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Anthony J Blazevich - One of the best experts on this subject based on the ideXlab platform.
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lack of cortical or ia afferent spinal pathway involvement in Muscle force loss after passive static Stretching
Journal of Neurophysiology, 2020Co-Authors: Gabriel S Trajano, Timothy S Pulverenti, Benjamin J C Kirk, Andrew Walsh, Anthony J BlazevichAbstract:This study is the first to specifically examine potential sites underlying the decreases in neural activation of Muscle and force production after a bout of Muscle Stretching. However, no changes w...
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passive Muscle Stretching impairs rapid force production and neuromuscular function in human plantar flexors
European Journal of Applied Physiology, 2019Co-Authors: Gabriel S Trajano, Laurent B Seitz, Kazunori Nosaka, Anthony J BlazevichAbstract:Purpose: We examined the effect of Muscle Stretching on the ability to produce rapid torque and the mechanisms underpinning the changes. Methods: Eighteen men performed three conditions: (1) continuous stretch (1 set of 5 min), (2) intermittent stretch (5 sets of 1 min with 15-s inter-stretch interval), and (3) control. Isometric plantar flexor rate of torque development was measured during explosive maximal voluntary contractions (MVC) in the intervals 0–100 ms (RTDV100) and 0–200 ms (RTDV200), and in electrically evoked 0.5-s tetanic contractions (20 Hz, 20 Hz preceded by a doublet and 80 Hz). The rate of EMG rise, electromechanical delay during MVC (EMDV) and during a single twitch contraction (EMDtwitch) were assessed. Results: RTDV200 was decreased (P < 0.05) immediately after continuous (− 15%) and intermittent stretch (− 30%) with no differences between protocols. The rate of torque development during tetanic stimulations was reduced (P < 0.05) immediately after continuous (− 8%) and intermittent stretch (− 10%), when averaged across stimulation frequencies. Lateral gastrocnemius rate of EMG rise was reduced after intermittent stretch (− 27%), and changes in triceps surae rate of EMG rise were correlated with changes in RTDV200 after both continuous (r = 0.64) and intermittent stretch (r = 0.65). EMDV increased immediately (31%) and 15 min (17%) after intermittent stretch and was correlated with changes in RTDV200 (r = − 0.56). EMDtwitch increased immediately after continuous (4%), and immediately (5.4%), 15 min (6.3%), and 30 min after (6.4%) intermittent stretch (P < 0.05). Conclusions: Reductions in the rate of torque development immediately after Stretching were associated with both neural and mechanical mechanisms.
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the loss of Muscle force production after Muscle Stretching is not accompanied by altered corticospinal excitability
European Journal of Applied Physiology, 2019Co-Authors: Timothy S Pulverenti, Gabriel S Trajano, Benjamin J C Kirk, Anthony J BlazevichAbstract:The aim of the present study was to determine whether depression of maximal muscular force and neural drive subsequent to prolonged ( ≥ 60 s) passive Muscle Stretching is associated with altered corticospinal excitability or intracortical (GABAB-mediated) inhibition. Fourteen healthy adult males were tested before and after 5 min (5 × 60-s stretches) of intense, passive static Stretching of the plantar flexor Muscles. Two protocols (A and B) were conducted in a randomized order. Transcranial magnetic stimulation was delivered to the contralateral motor cortex at rest (Protocol A) and during maximal voluntary contractions (Protocol B). Changes in maximal voluntary isometric torque, voluntary surface electromyographic activity of triceps surae Muscles (normalized to M-wave; EMG/M), motor-evoked potentials (MEP), and cortical silent period (cSP; Protocol B) in soleus elicited by transcranial magnetic stimulation were examined 10 min after stretch. In both protocols A and B, significant decreases were observed immediately after Stretching in maximal voluntary plantar flexion torque ( − 20.1 ± 15.9%, P = 0.004; and − 17.2 ± 13.5%, P = 0.006) and EMG/M ( − 18.0 ± 18.2%, P = 0.023; and − 13.0 ± 9.3%, P = 0.003). Decreases in torque and EMG/M were highly correlated (r = 0.67–0.85, P < 0.05). However, no changes were observed in MEP amplitudes during rest ( + 29.3 ± 50.0%) or maximum voluntary contraction ( + 1.9 ± 16.8%), or in cSP ( + 2.1 ± 15.1%). Impaired neural drive contributed to the stretch-induced force loss; however, changes in corticospinal excitability and intracortical inhibition could not explain the phenomenon.
