scholarly journals Perception of effort during an isometric contraction is influenced by prior muscle lengthening or shortening

2021 ◽  
Author(s):  
Benjamin Kozlowski ◽  
Benjamin Pageaux ◽  
Emma H Hubbard ◽  
Benjamin St. Peters ◽  
Philip J Millar ◽  
...  
Keyword(s):  
Steady State ◽  
Muscle Contraction ◽  
Isometric Contraction ◽  
Muscle Activation ◽  
Muscle Length ◽  
Motor Command ◽  
History Dependence ◽  
Neuromuscular Activation ◽  
Perception Of Effort

Purpose: Following a shortening or lengthening muscle contraction, the torque produced in the isometric steady state is distinctly lower (residual torque depression; rTD) or higher (residual torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force. Methods: Experiment 1 tested whether perception of effort differed between the rTD and rTE state when torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. Results: When torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. Conclusion: The combined results from these experiments indicate that the history dependence of force alters ones perception of effort, dependent on the level of motor command.

scholarly journals Does the Length of Elbow Flexors and Visual Feedback Have Effect on Accuracy of Isometric Muscle Contraction in Men after Stroke?

2016 ◽  
Vol 2016 ◽  
pp. 1-6
Author(s):  
Vilma Juodzbaliene ◽  
Tomas Darbutas ◽  
Albertas Skurvydas ◽  
Marius Brazaitis
Keyword(s):  
Muscle Contraction ◽  
Visual Feedback ◽  
Isometric Contraction ◽  
Muscle Force ◽  
Muscle Length ◽  
Elbow Flexion ◽  
Elbow Flexors ◽  
Feedback Information ◽  
Isometric Muscle Contraction ◽  
The Difference

The aim of the study was to determine the effect of different muscle length and visual feedback information (VFI) on accuracy of isometric contraction of elbow flexors in men after an ischemic stroke (IS).Materials and Methods. Maximum voluntary muscle contraction force (MVMCF) and accurate determinate muscle force (20% of MVMCF) developed during an isometric contraction of elbow flexors in 90° and 60° of elbow flexion were measured by an isokinetic dynamometer in healthy subjects (MH,n=20) and subjects after an IS during their postrehabilitation period (MS,n=20).Results. In order to evaluate the accuracy of the isometric contraction of the elbow flexors absolute errors were calculated. The absolute errors provided information about the difference between determinate and achieved muscle force.Conclusions. There is a tendency that greater absolute errors generating determinate force are made by MH and MS subjects in case of a greater elbow flexors length despite presence of VFI. Absolute errors also increase in both groups in case of a greater elbow flexors length without VFI. MS subjects make greater absolute errors generating determinate force without VFI in comparison with MH in shorter elbow flexors length.

Influence of submaximal isometric contractions of the hamstrings on electromyography activity and force while functioning as hip extensors

2020 ◽  
pp. 1-8
Author(s):  
Dasom Oh ◽  
Wootaek Lim
Keyword(s):  
Prone Position ◽  
Supine Position ◽  
Isometric Contraction ◽  
Muscle Length ◽  
Biceps Femoris ◽  
Emg Activity ◽  
Isometric Contractions ◽  
Significant Difference ◽  
Extension Force ◽  
Long Head

BACKGROUND: Although the medial and lateral hamstrings are clearly distinct anatomically and have different functions in the transverse plane, they are often considered as one muscle during rehabilitation. OBJECTIVE: The purpose of the study was to compare the electromyographic (EMG) activity between the prone position and the supine position during maximal isometric contraction and to additionally confirm the effect of submaximal isometric contractions on EMG activity of medial and lateral hamstrings, and force. METHODS: In the prone position, EMG activities of the long head of biceps femoris (BFLH) and semitendinosus (ST) were measured during the maximal isometric contraction. In the supine position, hip extension force with EMG activity were measured during the maximal and the submaximal isometric contractions. RESULTS: EMG activity in the prone position was significantly decreased in the supine position. In the supine position, there was a significant difference between the BFLH and ST during the maximal isometric contraction, but not during the submaximal isometric contractions. CONCLUSIONS: The dependence on the hamstrings could be relatively lower during hip extensions. When the medial and lateral hamstrings are considered separately, the lateral hamstrings may show a more active response, with increased muscle length, in clinical practice.

