Design and Evaluation of a Proportional Myoelectric Controller for Hip Exoskeletons During Walking

2018 ◽  
Author(s):  
Hsiang Hsu ◽  
Inseung Kang ◽  
Aaron J. Young
Keyword(s):  
Metabolic Rate ◽  
Sagittal Plane ◽  
Metabolic Cost ◽  
Emg Activity ◽  
Neural Controller ◽  
Output Torque ◽  
Gait Phase ◽  
High Level ◽  
Series Elastic Actuators ◽  
Metabolic Reduction

The purpose of this study was to explore the effectiveness of a neural controller for a single-joint bilateral hip exoskeleton. The device provides mechanical torque in the sagittal plane and uses series elastic actuators for feedback control. The system consists of three control layers: (1) a high-level controller that estimates the current gait phase, (2) a mid-level controller that converts the electromyography (EMG) signals to desired exoskeleton torques, and (3) a low-level controller that ensures the output torque matches the commanded torque. To evaluate the effectiveness of the proportional EMG controller, one able-body subject walked with the exoskeleton under 3 assistance conditions: (1) a baseline proportional gain condition (× G), (2) a double proportional gain condition (× 2G) for faster scaling, and (3) an on/off set value torque assistance (SV). The third condition provides the same net mechanical power as the baseline (× G) condition to compare whether proportional scaling of the hip torque was significant. The subject’s hip-joint kinematics, metabolic rate, and muscle activities were collected as outcome measurements. In summary, the EMG controller could generate seamless torque to the user with a response time of 80 ms. The × 2G condition resulted in a 23.3% EMG activity reduction while SV condition reduced the metabolic rate by 8.1%. Interestingly, the largest EMG reduction condition (× 2G) did not result in largest metabolic reduction (SV). Our preliminary findings suggest that the proportional scaling of the hip torque may not be the most important parameter to minimize metabolic cost.

scholarly journals Energy cost and muscular activity required for propulsion during walking

2003 ◽  
Vol 94 (5) ◽  
pp. 1766-1772 ◽  
Author(s):  
Jinger S. Gottschall ◽  
Rodger Kram
Keyword(s):  
Body Weight ◽  
Muscular Activity ◽  
Metabolic Cost ◽  
Medial Gastrocnemius ◽  
Emg Activity ◽  
Horizontal Force ◽  
Normal Walking ◽  
The Mean ◽  
The Cost ◽  
Muscle Actions

We reasoned that with an optimal aiding horizontal force, the reduction in metabolic rate would reflect the cost of generating propulsive forces during normal walking. Furthermore, the reductions in ankle extensor electromyographic (EMG) activity would indicate the propulsive muscle actions. We applied horizontal forces at the waist, ranging from 15% body weight aiding to 15% body weight impeding, while subjects walked at 1.25 m/s. With an aiding horizontal force of 10% body weight, 1) the net metabolic cost of walking decreased to a minimum of 53% of normal walking, 2) the mean EMG of the medial gastrocnemius (MG) during the propulsive phase decreased to 59% of the normal walking magnitude, and yet 3) the mean EMG of the soleus (Sol) did not decrease significantly. Our data indicate that generating horizontal propulsive forces constitutes nearly half of the metabolic cost of normal walking. Additionally, it appears that the MG plays an important role in forward propulsion, whereas the Sol does not.

Broad oxygen tolerance in the nematode Caenorhabditis elegans

2000 ◽  
Vol 203 (16) ◽  
pp. 2467-2478 ◽  
Author(s):  
W.A. Van Voorhies ◽  
S. Ward
Keyword(s):  
Caenorhabditis Elegans ◽  
Metabolic Rate ◽  
Developmental Stages ◽  
Small Body ◽  
Metabolic Cost ◽  
Soil Nematode ◽  
Nematode Caenorhabditis Elegans ◽  
Oxygen Levels ◽  
C Elegans ◽  
Short Period

