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Letteratura scientifica selezionata sul tema "Stretch reflex"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 1 agosto 2024

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Articoli di riviste sul tema "Stretch reflex"

Cleland, C. L., e W. Z. Rymer. "Neural mechanisms underlying the clasp-knife reflex in the cat. I. Characteristics of the reflex". Journal of Neurophysiology 64, n. 4 (1 ottobre 1990): 1303–18. http://dx.doi.org/10.1152/jn.1990.64.4.1303.

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Abstract (sommario):

1. The goal of this study was to characterize the clasp-knife reflex by the use of stretch and isometric contraction of ankle extensor and flexor muscles in decerebrated cats with bilateral dorsal hemisections of their spinal cords at segment T12. 2. Stretch of an extensor muscle evoked inhibition in both homonymous and synergistic extensor muscles. The similarities between homonymous and synergistic inhibition suggest that similar neural mechanisms were responsible. 3. Homonymous and synergistic clasp-knife inhibition showed several characteristic features: 1) inhibition was evoked only by large stretches that produced significant muscle force. Short stretches that did not produce large forces evoked only excitation; 2) the magnitude of clasp-knife inhibition increased with increasing initial motor output, as reflected in the level of rectified EMG; 3) the time course of reflex inhibition evoked by ramp-and-hold stretch was characterized by segmentation of EMG during ramp stretch, dynamic overshoot of inhibition at the end-of-ramp stretch, and slow but usually complete decay of inhibition during maintained stretch; 4) inhibition persisted beyond the termination of stretch, and 5) inhibition showed adaptation to repeated stretch. 4. Isometric contraction of the soleus or medial gastrocnemius, produced by electrical stimulation of the muscle nerve, also evoked powerful synergistic-reflex inhibition via similar mechanisms as stretch-evoked, clasp-knife inhibition. Stretch evoked a greater degree of inhibition than did contraction, indicating that receptors responsive to both stretch and contraction contribute to clasp-knife inhibition. 5. The reflex effects produced by stretching the soleus or medial gastrocnemius were not confined to the homonymous and close synergistic muscles. Extensor muscles were inhibited and flexor muscles were excited throughout the hindlimb, which paralleled the pattern of a flexion-withdrawal reflex evoked by cutaneous stimulation. 6. Stretch of a flexor muscle, the tibialis anterior, evoked the same spatial pattern and time course of reflex action as stretch of an extensor muscle--inhibition of extensor muscles and excitation of flexor muscles throughout the hindlimb, including homonymous excitation of the tibialis anterior. 7. We conclude that neither Golgi tendon organs nor secondary spindle afferents are likely to contribute significantly to clasp-knife inhibition because their responses to stretch and isometric contraction differ from the reflex actions evoked by stretch and contraction.(ABSTRACT TRUNCATED AT 400 WORDS)

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Sinkjaer, T., J. B. Andersen e B. Larsen. "Soleus stretch reflex modulation during gait in humans". Journal of Neurophysiology 76, n. 2 (1 agosto 1996): 1112–20. http://dx.doi.org/10.1152/jn.1996.76.2.1112.

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Abstract (sommario):

1. The modulation of the short-latency stretch reflex during walking at different walking speeds was investigated and compared with the stretch reflex during standing in healthy human subjects. 2. Ankle joint stretches were applied by a system able to rotate the human ankle joint during treadmill walking in any phase of the step cycle. The system consisted of a mechanical joint attached to the subject's ankle joint and connected to a motor placed beside the treadmill by means of bowden wires. The weight of the total system attached to the leg of the subject was 900 g. 3. The short-latency soleus stretch reflex was modulated during a step. In the stance phase, the amplitude equaled that found during standing at matched soleus background electromyogram (EMG). In the transition from stance to swing, the amplitude was 0 in all subjects. In late swing, the stretch reflex amplitude increased to 45 +/- 27% (mean +/- SD) of the maximal amplitude in the stance phase (stretch amplitude 8 degrees, stretch velocity 250 degrees/s). 4. The onset (42 +/- 3.2 ms) and peak latencies (59 +/- 2.5 ms) of the stretch reflex did not depend on the phase in the step cycle at which the reflex was elicited. 5. When the ankle joint is rotated, a change in torque can be measured. The torque measured over the first 35 ms after stretch onset (nonreflex torque) was at a maximum during late stance, when the leg supported a large part of the body's weight, and at a minimum during the swing phase. At heel contact the nonreflex torque was 50% of its maximal value. 6. During the stance phase the maximal EMG stretch reflex had a phase lead of approximately 120 ms with respect to the maximal background EMG and a phase lead of approximately 250 ms with respect to the maximal nonreflex torque. 7. The constant latency of the stretch reflex during a step implied that the ankle extensor muscle spindles are always taut during walking. 8. The relatively high amplitude of the stretch reflex in late swing and at heel contact made it likely that the stretch reflex contributed to the activation of the ankle extensor muscles in early stance phase.

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Cleland, C. L., L. Hayward e W. Z. Rymer. "Neural mechanisms underlying the clasp-knife reflex in the cat. II. Stretch-sensitive muscular-free nerve endings". Journal of Neurophysiology 64, n. 4 (1 ottobre 1990): 1319–30. http://dx.doi.org/10.1152/jn.1990.64.4.1319.

