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.

Work-dependent deactivation of a crustacean muscle

1999 ◽  
Vol 202 (18) ◽  
pp. 2551-2565 ◽  
Author(s):  
R.K. Josephson ◽  
D.R. Stokes
Keyword(s):  
Muscle Activation ◽  
Isometric Force ◽  
Carcinus Maenas ◽  
Stimulus Frequency ◽  
Force Production ◽  
Muscle Length ◽  
Background Level ◽  
Shortening Velocity ◽  
Shortening Deactivation ◽  
Work Done

Active shortening of respiratory muscle L2B from the crab Carcinus maenas results in contractile deactivation, seen as (1) a decline of force during the course of isovelocity shortening, (2) a reduction in the rate of force redevelopment following shortening, (3) a depression of the level of isometric force reached following shortening, and (4) an accelerated relaxation at the end of stimulation. The degree of deactivation increases with increasing distance of shortening, decreases with increasing shortening velocity, and is approximately linearly related to the work done during shortening. Deactivation lasts many seconds if stimulation is maintained, but is largely although not completely removed if the stimulation is temporarily interrupted so that the force drops towards the resting level. Deactivation for a given distance and velocity of shortening increases with increasing muscle length above the optimum length for force production. Stimulating muscle L2B at suboptimal frequencies gives tetanic contractions that are fully fused but of less than maximal amplitude. The depression of force following shortening, relative to the force during an isometric contraction, is independent of the stimulus frequency used to activate the muscle, indicating that deactivation is not a function of the background level of stimulus-controlled muscle activation upon which it occurs. Deactivation reduces the work required to restretch a muscle after it has shortened, but it also lowers the force and therefore the work done during shortening. The net effect of deactivation on work output over a full shortening/lengthening cycle is unknown.

A unique micromechanocalorimeter for simultaneous measurement of heat rate and force production of cardiac trabeculae carneae

2009 ◽  
Vol 107 (3) ◽  
pp. 946-951 ◽  
Author(s):  
June-Chiew Han ◽  
Andrew J. Taberner ◽  
Robert S. Kirton ◽  
Poul M. Nielsen ◽  
Nicholas P. Smith ◽  
...  
Keyword(s):  
Energy Expenditure ◽  
Thermal Performance ◽  
Mechanical Performance ◽  
Force Production ◽  
Muscle Length ◽  
Heat Rate ◽  
Force Transducer ◽  
Muscle Energetics ◽  
Flow Through

To study cardiac muscle energetics quantitatively, it is of paramount importance to measure, simultaneously, mechanical and thermal performance. Ideally, this should be achieved under conditions that minimize the risk of tissue anoxia, especially under high rates of energy expenditure. In vitro, this consideration necessitates the use of preparations of small radial dimensions. To that end, we have constructed a unique micromechanocalorimeter, consisting of an open-ended flow-through microcalorimeter, a force transducer, and a pair of muscle-length actuators. The device enables the metabolic and mechanical performance of cardiac trabeculae carneae to be investigated for prolonged periods in a continuously replenished oxygen- and nutrient-rich environment.

Mechanism and significance of early, rapid shortening in sensitized airway smooth muscleThis article is one of a selection of papers published in the Special Issue on Recent Advances in Asthma Research.

2007 ◽  
Vol 85 (7) ◽  
pp. 747-753 ◽  
Author(s):  
Lincoln E. Ford ◽  
Susan H. Gilbert
Keyword(s):  
Myosin Light Chain ◽  
Force Production ◽  
Muscle Length ◽  
Airway Disease ◽  
Shortening Velocity ◽  
Reactive Airway Disease ◽  
Activation Rate ◽  
Contractile Parameters ◽  
Stage Process ◽  
Selection Of

It has been reported that sensitization of animals to allergens increases both early shortening velocity and myosin light-chain kinase of their airway smooth muscle without increasing force generated by these muscles. Since early shortening sets muscle length for the duration of a contraction, these responses might be expected to produce greater airway obstruction. Here, it is explained how the more rapid early shortening without increased force production is predicted by the 2-stage process of activation followed by contraction posited by the crossbridge theory of contraction when the rate, but not the extent, of activation is increased. The experimental results are reproduced by a simple model in which activation rate is increased 1.6-fold without any other changes in contractile parameters. These results reinforce suggestions that sensitized animals are a model for reactive airway disease.

