The effect of 30 minutes of passive stretch of the rat soleus muscle on the myogenic differentiation, myostatin, and atrogin-1 gene expressions

Local application of a transcutaneous carbon dioxide paste prevents excessive scarring and promotes muscle regeneration in a bupivacaine-induced rat model of muscle injury

In postoperative patients with head and neck cancer, scar tissue formation may interfere with the healing process, resulting in incomplete functional recovery and a reduced quality of life. Percutaneous application of carbon dioxide (CO₂ ) has been reported to improve hypoxia, stimulate angiogenesis, and promote fracture repair and muscle damage. However, gaseous CO₂ cannot be applied to the head and neck regions. Previously, we developed a paste that holds non-gaseous CO₂ in a carrier and can be administered transdermally. Here, we investigated whether this paste could prevent excessive scarring and promote muscle regeneration using a bupivacaine-induced rat model of muscle injury. Forty-eight Sprague Dawley rats were randomly assigned to either a control group or a CO₂ group. Both groups underwent surgery to induce muscle injury, but the control group received no treatment, whereas the CO₂ group received the CO₂ paste daily after surgery. Then, samples of the experimental sites were taken on days 3, 7, 14, and 21 post-surgery to examine the following: (1) inflammatory (interleukin [IL]-1β, IL-6), and transforming growth factor (TGF)-β and myogenic (MyoD and myogenin) gene expression by polymerase chain reaction, (2) muscle regeneration with haematoxylin and eosin staining, and (3) MyoD and myogenin protein expression using immunohistochemical staining. Rats in the CO₂ group showed higher MyoD and myogenin expression and lower IL-1β, IL-6, and TGF-β expression than the control rats. In addition, treated rats showed evidence of accelerated muscle regeneration. Our study demonstrated that the CO₂ paste prevents excessive scarring and accelerates muscle regeneration. This action may be exerted through the induction of an artificial Bohr effect, which leads to the upregulation of MyoD and myogenin, and the downregulation of IL-1β, IL-6, and TGF-β. The paste is inexpensive and non-invasive. Thus, it may be the treatment of choice for patients with muscle damage.

Effects of combined hip exercise and passive stretching on muscle stiffness, pain perception and painrelated disability, and physical function in older adults with low back pain

[Purpose] This study aimed to examine the effects of combined hip exercise and passive stretching as a novel treatment method for low back pain (LBP) in older adults.[Methods] Altogether, 20 Koreans with LBP aged 60–79 years (67.3 ± 5.92 years) were randomly assigned to undertake combined exercise (CE; n = 10) or lumbar stabilization exercise (LSE; n = 10). All participants performed their respective exercise program for 25–30 min with an OMNI scale of 6–8 for 8 weeks, three times a week. Body composition, muscle stiffness, pain-visual analog scale (P-VAS), Oswestry disability index, and physical function were evaluated before and after the exercise intervention.[Results] The CE group demonstrated greater improvements in lean body mass (<i>η²</i> = 0.402, <i>p</i> = 0.003) and percent body fat (<i>η²</i> = 0.222, <i>p</i> = 0.036) than the LSE group. Both groups demonstrated significant improvements in muscle stiffness, P-VAS scores, and Oswestry disability index scores, although no significant differences were observed between the interventions. All physical function parameters demonstrated a significant improvement in both groups, and the CE group demonstrated greater improvement in the YMCA sit-and-reach (<i>η²</i> = 0.338, <i>p</i> = 0.007) and straight leg raise tests (<i>η²</i> = 0.283, p = 0.016) than the LSE group.[Conclusion] CE is comparable to LSE as an effective and successful exercise intervention that reduces muscle stiffness and P-VAS scores. Moreover, CE is more effective than LSE in enhancing the physical function of older adults with LBP.

Morphometric and Molecular Muscle Remodeling after Passive Stretching in Elderly Female Rats

OBJECTIVES

To determine the effects of three sessions of a passive stretching exercise protocol on the muscles of elderly female rats.

METHODS

The effects of the stretching exercises on the soleus muscle were analyzed using immunohistochemistry [tissue inhibitors of matrix metalloproteinases (TIMP), the tumor necrosis factor-alpha (TNF-α), and the gene expression levels using real-time PCR of the transforming growth factor-beta 1 (TGF-β1), collagen type 1 (COL1), and collagen type 3 (COL3)]. Fifteen 26-month-old female Wistar rats were randomly divided into two groups, namely, Stretching (SG, n=8) and Control (CG, n=7). The passive mechanical stretching protocol consisted of a set of 4 1-minute repetitions, with 30 seconds between each repetition (total treatment of 4 minutes), three times a week for 1 week.

