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Kerris, Jarrod P., Andrew C. Betik, Jinhua Li, and Glenn K. McConell. "Passive stretch regulates skeletal muscle glucose uptake independent of nitric oxide synthase." Journal of Applied Physiology 126, no. 1 (January 1, 2019): 239–45. http://dx.doi.org/10.1152/japplphysiol.00368.2018.
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Skeletal muscle contraction increases glucose uptake via an insulin-independent mechanism. Signaling pathways arising from mechanical strain are activated during muscle contractions, and mechanical strain in the form of passive stretching stimulates glucose uptake. However, the exact mechanisms regulating stretch-stimulated glucose uptake are not known. Since nitric oxide synthase (NOS) has been implicated in the regulation of glucose uptake during ex vivo and in situ muscle contractions and during exercise, and NO is increased with stretch, we examined whether the increase in muscle glucose uptake during stretching involves NOS. We passively stretched isolated extensor digitorum longus muscles (15 min at ~100–130 mN) from control mice and mice lacking either neuronal NOSµ (nNOSµ) or endothelial NOS (eNOS) isoforms, as well as used pharmacological inhibitors of NOS. Stretch significantly increased muscle glucose uptake appoximately twofold ( P < 0.05), and this was unaffected by the presence of the NOS inhibitors NG-monomethyl-l-arginine (100 µM) or NG-nitro-l-arginine methyl ester (100 µM). Similarly, stretch-stimulated glucose uptake was not attenuated by deletion of either eNOS or nNOSµ isoforms. Furthermore, stretching failed to increase skeletal muscle NOS enzymatic activity above resting levels. These data clearly demonstrate that stretch-stimulated skeletal muscle glucose uptake is not dependent on NOS. NEW & NOTEWORTHY Passive stretching is known to activate muscle glucose uptake through mechanisms that partially overlap with contraction. We report that genetic knockout of endothelial nitric oxide synthase (NOS) or neuronal NOS or pharmacological NOS inhibition does not affect stretch-stimulated glucose uptake. Passive stretch failed to increase NOS activity above resting levels. This information is important for the study of signaling pathways that regulate stretch-stimulated glucose uptake and indicate that NOS should be excluded as a potential signaling factor in this regard.
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Apostolopoulos, Nikos C., Ian M. Lahart, Michael J. Plyley, Jack Taunton, Alan M. Nevill, Yiannis Koutedakis, Matthew Wyon, and George S. Metsios. "The effects of different passive static stretching intensities on recovery from unaccustomed eccentric exercise – a randomized controlled trial." Applied Physiology, Nutrition, and Metabolism 43, no. 8 (August 2018): 806–15. http://dx.doi.org/10.1139/apnm-2017-0841.
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Effects of passive static stretching intensity on recovery from unaccustomed eccentric exercise of right knee extensors was investigated in 30 recreationally active males randomly allocated into 3 groups: high-intensity (70%–80% maximum perceived stretch), low-intensity (30%–40% maximum perceived stretch), and control. Both stretching groups performed 3 sets of passive static stretching exercises of 60 s each for hamstrings, hip flexors, and quadriceps, over 3 consecutive days, post-unaccustomed eccentric exercise. Muscle function (eccentric and isometric peak torque) and blood biomarkers (creatine kinase and C-reactive protein) were measured before (baseline) and after (24, 48, and 72 h) unaccustomed eccentric exercise. Perceived muscle soreness scores were collected immediately (time 0), and after 24, 48, and 72 h postexercise. Statistical time × condition interactions observed only for eccentric peak torque (p = 0.008). Magnitude-based inference analyses revealed low-intensity stretching had most likely, very likely, or likely beneficial effects on perceived muscle soreness (48–72 h and 0–72 h) and eccentric peak torque (baseline–24 h and baseline–72 h), compared with high-intensity stretching. Compared with control, low-intensity stretching had very likely or likely beneficial effects on perceived muscle soreness (0–24 h and 0–72 h), eccentric peak torque (baseline–48 h and baseline–72 h), and isometric peak torque (baseline–72 h). High-intensity stretching had likely beneficial effects on eccentric peak torque (baseline–48 h), but likely had harmful effects on eccentric peak torque (baseline–24 h) and creatine kinase (baseline–48 h and baseline–72 h), compared with control. Therefore, low-intensity stretching is likely to result in small-to-moderate beneficial effects on perceived muscle soreness and recovery of muscle function post-unaccustomed eccentric exercise, but not markers of muscle damage and inflammation, compared with high-intensity or no stretching.
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Blazevich, Anthony J. "Adaptations in the passive mechanical properties of skeletal muscle to altered patterns of use." Journal of Applied Physiology 126, no. 5 (May 1, 2019): 1483–91. http://dx.doi.org/10.1152/japplphysiol.00700.2018.
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The aim of this mini-review is to describe the present state of knowledge regarding the effects of chronic changes in the patterns of muscle use (defined as changes lasting >1 wk), including muscle stretching, strengthening, and others, on the passive mechanical properties of healthy human skeletal muscles. Various forms of muscle stretch training and some forms of strength training (especially eccentric training) are known to strongly impact the maximum elongation capacity of muscles in vivo (i.e., maximum joint range of motion), largely by increasing our ability to tolerate higher stretch loads. However, only small effects are observed in the passive stiffness of the muscle-tendon unit (MTU) or the muscle itself, although a reduction in muscle stiffness has been observed in the plantar flexors after both stretching and eccentric exercise interventions. No changes have yet been observed in viscoelastic properties such as the MTU stress-relaxation response, although a minimum of evidence indicates that hysteresis during passive stretch-relaxation cycles may be reduced by muscle stretching training. Importantly, data exist for relatively few muscle groups, and little is known about the effects of age and sex on the adaptive process of passive mechanical properties. Despite the significant research effort afforded to understanding the effects of altered physical activity patterns on the maximum range of motion at some joints, further information is needed before it will be possible to develop targeted physical activity interventions with the aim of evoking specific changes in passive mechanical properties in individuals or in specific muscles and muscle groups.
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Estrada, Juan A., Guillaume P. Ducrocq, and Marc P. Kaufman. "The magnitude of the exercise pressor reflex is influenced by the active skeletal muscle mass in the decerebrate rat." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 318, no. 1 (January 1, 2020): R30—R37. http://dx.doi.org/10.1152/ajpregu.00263.2019.
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The exercise pressor reflex is composed of two components, namely the muscle mechanoreflex and the muscle metaboreflex. The afferents evoking the two components are either thinly myelinated (group III) or unmyelinated (group IV); in combination they are termed “thin fiber afferents.” The exercise pressor reflex is often studied in unanesthetized, decerebrate rats. However, the relationship between the magnitude of this reflex and the number of thin fiber afferents stimulated by muscle contraction is unknown. This lack of knowledge prompted us to test the hypothesis that the magnitude of the exercise pressor reflex was directly proportional to the amount of muscle mass activated. Muscle mechanoreceptors were stimulated by stretching the calcaneal tendon. Likewise, muscle metaboreceptors were stimulated by injecting lactic acid into the arterial supply of the hindlimb muscles. In addition, both muscle mechanoreceptors and metaboreceptors were stimulated by statically contracting the hindlimb muscles. We found that simultaneous bilateral (both hindlimbs) stimulation of thin fiber afferents with stretch, lactic acid, and static contraction evoked significantly greater pressor responses than did unilateral (one hindlimb) stimulation of these afferents. In addition, the magnitude of the pressor responses to bilateral simultaneous stimulation of thin fiber afferents evoked by stretch, lactic acid, and contraction was not significantly different from the magnitude of the sum of the pressor responses evoked by unilateral stimulation of these afferents by stretch, lactic acid, and contraction. We conclude that the magnitude of the exercise pressor reflex and its two components is dependent on the number of afferents stimulated.
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Yuktasir, Bekir. "Warm-up: A case study on maximal oxygen consumption as it relates to acute stretching." Journal of Human Kinetics 19, no. 1 (January 1, 2008): 165–76. http://dx.doi.org/10.2478/v10078-008-0013-y.
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Warm-up: A case study on maximal oxygen consumption as it relates to acute stretchingThe aim of this study was to determine the acute effects of static and Proprioceptive Neuromuscular Facilitation (PNF) stretches on maximal oxygen consumption (VO2max). Ten physically active men (mean ± SD, 23.80 ± 1.54 years, 70.60 ± 9.70 kg, 1.74.60 ± 5.23 m), who were healthy students volunteered to take part in the study. The participants were subjected to Static and PNF stretching exercises. After the interventions, the Bruce treadmill protocol was applied to measure VO2max values. The expired gases were collected and analyzed continuously using the Cortex Metalyzer II. Analysis of variance showed significant main effects for interventions (F(2,18)=10.74, p<.05) on VO2max. The main result of this study showed that both static and PNF stretching exercises improved VO2max values.
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Abdel-aziem, Amr Almaz, and Walaa Sayed Mohammad. "Plantar-flexor static stretch training effect on eccentric and concentric peak torque – a comparative study of trained versus untrained subjects." Journal of Human Kinetics 34, no. 1 (October 1, 2012): 49–58. http://dx.doi.org/10.2478/v10078-012-0063-z.
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AbstractThe aim of this study was to examine the long-term effects of static stretching of the plantar-flexor muscles oneccentric and concentric torque and ankle dorsiflexion range of motion in healthy subjects. Seventy five healthy malevolunteers, with no previous history of trauma to the calf that required surgery, absence of knee flexion contracture andno history of neurologic dysfunction or disease, systemic disease affecting the lower extremities were selected for thisstudy. The participants were divided into three equal groups. The control group did not stretch the plantar-flexormuscles. Two Experimental groups (trained and untrained) were instructed to perform static stretching exercise of 30second duration and 5 repetitions twice daily. The stretching sessions were carried out 5 days a week for 6 weeks. Thedorsiflexion range of motion was measured in all subjects. Also measured was the eccentric and concentric torque ofplantar-flexors at angular velocities of 30 and 120o/s pre and post stretching. Analysis of variance showed a significantincrease in plantar-flexor eccentric and concentric torque (p < 0.05) of trained and untrained groups, and an increase indorsiflexion range of motion (p < 0.05) at both angular velocities for the untrained group only. The static stretchingprogram of plantar-flexors was effective in increasing the concentric and eccentric plantarflexion torque at angularvelocities of 30 and 120o/s. Increases in plantar-flexors flexibility were observed in untrained subjects.