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Abstract (sommario):

1. The goal of this study was to determine the contribution of muscular free nerve endings to the clasp-knife reflex by comparing their response properties and reflex actions to the clasp-knife reflex. 2. The responses of single muscle afferents were examined in anesthetized cats using stretch and isometric contraction of ankle extensor muscles identical to those that evoked clasp-knife inhibition in decerebrated and dorsal spinal-hemisectioned cats. 3. Fifty-three stretch-sensitive mechanoreceptor afferents were identified as free nerve ending afferents based on their conduction velocities, location within the muscle, uniformity of response, and dissimilarity to other muscle proprioceptors. The afferent conduction velocities were in both the group III (56%) and group II (44%) range, including five fast-conducting group II afferents (greater than 55 m/s). 4. The stretch response of stretch-sensitive, free nerve endings (SSFNEs) showed several characteristic features: 1) afferents were excited only by large stretches that produced significant passive force; 2) afferent activity began after a brief delay and exhibited segmentation of discharge during ramp stretch, a maximum at the end of ramp stretch, and rapid and complete decay during static stretch, and 3) afferent response adapted to repeated stretches. These properties match those of clasp-knife inhibition described in the companion paper, except that the SSFNE segmentation and maximum were more pronounced and their decay during maintained stretch was more rapid. 5. Isometric contraction produced by electrical stimulation of the muscle nerve, which induced force-evoked inhibition in decerebrated and dorsal hemisectioned cats, also consistently excited SSFNEs. Stretch evoked greater excitation than contraction, indicating that both length and force contribute to SSFNE activity. 6. Stimulation of free nerve endings by squeezing the achilles tendon in cats exhibiting the clasp-knife reflex evoked powerful, homonymous inhibition and a flexion-withdrawal pattern of reflex action--that is, inhibition of extensor and excitation of flexor muscles throughout the hindlimb, which parallels the spatial divergence of the clasp-knife reflex. 7. Intrathecal application of capsaicin, which preferentially blocks the reflex actions of small afferent fibers, blocked clasp-knife inhibition in decerebrated, dorsal hemisectioned cats. 8. The similarities between the reflex actions and response properties of SSFNEs and the properties of the clasp-knife reflex suggest that SSFNEs mediate clasp-knife inhibition.(ABSTRACT TRUNCATED AT 400 WORDS)

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Sobkowiak, Carole A. "Stretch Reflex Facts". Physiotherapy 81, n. 9 (settembre 1995): 575. http://dx.doi.org/10.1016/s0031-9406(05)66710-7.

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Obeso, J. A., J. Artieda e C. D. Marsden. "Stretch reflex blepharospasm". Neurology 35, n. 9 (1 settembre 1985): 1378. http://dx.doi.org/10.1212/wnl.35.9.1378.

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Stein, R. B., I. W. Hunter, S. R. Lafontaine e L. A. Jones. "Analysis of short-latency reflexes in human elbow flexor muscles". Journal of Neurophysiology 73, n. 5 (1 maggio 1995): 1900–1911. http://dx.doi.org/10.1152/jn.1995.73.5.1900.

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Abstract (sommario):

1. A motor and digital controller have been developed to apply rapid stretches to the human elbow joint. The digital controller returns the forearm to the initial position before the reflex contraction. Thus short-latency reflex responses can be cleanly separated in time from the mechanical effects of the stretch under a wide variety of loading conditions. 2. The reflex force varies linearly with the velocity of stretch over nearly 2 orders of magnitude. The reflex force also varies linearly with the tonic level of force over the entire range of forces studied (0-100 N). This contrasts sharply with, for example, the human ankle joint, which shows a very limited linear range. 3. As the digital controller is made more compliant (less stiff), reflex shortening increases dramatically and becomes more prolonged, whereas the reflex force becomes somewhat smaller and shorter. With compliant loads and the brief stretches we applied, the reflex shortening is approximately equal to the stretch that generated it. 4. Simulations of the results confirm that the dependence of reflex shortening and force on the stiffness of the load is mainly determined by the mechanics of the limb and muscles. The simulations also indicate that 1) the gain of the reflex is as high as it can be without causing instability and 2) the presence of a rectification nonlinearity (e.g., lengthening the muscle produces a reflex, but shortening the muscle does not) is mainly responsible for preserving the stability of the elbow system.

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Nicol, Caroline, e Paavo V. Komi. "Quantification of Achilles Tendon Force Enhancement by Passively Induced Dorsiflexion Stretches". Journal of Applied Biomechanics 15, n. 3 (agosto 1999): 221–32. http://dx.doi.org/10.1123/jab.15.3.221.

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Magnitude of the reflex contribution to force enhancement was investigated in vivo during passive stretches of the Achilles tendon (AT) of one female subject. Thirty passive (5 × 6) dorsiflexions were induced by a motorized ankle ergometer. Achilles tendon force (ATF) was sensed by a buckle transducer applied surgically around the right AT. Single passive stretches resulted in a low but rather linear ATF increase in the absence of EMG (surface electrodes) activity. In the presence of reflexes, a clear ATF enhancement occurred 13–15 ms after the beginning of the EMG reflex responses. In double dorsiflexions at either 1.2 or 1.9 rad · s-1, which were separated by a maintained stretched position of either 40 or 90 ms, the first stretch resulted in initial linear ATF increase, followed by an additional force enhancement during the plateau phase. This reflexly induced increase represented 94 ± 4 N and 184 ± 1 N, respectively, for the 40 and the 90 ms plateaus, corresponding to 210 ± 85% and 486 ± 177% enhancements as compared to the first passive stretch effect. The results suggest further that timing of the stretch during the twitch response influences the magnitude and rate of force potentiation.

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Miller, J. F., K. D. Paul, W. Z. Rymer e C. J. Heckman. "5-HT1B/1D agonist CGS-12066B attenuates clasp knife reflex in the cat". Journal of Neurophysiology 74, n. 1 (1 luglio 1995): 453–56. http://dx.doi.org/10.1152/jn.1995.74.1.453.