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acute effects of Muscle Stretching on physical performance range of motion and injury incidence in healthy active individuals a systematic review
Applied Physiology Nutrition and Metabolism, 2016Co-Authors: David G Behm, Anthony J Blazevich, Anthony D Kay, Malachy P MchughAbstract:Recently, there has been a shift from static Stretching (SS) or proprioceptive neuromuscular facilitation (PNF) Stretching within a warm-up to a greater emphasis on dynamic Stretching (DS). The objective of this review was to compare the effects of SS, DS, and PNF on performance, range of motion (ROM), and injury prevention. The data indicated that SS- (-3.7%), DS- (+1.3%), and PNF- (-4.4%) induced performance changes were small to moderate with testing performed immediately after Stretching, possibly because of reduced Muscle activation after SS and PNF. A dose-response relationship illustrated greater performance deficits with ≥60 s (-4.6%) than with <60 s (-1.1%) SS per Muscle group. Conversely, SS demonstrated a moderate (2.2%) performance benefit at longer Muscle lengths. Testing was performed on average 3-5 min after Stretching, and most studies did not include postStretching dynamic activities; when these activities were included, no clear performance effect was observed. DS produced small-to-moderate performance improvements when completed within minutes of physical activity. SS and PNF Stretching had no clear effect on all-cause or overuse injuries; no data are available for DS. All forms of training induced ROM improvements, typically lasting <30 min. Changes may result from acute reductions in Muscle and tendon stiffness or from neural adaptations causing an improved stretch tolerance. Considering the small-to-moderate changes immediately after Stretching and the study limitations, Stretching within a warm-up that includes additional postStretching dynamic activity is recommended for reducing Muscle injuries and increasing joint ROM with inconsequential effects on subsequent athletic performance.
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can passive stretch inhibit motoneuron facilitation in the human plantar flexors
Journal of Applied Physiology, 2014Co-Authors: Gabriel S Trajano, Laurent B Seitz, Kazunori Nosaka, Anthony J BlazevichAbstract:The purpose of the present study was to examine the possible inhibitory effect of passive plantar flexor Muscle Stretching on the motoneuron facilitatory system. Achilles tendon vibration (70 Hz) a...
Walter Herzog - One of the best experts on this subject based on the ideXlab platform.
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increased force following Muscle Stretching and simultaneous fibre shortening residual force enhancement or force depression that is the question
Journal of Biomechanics, 2021Co-Authors: Sheharzad Mahmood, Walter Herzog, Andrew SawatskyAbstract:Abstract Residual force enhancement (rFE) describes the increase in isometric force following Muscle Stretching compared to the corresponding isometric force. Even though rFE is consistently observed in isolated Muscle preparations, it is not always observed in human skeletal Muscle. This inconsistency might be associated with disociations between length changes in Muscle tendon units (MTUs) and fibres. This prompted the question if there is rFE for conditions where the MTU is stretched while fibres shorten. Rabbit tibialis anterior (TA) MTUs (n = 4) were stretched and the isometric forces following Stretching were compared to corresponding forces from isometric reference contractions. Unique combinations of stretch speed and activation were used to create conditions of continuous fibre shortening during MTU stretch. Mean force was increased (18 ± 2%) following MTU Stretching compared to the isometric reference forces. Without fibre length measurements, this result would be referred to as rFE. However, fibre shortening in the reference contractions was always greater than for the eccentric stretch contractions, suggesting that the observed increase in force might be caused by less residual force depression (rFD) in the stretch tests compared to the reference contractions. However, the work performed by fibre shortening was similar between the reference and the MTU stretch contractions, suggesting that rFD was similar for both experimental conditions. Therefore, we conclude that we observed rFE in the absence of contractile element Stretching. However, a lack of knowledge of the molecular mechanisms that distinguish rFE from rFD prevents an unequivocal pronouncement of what caused the enhanced forces after active Muscle Stretching.
