scholarly journals Assessment on Stationarity of EMG Signals with Different Windows Size During Isotonic Contractions

2017 ◽  
Vol 7 (10) ◽  
pp. 1050 ◽  
Author(s):  
Nurhazimah Nazmi ◽  
Mohd Abdul Rahman ◽  
Shin-ichiroh Yamamoto ◽  
Siti Ahmad ◽  
MB Malarvili ◽  
...  
Keyword(s):  
Isotonic Contractions

scholarly journals Influence of layer separation on the determination of stomach smooth muscle properties

2021 ◽  
Author(s):  
Mischa Borsdorf ◽  
Markus Böl ◽  
Tobias Siebert
Keyword(s):  
Smooth Muscle ◽  
Muscle Fibers ◽  
Smooth Muscles ◽  
Muscle Layer ◽  
Uniaxial Tensile ◽  
Muscle Properties ◽  
Layer Separation ◽  
Isotonic Contractions ◽  
Longitudinal Layer

AbstractUniaxial tensile experiments are a standard method to determine the contractile properties of smooth muscles. Smooth muscle strips from organs of the urogenital and gastrointestinal tract contain multiple muscle layers with different muscle fiber orientations, which are frequently not separated for the experiments. During strip activation, these muscle fibers contract in deviant orientations from the force-measuring axis, affecting the biomechanical characteristics of the tissue strips. This study aimed to investigate the influence of muscle layer separation on the determination of smooth muscle properties. Smooth muscle strips, consisting of longitudinal and circumferential muscle layers (whole-muscle strips [WMS]), and smooth muscle strips, consisting of only the circumferential muscle layer (separated layer strips [SLS]), have been prepared from the fundus of the porcine stomach. Strips were mounted with muscle fibers of the circumferential layer inline with the force-measuring axis of the uniaxial testing setup. The force–length (FLR) and force–velocity relationships (FVR) were determined through a series of isometric and isotonic contractions, respectively. Muscle layer separation revealed no changes in the FLR. However, the SLS exhibited a higher maximal shortening velocity and a lower curvature factor than WMS. During WMS activation, the transversally oriented muscle fibers of the longitudinal layer shortened, resulting in a narrowing of this layer. Expecting volume constancy of muscle tissue, this narrowing leads to a lengthening of the longitudinal layer, which counteracted the shortening of the circumferential layer during isotonic contractions. Consequently, the shortening velocities of the WMS were decreased significantly. This effect was stronger at high shortening velocities.

scholarly journals Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle

1997 ◽  
Vol 83 (4) ◽  
pp. 1062-1067 ◽  
Author(s):  
Roland H. H. Van Balkom ◽  
Wen-Zhi Zhan ◽  
Y. S. Prakash ◽  
P. N. Richard Dekhuijzen ◽  
Gary C. Sieck
Keyword(s):  
Isometric Force ◽  
Contractile Properties ◽  
Diaphragm Muscle ◽  
Peak Power Output ◽  
Rat Diaphragm ◽  
Fiber Morphology ◽  
Shortening Velocity ◽  
Maximum Isometric Force ◽  
Induced Changes ◽  
Isotonic Contractions

Van Balkom, Roland H. H., Wen-Zhi Zhan, Y. S. Prakash, P. N. Richard Dekhuijzen, and Gary C. Sieck. Corticosteroid effects on isotonic contractile properties of rat diaphragm muscle. J. Appl. Physiol. 83(4): 1062–1067, 1997.—The effects of corticosteroids (CS) on diaphragm muscle (Diam) fiber morphology and contractile properties were evaluated in three groups of rats: controls (Ctl), surgical sham and weight-matched controls (Sham), and CS-treated (6 mg ⋅ kg−1 ⋅ day−1prednisolone at 2.5 ml/h for 3 wk). In the CS-treated Diam, there was a selective atrophy of type IIx and IIb fibers, compared with a generalized atrophy of all fibers in the Sham group. Maximum isometric force was reduced by 20% in the CS group compared with both Ctl and Sham. Maximum shortening velocity in the CS Diamwas slowed by ∼20% compared with Ctl and Sham. Peak power output of the CS Diam was only 60% of Ctl and 70% of Sham. Endurance to repeated isotonic contractions improved in the CS-treated Diam compared with Ctl. We conclude that the atrophy of type IIx and IIb fibers in the Diam can only partially account for the CS-induced changes in isotonic contractile properties. Other factors such as reduced myofibrillar density or altered cross-bridge cycling kinetics are also likely to contribute to the effects of CS treatment.