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Abstract (sommario):

1. The effect of intrathecal injection of the selective serotonin (5-HT)1B/1D receptor agonist CGS-12066B maleate (825 nmol) was assessed on stretch-evoked clasp knife inhibition of hindlimb ankle extensor muscle reflex force in precollicular decerebrate cats in which neural transmission in dorsolateral spinal pathways was blocked bilaterally by focal cooling. 2. During cold block, ramp and hold stretches of the medial gastrocnemius muscle (MG) evoked only a brief reflex excitation that was followed by powerful, long-lasting inhibition (the clasp knife reflex). Both the amplitudes of peak force evoked by the ramp and sustained force output during the last 500 ms of the hold phase of the stretch were depressed by > 50%. 3. Reflex force output during the hold portion of stretch was significantly improved on postdrug cold block trials, although peak force remained depressed. CGS-12066B did not significantly alter stretch-evoked force output in decerebrate cats when spinal cord neural transmission was unimpaired. 4. These data suggest that selective 5-HT1B/1D agonists may be of therapeutic usefulness in the treatment of reflex disorders arising from partial spinal cord injury.

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Cronin, Neil J., Jussi Peltonen, Masaki Ishikawa, Paavo V. Komi, Janne Avela, Thomas Sinkjaer e Michael Voigt. "Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae". Journal of Applied Physiology 105, n. 1 (luglio 2008): 226–32. http://dx.doi.org/10.1152/japplphysiol.90432.2008.

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Abstract (sommario):

The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8°; 250°/s) were applied to the triceps surae at different moment levels (0–100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths. At low forces, reflex amplitudes increased despite a lack of change or even a decrease in fascicle stretch velocities. At high forces, lower fascicle stretch velocities coincided with smaller stretch reflexes. The results revealed a decline in fascicle stretch velocity of over 50% between passive conditions and maximal force levels in the major muscles of the triceps surae. This is likely to be an important factor related to the decline in stretch reflex amplitudes at high forces. Because short-latency stretch reflexes contribute to force production and stiffness regulation of human muscle fibers, a reduction in afferent feedback from muscle spindles could decrease the efficacy of human movements involving the triceps surae, particularly where high force production is required.

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Miller, J. F., K. D. Paul, R. H. Lee, W. Z. Rymer e C. J. Heckman. "Restoration of extensor excitability in the acute spinal cat by the 5-HT2 agonist DOI". Journal of Neurophysiology 75, n. 2 (1 febbraio 1996): 620–28. http://dx.doi.org/10.1152/jn.1996.75.2.620.

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Abstract (sommario):

1. The decerebrate cat preparation with an intact spinal cord is characterized by a high degree of excitability in extensor motoneuron pools, which is eliminated by acute spinalization. Subtype-specific agonists for serotonin (5-HT) were investigated in terms of their effectiveness in restoring the extensor excitability following spinalization. 2. Our hypothesis was that 5-HT2 receptors have the primary role in enhancement of extensor reflex excitability, whereas 5-HT1A and 5-HT1B/D receptors are relatively unimportant. Reflex excitability was assessed from the tonic levels of force and electromyographic (EMG) output from the ankle extensors medial gastrocnemius (MG) and soleus (SOL), and from the reflex forces in both these muscles generated by ramp-and-hold stretches of MG. 3. Before spinal transection, MG and SOL usually exhibited a small amount of tonic background EMG activity and force output. Ramp-and-hold stretch of MG generated a large-amplitude reflex response. Spinal transection at the level of T10 virtually abolished tonic background activity in both extensors and greatly attenuated the MG stretch reflex. Ventral topical application of the selective 5-HT2A/2C agonist (+-)-1-(2,5-dimethoxy-4-iodophenyl)-2-amino-propane hydrochloride (DOI) restored the amplitude of the MG stretch reflex in a dose-dependent fashion. However, a considerable portion of the DOI-mediated restoration of MG stretch reflex force was due to elevation of tonic background force levels above previous intact cord levels. 4. The DOI-induced increase in extensor tonic background excitability and facilitation of MG stretch reflex were reversed by ventral topical administration of the selective 5-HT2 antagonist ketanserin. No increase in extensor excitability was observed in spinalized preparations after administration of either the 5-HT1A agonist (+-)-8-hydroxy-dipropylaminotetralin hydrobromide or the 5-HT1B/1D agonist 7-trifluoromethyl-4-(4 methyl-1-piperazinyl)-pyrrolo[1,2- a]quinoxaline maleate. These data strongly suggest that the DOI-induced facilitation of extensor stretch reflex and tonic activity in spinalized preparations is mediated through an action on spinal 5-HT2 receptors. 5. One important difference between the actions of DOI in spinalized versus intact states was that the DOI-induced tonic and reflex forces in the spinalized state were subject to irregular oscillations. In contrast, DOI did not noticeably affect the smoothness of reflex force generation in the intact state. This discrepancy was probably due to the effects of clasp knife inhibition from muscular free nerve endings, which have potent reflex actions in the spinalized but not intact states. Thus DOI elevated excitability levels but did not alter the effects of spinalization on stretch reflex patterns.

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Più fonti

Tesi sul tema "Stretch reflex"

Cathers, Ian Electrical Engineering &amp Telecommunications Faculty of Engineering UNSW. "Stretch signal and muscle state dependence of the tonic stretch reflex". Awarded by:University of New South Wales. School of Electrical Engineering and Telecommunications, 2000. http://handle.unsw.edu.au/1959.4/17807.

