Organizing principles for single-joint movements. II. A speed-sensitive strategy

1989 ◽  
Vol 62 (2) ◽  
pp. 358-368 ◽  
Author(s):  
D. M. Corcos ◽  
G. L. Gottlieb ◽  
G. C. Agarwal
Keyword(s):  
Muscle Activation ◽  
Human Subjects ◽  
Movement Time ◽  
Initial Position ◽  
Joint Torque ◽  
Movement Speed ◽  
Movement Kinematics ◽  
Antagonist Muscles ◽  
Speed Accuracy ◽  
Organizing Principles

1. Normal human subjects made discrete flexions of the elbow over a fixed distance in the horizontal plane from a stationary initial position to a visually defined target. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Changes in movement speed were elicited either by explicit instruction to the subject or by adjusting the target width. Instructions always required accurately stopping in the target zone. 3. Peak inertial torques and accelerations, movement times, and integrated EMGs were all highly correlated with speed. We show that inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the task, the EMG, and movement kinematics. 4. When subjects perform tasks that require control of movement speed, they adjust the rate at which torque is developed by the muscles. This rate is modulated by the way in which the muscles are activated. The rate at which joint torque develops is correlated with the rate at which the agonist EMG rises as well as with integrated EMG. 5. The antagonist EMG shows two components. The latency of the first is 30-50 ms and independent of movement dynamics. The latency of the second component is proportional to movement time. The rate of rise and area of both components scale with torque. 6. We propose organizing principles for the control of single-joint movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 7. A model is proposed in which movements made under a speed-sensitive strategy are executed by controlling the intensity of an excitation pulse delivered to the motoneuron pool. The effect is to regulate the rate at which joint torque, and consequently acceleration, increases. 8. Movements of variable distance, speed, accuracy, and load are shown to be controlled by one of two consistent sets of rules for muscle activation. These rules apply to the control of both the agonist and antagonist muscles. Rules of activation lead to distinguishable patterns of EMG and torque development. All observable changes in movement kinematics are explained as deterministic consequences of these effects.

Organizing principles for single-joint movements. I. A speed-insensitive strategy

1989 ◽  
Vol 62 (2) ◽  
pp. 342-357 ◽  
Author(s):  
G. L. Gottlieb ◽  
D. M. Corcos ◽  
G. C. Agarwal
Keyword(s):  
Human Subjects ◽  
Movement Time ◽  
Muscle Length ◽  
Initial Position ◽  
Inertial Load ◽  
Antagonist Muscles ◽  
Human Movements ◽  
Inertial Torque ◽  
Highly Correlated ◽  
Organizing Principles

1. Normal human subjects made discrete elbow flexions and extensions in the horizontal plane from a stationary initial position to visually defined targets at different distances with a constant inertial load or made flexions to a visually defined target with different inertial loads. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects were instructed to move their limbs accurately but quickly to the targets. Movements of greater distances or lesser loads were performed at higher velocities. 3. Peak inertial torque, acceleration and velocity, movement time, and integrated, rectified EMG were all highly correlated with the task variables, distance and inertial load. We show that peak inertial torque can be used as a linking variable that is almost sufficient to explain all correlations between the tasks, the EMG, and movement kinematics. 4. The rate at which subjects initially developed torque to accelerate their movements was invariant over changes in the value of either task variable. The rising phase of the agonist EMG was also independent of the distance or load moved. 5. Two components were distinguished in the antagonist EMG. The first had a relatively constant latency and amplitude. It terminated on the onset of the second and larger component at a latency that was delayed as both distance and load increased. 6. The integrated, rectified antagonist EMG was proportional to inertial load and peak decelerating torque for changes in inertial load. When target distance varied, proportionality between peak decelerating torque and antagonist EMG could be found if correction was made for the effects of muscle length on the torque-EMG relationship. 7. We propose organizing principles for the control of single-joint human movements in which tasks are performed by one of two strategies. These are called speed-insensitive and speed-sensitive strategies. 8. A model is described in which movements made under a speed-insensitive strategy are executed by controlling the duration and the relative timing of amplitude invariant patterns of activation to the spinal motoneuron pools.

