scholarly journals Modulation of Stretch Reflexes of the Finger Flexors by Sensory Feedback From the Proximal Upper Limb Poststroke

2009 ◽  
Vol 102 (3) ◽  
pp. 1420-1429 ◽  
Author(s):  
Gilles Hoffmann ◽  
Derek G. Kamper ◽  
Jennifer H. Kahn ◽  
William Z. Rymer ◽  
Brian D. Schmit
Keyword(s):  
Upper Limb ◽  
Stretch Reflex ◽  
Sensory Input ◽  
Biceps Brachii ◽  
Elbow Flexion ◽  
Spinal Reflex ◽  
Reflex Response ◽  
Emg Activity ◽  
Triceps Brachii ◽  
Flexor Digitorum

Neural coupling of proximal and distal upper limb segments may have functional implications in the recovery of hemiparesis after stroke. The goal of the present study was to investigate whether the stretch reflex response magnitude of spastic finger flexor muscles poststroke is influenced by sensory input from the shoulder and the elbow and whether reflex coupling of muscles throughout the upper limb is altered in spastic stroke survivors. Through imposed extension of the metacarpophalangeal (MCP) joints, stretch of the relaxed finger flexors of the four fingers was imposed in 10 relaxed stroke subjects under different conditions of proximal sensory input, namely static arm posture (3 different shoulder/elbow postures) and electrical stimulation (surface stimulation of biceps brachii or triceps brachii, or none). Fast (300°/s) imposed stretch elicited stretch reflex flexion torque at the MCP joints and reflex electromyographic (EMG) activity in flexor digitorum superficialis. Both measures were greatest in an arm posture of 90° of elbow flexion and neutral shoulder position. Biceps stimulation resulted in greater MCP stretch reflex flexion torque. Fast imposed stretch also elicited reflex EMG activity in nonstretched heteronymous upper limb muscles, both proximal and distal. These results suggest that in the spastic hemiparetic upper limb poststroke, sensorimotor coupling of proximal and distal upper limb segments is involved in both the increased stretch reflex response of the finger flexors and an increased reflex coupling of heteronymous muscles. Both phenomena may be mediated through changes poststroke in the spinal reflex circuits and/or in the descending influence of supraspinal pathways.

Mind-Muscle Connection: Verbal Instructions Alter Electromyographic Activity for Elbow Flexors and Extensors During Co-Contraction Training

2020 ◽  
pp. 003151252094908
Author(s):  
Rafael A. Fujita ◽  
Marina M. Villalba ◽  
Nilson R. S. Silva ◽  
Matheus M. Pacheco ◽  
Matheus M. Gomes
Keyword(s):  
Strength Training ◽  
Elbow Joint ◽  
Biceps Brachii ◽  
Elbow Flexion ◽  
Emg Activity ◽  
Elbow Extension ◽  
Verbal Instruction ◽  
Triceps Brachii ◽  
Verbal Instructions ◽  
Lateral Head

Co-contraction training has demonstrated similar electromyographic (EMG) activity levels compared to conventional strength training. Since verbal instructions can increase EMG activity on target muscles during conventional exercises, the same should occur during co-contraction. In this study we analyzed whether different verbal instructions would alter the EMG activity of target muscles - biceps brachii (BB) and triceps brachii lateral head (TB) - during co-contraction training for the elbow joint. Seventeen males with experience in strength training performed a co-contraction set in two verbal instruction conditions to emphasize either elbow flexion or elbow extension. Surface electrodes were fixed over biceps brachii and triceps brachii lateral head muscles. We measured EMG mean amplitude and analyzed data with 2-way ANOVA. We found a significant interaction between muscle and verbal instruction ( p = 0.002). Post hoc tests indicated that verbal instructions ( p = 0.001) influenced the BB EMG activity (elbow flexion: M = 68.74, SD = 17.96%; elbow extension: M = 53.47, SD = 16.13%); and also showed difference ( p = 0.006) in the EMG activity between BB and TB with verbal instruction emphasizing the elbow extension (BB: M = 53.47, SD = 16.13%; TB: M = 69.18, SD = 21.79%). There was a difference in the EMG ratio of BB/TB ( p = 0.001) when focusing on elbow flexion ( M = 1.09, SD = 0.30) versus elbow extension ( M = 0.81, SD = 0.25). As verbal instruction modified the magnitude of muscle recruitment during co-contractions for elbow joint muscles, there is a clear mind-muscle connection of importance to this method of training. Also, of importance to trainers, verbal instructions seemed to affect individuals differentially.

