The effects of static stretching programs on muscle strength and muscle architecture of the medial gastrocnemius.

INTRODUCTION: Static stretching (SS) program are widely used in clinical and athletic settings. Many previous studies investigate the effect of SS program on muscle strength and muscle architecture (muscle thickness, and pennation angleh). However, no consensus has been reached about the effect of SS programs on muscle strength and muscle architecture. The aim of this study was to investigate the effects of 6-week SS programs performed at different weekly frequencies on muscle strength, muscle thickness and pennation angle at different ankle joint positions. METHODS: A total of 24 healthy male volunteers were performed 6-week SS programs (2,160 s of SS: 360 s/week*6 weeks) and were randomized to a group that performed SS once a week, or a group that performed SS three times per week. Total time under stretching was equated between groups. The muscle strength (maximum voluntary isometric contraction) at three different ankle joints were assessed before and after the 6-week SS program. In addition, muscle thickness and pennation angle were assessed by ultrasonography before and after 6-week SS program. RESULTS: There were no significant changes in all variables before and after the 6-week SS program, regardless of weekly frequency (p > 0.05). CONCLUSIONS: Our results suggest that 6-week SS programs do not increase muscle strength or muscle architecture at different ankle joint positions, regardless of stretching frequency; however, no negative effect on these outcomes was observed, contrary to evidence on the immediate, detrimental effects of SS.

[Stretching and chylothorax]. / Stretching et chylothorax.

INTRODUCTION: Chylothorax is a rare cause of pleural effusion. The most common causes are iatrogenic or medical. We report an unusual and rare cause of bilateral chylothorax. CASE REPORT: A 73-year-old woman with no past history was admitted to the emergency department for sudden onset of dyspnoea. Chest X-ray and thoracic CT scan revealed large bilateral pleural effusions. Analysis of the fluid revealed a chylothorax. The patient was treated by chest tube drainage and a fat free (medium chain triglyceride) diet. This led to drying up of the effusions and rapid discharge. Complementary imaging examinations with chest-abdomen-pelvis CT, PET CT and pelvic MRI did not reveal any underlying cause. The final diagnosis was bilateral traumatic chylothorax caused by tearing of the thoracic duct during stretching exercises. CONCLUSION: Following a literature review, similar cases with the same clinical presentation were found. Combined treatment with thoracic drainage and medium chain triglyceride diet was effective in drying up the effusions. Our diagnosis was a diagnosis of exclusion. It is important to exclude a medical cause by thorough investigation.

Effective Timing of Curcumin Ingestion to Attenuate Eccentric Exercise-Induced Muscle Soreness in Men.

Curcumin is known to have potent anti-inflammatory effects. We have reported that acute curcumin ingestion attenuates eccentric exercise-induced muscle damage. This study aimed to examine the effect of curcumin ingestion timing (before or after exercise) on the changes in muscle damage markers after eccentric exercise. In this randomized, single-blind, parallel design study, 24 healthy young men performed 30 maximal isokinetic (120º/s) eccentric contractions of the elbow flexors using an isokinetic dynamometer. Subjects were randomly assigned to ingest 180 mg/d of oral curcumin either 7 d before (PRE) or 4 d after exercise (POST) or 180 mg/d of oral placebo 4 d after exercise (CON). The maximal voluntary contraction (MVC) torque of the elbow flexors, elbow joint range of motion (ROM), muscle soreness, and serum creatine kinase (CK) activity were measured before, immediately after, and 1-4 d after exercise. Changes in these variables were compared over time. In the POST group, ROM were higher at 3-4 d and muscle soreness was lower at 3 d after exercise compared with the CON group (p<0.05). However, in the PRE group, there were no significant differences compared with the CON group in changes in ROM and muscle soreness. Meanwhile, there were no significant differences among the groups in terms of changes in MVC torque and serum CK activity. Our results suggest that curcumin ingestion after exercise had a more beneficial effect in attenuating muscle soreness.