Organizing principles for single joint movements. III. Speed-insensitive strategy as a default

1990 ◽  
Vol 63 (3) ◽  
pp. 625-636 ◽  
Author(s):  
G. L. Gottlieb ◽  
D. M. Corcos ◽  
G. C. Agarwal ◽  
M. L. Latash
Keyword(s):  
Human Subjects ◽  
Movement Control ◽  
Initial Position ◽  
Initial Slope ◽  
Range Of Movement ◽  
Stationary Target ◽  
Wide Range ◽  
Inertial Torque ◽  
Maximal Speed ◽  
Speed Accuracy

1. Human subjects made discrete elbow flexions in a horizontal plane over different distances, from a stationary initial position to a visually defined stationary target 9 degrees wide. We measured joint angle, acceleration, and electromyograms (EMGs) from two agonist and two antagonist muscles. 2. Subjects made movements over four different distances following one of four different instructions. The first instructed the subject simply to choose a comfortable speed. The other three explicitly emphasized either speed, accuracy, or maintenance of the "same" speed over different distances. These instructions produced a wide range of movement velocities. 3. The initial rises of the acceleration (and therefore of the inertial torque), as well as the initial slope of the agonist EMG, were all invariant over changes in the target distance for any single instruction but were all sensitive to the given instruction. 4. Our results demonstrate that the speed-insensitive strategy is a standard or default pattern for performing movements that may be carried out for different instructions over a wide range of speeds. A uniform intensity of excitation pulse is not a byproduct of moving at maximal speed. Submaximal intensities are associated with submaximal speeds and are a selected feature of the pattern of movement control.

Organizing principles for single joint movements: V. Agonist-antagonist interactions

1992 ◽  
Vol 67 (6) ◽  
pp. 1417-1427 ◽  
Author(s):  
G. L. Gottlieb ◽  
M. L. Latash ◽  
D. M. Corcos ◽  
T. J. Liubinskas ◽  
G. C. Agarwal
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Human Subjects ◽  
Single Equation ◽  
Movement Speed ◽  
Joint Movement ◽  
Movement Initiation ◽  
Muscle Activation Patterns ◽  
Movement Distance ◽  
Task Conditions

1. Normal human subjects made discrete elbow flexions in the horizontal plane under different task conditions of initial or final position, inertial loading, or instruction about speed. We measured joint angle, acceleration, and electromyographic signals (EMGs) from two agonist and two antagonist muscles. 2. For many of the experimental tasks, the latency of the antagonist EMG burst was strongly correlated with parameters of the first agonist EMG burst defined by a single equation, expressed in terms of the agonist's hypothetical excitation pulse. Latency is proportional to the ratio of pulse duration to pulse intensity, making it proportional to movement distance and inertial load and inversely proportional to planned movement speed. However, these rules are not sufficient to define the timing of every possible single joint movement. 3. For movements described by the speed-insensitive strategy, the quantity of both antagonist and agonist muscle activity can be uniformly associated with selected kinetic measures that incorporate muscle force-velocity relations. 4. For movements collectively described by the speed-sensitive strategy, (i.e., that have direct or indirect constraints on speed), no single rule can describe all the combinations of agonist-antagonist coordination that are used to perform these diverse tasks. 5. Estimates of joint viscosity were made by calculating the amount of velocity-dependent torque used to terminate movements on target. These estimates are similar to those that have previously been made of limb viscosity during postural maintenance. They imply that a significant component of muscle activity must be used to overcome these forces. 6. These and previous results are all consistent with a dual-strategy hypothesis for those single-joint movements that are sufficiently fast to require pulse-like muscle activation patterns. The major features of such patterns (pulse intensities, durations, and latencies) are determined by central commands programmed in advance of movement initiation. The selection between speed-insensitive or speed-sensitive rules of motoneuron pool excitation is implicitly specified by the nature of speed constraints of the movement task.