Emg and Motor Performance Changes with Practice of a Forearm Movement by Children

1988 ◽  
Vol 67 (2) ◽  
pp. 523-529 ◽  
Author(s):  
Richard Engelhorn
Keyword(s):  
Motor Performance ◽  
Biceps Brachii ◽  
Movement Time ◽  
Age Groups ◽  
Elbow Flexion ◽  
Emg Activity ◽  
Practice Session ◽  
Triceps Brachii ◽  
Movement Velocity ◽  
Time To Peak

The purpose of this research was to investigate changes in the control of movement, using EMG and kinematic variables, over practice by children. Children in three age groups, 7, 9, and 11 yr., performed 60 trials of an elbow-flexion movement. Correct movements consisted of a 60° angular movement of the forearm in 800 msec. The analysis of biceps brachii and triceps brachii muscle EMG activity, movement displacement and timing error, and movement velocity patterns indicated changes in motor performance with practice. All age groups improved performance with practice and also exhibited a decrease in biceps EMG activity with practice. Only movement-time error and time to peak triceps muscle activity differed between the age groups. The 11-yr.-old group significantly altered the timing of the antagonistic response to stop the movement over the practice session. This change is suggested to be related to the greater information-processing ability of these children and the development of appropriate movement strategies to perform the movement task successfully. Other changes observed in the EMG data appear similar to changes observed in studies of adults.

Strategies for muscle activation during isometric torque generation at the human elbow

1989 ◽  
Vol 62 (6) ◽  
pp. 1201-1212 ◽  
Author(s):  
T. S. Buchanan ◽  
G. P. Rovai ◽  
W. Z. Rymer
Keyword(s):  
Muscle Activation ◽  
Biceps Brachii ◽  
Human Subjects ◽  
Elbow Flexion ◽  
Emg Activity ◽  
Elbow Extension ◽  
Triceps Brachii ◽  
Pronator Teres ◽  
Flexion Extension ◽  
Torque Generation

1. We studied the patterns of electromyographic (EMG) activity in elbow muscles of 14 normal human subjects. The activity of five muscles that act in flexion-extension and forearm supination-pronation was simultaneously recorded during isometric voluntary torque generation, in which torques generated in a plane orthogonal to the long axis of the forearm were voluntarily coupled with torques generated about the long axis of the forearm (i.e., supination-pronation). 2. When forearm supination torques were superimposed on a background of elbow flexion torque, biceps brachii activity increased substantially, as expected; however, brachioradialis and brachialis EMG levels decreased modestly, a less predictable outcome. The pronator teres was also active during pure flexion and flexion coupled with mild supination (even though no pronation torque was required). This was presumably to offset inappropriate torque contributions of other muscles, such as the biceps brachii. 3. When forearm supination torque was superimposed on elbow extension torque, again the biceps brachii was strongly active. The pronator teres also became mildly active during extension with added pronation torque. These changes occurred despite the fact that both the pronator and biceps muscles induce elbow flexion. 4. In these same elbow extension tasks, triceps brachii activity was also modulated with both pronation or supination loads. It was most active during either supination or pronation loads, again despite the fact that it has no mechanical role in producing forearm supination-pronation torque. 5. Recordings of EMG activity during changes in forearm supination-pronation angle demonstrated that activation of the biceps brachii followed classic length-tension predictions, in that less EMG activity was required to achieve a given supination torque when the forearm was pronated (where biceps brachii is relatively longer). On the other hand, EMG activity of the pronator teres did not decrease when the pronator was lengthened. Triceps EMG was also more active when the forearm was supinated, despite its having no direct functional role in this movement. 6. Plots relating EMG activity in biceps brachii, brachialis, and brachioradialis at three different forearm positions revealed that there was a consistent positive near-linear relationship between brachialis and brachioradialis and that biceps brachii is often most active when brachioradialis and brachialis are least active. 7. We argue that, for the human elbow joint at least, fixed muscle synergies are rather uncommon and that relationships between muscle activities are situation dependent.(ABSTRACT TRUNCATED AT 400 WORDS)

scholarly journals The Effects of Bench Press Variations in Competitive Athletes on Muscle Activity and Performance