RESULTS

Immunohistochemical analysis revealed an increase of 71.4% in the TNF-α (p=0.04) gene expression levels for the SG and a 58% decrease in the TGF-β1 gene expression levels (p=0.005) in the SG compared to that in the CG. No significant differences were observed between the groups for the immunostaining of TIMP-1 or the gene expression levels of COL1 and COL3.

CONCLUSION

Three sessions of static stretching reduced the gene expression level of TGF-β1, which, owing to its anti-fibrotic role, might contribute to the remodeling of the intramuscular connective tissue of the aging muscle. In addition, immunostaining revealed that TNF-α levels increased in the aging muscle tissue in response to stretching, indicating its effect on stimulating extracellular matrix degradation. These outcomes have important clinical implications in reinforcing the use of stretching exercises in the elderly, considering that the aging muscle presents an infiltration of connective tissue.

Regulation of extracellular matrix elements and sarcomerogenesis in response to different periods of passive stretching in the soleus muscle of rats

Stretching is a common method used to prevent muscle shortening and improve limited mobility. However, the effect of different time periods on stretching-induced adaptation of the extracellular matrix and its regulatory elements have yet to be investigated. We aimed to evaluate the expression of fibrillar collagens, sarcomerogenesis, metalloproteinase (MMP) activity and gene expression of the extracellular matrix (ECM) regulators in the soleus (SOL) muscle of rats submitted to different stretching periods. The soleus muscles were submitted to 10 sets of passive stretching over 10 (St 10d) or 15 days (St 15d) (1 min per set, with 30 seconds' rest between sets). Sarcomerogenesis, muscle cross-sectional area (CSA), and MMP activity and mRNA levels in collagen (type I, III and IV), connective tissue growth factor (CTGF), growth factor-beta (TGF-β), and lysyl oxidase (LOX) were analyzed. Passive stretching over both time periods mitigated COL-I deposition in the SOL muscle of rats. Paradoxically, 10 days of passive stretching induced COL-I and COL-III synthesis, with concomitant upregulation of TGF-β1 and CTGF at a transcriptional level. These responses may be associated with lower LOX mRNA levels in SOL muscles submitted to 10 passive stretching sessions. Moreover, sarcomerogenesis was observed after 15 days of stretching, suggesting that stretching-induced muscle adaptations are time-dependent responses.

Endothelin-1 suppresses insulin-stimulated Akt phosphorylation and glucose uptake via GPCR kinase 2 in skeletal muscle cells

BACKGROUND AND PURPOSE

Endothelin-1 (ET-1) reduces insulin-stimulated glucose uptake in skeletal muscle, inducing insulin resistance. Here, we have determined the molecular mechanisms underlying negative regulation by ET-1 of insulin signalling.

EXPERIMENTAL APPROACH

We used the rat L6 skeletal muscle cells fully differentiated into myotubes. Changes in the phosphorylation of Akt was assessed by Western blotting. Effects of ET-1 on insulin-stimulated glucose uptake was assessed with [(3) H]-2-deoxy-d-glucose ([(3) H]2-DG). The C-terminus region of GPCR kinase 2 (GRK2-ct), a dominant negative GRK2, was overexpressed in L6 cells using adenovirus-mediated gene transfer. GRK2 expression was suppressed by transfection of the corresponding short-interfering RNA (siRNA).

KEY RESULTS

In L6 myotubes, insulin elicited sustained Akt phosphorylation at Thr(308) and Ser(473) , which was suppressed by ET-1. The inhibitory effects of ET-1 were prevented by treatment with a selective ETA receptor antagonist and a Gq protein inhibitor, overexpression of GRK2-ct and knockdown of GRK2. Insulin increased [(3) H]2-DG uptake rate in a concentration-dependent manner. ET-1 noncompetitively antagonized insulin-stimulated [(3) H]2-DG uptake. Blockade of ETA receptors, overexpression of GRK2-ct and knockdown of GRK2 prevented the ET-1-induced suppression of insulin-stimulated [(3) H]2-DG uptake. In L6 myotubes overexpressing FLAG-tagged GRK2, ET-1 facilitated the interaction of endogenous Akt with FLAG-GRK2.

