Electromyographic Study of Postural Muscles in Various Positions and Movements

1956 ◽  
Vol 186 (1) ◽  
pp. 122-126 ◽  
Author(s):  
Harold Portnoy ◽  
F. Morin
Keyword(s):  
Electrical Activity ◽  
Vertebral Column ◽  
Normal Subjects ◽  
Center Of Gravity ◽  
The Body ◽  
Lateral Flexion ◽  
Trunk Flexion ◽  
Hip Joints ◽  
Flexion And Extension ◽  
Postural Muscles

Electrical activity of ‘postural’ muscles (sacrospinales, hamstrings, gastrocnemii, quadriceps femoris) in normal subjects during different positions and movements of the body varies in different individuals. The sacrospinales become active whenever slight displacements of the center of gravity occur. The sacrospinalis of both sides participate in lateral flexion and extension, and rotation of the vertebral column. In leaning forward, these muscles (except the quadriceps) are working essentially under isometric conditions and their electrical activity is prominent. Stretch, then, appears to be a major factor for the activation of these muscles. In flexion of the trunk, the sacrospinales cease to function at a ‘critical point,’ however, further trunk flexion occurring mainly at the hip joints continues to be accompanied by the activity present in the hamstrings. In more complex movements, such as sitting and standing, the same basic mechanisms related to stretch and displacement of the center of gravity appear to hold true.

scholarly journals Biomechanical Analysis of Successful and Unsuccessful Snatch Lifts in Elite Female Weightlifters

2019 ◽  
Vol 68 (1) ◽  
pp. 69-79 ◽  
Author(s):  
Andrzej Mastalerz ◽  
Paulina Szyszka ◽  
Weronika Grantham ◽  
Jerzy Sadowski
Keyword(s):  
Performance Analysis ◽  
Body Movement ◽  
Center Of Gravity ◽  
The Body ◽  
Biomechanical Analysis ◽  
Hip Joints ◽  
Factors Affecting ◽  
Analysis System ◽  
Biomechanical Factors

AbstractThe aim of this study was to identify biomechanical factors affecting successful and unsuccessful snatch attempts in elite female weightlifters during the 2013 World Weightlifting Championships. Fourteen female competitors took part in this study. Their successful and unsuccessful snatch lifts with the same load were recorded with 2 camcorders (50 Hz), and selected points were digitized manually on to the body and the barbell using the Ariel Performance Analysis System. The kinetic and kinematic barbell movement as well as the athlete’s body movement variables during the liftoff phase were examined. The results of this study show statistical differences (p ≤ 0.05) between successful and unsuccessful attempts in relation to the angle values in the knee and hip joints in preparation for the aerial phase position. Similarly, the center of gravity velocity was significantly higher in successful attempts during the catch phase. Thus, coaches should pay particular attention to the accuracy of the execution in preparation for the aerial phase position and to the velocity of the center of gravity of the competitors during the catch phase.

Ergometric evaluation of pathological gait

1983 ◽  
Vol 55 (2) ◽  
pp. 606-613 ◽  
Author(s):  
G. A. Cavagna ◽  
L. Tesio ◽  
T. Fuchimoto ◽  
N. C. Heglund
Keyword(s):  
Kinetic Energy ◽  
Sagittal Plane ◽  
Normal Subjects ◽  
Step Length ◽  
Center Of Gravity ◽  
The Body ◽  
Gravitational Potential Energy ◽  
Maximal Height ◽  
Pathological Gait ◽  
Positive Work

At each step of walking, the center of gravity of the body moves up and down and accelerates and decelerates forward with a combined movement that allows an appreciable transfer (R) between gravitational potential energy and kinetic energy, as occurs in a pendulum. The positive work and power to lift the center of gravity, to accelerate it forward, and to maintain its motion in a sagittal plane, the amount of R, the maximal height reached during each step by the center of gravity, and the step length and frequency are all determined by a microcomputer a few minutes after a subject walks on a force platform. This method is applied to the analysis of pathological gait in the attempt to measure quantitatively the alteration of the normal locomotory movement of the center of gravity. The strides of the patient are compared with the strides of normal subjects; in addition, the movement of the center of gravity of the patient during the stance on the affected limb is compared with the movement of the center of gravity during the stance on the unaffected limb, thus giving an index of the asymmetry of locomotion. biomechanics; locomotion; walking; mechanical work Submitted on January 21, 1982 Accepted on March 3, 1983

scholarly journals Development of the multi-segment lumbar spine for humanoid robots

