Muscle synergies and isometric torque production: influence of supination and pronation level on elbow flexion

1993 ◽  
Vol 70 (3) ◽  
pp. 947-960 ◽  
Author(s):  
J. C. Jamison ◽  
G. E. Caldwell
Keyword(s):  
Biceps Brachii ◽  
Muscular Activity ◽  
Elbow Flexion ◽  
Normal Subjects ◽  
Analysis Of Covariance ◽  
Triceps Brachii ◽  
Emg Amplitude ◽  
Task Effects ◽  
Long Head ◽  
The Relationship

1. Twenty normal subjects performed a series of isometric elbow flexion (F) maximum voluntary contractions (MVC) while simultaneously maintaining one of seven targeted torque levels in the supination/pronation (S/P) degree of freedom (df). Experimental measures were torque in both df s and surface electromyograms (EMG) from brachioradialis (BRAD), triceps brachii (TB), biceps brachii (BB) short head (BBSH), and a medial and lateral site on biceps brachii long head (MED BB and LAT BB). Task effects were tested for significance using analysis of covariance models for the torque and EMG variables. Polynomial multiple regression models were developed for significant effects. The synergism among muscles was examined by statistically testing the EMG data for differing responses to the S/P torque changes across the five electrode sites. 2. The magnitude of the S/P target torque had a statistically significant effect on flexion MVC (F MVC) torque. Changes in S/P torque markedly influenced the F MVC torque magnitude, with as much as a 25% F torque decrement relative to an F MVC with an S/P torque target of 0. This suggests that the second df task affects some aspect of joint function that causes the CNS to reduce F torque capacity. 3. The S/P torque had a significant effect on EMG amplitude at all electrode sites other than TB. The EMG amplitude at the BB sites responded strongly to both F and S/P torque changes. The F+S tasks tended to facilitate BB EMG, whereas the F+P tasks tended to diminish it. The BRAD EMG, although primarily related to F torque amplitude, also was influenced by the S/P torque changes. The trends for BRAD EMG were opposite those for the BB in that BRAD EMG tended to be enhanced by the F+P tasks and reduced by the F+S tasks. 4. The synergistic pattern of stimulation (i.e., the relationship among the 5 EMG amplitude measures) was also significantly influenced by the S/P df task. Significant differences in the EMG behavior between BBSH and LAT BB were detected; however, no statistically significant differences were found between LAT BB and MED BB. The EMG behaviors at the BRAD and TB electrode sites were significantly different from those at the BB sites. 5. These inversely related responses from the BB and BRAD stress the importance of understanding the relationship between muscular activity and the function of muscles in more than one df. This finding further suggests that the synergistic relationships between muscles are dynamically related to task in all applicable dfs. It is suggested that this dynamic synergism is a natural consequence of the redundant musculoskeletal system.(ABSTRACT TRUNCATED AT 400 WORDS)

Muscle-fiber pennation angles are greater in hypertrophied than in normal muscles

1993 ◽  
Vol 74 (6) ◽  
pp. 2740-2744 ◽  
Author(s):  
Y. Kawakami ◽  
T. Abe ◽  
T. Fukunaga
Keyword(s):  
Muscle Fiber ◽  
Muscle Thickness ◽  
Normal Subjects ◽  
Muscle Size ◽  
Triceps Brachii ◽  
Human Cadavers ◽  
Long Head ◽  
The Relationship ◽  
Male Subjects

Muscle-fiber pennation angles were measured in vivo with the use of ultrasonography to investigate the relationship between fiber pennation and muscle size for 32 male subjects (from untrained subjects to highly trained bodybuilders). From the image of a B-mode ultrasonogram, fiber pennation angles and thickness of triceps brachii were determined, the former as angles between echoes from the interspaces of fascicles and from the aponeurosis of long and medial heads of triceps and the latter as the distance between the fat-muscle and muscle-bone interfaces. The pennation angles were in the range of 15 and 53 degrees for the long head and 9 to 26 degrees for the medial head, which were similar to or greater than the published and the present data on human cadavers. Significant differences were observed between normal subjects and bodybuilders in muscle thickness and pennation angles (P < 0.01), and there were significant correlations between muscle thickness and pennation angles for both long (r = 0.884) and medial (r = 0.833) heads of triceps, suggesting that muscle hypertrophy involves an increase in fiber pennation angles.