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Abstract (sommario):

When active skeletal muscle is stretched, it generally responds with a contraction which resists the stretch. This response is termed the muscle stretch reflex. The size (gain) and timing (phase) of the response has been found to depend on many factors including the characteristics of the applied stretch, the muscle contraction level and the subject's intention. Investigations of this stretch reflex have often involved stretches to muscle which contained frequencies either beyond the range of voluntary movement or else which could be consciously tracked. This study sought to characterise the frequency response of the stretch reflex, in terms of its gain and phase, under a variety of conditions while using stretches to the muscle which were relevant to voluntary movement, yet which were too irregular to be tracked. The types of stretch which satisfied these criteria had first to be determined by an investigation of tracking performance under different conditions of peripheral feedback. Having established the types of stretch which could be used to guarantee reflex rather than voluntary responses, the stretch reflex was investigated using stretches of different amplitude and bandwidth and spanning the full range of contraction level. Research was also undertaken to determine whether the gain and phase of the reflex response could be decoupled from the background contraction level of the muscle and to examine any associated effects on the mechanical properties of the limb. Explanatory models for some of these reflex responses were developed. An interaction between normal physiological tremor and the stretch reflex response was also investigated.

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Bock, Przemek John. "Modulation of stretch reflex excitability in quiet human standing". Thesis, McGill University, 2005. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=82471.

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Stretch reflex excitability was measured during quiet standing by using a bilateral electro-hydraulic actuator to apply perturbations of angular position to the ankle. Subjects were instructed to stand quietly while pulse displacements were applied at random times. Position, torque, gastrocnemius-soleus EMG, tibialis anterior EMG, heel position, tibia angle, femur angle, and sacrum angle were measured. Background torque and reflex excitability varied substantially from trial to trial---reflex torque decreased as the background torque level increased; while reflex EMG increased when background torque increased. This behavior is consistent with previous findings in prone subjects. Reflex torque for a given activation level was found to vary with the initial torque derivative---reflex excitation was greater for negative torque derivatives than their positive counterparts. These findings suggest that reflex excitability in quiet human standing is modulated to optimize balance.

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Duncan, Audrey. "Reflex modulation in human movement and posture". Thesis, University of Birmingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.367627.

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Human soleus H-reflex gain was measured in supine lying and in standing vertically while stabilised by a backboard. H-reflex amplitude was less in stabilised standing than in supine lying. The reduction was partly due to the effect of gravitational load. When the same load was applied (by compression of the body between shoulders and feet) while lying supine the corresponding reduction was 70%. The results are discussed in relation to possible gravitational load receptors. In a second series of experiments a collapsible landing platform was used to differentiate between reflex and programmed contributions to EMG activity in landing from a jump. Post-landing activity of the calf muscles was a short latency spinal reflex triggered by ankle rotation. In the rectus femoris muscle, activity was programmed for short falls and had a reflex component in longer falls. When the collapsible platform caused a landing to occur at a time later than anticipated, reflex gain was increased in the gastrocnemius, biceps femoris and rectus femoris muscles. Experimental results were consistent with the time that would be required for descending pathways to modulate the reflex gain and an appropriate model is proposed.

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Arbat, i. Plana Ariadna. "Modulation of the stretch reflex arc to improve functional recovery after peripheral nerve injury". Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/394061.