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on sarcomere length stability during isometric contractions before and after active Stretching
The Journal of Experimental Biology, 2019Co-Authors: Kaleena Johnston, Azim Jinha, Eng Kuan Moo, Walter HerzogAbstract:Sarcomere length (SL) instability and SL non-uniformity have been used to explain fundamental properties of skeletal Muscles, such as creep, force depression following active Muscle shortening and residual force enhancement following active Stretching of Muscles. Regarding residual force enhancement, it has been argued that active Muscle Stretching causes SL instability, thereby increasing SL non-uniformity. However, we recently showed that SL non-uniformity is not increased by active Muscle Stretching, but it remains unclear if SL stability is affected by active Stretching. Here, we used single myofibrils of rabbit psoas Muscle and measured SL non-uniformity and SL instability during isometric contractions and for isometric contractions following active Stretching at average SLs corresponding to the descending limb of the force-length relationship. We defined isometric contractions as contractions during which mean SL remained constant. SL instability was quantified by the rate of change of individual SLs over the course of steady-state isometric force and SL non-uniformity was defined as deviations of SLs from the mean SL at an instant of time. We found that whereas the mean SL remained constant during isometric contraction, by definition, individual SLs did not. SLs were more stable in the force-enhanced, isometric state following active Stretching compared with the isometric reference state. We also found that SL instability was not correlated with the rate of change of SL non-uniformity. Also, SL non-uniformity was not different in the isometric and the post-stretch isometric contractions. We conclude that since SL is more stable but similarly non-uniform in the force-enhanced compared with the corresponding isometric reference contraction, it appears unlikely that either SL instability or SL non-uniformity contribute to the residual force enhancement property of skeletal Muscle.
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does Stretching velocity affect residual force enhancement
Journal of Biomechanics, 2019Co-Authors: Atsuki Fukutani, T R Leonard, Walter HerzogAbstract:Abstract It is thought that the magnitude of residual force enhancement (RFE) is not affected by stretch velocity. However, the range of stretch velocities studied in previous investigations has been limited to slow and moderate velocities. High velocities of Muscle Stretching are associated with a loss of force and incomplete cross-bridge attachment to actin, thus creating a unique set of eccentric conditions referred to as slippage. The purpose of this study was to extend the relationship between stretch velocity and RFE to high velocities. We hypothesized that slippage at high velocities might affect RFE. We stretched cat soleus Muscles for 4 mm to the plateau of the force-length relationship at speeds of 2, 4, 8, 16, 32, 64 mm/s to induce RFE, and slippage for the fastest condition. For each RFE test, a corresponding isometric reference test was conducted. Residual force enhancement was quantified as the relative increase in isometric steady state force between the experimental stretch and the isometric reference tests. Residual force enhancement was similar for all stretch speeds, as expected, with the exception of the fastest speed (64 mm/s), which was associated with slippage and no significant RFE. These results suggest that if stretch speeds are too fast, and are associated with slippage, RFE is abolished. We conclude from these findings that proper cross-bridge engagement is required during eccentric Muscle action to produce RFE.
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changes in fascicle lengths and pennation angles do not contribute to residual force enhancement depression in voluntary contractions
Journal of Applied Biomechanics, 2011Co-Authors: Markus Tilp, Simon Steib, Gudrun Schappachertilp, Walter HerzogAbstract:Force enhancement following Muscle Stretching and force depression following Muscle shortening are well-accepted properties of skeletal Muscle contraction. However, the factors contributing to force enhancement/depression remain a matter of debate. In addition to factors on the fiber or sarcomere level, fiber length and angle of pennation affect the force during voluntary isometric contractions in whole Muscles. Therefore, we hypothesized that differences in fiber lengths and angles of pennation between force-enhanced/depressed and reference states may contribute to force enhancement/depression during voluntary contractions. The purpose of this study was to test this hypothesis. Twelve subjects participated in this study, and force enhancement/depression was measured in human tibialis anterior. Fiber lengths and angles of pennation were quantified using ultrasound imaging. Neither fiber lengths nor angles of pennation were found to differ between the isometric reference contractions and any of the force-e...
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residual force enhancement in skeletal Muscle
The Journal of Physiology, 2006Co-Authors: Walter Herzog, Eunjeong Lee, Dilson E RassierAbstract:Residual force enhancement has been observed consistently in skeletal Muscles following active Stretching. However, its underlying mechanism(s) remain elusive, and it cannot be explained readily within the framework of the cross-bridge theory. Traditionally, residual force enhancement has been attributed to the development of sarcomere length non-uniformities. However, recent evidence suggests that this might not be the case. Rather, it appears that residual force enhancement has an active and a passive component. The active component is tentatively associated with changes in the cross-bridge kinetics that might be reflected in decreased detachment rates following active Muscle Stretching, while the passive component possibly originates from a structural protein, such as titin, whose stiffness might be regulated by calcium.
