Bio-inspired origamic pouch motors with a high contraction ratio and enhanced force output

This study compared the kinetics, barbell, and joint kinematics and muscle activation patterns between a one-repetition maximum (1-RM) Smith machine squat and isometric squats performed at 10 different heights from the lowest barbell height. The aim was to investigate if force output is lowest in the sticking region, indicating that this is a poor biomechanical region. Twelve resistance trained males (age: 22 ± 5 years, mass: 83.5 ± 39 kg, height: 1.81 ± 0.20 m) were tested. A repeated two-way analysis of variance showed that Force output decreased in the sticking region for the 1-RM trial, while for the isometric trials, force output was lowest between 0–15 cm from the lowest barbell height, data that support the sticking region is a poor biomechanical region. Almost all muscles showed higher activity at 1-RM compared with isometric attempts (p < 0.05). The quadriceps activity decreased, and the gluteus maximus and shank muscle activity increased with increasing height (p ≤ 0.024). Moreover, the vastus muscles decreased only for the 1-RM trial while remaining stable at the same positions in the isometric trials (p = 0.04), indicating that potentiation occurs. Our findings suggest that a co-contraction between the hip and knee extensors, together with potentiation from the vastus muscles during ascent, creates a poor biomechanical region for force output, and thereby the sticking region among recreationally resistance trained males during 1-RM Smith machine squats.

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A modified physical model of high-strength water hydraulic artificial muscles considering the effects of geometry and material properties

Proceedings of the Institution of Mechanical Engineers Part C Journal of Mechanical Engineering Science ◽

10.1177/0954406221999077 ◽

2021 ◽

pp. 095440622199907

Author(s):

Zengmeng Zhang ◽

Jinkai Che ◽

Peipei Liu ◽

Yunrui Jia ◽

Yongjun Gong

Keyword(s):

Physical Model ◽

Relative Error ◽

Wall Thickness ◽

Material Properties ◽

High Strength ◽

Artificial Muscles ◽

Operating Pressure ◽

Rubber Tube ◽

Contraction Ratio ◽

Water Hydraulic

Compared with pneumatic artificial muscles (PAMs), water hydraulic artificial muscles (WHAMs) have the advantages of high force/weight ratio, high stiffness, rapid response speed, large operating pressure range, low working noise, etc. Although the physical models of PAMs have been widely studied, the model of WHAMs still need to be researched for the different structure parameters and work conditions between PAMs and WHAMs. Therefore, the geometry and the material properties need to be considered in models, including the wall thickness of rubber tube, the geometry of ends, the elastic force of rubber tube, the elongation of fibers, and the friction among fiber strands. WHAMs with different wall thickness and fiber materials were manufactured, and static characteristic experiments were performed when the actuator is static and fixed on both ends, which reflects the relationship between contraction force and pressure under the different contraction ratio. The deviations between theoretical values and experimental results were analyzed to investigate the effect of each physical factor on the modified physical model accuracy at different operating pressures. The results show the relative error of the modified physical model was 7.1% and the relative error of the ideal model was 17.4%. When contraction ratio is below 10% and operating pressure is 4 MPa, the wall thickness of rubber tube was the strongest factor on the accuracy of modified model. When the WHAM contraction ratio from 3% to 20%, the relative error between the modified physical model and the experimental data was within ±10%. Considering the various physical factors, the accuracy of the modified physical model of WHAM is improved, which lays a foundation of non-linear control of the high-strength, tightly fiber-braided and thick-walled WHAMs.

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The Global Convergence of the Nonlinear Power Method for Mixed-Subordinate Matrix Norms

Journal of Scientific Computing ◽

10.1007/s10915-021-01524-w ◽

2021 ◽

Vol 88 (1) ◽

Author(s):

Antoine Gautier ◽

Matthias Hein ◽

Francesco Tudisco

Keyword(s):

Global Convergence ◽

Convergence Theorem ◽

Matrix Norm ◽

Nonnegative Matrices ◽

Np Hard ◽

Power Method ◽

Contraction Ratio ◽

Matrix Norms ◽

Vector Norms

AbstractWe analyze the global convergence of the power iterates for the computation of a general mixed-subordinate matrix norm. We prove a new global convergence theorem for a class of entrywise nonnegative matrices that generalizes and improves a well-known results for mixed-subordinate $$\ell ^p$$ ℓ p matrix norms. In particular, exploiting the Birkoff–Hopf contraction ratio of nonnegative matrices, we obtain novel and explicit global convergence guarantees for a range of matrix norms whose computation has been recently proven to be NP-hard in the general case, including the case of mixed-subordinate norms induced by the vector norms made by the sum of different $$\ell ^p$$ ℓ p -norms of subsets of entries.