Two components of muscle activation: scaling with the speed of arm movement

1992 ◽  
Vol 67 (4) ◽  
pp. 931-943 ◽  
Author(s):  
M. Flanders ◽  
U. Herrmann
Keyword(s):  
Muscle Activation ◽  
Movement Time ◽  
Vertical Plane ◽  
Arm Movement ◽  
Movement Speed ◽  
Weighting Coefficient ◽  
Emg Activity ◽  
Tonic Component ◽  
Force Element ◽  
Weighting Coefficients

1. The temporal waveform of muscle activity was related to the speed of arm movement. Speed was expressed in terms of the duration of a fixed amplitude movement or the "movement time." 2. Human subjects moved their arms to targets in three-dimensional space. The right arm started at a standard initial position and moved directly to the target in a single stroke. The targets were placed in various directions in a vertical plane. The arm movements consisted of shoulder and elbow rotations. 3. Subjects were required to vary the speed of their movements. In most of the experiments, trials with different movement times were randomly ordered. One of the experiments also included randomly interspersed static trials, in which the subject held the arm still at the initial posture, the final posture, or halfway between the two extremes. 4. Electromyographic (EMG) activity was recorded from several superficial elbow and/or shoulder muscles. The time base of rectified EMG records was normalized for movement time such that records from movements with various speeds were compressed to align the ending times of the movements. 5. A principal component (PC) analysis revealed that the compressed EMG waveforms could be described by a summation of PC1 and PC2 waveforms; each individual EMG waveform was approximated by a weighted sum of these two components. 6. The PC1 weighting coefficients scaled down in a monotonic relationship with movement time such that the fastest movement corresponded to a large positive weighting coefficient and the slowest movement corresponded to a small positive weighting coefficient. The PC2 weighting coefficients exhibited a similar monotonic scaling, but the values ranged from positive to negative. Further analysis demonstrated that these two components can be mathematically transformed into a tonic waveform with a constant mathematically transformed into a tonic waveform with a constant weighting coefficient and a phasic waveform with positive weighting coefficients that scale down with movement time. 7. The amplitude scaling of EMG records cannot be described by a single component, but instead requires a summation of two separate components. The tonic component may correspond to the force element needed to counteract gravity, because the magnitude of this element does not scale with movement speed. The phasic component may correspond to the force element that scales quadratically to produce a linear increase in velocity.

Head Movements Produced During Whole Body Rotations and Their Sensitivity to Changes in Head Inertia in Squirrel Monkeys

2008 ◽  
Vol 99 (5) ◽  
pp. 2369-2382 ◽  
Author(s):  
J. S. Reynolds ◽  
G. T. Gdowski
Keyword(s):  
Head Movement ◽  
Muscle Activation ◽  
Human Subjects ◽  
Squirrel Monkeys ◽  
The Body ◽  
Head Movements ◽  
Whole Body ◽  
Movement Kinematics ◽  
Behavioral Studies ◽  
Wide Range

The head's inertia produces forces on the neck when the body moves. One collective function of the vestibulocollic and cervicocollic reflexes (VCR and CCR) is thought to be to stabilize the head with respect to the trunk during whole body movements. Little is known as to whether their head-movement kinematics produced by squirrel monkeys during whole body rotations are similar to those of cats and humans. Prior experiments with cats and human subjects have shown that yaw head-movement kinematics are unaffected by changes in the head's inertia when the whole body is rotated. These observations have led to the hypothesis that the combined actions of the VCR and CCR accommodate for changes in the head's inertia. To test this hypothesis in squirrel monkeys, it was imperative to first characterize the behavior of head movements produced during whole body rotation and then investigate their sensitivity to changes in the head's inertia. Our behavioral studies show that squirrel monkeys produce only small head movements with respect to the trunk during whole body rotations over a wide range of stimulus frequencies and velocities (0.5–4.0 Hz; 0–100°/s). Similar head movements were produced when only small additional changes in the head's inertia occurred. Electromyographic recordings from the splenius muscle revealed that an active process was utilized such that increases in muscle activation occurred when the inertia of the head was increased. These results are consistent with prior cat and human studies, suggesting that squirrel monkeys have a similar horizontal VCR and CCR.