CONCLUSIONS AND IMPLICATIONS

Activation of ETA receptors with ET-1 suppressed insulin-induced Akt phosphorylation at Thr(308) and Ser(473) and [(3) H]2-DG uptake in a GRK2-dependent manner in skeletal muscle cells. These findings suggest that ETA receptors and GRK2 are potential targets for overcoming insulin resistance.

Acute effects of stretching exercise on the soleus muscle of female aged rats

It has been shown that stretching exercises can improve the flexibility and independence of the elderly. However, although these exercises commonly constitute training programs, the morphological adaptations induced by stretching exercises in aged skeletal muscle are still unclear.

OBJECTIVE

To assess the acute effects of passive mechanical static stretching on the morphology, sarcomerogenesis and modulation of important components of the extracellular matrix of the soleus muscle of aged female rats.

METHODS

Fifteen old female rats with 26 months were divided into two groups: stretching (n=8, SG) and control (n=7, CG): The stretching protocol consisted of 4 repetitions each of 1 min with 30s interval between sets. Stretching was performed on the left soleus muscle, 3 times a week for 1 week. After three sessions, the rats were anesthetized to remove the left soleus muscle, and then euthanized. The following analyses were carried out: muscle fiber cross-sectional area and serial sarcomere number; immunohistochemistry for the quantification of collagen I, III and TGFβ-1.

RESULTS

a decrease in muscle fiber cross-sectional area of the SG was observed when compared to the CG (p=0.0001, Kruskal-Wallis); the percentage of type I collagen was significantly lower in the SG when compared to the CG (p=0.01, Kruskal-Wallis), as well as the percentage of TGFβ-1 (p=0.04, Kruskal-Wallis); collagen III was significantly higher in the SG than in the CG (7.06±6.88% vs 4.92±5.30%, p=0.01, Kruskal-Wallis).

CONCLUSION

Although the acute stretching induced muscle hypotrophy, an antifibrotic action was detected.

Gene therapy for inherited muscle diseases: where genetics meets rehabilitation medicine

The development of clinical vectors to correct genetic mutations that cause inherited myopathies and related disorders of skeletal muscle is advancing at an impressive rate. Adeno-associated virus vectors are attractive for clinical use because (1) adeno-associated viruses do not cause human disease and (2) these vectors are able to persist for years. New vectors are now becoming available as gene therapy delivery tools, and recent preclinical experiments have demonstrated the feasibility, safety, and efficacy of gene therapy with adeno-associated virus for long-term correction of muscle pathology and weakness in myotubularin-deficient canine and murine disease models. In this review, recent advances in the application of gene therapies to treat inherited muscle disorders are presented, including Duchenne muscular dystrophy and x-linked myotubular myopathy. Potential areas for therapeutic synergies between rehabilitation medicine and genetics are also discussed.

Skeletal muscle tissue engineering: methods to form skeletal myotubes and their applications

Skeletal muscle tissue engineering (SMTE) aims to repair or regenerate defective skeletal muscle tissue lost by traumatic injury, tumor ablation, or muscular disease. However, two decades after the introduction of SMTE, the engineering of functional skeletal muscle in the laboratory still remains a great challenge, and numerous techniques for growing functional muscle tissues are constantly being developed. This article reviews the recent findings regarding the methodology and various technical aspects of SMTE, including cell alignment and differentiation. We describe the structure and organization of muscle and discuss the methods for myoblast alignment cultured in vitro. To better understand muscle formation and to enhance the engineering of skeletal muscle, we also address the molecular basics of myogenesis and discuss different methods to induce myoblast differentiation into myotubes. We then provide an overview of different coculture systems involving skeletal muscle cells, and highlight major applications of engineered skeletal muscle tissues. Finally, potential challenges and future research directions for SMTE are outlined.

The effect of anabolic steroid administration on passive stretching-induced expression of mechano-growth factor in skeletal muscle

Background. Stretching of skeletal muscle induces expression of the genes which encode myogenic transcription factors or muscle contractile proteins and results in muscle growth. Anabolic steroids are reported to strengthen muscles. We have previously studied the effects of muscle stretching on gene expression. Here, we studied the effect of a combination of passive stretching and the administration of an anabolic steroid on mRNA expression of a muscle growth factor, insulin-like growth factor-I autocrine variant, or mechano-growth factor (MGF). Methods. Twelve 8-week-old male Wistar rats were used. Metenolone was administered and passive repetitive dorsiflexion and plantar flexion of the ankle joint performed under deep anesthesia. After 24 h, the gastrocnemius muscles were removed and the mRNA expression of insulin-like growth factor-I autocrine variant was measured using quantitative real-time polymerase chain reaction. Results. Repetitive stretching in combination with metenolone, but not stretching alone, significantly increased MGF mRNA expression. Conclusion. Anabolic steroids enhance the effect of passive stretching on MGF expression in skeletal muscle.