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Grotle, Ann-Katrin, Charles K. Crawford, Yu Huo, Kai M. Ybarbo, Michelle L. Harrison, James Graham, Kimber L. Stanhope, Peter J. Havel, Paul J. Fadel, and Audrey J. Stone. "Exaggerated cardiovascular responses to muscle contraction and tendon stretch in UCD type-2 diabetes mellitus rats." American Journal of Physiology-Heart and Circulatory Physiology 317, no. 2 (August 1, 2019): H479—H486. http://dx.doi.org/10.1152/ajpheart.00229.2019.
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Patients with type-2 diabetes mellitus (T2DM) have exaggerated sympathetic activity and blood pressure responses to exercise. However, the underlying mechanisms for these responses, as well as how these responses change throughout disease progression, are not completely understood. For this study, we examined the effect of the progression of T2DM on the exercise pressor reflex, a critical neurocardiovascular mechanism that functions to increase sympathetic activity and blood pressure during exercise. We also aimed to examine the effect of T2DM on reflexive cardiovascular responses to static contraction, as well as those responses to tendon stretch when an exaggerated exercise pressor reflex was present. We evoked the exercise pressor reflex and mechanoreflex by statically contracting the hindlimb muscles and stretching the Achilles tendon, respectively, for 30 s. We then compared pressor and cardioaccelerator responses in unanesthetized, decerebrated University of California Davis (UCD)-T2DM rats at 21 and 31 wk following the onset of T2DM to responses in healthy nondiabetic rats. We found that the pressor response to static contraction was greater in the 31-wk T2DM [change in mean arterial pressure (∆MAP) = 39 ± 5 mmHg] but not in the 21-wk T2DM (∆MAP = 24 ± 5 mmHg) rats compared with nondiabetic rats (∆MAP = 18 ± 2 mmHg; P < 0.05). Similarly, the pressor and the cardioaccelerator responses to tendon stretch were significantly greater in the 31-wk T2DM rats [∆MAP = 69 ± 6 mmHg; change in heart rate (∆HR) = 28 ± 4 beats/min] compared with nondiabetic rats (∆MAP = 14 ± 2 mmHg; ∆HR = 5 ± 3 beats/min; P < 0.05). These findings suggest that the exercise pressor reflex changes as T2DM progresses and that a sensitized mechanoreflex may play a role in exaggerating these cardiovascular responses. NEW & NOTEWORTHY This is the first study to provide evidence that as type-2 diabetes mellitus (T2DM) progresses, the exercise pressor reflex becomes exaggerated, an effect that may be due to a sensitized mechanoreflex. Moreover, these findings provide compelling evidence suggesting that impairments in the reflexive control of circulation contribute to exaggerated blood pressure responses to exercise in T2DM.
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Flanigan, Ryan M., Deborah A. Nawoczenski, Linlin Chen, Hulin Wu, and Benedict F. DiGiovanni. "The Influence of Foot Position on Stretching of the Plantar Fascia." Foot & Ankle International 28, no. 7 (July 2007): 815–22. http://dx.doi.org/10.3113/fai.2007.0815.
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Background A recent study found nonweightbearing stretching exercises specific to the plantar fascia to be superior to the standard program of weightbearing Achilles tendon-stretching exercises in patients with chronic plantar fasciitis. The present study used a cadaver model to demonstrate the influence of foot and ankle position on stretching of the plantar fascia. Methods Twelve fresh-frozen lower-leg specimens were tested in 15 different configurations representing various combinations of ankle and metatarsophalangeal (MTP) joint dorsiflexion, midtarsal transverse plane abduction and adduction, and forefoot varus and valgus. Measurements were recorded by a differential variable reluctance transducer (DVRT) implanted into the medial band of the plantar fascia, and primary measurement was a percent deformation of the plantar fascia (stretch) with respect to a reference position (90 degrees ankle dorsiflexion, 0 degrees midtarsal and forefoot orientation, and 0 degrees MTP dorsiflexion). Results Ankle and MTP joint dorsiflexion produced a significant increase (14.91%) in stretch compared to the position of either ankle dorsiflexion alone (9.31% increase, p < 0.001) or MTP dorsiflexion alone (7.33% increase, p < 0.01). There was no significant increase in stretch with positions of abduction or varus (2.49%, p = 0.27 and 0.55%, p = 0.79). Conclusion This study provides a mechanical explanation for enhanced outcomes in recent clinical trials using plantar fascia tissue-specific stretching exercises and lends support to the use of ankle and MTP joint dorsiflexion when employing stretching protocols for nonoperative treatment in patients with chronic proximal plantar fasciitis.
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Brandenburg, Jason, William A. Pitney, Paul E. Luebbers, Arun Veera, and Alicja Czajka. "Time Course of Changes in Vertical-Jumping Ability After Static Stretching." International Journal of Sports Physiology and Performance 2, no. 2 (June 2007): 170–81. http://dx.doi.org/10.1123/ijspp.2.2.170.
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Purpose:To examine the acute effects of static stretching on countermovement vertical-jump (CMVJ) ability and monitor the time course of any stretch-induced changes.Methods:Once familiarized, 16 experienced jumpers completed 2 testing sessions in a randomized order. Each session consisted of a general warm-up, a pretreatment CMVJ assessment, a treatment, and multiple posttreatment CMVJ assessments. One treatment included lower-body static stretching, and the second treatment, involving no stretching, was the control. Posttreatment CMVJ measures occurred immediately, 3, 6, 12, and 24 minutes posttreatment. Stretching consisted of 3 static-stretching exercises, with each exercise repeated 3 times and each repetition held for 30 s.Results:Prestretch CMVJ height equaled 47.1 (± 9.7) cm. CMVJ height immediately poststretch was 45.7 (± 9.2) cm, and it remained depressed during the 24-min follow-up period. Pre-no-stretch CMVJ height was 48.4 (± 9.8) cm, whereas immediately post-no-stretch CMVJ height equaled 46.8 (± 9.5) cm, and as in the stretch treatment, post-no-stretch CMVJ height remained lower than pre-no-stretch values. Although there was a significant main effect of time (P = .005), indicating that CMVJ was lower and remained impaired after both treatments, no significant interaction effect (P = .749) was observed.Conclusion:In comparison with the no-activity control, static stretching resulted in similar reductions in CMVJ ability when examined over the same time course, so athletes preparing for CMVJ should avoid periods of inactivity, as well as static stretching.
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Waters, Christopher M., Karen M. Ridge, G. Sunio, K. Venetsanou, and Jacob Iasha Sznajder. "Mechanical stretching of alveolar epithelial cells increases Na+-K+-ATPase activity." Journal of Applied Physiology 87, no. 2 (August 1, 1999): 715–21. http://dx.doi.org/10.1152/jappl.1999.87.2.715.
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Alveolar epithelial cells effect edema clearance by transporting Na+ and liquid out of the air spaces. Active Na+ transport by the basolaterally located Na+-K+-ATPase is an important contributor to lung edema clearance. Because alveoli undergo cyclic stretch in vivo, we investigated the role of cyclic stretch in the regulation of Na+-K+-ATPase activity in alveolar epithelial cells. Using the Flexercell Strain Unit, we exposed a cell line of murine lung epithelial cells (MLE-12) to cyclic stretch (30 cycles/min). After 15 min of stretch (10% mean strain), there was no change in Na+-K+-ATPase activity, as assessed by86Rb+uptake. By 30 min and after 60 min, Na+-K+-ATPase activity was significantly increased. When cells were treated with amiloride to block amiloride-sensitive Na+ entry into cells or when cells were treated with gadolinium to block stretch-activated, nonselective cation channels, there was no stimulation of Na+-K+-ATPase activity by cyclic stretch. Conversely, cells exposed to Nystatin, which increases Na+ entry into cells, demonstrated increased Na+-K+-ATPase activity. The changes in Na+-K+-ATPase activity were paralleled by increased Na+-K+-ATPase protein in the basolateral membrane of MLE-12 cells. Thus, in MLE-12 cells, short-term cyclic stretch stimulates Na+-K+-ATPase activity, most likely by increasing intracellular Na+ and by recruitment of Na+-K+-ATPase subunits from intracellular pools to the basolateral membrane.
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Gifford, Jayson R. "Stretching‐based vascular rehabilitation? it's not a stretch." Journal of Physiology 598, no. 17 (July 6, 2020): 3537–38. http://dx.doi.org/10.1113/jp280278.
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Abdelall, Esraa S., Bethany R. Lowndes, Amro M. Abdelrahman, Hunter J. Hawthorne, and M. Susan Hallbeck. "Mini Breaks, Many Benefits: Development and Pilot Testing of an Intraoperative Microbreak Stretch Web-Application for Surgeons." Proceedings of the Human Factors and Ergonomics Society Annual Meeting 62, no. 1 (September 2018): 1042–46. http://dx.doi.org/10.1177/1541931218621240.
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Periodic intraoperative microbreaks with calesthenic exercises performed within the sterile field improved self-reported mental focus (38%) and physical performance (57%) for 56 surgeons. Therefore, targeted stretching exercises and a web-application (web-app) leading the stretches with a reminder system were developed and piloted using user-centered design principles. A focus group with 10 users was conducted to refine the developed app. Seven surgeons (4 females) at a quaternary medical institute piloted the periodic stretching web-app in their operating rooms. At the end of each surgical day, the surgeons completed a short survey about the intraoperative stretching exercises web-app impact on their physical performance, mental focus and workflow disruption. Non-Routine Events were captured during the procedures. Twelve surgical days were followed with a median of 6 microbreaks/day/surgeon. Results showed that better physical performance and lower fatigue were reported (91.7%) across the surgical days, also better mental focus was reported (83.3%) across the surgical days, and less pain/discomfort was reported (100%) across the surgical days, with others reporting no change. The web-app leading sterile field microbreak stretches helped reduce physical pain, discomfort/pain, fatigue, and improve mental focus with minimal disruption for a small sample. The web-app is a promising tool for improving surgeon mental focus and physical performance and potentially musculoskeletal health.
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Kyröläinen, Heikki, and Paavo V. Komi. "Neuromuscular function with different stretching velocities in the stretch-shortening cycle (SSC) exercises." Journal of Biomechanics 27, no. 6 (January 1994): 704. http://dx.doi.org/10.1016/0021-9290(94)91082-0.
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Branco, Kim C., and M. Moodley. "Chiropractic manipulative therapy of the thoracic spine in combination with stretch and strengthening exercises, in improving postural kyphosis in woman." Health SA Gesondheid 21 (October 11, 2016): 303–8. http://dx.doi.org/10.4102/hsag.v21i0.982.
