scholarly journals An Experimental Study of the Influence of Hand-Arm Posture and Grip Force on the Mechanical Impedance of Hand-Arm System

2021 ◽  
Vol 2021 ◽  
pp. 1-11
Author(s):  
Wenjie Zhang ◽  
Qichao Wang ◽  
Zheng Xu ◽  
Hongmei Xu ◽  
Hang Li ◽  
...  
Keyword(s):  
Grip Force ◽  
Mechanical Impedance ◽  
Test System ◽  
Human Hand ◽  
Adult Males ◽  
Obvious Effect ◽  
Elbow Angle ◽  
Vibration Intensity ◽  
Vibration Excitation ◽  
40 Hz

In order to investigate the effects of hand-arm posture, grip force, push force, and vibration excitation intensity on the mechanical impedance of human hand-arm system, a test system with a self-developed vibration handle has been prepared. Based on the testing system, the mechanical impedance of the hand-arm system of seven Chinese adult males were tested and calculated under the random vibration excitation with the frequency of 10–1000 Hz. The results reveal that when the frequency is lower (<40 Hz), the hand-arm system with an elbow angle of 180o produces a higher mechanical impedance; when the frequency ranges from 40 Hz to 100 Hz, the hand-arm system with an elbow angle of 90o generates a higher mechanical impedance; while when the frequency is higher (>100 Hz), the hand-arm posture seems to have no obvious effect on the mechanical impedance. Higher grip or push force would increase the frequency corresponding to the peak value of the mechanical impedance and often correspond to a higher mechanical impedance in a specific frequency range (30–200 Hz). When the frequency is lower (<140 Hz), vibration intensity has certain effects on the mechanical impedance of the hand-arm system. In conclusion, vibration intensity does not directly affect the mechanical impedance, but an increase in grip or push force often causes an increase in mechanical impedance and a higher frequency that corresponds to the peak of mechanical impedance.

scholarly journals Neutering Effects on Social Behaviour of Urban Unowned Free-Roaming Domestic Cats

Animals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 1105 ◽  
Author(s):  
Simona Cafazzo ◽  
Roberto Bonanni ◽  
Eugenia Natoli
Keyword(s):  
General Level ◽  
Territorial Behaviour ◽  
Adult Males ◽  
Domestic Cats ◽  
Obvious Effect ◽  
Focal Animal ◽  
The Hierarchical Structure ◽  
Group Members ◽  
Marking Behaviour ◽  
Free Ranging

The “trap, spay/neuter, and release” programs to manage unowned free-roaming cat populations are diffused worldwide and they are largely advised even in countries where the suppression of unowned cats is enforced by law. Despite the massive neutering campaigns in the world, there is little information on the influence of neutering on individual cat behaviour, as well as on the social structure of cat colonies. The aim of this study is to verify such effects. Before neutering, the group consisted of 17 free-roaming domestic cats, who were totally unrestrained. After neutering it consisted of 16 individuals. Data on the outcomes of aggressive, submissive, affiliative, and territorial behaviour were collected, using classic ethological methods (“focal animal”, “all occurrences”, and “1/0” sampling methods) (735 h of observation before and 537 h after neutering). The dominance hierarchy did not change after neutering. On the other hand, the frequency of aggressive, territorial behaviour as well as proximity among individuals decreased significantly. Affiliative behaviour has been observed among neutered adult males that never performed it before neutering. The results of this study suggest that, after neutering: (i) The group of free-ranging cats was stable over time; (ii) the hierarchical structure of the cat social group did not change; (iii) the general level of activity, decreased; (iv) urine spraying marking behaviour almost disappeared; (v) the level of social proximity among group members decreased, although it tended to increase in some male–male dyads. The most obvious effect of neutering, detected on individual behaviour, was that cats were less active.

scholarly journals Tracking upper limbs fatigue by means of electronic dynamometry

2015 ◽  
Vol 21 (2) ◽  
pp. 214-221
Author(s):  
Fernando Max Lima ◽  
Luciane Fernanda Rodrigues Martinho Fernandes ◽  
Dernival Bertoncello
Keyword(s):  
Experimental Study ◽  
Young Adult ◽  
Muscle Fatigue ◽  
Grip Force ◽  
Load Cell ◽  
Peak Force ◽  
Transversal Design ◽  
Upper Limbs ◽  
Adult Males ◽  
Best Parameter

This study aimed to identify useful electronic grip dynamometry parameters to track differences between trained (TR) and untrained (UT) participants, and between dominant (DO) and non-dominant (ND) limbs as a consequence of upper limbs muscle fatigue following 10 RM tests of the brachial biceps. This experimental study with transversal design involved 18 young adult males, of whom 9 were untrained and 9 were experienced in resistance training.Isometric grip force was evaluated (30 seconds long) previous and after 10RM tests by means of a G200 Model grip dynamometer with precision load cell (Biometrics(r)). Significant differences between initial and final measurements were found only for trained participants: Peak force for TR-DO (67.1 vs 55.5 kgf, p = .0277); Raw average for TR-DO (46.96 vs 42.22 kgf, p = .0464), and for TR-ND (40.34 vs 36.13 kgf, p = .0277). Electronic grip dynamometry efficiently identified upper limbs fatigue in trained participants, being raw average measurements the best parameter.