Nociceptor-dependent locomotor dysfunction after clinically-modeled hindlimb muscle stretching in adult rats with spinal cord injury.

In the course of investigating how common clinical treatments and adaptive technologies affect recovery after spinal cord injury (SCI), we discovered that a clinically-modeled hindlimb stretching protocol dramatically, but transiently, reduces locomotor function. Nociceptive sensory input is capable of altering motor output at the spinal level, and nociceptive neurons are sensitized after SCI. Here we tested the hypotheses that stretch-induced locomotor deficits are dependent on nociceptive afferents by depleting TRPV1+ sensory afferents using capsaicin injections in neonatal rats. Following maturation, animals received 25g-cm contusive SCI at T10. After plateau of locomotor recovery at 6 weeks, daily stretching was performed for 3 weeks, followed by 2 weeks without stretch, and again for two additional weeks. Animals were sacrificed 2 h after the last stretching session for histological assessments. Consistent with previous findings, stretch-induced drops in locomotor function were observed in nociceptor-intact animals but were nearly absent in nociceptor-depleted animals. These functional changes were accompanied by corresponding increases in the number of c-Fos+ nuclei throughout the lumbar enlargement. As expected, nociceptor-depleted animals had very little CGRP+ axonal innervation of the dorsal horn. Nociceptor-intact stretched animals had significantly higher levels of CGRP+ as compared to non-stretched SCI rats, suggesting that stretching promoted intraspinal CGRP+ sprouting. These results indicate that stretch-induced locomotor dysfunction in animals with incomplete SCI involves C-fibers, adding a negative post-SCI role to their adaptive roles (e.g., bladder control), and suggesting that the clinical use of muscle stretching to combat contractures and spasticity may be unintentionally detrimental to locomotor function.

Dynamic stretching alone can impair slower velocity isokinetic performance of young male handball players for at least 24 hours.

There are many adult studies reporting static stretch (SS)-induced deficits and dynamic stretch (DS) performance improvements shortly after the intervention. However, there is only a single study examining stretch-induced performance changes with youth at 24 hours' post-stretch. The objective of this study was to examine physiological responses of young trained athletes at 24-hours after experiencing SS or DS protocols. Eight young male, elite handball players (age: 16.1±5.1 years) were tested prior to-, 3-minutes and 24-hours following the three conditions (DS, SS, Control) in a randomized and counterbalanced order. Similar volumes of SS (2 repetitions of 75s for each leg) and DS (5 repetitions of 30s for each leg) involved one stretch each for the quadriceps and hamstrings. Tests included (i) two 4s maximal voluntary isometric contractions (MVC) at 60° of knee flexion with 2-min rest, (ii) two maximal isokinetic contractions each at 60°/sec and 300°/sec with 1-min rest, and (iii) two drop jumps with 30-sec rest. To simulate a full warm-up, dynamic activity including 5 minutes of aerobic cycling (70 rpm; 1 kilopond), 4 submaximal isometric contractions and 4 drop jumps were instituted before the pre-tests and following the interventions. Two-way repeated measures ANOVAs revealed that 1) both the SS and control conditions exhibited knee extensor 60°.s-1 (SS:-10.3%; p = 0.04, Control: -8.7%; p = 0.07) and 300°.s-1 (SS: -12.9%; p = 0.005, Control: -16.3%; p = 0.02) isokinetic deficits at post-test, 2) DS impaired knee flexor 60°.s-1 isokinetic work and power-related measures at post-test (Work: -10.1%; p = 0.0006; Power: -19.1%; p = 0.08) and at 24-hours' post-test (Work: 9.9%; p = 0.023; Power: -9.6%; p = 0.01), 3) DS (12.07% and 10.47%) and SS (13.7% and 14.6%) enhanced knee flexor 300°.s-1 isokinetic force and power-related measures compared to control. In conclusion, testing-induced knee extensor isokinetic impairments were counterbalanced by DS, however the hip flexion DS could have produced minor muscle damage for at least 24-hours decreasing knee flexor forces and power at 60°.s-1.

