Dynamics of efferent regulation of muscular contraction. Determination of transients: Efferent stimulation frequency-muscle length

1986 ◽  
Vol 17 (4) ◽  
pp. 334-339 ◽  
Author(s):  
A. I. Kostyukov
Keyword(s):  
Muscle Length ◽  
Muscular Contraction ◽  
Stimulation Frequency

scholarly journals Oxaliplatin neurotoxicity of sensory transduction in rat proprioceptors

2011 ◽  
Vol 106 (2) ◽  
pp. 704-709 ◽  
Author(s):  
Katie L. Bullinger ◽  
Paul Nardelli ◽  
Qingbo Wang ◽  
Mark M. Rich ◽  
Timothy C. Cope
Keyword(s):  
Action Potentials ◽  
Muscle Length ◽  
Sensory Transduction ◽  
Muscle Stretch ◽  
Functional Deficits ◽  
Oxaliplatin Treatment ◽  
Sensory Encoding ◽  
Dying Back ◽  
Striking Contrast

Neurotoxic effects of oxaliplatin chemotherapy, including proprioceptive impairments, are debilitating and dose limiting. Here, we sought to determine whether oxaliplatin interrupts normal proprioceptive feedback by impairing sensory transduction of muscle length and force by neurons that are not damaged by dying-back neuropathy. Oxaliplatin was administered over 4 wk to rats in doses that produced systemic changes, e.g., decreased platelets and stunted weight gain, but no significant abnormality in the terminal ends of primary muscle spindle sensory neurons. The absence of neuropathy enabled the determination of whether oxaliplatin caused functional deficits in sensory encoding without the confounding issue of axon death. Rats were anesthetized, and action potentials encoding muscle stretch and contraction were recorded intra-axonally from dorsal roots. In striking contrast with normal proprioceptors, those from oxaliplatin-treated rats typically failed to sustain firing during static muscle stretch. The ability of spindle afferents to sustain and centrally conduct trains of action potentials in response to rapidly repeated transient stimuli, i.e., vibration, demonstrated functional competence of the parent axons. These data provide the first evidence that oxaliplatin causes persistent and selective deficits in sensory transduction that are not due to axon degeneration. Our findings raise the possibility that even those axons that do not degenerate after oxaliplatin treatment may have functional deficits that worsen outcome.

Peripheral factors influencing expression of pressor reflex evoked by muscular contraction

1985 ◽  
Vol 58 (5) ◽  
pp. 1676-1682 ◽  
Author(s):  
G. A. Iwamoto ◽  
B. R. Botterman
Keyword(s):  
Muscle Mass ◽  
Fiber Type ◽  
Muscle Tension ◽  
Muscle Length ◽  
Muscular Contraction ◽  
Type I ◽  
Active Muscle ◽  
Type Composition ◽  
Slow Twitch Muscle ◽  
Pressor Reflex

The effect of evoked muscle tension, active muscle mass, and fiber-type composition on the pressor reflex evoked by muscular contraction was examined in decerebrate and anesthetized cats. Muscular contraction was induced by stimulating the L7 and S1 ventral roots with 0.1-ms duration pulses three times motor threshold at various frequencies. The experiments were designed to isolate the variable under study as much as possible and included the use of selectively denervated preparations to limit contractions to specific muscles. It was found that altering the evoked tension by varying the resting muscle length had commensurate effects on the pressor reflex (greater evoked tension caused a larger reflex). In addition it was found that changing the amount of active muscle mass caused similar changes in the reflex (the smaller the muscle mass, the smaller the reflex). Finally, it was found that contrary to other accounts, pressor reflexes could be evoked by activation of the slow-twitch muscle soleus, composed exclusively of red (type I) fibers.

scholarly journals High Resolution Determination of Body Segment Inertial Parameters and Their Variation Due to Soft Tissue Motion

2001 ◽  
Vol 17 (4) ◽  
pp. 326-334 ◽  
Author(s):  
Matthew T.G. Pain ◽  
John H. Challis
Keyword(s):  
Soft Tissue ◽  
Plantar Flexion ◽  
Accurate Method ◽  
Muscular Contraction ◽  
Lower Leg ◽  
The Body ◽  
Triceps Surae ◽  
Body Segment ◽  
Inertial Parameters

This study had two purposes: to evaluate a new method for measuring segmental dimensions for determining body segment inertial parameters (BSIP), and to evaluate the changes in mass distribution within a limb as a consequence of muscular contraction. BSIP were calculated by obtaining surface data points of the body under investigation using a sonic digitizer, interpolating them into a regular grid, and then using Green’s theorem which relates surface to volume integrals. Four skilled operators measured a test object; the error was approximately 2.5% and repeatability was 1.4% (coefficient of variation) in the determination of BSIP. Six operators took repeat measures on human lower legs; coefficients of variation were typically around 5%, and 3% for the more skilled operators. Location of the center of mass of the lower leg was found to move up 1.7 cm proximally when the triceps surae muscles went from a relaxed state to causing plantar flexion. The force during an impact associated with such motion of the soft tissue of the lower leg was estimated to be up to 300 N. In summary, a new repeatable and accurate method for determining BSIP has been developed, and has been used to evaluate body segment mass redistribution due to muscular contraction.