Gabriel S Trajano - One of the best experts on this subject based on the ideXlab platform.
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lack of cortical or ia afferent spinal pathway involvement in Muscle force loss after passive static Stretching
Journal of Neurophysiology, 2020Co-Authors: Gabriel S Trajano, Timothy S Pulverenti, Benjamin J C Kirk, Andrew Walsh, Anthony J BlazevichAbstract:This study is the first to specifically examine potential sites underlying the decreases in neural activation of Muscle and force production after a bout of Muscle Stretching. However, no changes w...
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passive Muscle Stretching impairs rapid force production and neuromuscular function in human plantar flexors
European Journal of Applied Physiology, 2019Co-Authors: Gabriel S Trajano, Laurent B Seitz, Kazunori Nosaka, Anthony J BlazevichAbstract:Purpose: We examined the effect of Muscle Stretching on the ability to produce rapid torque and the mechanisms underpinning the changes. Methods: Eighteen men performed three conditions: (1) continuous stretch (1 set of 5 min), (2) intermittent stretch (5 sets of 1 min with 15-s inter-stretch interval), and (3) control. Isometric plantar flexor rate of torque development was measured during explosive maximal voluntary contractions (MVC) in the intervals 0–100 ms (RTDV100) and 0–200 ms (RTDV200), and in electrically evoked 0.5-s tetanic contractions (20 Hz, 20 Hz preceded by a doublet and 80 Hz). The rate of EMG rise, electromechanical delay during MVC (EMDV) and during a single twitch contraction (EMDtwitch) were assessed. Results: RTDV200 was decreased (P < 0.05) immediately after continuous (− 15%) and intermittent stretch (− 30%) with no differences between protocols. The rate of torque development during tetanic stimulations was reduced (P < 0.05) immediately after continuous (− 8%) and intermittent stretch (− 10%), when averaged across stimulation frequencies. Lateral gastrocnemius rate of EMG rise was reduced after intermittent stretch (− 27%), and changes in triceps surae rate of EMG rise were correlated with changes in RTDV200 after both continuous (r = 0.64) and intermittent stretch (r = 0.65). EMDV increased immediately (31%) and 15 min (17%) after intermittent stretch and was correlated with changes in RTDV200 (r = − 0.56). EMDtwitch increased immediately after continuous (4%), and immediately (5.4%), 15 min (6.3%), and 30 min after (6.4%) intermittent stretch (P < 0.05). Conclusions: Reductions in the rate of torque development immediately after Stretching were associated with both neural and mechanical mechanisms.
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the loss of Muscle force production after Muscle Stretching is not accompanied by altered corticospinal excitability
European Journal of Applied Physiology, 2019Co-Authors: Timothy S Pulverenti, Gabriel S Trajano, Benjamin J C Kirk, Anthony J BlazevichAbstract:The aim of the present study was to determine whether depression of maximal muscular force and neural drive subsequent to prolonged ( ≥ 60 s) passive Muscle Stretching is associated with altered corticospinal excitability or intracortical (GABAB-mediated) inhibition. Fourteen healthy adult males were tested before and after 5 min (5 × 60-s stretches) of intense, passive static Stretching of the plantar flexor Muscles. Two protocols (A and B) were conducted in a randomized order. Transcranial magnetic stimulation was delivered to the contralateral motor cortex at rest (Protocol A) and during maximal voluntary contractions (Protocol B). Changes in maximal voluntary isometric torque, voluntary surface electromyographic activity of triceps surae Muscles (normalized to M-wave; EMG/M), motor-evoked potentials (MEP), and cortical silent period (cSP; Protocol B) in soleus elicited by transcranial magnetic stimulation were examined 10 min after stretch. In both protocols A and B, significant decreases were observed immediately after Stretching in maximal voluntary plantar flexion torque ( − 20.1 ± 15.9%, P = 0.004; and − 17.2 ± 13.5%, P = 0.006) and EMG/M ( − 18.0 ± 18.2%, P = 0.023; and − 13.0 ± 9.3%, P = 0.003). Decreases in torque and EMG/M were highly correlated (r = 0.67–0.85, P < 0.05). However, no changes were observed in MEP amplitudes during rest ( + 29.3 ± 50.0%) or maximum voluntary contraction ( + 1.9 ± 16.8%), or in cSP ( + 2.1 ± 15.1%). Impaired neural drive contributed to the stretch-induced force loss; however, changes in corticospinal excitability and intracortical inhibition could not explain the phenomenon.