This study examined the effects of oxygen tensions ranging from 0 to 90 kPa on the metabolic rate (rate of carbon dioxide production), movement and survivorship of the free-living soil nematode Caenorhabditis elegans. C. elegans requires oxygen to develop and survive. However, it can maintain a normal metabolic rate at oxygen levels of 3.6 kPa and has near-normal metabolic rates at oxygen levels as low as 2 kPa. The ability to withstand low ambient oxygen levels appears to be a consequence of the small body size of C. elegans, which allows diffusion to supply oxygen readily to the cells without requiring any specialized respiratory or metabolic adaptations. Thus, the small size of this organism pre-adapts C. elegans to living in soil environments that commonly become hypoxic. Movement in C. elegans appears to have a relatively minor metabolic cost. Several developmental stages of C. elegans were able to withstand up to 24 h of anoxia without major mortality. Longer periods of anoxia significantly increased mortality, particularly for eggs. Remarkably, long-term exposure to 100 % oxygen had no effect on the metabolic rate of C. elegans, and populations were able to survive for a least 50 generations in 100 % (90 kPa) oxygen. Such hyperoxic conditions are fatal to most organisms within a short period.

New Predictive Resting Metabolic Rate Equations for High-Level Athletes

2021 ◽  
Vol Publish Ahead of Print ◽  
Author(s):  
Raul Freire ◽  
Glauber Pereira ◽  
Juan MA Alcantara ◽  
Ruan Santos ◽  
Matheus Hausen ◽  
...  
Keyword(s):  
Metabolic Rate ◽  
Resting Metabolic Rate ◽  
Rate Equations ◽  
High Level

scholarly journals Conspecific chemical cues drive density-dependent metabolic suppression independently of resource intake

2020 ◽  
Vol 223 (17) ◽  
pp. jeb224824
Author(s):  
Melanie K. Lovass ◽  
Dustin J. Marshall ◽  
Giulia Ghedini
Keyword(s):  
Metabolic Rate ◽  
Chemical Cues ◽  
Marine Invertebrates ◽  
Feeding Activity ◽  
Food Competition ◽  
Conspecific Density ◽  
Physiological Processes ◽  
Metabolic Suppression ◽  
Metabolic Variation ◽  
Metabolic Reduction

ABSTRACTWithin species, individuals of the same size can vary substantially in their metabolic rate. One source of variation in metabolism is conspecific density – individuals in denser populations may have lower metabolism than those in sparser populations. However, the mechanisms through which conspecifics drive metabolic suppression remain unclear. Although food competition is a potential driver, other density-mediated factors could act independently or in combination to drive metabolic suppression, but these drivers have rarely been investigated. We used sessile marine invertebrates to test how food availability interacts with oxygen availability, water flow and chemical cues to affect metabolism. We show that conspecific chemical cues induce metabolic suppression independently of food and this metabolic reduction is associated with the downregulation of physiological processes rather than feeding activity. Conspecific cues should be considered when predicting metabolic variation and competitive outcomes as they are an important, but underexplored, source of variation in metabolic traits.

scholarly journals Metabolic cost of generating muscular force in human walking: insights from load-carrying and speed experiments

2003 ◽  
Vol 95 (1) ◽  
pp. 172-183 ◽  
Author(s):  
Timothy M. Griffin ◽  
Thomas J. Roberts ◽  
Rodger Kram
Keyword(s):  
Metabolic Rate ◽  
Stance Phase ◽  
Metabolic Cost ◽  
Direct Proportion ◽  
Muscular Force ◽  
Active Muscle ◽  
Cost Coefficient ◽  
Load Carrying ◽  
Leg Muscle ◽  
The Cost

We sought to understand how leg muscle function determines the metabolic cost of walking. We first indirectly assessed the metabolic cost of swinging the legs and then examined the cost of generating muscular force during the stance phase. Four men and four women walked at 0.5, 1.0, 1.5, and 2.0 m/s carrying loads equal to 0, 10, 20, and 30% body mass positioned symmetrically about the waist. The net metabolic rate increased in nearly direct proportion to the external mechanical power during moderate-speed (0.5–1.5 m/s) load carrying, suggesting that the cost of swinging the legs is relatively small. The active muscle volume required to generate force on the ground and the rate of generating this force accounted for >85% of the increase in net metabolic rate across moderate speeds and most loading conditions. Although these factors explained less of the increase in metabolic rate between 1.5 and 2.0 m/s (∼50%), the cost of generating force per unit volume of active muscle [i.e., the cost coefficient ( k)] was similar across all conditions [ k = 0.11 ± 0.03 (SD) J/cm3]. These data indicate that, regardless of the work muscles do, the metabolic cost of walking can be largely explained by the cost of generating muscular force during the stance phase.