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Després d’una lesió del sistema nerviós perifèric, aquest té la capacitat de regenerar però la seva recuperació funcional sol ser limitada, principalment degut a la inespecificitat de la reinnervació dels òrgans perifèrics i als canvis plàstics maladaptatius de la circuiteria espinal. En aquesta tesi hem volgut modular els canvis a la circuiteria espinal del reflex d’estirament per poder millorar la recuperació funcional després de lesions del nervi perifèric en un model animal. En primer lloc, es va dur a terme una caracterització immunohistoquímica dels canvis que patien les motoneurones espinals després d'una lesió del nervi ciàtic; aquests canvis es van estudiar en animal postnatal i en l’adult. En els animals postnatals, també es va estudiar la composició sinàptica de l’arbre dendrític de les neurones, i es va observar una elevada pèrdua de sinapsis excitatòries que no s’arriben a recuperar després de 2 mesos. Pel que fa als canvis produïts en l’adult, vam observar que la màxima pèrdua de sinapsis glutamatèrgiques i de xarxes perineurals (PNN) es produïa dues setmanes després de la lesió, amb una progressiva recuperació a partir de la quarta setmana. Per intentar atenuar aquesta pèrdua sinàptica i de PNN, vam estudiar l’efecte de l’estimulació elèctrica i de la capacitat de diferents factors tròfics (aplicats a la zona de lesió mitjançant una matriu de col·lagen en un tub de silicona). No es van obtenir diferències significatives en cap de les dues teràpies. També vam avaluar diferents protocols d'exercici físic, concretament l’exercici forçat, voluntari i passiu. Si es feia servir un protocol d’alta intensitat, la pèrdua sinàptica i de PNN que patien les motoneurones era menor que la pèrdua observada en les motoneurones d'animals que no havien estat sotmesos a exercici, mentre que en aquells que corrien menys no presentaven millores respecte als animals no exercitats A més, en els animals exercitats també vam observar un augment de l’astrogliosis al voltant de les motoneurones axotomitzades i una disminució de l’activació de la microglia, excepte en l’exercici voluntari i passiu a baixa intensitat, on vam observar un augment de l’activació de microglia. Degut als efectes positius induïts per l’exercici físic sobre els canvis plàstics en el nostre model, vam valorar potencials mecanismes implicats en aquestes efectes. Tot i que se sap que l’exercici incrementa l’expressió de neurotrofines, es desconeix com l'exercici modula aquestes neurotrofines i quines són les seves accions específiques. Per valorar el paper del BDNF en els efectes de l'exercici observats en el nostre model, vam administrar sistèmicament un agonista i un antagonista del TrkB. Vam observar que el manteniment de les sinapsis mediat per l'exercici físic depenia parcialment de l’activació del TrkB, però l'activació farmacològica d'aquest receptor no mimetitzava els efectes de l'exercici. Com que l'exercici físic provoca un augment de l'activitat neural, també vam valorar el paper de les projeccions descendents noradrenèrgiques del tronc de l'encèfal en els efectes moduladors de l'exercici sobre les motoneurones. Aquestes vies descendents modulen l'excitabilitat de les motoneurones espinals i s'activen en situació d’estrès, com l'exercici forçat. Mitjançant l’administració de DSP-4, que destrueix el locus coeruleus i per tan, provoca la pèrdua de les projeccions noradrenergiques descendents, vam veure una reducció de PNN i una marcada reactivitat de la microglia. En els animals sotmesos a exercici, la pèrdua d'aquestes projeccions impedia la preservació de sinapsis i de PNN al voltant de les motoneurones lesionades, si bé la reactivitat microglial es veia igualment disminuïda. Aquestes troballes suggereixen que la modulació dels canvis espinals induïts per l'exercici físic seria parcialment dependent de l'activació d'aquestes projeccions noradrenèrgiques, mentre que la modulació de la micròglia per l'exercici en seria independent
After a peripheral nerve injury, axons are able to regenerate but functional recovery is usually limited, mainly due to unspecific reinnervation of target organs and also to maladaptive plastic changes in the spinal circuitry. In this thesis we wanted to modulate the stretch reflex arc to improve functional recovery after peripheral nerve lesions in animal model. Firstly, we carried out an immunohistochemical characterization of the changes surrounding spinal motoneurons after sciatic nerve injury; these changes were studied in postnatal and adult animals. In postnatal animals, we also studied VGlut1 contacts along dendrites, observing a high loss of excitatory synapses that were not recovered at 2 months. Regarding adult motoneurons, we found that the maximum loss of glutamatergic synapses and perineuronal nets (PNN) took place two weeks after injury, with a progressive recovery at 4 weeks. To try to ameliorate this loss of synapses and PNN, we studied the effect of electrical stimulation and different trophic factors (applied directly to the injury with a collagen matrix in a silicone tube). No significant differences were observed in none of them. We also evaluated different exercise protocols, specifically forced, voluntary and passive exercise. A high intensity protocol was able to partially prevent the synaptic and PNN loss that suffer axotomized motoneurons, whereas low intensity programs did not show significant differences compared to untrained ones. We also observed an increase of astrogliosis surrounding axotomized motoneurons and a decrease of microglia activation in exercised animals, except for those receiving low intensity voluntary and passive exercise, where there was a significant increase of microglia. Due to the positive effects induced by physical exercise on central plastic changes, we evaluate potential mechanisms involved in these effects. Although it is known that exercise increase neurotrophins, it is unknown how exercise modulates these neurotrophins and their specific actions. To evaluate the role of BDNF in the effects of exercise on axotomized motoneurons, we systemically administered a TrkB agonist and antagonist. We observed that the maintenance of synapses mediated by exercise was partially dependent of TrkB activation, but pharmacological activation of this receptor did not mimic exercise effects. As after physical exercise there was an increase of neural activity, we studied the role of noradrenergic descending projections from brainstem in spinal cord motoneurons after exercise. These descending pathways modulate excitability of the spinal motoneurons and are activated by stress situations, such as forced exercise. By DSP-4 administration, we provoked the desestructuration of the Locus Coeruleus and thus, loss of noradrenergic descending projections, observing a reduction of PNN and a marked reactivity of microglia. In animals submitted to exercise, the loss of these projections prevented the preservation of synapses and PNN around injured motoneurons, although microglial reactivity was also decreased. These findings suggest that modulation of spinal changes induced by physical exercise would be partially dependent on the activation of noradrenergic projections, whereas the modulation of microglia is independent of the exercise.

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Tung, James 1975. "Task-dependent modulation of stretch reflex stiffness in the ankle". Thesis, McGill University, 2002. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=79266.

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Abstract (sommario):

The stretch reflex is an involuntary contraction produced in response to muscle stretch. Despite extensive research, its role in the control of movement and posture remains controversial. One reason for this is that the torque output produced by reflex activity has been studied in only a limited number of tasks and behaviours. The main thrust of this thesis is to examine whether the central nervous system (CNS) modifies stretch reflex properties to suit the task.
An electro-hydraulic actuator applied perturbations to the ankles of five subjects while they performed position-matching (PM) and torque-matching (TM) tasks. Stretch reflex properties were determined using a new closed-loop, reflex identification algorithm that analytically separated the torques produced by stretch reflexes from the overall ankle torque. Stretch reflex gain was greater in the PM task than for the TM task, under matched conditions.

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Calota, Andra. "Reliability of spasticity measurement based on tonic stretch reflex threshold". Thesis, McGill University, 2008. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=111947.

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Studies suggest that deficits in central regulation of stretch reflex thresholds (SRT) underlie both spasticity and other disorders of motor control. We investigated intra- and inter-evaluator reliability to quantify spasticity based on tonic SRT (TSRT) and the relationship between TSRT and Modified Ashworth Scale (MAS, clinical assessment of resistance to stretch). Spasticity was evaluated in 20 subjects with chronic stroke-related spasticity in two different days, by three evaluators. Twenty different velocity-dependent dynamic SRT (angle where biceps brachii EMG signal increased for a given velocity of stretch) were recorded. TSRT (excitability of motoneurons at 0°/sec) was then computed. Spasticity was also estimated with MAS. Reliability was moderately good for subjects with moderately high spasticity (intra--evaluator: 0.46 to 0.68, inter--evaluator: 0.53 to 0.68). There was no correlation between TSRT and MAS since they measure different phenomena. TSRT is a promising new measure of spasticity. Further improvements for its quantification are suggested.