Organizing principles for single-joint movements. IV. Implications for isometric contractions

1990 ◽  
Vol 64 (3) ◽  
pp. 1033-1042 ◽  
Author(s):  
D. M. Corcos ◽  
G. C. Agarwal ◽  
B. P. Flaherty ◽  
G. L. Gottlieb
Keyword(s):  
Pulse Width Modulation ◽  
Human Subjects ◽  
Pulse Height ◽  
Joint Torque ◽  
Isometric Contractions ◽  
Time Interval ◽  
Motoneuron Pool ◽  
Agonist And Antagonist ◽  
Isometric Torque ◽  
Organizing Principles

1. Normal human subjects made isometric pulse and step contractions about the elbow to visually defined target torques of different amplitudes and at different rates. We measured joint torque and electromyograms (EMG) from two agonist and two antagonist muscles. 2. When the task specification requires that the subject explicitly alter the rate at which torque is increased, the rates of rise of the agonist and antagonist EMG bursts covary with the rate of rise of the torque. For pulses of torque the duration of motoneuron excitation varies with the duration of the task-defined contractile event. 3. When a subject is asked to generate torques of different amplitudes without specifying a time interval, torque amplitude is positively correlated with how long, and therefore how high, the EMG rose. Subjects usually proportionately covary the strength of the agonist and antagonist contractions but are not constrained to do so. Some subjects use a strategy of varying the antagonist inversely with the agonist contraction. 4. We extend the organizing principles for the control of movement about a single joint to the control of isometric torque. These rules state that control of torque about a single joint is exercised by one of two strategies: the speed-sensitive strategy modulates the rate at which contraction rises by varying the intensity of motoneuron-pool excitation. The speed-insensitive strategy varies the duration over which contraction rises but does not change the rate. These two respective patterns of torque emerge from pulse-height and pulse-width modulation of motoneuron-pool excitation. 5. The rules defining speed-sensitive and speed-insensitive strategies for movements are broadened for isometric contractions because of the wider range of torque patterns that we observe under these conditions. We propose a step-excitation component for prolonged isometric step contractions and slowly rising ramp patterns of excitation for contractions that develop over several hundreds of milliseconds. 6. The choice of strategies is based on task-specific torque requirements. The same two strategies that control torque to produce movement apply to the control of isometric torque. Unlike movements, however, isometric tasks are more often controlled by a blending of the two patterns. Possible reasons for this are discussed.

Compliance of single joints: elastic and plastic characteristics

1988 ◽  
Vol 59 (3) ◽  
pp. 937-951 ◽  
Author(s):  
G. L. Gottlieb ◽  
G. C. Agarwal
Keyword(s):  
Inflection Point ◽  
Muscle Activation ◽  
Human Subjects ◽  
Equilibrium Points ◽  
Characteristic Curve ◽  
Muscle Tension ◽  
Joint Stiffness ◽  
Elastic Stiffness ◽  
Joint Torque ◽  
Equilibrium Angle