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Purpose: This study serves to determine the effectiveness of either chiropractic spinal manipulative therapy to the thoracic spine or stretch and strengthening exercises (stretching the pectoralis major muscle and strengthening the rhomboid, middle and inferior trapezius muscles) versus the combined treatment of chiropractic spinal manipulative therapy to the thoracic spine in conjunction with stretch and strengthening exercises.Method: A randomised study design with thirty female participants between the ages of twenty and thirty nine was selected. Group 1 (n = 10) received chiropractic spinal manipulative therapy to the thoracic spine. Group 2 (n = 10) received chiropractic spinal manipulative therapy to the thoracic spine as well as stretch and strengthening exercises i.e. stretching the pectoralis major muscles and strengthening the rhomboid, middle and inferior trapezius muscles. Group 3 (n = 10) received stretch and strengthening exercises. The stretch and strengthening exercises were performed in the consultation rooms to ensure that the participants were complying with the treatment and doing the exercises properly. The study consisted of seven consultations for Group 1 (they received treatment once a week for six weeks) and for Groups 2 and 3 there were nineteen consultations (they received three treatments a week for six weeks). Objective data was recorded at the beginning of the first, fourth and seventh consultations for Group 1, and the first, tenth and nineteenth consultations for Groups 2 and 3. On the seventh consultation (for Group 1) and nineteenth consultation for Groups 2 and 3, only data collection was done. Objective data were obtained by using the Flexicurve® Ruler measurements for the angle of kyphosis. Visual analysis was done by taking lateral (sagittal) view photographs at the beginning of the initial and final consultations.Results: Statistical analysis revealed significant statistical changes for the intragroup results for all three groups. No significant statistical difference was found between the groups for the inter-group analysis.Conclusion: The study showed that all three treatment protocols for Groups 1, 2, and 3 were effective. However, Group 1 had not shown a great improvement in their postural kyphosis, Group 3 had shown a relatively good improvement in their posture, while Group 2 had shown the best results with regards to improvement of the participants' posture. Therefore, in conclusion, Groups 2 and 3 treatment protocols can be used effectively to treat postural kyphosis but Group 2's treatment protocol, consisting of chiropractic spinal manipulative therapy to the thoracic spine in combination with stretch and strengthening exercises, will yield the best results.
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Tanaka, Yoshio, Shinzo Hata, Hiromi Ishiro, Kunio Ishii, and Koichi Nakayama. "Stretching releases Ca2+ from intracellular storage sites in canine cerebral arteries." Canadian Journal of Physiology and Pharmacology 72, no. 1 (January 1, 1994): 19–24. http://dx.doi.org/10.1139/y94-004.
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Mechanical stretch applied to canine cerebral artery produced myogenic contraction. The contraction of the artery in response to quick stretch was dependent on not only the transmembrane influx of Ca2+ through 1,4-dihydropyridine-sensitive Ca2+ channels but also the release of Ca2+ from intracellular storage sites: the stretch-produced contractile component that was resistant to 0.1 μM nicardipine, a Ca2+-channel antagonist, was inhibited by about 50% after treatment with ryanodine, and was almost completely suppressed by 0.1 mM 2-nitro-4-carboxyphenyl-N,N-diphenylcarbamate, a putative phospholipase C inhibitor, or by lowering the temperature from 35 to 20 °C. The results suggest that in addition to transmembrane influx of Ca2+ through L-type Ca2+ channels, the release of Ca2+ from both ryanodine-sensitive and -insensitive intracellular storage sites, which increases intracellular Ca2+, accounts for the stretch-induced contraction of canine basilar artery. It seems also possible that inositol 1,4,5-trisphosphate is a common mediator for the release of Ca2+ from both types of intracellular storage sites.Key words: stretch-induced contraction, cerebral artery, phospholipase C, ryanodine, Ca2+ storage sites, inositol 1,4,5-trisphosphate, Ca2+ release, Ca2+-channel antagonist.
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Chakraborty, Manoj Kumar, Pratendra Raj Onta, and Brijesh Sathian. "Efficacy of Stretching Exercises in the Treatment of Chronic Plantar Fasciitis: A Prospective Study in Manipal Teaching Hospital, Pokhara, Nepal." Asian Journal of Medical Sciences 2, no. 2 (September 17, 2011): 97–101. http://dx.doi.org/10.3126/ajms.v2i2.4218.
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Objective: Chronic plantar fasciitis developed in ten percent of cases with poor response. Specific plantar stretching exercises alone improves the patient with better outcome. It is self limited process with resolution of symptoms within one year but five percent cases may require surgical intervention in intractable cases. The purpose of this study was to evaluate the long term outcomes of the plantar fascia specific stretching exercise only for chronic plantar fasciitis. Material & Methods: 50 patients with chronic plantar fasciitis for more than three month duration were enrolled in our study for post treatment follow up with effect from Jan 2010 to Jan 2011 in Department of Orthopedics of Manipal College of Medical Sciences. All patients received plantar specific stretching exercise protocol for twelve months interval of one week, three week, two months, six months and twelve months. Results: Out of 50 patients, 36(72%) were female and 14 (28%) were male. 36(72%) were left sided and 14 (28%) were right. Mean age of patients were 46.12±SD7.11 years. The pre treatment mean visual analogue scale score for all patients is significantly higher than every follow up (p=0.0001). Conclusion: This stretching of the plantar fascia is a modification of the traditional stretch weight bearing to tissue specific plantar fascia stretching protocol to optimize tissue tension through a controlled stretch of plantar fascia by recreation of windlass mechanism with high rate of satisfaction in regards to decrease of pain and functional limitations. Key Words: Chronic plantar fasciitis; stretching; windlass mechanism DOI: http://dx.doi.org/10.3126/ajms.v2i2.4218 Asian Journal of Medical Sciences 2 (2011) 97-101
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Kruse, Nicholas T., Christopher R. Silette, and Barry W. Scheuermann. "Influence of passive stretch on muscle blood flow, oxygenation and central cardiovascular responses in healthy young males." American Journal of Physiology-Heart and Circulatory Physiology 310, no. 9 (May 1, 2016): H1210—H1221. http://dx.doi.org/10.1152/ajpheart.00732.2015.
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The aim of this study was to examine the effect of skeletal muscle stretching on peripheral, central, and autonomic cardiovascular responses in humans. Twelve healthy males completed a controlled passive stretch of the plantar flexors for 4 min at three different intensities. Doppler ultrasound velocimetry and imaging techniques assessed mean leg blood flow (MLBF), antegrade blood flow, and retrograde blood flow of the popliteal artery. Near-infrared spectroscopy assessed the concentration of deoxygenated hemoglobin + myoglobin ([HHb]) and the sum of its deoxygenated and oxygenated forms [i.e., blood volume ([Hbtot])]. Heart rate (HR) and mean arterial pressure were measured simultaneously to peripheral hemodynamic responses. During stretch there was an increase ( P < 0.05) in antegrade and retrograde blood flow along with [HHb] and [Hbtot] relative to baseline, whereas MLBF was not altered. HR increased ( P < 0.01) in a stretch intensity- and time-dependent manner, suggesting a threshold tension must be met that results in a mechanoreflex-mediated increase in HR. After stretch there was an increase ( P < 0.05) in [Hbtot] and MLBF in each condition, suggesting that stretch creates a poststretch hyperemic response. Furthermore, retrograde blood flow was decreased ( P < 0.05) after stretch in each stretch condition. Mean arterial pressure was decreased ( P < 0.05) after moderate-intensity stretching. Collectively, our data provide novel mechanistic evidence on cardiovascular responses to skeletal muscle stretching in humans. Moreover, the reductions in MAP and retrograde blood flow suggest that stretch transiently reduces myogenic vascular tone in a poststretch resting period.
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Jesudason, Rajiv, Lauren Black, Arnab Majumdar, Phillip Stone, and Bela Suki. "Differential effects of static and cyclic stretching during elastase digestion on the mechanical properties of extracellular matrices." Journal of Applied Physiology 103, no. 3 (September 2007): 803–11. http://dx.doi.org/10.1152/japplphysiol.00057.2007.
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Enzyme activity plays an essential role in many physiological processes and diseases such as pulmonary emphysema. While the lung is constantly exposed to cyclic stretching, the effects of stretch on the mechanical properties of the extracellular matrix (ECM) during digestion have not been determined. We measured the mechanical and failure properties of elastin-rich ECM sheets loaded with static or cyclic uniaxial stretch (40% peak strain) during elastase digestion. Quasistatic stress-strain measurements were taken during 30 min of digestion. The incremental stiffness of the sheets decreased exponentially with time during digestion. However, digestion in the presence of static stretch resulted in an accelerated stiffness decrease, with a time constant that was nearly 3× smaller (7.1 min) than during digestion alone (18.4 min). These results were supported by simulations that used a nonlinear spring network model. The reduction in stiffness was larger during static than cyclic stretch, and the latter also depended on the frequency. Stretching at 20 cycles/min decreased stiffness less than stretching at 5 cycles/min, suggesting a rate-dependent coupling between mechanical forces and enzyme activity. Furthermore, pure digestion reduced the failure stress of the sheets from 88 ± 21 kPa in control to 29 ± 15 kPa ( P < 0.05), while static and cyclic stretch resulted in a failure stress of 7 ± 5 kPa ( P < 0.05). We conclude that not only the presence but the dynamic nature of mechanical forces have a significant impact on enzyme activity, hence the deterioration of the functional properties of the ECM during exposure to enzymes.
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Avela, Janne, Heikki Kyröläinen, and Paavo V. Komi. "Altered reflex sensitivity after repeated and prolonged passive muscle stretching." Journal of Applied Physiology 86, no. 4 (April 1, 1999): 1283–91. http://dx.doi.org/10.1152/jappl.1999.86.4.1283.
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Experiments were carried out to test the effect of prolonged and repeated passive stretching (RPS) of the triceps surae muscle on reflex sensitivity. The results demonstrated a clear deterioration of muscle function immediately after RPS. Maximal voluntary contraction, average electromyographic activity of the gastrocnemius and soleus muscles, and zero crossing rate of the soleus muscle (recorded from 50% maximal voluntary contraction) decreased on average by 23.2, 19.9, 16.5, and 12.2%, respectively. These changes were associated with a clear immediate reduction in the reflex sensitivity; stretch reflex peak-to-peak amplitude decreased by 84.8%, and the ratio of the electrically induced maximal Hoffmann reflex to the maximal mass compound action potential decreased by 43.8%. Interestingly, a significant ( P < 0.01) reduction in the stretch-resisting force of the measured muscles was observed. Serum creatine kinase activity stayed unaltered. This study presents evidence that the mechanism that decreases the sensitivity of short-latency reflexes can be activated because of RPS. The origin of this system seems to be a reduction in the activity of the large-diameter afferents, resulting from the reduced sensitivity of the muscle spindles to repeated stretch.