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Vedula, Siddharth. "Ankle stretch reflexes during anticipatory postural adjustments". Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:8881/R/?func=dbin-jump-full&object_id=32517.

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Horstman, Gabrielle Marie. "Limitations of Functional Recovery of Stretch Reflex Circuitry After Peripheral Nerve Regeneration". Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1347852976.

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Salazar-Torres, Jose de Jesus. "Biomechanical analysis of stretch reflex responses : an approach to spasticity measurement". Thesis, University of Newcastle Upon Tyne, 2005. http://hdl.handle.net/10443/2038.

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Spasticity is a clinical condition that may develop in people with central nervous system injuries. It is believed that spasticity results from changes in the excitability of the stretch reflex pathways manifesting clinically as a velocity dependent increase in resistance to passive movement (RTPM) and exaggerated tendon jerks. Stretch reflex excitability is influenced by neural (e.g. feed-forward and feedback mechanisms) and biomechanical components (e.g. muscle length). The objective of this work was to quantify the stretch reflex parameters of the biceps brachii under different initial conditions (amplitude of applied torque, initial muscle length, initial voluntary activity, head position) in non-impaired (NI) volunteers and stroke patients (SP) with diagnosed upper limb spasticity and objectively evaluate their differences. A biomechanical device was designed to provide a 90 ms initially applied torque controlled stretch to the biceps brachii. The stretch reflex response was recorded using surface electromyography and angular displacement with a potentiometer. Stretch reflex characterisation was done on EMG data collected 150 ms before and to complete 450 ms after the perturbation. The outcome measures were the amplitude of the rectified reflex response and, the latency, rise time and duration reflex response. Lower amplitudes, shorter latencies and longer durations were observed in the poststroke populancn when compared to the non-impaired volunteers. Amplitude results were unexpected. However latencies and durations suggest increased stretch reflex excitability. Significant differences dependent on the initial conditions were found within the non-impaired volunteers. No differences were found in the post-stroke population. These latter results suggest lack of modulation of the stretch reflex excitability after stroke. More research is necessary to understand the relationship between the changes in the stretch reflex excitability and the clinical concept of spasticity and the importance of their quantification to improve the quality of life of people with neurological lesions.

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Lederman, Eyal. "The effect of manual therapy techniques on the neuromuscular system". Thesis, King's College London (University of London), 1999. https://kclpure.kcl.ac.uk/portal/en/theses/the-effect-of-manual-therapy-techniques-on-the-neuromuscular-system(3764f2dc-c18b-4f37-a1aa-0bcc0abe64ec).html.

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Libri sul tema "Stretch reflex"

Avela, Janne. Stretch-reflex adaptation in man. Jyväskylä: University of Jyväskylä, 1998.

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Gellman, Richard Evan. Muscle strain injury: An in vitro study of stretch rate dependence in elongation to failure. [New Haven: s.n.], 1991.

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1952-, Alter Michael J., a cura di. Science of flexibility. 2^a ed. Champaign, IL: Human Kinetics, 1996.

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Csonka, Jacqueline V. Electrical stimulation of tibialis anterior to inhibit the stretch reflex of soleus resulting from passive stretch and gait, and its effect on spasticity. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1992.

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Homma, S. Understanding the Stretch Reflex. Elsevier Science & Technology Books, 2011.

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Moldave, Kivie. Progress in Nucleic Acid Research and Molecular Biology, Volume 58 (Progress in Nucleic Acid Research and Molecular Biology). Academic Press, 1998.

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Alter, Michael J. Science of Flexibility. 3^a ed. Human Kinetics Publishers, 2004.

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Alter, Michael J. Science of Flexibility. 2^a ed. Human Kinetics Pub, 2000.

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Fisch, Adam. Spinal Canal and Muscle–Nerve Physiology. Oxford University Press, 2013. http://dx.doi.org/10.1093/med/9780199845712.003.0137.

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Mason, Peggy. Reflexes and Gait. Oxford University Press, 2017. http://dx.doi.org/10.1093/med/9780190237493.003.0022.

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The importance of proprioception to motor function is revealed by the dramatic story of Ian Waterman, a man who lost function in all proprioceptive and tactile spinal afferents. The circuitry of the stretch reflex, termed the deep tendon reflex in clinical circles, is described in detail. In this context, the student is introduced to load, muscle spindles, Ia afferents, α‎- and γ‎- motoneurons, and α‎- γ‎ coactivation. The concept of physiological extensors and flexors is useful for understanding the role of reflexes in normal and abnormal postures. The logic and utility of reflex testing is fully explained and the Ib and nociceptive withdrawal reflexes briefly introduced. Primitive reflexes and their modulation across development and in response to stroke or disease are presented. In a final segment, movements produced by central pattern generators and refined by reflexes are illustrated by a close examination of human gait across the life cycle.

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Capitoli di libri sul tema "Stretch reflex"

Baev, Konstantin V. "The Stretch-Reflex System". In Biological Neural Networks: Hierarchical Concept of Brain Function, 143–47. Boston, MA: Birkhäuser Boston, 1998. http://dx.doi.org/10.1007/978-1-4612-4100-3_10.

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Matthews, P. B. C. "Vibration and the Stretch Reflex". In Novartis Foundation Symposia, 40–55. Chichester, UK: John Wiley & Sons, Ltd., 2008. http://dx.doi.org/10.1002/9780470719565.ch4.

