Fast Stretch Research Articles

Evaluation of spasticity by the fast stretch and slow stretch tests

A difference of range of motion is found between the fast stretch and slow stretch on flexors of the hip and knee joints, and on extensors of the ankle joint in early childhood. The difference increases up to 6 months, then sharply decreases at 9 months and diminishes around 18 months after birth. This phenomenon is thought to be due to the development of antigravitic extensor postural tone and maturity of balance reaction. In spastic cerebral palsied children, before the clear appearance of spasticity, the phenomenon is different from that of normal children, with limitation of range of motion or existence of laterality. For high risk babies, the fast and slow stretch tests are considered to be useful in early diagnosis of spasticity.

Role of cross-bridge distortion in the small-signal mechanical dynamics of insect and rabbit striated muscle.

The mechanism of the active tension response of insect fibrillar muscle to step changes and small oscillations of length was re-investigated, following White's demonstration (1983) that the high relaxed stiffness evidently persists during activation and cannot be neglected as had previously been assumed. White's result makes earlier explanations of the small-signal response untenable; the experimental and theoretical studies described here lead to a new class of explanations at the cross-bridge level. The response of an activated muscle to a fast stretch consists of a synchronous tension increase that is followed first by a rapid decay of tension and then by a delayed rise ('stretch activation'). It was shown in glycerinated fibre preparations from the water bug and the bumblebee that subtraction of the relaxed tension response from the active response results in a prominent undershoot of the tension level preceding the step, before the delayed rise of tension. The responses of the same fibres to sinusoidal oscillations, in the frequency range 1-150 Hz, showed an equivalent behaviour, with the active locus circling the relaxed locus in a Nyquist plot, as described by Machin & Pringle (1960). Stiffness was determined during the tension response to a large step (of 1%) by recording the immediate change of tension to a small test step (0.2%), applied at various times after the conditioning step. In the majority of preparations stiffness remained constant or increased during the undershoot of tension. Step and sinusoidal responses with the above features cannot be explained at all by an active component resembling a simple exponential delay. We show, however, that such features are predicted if certain small-signal effects of cross-bridge distortion (previously and erroneously assumed negligible in insect flight muscle for the small-signal case) are incorporated in models of the cross-bridge cycle. Two alternative hypotheses for the effects of distortion are examined: (i) distortion-induced detachments and (ii) distortion-modulated transitions among multiple attached states (Huxley & Simmons, 1971). For the first we also show that the results do not differ qualitatively whether one assumes strain, interfilament displacement or 'bridge recruitment' as the physical correlate of stretch activation. Both of the above explanations account, at least qualitatively, for the observed rapid decay and undershoot of tension following a step increase of length, and for the circling of the active Nyquist-plot loci about the passive locus. The explanation based on distortion-induced detachments, however, appears to be inconsistent with the stiffness measurements.(ABSTRACT TRUNCATED AT 400 WORDS)

Separation of active and passive components of short-range stiffness of muscle.

The short-range stiffness of smoothly but submaximally contracting isometric soleus muscles of anesthetised cats was measured by applying small fast stretches. The ratio of isometric tension to stiffness was plotted against tension over a wide range of muscle lengths and stimulus rates. The results fitted a straight line well, as predicted from crossbridge theory, showing the stiffness to be a function of tension only, independent of the combination of length and stimulus rate used to generate the tension. The major deviation from this line was attributed to incomplete fusion at low frequencies of stimulation. Values believed to be tendon compliance and crossbridge tension per unit of stiffness were found from the graph, and the tendon compliance correlated with the maximum muscle tension. Shortening the tendon by attaching nearer to the muscle changed the results in a manner consistent with the theory, provided that appropriate precautions were taken against slippage.

Mechanical properties of frog skeletal muscles in iodoacetic acid rigor.