Passive repetitive stretching for a short duration within a week increases myogenic regulatory factors and myosin heavy chain mRNA in rats' skeletal muscles

Stretching is a stimulation of muscle growth. Stretching for hours or days has an effect on muscle hypertrophy. However, differences of continuous stretching and repetitive stretching to affect muscle growth are not well known. To clarify the difference of continuous and repetitive stretching within a short duration, we investigated the gene expression of muscle-related genes on stretched skeletal muscles. We used 8-week-old male Wistar rats (N = 28) for this study. Animals medial gastrocnemius muscle was stretched continuously or repetitively for 15 min daily and 4 times/week under anesthesia. After stretching, muscles were removed and total RNA was extracted. Then, reverse transcriptional quantitative real-time PCR was done to evaluate the mRNA expression of MyoD, myogenin, and embryonic myosin heavy chain (MyHC). Muscles, either stretched continuously or repetitively, increased mRNA expression of MyoD, myogenin, and embryonic MyHC more than unstretched muscles. Notably, repetitive stretching resulted in more substantial effects on embryonic MyHC gene expression than continuous stretching. In conclusion, passive stretching for a short duration within a week is effective in increasing myogenic factor expression, and repetitive stretching had more effects than continuous stretching for skeletal muscle on muscle growth. These findings are applicable in clinical muscle-strengthening therapy.

Low-level laser therapy (808 nm) contributes to muscle regeneration and prevents fibrosis in rat tibialis anterior muscle after cryolesion

Muscle regeneration is a complex phenomenon, involving replacement of damaged fibers by new muscle fibers. During this process, there is a tendency to form scar tissue or fibrosis by deposition of collagen that could be detrimental to muscle function. New therapies that could regulate fibrosis and favor muscle regeneration would be important for physical therapy. Low-level laser therapy (LLLT) has been studied for clinical treatment of skeletal muscle injuries and disorders, even though the molecular and cellular mechanisms have not yet been clarified. The aim of this study was to evaluate the effects of LLLT on molecular markers involved in muscle fibrosis and regeneration after cryolesion of the tibialis anterior (TA) muscle in rats. Sixty Wistar rats were randomly divided into three groups: control, injured TA muscle without LLLT, injured TA muscle treated with LLLT. The injured region was irradiated daily for four consecutive days, starting immediately after the lesion using an AlGaAs laser (808 nm, 30 mW, 180 J/cm(2); 3.8 W/cm(2), 1.4 J). The animals were sacrificed on the fourth day after injury. LLLT significantly reduced the lesion percentage area in the injured muscle (p<0.05), increased mRNA levels of the transcription factors MyoD and myogenin (p<0.01) and the pro-angiogenic vascular endothelial growth factor (p<0.01). Moreover, LLLT decreased the expression of the profibrotic transforming growth factor TGF-β mRNA (p<0.01) and reduced type I collagen deposition (p<0.01). These results suggest that LLLT could be an effective therapeutic approach for promoting skeletal muscle regeneration while preventing tissue fibrosis after muscle injury.

Could muscle deformity in children with spastic cerebral palsy be related to an impairment of muscle growth and altered adaptation?

Skeletal muscle deformity is common in children with spastic cerebral palsy (CP), but the underlying mechanisms are unclear. This review explores some possible factors which may influence the development of muscle deformity in CP. Normal muscle function and growth appear to depend on the interaction of neuronal, endocrinal, nutritional, and mechanical factors, and also on the development of an appropriate balance between muscle protein synthesis and degradation, and between the development of contractile and non-contractile components. In this context, the changes seen in muscle in children with CP are reviewed and discussed. It is suggested that the development of muscle deformity in children with CP may be related to a multifactorial impairment of muscle growth, on which adaptation of the extracellular matrix due to altered loading may be imposed.

Role of MyoD in denervated, disused, and exercised muscle

The myogenic regulatory factor MyoD plays an important role in embryonic and adult skeletal muscle growth. Even though it is best known as a marker for activated satellite cells, it is also expressed in myonuclei, and its expression can be induced by a variety of different conditions. Several model systems have been used to study the mechanisms behind MyoD regulation, such as exercise, stretch, disuse, and denervation. Since MyoD reacts in a highly muscle-specific manner, and its expression varies over time and between species, universally valid predictions and explanations for changes in MyoD expression are not possible. This review explores the complex role of MyoD in muscle plasticity by evaluating the induction of MyoD expression in the context of muscle composition and electrical and mechanical stimulation.