scholarly journals Muscle length and joint angle influence spinal but not corticospinal excitability to the biceps brachii across forearm postures

2019 ◽  
Vol 122 (1) ◽  
pp. 413-423 ◽  
Author(s):  
Davis A. Forman ◽  
Daniel Abdel-Malek ◽  
Christopher M. F. Bunce ◽  
Michael W. R. Holmes
Keyword(s):  
Isometric Contraction ◽  
Elbow Joint ◽  
Joint Angle ◽  
Biceps Brachii ◽  
Motor Evoked Potentials ◽  
Muscle Length ◽  
Elbow Flexion ◽  
Corticospinal Excitability ◽  
Biceps Brachii Muscle ◽  
Spinal Excitability

Forearm rotation (supination/pronation) alters corticospinal excitability to the biceps brachii, but it is unclear whether corticospinal excitability is influenced by joint angle, muscle length, or both. Thus the purpose of this study was to separately examine elbow joint angle and muscle length on corticospinal excitability. Corticospinal excitability to the biceps and triceps brachii was measured using motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation. Spinal excitability was measured using cervicomedullary motor evoked potentials (CMEPs) elicited via transmastoid electrical stimulation. Elbow angles were manipulated with a fixed biceps brachii muscle length (and vice versa) across five unique postures: 1) forearm neutral, elbow flexion 90°; 2) forearm supinated, elbow flexion 90°; 3) forearm pronated, elbow flexion 90°; 4) forearm supinated, elbow flexion 78°; and 5) forearm pronated, elbow flexion 113°. A musculoskeletal model determined biceps brachii muscle length for postures 1–3, and elbow joint angles ( postures 4–5) were selected to maintain biceps length across forearm orientations. MEPs and CMEPs were elicited at rest and during an isometric contraction of 10% of maximal biceps muscle activity. At rest, MEP amplitudes to the biceps were largest during supination, which was independent of elbow joint angle. CMEP amplitudes were not different when the elbow was fixed at 90° but were largest in pronation when muscle length was controlled. During an isometric contraction, there were no significant differences across forearm postures for either MEP or CMEP amplitudes. These results highlight that elbow joint angle and biceps brachii muscle length can each independently influence spinal excitability. NEW & NOTEWORTHY Changes in upper limb posture can influence the responsiveness of the central nervous system to artificial stimulations. We established a novel approach integrating neurophysiology techniques with biomechanical modeling. Through this approach, the effects of elbow joint angle and biceps brachii muscle length on corticospinal and spinal excitability were assessed. We demonstrate that spinal excitability is uniquely influenced by joint angle and muscle length, and this highlights the importance of accounting for muscle length in neurophysiological studies.

scholarly journals Modifiability of the history dependence of force through chronic eccentric and concentric biased resistance training

2019 ◽  
Vol 126 (3) ◽  
pp. 647-657 ◽  
Author(s):  
Jackey Chen ◽  
Geoffrey A. Power
Keyword(s):  
Steady State ◽  
Resistance Training ◽  
Isometric Force ◽  
Eccentric Training ◽  
Force Enhancement ◽  
History Dependence ◽  
Force Depression ◽  
Residual Force ◽  
Residual Force Enhancement ◽  
Concentric Training