1. Methods have been developed for describing the length: tension characteristics of frog skeletal muscles which go into rigor at 4 degrees C following iodoacetic acid poisoning either in the presence of Ca2+ (Ca-rigor) or its absence (Ca-free-rigor). 2. Such rigor muscles showed less resistance to slow stretch (slow rigor resistance) that to fast stretch (fast rigor resistance). The slow and fast rigor resistances of Ca-free-rigor muscles were much lower than those of Ca-rigor muscles. 3. The slow rigor resistance of Ca-rigor muscles was proportional to the amount of overlap between the contractile filaments present when the muscles were put into rigor. 4. Withdrawing Ca2+ from Ca-rigor muscles (induced-Ca-free rigor) reduced their slow and fast rigor resistances. Readdition of Ca2+ (but not Mg2+, Mn2+ or Sr2+) reversed the effect. 5. The slow and fast rigor resistances of Ca-rigor muscles (but not of Ca-free-rigor muscles) decreased with time. 6. The sarcomere structure of Ca-rigor and induced-Ca-free rigor muscles stretched by 0.2lo was destroyed in proportion to the amount of stretch, but the lengths of the remaining intact sarcomeres were essentially unchanged. This suggests that there had been a successive yielding of the weakeast sarcomeres. 7. The difference between the slow and fast rigor resistance and the effect of calcium on these resistances are discussed in relation to possible variations in the strength of crossbridges between the thick and thin filaments.

Comparative study of three stretching techniques.

This study involved comparison of three techniques for increasing range of motion. Fast stretch (ballistic), slow stretch, and IA-CA, a modified version of proprioceptive neuromuscular facilitation (PNF) were compared using 24 normal male Ss. Controlling for serial order effects, 6 groups of 4 Ss each were administered the treatments, and the differences between pre- and post-exercise measures were observed. Multiple regression analysis indicated the superiority of the IA-CA approach.

Effect of procaine on asphyxial rigidity

Procaine (0.2–0.5%) was applied to the motor nerve of the gastrocnemiussoleus muscle of cats showing either “secondary” or “late” tone after asphysiation of the cord for appropriate periods of time. The drug tended to abolish the responses both to sinusoidal slow and fast (0.2–2 cycle/sec) stretch of the muscle before the muscle action potentials elicited by a single shock to the sciatic nerve started to decline. Although secondary tone in contrast to the late tone is characterized by considerable γ-efferent activity, both forms of asphyxial rigidity were similarly affected by procaine. It was, therefore, postulated that, in addition to the selective effect of procaine on the γ-efferents, this local anesthetic also affects the transmission of high frequency impulse trains in the Ia fibers, which represent the sensory input for the myotatic reflex underlying the response of the muscle to stretch. Evidence was obtained that in the concentrations and time of application used to affect the stretch responses procaine impedes the transmission of high frequency trains of impulses.

Electrophysiological and electron microscopic studies on the neuromuscular junction of the crayfish stretch receptors.

1. Investigations on the inhibitory neuromuscular junction of crayfish stretch receptor muscles were performed electrophysiologically and electron microscopically.2. Fast receptor muscles responded to direct stimulation with a transient depolarization which exhibited the property of a propagated action potential, but did not show any overshoot. On the other hand, slow muscles did not generate an action potential but showed excitatory junction potentials of 10-30mV in amplitude. EJPs of fast receptor muscles were summated by repetitive stimulation until all-or-nothing spikes were generated.3. When a nerve bundle was carefully isolated and one of the isolated filaments were stimulated, inhibitory junction potentials could be obtained from fast stretch receptor muscles by the microelectrode inserted near the receptor neuron. They had a reversal potential approximately at-60mV. Inhibitory junction potentials completely inhibited excitatory junction potentials and spikes when inhibitory nerves were stimulated at high frequency of 100c/s for several seconds.4. Application of GABA of 10-4-10-5M showed similar effects to stimulation of inhibitory nerves. It's effect was due to the increase of postsynaptic membrane conductance.5. Two different types of synapses were identified electron microscopically at fast stretch receptor muscles. The one contained spherical synaptic vesicles, the other ellipsoidal ones. The latter was observed within the limit of the vicinity of the neuron soma. From UCHIZONO'S (1965, 1966) previous studies and the present electrophysiological experiments, it was concluded that the latter was the terminal of inhibitory neuromuscular junctions.