Interdisciplinary palliative care, including massage, in treatment of amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive fatal neurological disease that affects approximately 20,000 Americans. Symptoms include muscle weakness, fatigue, twitching, atrophy, spasticity, pain, oropharyngeal dysfunction, pseudobulbar affect, weight loss, and respiratory impairment. Death occurs within 3-5 yr after onset of symptoms, with diagnosis taking from 11 to 17.5 months. The only FDA-approved drug for ALS is Riluzole, which only increases the life expectancy by a few months. All other treatments for ALS provide symptom management to improve the patient's quality of life. An interdisciplinary palliative care team for the ALS patient helps to reduce the stress that the illness places on families. Massage can be a useful adjunctive treatment for spasticity and pain when medication side effects are unwanted. A holistic interdisciplinary palliative care team supports both the patient and the family improving their quality of life.

Mechano-sensitivity of normal and long term denervated soleus muscle of the rat

INTRODUCTION AND OBJECTIVES

Evidence showed that physical forces, as passive stretching or active contraction, may counteract various kinds of skeletal muscle atrophy due, for instance, to muscle immobilization, pathophysiology or denervation. Accordingly, active muscle contraction induced by functional electric stimulation is helpful to reduce the muscle atrophic state in denervated man. Moreover, there is evidence that also passive mechanical stimulation of the sarcolemnic membrane may reduce the atrophic muscle state. As to the mechanisms by which mechanical stimulation modulates muscle physiology and pathophysiology, there is a growing list of facts that signaling pathway to the nucleus involves stretch activated channels (SACs) of the sarcolemma and the cytoskeleton. SACs activation allowed a Ca(2+) inflow that activates Ca(2+)-dependent molecular signals. Cytoskeleton may be activated by Ca(2+)-dependent and -independent paths and its contraction and elongation represent not only a mechanical signal to the nucleus but also a stimulus for many molecular signals. The aim of this work was to evaluate in soleus muscle of the rat, the mechano-sensitivity of SACs before and after medium and long term denervation.

METHODS

Electrophysiologic experiments were made in normal and denervated Soleus muscle of Wistar rats. Currents were recorded in voltage clamp by intracellular microelectrodes inserted in a single fiber.

RESULTS

Our findings demonstrated that SACs were expressed in normal soleus muscle and that SAC currents were potentiated by muscle stretching. Another important result was that the sensitivity to stretching increased after denervation and was particularly evident in long term denervated muscles.

DISCUSSION

The reported effects are in agreement with the effects of exercise on inducing muscle hypertrophy or with the positive effects on repairing the atrophic state of skeletal muscles by mechanical stimulation or, in denervated humans, by the functional electrical stimulation (FES).

Morphological comparison of different protocols of skeletal muscle remobilization in rats after hindlimb suspension

The aim of this study was to evaluate and compare the efficacy of different remobilization protocols in different skeletal muscles considering the changes induced by hindlimb suspension of the tail. Thirty-six female Wistar rats were divided into six groups: control I, control II, suspended, suspended free, suspended trained on a declined treadmill and suspended trained on a flat treadmill. Fragments of soleus and tibialis anterior (TA) muscle were frozen and processed by different histochemical methods. The suspended soleus showed a significant increase in the proportional number of intermediate/hybrid fibers and a decrease in the number of type I fibers. Some of these changes proved to be reversible after remobilization. The three remobilization programs led to the recovery of both the proportional number of fibers and their size. The TA muscle presented a significant increase in the number and size of type I fibers and a cell size reduction of type IIB fibers, which were recovered after training on a declined treadmill and free movement. Especially regarding the soleus, the present findings indicate that, among the protocols, training on a declined treadmill was found to induce changes of a more regenerative nature, seemingly indicating a better tissue restructuring after the suspension procedure.