1. Step changes in torque were applied to the elbow or ankle joint of normal human subjects who exerted constant levels of effort. They were instructed to not react to the torque but to allow their limbs to move to a new equilibrium position. In this experimental paradigm, the joint may be characterized by a nonlinear compliant element. The aim of this study was to characterize the elastic properties of the compliant element. 2. Joint elasticity is described by an S-shaped relation between torque and angle (a "compliant characteristic curve"). The stiffness of a joint is greatest for small perturbations and decreases as the size of the perturbation is increased whether the limb is loaded or unloaded from its initial equilibrium. 3. The S shape of the compliant characteristic curve is relatively constant when measured at different initial joint angles from the same initial joint torque. 4. Higher levels of initial muscle torque increase the steepness of the compliant characteristic curve. 5. All changes in initial joint torque and angle preserve the S shape. The inflection point of the characteristic curve is always at the initial equilibrium angle and torque. This shifting of the inflection point of the torque-angle relation implies a fundamental plasticity in joint compliance. The elastic component is not invariant but changes with the joint's initial equilibrium state. 6. Changes in muscle tension and length that result from a perturbation are accompanied by changes in muscle activation. The relationship between perturbation torque and mean equilibrium EMG is similar to that found for voluntary isometric contraction. It is not possible to conclude what proportion of the late EMG response to perturbation is mediated by segmental reflex mechanisms. 7. At the levels of torque used here, changes in joint stiffness are highly correlated with changes in tonic contraction of the muscle opposing the load. This change in stiffness is not the result of antagonist coactivation, which was minimal. 8. The compliant characteristic curves of elbow and ankle are qualitatively similar. The principal difference is due to the greater passive stiffness of the ankle. 9. Our findings are inconsistent with aspects of the theory of invariant characteristics or with models of movement and load compensation that postulate a control scheme based only on the setting of muscle and reflex equilibrium points. The data are also incompatible with models that only control the elastic stiffness of the muscle.

Muscle Activation Patterns During Two Types of Voluntary Single-Joint Movement

1998 ◽  
Vol 80 (4) ◽  
pp. 1860-1867 ◽  
Author(s):  
Gerald L. Gottlieb
Keyword(s):  
Muscle Activation ◽  
Human Subjects ◽  
Silent Period ◽  
Initial Position ◽  
Joint Movement ◽  
Flexor Muscle ◽  
Activation Patterns ◽  
Muscle Torque ◽  
Muscle Activation Patterns ◽  
Emg Patterns

Gottlieb, Gerald L. Muscle activation patterns during two types of voluntary single-joint movement. J. Neurophysiol. 80: 1860–1867, 1998. We examined the systematic variations in the EMG patterns during two types of single joint elbow movements. These patterns may be interpreted as exhibiting rules by which the CNS controls movement parameters. Normal human subjects performed two series of fast elbow flexion movements of 20–100° in a horizontal plane manipulandum. The first series consisted of pointing movements (PMs) from an initial position to a target; the second series consisted of reversal movements (RMs) to the same targets with an immediate return to the starting position. Both series showed kinematic and electromyographic (EMG) patterns that followed our previously described speed-insensitive strategy for controlling movement distance. Kinematic patterns of PMs and RMs were identical to about the time of peak PM deceleration. Agonist EMG bursts were also initially the same, but RM bursts ended abruptly in a silent period, whereas PM bursts declined more gradually. Antagonist EMG bursts of RMs were later than those of PMs but were not larger, contrary to our prior expectation and despite the larger net extension torque during RMs. The increase in net RM extension-directed torque that takes the limb back to its initial position appears to be a consequence of reduced flexor muscle torque rather than increased extensor muscle torque. We propose that rules for movement control may be similar for different kinds of movements as long as they are functionally sufficient for the task. However, even in a single-joint movement paradigm, physics alone, that is, the knowledge of net muscle torque and limb kinematics, is not adequate to fully predict those rules or the muscle activation patterns they produce. These must be discovered by experiment. The simplest expression of such rules may not be in terms of torque or kinematic variables but rather explicitly in terms of muscle activation patterns.