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Experimental Study on Backflow Patterns Induced by a Bilateral Groin Pair with Different Spacing

Applied Sciences ◽

10.3390/app11041486 ◽

2021 ◽

Vol 11 (4) ◽

pp. 1486

Author(s):

Cuiping Kuang ◽

Yuhua Zheng ◽

Jie Gu ◽

Qingping Zou ◽

Xuejian Han

Keyword(s):

Cross Sections ◽

Large Scale ◽

Recirculation Zone ◽

Flow Direction ◽

Wake Flow ◽

Zone Length ◽

Array Configuration ◽

Contraction Ratio ◽

River Training ◽

Spanwise Velocity

Groins are one of the popular manmade structures to modify the hydraulic flow and sediment response in river training. The spacing between groins is a critical consideration to balance the channel-depth and the cost of construction, which is generally determined by the backflow formed downstream from groins. A series of experiments were conducted using Particle Image Velocimetry (PIV) to observe the influence of groin spacing on the backflow pattern of two bilateral groins. The spacing between groins has significant effect on the behavior of the large-scale recirculation cell behind groins. The magnitude of the wake flow induced by a groin was similar to that induced by another groin on the other side, but the flow direction is opposite. The spanwise velocity near the groin tip dictates the recirculation zone width behind the groins due to the strong links between the spanwise velocity and the contraction ratio of channel cross-sections between groins. Based on previous studies and present experimental results, quantitative empirical relationships are proposed to calculate the recirculation zone length behind groins alternately placed at different spacing along riverbanks. This study provides better understanding and a robust formula to assess the backflow extent of alternate groins and identify the optimum groins array configuration.

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Respiratory load compensation in chronic airway obstruction

Journal of Applied Physiology ◽

10.1152/jappl.1985.59.6.1947 ◽

1985 ◽

Vol 59 (6) ◽

pp. 1947-1954 ◽

Cited By ~ 8

Author(s):

M. Lopata ◽

E. Onal ◽

G. Cromydas

Keyword(s):

Airway Obstruction ◽

Lung Volume ◽

Average Rate ◽

Minute Ventilation ◽

Force Output ◽

Transdiaphragmatic Pressure ◽

Load Compensation ◽

Group A ◽

Group B ◽

Chronic Airway

To assess respiratory neuromuscular function and load compensating ability in patients with chronic airway obstruction (CAO), we studied eight stable patients with irreversible airway obstruction during hyperoxic CO2 rebreathing with and without a 17 cmH2O X l-1 X s flow-resistive inspiratory load (IRL). Minute ventilation (VE), transdiaphragmatic pressure (Pdi), and diaphragmatic electromyogram (EMGdi) were monitored. Pdi and EMGdi were obtained via a single gastroesophageal catheter with EMGdi being quantitated as the average rate of rise of inspiratory (moving average) activity. Based on the effects of IRL on the Pdi response to CO2 [delta Pdi/delta arterial CO2 tension (PaCO2)] and the change in Pdi for a given change in EMGdi (delta Pdi/delta EMGdi) during rebreathing, two groups could be clearly identified. Four patients (group A) were able to increase delta Pdi/delta PaCO2 and delta Pdi/delta EMGdi, whereas in the other four (group B) the IRL responses decreased. All group B patients were hyperinflated having significantly greater functional residual capacity (FRC) and residual volume than group A. In addition the IRL induced percent change in delta Pdi/delta PaCO2, and delta VE/delta PaCO2 was negatively correlated with lung volume so that in the hyperinflated group B the higher the FRC the greater was the decrease in Pdi response due to IRL. In both groups the greater the FRC the greater was the decrease in the ventilatory response to loading. Patients with CAO, even with severe airways obstruction, can effect load compensation by increasing diaphragmatic force output, but the presence of increased lung volume with the associated shortened diaphragm prevents such load compensation.