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Xiao, Wen-lin, Dai-zun Zhang, Cun-hui Fan, and Bao-jun Yu. "Intermittent Stretching and Osteogenic Differentiation of Bone Marrow Derived Mesenchymal Stem Cells via the p38MAPK-Osterix Signaling Pathway." Cellular Physiology and Biochemistry 36, no. 3 (2015): 1015–25. http://dx.doi.org/10.1159/000430275.
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Aims: The relationship between the p38MAPK signaling pathway and osterix in osteogenic differentiation of BMMSCs subjected to intermittent stretching was investigated. Methods: BMMSCs derived from C57BL/6J mice were divided into the following groups: 1) control, 2) stretch, and 3) SB203580+stretch (SB203580 is a p38MAPK signal pathway inhibitor). BMMSCs were exposed to an intermittent mechanical strain of 0.8% (8000μ strain) at 0.5 Hz, twice a day for 30 min each application. BMMSCs were harvested on days 1, 3, and 5 post-treatment. The expression of ALP, COL I, OCN, and osterix mRNA was assessed utilizing RT-PCR while the expression of P-p38MAPK and osterix protein was assessed by Western blot analysis. The osterix gene in mouse BMMSCs was knocked down using RNAi technology and its protein expression was also assessed by Western blot. RT-PCR was used to detect ALP, COL I, and OCN mRNA expression. Results: Intermittent stretching was found to promote expression of ALP, COL I, OCN, and osterix mRNA. Silencing the osterix gene was found to reduce levels of ALP, COL I, and OCN mRNA. Western blot analysis demonstrated that the levels of osterix and P-p38MAPK proteins in the stretch group were significantly higher than in the control group (P<0.05). There was less expression of ALP, COL I, OCN, and osterix mRNA in the SB203580+stretch group than in the control and stretch groups. Conclusions: Data demonstrate that intermittent stretching promotes osteogenic differentiation of BMMSCs, and the p38MAPK-osterix pathway has an important role in the control of osteogenesis-related gene expression.
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Irshad, Sameha, Arshad Nawaz Malik, and Sahreen Anwar. "LUMBAR POSTURAL SYNDROME." Professional Medical Journal 23, no. 10 (October 10, 2016): 1232–36. http://dx.doi.org/10.29309/tpmj/2016.23.10.1728.
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Background: The most prevalent disabling condition in clinical practice islow back pain. The poor posture has highest risk for the development of low back pain inyoung population. There is different conservative treatment approaches used to treat lumbarpostural syndrome. Purpose of The Study: The objective was to determine the effectivenessof Piriformis stretching with hip external rotation in the treatment of lumbar postural syndrome.Study Design: Randomized control. Setting: District Headquarter hospital Faisalabad. Period:06 month from 01st January- 30th June 2014. Materials and Methods: The purposive samplingtechnique was used to collect sample of 30 patients and then assigned to 2 groups randomly(Hip external rotation HER and Hip Internal rotation HIR group). Standardized treatment protocolinclude heating modality, hamstring stretching, back strengthening & stretching exercises andpostural education was implemented to all patients. Participants in the hip external rotation(HER) group received Piriformis stretch with hip external rotation and participants in HipInternal rotation (HIR) group received piriformis stretch with hip internal rotation as an additionaltreatment in order to compare both stretch positions. The changes in the symptoms weremeasured in the form of pain and Modified Oswestry Disability Index (MODI). Results: Thestatistical analysis showed the P value for total score of Modified Oswestry Disability Index(MODI) was (0.00<0.05). So there is a significant difference in both group showing that thepiriformis stretching with hip external rotation is effective than hip internal rotation combinedwith conventional physical therapy in subjects with lumbar postural syndrome. Conclusions:It is concluded that piriformis stretching with hip external rotation together with conventionaltreatment is an effective treatment approach in treating lumbar postural syndrome.
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Behm, David G., Duane C. Button, and Jeremy C. Butt. "Factors Affecting Force Loss With Prolonged Stretching." Canadian Journal of Applied Physiology 26, no. 3 (June 1, 2001): 262–72. http://dx.doi.org/10.1139/h01-017.
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The purpose of this study was to investigate factors underlying the force loss occurring after prolonged, static, passive stretching. Subjects were tested before and 5-10 min following 20 min of static, passive stretching of the quadriceps (N = 12) or a similar period of no stretch (control, N = 6). Measurements included isometric maximal voluntary contraction (MVC) force, surface integrated electromyographic (iEMG) activity of the quadriceps and hamstrings, evoked contractile properties (twitch and tetanic force), and quadriceps inactivation as measured by the interpolated twitch technique (ITT). Following stretching, there was a significant 12% decrement in MVC with no significant changes in the control group. Muscle inactivation as measured by the ITT and iEMG increased by 2.8% and 20.2%, respectively. While twitch forces significantly decreased 11.7%, there was no change in tetanic force post-stretch. Although possible increases in muscle compliance affected twitch force, a lack of tetanic force change would suggest that post-stretch force decrements are more affected by muscle inactivation than changes in muscle elasticity. Key Words: antagonist, electromyography, maximum voluntary contraction, muscle activation, twitch, tetanus
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Sobko, I. M., O. V. Koliesov, and L. O. Ulaeva. "Method for the development of physical qualities of tennis players 12-13 years old using react balls and stretching." Health, sport, rehabilitation 5, no. 2 (July 5, 2019): 88. http://dx.doi.org/10.34142/hsr.2019.05.02.10.
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<p><strong>The purpose</strong> – to develop and experimentally substantiate the method of developing the physical qualities of tennis players aged 12–13 years old, using React Balls and stretching.</p><p><strong>Material and methods</strong>. The experiment was attended by 28 tennis players 12-13 years old sport school № 3, Severodonetsk, who were divided into control and experimental group of 14 people. The study was conducted within 8 months from August 2018 to March 2019. Before and after the experiment, tennis players' physical fitness was tested (shuttle run 6x8 m, push-ups 30 s, jumps with skipping-rope, running 6 m, running 30 m, long jump from the spot, throwing ball 1 kg, torso inclination forward from a sitting position, circular rotations in the shoulder joint with a gymnastic stick).</p><p><strong>Results</strong><em>. </em>Complexes of exercises with React Balls and stretch exercises for all muscle groups were developed and introduced into the training process of young tennis players. A significant (p<0.05) increase in the flexibility indicators of athletes from the experimental group, as a result of the use of stretch exercises, was determined. It was revealed that doing exercises with React Balls and tennis balls significantly (p <0.05) increased the level of speed and coordination capabilities in the control and experimental groups. According to the test results «running 30 m», «circular rotations in the shoulder joint with a gymnastic stick», «torso inclination forward from a sitting position» in the experimental group, these figures are significantly higher compared with the athletes of the control group.</p><p><strong>Conclusions.</strong> It was shown that the use of stretching exercises contributes to the development of greater amplitude of movements, and also forms motor freedom, which affects the development of coordination and speed of movement of a tennis player. It is recommended to use the method of development of physical qualities using React Balls and stretching balls in the training process of young tennis players 12-13 years old.</p>
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Richardson, W. J., E. Wilson, and J. E. Moore. "Altered phenotypic gene expression of 10T1/2 mesenchymal cells in nonuniformly stretched PEGDA hydrogels." American Journal of Physiology-Cell Physiology 305, no. 1 (July 1, 2013): C100—C110. http://dx.doi.org/10.1152/ajpcell.00340.2012.
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Disease-related phenotype modulation of many cell types has been shown to be closely related to mechanical loading conditions; for example, vascular smooth muscle cell (SMC) phenotype shift from a mature, contractile state to a proliferative, synthetic state contributes to the formation of neointimal tissue during atherosclerosis and restenosis development and is related to SMC mechanical loading in vivo. The majority of past in vitro cell-stretching experiments have employed simplistic (uniform, uniaxial or biaxial) stretching environments to elucidate mechanobiological pathways involved in phenotypic shifts. However, the in vivo mechanics of the vascular wall consists of highly nonuniform stretch. Here we subjected 10T1/2 murine mesenchymal cells (an SMC precursor) to two- and three-dimensional nonuniform stretch environments. After 24 h of stretch, cells on an elastomeric membrane demonstrated varied proliferation [assessed by 5-bromo-2′-deoxyuridine (BrdU) incorporation] depending on location upon the membrane, with maximal proliferation occurring in a region of high, uniaxial stretch. Cells subjected to a nonuniform stretching regimen within three-dimensional polyethylene glycol diacrylate (PEGDA) hydrogel constructs demonstrated marked changes in mRNA expression of several phenotype-related proteins, indicating a sort of “hybrid” phenotype with contractile and synthetic markers being both upregulated and downregulated. Furthermore, expression levels of mRNAs were significantly different between various locations within the stretched gel. With the proliferation results, these data exhibit the capability of nonuniform stretching devices to induce heterogeneous cell responses, potentially indicative of spatial distributions of disease-related behaviors in vivo.
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Hibberd, Elizabeth E., Sakiko Oyama, Jeffrey T. Spang, William Prentice, and Joseph B. Myers. "Effect of a 6-Week Strengthening Program on Shoulder and Scapular-Stabilizer Strength and Scapular Kinematics in Division I Collegiate Swimmers." Journal of Sport Rehabilitation 21, no. 3 (August 2012): 253–65. http://dx.doi.org/10.1123/jsr.21.3.253.
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Context:Shoulder injuries are common in swimmers because of the demands of the sport. Muscle imbalances frequently exist due to the biomechanics of the sport, which predispose swimmers to injury. To date, an effective shoulder-injury-prevention program for competitive swimmers has not been established.Objective:To assess the effectiveness of a 6-wk strengthening and stretching intervention program on improving glenohumeral and scapular muscle strength and scapular kinematics in collegiate swimmers.Design:Randomized control trial.Setting:University biomechanics research laboratory.Participants:Forty-four Division I collegiate swimmers.Interventions:The intervention program was completed 3 times per week for 6 wk. The program included strengthening exercises completed using resistance tubing—scapular retraction (Ts), scapular retraction with upward rotation (Ys), scapular retraction with downward rotation (Ws), shoulder flexion, low rows, throwing acceleration and deceleration, scapular punches, shoulder internal rotation at 90° abduction, and external rotation at 90° abduction—and 2 stretching exercises: corner stretch and sleeper stretch.Main Outcome Measurements:Scapular kinematics and glenohumeral and scapular muscle strength assessed preintervention and postintervention.Results:There were no significant between-groups differences in strength variables at pre/post tests, although shoulder-extension and internal-rotation strength significantly increased in all subjects regardless of group assignment. Scapular kinematic data revealed increased scapular internal rotation, protraction, and elevation in all subjects at posttesting but no significant effect of group on the individual kinematic variables.Conclusions:The current strengthening and stretching program was not effective in altering strength and scapular kinematic variables but may serve as a framework for future programs. Adding more stretching exercises, eliminating exercises that overlap with weight-room training and swim training, and timing of implementation may yield a more beneficial program for collegiate swimmers.
