scholarly journals Intrinsic Properties and Reflex Compensation in Reinnervated Triceps Surae Muscles of the Cat: Effect of Activation Level

2003 ◽  
Vol 90 (3) ◽  
pp. 1537-1546 ◽  
Author(s):  
Clotilde M.J.I. Huyghues-Despointes ◽  
Timothy C. Cope ◽  
T. Richard Nichols
Keyword(s):  
Mechanical Properties ◽  
Stretch Reflex ◽  
Full Range ◽  
Motor Units ◽  
Triceps Surae ◽  
Type I ◽  
Initial Stiffness ◽  
Decerebrate Cat ◽  
Reflex Action ◽  
Triceps Surae Muscles

The manner in which activation levels influence intrinsic muscular properties and contributions of the stretch reflex were studied in homogeneous soleus (SOL) and heterogeneous gastrocnemius (G) muscles in the decerebrate cat. Intrinsic mechanical properties were represented by the initial stiffness of the muscle, measured prior to reflex action, and by the tendency of the muscle to yield during stretch in the absence of the stretch reflex. Stiffness regulation by the stretch reflex was evaluated by measuring the extent to which reflex action reduces yielding and the extent to which stiffness depends on background force. Intrinsic mechanical properties were measured in muscles deprived of effective autogenic reflexes using the method of muscular reinnervation. Reinnervated muscles were recruited to force levels comparable to those achieved during natural locomotion. As force declined during crossed-extension reflexes in reinnervated and intact muscles, initial stiffness declined according to similar convex trajectories. The data did not support the hypothesis that, for a given force level, initial stiffness is greatest in populations of predominantly type I motor units. Incremental stiffness (Δ f/Δ l) of both G and SOL increased in the presence of the stretch reflex. Yielding of SOL (ratio of incremental to initial stiffness) substantially decreased in the presence of the stretch reflex over the full range of forces. In reflexive G, yielding significantly decreased for low to intermediate forces, whereas at higher forces, yielding was similar irrespective of the presence or absence of the stretch reflex. The stretch reflex regulates stiffness in both homogeneous and heterogeneous muscles.

scholarly journals Intrinsic Properties and Reflex Compensation in Reinnervated Triceps Surae Muscles of the Cat: Effect of Movement History

2003 ◽  
Vol 90 (3) ◽  
pp. 1547-1555 ◽  
Author(s):  
Clotilde M.J.I. Huyghues-Despointes ◽  
Timothy C. Cope ◽  
T. Richard Nichols
Keyword(s):  
Triceps Surae ◽  
Variable Delay ◽  
Intrinsic Properties ◽  
Initial Stiffness ◽  
Reflex Action ◽  
Wide Range ◽  
Reflex Compensation ◽  
Triceps Surae Muscles ◽  
Gastrocnemius Muscles ◽  
Decerebrate Cats

Effects of prior motion on ramp stretch responses of reflexive and areflexive muscles were measured in decerebrate cats. Soleus and gastrocnemius muscles were rendered areflexive by reinnervation a minimum of 9 mo before the terminal experiments. The introduction of a shortening phase prior to the ramp stretch increased the normalized initial stiffness of muscles and decreased the tendency to yield of the reinnervated muscles as compared with the case in which muscles contracted isometrically prior to stretch. Yielding was compensated by reflex action for all amplitudes of prior shortening in soleus and gastrocnemius muscles. The comparison of responses of untreated and reinnervated muscles indicated that the contribution of reflex action progressively declined with the amplitude of prior shortening as the extent of yielding diminished. In soleus muscle, during a variable delay period of isometric contraction interposed between shortening and lengthening force generation, initial stiffness and yielding returned to levels seen with isometric contractile history. However, these attributes recovered at different rates, suggesting that distinct processes are responsible for initial stiffness and yielding. Yielding was compensated for by reflex action regardless of the length of the interposed delay or of the amplitude of the prior shortening. These and previous findings indicate that the stretch reflex regulates muscular stiffness for a wide range of conditions. This regulation apparently arises from complementary mechanical properties of intrafusal and extrafusal muscle.

Frequency analysis of stretch reflex and its main subsystems in triceps surae muscles of the cat.