Caffeine, acute static stretching and maximum knee flexion strength.

BACKGROUND: Reductions in one-repetition maximum lifts (1RM) following static stretching can be attributed to enhanced neural inhibition, which can be reduced by using stimulants like caffeine. This study compared knee-flexion 1RM following either static stretching (SS) or no-stretching (NS), as well as after ingesting either caffeine (C) or placebo (P). METHODS: Twenty-four participants (12 female, 12 male) performed four random counterbalanced knee flexion 1RM tests. A 1RM test was performed for each condition at the same time of day with ~48 hours separating each test. Static stretching consisted of 5 exercises with the 1RM being performed immediately following the stretching. Caffeine dose was 6 mg/kg body weight, and the placebo was methylcellulose (520 mg). Both doses were administered as pills 60 minutes before the SS or NS procedures. RESULTS: Two-way repeated measures ANOVA showed a significant main effect for NS vs. SS (P<0.001, ηG2=0.23). The main effect for C vs. P, and the interaction between C vs. P and NS vs. SS were not statistically different. Average 1RMs were: CNS = 512±242 N, CSS = 474±241 N, PNS = 498±247 N, and PSS = 460±247 N. CONCLUSIONS: It is concluded that static stretching induced strength decrements are not removed by using stimulants at doses allowed by sport governing organizations.

Non-pharmacological interventions to combat exercise-induced muscle damage, a little natural tax on work out.

Debilitating pain, stiffness, tenderness, fatigue, impaired muscle function, lack of strength subsequent to exercise are not welcomed by those not accustomed to it. It may discourage an individual from participating in regular exercise. Numerou s ph armacological and non - pharmacological strategies have been used to alleviate symptoms of muscle soreness, muscle pain, improving muscle function, the range of motion and recovery time. Non-steroidal anti-inflammatory drugs are suggested to have a beneficial impact on muscle soreness, but fail to rejuvenate muscle weakness and range of motion coupled with muscle soreness. Furthermore, oral antiinflammatory drugs are widely used to mitigate muscle soreness symptoms, but chronic use can lead to different side effects in terms of peptic ulcer and liver toxicity. Non-pharmacological remedies and interventions can be a better choice. This narrative review is intended to provide insight into the non-pharmacological strategies to combat exercise-induced muscle damage.

Characterization of Prepractice Injury Prevention Exercises of High School Athletic Teams.

BACKGROUND: Static and dynamic exercises are performed before activity to decrease injury risk and increase performance. Although evidence supports using dynamic over static stretching and performing Fédération Internationale de Football Association (FIFA) 11+ as a dynamic prepractice routine, we do not know the frequency at which these exercises are utilized in high school populations. HYPOTHESIS: We hypothesize that there is a wide variety of preparticipation exercises performed by high school athletes, and that few high school teams perform FIFA 11+ as an injury prevention program in its entirety. STUDY DESIGN: Observational study. LEVEL OF EVIDENCE: Level 4. METHODS: High school prepractice routines were observed for 185 teams (football, soccer, basketball, and lacrosse) over 1 season. The percentages of team warm-up routines that included components of FIFA 11+ were calculated, and the chi-square test was used to compare sex, sport, and level of competition. RESULTS: Of a total 644 warm-up observations, 450 (69.9%) included only non-FIFA 11+ exercises, 56 (8.7%) included at least 1 FIFA 11+ exercise, and 38 (5.9%) included only jogging; 69 (10.6%) consisted only of sport-specific activities. The type of warm-up differed significantly between males and females ( P = 0.002), sports ( P < 0.001), and level of competition ( P < 0.001). Static stretching and athletes stretching on their own were observed in 14% and 15% of all observations. No team performed the FIFA 11+ injury prevention routine in its entirety. CONCLUSION: The type of warm-up differed by sex, sport, and level of competition. Static stretching was performed more frequently than anticipated, and an entire FIFA 11+ warm-up was never performed. CLINICAL RELEVANCE: We need to identify the exercises that decrease injury and increase performance and better inform the athletic population about the risks and benefits of static and dynamic warm-up programs.

