake, a musculoskeletal (MS) model of the whole body was developed, and an inverse dynamics analysis was performed to predict the forces on the spine. An EMG measurement experiment was conducted to validate the muscle forces and activation patterns. The MS model was rotated and tilted in eight different directions: anterior (A), posterior (P), anterior right (AR), posterior right (PR), anterior left (AL), posterior left (PL), right (R) and left (L), replicating the directions of the 3D spine balance exercise device, as performed in the experiment. The anterior directions of the tilt primarily induced the activation of long and superficial back muscles and the posterior directions activated the front muscles. However, deep muscles, such as short muscles and multifidi, were activated in all directions of the tilt. The resultant joint forces in the right and left directions of the tilt were the least among the directions, but higher muscle activations and more diverse muscle recruitments than other positions were observed. Therefore, these directions of tilt may be suitable for the elderly and rehabilitation patients who require muscle strengthening with less spinal loads. In the present investigation, it was shown that 3D stabilization exercises could provide considerable muscle exercise effects with a minimum perturbation of structure. The results of this study can be used to provide safety guidelines for muscle exercises using this type of tilting device. Therefore, the proposed direction of tilt can be used to strengthen targeted muscles, depending on the patients' muscular condition.

Gait Analysis Using Multibody Simulation Tools and Inverse Dynamics Procedures

2005 ◽  
Author(s):  
Miguel Silva ◽  
Jorge Ambro´sio
Keyword(s):  
Gait Analysis ◽  
Inverse Dynamics ◽  
Three Dimensional ◽  
Biomechanical Model ◽  
Whole Body ◽  
Dynamics Analysis ◽  
Natural Coordinates ◽  
Kinematic Constraints ◽  
Biomechanical Models ◽  
Inverse Dynamics Analysis

The use of inverse dynamics methodologies for the evaluation of intersegmental reaction forces and the moments-of-force at the anatomical joints, in the framework of gait analysis, not only requires that appropriate biomechanical models are used but also that kinematic and kinetic data sets are available. This paper discusses the quality of the results of the inverse dynamics analysis with respect to the filtering procedures used and the kinematic consistency of the position, velocity and acceleration data. A three-dimensional whole body response biomechanical model based on a multibody formulation with natural coordinates is used. The model has 16 anatomical segments that are described using 33 rigid bodies in a total of 44 degrees-of-freedom. In biomechanical applications, one of the advantages of the current formulation is that the set of anatomical points used to reconstruct the spatial motion of the subject is also used to construct the set of natural coordinates that describe the biomechanical model itself. Based on the images collected by four synchronized video cameras, the three-dimensional trajectories of the anatomical points are reconstructed using standard photogrammetry techniques and Direct Linear Transformations. The trajectories obtained are then filtered in order to reduce the noise levels introduced during the reconstruction procedure using 2nd order Butterworth low-pass filters with properly chosen cut-off frequencies. The filtered data is used in the inverse dynamics analysis either directly or after being modified in order to ensure its consistency with the biomechanical model’s kinematic constraints. It is also shown that the use of velocities and accelerations consistent with the kinematic constraints or those obtained through the time derivatives of the spline interpolation curves of the reconstructed trajectories lead to similar results.

scholarly journals ANALYSIS OF MUSCLE STRENGTH EFFECTS ON EXERCISE PERFORMANCE USING DYNAMIC STABILIZATION EXERCISE DEVICE

2020 ◽  
Vol 20 (09) ◽  
pp. 2040004
Author(s):  
KAP-SOO HAN ◽  
SEUNG-ROK KANG ◽  
TAE-KYU KWON
Keyword(s):  
Muscle Strength ◽  
Muscle Activation ◽  
Muscle Force ◽  
Inverse Dynamics ◽  
Body Tilt ◽  
Whole Body ◽  
Stabilization Exercise ◽  
Spine Stabilization ◽  
Exercise Effect ◽  
Inverse Dynamics Analysis