1970 ◽  
Vol 33 (6) ◽  
pp. 713-749 ◽  
Author(s):  
N P Rosenthal ◽  
T A McKean ◽  
W J Roberts ◽  
C A Terzuolo
Keyword(s):  
Frequency Analysis ◽  
Stretch Reflex ◽  
Triceps Surae ◽  
Triceps Surae Muscles

scholarly journals Training-induced increase in Achilles tendon stiffness affects tendon strain pattern during running

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e6764 ◽  
Author(s):  
Amelie Werkhausen ◽  
Neil J. Cronin ◽  
Kirsten Albracht ◽  
Gøran Paulsen ◽  
Askild V. Larsen ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Achilles Tendon ◽  
Stance Phase ◽  
Training Group ◽  
Triceps Surae ◽  
Control Group ◽  
Tendon Stiffness ◽  
Strain Pattern ◽  
Tendon Strain ◽  
Triceps Surae Muscles

Background During the stance phase of running, the elasticity of the Achilles tendon enables the utilisation of elastic energy and allows beneficial contractile conditions for the triceps surae muscles. However, the effect of changes in tendon mechanical properties induced by chronic loading is still poorly understood. We tested the hypothesis that a training-induced increase in Achilles tendon stiffness would result in reduced tendon strain during the stance phase of running, which would reduce fascicle strains in the triceps surae muscles, particularly in the mono-articular soleus. Methods Eleven subjects were assigned to a training group performing isometric single-leg plantarflexion contractions three times per week for ten weeks, and another ten subjects formed a control group. Before and after the training period, Achilles tendon stiffness was estimated, and muscle-tendon mechanics were assessed during running at preferred speed using ultrasonography, kinematics and kinetics. Results Achilles tendon stiffness increased by 18% (P < 0.01) in the training group, but the associated reduction in strain seen during isometric contractions was not statistically significant. Tendon elongation during the stance phase of running was similar after training, but tendon recoil was reduced by 30% (P < 0.01), while estimated tendon force remained unchanged. Neither gastrocnemius medialis nor soleus fascicle shortening during stance was affected by training. Discussion These results show that a training-induced increase in Achilles tendon stiffness altered tendon behaviour during running. Despite training-induced changes in tendon mechanical properties and recoil behaviour, the data suggest that fascicle shortening patterns were preserved for the running speed that we examined. The asymmetrical changes in tendon strain patterns supports the notion that simple in-series models do not fully explain the mechanical output of the muscle-tendon unit during a complex task like running.

Short-term immobilization and recovery affect skeletal muscle but not collagen tissue turnover in humans

2008 ◽  
Vol 105 (6) ◽  
pp. 1845-1851 ◽  
Author(s):  
Britt Christensen ◽  
Eva Dyrberg ◽  
Per Aagaard ◽  
Michael Kjaer ◽  
Henning Langberg
Keyword(s):  
Collagen Synthesis ◽  
Type I Collagen ◽  
Recovery Period ◽  
Triceps Surae ◽  
Muscle Size ◽  
Type I ◽  
Short Term ◽  
Cross Sectional ◽  
Significant Difference ◽  
Triceps Surae Muscles

Not much is known about the effects of immobilization and subsequent recovery on tendon connective tissue. In the present study, healthy young men had their nondominant leg immobilized for a 2-wk period, followed by a recovery period of the same length. Immobilization resulted in a mean decrease of 6% (5,413 to 5,077 mm2) in cross-sectional area (CSA) of the triceps surae muscles and a mean decrease of 9% (261 to 238 N·m) in strength of the immobilized calf muscles. Two weeks of recovery resulted in a 6% increased in CSA (to 5,367 mm2), whereas strength remained suppressed (240 N·m). No difference in Achilles tendon CSA was detected between the two legs at any time point. Local tendon collagen synthesis, measured as the peritendinous concentrations of PINP (NH2-terminal propeptide of type I collagen; indirect marker for collagen synthesis), was unchanged after 2 wk of immobilization. However, peritendinous levels of PINP were significantly elevated in the immobilized leg (15 to 139 ng/ml) following 2 wk of remobilization compared with preimmobilization levels. In contradiction hereto, systemic concentrations of PINP remained unchanged throughout the study. Immobilization reduced muscle size and strength, while tendon size and collagen turnover were unchanged. While recovery resulted in an increase in muscle size, strength was unchanged. No significant difference in tendon size could be detected between the two legs after 2 wk of recovery, although collagen synthesis was increased in the previously immobilized leg. Thus 2 wk of immobilization are sufficient to induce significant changes in muscle tissue, whereas tendon tissue seems to be more resistant to short-term immobilization.