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Rotondo, Salvatore, Rodina Sadek, Narmin Mekawy, Monir Arnos e Abdeslem El Idrissi. "Taurine Enhances Stretch Reflex Excitability". In Advances in Experimental Medicine and Biology, 359–65. Singapore: Springer Singapore, 2019. http://dx.doi.org/10.1007/978-981-13-8023-5_34.

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Andersen, J. B., e T. Sinkjær. "Stretch Reflex Variations During Gait". In Neuroprosthetics: from Basic Research to Clinical Applications, 45–50. Berlin, Heidelberg: Springer Berlin Heidelberg, 1996. http://dx.doi.org/10.1007/978-3-642-80211-9_7.

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Mrachacz-Kersting, Natalie, Priscila de Brito Silva, Yukiko Makihara, Lars Arendt-Nielsen, Thomas Sinkjær e Uwe G. Kersting. "Stretch Reflex Conditioning in Humans – Implications for Function". In Biosystems & Biorobotics, 103–11. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-08072-7_20.

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Mrachacz-Kersting, Natalie, e Uwe G. Kersting. "Operant Conditioning of the Human Soleus Short Latency Stretch Reflex and Implications for the Medium Latency Soleus Stretch Reflex". In Converging Clinical and Engineering Research on Neurorehabilitation II, 59–63. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-46669-9_11.

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Westwick, David T. "Block Structured Modelling in the Study of the Stretch Reflex". In Lecture Notes in Control and Information Sciences, 385–402. London: Springer London, 2010. http://dx.doi.org/10.1007/978-1-84996-513-2_23.

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Graham, Bruce P., e Stephen J. Redman. "Simulation of the Muscle Stretch Reflex by a Neuronal Network". In Computation and Neural Systems, 323–30. Boston, MA: Springer US, 1993. http://dx.doi.org/10.1007/978-1-4615-3254-5_49.

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Rosendo, Andre, Xiangxiao Liu, Shogo Nakatsu, Masahiro Shimizu e Koh Hosoda. "A Combined CPG-Stretch Reflex Study on a Musculoskeletal Pneumatic Quadruped". In Biomimetic and Biohybrid Systems, 417–19. Cham: Springer International Publishing, 2014. http://dx.doi.org/10.1007/978-3-319-09435-9_48.

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Ebner, Timothy J., James R. Bloedel, Jerrold Vitek e Andrew Schwartz. "Modification of the Stretch Reflex in Spastic Monkeys by Cerebellar Stimulation". In Cerebellar Stimulation for Spasticity and Seizures, 89–104. Boca Raton: CRC Press, 2021. http://dx.doi.org/10.1201/9780429284939-9.

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Atti di convegni sul tema "Stretch reflex"

Liu, Xiangxiao, Andre Rosendo, Masahiro Shimizu e Koh Hosoda. "Improving hopping stability of a biped by muscular stretch reflex". In 2014 IEEE-RAS 14th International Conference on Humanoid Robots (Humanoids 2014). IEEE, 2014. http://dx.doi.org/10.1109/humanoids.2014.7041433.

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Rosendo, Andre, Shogo Nakatsu, Xiangxiao Liu, Masahiro Shimizu e Koh Hosoda. "Quadrupedal locomotion based on a muscular activation pattern with stretch-reflex". In 2014 IEEE International Conference on Robotics and Biomimetics (ROBIO). IEEE, 2014. http://dx.doi.org/10.1109/robio.2014.7090425.

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Ramos, C. F., S. S. Hacisalihzade, P. D. Ayme e L. W. Stark. "Exploring the 'behavior space' of a nonlinear model for the stretch reflex". In Proceedings of the Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 1988. http://dx.doi.org/10.1109/iembs.1988.94960.

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Flanagan, P. M., J. G. Chutkow, M. T. Riggs e V. D. Cristiano. "An Intelligent Computerized Stretch Reflex Measurement System For Clinical And Investigative Neurology". In Applications of Artificial Intelligence V, a cura di John F. Gilmore. SPIE, 1987. http://dx.doi.org/10.1117/12.940653.

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Al Dhaifallah, M., e D. T. Westwick. "Nonlinear modeling and identification of stretch reflex dynamics using support vector machines". In 2009 Annual International Conference of the IEEE Engineering in Medicine and Biology Society. IEEE, 2009. http://dx.doi.org/10.1109/iembs.2009.5333808.

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Shimizu, Masahiro, Keiko Suzuki, Kenichi Narioka e Koh Hosoda. "Roll motion control by stretch reflex in a continuously jumping musculoskeletal biped robot". In 2012 IEEE/RSJ International Conference on Intelligent Robots and Systems (IROS 2012). IEEE, 2012. http://dx.doi.org/10.1109/iros.2012.6386231.

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Cronin, Neil, Thomas Sinkjaer, Michael Voigt, Masaki Ishikawa, Janne Avela, Paavo Komi e Caroline Nicol. "Modulation of soleus fascicle stretch responses with changes in reflex-induced muscle contraction state". In 2008 Annual IEEE Student Paper Conference. IEEE, 2008. http://dx.doi.org/10.1109/aispc.2008.4460548.

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Ferreira, Joao, Vitor Moreira, Jose Machado e Filomena Soares. "Biomedical device for spasticity quantification based on the velocity dependence of the Stretch Reflex threshold". In Factory Automation (ETFA 2011). IEEE, 2011. http://dx.doi.org/10.1109/etfa.2011.6059225.

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Yu, Yong, Hisashi Iwashita, Kazumi Kawahira e Ryota Hayashi. "Development of rehabilitation device for hemiplegic fingers by finger-expansion facilitation exercise with stretch reflex". In 2013 IEEE International Conference on Robotics and Biomimetics (ROBIO). IEEE, 2013. http://dx.doi.org/10.1109/robio.2013.6739647.