Muscle strength may vary depending on the pathological issues and static life habits. These conditions lead to abnormal spinal loads and change muscle strength as well as activation patterns, thereby causing spinal disorders. In this study, the effects of muscle strength on the spine stabilization exercise were analyzed using a whole-body tilt device. Musculoskeletal modeling was performed and the results were validated through a comparison with the electromyography (EMG) analysis results. Based on the validated basic model, modeling was performed for the whole-body tilt device. To examine the exercise effect and muscle activation while the maximum muscle force capacity (MFC) was varied from 30[Formula: see text]N/cm2 to 60[Formula: see text]N/cm2 and 90[Formula: see text]N/cm2, the muscle force was predicted through inverse dynamics analysis. When MFC was 30[Formula: see text]N/cm2, the posterior direction of the tilt could not be analyzed (no solution found). When MFC was 60[Formula: see text]N/cm2, it could be analyzed, but the muscle force was predicted to be higher compared to when MFC was 90[Formula: see text]N/cm2. It was confirmed that muscle strength is a very important element for maintaining postural activities and performing exercise. Therefore, for rehabilitation patients and elderly people with weak muscle strength, hard or extreme exercise may cause musculoskeletal injuries.

In vivo behavior of the human soleus muscle with increasing walking and running speeds

2015 ◽  
Vol 118 (10) ◽  
pp. 1266-1275 ◽  
Author(s):  
Adrian Lai ◽  
Glen A. Lichtwark ◽  
Anthony G. Schache ◽  
Yi-Chung Lin ◽  
Nicholas A. T. Brown ◽  
...  
Keyword(s):  
Steady State ◽  
Inverse Dynamics ◽  
Length Change ◽  
Shortening Velocity ◽  
Transition Speed ◽  
Muscle Fascicle ◽  
Muscle Fascicles ◽  
Inverse Dynamics Analysis ◽  
Preferred Transition Speed

The interaction between the muscle fascicle and tendon components of the human soleus (SO) muscle influences the capacity of the muscle to generate force and mechanical work during walking and running. In the present study, ultrasound-based measurements of in vivo SO muscle fascicle behavior were combined with an inverse dynamics analysis to investigate the interaction between the muscle fascicle and tendon components over a broad range of steady-state walking and running speeds: slow-paced walking (0.7 m/s) through to moderate-paced running (5.0 m/s). Irrespective of a change in locomotion mode (i.e., walking vs. running) or an increase in steady-state speed, SO muscle fascicles were found to exhibit minimal shortening compared with the muscle-tendon unit (MTU) throughout stance. During walking and running, the muscle fascicles contributed only 35 and 20% of the overall MTU length change and shortening velocity, respectively. Greater levels of muscle activity resulted in increasingly shorter SO muscle fascicles as locomotion speed increased, both of which facilitated greater tendon stretch and recoil. Thus the elastic tendon contributed the majority of the MTU length change during walking and running. When transitioning from walking to running near the preferred transition speed (2.0 m/s), greater, more economical ankle torque development is likely explained by the SO muscle fascicles shortening more slowly and operating on a more favorable portion (i.e., closer to the plateau) of the force-length curve.

Simulating Instrumented Knee Implant Forces With a Simplified Computational Model

2013 ◽  
Author(s):  
Jacobus H. Müller
Keyword(s):  
Computational Model ◽  
Inverse Analysis ◽  
Inverse Dynamics ◽  
Musculoskeletal Model ◽  
Grand Challenge ◽  
Dynamics Analysis ◽  
Muscle Dynamics ◽  
Target Values ◽  
Inverse Dynamics Analysis

A simplified computational model is presented with which axial knee implant forces can be estimated. The dataset provided in the IV Grand Challenge to Predict in-vivo Knee Loads [1] is used to assemble a musculoskeletal model, and perform an inverse dynamics analysis. The joint and muscle dynamics recorded during the inverse analysis is then used as target values during a forward dynamics analysis to compute the axial tibiofemoral load.

scholarly journals Coupled exoskeleton assistance simplifies control and maintains metabolic benefits: a simulation study

2021 ◽  
Author(s):  
Nicholas August Bianco ◽  
Patrick W. Franks ◽  
Jennifer Lee Hicks ◽  
Scott Lee Delp
Keyword(s):  
Control Strategies ◽  
Metabolic Cost ◽  
Torque Control ◽  
Whole Body ◽  
Negative Consequences ◽  
Lower Limb Exoskeleton ◽  
Human Experiments ◽  
Optimizing Control ◽  
And Control ◽  
Exoskeleton Device