Treadmill vs. floor walking: kinematics, electromyogram, and heart rate

1985 ◽  
Vol 59 (1) ◽  
pp. 87-91 ◽  
Author(s):  
M. P. Murray ◽  
G. B. Spurr ◽  
S. B. Sepic ◽  
G. M. Gardner ◽  
L. A. Mollinger
Keyword(s):  
Heart Rate ◽  
Stride Length ◽  
Sagittal Plane ◽  
Treadmill Walking ◽  
Emg Activity ◽  
Normal Female ◽  
Emg Patterns ◽  
Female Subjects

To identify the degree of difference between treadmill and floor walking, kinematic, electromyographic (EMG), and heart rate measurements were recorded in seven normal female subjects during walking at three speeds on the treadmill and on the floor. During treadmill walking, subjects tended to use a faster cadence and shorter stride length than during floor walking. In addition the displacements of the head, hip, and ankle in the sagittal plane showed statistically significant differences between floor and treadmill walking. Average EMG activity was usually greater on the treadmill than on the floor; however, this difference was only significant for the quadriceps. Heart rate was significantly higher during fast treadmill walking than floor walking. In general, treadmill walking was not found to differ markedly from floor walking in kinematic measurements or EMG patterns.

Postural Characterization of Adolescent Federation Basketball Players

2014 ◽  
Vol 11 (7) ◽  
pp. 1401-1407 ◽  
Author(s):  
Patrícia Ferreira Guedes ◽  
Silvia Maria Amado João
Keyword(s):  
Sagittal Plane ◽  
Biological Tissues ◽  
Control Group ◽  
Anatomical Landmarks ◽  
Basketball Players ◽  
Significant Group ◽  
Postural Alignment ◽  
The Right ◽  
High Level ◽  
Postural Analysis

Background:The adolescent players federated to basketball have a high-level of endurance demand, often overloading the biological tissues and causing biomechanical compensations. Due to the immaturity of their musculoskeletal structures those consequences may influence the growing process and lead to the development of various postural patterns. We aimed to evaluate the postural alignment of the trunk in players.Methods:Participants, 74 healthy adolescents: 36 basketball players (BG) and 38 adolescents in control group (CG). First, adolescents were marked with spheres over specific anatomical landmarks. Postural photographs were taken in the sagittal and frontal planes, and analyzed using the free internet Postural Analysis Software to obtain quantitative measures of the head, shoulders, and trunk.Results:ANCOVA has revealed significant group effects: players demonstrated greater lateral spinal inclination (P < .008). In the right sagittal plane, the BG had lower angular values of forward head position (P < .02), pelvic ante version (P < .02), vertical alignment of the trunk (P < .02), and thoracic kyphosis (P < .005). The covariate analysis has indicated that age influences the alignments of both the shoulders and the left scapula; and height influences the scapular alignment.Conclusions:This study has demonstrated that basketball training within federations influences the musculoskeletal system of adolescents and reflects a process of postural adaptations.

scholarly journals Relation between postural sway magnitude and metabolic energy cost during upright standing on a compliant surface

2015 ◽  
Vol 119 (6) ◽  
pp. 696-703 ◽  
Author(s):  
Han Houdijk ◽  
Starr E. Brown ◽  
Jaap H. van Dieën
Keyword(s):  
Postural Control ◽  
Muscle Activation ◽  
Metabolic Response ◽  
Postural Sway ◽  
Center Of Pressure ◽  
Metabolic Cost ◽  
Optimization Criterion ◽  
Metabolic Energy ◽  
Emg Activity ◽  
Upright Standing