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Considerations on Designing Artificial Muscle Working at High Pressure

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.268-270.1457 ◽

2012 ◽

Vol 268-270 ◽

pp. 1457-1463

Author(s):

Li Chao Wang ◽

Xiao Dong Wang

Keyword(s):

High Pressure ◽

Material Properties ◽

Weight Ratio ◽

Artificial Muscle ◽

Force Output ◽

Compact Structure ◽

Small Power ◽

Small Force ◽

Working Principle ◽

Contraction Angle

Artificial muscle is a new style of actuator with novel working principle, which owns the advantages of compact structure, high power-to-weight ratio, compliance and easy application. Pneumatic artificial muscle (PAM) is usually used in robotics, medical auxiliaries and other small force output occasions nowadays. However, it suffers problems of small power, hysteresis and poor repeatability. A kind of artificial muscle working at high pressure was researched. Different muscle styles are compared and MicKibben structure is selected while fluid media is determined. Furthermore, factors of geometry and material properties, which limit the ultimate pressure, are analyzed. Formulas and simulations verify the influence of limitation and help to calculate key parameters of 18MPa artificial muscle. Data show that it is possible in theory to design high pressure artificial muscle by overall consideration of initial diameter, initial contraction angle and material properties, initial length only influent the stroke.

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Neurophysiological changes in the visuomotor network after practicing a motor task

Journal of Neurophysiology ◽

10.1152/jn.00020.2018 ◽

2018 ◽

Vol 120 (1) ◽

pp. 239-249 ◽

Cited By ~ 10

Author(s):

James E. Gehringer ◽

David J. Arpin ◽

Elizabeth Heinrichs-Graham ◽

Tony W. Wilson ◽

Max J. Kurz

Keyword(s):

Motor Learning ◽

Motor Planning ◽

Motor Task ◽

Force Production ◽

Oscillatory Activity ◽

Matching Task ◽

Force Output ◽

Motor Action ◽

Visuomotor Transformations ◽

Target Matching

Although it is well appreciated that practicing a motor task updates the associated internal model, it is still unknown how the cortical oscillations linked with the motor action change with practice. The present study investigates the short-term changes (e.g., fast motor learning) in the α- and β-event-related desynchronizations (ERD) associated with the production of a motor action. To this end, we used magnetoencephalography to identify changes in the α- and β-ERD in healthy adults after participants practiced a novel isometric ankle plantarflexion target-matching task. After practicing, the participants matched the targets faster and had improved accuracy, faster force production, and a reduced amount of variability in the force output when trying to match the target. Parallel with the behavioral results, the strength of the β-ERD across the motor-planning and execution stages was reduced after practice in the sensorimotor and occipital cortexes. No pre/postpractice changes were found in the α-ERD during motor planning or execution. Together, these outcomes suggest that fast motor learning is associated with a decrease in β-ERD power. The decreased strength likely reflects a more refined motor plan, a reduction in neural resources needed to perform the task, and/or an enhancement of the processes that are involved in the visuomotor transformations that occur before the onset of the motor action. These results may augment the development of neurologically based practice strategies and/or lead to new practice strategies that increase motor learning. NEW & NOTEWORTHY We aimed to determine the effects of practice on the movement-related cortical oscillatory activity. Following practice, we found that the performance of the ankle plantarflexion target-matching task improved and the power of the β-oscillations decreased in the sensorimotor and occipital cortexes. These novel findings capture the β-oscillatory activity changes in the sensorimotor and occipital cortexes that are coupled with behavioral changes to demonstrate the effects of motor learning.

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Intermittency in the Control of Continuous Force Production

Journal of Neurophysiology ◽

10.1152/jn.2000.84.4.1708 ◽

2000 ◽

Vol 84 (4) ◽

pp. 1708-1718 ◽

Cited By ~ 203

Author(s):

Andrew B. Slifkin ◽

David E. Vaillancourt ◽

Karl M. Newell

Keyword(s):

Visual Feedback ◽

Visual Information ◽

Spectral Power ◽

Force Production ◽

Motor Output ◽

Force Variability ◽

Force Output ◽

Feedback Information ◽

Information Processes ◽

Feedback Frequency

The purpose of the current investigation was to examine the influence of intermittency in visual information processes on intermittency in the control continuous force production. Adult human participants were required to maintain force at, and minimize variability around, a force target over an extended duration (15 s), while the intermittency of on-line visual feedback presentation was varied across conditions. This was accomplished by varying the frequency of successive force-feedback deliveries presented on a video display. As a function of a 128-fold increase in feedback frequency (0.2 to 25.6 Hz), performance quality improved according to hyperbolic functions (e.g., force variability decayed), reaching asymptotic values near the 6.4-Hz feedback frequency level. Thus, the briefest interval over which visual information could be integrated and used to correct errors in motor output was approximately 150 ms. The observed reductions in force variability were correlated with parallel declines in spectral power at about 1 Hz in the frequency profile of force output. In contrast, power at higher frequencies in the force output spectrum were uncorrelated with increases in feedback frequency. Thus, there was a considerable lag between the generation of motor output corrections (1 Hz) and the processing of visual feedback information (6.4 Hz). To reconcile these differences in visual and motor processing times, we proposed a model where error information is accumulated by visual information processes at a maximum frequency of 6.4 per second, and the motor system generates a correction on the basis of the accumulated information at the end of each 1-s interval.