Reliability of Sonographic Assessment of Biceps Femoris Distal Tendon Strain during Passive Stretching.

The purpose of this study was to determine the intra-rater, inter-examiner and inter-observer reliability of biceps femoris long head (BFlh) tendon strain using ultrasound imaging. Nineteen patients (age: 20.4 ± 0.35 y) were tested twice with a 1-wk interval. Each session included passive stretching from three different hip positions. Tests were performed independently by two examiners while BFlh tendon displacement (mm) and strain (%) were manually extracted from ultrasound video footages by two observers. Intra-rater comparisons revealed an intra-class correlation coefficient (ICC2,1) range of 0.87 to 0.98 and a variability less than 4.74%. Inter-examiner comparisons revealed an ICC2,1 range of 0.83 to 0.99 and less than 4.69% variability. Inter-observer ICCs ranged from 0.93 to 0.97 with variability less than 4.89%. Using a well-defined scanning protocol, two experienced examiners attained high levels of intra-rater agreement, with similarly excellent results for inter-rater and inter-observer reliability for BFlh tendon displacement and strain.

Acute effect of stretching one leg on regional arterial stiffness in young men.

PURPOSE: Our previous study demonstrated that a single bout of stretching exercises acutely reduced arterial stiffness. We hypothesized that this acute vascular response is due to regional mechanical stimulation of the peripheral arteries. To test this hypothesis, we examined the effect of a single bout of passive one leg stretching on arterial stiffness, comparing the stretched and the non-stretched leg in the same subject. METHODS: Twenty-five healthy young men (20.9 ± 0.3 years, 172.5 ± 1.4 cm, 64.1 ± 1.2 kg) volunteered for the study. Subjects underwent a passive calf stretching on one leg (six repetitions of 30-s static stretch with a 10-s recovery). Pulse wave velocity (PWV, an index of arterial stiffness), blood pressure (BP), and heart rate (HR) were measured before and immediately, 15, and 30 min after the stretching. RESULTS: Femoral-ankle PWV (faPWV) in the stretched leg was significantly decreased from baseline (835.0 ± 15.9 cm/s) to immediately (802.9 ± 16.8 cm/s, P < 0.01) and 15 min (810.5 ± 16.0 cm/s, P < 0.01) after the stretching, despite no changes in systolic and diastolic BP, or HR. However, faPWV in the non-stretched leg was not significantly altered at any time. Brachial-ankle PWV (baPWV) also showed similar responses with faPWV, but this response was not significant. Additionally, the passive stretching did not alter carotid-femoral PWV (cfPWV). CONCLUSIONS: These results suggest that mechanical stimulation to peripheral arteries as induced by static passive stretch may modulate arterial wall properties directly, rather than resulting in a systemic effect.

The acute benefits and risks of passive stretching to the point of pain.

PURPOSE: This study evaluated the acute effects of two different stretch intensities on muscle damage and extensibility. METHODS: Twenty-two physically active women (age 20 ± 1.0 years) were divided into two matched groups and undertook eight sets of 30-s passive hamstring stretching. One group stretched to the point of discomfort (POD) and the other to the point of pain (POP). Hamstring passive torque, sit and reach (S&R), straight leg raise (SLR), and markers of muscle damage were measured before, immediately after stretching and 24 h later. RESULTS: S&R acutely increased and was still increased at 24 h with median (interquartile range) of 2.0 cm (0.5-3.75 cm) and 2.0 cm (0.25-3.0 cm) for POP and POD (p < 0.05), respectively, with no difference between groups; similar changes were seen with SLR. Passive stiffness fully recovered by 24 h and there was no torque deficit. A small, but significant increase in muscle tenderness occurred at 24 h in both groups and there was a very small increase in thigh circumference in both groups which persisted at 24 h in POP. Plasma CK activity was not raised at 24 h. CONCLUSION: Stretching to the point of pain had no acute advantages over stretching to the discomfort point. Both forms of stretching resulted in very mild muscle tenderness but with no evidence of muscle damage. The increased ROM was not associated with changes in passive stiffness of the muscle but most likely resulted from increased tolerance of the discomfort.

