Optimal Elbow Angle for Extraction of sEMG and MMG Signals During Dynamic Fatiguing Contractions

Presynaptic modulation of Ia afferents converging onto the motor neuron pool of the extensor carpi radialis (ECR) was compared during contractions (20% of maximal force) sustained to failure as subjects controlled either the angular position of the wrist while supporting an inertial load (position task) or exerted an equivalent force against a rigid restraint (force task). Test Hoffmann (H) reflexes were evoked in the ECR by stimulating the radial nerve above the elbow. Conditioned H reflexes were obtained by stimulating either the median nerve above the elbow or at the wrist (palmar branch) to assess presynaptic inhibition of homonymous (D1 inhibition) and heteronymous Ia afferents (heteronymous Ia facilitation), respectively. The position task was briefer than the force task ( P = 0.001), although the maximal voluntary force and electromyograph for ECR declined similarly at failure for both tasks. Changes in the amplitude of the conditioned H reflex were positively correlated between the two conditioning methods ( P = 0.02) and differed between the two tasks ( P < 0.05). The amplitude of the conditioned H reflex during the position task first increased (129 ± 20.5% of the initial value, P < 0.001) before returning to its initial value ( P = 0.22), whereas it increased progressively during the force task to reach 122 ± 17.4% of the initial value at failure ( P < 0.001). Moreover, changes in conditioned H reflexes were associated with the time to task failure and force fluctuations. The results suggest a task- and time-dependent modulation of presynaptic inhibition of Ia afferents during fatiguing contractions.

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Motor Programs as Indicators of Penalty Direction in Soccer

International Journal for Innovation Education and Research ◽

10.31686/ijier.vol8.iss9.2619 ◽

2020 ◽

Vol 8 (9) ◽

pp. 224-233

Author(s):

Luiz Felipe Pinto Oliveira da Motta ◽

Ricardo Fontes Macedo ◽

Elizabeth Cárpio Rivera ◽

Angela Luciana De-Bortoli ◽

Robelius De-Bortoli

Keyword(s):

Behavior Pattern ◽

Video Camera ◽

The Body ◽

Motor Patterns ◽

Motor Programs ◽

Front View ◽

Elbow Angle ◽

Patterns Of Behavior ◽

Prior Intention ◽

Leg Position

Introduction: Many football games are decided on penalties and usually in championship final games. When seeking to anticipate movements, differences in amplitude can harm players because the informational movement appears to be spread "globally" throughout the action and should be coded at several levels. Thus, it would be interesting to analyze the entire period of the kick, since the player begins his run to approach the ball to recognize the motor patterns used in the kick that identify his direction. Objective: The objective of this study is to identify patterns of behavior in penalty kicks that may indicate the direction of their action / kick and in my moment they appear. Methodology: The sample consisted of 21 subjects hitting a penalty kick, 18 males and 3 females with an average age of 22.18 ± 2.44 years and two goalkeepers with college football experience. The tests consisted of a battery of two penalty kicks for each subject in order to score. The kicks were recorded by a video camera with a front view of the goal goal and the back of the batter. The kick phases were divided into the starting leg position; first step leg; angle of the elbow in relation to the body seen from behind; angle of the elbow in relation to the displacement line seen from above; direction of the tip of the supporting foot and position on the goal where the kick was. Each kick was preceded by a start signal. The data were analyzed from the registration of each variable and the position of the goal in which the ball was kicked, considering it in three sectors: left, right and central. Results: The main results indicated that the variable “Leg of the first step” had 81% of the kicks associated with the direction of the goal; 52.4% of second kicks had repeated the pattern of behavior and 84.6% had repeated the pattern of behavior regardless of the goal position. The variable “Elbow angle in relation to the body seen from behind” had 81.8% repeated behavior pattern regardless of the goal position and the variable “Elbow angle in relation to the displacement line seen from above” had 81% association with the sector of the goal in which the ball was kicked; 52.4% of second kicks had repeated the pattern of behavior and 91.7% had repeated the pattern of behavior regardless of the goal position. Conclusions: The main conclusions indicate that it is possible to relate the kick location with the batter's body information; the start of the race seems to indicate that there is a prior intention of movement programs; the decision of where to hit the penalty appears to be made before contact with the ball and more closely to the placement of the support foot and with this relationship, the size of the goal to be defended by the goalkeeper could be reduced, increasing the possibility of defense.

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Short Segmental Motor Conduction Studies of Ulnar Nerve at the Elbow according to Different Elbow Angle

Jouranl of Korean Association of EMG Electrodiagnostic Medicine ◽

10.18214/jkaem.2008.10.1.22 ◽

2008 ◽

Vol 10 (1) ◽

pp. 22-27

Author(s):

변승득 ◽

김태건 ◽

김철현 ◽

신오수 ◽

권순모

Keyword(s):

Ulnar Nerve ◽

Elbow Angle

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Task Differences With the Same Load Torque Alter the Endurance Time of Submaximal Fatiguing Contractions in Humans

Journal of Neurophysiology ◽

10.1152/jn.00232.2002 ◽

2002 ◽

Vol 88 (6) ◽

pp. 3087-3096 ◽

Cited By ~ 118

Author(s):

Sandra K. Hunter ◽

Daphne L. Ryan ◽

Justus D. Ortega ◽

Roger M. Enoka

Keyword(s):

Mean Arterial Pressure ◽

Arterial Pressure ◽

Elbow Flexor ◽

Emg Activity ◽

Load Torque ◽

Endurance Time ◽

Position Task ◽

Flexor Muscles ◽

Elbow Flexor Muscles ◽

Fatiguing Contractions

Endurance time, muscle activation, and mean arterial pressure were measured during two types of submaximal fatiguing contractions that required each subject to exert the same net muscle torque in the two tasks. Sixteen men and women performed isometric contractions at 15% of the maximum voluntary contraction (MVC) force with the elbow flexor muscles, either by maintaining a constant force while pushing against a force transducer (force task) or by supporting an equivalent inertial load while maintaining a constant elbow angle (position task). The endurance time for the force task (1402 ± 728 s) was twice as long as that for the position task (702 ± 582 s, P < 0.05), despite a similar reduction in the load torque at exhaustion for each contraction. The rate of increase in average electromyographic activity (EMG, % peak MVC value) for the elbow flexor muscles was similar for the two tasks. However, the average EMG was greater at exhaustion for the force task (22.4 ± 1.2%) compared with the position task (14.9 ± 1.0%, P < 0.05). In contrast, the rates of increase in the mean arterial pressure, the rating of perceived exertion, anterior deltoid EMG, and fluctuations in motor output (force or acceleration) were greater for the position task compared with the force task ( P < 0.05). Furthermore, the rate of bursts in EMG activity, which corresponded to the transient recruitment of motor units, was greater for the brachialis muscle during the position task. These results indicate that the briefer endurance time for the position task was associated with greater levels of excitatory and inhibitory input to the motor neurons compared with the force task.

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