Assistive exoskeletons can reduce the metabolic cost of walking, and recent advances in exoskeleton device design and control have resulted in large metabolic savings. Most exoskeleton devices provide assistance at either the ankle or hip. Exoskeletons that assist multiple joints have the potential to provide greater metabolic savings, but can require many actuators and complicated controllers, making it difficult to design effective assistance. Coupled assistance, when two or more joints are assisted using one actuator or control signal, could reduce control dimensionality while retaining metabolic benefits. However, it is unknown which combinations of assisted joints are most promising and if there are negative consequences associated with coupled assistance. Since designing assistance with human experiments is expensive and time-consuming, we used musculoskeletal simulation to evaluate metabolic savings from multi-joint assistance and identify promising joint combinations. We generated 2D muscle-driven simulations of walking while simultaneously optimizing control strategies for simulated lower-limb exoskeleton assistive devices to minimize metabolic cost. Each device provided assistance either at a single joint or at multiple joints using massless, ideal actuators. To assess if control could be simplified for multi-joint exoskeletons, we simulated different control strategies in which the torque provided at each joint was either controlled independently or coupled between joints. We compared the predicted optimal torque profiles and changes in muscle and whole-body metabolic power consumption across the single joint and multi-joint assistance strategies. We found multi-joint devices--whether independent or coupled--provided 50% greater metabolic savings than single joint devices. The coupled multi-joint devices were able to achieve most of the metabolic savings produced by independently-controlled multi-joint devices. Our results indicate that device designers could simplify multi-joint exoskeleton designs by reducing the number of torque control parameters through coupling, while still maintaining large reductions in metabolic cost.

scholarly journals Force Generation on the Hallux Is More Affected by the Ankle Joint Angle than the Lesser Toes: An In Vivo Human Study

Biology ◽  
2021 ◽  
Vol 10 (1) ◽  
pp. 48
Author(s):  
Junya Saeki ◽  
Soichiro Iwanuma ◽  
Suguru Torii
Keyword(s):  
Repeated Measures ◽  
Joint Angle ◽  
Plantar Flexion ◽  
Human Study ◽  
Force Generation ◽  
Functional Difference ◽  
Multiple Comparison Test ◽  
The Difference ◽  
Metatarsophalangeal Joints

The structure of the first toe is independent of that of the other toes, while the functional difference remains unclear. The purpose of this study was to investigate the difference in the force generation characteristics between the plantar-flexion of the first and second–fifth metatarsophalangeal joints (MTPJs) by comparing the maximal voluntary plantar-flexion torques (MVC torque) at different MTPJs and ankle positions. The MVC torques of the first and second–fifth MTPJs were measured at 0°, 15°, 30°, and 45° dorsiflexed positions of the MTPJs, and at 20° plantar-flexed, neutral, and 20° dorsiflexed positions of the ankle. Two-way repeated measures analyses of variance with Holm’s multiple comparison test (MTPJ position × ankle position) were performed. When the MTPJ was dorsiflexed at 0°, 15°, and 30°, the MVC torque of the first MTPJ when the ankle was dorsiflexed at 20° was higher than that when the ankle was plantar-flexed at 20°. However, the ankle position had no significant effect on the MVC torque of the second–fifth MTPJ. Thus, the MVC torque of the first MTPJ was more affected by the ankle position than the second–fifth MTPJs.

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.

The Hemostatic Effect of 51Cr-Labelled Platelets

1975 ◽  
Author(s):  
J. Björnson ◽  
I. Aursnes
Keyword(s):  
Whole Body ◽  
Platelet Concentrates ◽  
Platelet Aggregability ◽  
Hemostatic Effect ◽  
Normal Platelet ◽  
Labelling Procedure

In the interpretation of data obtained with 51Cr-labelled platelets it is vital to know whether they are functionally normal. Although survival of 51Cr-labelled platelets in vivo appears to be normal, platelet aggregability- has recently been shown to be reduced after the labelling procedure (Björnson, J., Sc and. J. Haemat. 13, 252–259).The aim of the present study was to examine the hemostatic effect of labelled platelets. Rabbits were made thrombocytopenic (< 35,000/μ1) by whole body irradiation. Bleeding times were recorded after standardized cuts on the inner side of the ear, a method showing an acceptable reproducibility (< 3 min in normals). The animals were then transfused with labelled platelet concentrates, increasing the platelet levels to about 200,000/μ) blood. Bleeding times of more than 15 min before transfusion were almost normalized 1 and 4 hours after transfusion. In controls transfusion of PRP led to similar shortening of bleeing time.It is concluded that platelets subjected to the 51Cr-labelling procedure to a large extent retain their hemostatic ability.

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