2017 ◽  
Vol 57 (1) ◽  
pp. 61-71 ◽  
Author(s):  
Atle Hole Saeterbakken ◽  
Dag-André Mo ◽  
Suzanne Scott ◽  
Vidar Andersen
Keyword(s):  
Muscle Activity ◽  
Latissimus Dorsi ◽  
Bench Press ◽  
Biceps Brachii ◽  
High Load ◽  
Emg Activity ◽  
International Level ◽  
Triceps Brachii ◽  
Competitive Athletes ◽  
And Performance

AbstractThe aim of the study was to compare the EMG activity performing 6RM competition style bench press (flat bench-wide grip) with 1) medium and narrow grip widths on a flat bench and 1) inclined and declined bench positions with a wide grip. Twelve bench press athletes competing at national and international level participated in the study. EMG activity was measured in the pectoralis major, anterior and posterior deltoid, biceps brachii, triceps brachii and latissimus dorsi. Non-significant differences in activation were observed between the three bench positions with the exception of 58.5-62.6% lower triceps brachii activation, but 48.3-68.7% greater biceps brachii activation in the inclined bench compared with the flat and declined bench position. Comparing the three grip widths, non-significant differences in activations were observed, with the exception of 25.9-30.5% lower EMG activity in the biceps brachii using a narrow grip, compared to the medium and wide grip conditions. The 6-RM loads were 5.8-11.1% greater using a medium and wide grip compared to narrow grip width and 18.5-21.5% lower in the inclined bench position compared with flat and declined. Comparing the EMG activity during the competition bench press style with either the inclined and declined bench position (wide grip) or using a narrow and medium grip (flat bench), only resulted in different EMG activity in the biceps- and triceps brachii. The 6RM loads varied with each bench press variation and we recommend the use of a wide grip on a flat bench during high load hypertrophy training to bench press athletes.

Heteronymous reflex connections in human upper limb muscles in response to stretch of forearm muscles

2011 ◽  
Vol 106 (3) ◽  
pp. 1489-1499 ◽  
Author(s):  
Curtis D. Manning ◽  
Parveen Bawa
Keyword(s):  
Upper Limb ◽  
Biceps Brachii ◽  
Monosynaptic Reflex ◽  
Electromyographic Activity ◽  
Response Patterns ◽  
Triceps Brachii ◽  
Limb Muscles ◽  
Abductor Digiti Minimi ◽  
Human Upper Limb ◽  
Wrist Flexors

Torque motor produced stretch of upper limb muscles results in two distinct reflex peaks in the electromyographic activity. Whereas the short-latency reflex (SLR) response is mediated largely by the spinal monosynaptic reflex pathway, the longer-latency reflex (LLR) is suggested to involve a transcortical loop. For the SLRs, patterns of heteronymous monosynaptic Ia connections have been well-studied for a large number of muscles in the cat and in humans. For LLRs, information is available for perturbations to proximal joints, although the protocols for most of these studies did not focus on heteronymous connections. The main objective of the present study was to elicit both SLRs and LLRs in wrist flexors and extensors and to examine heteronymous connections from these muscles to elbow flexors (biceps brachii; BiBr) and extensors (triceps brachii; TriBr) and to selected distal muscles, including abductor pollicis longus (APL), first dorsal interosseous (FDI), abductor digiti minimi (ADM), and Thenars. The stretch of wrist flexors produced SLR and LLR peaks in APL, FDI, ADM, Thenars, and BiBr while simultaneously inducing inhibition of wrist extensors and TriBr. When wrist extensors were stretched, SLR and LLR peaks were observed in TriBr, whereas the primary wrist flexors, APL and BiBr, were inhibited; response patterns of FDI, ADM, and Thenars were less consistent. The main conclusions from the observed data are that: 1) as in the cat, afferents from wrist flexors and extensors make heteronymous connections with proximal and distal upper limb muscles; and 2) the strength of heteronymous connections is greater for LLRs than SLRs in the distal muscles, whereas the opposite is true for the proximal muscles. In the majority of observations, SLR and LLR excitatory peaks were observed together. However, on occasion, LLRs were observed without the SLR response in hand muscles when wrist extensors were stretched.

scholarly journals Effects of Sampling Frequency and Sample Window Size on Median Frequency of Surface EMG