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can passive stretch inhibit motoneuron facilitation in the human plantar flexors
Journal of Applied Physiology, 2014Co-Authors: Gabriel S Trajano, Laurent B Seitz, Kazunori Nosaka, Anthony J BlazevichAbstract:The purpose of the present study was to examine the possible inhibitory effect of passive plantar flexor Muscle Stretching on the motoneuron facilitatory system. Achilles tendon vibration (70 Hz) a...
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contribution of central vs peripheral factors to the force loss induced by passive stretch of the human plantar flexors
Faculty of Health, 2013Co-Authors: Gabriel S Trajano, Laurent B Seitz, Kasunori Nosaka, Anthony J BlazevichAbstract:Free to read The purpose of the present research was to identify the contribution of central vs. peripheral factors to the force loss after passive Muscle Stretching. Thirteen men randomly performed both a 5-min constant-torque stretch of the plantar flexors on an isokinetic dynamometer and a resting condition on 2 separate days. The triceps surae electromyogram (EMG) was recorded simultaneously with plantar flexor isometric torque. Measures of central drive, including the EMG amplitude normalized to the Muscle compound action potential amplitude (EMG/M), percent voluntary activation and first volitional wave amplitude, and measures of peripheral function, including the twitch peak torque, 20-to-80-Hz tetanic torque ratio and torque during 20-Hz stimulation preceded by a doublet, were taken before and immediately and 15 min after each condition. Peak torque (−15.7%), EMG/M (−8.2%), and both twitch (−9.4%) and 20-Hz peak torques (−11.5%) were reduced immediately after stretch but recovered by 15 min. There were strong correlations between the torque loss and the reductions in central drive parameters (r = 0.65–0.93). Torque recovery was also strongly correlated with the recovery in EMG/M and percent voluntary activation (r = 0.77–0.81). The moderate decreases in measures of peripheral function were not related to the torque loss or recovery. These results suggest that 1) central factors were strongly related to the torque reduction immediately after stretch and during torque recovery; and 2) the Muscle's contractile capacity was moderately reduced, although these changes were not associated with the torque reduction, and changes in excitation-contraction coupling efficiency were not observed.
Blazevich, Anthony J - One of the best experts on this subject based on the ideXlab platform.
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Plantar Flexor Muscle Stretching depresses the Soleus Late Response but not Tendon Tap Reflexes
'Wiley', 2021Co-Authors: Pulverenti, Timothy S, Trajano, Gabriel S, Kirk, Benjamin J C, Bochkezanian Vanesa, Blazevich, Anthony JAbstract:The purpose of this study was to investigate changes in Muscle spindle sensitivity with early and late soleus reflex responses via tendon taps and transcranial magnetic stimulation, respectively, after an acute bout of prolonged static plantar flexor Muscle Stretching. Seventeen healthy males were tested before and after 5 min (5 × 60-s stretches) of passive static Stretching of the plantar flexor Muscles. Maximal voluntary isometric torque and M wave-normalized triceps surae Muscle surface electromyographic activity were recorded. Both soleus tendon reflexes, evoked by percussion of the Achilles tendon during rest and transcranial magnetic stimulation-evoked soleus late responses during submaximal isometric dorsiflexion were also quantified. Significant decreases in maximal voluntary isometric plantar flexion torque (−19.2 ± 13.6%, p =.002) and soleus electromyographic activity (−20.1 ± 11.4%, p .05). Significant reductions in soleus late response amplitudes (−46.9 ± 36.0%, p =.002) were detected, although these changes were not correlated with changes in maximal electromyographic activity, torque or tendon reflex amplitudes. No changes in soleus late response latency were detected. In conclusion, impaired neural drive was implicated in the stretch-induced force loss; however, no evidence was found that this loss was related to changes in Muscle spindle sensitivity. We hypothesize that the decrease in soleus late response indicates a stretch-induced reduction in a polysynaptic postural reflex rather than spindle reflex sensitivity
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Plantar flexor Muscle Stretching depresses the soleus late response but not tendon tap reflexes