2016 ◽  
Vol 20 (suppl. 2) ◽  
pp. 581-590 ◽  
Author(s):  
Marko Pencic ◽  
Branislav Borovac ◽  
Dusan Kovacevic ◽  
Maja Cavic
Keyword(s):  
Carrying Capacity ◽  
Humanoid Robots ◽  
The Body ◽  
Flexible Structure ◽  
Lateral Flexion ◽  
Hip Joints ◽  
Positioning Accuracy ◽  
Dynamical Simulation ◽  
Flexion Extension ◽  
Accuracy And Repeatability

The paper presents development of multi-segment lumbar structure based on the human spine. The research is performed within the project based on development of socially acceptable robot named "SARA". Two approaches for spine realization of humanoids exist: multi-joint viscoelastic structures (5-10 joints) that have variable flexibility and structures that consist of one joint - torso/waist joint, which has low elasticity and high stiffness. We propose multi-joint flexible structure with stiff, low backlash and self-locking mechanisms that require small actuators. Based on kinematic-dynamic requirements dynamical model of robot is formed. Dynamical simulation is performed for several postures of the robot and driving torques of lumbar structure are determined. During development of the lumbar structure 16 variant solutions are considered. Developed lumbar structure consists of three equal segments, it has 6 DOFs (2 DOFs per segment) and allows movements of lateral flexion ?30? and torsion ?45?, as well as the combination of these two movements. In development phase the movements of flexion/extension are excluded, for the bending of the body forward to an angle of 45? is achieved by rotation in the hip joints. Proposed solution of the lumbar structure is characterized by self-locking of mechanisms (if for any reason actuators stop working, lumbar structure retains current posture), low backlash (high positioning accuracy and repeatability of movements), compactness, high carrying capacity and small dimensions.

The Role of Computer Modeling in Electrocardiography

1990 ◽  
Vol 29 (04) ◽  
pp. 282-288 ◽  
Author(s):  
A. van Oosterom
Keyword(s):  
Electrical Activity ◽  
Computer Modeling ◽  
Body Surface ◽  
Electrical Current ◽  
The Body ◽  
Volume Conductor ◽  
Current Generator ◽  
Cardiac Electrical Activity ◽  
Source Models

AbstractThis paper introduces some levels at which the computer has been incorporated in the research into the basis of electrocardiography. The emphasis lies on the modeling of the heart as an electrical current generator and of the properties of the body as a volume conductor, both playing a major role in the shaping of the electrocardiographic waveforms recorded at the body surface. It is claimed that the Forward-Problem of electrocardiography is no longer a problem. Several source models of cardiac electrical activity are considered, one of which can be directly interpreted in terms of the underlying electrophysiology (the depolarization sequence of the ventricles). The importance of using tailored rather than textbook geometry in inverse procedures is stressed.

Shifting of the body center of gravity in low-risk preterm infants: A video-pedoscope study

2018 ◽  
Vol 124 ◽  
pp. 33-37 ◽  
Author(s):  
Natascia Bertoncelli ◽  
Laura Lucaccioni ◽  
Luca Ori ◽  
Christa Einspieler ◽  
Heinz F.R. Prechtl ◽  
...  
Keyword(s):  
Preterm Infants ◽  
Center Of Gravity ◽  
The Body ◽  
Low Risk ◽  
Body Center

Immediate diaphragmatic electromyogram responses to imperceptible mechanical loads in conscious humans

1992 ◽  
Vol 73 (1) ◽  
pp. 248-259 ◽  
Author(s):  
E. J. Kobylarz ◽  
J. A. Daubenspeck
Keyword(s):  
Electrical Activity ◽  
Lung Volume ◽  
Muscle Activity ◽  
Normal Subjects ◽  
Tonic Activity ◽  
Phasic Activity ◽  
Mechanical Loads ◽  
Oral Airway ◽  
Pattern Regulation ◽  
Adaptive Pattern