Distribution of Heterogenic Reflexes Among the Quadriceps and Triceps Surae Muscles of the Cat Hind Limb

2003 ◽  
Vol 90 (4) ◽  
pp. 2310-2324 ◽  
Author(s):  
Ronnie J. H. Wilmink ◽  
T. Richard Nichols
Keyword(s):  
Force Feedback ◽  
Joint Stiffness ◽  
Rectus Femoris ◽  
Triceps Surae ◽  
Neural Signals ◽  
Decerebrate Cat ◽  
Wide Range ◽  
Muscle Groups ◽  
Triceps Surae Muscles ◽  
Neural Feedback

Neural signals from proprioceptors in muscles provide length and force-related linkages among muscles of the limbs. The functions of this network of heterogenic reflexes remain unclear. New data are reported here on the distribution and magnitudes of neural feedback among quadriceps and triceps surae muscles in the decerebrate cat. The purpose of this paper was to distinguish whether inhibitory-force feedback is directed against muscles by virtue of the motor-unit composition or articulation of the muscle. These studies were carried out using controlled stretches and measurements of the resulting force responses of individual quadriceps and triceps surae muscles. Responses were evoked over a wide range of background force levels. In agreement with earlier electrophysiological studies, excitatory length feedback strongly linked the vastus muscles, but excitatory reflexes between each vastus and rectus femoris muscles were weak. We also observed a substantial excitatory linkage from the vastus muscles to the soleus muscle. In contrast, force-related inhibition was absent in the heterogenic reflexes among the vastus muscles but strong and bidirectional between each vastus muscle and the rectus femoris muscle and between triceps surae and quadriceps muscles. We conclude that short-latency feedback in the hindlimb is organized according to muscle articulation. Length feedback within muscle groups regulates joint stiffness while interjoint length feedback may compensate for the effects of nonuniform inertial properties of the limb. Force feedback is organized to regulate coupling between joints and, along with length feedback, determine the mechanical properties of the endpoint.

scholarly journals Movement Reduces the Dynamic Response of Muscle Spindle Afferents and Motoneuron Synaptic Potentials in Rat

2004 ◽  
Vol 91 (5) ◽  
pp. 2164-2171 ◽  
Author(s):  
Valerie K. Haftel ◽  
Edyta K. Bichler ◽  
T. Richard Nichols ◽  
Martin J. Pinter ◽  
Timothy C. Cope
Keyword(s):  
Dynamic Response ◽  
Stretch Reflex ◽  
Muscle Spindles ◽  
Triceps Surae ◽  
History Dependence ◽  
Muscle Stretch ◽  
Initial Burst ◽  
Synaptic Potentials ◽  
Probable Effect ◽  
Triceps Surae Muscles

Among the mechanisms that may result in modulation of the stretch reflex by the recent history of muscle contraction is the history dependence observed under some conditions in the response properties of muscle spindles. The present study was designed to test one report that in successive trials of muscle stretch-release, spindle afferent firing during stretch, i.e., the dynamic response shows no history dependence beyond the initial burst of firing at stretch onset. Firing responses of spindle afferents were recorded during sets of three consecutive trials of triangular stretch-release applied to triceps surae muscles in barbiturate-anesthetized rats. All 69 spindle afferents fired more action potentials (spikes) during the dynamic response of the first trial, excluding the initial burst, than in the following two trials. The reduced dynamic response (RDR) was nearly complete after trial 1 and amounted to an average of ∼12 fewer spikes (16 pps slower firing rate) in trial 3 than in trial 1. RDR was sensitive to the interval between stretch sets but independent of stretch velocity (4–32 mm/s). RDR was reflected in the synaptic potentials recorded intracellularly from 16 triceps surae α-motoneurons: depolarization during muscle stretch was appreciably reduced after trial 1. These findings demonstrate history dependence of spindle afferent responses that extends throughout the dynamic response in successive muscle stretches and that is synaptically transmitted to motoneurons with the probable effect, unless otherwise compensated, of modulating the stretch reflex.

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