Task dependent patterns of muscle activation at the shoulder and elbow for unconstrained arm movements

1994 ◽  
Vol 71 (3) ◽  
pp. 1261-1265 ◽  
Author(s):  
D. A. Hong ◽  
D. M. Corcos ◽  
G. L. Gottlieb
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Elbow Flexion ◽  
Joint Torque ◽  
Movement Speed ◽  
Elbow Extension ◽  
Joint Angles ◽  
The Third ◽  
Shoulder Muscles ◽  
Shoulder Flexion

1. Six subjects performed three series of pointing tasks with the unconstrained arm. Series one and two required subjects to move as fast as possible with different weights attached to the wrist. The first required flexion at both shoulder and elbow joints. The second required shoulder flexion and elbow extension. The third series required flexion at both joints and subjects were intentionally instructed to vary movement speed. These three pointing tasks were selected as the simplest progression from single to multiple degree of freedom movements in which different patterns of motoneuron excitation are required depending on whether movements are made against different loads or at different intended speeds. 2. Changes in load and changes in intended speed both produced systematic but different changes in the patterns of muscle activity and joint torque in both the elbow and shoulder muscles. These patterns are the same found during constrained, single-joint elbow flexion movements. The changes are expressed in the rates of rise, durations, and latencies of the electromyographic (EMG) bursts and in the rates of rise of torque that have specific dependencies based on the force requirements of the task. 3. A consistent, almost linear relationship is observed between muscle torque at the shoulder and at the elbow for all three tasks. Similar systematic changes were not seen in the kinematic description of joint angles.(ABSTRACT TRUNCATED AT 250 WORDS)

scholarly journals Antagonist Muscle Co-Activation during Kettlebell Single Arm Swing Exercise

2021 ◽  
Vol 11 (9) ◽  
pp. 4033
Author(s):  
Ahmed Salem ◽  
Amr Hassan ◽  
Markus Tilp ◽  
Abdel-Rahman Akl
Keyword(s):  
Muscle Activation ◽  
Surface Emg ◽  
Antagonist Muscle ◽  
Arm Swing ◽  
Shoulder Muscles ◽  
Antagonist Muscles ◽  
Co Activation ◽  
Integrated Emg ◽  
Post Hoc ◽  
Electrical Muscle

The purpose of this study was to determine the muscle activation and co-activation of selected muscles during the kettlebell single arm swing exercise. To the best of our knowledge, this is the first study investigating the muscle co-activation of a kettlebell single arm swing exercise. Nine volunteers participated in the present study (age: 22.6 ± 3.8 years; body mass: 80.4 ± 9.2 kg; height: 175.6 ± 7.5 cm). The electrical muscle activity of eight right agonist/antagonist muscles (AD/PD, ESL/RA, ESI/EO, and GM/RF) were recorded using a surface EMG system (Myon m320RX; Myon, Switzerland) and processed using the integrated EMG to calculate a co-activation index (CoI) for the ascending and descending phases. A significant effect of the ascending and descending phases on the muscles’ CoI was observed. Post hoc analyses showed that the co-activation was significantly higher in the descending phase compared to that in the ascending phase of AD/PD CoI (34.25 ± 18.03% and 24.75 ± 13.03%, p < 0.001), ESL/RA CoI (34.97 ± 17.86% and 24.19 ± 10.32%, p < 0.001), ESI/EO CoI (41.14 ± 10.72% and 30.87 ± 11.26%, p < 0.001), and GM/RF CoI (27.49 ± 12.97% and 34.98 ± 14.97%, p < 0.001). In conclusion, the co-activation of the shoulder muscles varies within the kettlebell single arm swing. The highest level of co-activation was observed in the descending phase of AD/PD and GM/RF CoI, and the lowest level of co-activation was observed during the descending phase, ESL/RA and ESI/EO CoI. In addition, the highest level of co-activation was observed in the ascending phase of ESL/RA and ESI/EO CoI, and the lowest level of co-activation was observed during the ascending phase, AD/PD and GM/RF CoI. The co-activation index could be a useful method for the interpretation of the shoulder and core muscles’ co-activity during a kettlebell single arm swing.

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