The increase and decrease in steady-state isometric force following active muscle lengthening and shortening are referred to as residual force enhancement (RFE) and force depression (FD), respectively. The RFE and FD states are associated with decreased (activation reduction; AR) and increased (activation increase; AI) neuromuscular activity, respectively. Although the mechanisms have been discussed over the last 60 years, no studies have systematically investigated the modifiability of RFE and FD with training. The purpose of the present study was to determine whether RFE and FD could be modulated through eccentric and concentric biased resistance training. Fifteen healthy young adult men (age: 24 ± 2 yr, weight: 77 ± 8 kg, height: 178 ± 5 cm) underwent 4 wk of isokinetic dorsiflexion training, in which one leg was trained eccentrically (−25°/s) and the other concentrically (+25°/s) over a 50° ankle excursion. Maximal and submaximal (40% maximum voluntary contraction) steady-state isometric torque and EMG values following active lengthening and shortening were compared to purely isometric values at the same joint angles and torque levels. Residual torque enhancement (rTE) decreased by ~36% after eccentric training ( P < 0.05) and increased by ~89% after concentric training ( P < 0.05), whereas residual torque depression (rTD), AR, AI, and optimal angles for torque production were not significantly altered by resistance training ( P ≥ 0.05). It appears that rTE, but not rTD, for the human ankle dorsiflexors is differentially modifiable through contraction type-dependent resistance training. NEW & NOTEWORTHY The history dependence of force production is a property of muscle unexplained by current cross bridge and sliding filament theories. Whether a muscle is actively lengthened (residual force enhancement; RFE) or shortened (force depression) to a given length, the isometric force should be equal to a purely isometric contraction—but it is not! In this study we show that eccentric training decreased RFE, whereas concentric training increased RFE and converted all nonresponders (i.e., not exhibiting RFE) into responders.

Muscle Contraction: Calcium in Muscle Activation.

Science ◽  
1987 ◽  
Vol 238 (4824) ◽  
pp. 223-223 ◽  
Author(s):  
A. G. SZENT-GYORGYI
Keyword(s):  
Muscle Contraction ◽  
Muscle Activation

The EMG-force relationship of the cat soleus muscle and its association with contractile conditions during locomotion.

1995 ◽  
Vol 198 (4) ◽  
pp. 975-987 ◽  
Author(s):  
A C Guimaraes ◽  
W Herzog ◽  
T L Allinger ◽  
Y T Zhang
Keyword(s):  
Soleus Muscle ◽  
Adaptive Filtering ◽  
Muscle Activation ◽  
Stance Phase ◽  
Force Production ◽  
Muscle Length ◽  
Force Transducer ◽  
Shortening Velocity ◽  
Integrated Emg ◽  
Filtering Approach

The relationship between force and electromyographic (EMG) signals of the cat soleus muscle was obtained for three animals during locomotion at five different speeds (154 steps), using implanted EMG electrodes and a force transducer. Experimentally obtained force-IEMG (= integrated EMG) relationships were compared with theoretically predicted instantaneous activation levels calculated by dividing the measured force by the predicted maximal force that the muscle could possibly generate as a function of its instantaneous contractile conditions. In addition, muscular forces were estimated from the corresponding EMG records exclusively using an adaptive filtering approach. Mean force-IEMG relationships were highly non-linear but similar in shape for different cats and different speeds of locomotion. The theoretically predicted activation-time plots typically showed two peaks, as did the IEMG-time plots. The first IEMG peak tended to be higher than the second one and it appeared to be associated with the initial priming of the muscle for force production at paw contact and the peak force observed early during the stance phase. The second IEMG peak appeared to be a burst of high muscle activation, which might have compensated for the levels of muscle length and shortening velocity that were suboptimal during the latter part of the stance phase. Although it was difficult to explain the soleus forces on the basis of the theoretically predicted instantaneous activation levels, it was straightforward to approximate these forces accurately from EMG data using an adaptive filtering approach.

Transient responses and continuous behavior of active smooth muscle during controlled stretches

1982 ◽  
Vol 242 (3) ◽  
pp. C146-C158 ◽  
Author(s):  
R. A. Meiss
Keyword(s):  
Steady State ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Initial Slope ◽  
Stretch Rate ◽  
Rate Dependent ◽  
Upward Slope ◽  
Length Changes ◽  
State Force ◽  
The Relationship

Controlled length changes were imposed on mesotubarium superius and ovarian ligament smooth muscles from the reproductive tracts of female rabbits in constant estrus. Stretches of up to 35% of the muscle length were applied during isometric contraction, relaxation, and steady-state force levels. Force was continuously monitored and was plotted as a function of length. During constant velocity stretches there was an initial steep rise in force, a rapid downward deviation from the initial slope, and a long region with a constant upward slope. Stretches made during contraction showed smaller initial rises in force and steeper linear portions than did identical comparison stretches made during relaxation. The value of the slope was independent of the prior developed force, but it did depend on whether the muscle was contracting or relaxing. During contraction and steady-state force levels, the slope was independent of the stretch rate, but it was strongly rate dependent during relaxation. Changes in the stretch rate during stretch caused associated changes in muscle force; the relationship was curvilinear and was exaggerated during relaxation. The findings are placed in the context of a sliding-filament--cross-bridge hypothesis.