We used an esophageal electrode to measure the amplitude and neural inspiratory and expiratory (N TE) timing responses of crural diaphragmatic electrical activity in response to flow-resistive (R) and elastic (E) loads at or below the threshold for conscious detection, applied pseudorandomly to the oral airway of eight normal subjects. We observed a rapid first-breath neural reflex that modified respiratory timing such that N TE lengthened significantly in response to R loads in six of eight subjects and shortened in response to E loading in six of seven subjects. The prolongation of N TE with R loading resulted primarily from lengthening the portion of N TE during which phasic activity in the diaphragm is absent (TE NDIA), whereas E loading shortened N TE mainly by reducing TE NDIA. Most subjects responded to both types of loading by decreasing mean tonic diaphragmatic activity, the average level of muscle activity that exists when no phasic changes are occurring, as well as its variability. The observed timing responses are consistent in direction with optimally adaptive pattern regulation, whereas the modulation of tonic activity may be useful in neural regulation of end-expiratory lung volume.

scholarly journals SINGLE LEG SQUAT COMPENSATIONS ASSOCIATE WITH SOFTBALL PITCHING PATHOMECHANICS IN ADOLESCENT SOFTBALL PITCHERS

2021 ◽  
Vol 9 (7_suppl3) ◽  
pp. 2325967121S0006
Author(s):  
Gretchen D. Oliver ◽  
Kenzie B. Friesen ◽  
Regan E. Shaw ◽  
David Shannon ◽  
Jeffrey Dugas ◽  
...  
Keyword(s):  
Center Of Mass ◽  
Knee Valgus ◽  
Trunk Rotation ◽  
Lateral Flexion ◽  
Trunk Flexion ◽  
Backward Elimination ◽  
Potential Risk Factors ◽  
Single Leg Squat ◽  
Tracking Device ◽  
The Relationship

Background: Softball pitchers have an eminent propensity for injury due to the high repetition and ballistic nature of the pitch. As such, trunk pathomechanics during pitching have been associated with upper extremity pain. The single leg squat (SLS) is a simple diagnostic tool used to examine LPHC and trunk stability. Research shows a lack of LPHC stability is often associated with altered pitching mechanics consequently increasing pain and injury susceptibility. Hypothesis/Purpose: The purpose of this study was to examine the relationship between trunk compensatory kinematics during the SLS and kinematics during foot contact of the windmill pitch. The authors hypothesized there would be a relationship between SLS compensations and pitch kinematics previously associated with injury. In using a simple clinical assessment such as the SLS, athletes, coaches, parents, and clinicians can identify potential risk factors that may predispose the athlete to injurious movement patterns. Methods: Fifty-five youth and high school softball pitchers (12.6±2.2 years, 160.0±11.0 cm, 60.8±15.5 kg) were recruited to participate. Kinematic data were collected at 100Hz using an electromagnetic tracking device. Participants were asked to complete a SLS on their stride leg (contralateral to their throwing arm), then throw 3 fastballs at maximal effort. Values of trunk flexion, trunk lateral flexion, and trunk rotation at peak depth of the SLS were used as the dependent variables in three separate backward elimination regression analyses. Independent variables examined at foot contact of the pitch included: trunk flexion, trunk lateral flexion, trunk rotation, center of mass, stride length, and stride knee valgus. Results: The SLS trunk rotation regression, F(1,56) = 4.980, p = .030, revealed trunk flexion significantly predicted SLS trunk rotation (SE = .068, t = 2.232, p = .030) and explained approximately 7% of variance (Adj. R2 = .066). The SLS trunk flexion regression, F(1,56) = 5.755, p = .020, revealed stride knee valgus significantly predicted SLS trunk flexion (SE = .256, t = 2.399, p = .020) and explained approximately 8% of variance (Adj. R2 = .078). Conclusion/Significance: Additional trunk rotation and trunk flexion at peak depth of the SLS indicate increased knee valgus and trunk flexion at foot contact of the pitch, both of which suggest poor LPHC stability, may increase the potential for injury. Athletes, coaches and clinicians should acknowledge the risk of poor LPHC in softball pitching and implement exercises to improve LPHC stability in effort to decrease pitching pathomechanics and associated pain.

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