Some aspects of the pathophysiology of spasticity and rigidity

New discoveries in relution to the histology and electrophysiology of the muscle spindle show that the stretch reflexes are much more complex at the segmental level than was previously thought, and these must be taken into account in explaining various clinical hypertonias. Thus, the gamma‐1 fibers are believed particularly hyperactive in mild spasticity, while the gamma‐2 system may account for the large tonic stretch reflexes; in the “clasp‐knife” reactions sudden motoneuron inhibition occurs, while ordinarily, as stretch proceeds, more and more motoneurons are recruited. In some types of spasticity, alpha motoneuron hyperexcitability occurs and not the gamma, so that this type is resistant even to dorsal root section. Parkinsonian rigidity, characteristically mild and plastic, is relatively independent of the velocity of stretching, though the response of rigid muscles to fast stretch may be of the “cogwheel” type. Parkinsonian rigidity may be governed by gamma fibers and not maintained by the alpha system, which may account for the rapid and dramatic effect obtained with intramuscular procaine. Complex physiologic work on gamma systems of muscle spindles provides a working hypothesis to account for both spasticity and rigidity as well as for differential action of certain agents. Further work on the dual alpha and gamma systems is urgently needed, as is the development of methods for recording reflex action in man to quantitate spasticity and rigidity.

Stress-relaxation in mammalian gastrocnemius muscle.

Rat whole gastrocnemii (ML) and their medial (M) and lateral (L) heads separately, when stretched 5 mm over resting length at rates of 0.29, 1.16 and 4.71 mm/sec., reach slightly higher levels of passive tension with faster stretches, because the faster the stretch the less is ‘give’ able to keep pace with the stretch. Attained tension of L is less than that of M at all stretch speeds, because ‘give’ occurs more readily in L than in M. The faster the stretch the greater the amount of ensuing fast SR, because the less the amount of tension lost by ‘give’ during stretch the greater the amount of tension left to be lost during ensuing fast SR. The faster the stretch the more residual tension left at 180 seconds; the slower the stretch the less residual tension left at 180 seconds. Slow SR appears to be affected very little by speed of stretch. Fast stretch → high attained tension → more fast SR; slow stretch → low attained tension → less fast SR. There is some ‘give’ at fast stretches in both M and L, with M showing more than L. In attained tension and amount of fast SR, M's behavior is modified more by the presence of L than L's behavior is by the presence of M. It is suggested that the contractile component is responsible for fast SR and noncontractile component for slow SR.

Extensibility of gastrocnemius muscle at rest and during contraction.

The medial head of rat gastrocnemius shows greater static and semidynamic passive tension (per cm2 cross-section area) than the lateral head. Regarded as two resistances in parallel, resistance of lateral and medial heads together (1.16 and 4.71 mm/sec., 1–5 mm stretch) approximate resistance of whole muscle. Resting muscle shows a slow rise and low tension at 0.29 mm/sec., a rapid rise and higher tension at 1.16 mm/sec., and declining tension rise and level with faster stretches. The lateral head yields more readily than the medial head. The lateral head controls whole muscle's reaction to stretch at rest. Tetanized (15 cps) muscle shows a linear, faster tension rise with faster stretches. Excess (over isometric) tension, related to resting stretch tension, shows a decline with stretch (yielding). The amount of excess tension increases with speed of stretch. The lateral head shows less excess tension rise than the medial head. The medial head controls whole muscle's reaction to stretch during isometric tetanus.