Metabolic fluctuation during a muscle contraction cycle

1998 ◽  
Vol 274 (3) ◽  
pp. C846-C852 ◽  
Author(s):  
Youngran Chung ◽  
Robert Sharman ◽  
Richard Carlsen ◽  
Steven W. Unger ◽  
Douglas Larson ◽  
...  
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Steady State ◽  
Magnetic Resonance ◽  
Muscle Contraction ◽  
Gastrocnemius Muscle ◽  
Reference State ◽  
Maximum Force ◽  
Muscle Twitch ◽  
Energy Fluctuation ◽  
Contraction Cycle

Gated31P-nuclear magnetic resonance followed the metabolic fluctuation in rat gastrocnemius muscle during a contraction cycle. Within 16 ms after stimulation, the phosphocreatine (PCr) level drops 11.3% from its reference state. The PCr minimum corresponds closely to the time of maximum force contraction. Pi increases stoichiometrically, while ATP remains constant. During a twitch, PCr hydrolysis produces 3.1 μmol ATP/g tissue, which is substantially higher than the reported 0.3 μmol ATP ⋅ twitch−1 ⋅ g tissue−1 derived from steady-state experiments. The results reveal that a substantial energy fluctuation accompanies a muscle twitch.

Blood flow response to muscle contractions is more closely related to metabolic rate than contractile work

2005 ◽  
Vol 98 (6) ◽  
pp. 2096-2100 ◽  
Author(s):  
Jason J. Hamann ◽  
Heidi A. Kluess ◽  
John B. Buckwalter ◽  
Philip S. Clifford
Keyword(s):  
Blood Flow ◽  
Steady State ◽  
Short Duration ◽  
Muscle Activation ◽  
Muscle Metabolism ◽  
Metabolic Cost ◽  
Blood Flow Response ◽  
Flow Response ◽  
Long Duration ◽  
Tension Time

The magnitude of the blood flow response to exercise has been linked to both the contractile work performed and the metabolic cost of the activity. Under certain conditions, contractile work and metabolic cost may be dissociated. This study examined the blood flow response to trains of contractions when contraction duration was manipulated under conditions of similar tension-time indexes (isometric analog of work). Previous investigations have shown that trains of short-duration contractions have a greater ATP utilization, which may result from an augmented ion transport required for muscle activation and relaxation. On the basis of these findings, we hypothesized that the blood flow response would be greater to a train of short-duration contractions than a train of long-duration contractions. Canine gastrocnemius-plantaris muscle ( n = 8) was isolated, and blood flow assessed with an ultrasound flow probe placed around the popliteal artery. The sciatic nerve was stimulated to produce two contraction protocols that resulted in similar contraction-to-rest ratios: short duration: 0.25 s/0.75 s vs. long duration: 1 s /3 s. In accord with the design of the experiment, the tension-time indexes were identical for the two contraction protocols (short: 18.6 ± 1.0 vs. long: 18.6 ± 1.0 kN·s). Steady-state oxygen consumption was greater in the short-duration contractions (17.2 ± 0.9 ml·100 g−1·min−1) than in the long-duration contractions (11.7 ± 0.7 ml·100 g−1·min−1). Similarly, the steady-state blood flow was greater in contractions of short duration (125 ± 7 ml/min) compared with long-duration contractions (92 ± 7 ml/min). Contractions of short duration resulted in significantly higher oxygen consumptions and blood flows compared with contractions of long duration despite the same total contractile work. The blood flow response to muscle contraction appears to be more closely associated with muscle metabolism than contractile work performed.

Sign in / Sign up

Export Citation Format

Share Document