2019 ◽  
Vol 63 (1) ◽  
pp. 1369-1372
Author(s):  
Pramiti Sarker ◽  
Gary Mirka
Keyword(s):  
Biceps Brachii ◽  
Window Size ◽  
Elbow Flexion ◽  
Surface Emg ◽  
Sampling Frequency ◽  
Emg Activity ◽  
Median Frequency ◽  
Surface Electrodes ◽  
Emg Signal ◽  
Sample Window

Muscle fatigue can be evaluated through the assessment of the downward shift in the median frequency (MDF) of the electromyographic (EMG) signal collected through surface electromyography. Previous research has shown that the value of MDF may be affected by sampling parameters. The purpose of this study was to quantify the combined effect of different sampling frequencies and window sizes on the calculated MDF. A sample of 24 participants performed a simple static elbow flexion exertion (15% MVC) and the EMG activity of the biceps brachii was periodically sampled using surface electrodes for four seconds at a frequency of 4096 Hz as the biceps brachii became fatigued. These collected data were then down-sampled to create a dataset of four window sizes (1s, 2s, 3s, and 4s) and five sampling frequencies (256 Hz, 512 Hz, 1024 Hz, 2048 Hz, and 4096 Hz). Median frequencies were calculated for each combination of sampling frequency and window size and then compared with the 4096 Hz / 4 s condition (considered gold standard) and the errors were calculated. Results suggest the use of a minimum sampling frequency of 512 Hz and a window size of 4s.

PATTERNS AND CONSISTENCY OF MUSCLE RECRUITMENT FOR A KARATE JAB

2011 ◽  
Vol 23 (01) ◽  
pp. 75-82 ◽  
Author(s):  
Yu-Lin Ning ◽  
Jia-Da Li ◽  
Wei-Ching Lo ◽  
Chih-Hung Huang ◽  
Chu-Fen Chang ◽  
...  
Keyword(s):  
Upper Limb ◽  
Muscle Activation ◽  
Biceps Brachii ◽  
Erector Spinae ◽  
Lower Limbs ◽  
Medial Gastrocnemius ◽  
Muscle Recruitment ◽  
Triceps Brachii ◽  
Motor Time ◽  
Karate Athletes

Adequate pattern and consistency of the muscle recruitment is essential to symbolize the destruction of the opponent with high movement velocities and precise targeting of the opponent's head and body during a karate jab. The purpose of this study was to evaluate the reaction time (RT), motor time (MT), and total response time (TRT), as well as their correlation during a karate jab, and to investigate the recruitment pattern and consistency of muscles during motor time. As many as 14 professional karate athletes (age: 23.67 ± 2.64 years; height: 174.57 ± 7.13 cm; and weight: 72.75 ± 10.65 kg) participated in the current study. Each subject was instructed to pose in combat stance first and then to use their left hand to jab at an instrumented kicking target as soon as they saw the start signal. Surface electromyograms (EMGs) were recorded from 16 muscles, namely the pronator teres, biceps brachii, triceps brachii, and deltoid of the left upper limb, right erector spinae, left rectus abdominis, and gluteus maximus, rectus femoris, biceps femoris, tibialis anterior, and medial gastrocnemius of the right and left lower limbs. Start and stop signals from the instrumented target were also recorded synchronously to obtain the TRT. Significant correlation between MT and TRT indicated that MT was a key determinant for the TRT of the jab. When performing a karate jab, the karate athletes initiated the movement with postural adjustments of the legs and trunk prior to the onset of the voluntary jab by the upper limb, and with a proximal-to-distal sequence of muscle activation in the left arm. Good consistencies of muscle recruitment of the trunk, left arm, and leg, and cocontraction of the left triceps and biceps brachii also indicated a well-controlled jab by the left arm. These results provide important information on the patterns and the consistencies of the muscle recruitment for coaching a karate jab, which should be helpful for a better understanding of the motor control strategies of a karate jab and for developing a suitable training protocol.