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Naruse, K., and M. Sokabe. "Involvement of stretch-activated ion channels in Ca2+ mobilization to mechanical stretch in endothelial cells." American Journal of Physiology-Cell Physiology 264, no. 4 (April 1, 1993): C1037—C1044. http://dx.doi.org/10.1152/ajpcell.1993.264.4.c1037.
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Endothelial cells are subjected to shear stresses by blood flow, normal stresses by blood pressure, and stretch by vessel expansion. These forces are known to induce secretions of several vasoactive substances probably via internal calcium mobilization (R. F. Furchgott. Circ. Res. 53: 557-573, 1983; M. J. Peach, A. L. Loeb, H. A. Singer, and J. Saye. Hypertension Dallas 7, Suppl. I: I-94-I-100, 1985). Here we report that stretching cellular membranes increased intracellular Ca2+ concentration ([Ca2+]i) in human umbilical endothelial cells cultured on silicon membranes. Upon application of a stretch pulse (3-s duration), [Ca2+]i increased rapidly and decayed slowly. The following results suggest that this increase arises from Ca2+ entry through stretch-activated (SA) channels: 1) the Ca2+ response disappeared when extracellular Ca2+ was removed; 2) gadolinium (Gd3+), a blocker for cation-selective SA channels, blocked the response but nifedipine did not; and 3) externally applied Mn2+, which is known to permeate mechanosensitive channels but not Ca2+ channels, entered the intracellular space immediately after an application of mechanical stretch. The increase in [Ca2+]i was found to consist of at least two components: an initial fast component and a delayed slower component. Ryanodine inhibited the slow component. It is suggested that stretching the membrane primarily induced extracellular Ca2+ entry through SA channels followed by Ca2+ releases from intracellular Ca2+ stores.
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Chorro, Francisco J., Isabel Trapero, Luis Such-Miquel, Francisca Pelechano, Luis Mainar, Joaquín Cánoves, Álvaro Tormos, et al. "Pharmacological modifications of the stretch-induced effects on ventricular fibrillation in perfused rabbit hearts." American Journal of Physiology-Heart and Circulatory Physiology 297, no. 5 (November 2009): H1860—H1869. http://dx.doi.org/10.1152/ajpheart.00144.2009.
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Stretch induces modifications in myocardial electrical and mechanical activity. Besides the effects of substances that block the stretch-activated channels, other substances could modulate the effects of stretch through different mechanisms that affect Ca2+ handling by myocytes. Thirty-six Langendorff-perfused rabbit hearts were used to analyze the effects of the Na+/Ca2+ exchanger blocker KB-R7943, propranolol, and the adenosine A2 receptor antagonist SCH-58261 on the acceleration of ventricular fibrillation (VF) produced by acute myocardial stretching. VF recordings were obtained with two epicardial multiple electrodes before, during, and after local stretching in four experimental series: control ( n = 9), KB-R7943 (1 μM, n = 9), propranolol (1 μM, n = 9), and SCH-58261 (1 μM, n = 9). Both the Na+/Ca2+ exchanger blocker KB-R7943 and propranolol induced a significant reduction ( P < 0.001 and P < 0.05, respectively) in the dominant frequency increments produced by stretching with respect to the control and SCH-58261 series (control = 49.9%, SCH-58261 = 52.1%, KB-R7943 = 9.5%, and propranolol = 12.5%). The median of the activation intervals, the functional refractory period, and the wavelength of the activation process during VF decreased significantly under stretch in the control and SCH-58261 series, whereas no significant variations were observed in the propranolol and KB-R7943 series, with the exception of a slight but significant decrease in the median of the fibrillation intervals in the KB-R7943 series. KB-R7943 and propranolol induced a significant reduction in the activation maps complexity increment produced by stretch with respect to the control and SCH-58261 series. In conclusion, the electrophysiological effects responsible for stretch-induced VF acceleration in the rabbit heart are reduced by the Na+/Ca2+ exchanger blocker KB-R7943 and by propranolol but not by the adenosine A2 receptor antagonist SCH-58261.
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Resar, J., J. Z. Livingston, H. R. Halperin, P. Sipkema, R. Krams, and F. C. Yin. "Effect of wall stretch on coronary hemodynamics in isolated canine interventricular septum." American Journal of Physiology-Heart and Circulatory Physiology 259, no. 6 (December 1, 1990): H1869—H1880. http://dx.doi.org/10.1152/ajpheart.1990.259.6.h1869.
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The effects of stretch on coronary pressure-flow relations are not well understood. To examine the role of wall stretch per se on coronary hemodynamics, we studied arterially perfused isolated canine interventricular septa in a noncontracting state with vasodilated vessels. We compared the hemodynamic parameters of zero-flow pressure and resistance during passive stretching in the circumferential and the base-to-apex directions alone as well as during simultaneous biaxial stretching in both directions. Even in the unloaded state the zero-flow pressure was positive. Any type of stretching significantly increased the zero-flow pressure and the resistance from their unloaded values. The pressure-flow responses also showed directional dependence. When stretches with matched strains or stresses in each direction were applied sequentially, the resistance increases corresponded to the direction of higher stress. Conversely, the zero-flow pressure response increase corresponded to the direction of greater strain. However, neither response correlated with a measure of global tissue stiffness. Thus there is a complex and tight mechanical interaction between the vessels and the surrounding tissue. These interactions, but not the tissue stiffness, are important determinants of coronary pressure-flow responses during stretch.
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Kerkelä, Risto, Mika Ilves, Sampsa Pikkarainen, Heikki Tokola, Veli-Pekka Ronkainen, Theresa Majalahti, Juhani Leppäluoto, Olli Vuolteenaho, and Heikki Ruskoaho. "Key roles of endothelin-1 and p38 MAPK in the regulation of atrial stretch response." American Journal of Physiology-Regulatory, Integrative and Comparative Physiology 300, no. 1 (January 2011): R140—R149. http://dx.doi.org/10.1152/ajpregu.00853.2009.
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Mechanisms regulating stretch response in the left ventricle are investigated in detail but not well understood in atrial myocardium. Hypertrophic growth of atrial myocardium contributes to the pathogenesis of atrial fibrillation. In this study, we sought to elucidate mechanisms of stretch-induced activation of key signaling pathways and hypertrophy-associated genes in rat atria. Stretching of isolated atria induced a rapid increase in phosphorylation of p38 MAPK and ERK and induced a p38 MAPK-dependent increase in DNA binding activity of transcription factors Elk-1 and GATA-4. Inhibition of the ERK pathway had no effect on the cardiac transcription factors studied. Stretch-induced increase in atrial contractile function was substantially enhanced by inhibition of p38 MAPK. p38 MAPK also regulated stretch-induced increase in c-fos, β-myosin heavy chain, B-type natriuretic peptide mRNA levels, and atrial natriuretic peptide secretion in isolated atria. Various autocrine/paracrine factors are known to mediate the stretch response in the left ventricle. Stretching of isolated atria resulted in a robust increase in endothelin-1 (ET-1) mRNA levels, while apelin and adrenomedullin signaling cascades were downregulated. Administration of mixed ETA/B receptor antagonist bosentan attenuated the stretch-induced activation of GATA-4 in isolated atria, whereas ANG II receptor type-1 antagonist CV-11974 had no effect. Moreover, analysis of RNA from intact atrial and ventricular myocardium revealed significantly higher mRNA levels of ETA receptor and ET converting enzyme-1 in atrial compared with ventricular myocardium. In conclusion, our findings identify the local ET-1 system and p38 MAPK as key regulators of load-induced hypertrophic response in isolated rat atria.
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Yao, Li Qin. "Effect of Proprioceptive Neuromuscular Facilitation on Force-Time Curve and Electromyogram Parameters in Competitive Aerobics Athletes." Advanced Materials Research 108-111 (May 2010): 369–71. http://dx.doi.org/10.4028/www.scientific.net/amr.108-111.369.
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Objective: to investigate the effect of proprioceptive neuromuscular facilitation stretching on force-time curve and EMG Parameters in competitive aerobics athletes. Methods: we take 36 competitive aerobics athletes as participants, and they were tested after bicycle exercise and bicycle exercise/PNF stretching protocol,then the data were compared and analyzed.Conclusion: PNF stretching for lower extremity will not cause the maximum muscular strength and force - time curve parameters (MVC,F100,IRF,and TMVC) significantly decreased in competitive aerobics athletes, however,EMG voltage of rectus femoris has undergone a significant decline,which is showed that PNF stretch will cause change in excited mode,but force - time curve parameters will not be affected significantly.EMG showed that neural inhibition did not affect the maximum isometric muscle strength and characteristics of time - the power curve parameters, indicating PNF stretching can improve capability of muscle coordination.To take full advantage of PNF stretching exercises, changes of muscular strength and force - time curve parameters caused by PNF stretching should be studied in a more comprehensive, in-depth detail.
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Moradi, Elham, Shaghayegh Hashemi Motlagh, and Zahra Nikkhah. "Measurement of the Effect of Static Stretching on Hamstring Flexibility in High School Females." International Journal of Life Sciences 8, no. 5 (January 8, 2015): 18–21. http://dx.doi.org/10.3126/ijls.v8i5.10914.
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Background: flexibility that is one of basic aspects of any sport program , can be developed and acquired through various stretching exercises. This study examined the effect of six-weeks of static stretching on hamstring flexibility in high school females. Methods: Thirty healthy high school females aged 15 to 17 years were randomly assigned to one of two groups. The training group underwent static stretch training of the hamstring with a six-weeks protocol training sessions were 3 days per week, including 4 30-seconds stretches per day for each of subjects. The other group acted as control group. Before and after six-weeks of stretching, flexibility of the hamstring muscles was determined by Sit & Reach Test. Results: A significant increase in flexibility of hamstring was found in training group (mean 31cm to 39/87cm), and no significant difference was revealed in hamstring flexibility after the six-weeks static stretching for the control group. Conclusion: This study indicated that the static stretching significantly increased the hamstring flexibility and suggests that subjects use static stretching for increasing their hamstring flexibility.DOI: http://dx.doi.org/10.3126/ijls.v8i5.10914
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Trepat, Xavier, Mireia Grabulosa, Ferranda Puig, Geoffrey N. Maksym, Daniel Navajas, and Ramon Farré. "Viscoelasticity of human alveolar epithelial cells subjected to stretch." American Journal of Physiology-Lung Cellular and Molecular Physiology 287, no. 5 (November 2004): L1025—L1034. http://dx.doi.org/10.1152/ajplung.00077.2004.