Catchlike-inducing train activation of human muscle during isotonic contractions: burst modulation

1999 ◽  
Vol 87 (5) ◽  
pp. 1758-1767 ◽  
Author(s):  
Samuel C. K. Lee ◽  
Cara N. Becker ◽  
Stuart A. Binder-Macleod
Keyword(s):  
Isometric Contraction ◽  
Peak Power ◽  
Average Power ◽  
Knee Extension ◽  
Human Muscle ◽  
Constant Frequency ◽  
Maximum Voluntary Isometric Contraction ◽  
Before And After ◽  
Isotonic Performance ◽  
Isotonic Contractions

Stimulation trains that exploit the catchlike property [catchlike-inducing trains (CITs)] produce greater forces and rates of rise of force than do constant-frequency trains (CFTs) during isometric contractions and isovelocity movements. This study examined the effect of CITs during isotonic contractions in healthy subjects. Knee extension was electrically elicited against a load of 10% of maximum voluntary isometric contraction. The stimulation intensity was set to produce 20% of maximum voluntary isometric contraction. The muscle was tested before and after fatigue with a 6-pulse CFT and 6-pulse CITs that contained an initial doublet, triplet, or quadruplet. For prefatigue responses, the greatest isotonic performance was produced by CITs with initial doublets. When the muscles were fatigued, triplet CITs were best. CITs produce greater excursion, work, peak power, and average power than do CFTs, because CITs produced more rapid rates of rise of force. Faster rates of rise of force enabled the preload on the muscle to be exceeded earlier during the stimulation train.

scholarly journals Comparison of the Gibbs and Suga formulations of cardiac energetics: the demise of “isoefficiency”

2012 ◽  
Vol 113 (7) ◽  
pp. 996-1003 ◽  
Author(s):  
J.-C. Han ◽  
A. J. Taberner ◽  
K. Tran ◽  
S. Goo ◽  
D. P. Nickerson ◽  
...  
Keyword(s):  
Isometric Force ◽  
Systolic Pressure ◽  
Isometric Contractions ◽  
Papillary Muscles ◽  
Cardiac Energetics ◽  
The Past ◽  
Wide Range ◽  
Time Work ◽  
Isotonic Contractions ◽  
Thermodynamic Basis

Two very different sorts of experiments have characterized the field of cardiac energetics over the past three decades. In one of these, Gibbs and colleagues measured the heat production of isolated papillary muscles undergoing isometric contractions and afterloaded isotonic contractions. The former generated roughly linear heat vs. force relationships. The latter generated enthalpy-load relationships, the peak values of which occurred at or near peak isometric force, i.e., at a relative load of unity. Contractile efficiency showed a pronounced dependence on afterload. By contrast, Suga and coworkers measured the oxygen consumption (V̇o2) while recording the pressure-volume-time work loops of blood-perfused isolated dog hearts. From the associated (linear) end-systolic pressure-volume relations they derived a quantity labeled pressure-volume area (PVA), consisting of the sum of pressure-volume work and unspent elastic energy and showed that this was linearly correlated with V̇o2 over a wide range of conditions. This linear dependence imposed isoefficiency: constant contractile efficiency independent of afterload. Neither these data nor those of Gibbs and colleagues are in dispute. Nevertheless, despite numerous attempts over the years, no demonstration of either compatibility or incompatibility of these disparate characterizations of cardiac energetics has been forthcoming. We demonstrate that compatibility between the two formulations is thwarted by the concept of isoefficiency, the thermodynamic basis of which we show to be untenable.

scholarly journals Staircase, rest contractions, and potentiation in the isolated rat heart

1962 ◽  
Vol 202 (4) ◽  
pp. 636-640 ◽  
Author(s):  
F. L. Meijler
Keyword(s):  
Cycle Length ◽  
Rest Period ◽  
Isolated Rat Heart ◽  
Stimulation Rate ◽  
Rat Hearts ◽  
Constant Rate ◽  
Theoretical Evidence ◽  
The Relationship ◽  
Isotonic Contractions ◽  
Isolated Rat

Variation in amplitude of isotonic contractions of intact isolated rat hearts, following changes in cycle length, were studied. It was found that a staircase-like phenomenon resembling the original Bowditch effect cannot be evoked in a intact mammalian heart without special measures, such as adding acetylcholine to the perfusion fluid. A steady state relation of rate to amplitude of isotonic contractions was demonstrated. Potentiation of contractility can be originated by sudden changes in stimulation rate. A rest period preceding the changes in stimulation rate does not change the potentiation found originally. At a constant rate the amplitude of a contraction is determined by the preceding cycle length. This relation has been called restitution. Theoretical evidence is presented in an attempt to demonstrate that restitution and potentiation are due to the same process. It can be concluded that Bowditch's staircase does not play a role in the relationship between cycle length and contractility in intact hearts and the statement that restitution and potentiation are due to the same process offers an opportunity to describe all effects of changes in cycle length on isotonic contractions as one phenomenon.