Postural control performance is often described in terms of postural sway magnitude, assuming that lower sway magnitude reflects better performance. However, people do not typically minimize sway magnitude when performing a postural control task. Possibly, other criteria are satisfied when people select the amount of sway they do. Minimal metabolic cost has been suggested as such a criterion. The aim of this study was to experimentally test the relation between sway magnitude and metabolic cost to establish whether metabolic cost could be a potential optimization criterion in postural control. Nineteen healthy subjects engaged in two experiments in which different magnitudes of sway were evoked during upright standing on a foam surface while metabolic energy expenditure, center of pressure (CoP) excursion, and muscle activation were recorded. In one experiment, sway was manipulated by visual feedback of CoP excursion. The other experiment involved verbal instructions of standing still, natural or relaxed. In both experiments, metabolic cost changed with sway magnitude in an asymmetric parabolic fashion, with a minimum around self-selected sway magnitudes and a larger increase at small compared with large sway magnitudes. This metabolic response was paralleled by a change in tonic and phasic EMG activity in the major leg muscles. It is concluded that these results are in line with the notion that metabolic cost can be an optimization criterion used to set postural control and as such could account for the magnitude of naturally occurring postural sway in healthy individuals, although the pathway remains to be elucidated.

Potentiated muscular thermogenesis in cold-acclimated muscovy duckling

1985 ◽  
Vol 249 (5) ◽  
pp. R533-R538 ◽  
Author(s):  
H. Barre ◽  
A. Geloen ◽  
J. Chatonnet ◽  
A. Dittmar ◽  
J. L. Rouanet
Keyword(s):  
Metabolic Rate ◽  
Muscular Activity ◽  
Threshold Temperature ◽  
Emg Activity ◽  
Nonshivering Thermogenesis ◽  
Brown Adipose ◽  
Lower Critical Temperature ◽  
Cold Shivering ◽  
Two Temperatures ◽  
Extreme Cold

The capacity for nonshivering thermogenesis (NST) was examined in 26- to 27-day cold-acclimated (CA) muscovy ducklings reared for 21 days at 4 degrees C. Metabolic rate and integrated electromyographic (EMG) muscle activity were measured at ambient temperature ranging from -10 to 28 degrees C. Compared with controls reared at 30 degrees C, CA ducklings were more resistant to cold and had higher peak metabolic rate in extreme cold. Shivering threshold temperature of CA ducklings was 14.2 degrees C lower than lower critical temperature, whereas for controls the two temperatures were similar. Thus CA ducklings exhibited an NST in moderate cold. In addition, at temperatures that produced shivering, EMG activity in CA duckling muscle was lesser than that of controls, even at a higher metabolic rate. Because these ducklings are devoid of brown adipose tissue, these results indicated an increased thermogenic efficiency of muscular activity in CA ducklings.

Modularity of Motor Output Evoked By Intraspinal Microstimulation in Cats

2004 ◽  
Vol 91 (1) ◽  
pp. 502-514 ◽  
Author(s):  
Michel A. Lemay ◽  
Warren M. Grill
Keyword(s):  
Muscle Activation ◽  
Sagittal Plane ◽  
Force Fields ◽  
Isometric Force ◽  
Force Transducer ◽  
Spinal Reflexes ◽  
Lumbar Spinal Cord ◽  
Emg Activity ◽  
Active Force ◽  
Spinal Circuitry

We studied the forces produced at the cat's hindpaw by microstimulation of the ipsi- and contralateral lumbar spinal cord in spinal intact α-chloralose anesthetized ( n = 3) or decerebrate ( n = 3) animals. Isometric force and EMG responses were measured at 9-12 limb configurations, with the paw attached to a force transducer and with the hip and femur fixed. The active forces elicited at different limb configurations were summarized as force fields representing the sagittal plane component of the forces produced at the paw throughout the workspace. The forces varied in amplitude over time but the orientations were stable, and the pattern of an active force field was invariant through time. The active force fields divided into four distinct types, and a few of the fields showed convergence to an equilibrium point. The fields were generally produced by coactivation of the hindlimb muscles. In addition, some of the fields were consistent with known spinal reflexes and the stimulation sites producing them were in laminae where the interneurons associated with those reflexes are known to be located. Muscle activation produced by intraspinal stimulation, as assessed by intramuscular EMG activity, was modified with limb configuration, suggesting that the responses were not fixed, but were modified by position-dependent sensory feedback. The force responses may represent basic outputs of the spinal circuitry and may be related to similar spinal primitives found in the frog and rat.

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