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Alveolar epithelial cells undergo stretching during breathing and mechanical ventilation. Stretch can modify cell viscoelastic properties, which may compromise the balance of forces in the alveolar epithelium. We studied the viscoelasticity of alveolar epithelial cells (A549) subjected to equibiaxial distention with a novel experimental approach. Cells were cultured on flexible substrates and subjected to stepwise deformations of up to 17% with a device built on an inverted microscope. Simultaneously, cell storage (G′) and loss (G″) moduli were measured (0.1–100 Hz) with optical magnetic twisting cytometry. G′ and G″ increased with strain up to 64 and 30%, respectively, resulting in a decrease in G″/G′ (15%). This stretch-induced response was inhibited by disruption of the actin cytoskeleton with latrunculin A. G′ increased with frequency following a power law with exponent α = 0.197. G″ increased proportionally to G′ but exhibited a more marked frequency dependence at high frequencies. Stretching (14%) caused a fall in α (13%). At high stretching amplitudes, actual cell strain (14.4%) was lower than the applied substrate strain (17.3%), which could indicate a partial cell detachment. These data suggest that cytoskeletal prestress modulates the elastic and frictional properties of alveolar epithelial cells in a coupled manner, according to soft glassy rheology. Stretch-induced cell stiffening could compromise the balance of forces at the cell-cell and cell-matrix adhesions.
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Tahran, Özge, and Sevgi Sevi Yeşilyaprak. "Effects of Modified Posterior Shoulder Stretching Exercises on Shoulder Mobility, Pain, and Dysfunction in Patients With Subacromial Impingement Syndrome." Sports Health: A Multidisciplinary Approach 12, no. 2 (February 4, 2020): 139–48. http://dx.doi.org/10.1177/1941738119900532.
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Background: Posterior shoulder stretching exercises (PSSEs) aim to reduce posterior shoulder tightness (PST). Position modification of traditional PSSEs has been suggested to minimize inadequate control of scapular and glenohumeral rotation, possibly leading to increased subacromial impingement. Hypothesis: Modified PSSEs will have positive effects on shoulder mobility, pain, and dysfunction. Study Design: Randomized controlled trial. Level of Evidence: Level 1. Methods: A total of 67 symptomatic patients with subacromial impingement syndrome (SIS) and shoulder internal rotation asymmetry were randomly assigned to 3 groups: modified cross-body stretch (MCS) (n = 22; treatment program + MCS), modified sleeper stretch (MSS) (n = 22; treatment program + MSS), and a control group (n = 23; treatment program consisting of only modalities, range of motion [ROM], and strength training but no PSSEs) for 4 weeks. Pain, PST, shoulder rotation ROM, and dysfunction were evaluated. Results: Pain, PST, shoulder rotation ROM, function, and disability improved in all groups ( P < 0.05). The MCS and MSS groups had better results compared with the control group with regard to pain with activity, internal rotation ROM, function, and disability ( P < 0.05). There was no significant difference between the stretching groups ( P > 0.05). Conclusion: All treatments improved pain, shoulder mobility, function, and disability in patients with SIS. However, modified PSSEs in addition to a treatment program was superior to the treatment program alone (without PSSEs) in improving pain with activity, internal rotation ROM, and dysfunction. Moreover, stretching provided clinically significant improvements. Clinical Relevance: Modified PSSEs, in addition to a treatment program, are beneficial for patients with SIS. Both modified cross-body and sleeper stretches are safe and efficacious for improving shoulder mobility, pain, and dysfunction.
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Anderson, Judy E., and Ashley C. Wozniak. "Satellite cell activation on fibers: modeling events in vivo — an invited review." Canadian Journal of Physiology and Pharmacology 82, no. 5 (May 1, 2004): 300–310. http://dx.doi.org/10.1139/y04-020.
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Knowledge of the events underlying satellite cell activation and the counterpart maintenance of quiescence is essential for planning therapies that will promote the growth and regeneration of skeletal muscle in healthy, disease and aging. By modeling those events of satellite cell activation in studies of single muscle fibers or muscles in culture, the roles of mechanical stretching and nitric oxide are becoming understood. Recent studies demonstrated that stretch-induced activation is very rapid and exhibits some features of satellite cell heterogeneity. As well, gene expression studies showed that expression of the c-met receptor gene rises rapidly after stretching muscles in culture compared to those without stretch. This change in gene expression during activation, and the maintenance of quiescence in both normal and dystrophic muscles are dependent on NO, as they are blocked by inhibition of nitric oxide synthase (NOS). Mechanical, contractile activity is the defining feature of muscle function. Therefore, ongoing studies of stretch effects in satellite cell activation and quiescence in quiescent fiber and muscle cultures provides appropriate models by which to explore the regulatory steps in muscle in vivo under many conditions related to disease, repair, rehabilitation, growth and the prevention or treatment of atrophy.Key words: regeneration, stretch, myofiber culture, muscular dystrophy, quiescence.
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Coburn, R. F. "Stretch-induced membrane depolarization in ferret trachealis smooth muscle cells." Journal of Applied Physiology 62, no. 6 (June 1, 1987): 2320–25. http://dx.doi.org/10.1152/jappl.1987.62.6.2320.
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We determined the effects of increasing the length of the ferret trachealis muscle on smooth muscle membrane potentials recorded on successive impalements by microelectrodes. The preparation included the paratracheal ganglion nerve plexus as well as trachealis muscle. With sustained increases in muscle length over the range 0.5–0.8 to 1.2 maximal length (Lmax), depolarization occurred, which was related to the amplitude of the length increase. Membrane depolarizations were also evoked after stretching to lengths approximately 1.1 Lmax and returning to the control length. Stretch-induced membrane depolarizations developed after the stretch maneuver was complete; were slowly reversible; were not influenced by tetrodotoxin or atropine; were related to stretch rather than to maintained increase in muscle length; were not transmitted to adjacent nonstretched segments of the trachea; and were often associated with slow waves which appear to be secondary to membrane depolarization rather than stretch per se.
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Letnar, Bernarda. "STRENGTHENING AND STABILIZATION EXERCISES IN PREVENTION OF SHOULDER INJURIES." Sportlogia 16, no. 1 (December 17, 2020): 149–60. http://dx.doi.org/10.5550/sgia.201601.en.bl.
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The shoulder joint is the most flexible joint in the human body which experiences high loads during certain sport activities involving overhead motion. Overhead athletes experience rapid shoulder elevation, abduction and external rotation during the movement and rapid deceleration after the movement, making them susceptible to shoulder injuries. Due to the extreme ranges of motion, overhead athletes tend to develop increased external rotation, combined with decreased range of internal rotation, emphasizing the need for balanced shoulder care program in the training process to prevent such occurrences. The aim of the research paper was to develop training regimen for injury prevention and shoulder maintenance that can be incorporated in daily training activities of the athletes in order to decrease the occurrence of injuries. Three part training program was designed consisting of specific warm up, strengthening and stabilization exercises and stretching exercises. The aim of the specific warm up was to prepare the shoulder for the training loads, mimicking the overhead movements and stimulating the stabilization in the joint. Strengthening and stabilization exercises aimed to strengthen external rotators in the shoulder and improve the stabilization of the shoulder joint by targeting specific muscles such as serratus anterior. The focus of stretching exercises was to stretch internal rotation muscles, which experience high loads in the overhead athlete's training. An effective training program that can be performed with minimal equipment and in a short time frame was designed to enable its simple incorporation into the daily training of overhead athletes.
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Ovize, M., R. A. Kloner, and K. Przyklenk. "Stretch preconditions canine myocardium." American Journal of Physiology-Heart and Circulatory Physiology 266, no. 1 (January 1, 1994): H137—H146. http://dx.doi.org/10.1152/ajpheart.1994.266.1.h137.
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Preconditioning is believed to be directly triggered by brief ischemia-reperfusion. However, brief ischemia results in transient dilation (or stretching) of the heart. We therefore sought to determine whether stretch per se, induced by rapid volume overload instead of brief coronary occlusion, could precondition the heart via stretch-activated ion channels. Forty-two anesthetized dogs underwent 1 h of coronary artery occlusion followed by 4.5 h of reperfusion. Before this, each dog underwent either no intervention (control) or acute volume overload. In three additional groups, Gd3+, a potent blocker of stretch-activated channels was injected as a bolus into the left atrium of each dog at the onset of the treatment period. Then the dogs underwent either acute volume overload, a 5-min episode of coronary occlusion followed by 10 min of reperfusion, or no intervention. Myocardial stretch significantly reduced infarct size after a subsequent 60-min ischemic insult. Protection afforded by stretch was completely prevented by Gd3+. Reduction in infarct size afforded by ischemic preconditioning was partially reversed by Gd3+. Gd3+ per se did not, however, alter the extent of necrosis. The present study suggests that myocardial stretch per se can precondition the canine heart, probably by activation of stretch-activated ion channels.
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Kubo, Yusuke, Bernd Hoffmann, Katja Goltz, Uwe Schnakenberg, Holger Jahr, Rudolf Merkel, Gundula Schulze-Tanzil, Thomas Pufe, and Mersedeh Tohidnezhad. "Different Frequency of Cyclic Tensile Strain Relates to Anabolic/Catabolic Conditions Consistent with Immunohistochemical Staining Intensity in Tenocytes." International Journal of Molecular Sciences 21, no. 3 (February 6, 2020): 1082. http://dx.doi.org/10.3390/ijms21031082.
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Tenocytes are mechanosensitive cells intimately adapting their expression profile and hence, their phenotype to their respective mechanomilieu. The immunolocalization and expression intensity of tenogenic, anabolic and catabolic markers in tenocytes in response to in vitro mechanical loading have not been monitored by immunohistochemical staining (IHC). Thus, we investigated the association between IHC intensities, different stimulation frequencies, and tenogenic metabolism using a versatile mechanical stretcher. Primary tenocytes obtained from murine Achilles tendons were transferred to poly(dimethylsiloxane) (PDMS) elastomeric chamber. Chambers were cyclically stretched by 5% in uniaxial direction at a variation of tensile frequency (1 or 2 Hz) for 3 h. After stretching, cell physiology, IHC intensities of tendon-related markers, and protein level of the angiogenesis marker vascular endothelial growth factor (VEGF) were evaluated. Cell proliferation in tenocytes stimulated with 1 Hz stretch was significantly higher than with 2 Hz or without stretch, while 2 Hz stretch induced significantly reduced cell viability and proliferation with microscopically detectable apoptotic cell changes. The amount of scleraxis translocated into the nuclei and tenomodulin immunoreactivity of tenocytes treated with stretch were significantly higher than of non-stretched cells. The collagen type-1 expression level in tenocytes stretched at 1 Hz was significantly higher than in those cultivated with 2 Hz or without stretching, whereas the matrix metalloproteinase (MMP)-1 and MMP-13 immunoreactivities of cells stretched at 2 Hz were significantly higher than in those stimulated with 1 Hz or without stretching. The secreted VEGF-protein level of tenocytes stretched at 2 Hz was significantly higher than without stretching. Our IHC findings consistent with cell physiology suggest that appropriate stretching can reproduce in vitro short-term tenogenic anabolic/catabolic conditions and allow us to identify an anabolic stretching profile.