Architecture, composition, and contractile properties of rat soleus muscle grafts

1986 ◽  
Vol 250 (3) ◽  
pp. C474-C479 ◽  
Author(s):  
S. S. Segal ◽  
T. P. White ◽  
J. A. Faulkner
Keyword(s):  
Soleus Muscle ◽  
Muscle Length ◽  
Contractile Properties ◽  
Shortening Velocity ◽  
Cross Sectional ◽  
Tension Development ◽  
Specific Tension ◽  
Control Value ◽  
Rat Soleus Muscle ◽  
Total Muscle

Skeletal muscle grafts have a deficit in tension development compared with control muscles, even after accounting for reduced mass and total muscle cross-sectional area. Our purpose was to determine relationships among the architecture, tissue composition, and contractile properties of rat soleus muscle grafts. Data were compared with control soleus muscles obtained from littermates. Female Wistar rats were anesthetized with pentobarbital sodium for grafting of soleus muscles with nerve implant and for dissection of muscles 56 days after grafting. Compared with control values, the maximum specific tension (N/cm2) of grafts was 76%, the interstitial (inulin) space was 135%, and the connective tissue protein concentration was 177%. For grafts, total muscle length and fiber length were 91 and 123% of control values, respectively. The extrapolated shortening velocity at zero load (fiber lengths/s) for grafts was not different from the control value. The deficit in specific tension of grafts is explained by a greater concentration of noncontractile tissue components. Changes in muscle architecture and composition following grafting had little affect on contraction dynamics.

scholarly journals Effects of muscle length on the EMG-force relationship of the cat soleus muscle studied using non-periodic stimulation of ventral root filaments.

1994 ◽  
Vol 193 (1) ◽  
pp. 49-64
Author(s):  
A C Guimaraes ◽  
W Herzog ◽  
M Hulliger ◽  
Y T Zhang ◽  
S Day
Keyword(s):  
Soleus Muscle ◽  
Muscle Length ◽  
Motor Units ◽  
Ventral Root ◽  
Length Relationship ◽  
Active Motor ◽  
Integrated Emg ◽  
Relationship Of ◽  
Force Relationship ◽  
Stimulation Of

The effects of changing the length of the cat soleus muscle on electromyographic (EMG) signals, muscle force and the corresponding EMG-force relationship were assessed using distributed stimulation of ten ventral root filaments and irregular interpulse intervals. EMG-force relationships were first determined for four muscle lengths using a protocol of simultaneous addition and rate modulation of ventral root filaments. In the second test, three submaximal levels of stimulation were applied at eight muscle lengths. EMG signals were obtained using surface and wire electrodes, and force was measured using a strain transducer. For most muscle lengths, the relationships between integrated EMG and mean force obtained using wire and surface electrodes were sigmoid with a linear intermediate region. The effects of muscle length on EMG signals were likely to be associated with movement of the recording electrodes relative to each other and to the active motor units. Mean forces increased with increasing muscle length and with increasing levels of stimulation. Mean force-length relationships obtained using submaximal stimulation were not simply scaled down versions of the force-length relationship obtained using supramaximal stimulation of the soleus nerve, but appeared to be shifted towards longer muscle lengths.

Mechanisms of enhanced force production in lengthening (eccentric) muscle contractions

2014 ◽  
Vol 116 (11) ◽  
pp. 1407-1417 ◽  
Author(s):  
Walter Herzog
Keyword(s):  
Experimental Evidence ◽  
Calcium Binding ◽  
Muscle Activation ◽  
Force Production ◽  
Muscle Length ◽  
Actin Binding ◽  
Structural Protein ◽  
Force Enhancement ◽  
Residual Force ◽  
Residual Force Enhancement

In contrast to isometric and shortening contractions, many observations made on actively lengthening muscles cannot be readily explained with the sliding filament and cross-bridge theory. Specifically, residual force enhancement, the persistent increase in force following active muscle lengthening, beyond what one would expect based on muscle length, has not been explained satisfactorily. Here, we summarize the experimental evidence on residual force enhancement, critically evaluate proposed mechanisms for the residual force enhancement, and propose a mechanism for residual force enhancement that explains all currently agreed upon experimental observations. The proposed mechanism is based on the engagement of the structural protein titin upon muscle activation and an increase in titin's resistance to active compared with passive stretching. This change in resistance from the passive to the active state is suggested to be based on 1) calcium binding by titin upon activation, 2) binding of titin to actin upon activation, and 3) as a consequence of titin-actin binding—a shift toward stiffer titin segments that are used in active compared with passive muscle elongation. Although there is some experimental evidence for the proposed mechanism, it must be stressed that much of the details proposed here remain unclear and should provide ample research opportunities for scientists in the future. Nevertheless, the proposed mechanism for residual force enhancement explains all basic findings in this area of research.