Rise of Temperature on Fast Stretching of Butyl Rubber

Abstract Study of the rise in temperature by fast stretching of Butyl gum and tread stocks throws considerable light on crystallization, internal friction, and carbon black reënforcement as functions of elongation and other possible variables. For low elongations, the low-heat curves show the occurrence of thermoelastic inversion. They show also that internal friction is much larger in Butyl than in Hevea. For high elongations the high-heat curves enable one to follow the late and abrupt crystallization so characteristic for Butyl stocks. The carbon black reënforcement of Butyl is followed for the whole range of elongations up to the breaking point. Specific carbon-black reënforcement takes place in the range of elongations before crystallization of the gum stock, but the shortening of the breaking elongation by the black excludes to a large extent the added reënforcement through crystallization. Physical measurements of the type reported in this paper serve a manifold purpose. They enable one to establish a correlation between physical properties and chemical structure. Such a correlation is simpler for fundamental physical properties, as the ΔT vs. ε curve, than for more complicated physical tests, as data from flexometer, which were designed to approach service conditions. Comparing different gum stocks with Butyl polymers among themselves and with Hevea or other synthetics, these measurements may guide the development of better Butyl polymers. Finally, comparing tread with gum stocks, they may help to recognize the nature of reënforcing by carbon blacks and the action of other compounding ingredients.

Rise of Temperature on Fast Stretching of Butyl Rubber

The rise of temperature on fast stretching of natural and synthetic rubber stocks was investigated recently by Dart, Anthony, and Guth (D.A.G.). Since then the experimental technique was considerably improved and the taking of data greatly simplified thereby. By D.A.G. emphasis was placed to record temperature rises of up to 15°C for extensions up to 700 percent by a fast galvanometer of moderate sensitivity. In the present work this high heat was investigated. In addition, however, a less fast but more sensitive galvanometer was employed to record changes of temperature as small as 0.001°C for 0–80 percent extension. In accordance with early work by Joule on natural gum (1859) it was found that also Butyl gum stocks show an initial cooling effect. This passes at a thermoelastic inversion point into a heating effect. In agreement with the recent theory by James and Guth the thermoelastic inversion point was found to depend solely upon the thermal expansion coefficient of the unstretched stock. The coefficient of thermal expansion was measured for Butyl stocks in the present work. Butyl tread stocks also show the thermoelastic inversion point. The work of D.A.G. showed that the rise in temperature on extension is a slowly rising function of the extension with a steep upward turn and almost linear continuation after the onset of crystallization. The samples were kept extended for a minute and then the cooling arising on retraction also measured. The negative of the cooling on retraction plotted against extension fall, according to the second law of thermodynamics as it should under the extension curve, but crosses it at the onset of crystallization. For Butyl gum stocks this crossing takes place at rather high (600 percent or more) extensions in agreement with x-ray work. More similarity was found between Butyl and Hevea tread stocks than between the corresponding gum stocks. Loading shifts the onset of crystallization to a range of smaller extensions. In addition to measuring the change of temperature on extension and retraction, the residual rise in temperature after an extension and immediate fast cycle retraction was also observed. This quantity is a measure of internal friction in Butyl rubber and is closely connected with rebound and free vibration tests. Summarizing, the method described has a twofold application for development work: 1. Changes of the temperature on extension and delayed retraction indicate in a simple manner the onset and progress of crystallization. 2. Changes of the temperature in a fast cycle give an estimate for internal friction. Both these applications will facilitate attempts to improve present synthetics.

Rise of Temperature on Fast Stretching of Synthetics and Natural Rubbers

Abstract This investigation covered more types of rubber and rubberlike synthetics than were studied by previous investigators. From the results it seems apparent that at least a part of the disagreement between previous workers on this subject is due to the different types of rubber employed. It is also important to note that the temperature changes observed were of the order predicted by sensory observation.

Rise of Temperature on Fast Stretching of Synthetics and Natural Rubbers

Abstract This investigation covered more types of rubber and rubberlike synthetics than were studied by previous investigators. From the results it seems apparent that at least a part of the disagreement between previous workers on this subject is due to the different types of rubber employed. It is also important to note that the temperature changes observed were of the order predicted by sensory observation.