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Oldenhof, Alexandra D., Oksana P. Shynlova, Mingyao Liu, B. Lowell Langille, and Stephen J. Lye. "Mitogen-activated protein kinases mediate stretch-induced c-fos mRNA expression in myometrial smooth muscle cells." American Journal of Physiology-Cell Physiology 283, no. 5 (November 1, 2002): C1530—C1539. http://dx.doi.org/10.1152/ajpcell.00607.2001.
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Evidence indicates that stretch of the uterus imposed by the growing fetus contributes to the onset of labor. Previously we have shown that mechanically stretching rat myometrial smooth muscle cells (SMCs) induces c- fos expression. To investigate this stretch-induced signaling, we examined the involvement of the mitogen-activated protein kinase (MAPK) family. We show that stretching rat myometrial SMCs induces a rapid and transient phosphorylation (activation) of MAPKs: extracellular signal-regulated protein kinase (ERK), c-Jun NH2-terminal kinase (JNK), and p38. The use of selective inhibitors for the ERK pathway (PD-98059 and U-0126), p38 (SB-203580), and JNK pathway (curcumin) demonstrated that activation of all three MAPK signaling pathways was necessary for optimal stretch-induced c- fos expression. We also demonstrate that upstream tyrosine kinase activity is involved in the mechanotransduction pathway leading to stretch-induced MAPK activation and c- fos mRNA expression. To further examine the role of MAPKs in vivo, we used a unilaterally pregnant rat model. MAPKs (ERK and p38) are expressed in the pregnant rat myometrium with maximal ERK and p38 phosphorylation occurring in the 24 h immediately preceding labor. Importantly, the rise in MAPK phosphorylation was confined to the gravid horn and was absent in the empty uterine horn, suggesting that mechanical strain imposed by the growing fetus controls MAPK activation in the myometrium. Collectively, this data indicate that mechanical stretch modulates MAPK activity in the myometrium leading to c- fos expression.
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Frigon, Alain, Michael D. Johnson, and C. J. Heckman. "Altered activation patterns by triceps surae stretch reflex pathways in acute and chronic spinal cord injury." Journal of Neurophysiology 106, no. 4 (October 2011): 1669–78. http://dx.doi.org/10.1152/jn.00504.2011.
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Spinal reflexes are modified by spinal cord injury (SCI) due the loss of excitatory inputs from supraspinal structures and changes within the spinal cord. The stretch reflex is one of the simplest pathways of the central nervous system and was used presently to evaluate how inputs from primary and secondary muscle spindles interact with spinal circuits before and after spinal transection (i.e., spinalization) in 12 adult decerebrate cats. Seven cats were spinalized and allowed to recover for 1 mo (i.e., chronic spinal state), whereas 5 cats were evaluated before (i.e., intact state) and after acute spinalization (i.e., acute spinal state). Stretch reflexes were evoked by stretching the left triceps surae (TS) muscles. The force evoked by TS muscles was recorded along with the activity of several hindlimb muscles. Stretch reflexes were abolished in the acute spinal state due to an inability to activate TS muscles, such as soleus (Sol) and lateral gastrocnemius (LG). In chronic spinal cats, reflex force had partly recovered but Sol and LG activity remained considerably depressed, despite the fact that injecting clonidine could recruit these muscles during locomotor-like activity. In contrast, other muscles not recruited in the intact state, most notably semitendinosus and sartorius, were strongly activated by stretching TS muscles in chronic spinal cats. Therefore, stretch reflex pathways from TS muscles to multiple hindlimb muscles undergo functional reorganization following spinalization, both acute and chronic. Altered activation patterns by stretch reflex pathways could explain some sensorimotor deficits observed during locomotion and postural corrections after SCI.
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Kubo, Keitaro, Hiroaki Kanehisa, and Tetsuo Fukunaga. "Effect of stretching training on the viscoelastic properties of human tendon structures in vivo." Journal of Applied Physiology 92, no. 2 (February 1, 2002): 595–601. http://dx.doi.org/10.1152/japplphysiol.00658.2001.
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The purpose of this study was to examine whether stretching training altered the viscoelastic properties of human tendon structures in vivo. Eight men performed the stretching training for 3 wk. Before and after the stretching training, the elongation of the tendon and aponeurosis of medial gastrocnemius muscle was directly measured by ultrasonography while the subjects performed ramp isometric plantar flexion up to the voluntary maximum, followed by a ramp relaxation. The relationship between the estimated muscle force (Fm) and tendon elongation ( L) during the ascending phase was fitted to a linear regression, the slope of which was defined as stiffness of tendon structures. The percentage of the area within the Fm- L loop to the area beneath the curve during ascending phase was calculated as an index representing hysteresis. To assess the flexibility, the passive torque of the plantar flexor muscles was measured during the passive stretch from 0° (anatomic position) to 25° of dorsiflexion with a constant velocity of 5°/s. The slope of the linear portion of the passive torque-angle curve during stretching was defined as flexibility index. Flexibility index decreased significantly after stretching training (−13.4 ± 4.6%). On the other hand, the stretching training produced no significant change in stiffness but significantly decreased hysteresis from 19.9 ± 11.7 to 12.5 ± 9.5%. The present results suggested that stretching training affected the viscosity of tendon structures but not the elasticity.
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Gordon, A. M., and E. B. Ridgway. "Stretch of active muscle during the declining phase of the calcium transient produces biphasic changes in calcium binding to the activating sites." Journal of General Physiology 96, no. 5 (November 1, 1990): 1013–35. http://dx.doi.org/10.1085/jgp.96.5.1013.
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In voltage-clamped barnacle single muscle fibers, muscle shortening during the declining phase of the calcium transient increases myoplasmic calcium. This extra calcium is probably released from the activating sites by a change in affinity when cross-bridges break (Gordon, A. M., and E. B. Ridgway, 1987. J. Gen. Physiol. 90:321-340). Stretching the muscle at similar times causes a more complex response, a rapid increase in intracellular calcium followed by a transient decrease. The amplitudes of both phases increase with the rate and amplitude of stretch. The rapid increase, however, appears only when the muscle is stretched more than approximately 0.4%. This is above the length change that produces the breakpoint in the force record during a ramp stretch. This positive phase in response to large stretches is similar to that seen on equivalent shortening at the same point in the contraction. For stretches at different times during the calcium transient, the peak amplitude of the positive phase has a time course that is delayed relative to the calcium transient, while the peak decrease during the negative phase has an earlier time course that is more similar to the calcium transient. The amplitudes of both phases increase with increasing strength of stimulation and consequent force. When the initial muscle the active force. A large decrease in length (which drops the active force to zero) decreases the extra calcium seen on a subsequent restretch. After such a shortening step, the extra calcium on stretch recovers (50 ms half time) toward the control level with the same time course as the redeveloped force. Conversely, stretching an active fiber decreases the extra calcium on a subsequent shortening step that is imposed shortly afterward. Enhanced calcium binding due to increased length alone cannot explain our data. We hypothesize that the calcium affinity of the activating sites increases with cross-bridge attachment and further with cross-bridge strain. This accounts for the biphasic response to stretch as follows: cross-bridges detached by stretch first decrease calcium affinity, then upon reattachment increase calcium affinity due to the strained configuration brought on by the stretch. The experiments suggest that cross-bridge attachment and strain can modify calcium binding to the activating sites in intact muscle.
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Cornelius, William L., Randall L. Jensen, and Michael E. Odell. "Effects of PNF Stretching Phases on Acute Arterial Blood Pressure." Canadian Journal of Applied Physiology 20, no. 2 (June 1, 1995): 222–29. http://dx.doi.org/10.1139/h95-016.
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This study examined acute systolic (SBP) and diastolic (DBP) blood pressure responses within passive and modified proprioceptive neuromuscular facilitation (PNF) stretching techniques. Nonhypertensives (N = 60) were assigned to one of three treatment groups. Group 1 employed an antagonist passive stretch (APS), 6-sec maximal voluntary isometric contraction (MVIC) of the antagonist, and subsequent APS. Group 2 employed an APS, a 6-sec MVIC of the antagonist, submaximal concentric contraction of the agonist, and APS. Group 3 was similar to Group 2, with the deletion of an MVIC prior to the concentric contraction. Blood pressures were obtained during rest, baseline following passive stretch, and at the end of the three phases of the PNF technique. Range of motion (ROM) data were collected for baseline and treatment in terminal hip flexion for each group. All PNF treatments were effective for increasing ROM. One or two trials of PNF improve ROM and avoid increasing SBP, while a third trial increases SBP. Key words: flexibility, nonhypertensives, pressor response, range of motion
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Dassow, C., L. Wiechert, C. Martin, S. Schumann, G. Müller-Newen, O. Pack, J. Guttmann, W. A. Wall, and S. Uhlig. "Biaxial distension of precision-cut lung slices." Journal of Applied Physiology 108, no. 3 (March 2010): 713–21. http://dx.doi.org/10.1152/japplphysiol.00229.2009.
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The mechanical forces acting on lung parenchyma during (mechanical) ventilation and its (patho)physiological consequences are currently under intense scrutiny. Several in vivo and cell culture models have been developed to study the pulmonary responses to mechanical stretch. While providing extremely useful information, these models do also suffer from limitations in being either too complex for detailed mechanical or mechanistic studies, or in being devoid of the full complexity present in vivo (e.g., different cell types and interstitial matrix). Therefore in the present study it was our aim to develop a new model, based on the biaxial stretching of precision-cut lung slices (PCLS). Single PCLS were mounted on a thin and flexible carrier membrane of polydimethylsiloxane (PDMS) in a bioreactor, and the membrane was stretched by applying varying pressures under static conditions. Distension of the membrane-PCLS construct was modeled via finite element simulation. According to this analysis, lung tissue was stretched by up to 38% in the latitudinal and by up to 44% in the longitudinal direction, resulting in alveolar distension similar to what has been described in intact lungs. Stretch for 5 min led to increased cellular calcium levels. Lung slices were stretched dynamically with a frequency of 15/min for 4 h without causing cell injury {3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide (MTT) test; live/dead straining}. These findings suggest that stretching of PCLS on PDMS-membranes may represent a useful model to investigate lung stretch in intact lung tissue in vitro for several hours.