Effect of the flexibility training performed immediately before resistance training on muscle hypertrophy, maximum strength and flexibility.

PURPOSE: It has been suggested that flexibility training may reduce the total volume of training during resistance trainings. The purpose of this study was to compare the effect of flexibility training immediately before resistance training (FLEX-RT) versus resistance training without flexibility training (RT) on maximum strength and the vastus lateralis muscle cross-sectional area (CSA). METHODS: Participants had each leg assigned to RT or FLEX-RT. Both groups performed four sets of leg extensions to voluntary failure of 80% of one repetition maximum (1RM); however, FLEX-RT performed two sets of 25 s of static stretching before resistance training. Number of repetitions and total volume were calculated during weeks 1-5 and 6-10. Vastus lateralis muscle CSA, 1RM, and flexibility were assessed at baseline and after 10 weeks. RESULTS: The number of repetitions and total training volume were greater for RT than FLEX-RT for weeks 1-5 and 6-10. Regarding the vastus lateralis muscle CSA, a main time effect was observed, however, greater change was observed for RT than FLEX-RT (12.7 and 7.4%, respectively). A main time effect for 1RM was also observed with similar changes for RT and FLEX-RT (12.7 and 12.9%, respectively). Flexibility was increased pre- to post-training for FLEX-RT with greater change for FLEX-RT (10.1%) than RT (2.1%). CONCLUSION: These results show that performing flexibility training immediately before resistance training can contribute to a lower number of repetitions, total volume, and muscle hypertrophy.

Dynamic "Range of Motion" Hindlimb Stretching Disrupts Locomotor Function in Rats with Moderate Subacute Spinal Cord Injuries.

Joint contractures and spasticity are two common secondary complications of a severe spinal cord injury (SCI), which can significantly reduce quality of life, and stretching is one of the top strategies for rehabilitation of these complications. We have previously shown that a daily static stretching protocol administered to rats at either acute or chronic time points after a moderate or moderate-severe T10 SCI significantly disrupts their hindlimb locomotor function. The objective of the current study was to examine the effects of dynamic range of motion (ROM) stretching on the locomotor function of rats with SCI as an alternative to static stretching. Starting at 6 weeks post-injury (T10 moderate contusion) eight adult Sprague-Dawley rats were subjected to hindlimb stretching for 4 weeks. Our standard stretching protocol (six maneuvers to stretch the major hindlimb muscle groups) was modified from 1 min static stretch-and-hold at the end ROM of each stretch position to a dynamic 2 sec hold, 1 sec release rhythm repeated for a duration of 1 min. Four weeks of daily (5 days/week) dynamic stretching led to significant disruption of locomotor function as assessed by the Basso, Beattie, Bresnahan (BBB) Open Field Locomotor Scale and three-dimensional (3D) kinematic and gait analyses. In addition, we identified and analyzed an apparently novel hindlimb response to dynamic stretch that resembles human clonus. The results of the current study extend the observation of the stretching phenomenon to a new modality of stretching that is also commonly used in SCI rehabilitation. Although mechanisms and clinical relevance still need to be established, our findings continue to raise concerns that stretching as a therapy can potentially hinder aspects of locomotor recovery.

Effect of participants' static stretching knowledge or deception on the responses to prolonged stretching.