Arm Posture and Muscular Activity while Inserting and Aiming with Laparoscopic Tools

2005 ◽  
Vol 49 (14) ◽  
pp. 1399-1403
Author(s):  
Trejo, A.E. Jung ◽  
M.S. Hallbeck
Keyword(s):  
Biceps Brachii ◽  
Muscular Activity ◽  
Elbow Flexion ◽  
Dominant Hand ◽  
Wrist Flexion ◽  
Triceps Brachii ◽  
Upper Trapezius ◽  
Flexion Extension ◽  
Laparoscopic Tools ◽  
Wrist Flexors

Two laparoscopic tools, a scissor-type grasper and an ergonomically designed grasper, were compared in terms of arm posture and muscle activity during insertion into a trocar and during a standardized aiming task. Participants were asked to insert a laparoscopic tool into a simulated abdomen and hit five cross-shaped targets using their dominant hand; similar to reaching an organ during laparoscopic surgery. Twenty-six right-handed novice participants volunteered for the study. Two electrogoniometers were used to measure wrist flexion/extension, wrist deviation, and elbow flexion/extension angles. Six surface electrodes were used to measure %MVE of wrist flexors, wrist extensors, biceps brachii, triceps brachii, deltoid, and upper trapezius. The conditions used were five target positions, two touch screen monitor angles, and five hand postures. The scissors-type tool caused the largest wrist flexion, but the smallest %MVE from the wrist flexors. The method of gripping the tools was the most important factor determining joint angles and muscular load during the insertion and aiming tasks.

Electrical activity and relative length changes of dog limb muscles as a function of speed and gait

1981 ◽  
Vol 94 (1) ◽  
pp. 15-42 ◽  
Author(s):  
G. E. Goslow ◽  
H. J. Seeherman ◽  
C. R. Taylor ◽  
M. N. McCutchin ◽  
N. C. Heglund
Keyword(s):  
Electrical Activity ◽  
Stance Phase ◽  
Biceps Brachii ◽  
Vastus Lateralis ◽  
Activity Patterns ◽  
Relative Length ◽  
Muscular Activity ◽  
Triceps Brachii ◽  
Limb Muscles ◽  
Length Changes

Electrical activity and length changes of 11 muscles of the fore- and hind- limbs of dogs walking, running, and galloping on a treadmill, were measured as a function of forward speed and gait. Our purpose was to find out whether the activity patterns of the major limb muscles were consistent with the two mechanisms proposed for storage and recovery of energy within a stride: a ‘pendulum-like’ mechanism during a walk, and a ‘spring-like’ mechanism during a run. In the stance phase of the walking dog, we found that the supraspinatus, long head of the triceps brachii, biceps brachii, vastus lateralis, and gastrocnemius underwent only minor length changes during a relatively long portion of their activity, Thus, a major part of their activity during the walk seems consistent with a role in stabilization of the joints as the dog ‘pole-vaulted’ over its limbs (and thereby conserved energy). In the stance phase of trotting and/or galloping dogs, we found that the supraspinatus, lateral head of the triceps, vastus lateralis, and gastrocnemius were active while being stretched prior to shortening (as would be required for elastic storage of energy), and that this type of activity increased with increasing speed. We also found muscular activity in the select limb flexors that was consistent with storage of kinetic energy at the end of the swing phase and recovery during the propulsive stroke. This activity pattern was apparent in the latissimus dorsi during a walk and trot, and in the biceps femoris during a trot and gallop. We conclude that, during locomotion, a significant fraction of the electrical activity of a number of limbs muscles occurs while they undergo little or no length change or are being stretched prior to shortening and that these types of activities occur in a manner that would enable the operation of pendulum-like and spring-like mechanisms for conserving energy within a stride. Therefore these forms of muscular activity, in addition to the more familiar activity associated with muscle shortening, should be considered to be important during locomotion.

scholarly journals Differential muscle function between muscle synergists: long and lateral heads of the triceps in jumping and landing goats (Capra hircus)

2008 ◽  
Vol 105 (4) ◽  
pp. 1262-1273 ◽  
Author(s):  
Andrew M. Carroll ◽  
David V. Lee ◽  
Andrew A. Biewener
Keyword(s):  
Muscle Function ◽  
High Speed ◽  
Muscle Activation ◽  
Reaction Force ◽  
Elbow Flexion ◽  
Capra Hircus ◽  
Triceps Brachii ◽  
Joint Work ◽  
Long Head ◽  
Lateral Head