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Syme, Douglas A., and Michael J. Grattan. "Effects of stretch on work from fast and slow muscles of mice: damped and undamped energy release." Canadian Journal of Physiology and Pharmacology 80, no. 9 (September 1, 2002): 887–900. http://dx.doi.org/10.1139/y02-110.
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Stretching active muscle increases the work performed during subsequent shortening. The effects of a preceding stretch on work done by the undamped or lightly damped series compliance (SC) and by the contractile component (CC), which includes cross bridges and damped elements, were assessed using mouse soleus (slow) and extensor digitorum longus (fast) muscles with limited tendon. Increasing stretch amplitude (010% fibre length) increased work done by the SC up to a limit, but did not effect work done by the CC. Increasing stretch velocity (10100% Vmax) had almost no effect on work done by either component. Increasing the delay between the end of stretch and onset of shortening (060 ms) caused a decrease in SC work, with no effect on CC work. Recoil of the SC was responsible for 5070% of the total work done during shortening after stretch. Usually only 1040% of the energy imparted during the stretch was recovered as work during subsequent shortening; large stretches and long delays between stretch and shortening further reduced this recovery by one third to one fifth. Results are interpreted in the context of a loss of energy stored in the SC owing to forcible detachment of cross bridges with large stretches and cyclic detachment with long delays.Key words: compliance, stretch, work, muscle, undamped.
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Sá, Marcos A., Gabriel R. Neto, Pablo B. Costa, Thiago M. Gomes, Cláudio M. Bentes, Amanda F. Brown, and Jefferson S. Novaes. "Acute Effects of Different Stretching Techniques on the Number of Repetitions in A Single Lower Body Resistance Training Session." Journal of Human Kinetics 45, no. 1 (March 1, 2015): 177–85. http://dx.doi.org/10.1515/hukin-2015-0018.
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Abstract This study aimed to investigate the acute effects of passive static and ballistic stretching on maximal repetition performance during a resistance training session (RTS). Nine male subjects underwent three experimental conditions: ballistic stretching (BS); passive static stretching (PSS); and a specific warm-up (SW). The RTS was composed of three sets of 12RM for the following exercises: leg press 45 (LP), leg extension (LE), leg curl (LC), and plantar flexors (PF). Performance of six sessions was assessed 48 hours apart. The first visit consisted of a familiarization session including stretching methods and exercises used in the RTS. On the second and third visit, a strength test and retest were performed. During the fourth to the sixth visit, the volunteers randomly performed the following protocols: BS+RTS; PSS+RTS; or SW+RTS. For the sum of the RM number of each three-set exercise, significant differences were found between PSS vs. SW for the LP (p = 0.001); LE (p = 0.005); MF (p = 0.001); and PF (p = 0.038). For the comparison between the methods of stretching PSS vs. BS, significant differences were found only for the FP (p = 0.019). When analyzing the method of stretching BS vs. SW, significant differences were found for the LP (p = 0.014) and MF (p = 0.002). For the total sum of the RM number of three sets of the four exercises that composed the RTS, significant differences were observed (p < 0.05) in the following comparisons: PPS vs. SW (p = 0.001), PPS vs. BS (p = 0.008), and BS vs. SW (p = 0.002). Accordingly, the methods of passive static and ballistic stretching should not be recommended before a RTS.
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Matsukawa, Kanji, and Tomoko Nakamoto. "Muscle mechanosensitive reflex is suppressed in the conscious condition: effect of anesthesia." Journal of Applied Physiology 104, no. 1 (January 2008): 82–87. http://dx.doi.org/10.1152/japplphysiol.00938.2007.
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To test the hypothesis that a muscle mechanosensitive reflex is suppressed in the conscious condition, we examined the effect of anesthesia on the cardiovascular responses to passive mechanical stretch of the hindlimb triceps surae muscle in six conscious cats. The triceps surae muscle was manually stretched for 30 s by extending the hip and knee joints and subsequently by dorsiflexing the ankle joint; the lateral gastrocnemius muscle was lengthened by 19 ± 2.6 mm. Heart rate (HR) and mean arterial blood pressure (MAP) did not change significantly during passive stretch of the muscle in the conscious condition. At 10–40 min after intravenously administering pentobarbital sodium (20–25 mg/kg), the identical passive stretch of the triceps surae muscle was able to induce the cardiovascular responses; HR and MAP were increased by 14 ± 1.3 beats/min and 14 ± 1.4 mmHg, respectively, and the cardiovascular responses were sustained throughout the passive stretch. In contrast, stretching skin on the triceps surae muscle evoked no significant changes in HR and MAP in the anesthetized condition. When anesthesia became light 40–90 min after injection of pentobarbital and the animals started to show spontaneous body movement, the cardiovascular response to passive muscle stretch tended to be blunted again. It is therefore concluded that passive mechanical stretch of skeletal muscle is capable of evoking the reflex cardiovascular response, which is suppressed in the conscious condition but exaggerated by anesthesia.
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Inoue, Nobutaka, Seinosuke Kawashima, Ken-Ichi Hirata, Yoshiyuki Rikitake, Saori Takeshita, Wataru Yamochi, Hozuka Akita, and Mitsuhiro Yokoyama. "Stretch force on vascular smooth muscle cells enhances oxidation of LDL via superoxide production." American Journal of Physiology-Heart and Circulatory Physiology 274, no. 6 (June 1, 1998): H1928—H1932. http://dx.doi.org/10.1152/ajpheart.1998.274.6.h1928.
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Hemodynamic forces on vasculature profoundly influence atherogenesis. We examined the effect of stretch force on the oxidation of low-density lipoprotein (LDL) by rat aortic smooth muscle cells (RASM) and superoxide production. Stretch force was imposed on RASM cultured on deformable dishes by stretching the dishes. Incubation of native LDL with static RASM for 24 h resulted in LDL oxidation as indicated by increases in thiobarbituric acid-reacting substances from 9.5 ± 2.3 to 24.5 ± 2.3 nmol malondialdehyde/mg. Stretch force on RASM augmented cell-mediated LDL oxidation to 149.3 ± 17.1% concomitantly with increase in superoxide production. LDL oxidation was inhibited by superoxide dismutase or depletion of the metal ion in the culture medium, indicating that it was a metal ion-dependent and superoxide-mediated process. The enhancement of LDL oxidation by stretch force was inhibited by diphenyliodonium, indicating the involvement of the NADH/NADPH oxidase system. Our findings suggest that the increased oxidant stress induced by stretch force is one of the potential mechanisms whereby hypertension facilitates atherosclerosis.
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Behm, David G., Sebastian Plewe, Philip Grage, Alireza Rabbani, Hamid Taghi Beigi, Jeannette M. Byrne, and Duane C. Button. "Relative static stretch-induced impairments and dynamic stretch-induced enhancements are similar in young and middle-aged men." Applied Physiology, Nutrition, and Metabolism 36, no. 6 (December 2011): 790–97. http://dx.doi.org/10.1139/h11-107.
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Middle-aged individuals may not respond in a similar manner as younger individuals. The study’s objective was to examine the effect of static (SS) and dynamic stretching (DS) in young and middle-aged men on subsequent performance. Ten young (22 ± 1.4 years) and 8 middle-aged men (46.3 ± 6.5 years) participated in 3 conditions consisting of SS (4 × 30 s for right and left quadriceps, hamstrings, and plantar flexors), DS (8 × 30 s of bilateral butt kicks, walking lunges, and plantar flexors) and control. Dependent variables included sit and reach, hip extension flexibility, countermovement jump (CMJ) height, drop jump (DJ) height, static balance, reaction (RT) and movement time (MT). Measurements were taken pre-intervention, post- and 10 min post-intervention. A 3-way repeated measurement ANOVA revealed that the younger men had higher jump heights, faster RT and MT, and greater flexibility than the middle-aged men. DS significantly enhanced DJ (p = 0.04) and CMJ (p = 0.006) height compared with SS and control conditions. SS (p < 0.0001) and DS (p = 0.004) post-intervention sit and reach scores were significantly greater than pre-intervention scores. There were no significant differences between the SS and DS sit and reach scores. CMJ heights were impaired (p = 0.04) by SS. Conversely, DS post-intervention jump heights were significantly (p < 0.0001) higher than SS post-, control post-, and control 10 min post-intervention. SS-induced impairments and DS-induced enhancements of CMJ height were not affected by age. DS provided similar improvements in sit and reach scores as SS. DS is recommended as the most appropriate stretching routine prior to work or athletic performance for younger and middle-aged men.
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Wang, Yongshun, Wei Cao, Jinjin Cui, Yang Yu, Yubo Zhao, Jian Shi, Jian Wu, Zhengyuan Xia, Bo Yu, and Jingjin Liu. "Arterial Wall Stress Induces Phenotypic Switching of Arterial Smooth Muscle Cells in Vascular Remodeling by Activating the YAP/TAZ Signaling Pathway." Cellular Physiology and Biochemistry 51, no. 2 (2018): 842–53. http://dx.doi.org/10.1159/000495376.
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Background/Aims: Increasing wall stress or biomechanical stretch experienced by arteries influences the initiation of atherosclerotic lesions. This initiation is mediated by Yes-associated protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ), which are both effectors of the Hippo pathway. In this study, the functional roles of YAP/TAZ proteins in the regulation of the stretch-mediated programing of human umbilical arterial smooth muscle cells (HUASMCs) to a proliferative phenotype were examined. Methods: HUASMCs were seeded on a Matrigel-coated silicone chamber and subjected to biomechanical stretch for 24 h after 48 h of growth. YAP/TAZ small interfering RNA was used to specifically knockdown YAP/ TAZ expression in HUASMCs. Results: We observed that YAP/TAZ activation via biomechanical stretching is involved in the regulation of critical aspects of the HUASMC phenotypic switch. YAP/TAZ knockdown significantly attenuated the stretch-induced proliferative and pro-inflammatory phenotypes in HUASMCs. Furthermore, treatment with atorvastatin, an anti-atherosclerotic drug, attenuated the stretch-induced phenotypic switch of HUASMCs from the contractile to synthetic state by suppressing YAP/TAZ expression. Additional investigations demonstrated the role of stretch in inhibiting the Hippo pathway, leading to the activation of PI3-kinase (PI3K) and phosphoinositide dependent kinase (PDK1); the key molecule for the regulation of the PDK1 and Hippo complex interaction was Sav1. These results showed the importance of YAP/TAZ activation, induced by biomechanical stretch, in promoting atheroprone phenotypes in HUASMCs. Conclusion: Taken together, our findings revealed a mechanism by which YAP/TAZ activation contributes to the pathogenesis of atherosclerosis.