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Averta, Giuseppe, Massimiliano Abbinante, Piero Orsini, Federica Felici, Paolo Lippi, Antonio Bicchi, Manuel G. Catalano e Matteo Bianchi. "A novel mechatronic system for evaluating elbow muscular spasticity relying on Tonic Stretch Reflex Threshold estimation". In 2020 42nd Annual International Conference of the IEEE Engineering in Medicine and Biology Society (EMBC) in conjunction with the 43rd Annual Conference of the Canadian Medical and Biological Engineering Society. IEEE, 2020. http://dx.doi.org/10.1109/embc44109.2020.9176011.

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Rapporti di organizzazioni sul tema "Stretch reflex"

Sanders, Suzanne, e Jessica Kirschbaum. Forest health monitoring at Mississippi National River and Recreation Area: 2022 field season. National Park Service, 2023. http://dx.doi.org/10.36967/2301407.

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The Mississippi National River and Recreation area (MISS), situated along a 116 km stretch of the Mississippi River through the Minneapolis and St. Paul urban corridor, encompasses ~21,800 ha of public and private land. In 2022, the Great Lakes Inventory and Monitoring Network (GLKN) resampled permanent forest monitoring sites in the park, marking the second assessment of these sites, which were established and initially sampled in 2011. The goal of this long-term monitoring project is to provides managers with routine updates on which to base management decisions; these data can also be used to tease apart impacts and elucidate causal agents when novel problems or situations arise. We initiated a comprehensive forest monitoring program at MISS in 2011, establishing 33 sites at that time. High water levels during our sampling window that year precluded sampling on many of our planned sites while on others, water levels had only recently subsided. Here, the full complement of herbs had not yet emerged. In 2022, we resampled existing sites and established additional locations, bringing the total to 50. Sampled and derived metrics included trees (density and basal area of live trees, seedlings, and snags (i.e., standing dead trees)), understory (herb and shrub frequency), browse (bite marks on woody species and presence and height of herbaceous species), and taxa richness. We classified sites into four broad forest types using the newer (2022) dataset, resulting in two upland types (upland rich, upland disturbed) and two floodplain types (box elder-dominated and silver maple-dominated). Because of sampling difficulties in 2011, we are only comparing tree, sapling, and snag data between years. At upland rich sites, overall tree (? 2.5 cm diameter at breast height [DBH]) density declined 22%, while that for just the small sapling component (? 2.5 cm, < 5 cm DBH) fell 41%. Species experiencing notable losses include basswood (Tilia americana L.), elm (Ulmus L.), bitternut hickory (Carya cordiformis (Wangenh.) K. Koch), and red oak (Quercus rubra L.). All three resampled sites are located in Spring Lake Park Reserve and subjected to high white-tailed deer (Odocoileus virginianus Zimm.) browse pressure. We sampled seven sites in upland disturbed forests, where overall tree density fell 17% from 778 ? 215 trees/ha to 648 ? 72 trees/ha, largely due to declines in elm, ash (Fraxinus sp. L.), and hackberry (Celtis occidentalis L.). While changes in black cherry (Prunus serotina Ehrh.) mirrored this pattern in diameter classes above 5 cm, density of saplings increased 12-fold, largely due to a swamping effect from one site, possibly in response to buckthorn (Rhamnus cathartica L.) removal. In the nine box elder-dominated sites, overall tree density declined from 635 ? 47 in 2011 to 500 ? 58 trees/ha in 2022, mainly reflecting changes in box elder (Acer negundo L.), elm, and silver maple (Acer saccharinum L.). In these sites, density of large (? 30 cm DBH) snags increased from 2.5 ? 1.6 to 11.1 ? 4.4 snags/ha. In silver maple-dominated floodplain forests, tree density in the 12 sites fell from 421 ? 63 to 291 ? 23 trees/ha, with declines observed in all five dominant species. Sapling density was low in these sites, falling from 62.6 ? 36 in 2011 to 23.6 ? 11 saplings/ha in 2022. Our observations likely reflect both deer browse and alteration of the flow regime by river impoundment. At upland sites, deer browse is impeding regeneration of all major upland species: red oak, bitternut hickory, basswood, and elm. While browse is also occurring in floodplain sites, prolonged inundation may play a larger role in regeneration failure here. Saplings of silver maple, box elder, cottonwood, elm, and hackberry all have some degree of susceptibility to inundation, ranging from moderate tolerance to completely intolerant. The Mississippi River experienced flooding in 2014, 2017, and again in 2019 when flood stage was exceeded for a record number of days in St. Paul. Sapling decline at floodplain sites is likely a direct result of this. Forest management within the park should focus both on invasive species control and floodplain reforestation. Several sites with heavy invasive weed species are in areas where leveraging local volunteers for removal projects may be possible. Floodplain reforestation requires a dual approach of research and active management. Research is needed to determine preferred propagule types and planting stock, as well as the most effective ways to control invasives, especially reed canarygrass (Phalaris arundinacea L.). Active floodplain reforestation can alleviate many of the issues we found here, although this is expensive, limited in scope, and carries with it a great deal of uncertainty. Nonetheless, projects undertaken at a small scale can provide lessons to managers, based on which aspects were successful and which were not. Many of the park forests at MISS are nearing an inflection point and are at risk of becoming irreversibly altered if countermeasures are not undertaken in the near future. At this point, steps taken to promote ecosystem integrity are likely to be less costly and more effective than those which may be needed after further ecosystem decline. The river system through the Twin Cities metro area provides numerous services, both ecological and otherwise. As the need to act is becoming a pressing issue, it is incumbent on land managers to recognize this, and address it.

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