Plasticity in airway smooth muscle: an update

2005 ◽  
Vol 83 (10) ◽  
pp. 841-850 ◽  
Author(s):  
Lincoln E Ford
Keyword(s):  
Muscle Activation ◽  
Smooth Muscles ◽  
Muscle Length ◽  
Thick Filament ◽  
Myosin Filament ◽  
Shortening Velocity ◽  
Tetanic Force ◽  
Substantial Body ◽  
In Series ◽  
Mass Increase

At a similar meeting 10 years ago, we proposed (i) that the long functional range of some smooth muscles is accommodated by plastic alterations that place more myofilaments in series at longer lengths, (ii) that this plasticity is facilitated by myosin filament evanescence, with filaments dissociating partially during relaxation and reforming upon activation, and (iii) that filament lengthening during the rise of activation would cause velocity to fall. Since that meeting, we have accumulated a substantial body of evidence to support these proposals, as follows: (i) muscles develop nearly the same force when adapted to a range of lengths that can vary by 3-fold; (ii) other physiological parameters including shortening velocity, maximum power, compliance, ATPase rate, and thick-filament mass increase by about 2/3 for a doubling of muscle length; (iii) thick-filament density increases substantially during the rise of activation; and (iv) velocity falls as force rises during the rise of tetanic force, and when correction is made for differences in activation, velocity and force vary exactly in inverse proportion. This review explains the rationale for the different experimental measurements and their interpretation.Key words: muscle activation, series-to-parallel transition, myofilaments, myosin.

scholarly journals Ultrasound imaging links soleus muscle neuromechanics and energetics during human walking with elastic ankle exoskeletons

2020 ◽  
Author(s):  
R.W. Nuckols ◽  
T.J.M Dick ◽  
O.N. Beck ◽  
G.S. Sawicki
Keyword(s):  
Metabolic Rate ◽  
Ultrasound Imaging ◽  
Soleus Muscle ◽  
Force Production ◽  
Metabolic Cost ◽  
Flexor Muscle ◽  
Shortening Velocity ◽  
Activation Rate ◽  
Force Activation ◽  
Muscle Contractile

ABSTRACTUnpowered exoskeletons with springs in parallel to human plantar flexor muscle-tendons can reduce the metabolic cost of walking. We used ultrasound imaging to look ‘under the skin’ and measure how exoskeleton stiffness alters soleus muscle contractile dynamics and shapes the user’s metabolic rate during walking. Eleven participants (4F, 7M; age: 27.7 ± 3.3 years) walked on a treadmill at 1.25 m s-1 and 0% grade with elastic ankle exoskeletons (rotational stiffness: 0-250 Nm rad-1) in one training and two testing days. Metabolic savings were maximized (4.2%) at a stiffness of 50 Nm rad-1. As exoskeleton stiffness increased, the soleus muscle operated at longer lengths and improved economy (force/activation) during early stance, but this benefit was offset by faster shortening velocity and poorer economy in late stance. Changes in soleus activation rate correlated with changes in users’ metabolic rate (p = 0.038, R2 = 0.44), highlighting a crucial link between muscle neuromechanics and exoskeleton performance; perhaps informing future ‘muscle-in-the loop’ exoskeleton controllers designed to steer contractile dynamics toward more economical force production.

scholarly journals Ankle Muscle Activations during Different Foot-Strike Patterns in Running

Sensors ◽  
2021 ◽  
Vol 21 (10) ◽  
pp. 3422
Author(s):  
Jian-Zhi Lin ◽  
Wen-Yu Chiu ◽  
Wei-Hsun Tai ◽  
Yu-Xiang Hong ◽  
Chung-Yu Chen
Keyword(s):  
Muscle Activity ◽  
Muscle Activation ◽  
Stance Phase ◽  
Inertial Sensors ◽  
Plantar Flexion ◽  
Intraclass Correlation ◽  
Biceps Femoris ◽  
Ankle Muscle ◽  
Foot Strike ◽  
Muscle Activations

This study analysed the landing performance and muscle activity of athletes in forefoot strike (FFS) and rearfoot strike (RFS) patterns. Ten male college participants were asked to perform two foot strikes patterns, each at a running speed of 6 km/h. Three inertial sensors and five EMG sensors as well as one 24 G accelerometer were synchronised to acquire joint kinematics parameters as well as muscle activation, respectively. In both the FFS and RFS patterns, according to the intraclass correlation coefficient, excellent reliability was found for landing performance and muscle activation. Paired t tests indicated significantly higher ankle plantar flexion in the FFS pattern. Moreover, biceps femoris (BF) and gastrocnemius medialis (GM) activation increased in the pre-stance phase of the FFS compared with that of RFS. The FFS pattern had significantly decreased tibialis anterior (TA) muscle activity compared with the RFS pattern during the pre-stance phase. The results demonstrated that the ankle strategy focused on controlling the foot strike pattern. The influence of the FFS pattern on muscle activity likely indicates that an athlete can increase both BF and GM muscles activity. Altered landing strategy in cases of FFS pattern may contribute both to the running efficiency and muscle activation of the lower extremity. Therefore, neuromuscular training and education are required to enable activation in dynamic running tasks.

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