Mechanical Impedance of Rat Glabrous Skin and Its Relation with Skin Morphometry

2021 ◽  
Author(s):  
Çaglar Gök ◽  
Ismail Devecioglu ◽  
Burak Guclu
Keyword(s):  
Mechanical Properties ◽  
Mechanical Impedance ◽  
Glabrous Skin ◽  
Mechanical Resistance ◽  
Model Parameters ◽  
Inertial Effects ◽  
Rat Skin ◽  
Intact Skin ◽  
Lumped Element ◽  
40 Hz

Abstract The mechanical impedance of intact and epidermis-peeled rat glabrous skin was studied at two sites (digit and sole) and at two frequencies (40 Hz and 250 Hz). The thicknesses of skin layers at the corresponding regions were measured histologically from intact- and peeled-skin samples in every subject. Compared to intact sole skin, digital rat skin has thicker layers and higher mechanical resistance, and it is less stiff. The resistance of the skin significantly decreased after epidermal peeling at both the digit and the sole. Furthermore, peeling caused the reactance to become positive due to inertial effects. As the frequency was increased from 40 to 250 Hz, the resistance and stiffness also increased for the intact skin, while the peeled skin showed less frictional (i.e. resistance) but more inertial (i.e. positive reactance) effects. We estimated the mechanical properties of epidermis and dermis with lumped-element models developed for both intact and peeled conditions. The models predicted that dermis has higher mass, lower stiffness, and lower resistance compared to epidermis, similar to the experimental impedance results obtained in the peeled condition which consisted mostly of dermis. The overall impedance was simulated more successfully at 40 Hz. When both frequencies are considered, the models produced consistent results for resistance in both conditions. The results imply that most of the model parameters should be frequency-dependent, and suggest that mechanical properties of epidermis can be related to its thickness. These findings may help in designing artificial skin for neuroprosthetic limbs.

Biodynamic Response of Human Fingers in a Power Grip Subjected to a Random Vibration

2004 ◽  
Vol 126 (4) ◽  
pp. 447-457 ◽  
Author(s):  
R. G. Dong ◽  
D. E. Welcome ◽  
T. W. McDowell ◽  
J. Z. Wu
Keyword(s):  
High Frequency ◽  
Random Vibration ◽  
Grip Force ◽  
Frequency Effect ◽  
Human Hand ◽  
Vibration Exposure ◽  
Power Grip ◽  
Coupling Force ◽  
Frequency Weighting ◽  
Male Subjects

Background. Knowledge of the biodynamic response (BR) of the human hand-arm system is an important part of the foundation for the measurement and assessment of hand-transmitted vibration exposure. This study investigated the BR of human fingers in a power grip subjected to a random vibration. Method. Ten male subjects were used in the experiment. Each subject applied three coupling actions to a simulated tool handle at three different finger grip force levels. Results and Conclusions. The BR is practically independent of the hand coupling actions for frequencies at or above 100 Hz. Above 50 Hz, the BR is correlated to finger and hand sizes. Increasing the finger coupling force significantly increases the BR. Therefore, hand forces should be measured and used when assessing hand-transmitted vibration exposure. The results also show that under a constant-velocity vibration, the finger vibration power absorption at frequencies above 200 Hz is approximately twice that at frequencies below 100 Hz. This suggests that the frequency weighting specified in the current ISO 5349-1 (2001) may underestimate the high frequency effect on vibration-induced finger disorders.

scholarly journals Evaluating Viscoelastic Properties of the Wrist Joint During External Perturbations: Influence of Velocity, Grip, and Handedness

2021 ◽  
Vol 15 ◽  
Author(s):  
Valeria Falzarano ◽  
Michael W. R. Holmes ◽  
Lorenzo Masia ◽  
Pietro Morasso ◽  
Jacopo Zenzeri
Keyword(s):  
Viscoelastic Properties ◽  
Grip Force ◽  
Mechanical Characteristics ◽  
Wrist Joint ◽  
Maximum Voluntary Contraction ◽  
Mechanical Impedance ◽  
Experimental Conditions ◽  
External Perturbations ◽  
Custom Made ◽  
Flexion Extension

In this study, we designed a robot-based method to compute a mechanical impedance model that could extract the viscoelastic properties of the wrist joint. Thirteen subjects participated in the experiment, testing both dominant and nondominant hands. Specifically, the robotic device delivered position-controlled disturbances in the flexion-extension degree of freedom of the wrist. The external perturbations were characterized by small amplitudes and fast velocities, causing rotation at the wrist joint. The viscoelastic characteristics of the mechanical impedance of the joint were evaluated from the wrist kinematics and corresponding torques. Since the protocol used position inputs to determine changes in mean wrist torque, a detailed analysis of wrist joint dynamics could be made. The scientific question was whether and how these mechanical features changed with various grip demands and perturbation velocities. Nine experimental conditions were tested for each hand, given by the combination of three velocity perturbations (fast, medium, and slow) and three hand grip conditions [self-selected grip, medium and high grip force, as percentage of the maximum voluntary contraction (MVC)]. Throughout the experiments, electromyographic signals of the extensor carpi radialis (ECR) and the flexor carpi radialis (FCR) were recorded. The novelty of this work included a custom-made soft grip sensor, wrapped around the robotic handle, to accurately quantify the grip force exerted by the subjects during experimentation. Damping parameters were in the range of measurements from prior studies and consistent among the different experimental conditions. Stiffness was independent of both direction and velocity of perturbations and increased with increasing grip demand. Both damping and stiffness were not different between the dominant and nondominant hands. These results are crucial to improving our knowledge of the mechanical characteristics of the wrist, and how grip demands influence these properties. This study is the foundation for future work on how mechanical characteristics of the wrist are affected in pathological conditions.

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