'Wiley', 2021Co-Authors: Pulverenti, Timothy S, Trajano, Gabriel S, Kirk, Benjamin J C, Bochkezanian Vanesa, Blazevich, Anthony JAbstract:The purpose of this study was to investigate changes in Muscle spindle sensitivity with early and late soleus reflex responses via tendon taps and transcranial magnetic stimulation, respectively, after an acute bout of prolonged static plantar flexor Muscle Stretching. Seventeen healthy males were tested before and after 5 min (5 × 60-s stretches) of passive static Stretching of the plantar flexor Muscles. Maximal voluntary isometric torque and M wave-normalized triceps surae Muscle surface electromyographic activity were recorded. Both soleus tendon reflexes, evoked by percussion of the Achilles tendon during rest and transcranial magnetic stimulation-evoked soleus late responses during submaximal isometric dorsiflexion were also quantified. Significant decreases in maximal voluntary isometric plantar flexion torque (−19.2 ± 13.6%, p =.002) and soleus electromyographic activity (−20.1 ± 11.4%, p \u3c .001) were observed immediately after Stretching, and these changes were highly correlated (r = 0.76, p \u3c .001). No changes were observed in tendon reflex amplitude or latency or peak Muscle twitch torque (p \u3e .05). Significant reductions in soleus late response amplitudes (−46.9 ± 36.0%, p =.002) were detected, although these changes were not correlated with changes in maximal electromyographic activity, torque or tendon reflex amplitudes. No changes in soleus late response latency were detected. In conclusion, impaired neural drive was implicated in the stretch-induced force loss; however, no evidence was found that this loss was related to changes in Muscle spindle sensitivity. We hypothesize that the decrease in soleus late response indicates a stretch-induced reduction in a polysynaptic postural reflex rather than spindle reflex sensitivity
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Static Stretching reduces motoneuron excitability: The potential role of neuromodulation
'Ovid Technologies (Wolters Kluwer Health)', 2021Co-Authors: Trajano, Gabriel S, Blazevich, Anthony JAbstract:Prolonged static Muscle Stretching transiently reduces maximal Muscle force, and this force loss has a strong neural component. In this review, we discuss the evidence suggesting that Stretching reduces the motoneuron\u27s ability to amplify excitatory drive. We propose a hypothetical model in which Stretching causes physiological relaxation, reducing the brainstem-derived neuromodulatory drive necessary to maximize motoneuron discharge rates
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Effects of acute and chronic Stretching on pain control
'Clinical Exercise Physiology Association', 2021Co-Authors: Behm, David G, Kay, Anthony David, Trajano Gabriel, Alizadeh Shahab, Blazevich, Anthony JAbstract:ABSTRACT While Muscle Stretching has been commonly used to alleviate pain, reports of its effectiveness are conflicting. The objective of this review is to investigate the acute and chronic effects of Stretching on pain, including delayed onset Muscle soreness. The few studies implementing acute Stretching protocols have reported small to large magnitude decreases in quadriceps and anterior knee pain as well as reductions in headache pain. Chronic Stretching programs have demonstrated more consistent reductions in pain from a wide variety of joints and Muscles, which has been ascribed to an increased sensory (pain) tolerance. Other mechanisms underlying acute and chronic pain reduction have been proposed to be related to gate control theory, diffuse noxious inhibitory control, myofascial meridians, and reflex-induced increases in parasympathetic nervous activity. By contrast, the acute effects of Stretching on delayed onset Muscle soreness are conflicting. Reports of stretch-induced reductions in delayed onset Muscle soreness may be attributed to increased pain tolerance or alterations in the Muscle's parallel elastic component or extracellular matrix properties providing protection against tissue damage. Further research evaluating the effect of various Stretching protocols on different pain modalities is needed to clarify conflicts within the literature
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Lack of cortical or Ia-afferent spinal pathway involvement in Muscle force loss after passive static Stretching