We investigate how the biarticular long head and monoarticular lateral head of the triceps brachii function in goats ( Capra hircus) during jumping and landing. Elbow moment and work were measured from high-speed video and ground reaction force (GRF) recordings. Muscle activation and strain were measured via electromyography and sonomicrometry, and muscle stress was estimated from elbow moment and by partitioning stress based on its relative strain rate. Elbow joint and muscle function were compared among three types of limb usage: jump take-off (lead limb), the step prior to jump take-off (lag limb), and landing. We predicted that the strain and work patterns in the monoarticular lateral head would follow the kinematics and work of the elbow more closely than would those of the biarticular long head. In general this prediction was supported. For instance, the lateral head stretched (5 ± 2%; mean ± SE) in the lead and lag limbs to absorb work during elbow flexion and joint work absorption, while the long head shortened (−7 ± 1%) to produce work. During elbow extension, both muscles shortened by similar amounts (−10 ± 2% long; −13 ± 4% lateral) in the lead limb to produce work. Both triceps heads functioned similarly in landing, stretching (13 ± 3% in the long head and 19 ± 5% in the lateral) to absorb energy. In general, the long head functioned to produce power at the shoulder and elbow, while the lateral head functioned to resist elbow flexion and absorb work, demonstrating that functional diversification can arise between mono- and biarticular muscle agonists operating at the same joint.

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.

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.

Intra- and Intersession Reliability of Surface Electromyography on Muscles Actuating the Forearm During Maximum Voluntary Contractions

2016 ◽  
Vol 32 (6) ◽  
pp. 558-570 ◽  
Author(s):  
Guillaume Gaudet ◽  
Maxime Raison ◽  
Fabien Dal Maso ◽  
Sofiane Achiche ◽  
Mickael Begon
Keyword(s):  
Surface Electromyography ◽  
Biceps Brachii ◽  
Intraclass Correlation ◽  
Isometric Contractions ◽  
Triceps Brachii ◽  
Pronator Quadratus ◽  
Pronator Teres ◽  
Flexion Extension ◽  
Long Head ◽  
Voluntary Contractions

The aim of this study is to determine the intra- and intersession reliability of nonnormalized surface electromyography (sEMG) on the muscles actuating the forearm during maximum voluntary isometric contractions (MVIC). A subobjective of this study is to determine the intra- and intersession reliability of forearm MVIC force or torque, which is a prerequisite to assess sEMG reliability. Eighteen healthy adults participated at 4 different times: baseline, 1-h post, 6-h post, and 24-h post. They performed 3 MVIC trials of forearm flexion, extension, pronation, and supination. sEMG of the biceps brachii short head, brachialis, brachioradialis, triceps brachii long head, pronator teres, and pronator quadratus were measured. The intraclass correlation coefficient (ICC) on MVIC ranged from 0.36 to 0.99. Reliability was excellent for flexion, extension, and supination MVIC for both intra- and intersession. The ICC on sEMG ranged from 0.58 to 0.99. sEMG reliability was excellent for brachialis, brachioradialis, and pronator quadratus, and good to excellent for triceps brachii, biceps brachii, and pronator teres. This study shows that performing 3 MVICs is sufficient to obtain highly reliable maximal sEMG over 24 h for the main muscles actuating the forearm. These results confirm the potential of sEMG for muscle motor functional monitoring.

scholarly journals Muscle Activation in Traditional and Experimental Barbell Bench Press Exercise: A Potential New Tool for Fitness Maintenance

Sports ◽  
2019 ◽  
Vol 7 (10) ◽  
pp. 224
Author(s):  
Andrea Melani ◽  
Giuliana Gobbi ◽  
Daniela Galli ◽  
Cecilia Carubbi ◽  
Elena Masselli ◽  
...  
Keyword(s):  
Muscle Activity ◽  
Professional Training ◽  
Muscle Activation ◽  
Bench Press ◽  
Biceps Brachii ◽  
Elbow Flexion ◽  
Upper Body ◽  
Triceps Brachii ◽  
Extended Position ◽  
Lower Load

Background: The bench press exercise (BP) is commonly practiced in both recreational and professional training. The weight is lowered from a position where the elbows are at a 90° angle at the start and <90° at the end of eccentric phase, and then returned to the elbows extended position. In order to focus the exercise more on the triceps brachii (TB) rather than the pectoralis major (PM), the inter-handle distance (IHD) is decreased diminishing the involvement of the PM in favor of the TB. Purpose: To improve performance of the exercise by reducing force dissociation and transmitting 100% of the external load to the muscle tissue we propose a prototype of the barbell with a bar on which two sleeves are capable of sliding. The dynamic modifications of the IHD keep the elbow flexion angle constant at 90°. Results: Analysis of the inter-handle distance (IHD) signals of the upper body muscles showed a marked increase in muscle activity using the experimental barbell for the PM (19.5%) and for the biceps brachii (173%). Conclusions: The experimental barbell increased the muscle activity typical of the bench press exercise, obtaining the same training induction with a lower load and consequently preventing articular stress.

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