Production of isotonic contractions in the intact canine left ventricle.

1969 ◽  
Vol 27 (4) ◽  
pp. 577-581 ◽  
Author(s):  
J W Covell ◽  
J S Fuhrer ◽  
R C Boerth ◽  
J Ross
Keyword(s):  
Left Ventricle ◽  
Isotonic Contractions

Glucocorticoid-Induced Alterations in Isotonic Contractions of the Rat Diaphragm

1993 ◽  
Vol 4 (3) ◽  
pp. 16-17
Author(s):  
J M Eason ◽  
S L Dodd ◽  
I S Vrabas ◽  
S K Powers
Keyword(s):  
Rat Diaphragm ◽  
Isotonic Contractions

Excitation-induced Ca2+uptake in rat skeletal muscle

1999 ◽  
Vol 276 (2) ◽  
pp. R331-R339 ◽  
Author(s):  
H. Gissel ◽  
T. Clausen
Keyword(s):  
Skeletal Muscle ◽  
Electrical Stimulation ◽  
Initial Rate ◽  
Low Frequency ◽  
Channel Blockers ◽  
Ca Uptake ◽  
Edl Muscle ◽  
Isotonic Contractions ◽  
Progressive Accumulation ◽  
Stimulation Of

In isolated rat extensor digitorum longus (EDL) muscle mounted for isometric contractions, chronic low-frequency electrical stimulation was found to lead to an increased uptake of45Ca (154% above control after 240 min) and a progressive accumulation of Ca2+ (85% above control after 240 min). In soleus, however, this treatment led to a small, but significant, increase in 45Ca uptake (30% above control after 180 min) but no significant accumulation of Ca2+. In muscles mounted for isotonic contractions without any external load, electrical stimulation gave rise to a larger45Ca uptake and accumulation of Ca2+ in both EDL and soleus. These uptakes of Ca2+ coincided with an accumulation of Na+. During isometric or isotonic contractions, stimulation at 40 Hz increased the initial (60 s) rate of 45Ca uptake in soleus muscle 15- and 30-fold, respectively. The stimulation-induced increase in 45Ca uptake was only reduced by 17% by the Ca2+-channel blockers nifedipine and verapamil but was blocked by tetrodotoxin. The initial rate of stimulation-induced 22Na and45Ca uptake was correlated ( r = 0.80; P < 0.003). Stimulation of Na+ channels with veratridine increased 45Ca uptake by 93 and 139% in soleus and EDL, respectively ( P < 0.001), effects that were abolished by tetrodotoxin. The results indicate that in skeletal muscle, excitation induces a considerable influx of Ca2+, mediated by Na+ channels.

Effect of initial length on relations between oxygen uptake and load in dog muscle

1976 ◽  
Vol 230 (4) ◽  
pp. 1008-1012 ◽  
Author(s):  
WN Stainsby ◽  
JK Barclay
Keyword(s):  
Skeletal Muscle ◽  
Oxygen Uptake ◽  
The Other ◽  
Mammalian Skeletal Muscle ◽  
Initial Length ◽  
Muscle Preparation ◽  
Optimal Length ◽  
Muscle Energetics ◽  
Isotonic Contractions ◽  
Fenn Effect

Oxygen uptake for brief tetanic contractions was calculated from measurements of blood flow and blood arteriovenous oxygen content differences. Each muscle preparation was pretested under isometric conditions to establish optimal length, Lo. After this one group of preparations performed afterload isotonic contractions at several loads with initial length, Li, less than Lo. The other groups of preparations performed similar contractions with Li greater than Lo. When Li was less than Lo, oxygen uptake for the highest load was always greater than oxygen uptake at the lowest load whereas intermediate loads were usually higher than both extremes. However, when Li was greater than Lo, oxygen uptake at the highest load was always less than oxygen uptake at the lowest load; again the intermediate loads were usually higher than both extremes. The data confirm and extend similar effects of initial length on heat production for contractions by amphibian muscles (7). It seems likely that the differences in initial lengths may account for the fact that the Fenn effect has not previously been observed in studies of mammalian skeletal muscle energetics.

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