In vivo determination of fascicle curvature in contracting human skeletal muscles

2002 ◽  
Vol 92 (1) ◽  
pp. 129-134 ◽  
Author(s):  
Tadashi Muramatsu ◽  
Tetsuro Muraoka ◽  
Yasuo Kawakami ◽  
Akira Shibayama ◽  
Tetsuo Fukunaga
Keyword(s):  
Maximum Voluntary Contraction ◽  
Muscle Length ◽  
Muscle Thickness ◽  
Voluntary Contraction ◽  
Pennation Angle ◽  
Medial Gastrocnemius ◽  
Fascicle Length ◽  
Fascicle Curvature

Fascicle curvature of human medial gastrocnemius muscle (MG) was determined in vivo by ultrasonography during isometric contractions at three (distal, central, and proximal) locations ( n = 7) and at three ankle angles ( n = 7). The curvature significantly ( P < 0.05) increased from rest to maximum voluntary contraction (MVC) (0.4–5.2 m−1). In addition, the curvature at MVC became larger in the order dorsiflexed, neutral, plantar flexed ( P < 0.05). Thus both contraction levels and muscle length affected the curvature. Intramuscular differences in neither the curvature nor the fascicle length were found. The direction of curving was consistent along the muscle: fascicles were concave in the proximal side. Fascicle length estimated from the pennation angle and muscle thickness, under the assumption that the fascicle was straight, was underestimated by ∼6%. In addition, the curvature was significantly correlated to pennation angle and muscle thickness. These findings are particularly important for understanding the mechanical functions of human skeletal muscle in vivo.

The relation between force developed and energy liberated in an isometric twitch

1958 ◽  
Vol 149 (934) ◽  
pp. 58-62 ◽  
Keyword(s):  
Striated Muscle ◽  
Muscle Length ◽  
Creatine Phosphate ◽  
Muscular Contraction ◽  
Quantitative Theory ◽  
A Value ◽  
Wide Range ◽  
Unit Of Length ◽  
Isometric Twitch

The development of force in muscular contraction requires a proportional expenditure of energy, and any quantitative theory of contraction must involve the constant of the propor­tion. In an isometric twitch the energy liberated, as well as the force developed, varies with muscle length; but over a wide range of lengths the ratio P l 0 / H is nearly constant ( P = force developed, l 0 = standard resting length, H = energy liberated). Its actual value depends on the extensibility of the arrangements for recording force; when these were made as inextensible as possible, a value of about 10·3 was obtained. This is still rather too small, because of the compliance of the muscle itself, tendons, etc.; if this compliance could be eliminated the value would be about 13. In striated muscle the ultimate unit of length is the sarcomere. In order to develop a force of 1 dyne in the length of one sarcomere the energy required is about 2 × 10 ‒5 erg; or, assuming that the energy is derived from the splitting and neutralization of ATP and/or creatine phosphate, the number of molecules split is about 2·4 × 10 7 .

Decreasing stimulation frequency-dependent length-force characteristics of rat muscle

1994 ◽  
Vol 77 (5) ◽  
pp. 2115-2124 ◽  
Author(s):  
B. Roszek ◽  
G. C. Baan ◽  
P. A. Huijing
Keyword(s):  
Sarcomere Length ◽  
Muscle Length ◽  
Calcium Sensitivity ◽  
Stimulation Frequency ◽  
Medial Gastrocnemius ◽  
Frequency Dependent ◽  
Contractile System ◽  
Active Peak ◽  
Slack Length ◽  
Force Characteristics

Effects of decreasing stimulation frequency on length-force characteristics were determined for rat medial gastrocnemius muscle. The peripheral nerve was stimulated supramaximally with a succession of twitch and frequencies of 100, 50, 40, 30, and 15 Hz. Active peak tetanic and twitch forces and active muscle geometry were analyzed. Optimal muscle length and active slack length shifted significantly (P < 0.05) to higher muscle length by a maximum of 2.8 and 3.2 mm, respectively. Further significant effects were found for distal fiber length and mean sarcomere length of distal fiber (increases) and for fiber angle and aponeurosis length (decreases). Neither muscle length range between active slack and optimal length nor aponeurosis angle was altered significantly. We concluded that decreasing stimulation frequency-dependent length-force characteristics are affected by a complex interaction of length-dependent calcium sensitivity, potentiation of the contractile system, distribution of sarcomere length, and interactions between force exerted and aponeurosis length. Length-dependent calcium sensitivity seems to be a major factor determining the magnitude of the shift of optimal muscle length.

Determining the Force-Length-Velocity Relations of the Quadriceps Muscles: III. A Pilot Study

1999 ◽  
Vol 15 (2) ◽  
pp. 200-209 ◽  
Author(s):  
John W. Chow ◽  
Warren G. Darling ◽  
James G. Hay ◽  
James G. Andrews
Keyword(s):  
Muscle Length ◽  
Muscle Model ◽  
Model Parameters ◽  
Velocity Data ◽  
Unknown Parameters ◽  
Shortening Velocity ◽  
Maximum Effort ◽  
Low Torque

The purpose of this study was to propose and evaluate a method for the in vivo determination of the force-length-velocity relations of individual quadriceps muscles. One female subject performed maximum effort knee extensions on an isokinetic dynamometer. The gravitational and inertial effects were taken into consideration when determining the resultant knee torque. Selected anatomical and geometric parameters of the quadriceps muscles were obtained from radiography and magnetic resonance imaging (MRI). Hill’s (1938) mechanical model was used to represent the force-velocity relation of a muscle at a given length, and the constants in Hill’s model were assumed to vary with muscle length. Experimentally determined knee torque and muscle shortening velocity data were used to determine the unknown parameters in the muscle model. The relation between each muscle parameter and muscle length for each muscle was obtained using regression analysis. On average, the muscle model overestimated the knee torque by 15.5 ± 5.1%. The overestimations may have resulted from the lack of low torque-high velocity data for the determination of muscle model parameters. When a set of fixed Hill constants was used, the knee torque was underestimated by 29.0 ± 10.6%. The results demonstrate the feasibility of the method proposed in this study.

Sign in / Sign up

Export Citation Format

Share Document