'American Physiological Society', 2020Co-Authors: Pulverenti, Timothy S, Trajano, Gabriel S, Walsh Andrew, Kirk, Benjamin J.c., Blazevich, Anthony JAbstract:This study investigated whether modulation of corticospinal-motoneuronal excitability and/or synaptic transmission of the Ia afferent spinal reflex contributes to decreases in voluntary activation and muscular force after an acute bout of prolonged static Muscle Stretching. Fifteen men performed five 60-s constant-torque stretches (15-s rest intervals; total duration 5 min) of the plantar flexors on an isokinetic dynamometer and a nonStretching control condition in random order on 2 separate days. Maximum isometric plantar flexor torque and triceps surae Muscle electromyographic activity (normalized to M wave; EMG/M) were simultaneously recorded immediately before and after each condition. Motor-evoked potentials (using transcranial magnetic stimulation) and H-reflexes were recorded from soleus during EMG-controlled submaximal contractions (23.4 ± 6.9% EMG maximum). No changes were detected in the control condition. After Stretching, however, peak torque (mean ± SD; =14.3 ± 7.0%) and soleus EMG/M (=17.8 ± 6.2%) decreased, and these changes were highly correlated (r = 0.83). No changes were observed after Stretching in soleus MEP or H-reflex amplitudes measured during submaximal contractions, and interindividual variability of changes was not correlated with changes in EMG activity or maximum torque. During EMG-controlled submaximal contractions, torque production was significantly decreased after Stretching (=22.7 ± 15.0%), indicating a compromised muscular output. These data provide support that changes in the excitability of the corticospinal-motoneuronal and Ia afferent spinal reflex pathways do not contribute to poststretch neural impairment. NEW & NOTEWORTHY This study is the first to specifically examine potential sites underlying the decreases in neural activation of Muscle and force production after a bout of Muscle Stretching. However, no changes were found in either the H-reflex or motor-evoked potential amplitude during submaximal contractions
Timothy S Pulverenti - One of the best experts on this subject based on the ideXlab platform.
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lack of cortical or ia afferent spinal pathway involvement in Muscle force loss after passive static Stretching
Journal of Neurophysiology, 2020Co-Authors: Gabriel S Trajano, Timothy S Pulverenti, Benjamin J C Kirk, Andrew Walsh, Anthony J BlazevichAbstract:This study is the first to specifically examine potential sites underlying the decreases in neural activation of Muscle and force production after a bout of Muscle Stretching. However, no changes w...
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the loss of Muscle force production after Muscle Stretching is not accompanied by altered corticospinal excitability
European Journal of Applied Physiology, 2019Co-Authors: Timothy S Pulverenti, Gabriel S Trajano, Benjamin J C Kirk, Anthony J BlazevichAbstract:The aim of the present study was to determine whether depression of maximal muscular force and neural drive subsequent to prolonged ( ≥ 60 s) passive Muscle Stretching is associated with altered corticospinal excitability or intracortical (GABAB-mediated) inhibition. Fourteen healthy adult males were tested before and after 5 min (5 × 60-s stretches) of intense, passive static Stretching of the plantar flexor Muscles. Two protocols (A and B) were conducted in a randomized order. Transcranial magnetic stimulation was delivered to the contralateral motor cortex at rest (Protocol A) and during maximal voluntary contractions (Protocol B). Changes in maximal voluntary isometric torque, voluntary surface electromyographic activity of triceps surae Muscles (normalized to M-wave; EMG/M), motor-evoked potentials (MEP), and cortical silent period (cSP; Protocol B) in soleus elicited by transcranial magnetic stimulation were examined 10 min after stretch. In both protocols A and B, significant decreases were observed immediately after Stretching in maximal voluntary plantar flexion torque ( − 20.1 ± 15.9%, P = 0.004; and − 17.2 ± 13.5%, P = 0.006) and EMG/M ( − 18.0 ± 18.2%, P = 0.023; and − 13.0 ± 9.3%, P = 0.003). Decreases in torque and EMG/M were highly correlated (r = 0.67–0.85, P < 0.05). However, no changes were observed in MEP amplitudes during rest ( + 29.3 ± 50.0%) or maximum voluntary contraction ( + 1.9 ± 16.8%), or in cSP ( + 2.1 ± 15.1%). Impaired neural drive contributed to the stretch-induced force loss; however, changes in corticospinal excitability and intracortical inhibition could not explain the phenomenon.