Knowledge of Repetition Range Does Not Affect Maximal Force Production Strategies of Adolescent Females

2017 ◽  
Vol 29 (1) ◽  
pp. 109-115 ◽  
Author(s):  
Jonathan C. Reid ◽  
Rebecca M. Greene ◽  
Nehara Herat ◽  
Daniel D. Hodgson ◽  
Israel Halperin ◽  
...  
Keyword(s):  
Biceps Brachii ◽  
Force Production ◽  
Adolescent Females ◽  
Emg Activity ◽  
Triceps Brachii ◽  
Pacing Strategies ◽  
Physiological Reserve ◽  
Random Crossover ◽  
Voluntary Contractions ◽  
Impulse Force

Purpose:Contrary to adult force reserve strategies, it is not known whether adolescent females with less experience performing maximal voluntary contractions (MVC) have specific responses to a known or unknown fatigue endpoint. Methods:Using a counterbalanced random crossover design, fourteen inexperienced female adolescents completed three elbow flexor (EF) fatiguing protocols. Participants were randomly assigned to a control (informed they would perform 12 MVCs), unknown (not informed of the number of MVCs to be completed, but stopped after 12) or deception condition (instructed to complete 6 MVCs, however, after the sixth repetition performed another 6 MVCs). Before and during the interventions, EF impulse, force, and biceps brachii (BB) and triceps brachii (TB) electromyography (EMG) activity were recorded. Results: Participants exhibited decreases in impulse (10.9%; p < .05), force (7.5%; p = .001), BB (16.2%; p < .05) and TB (12.9%; p < .05) EMG activity between the pretest and the first repetition of all protocols. Knowledge of endpoint, or lack of it, did not change measures with the repeated MVCs. When informed about the final repetition, force remained depressed suggesting no physiological reserve. Conclusion:Adolescent females exhibited an anticipatory response to the task of performing repeated MVCs. A lack of change with knowledge of endpoint indicates that those lacking in MVC experience do not employ the same pacing strategies as in previous studies of participants with MVC experience.

Kinematics, Kinetics, and Muscle Activation during Explosive Upper Body Movements

1996 ◽  
Vol 12 (1) ◽  
pp. 31-43 ◽  
Author(s):  
Robert U. Newton ◽  
William J. Kraemer ◽  
Keijo Häkkinen ◽  
Brendan J. Humphries ◽  
Aron J. Murphy
Keyword(s):  
Muscle Activation ◽  
Biceps Brachii ◽  
Average Power ◽  
Upper Body ◽  
Emg Activity ◽  
Neural Activation ◽  
Loading Conditions ◽  
Force Output ◽  
Triceps Brachii ◽  
Average Force

The aim of this study was to investigate the kinematics, kinetics, and neural activation of the traditional bench press movement performed explosively and the explosive bench throw in which the barbell was projected from the hands. Seventeen male subjects completed three trials with a bar weight of 45% of the subject's previously determined 1RM. Performance was significantly higher during the throw movement compared to the press for average velocity, peak velocity, average force, average power, and peak power. Average muscle activity during the concentric phase for pectoralis major, anterior deltoid, triceps brachii, and biceps brachii was higher for the throw condition. It was concluded that performing traditional press movements rapidly with light loads does not create ideal loading conditions for the neuromuscular system with regard to explosive strength production, especially in the final stages of the movement, because ballistic weight loading conditions where the resistance was accelerated throughout the movement resulted in a greater velocity of movement, force output, and EMG activity.

Effect of Reaction Time Condition on EMG Activities of the Biceps Brachii Muscle in Elbow Flexion and Forearm Supination

1988 ◽  
Vol 67 (3) ◽  
pp. 807-813
Author(s):  
Jose Alvin P. Mojica ◽  
Ryuichi Nakamura ◽  
Yoshiaki Yamada ◽  
Ichiro Tsuji
Keyword(s):  
Biceps Brachii ◽  
Elbow Flexion ◽  
Emg Activity ◽  
Biceps Brachii Muscle ◽  
Response Uncertainty ◽  
Motor Set ◽  
Temporal And Spatial ◽  
Temporal And Spatial Characteristics ◽  
Spatial Specificity ◽  
Simple Rt

Under simple- and choice-RT conditions, the biceps brachii muscle was examined in 8 healthy male subjects to determine how the temporal and spatial characteristics of elbow flexion and forearm supination differed at the initial phase of EMG activity and whether preparation or the presence of response uncertainty influenced the EMG outputs of the two movements. In the simple-RT condition, RT of supination was significantly faster than that of flexion but EMG activity of supination was less than that of flexion. In contrast, in the choice-RT condition, RT of flexion was significantly faster than that of supination but EMG activity of flexion was significantly reduced compared to supination. These findings indicate that advanced preparation or motor set facilitates the differentiation of RTs and EMG activities of the response movements and that response uncertainty causes a significant change in the temporal and spatial specificity of both elbow flexion and forearm supination.

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