Morphological effects of two protocols of passive stretch over the immobilized rat soleus muscle

This study evaluated two different stretching protocols employed during a period of hind-limb immobilization in terms of their effects on muscle morphology. Quantitative data regarding the soleus muscle were obtained based on the clinical hypothesis that a high frequency of this exercise would improve the recovery of muscle structure. Twenty-four male Wistar rats were divided into four groups (n = 6 each): the control group (C); the immobilized group, in which the left hind limb was immobilized in order to maintain the soleus muscle in a fully shortened position for 3 weeks (I); the 'immobilized and stretched every 3 days' group, in which the left hind limb was immobilized as in the immobilized group, but with the soleus muscle stretched every 3 days for 40 min (Ist3); and the 'immobilized (as in the immobilized group) and stretched every 7 days' group (ISt7). All soleus muscles were excised 21 days after the beginning of the experiment, and were processed for (1) haematoxylin and eosin and myosin ATPase to evaluate muscle morphology and cross-sectional area and the proportions of the different fibre types, and (2) ultrastructural analysis. The cross-sectional area was found to have decreased in all fibre types (I, II and C), mainly in ISt7, when compared with the C group and ISt3 group. The proportion of the different fibre types did not show statistical difference between groups. Light and electron microscopy examination revealed signs of cell degeneration that was more intense in the group immobilized and stretched three times a week. In conclusion, sessions of passive stretching applied to the soleus during immobilization induce muscle fibre injury, suggesting that this therapeutic tool should be applied carefully to disused muscles.

Short bouts of stretching increase myo-D, myostatin and atrogin-1 in rat soleus muscle

Stretching is widely used in rehabilitation and sports activities to improve joint range-of-motion and flexibility in humans, but the effect of stretching on the gene expression of skeletal muscle is poorly understood. We evaluated the effect of short bouts of passive stretching of rat soleus muscle on myo-D, myostatin, and atrogin-1 gene expressions. Six groups of animals were submitted to a single session of stretching (10 stretches of 1 minute with 30 seconds of rest between them, performed manually) and were evaluated immediately (I), and 8, 24, 48, 72, and 168 hours after the session. To evaluate the effect of repetitive sessions of stretching on the soleus muscle over 1 week, three groups of animals received a single session per day of stretching and the muscle was evaluated immediately after 2, 3, and 7 sessions. The mRNA levels of myo-D, myostatin, and atrogin-1 were determined by real-time polymerase chain reaction. A single session of stretching increased the mRNA levels of myo-D (after 24 h), myostatin (I, and 168 h later), and atrogin-1 (after 48 h). Repeated daily session of stretching over 1 week increased myostatin (after 7 sessions) and atrogin-1 expression (after 2, 3, and 7 sessions). Thus, short bouts of passive stretching are able to increase the gene expression of factors associated with muscle growth (myo-D), negative regulation of muscle mass (myostatin), and atrophy (atrogin-1), indicating muscle remodeling through different pathways.

Electrical stimulation based on chronaxie reduces atrogin-1 and myoD gene expressions in denervated rat muscle

Denervation induces muscle fiber atrophy and changes in the gene expression rates of skeletal muscle. Electrical stimulation (ES) is a procedure generally used to treat denervated muscles in humans. This study evaluated the effect of ES based on chronaxie and rheobase on the expression of the myoD and atrogin-1 genes in denervated tibialis anterior (TA) muscle of Wistar rats. Five groups were examined: (1) denervated (D); (2) D+ES; (3) sham denervation; (4) normal (N); and (5) N+ES. Twenty muscle contractions were stimulated every 48 h using surface electrodes. After 28 days, ES significantly decreased the expression of myoD and atrogin-1 in D+ES compared to the D group. However, ES did not prevent muscle-fiber atrophy after denervation. Thus, ES based on chronaxie values and applied to denervated muscles using surface electrodes, as normally used in human rehabilitation, was able to reduce the myoD and atrogin-1 gene expressions, which are related to muscular growth and atrophy, respectively. The results of this study provide new information for the treatment of denervated skeletal muscle using surface ES.

Bouts of passive stretching after immobilization of the rat soleus muscle increase collagen macromolecular organization and muscle fiber area

This study evaluated the effect of short bouts of stretching on the soleus muscle after immobilization, by measuring the birefringence of the intramuscular connective tissue (ICT) and the muscle fiber area. Thirty rats were divided into five groups: the left soleus was immobilized in the shortened position; after immobilization the animals remained free; after immobilization, the soleus was stretched daily (10 stretches of 60 sec followed by 30 sec rest); after immobilization, the soleus was stretched 3 times a week; control. Immobilization caused a loss of birefringence of the ICT and of muscle fiber area and only daily stretching increased both compared with the control (p< 0.01). In conclusion, short daily bouts of stretching after immobilization induced molecular reorganization of the collagen bundles and muscle fiber hypertrophy in the rat soleus.