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Ultrasonic evaluation of muscle functional recovery following free functioning gracilis transfer, a preliminary study

European Journal of Medical Research ◽

10.1186/s40001-020-00473-8 ◽

2021 ◽

Vol 26 (1) ◽

Author(s):

Yi Hou ◽

Jiantao Yang ◽

Bengang Qin ◽

Liqiang Gu ◽

Jia Zheng

Keyword(s):

Muscle Strength ◽

Functional Recovery ◽

Linear Regression Analysis ◽

Gracilis Muscle ◽

Ultrasound Measurement ◽

Multivariate Linear Regression Analysis ◽

Joint Mobility ◽

Post Transplant ◽

Rest State ◽

Contraction Ratio

Abstract Background Ultrasonic measurement has not been utilized to assess the functional recovery of transplanted muscle. This study aimed to investigate the feasibility of using B-ultrasound measurement to assess muscle recovery following free functioning gracilis transfer. Methods From January 2009 to January 2014, 35 patients receiving free functioning gracilis transfer to treat total brachial plexus injury were enrolled. B-ultrasound was adopted to determine the cross-sectional area (CSA) of transplanted gracilis muscle at rest and contraction state. The ratio of pre- to post-transplant CSA value at rest state was defined as muscle bulk ratio (MBR). The ratio of CSA value at contraction state to rest state was defined as contraction ratio (CR). Results Patients with muscle strength M ≥ 4 had significantly higher CR1 (post-transplant), CR2 (pre-transplant), and range of motion (ROM, joint mobility) than those with muscle strength M < 4. The CR1 > CR2 group had significantly higher CR1, muscle strength, and ROM than the CR1 ≤ CR2 group. The MBR > 1 group had significantly higher muscle strength than the MBR ≤ 1 group. CR1 value was highly correlated with muscle strength and with ROM. CR2 value was moderately correlated with muscle strength and ROM. Multivariate linear regression analysis showed that a higher CR1/CR2 value was associated with a higher muscle strength and joint mobility. The CR1 > CR2 group had better muscle strength and ROM than the CR1 ≤ CR2 groups. Conclusion B-ultrasound measurement can quantitatively reflect muscle strength following gracilis transfer, and CR value could be a potential indicator for functional recovery of the transplanted gracilis muscle. Level of Evidence: Prognostic studies, Level II.

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Decorrelation of cortical inputs and motoneuron output

Journal of Neurophysiology ◽

10.1152/jn.00336.2011 ◽

2011 ◽

Vol 106 (5) ◽

pp. 2688-2697 ◽

Cited By ~ 41

Author(s):

Francesco Negro ◽

Dario Farina

Keyword(s):

Motor Cortex ◽

Primary Motor Cortex ◽

Small Population ◽

Spectral Lines ◽

Spinal Motoneurons ◽

Force Output ◽

Cortical Input ◽

Motoneuron Pool ◽

Discharge Rates ◽

Cortical Inputs

Oscillations in the primary motor cortex are transmitted through the corticospinal tract to the motoneuron pool. This pathway is believed to produce an effective and direct command from the motor cortex to the spinal motoneurons for the modulation of the force output. In this study, we used a computational model of a population of motoneurons to investigate the factors that can influence the transmission of the cortical input to the output of motoneurons, since it can be quantified by coherence analysis. The simulations demonstrated that, despite the nonlinearity of the motoneurons, oscillations present in the cortical input are transmitted to the output of the motoneuron pool at the same frequency. However, the interference introduced by the nonlinearity of the system increases the variability of the oscillations in output, introducing spectral lines whose frequency depends on the input frequencies and the motoneuron discharge rates. Moreover, an additional source of synaptic input common to all motoneurons but independent from the corticospinal component decorrelates the cortical input and motoneuron output and, thus, decreases the magnitude of the estimated coherence, even if the effective cortical drive does not change. These results indicate that the corticospinal input can effectively be sampled by a small population of motoneurons. However, the transmission of a corticospinal drive to the motoneuron pool is influenced by the nonlinearity of the spiking processes of the active motoneurons and by synaptic inputs common to the motoneuron population but independent from the cortical input.

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