Much of the static stretching (SS) literature reports performance impairments with prolonged SS. However, it has been acknowledged that a limitation of these studies is participants' knowledge or bias. Since many participants have knowledge of the literature, their performance may be subconsciously influenced by expectations. Hence, the objective of this study was to examine the effect of stretching knowledge or deception on subsequent force output following SS. Two groups of male participants who were either aware (BIASED: 14) or unaware (DECEPTION: 14) of the SS literature participated. Unaware participants were misinformed that SS increases force production. Testing involved maximal voluntary isometric contractions (MVC) of the quadriceps and hamstrings at pre-, post-, and 5 min post-intervention (three 30-s passive hamstring stretches to the point of discomfort with 30-s rest intervals) or control. While the DECEPTION group displayed impaired knee flexion force (p = 0.04; 3.6% and 10.4%) following hamstrings SS, there was no significant impairment with the BIASED (-1.1% and +0.9%) group. Both groups exhibited hamstrings F200 (force produced in the first 200 ms) impairments following SS. Whereas BIASED participants exhibited an overall decrease (p < 0.05; 1.8% and 4.2%) in knee extension MVC, DECEPTION participants showed (p = 0.005; 8.8% and 5.1%) force increases. The quadriceps F200 was not significantly affected with the BIASED group but overall there were 4.5% and 8.7% F200 impairments at 1 and 5 min post-intervention (p = 0.05) with the DECEPTION group. Thus while deception resulted in enhanced quadriceps muscle force output, there was no knowledge or deception advantage when stretching the hamstrings.

The effects of passive stretching plus vibration on strength and activation of the plantar flexors.

This study examined the effects of passive stretching only (PS+CON) and passive stretching with the addition of continuous vibration (VIB) during post-passive stretching tests (PS+VIB) on peak torque (PT), percent voluntary inactivation (%VI), single stimulus twitch torque (TTSINGLE), and doublet stimuli twitch torque (TTDOUBLET) of the plantar flexors at a short (20° plantar flexion (PF)) and long muscle length (15° dorsiflexion (DF)). Fourteen healthy men (age = 22 ± 3 years) performed isometric maximal voluntary contractions at PF and DF, and passive range of motion (PROM) assessments before and after 8 × 30-s passive stretches without (PS+CON) or with VIB (PS+VIB) administered continuously throughout post-passive stretching tests. The passive properties of the muscle tendon unit were assessed pre- and post-passive stretching via PROM, passive torque (PASSTQ), and musculotendinous stiffness (MTS) measurements. PT, TTSINGLE, and TTDOUBLET decreased, whereas, %VI increased following passive stretching at PF and DF (P < 0.05) with no significant differences between PS+CON and PS+VIB. PASSTQ and MTS decreased while PROM increased post-passive stretching during both trials (P < 0.05). The stretching-induced force/torque deficit and increases in %VI were evident following passive stretching at short and long muscle lengths. Although not statistically significant, effect size calculations suggested large and moderate differences in the absolute changes in PT (Cohen's d = 1.14) and %VI (Cohen's d = 0.54) from pre- to post-passive stretching between treatments, with PS+VIB having greater decreases of PT and higher %VI than PS+CON. The decrement in PT following passive stretching may be primarily neural in origin.

Ictus talámico secundario a disección vertebral tras la práctica de yoga / Thalamic stroke secondary to vertebral dissection after doing yoga

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Stretching the Spines of Gymnasts: A Review.

Gymnastics is noted for involving highly specialized strength, power, agility and flexibility. Flexibility is perhaps the single greatest discriminator of gymnastics from other sports. The extreme ranges of motion achieved by gymnasts require long periods of training, often occupying more than a decade. Gymnasts also start training at an early age (particularly female gymnasts), and the effect of gymnastics training on these young athletes is poorly understood. One of the concerns of many gymnastics professionals is the training of the spine in hyperextension-the ubiquitous 'arch' seen in many gymnastics positions and movements. Training in spine hyperextension usually begins in early childhood through performance of a skill known as a back-bend. Does practising a back-bend and other hyperextension exercises harm young gymnasts? Current information on spine stretching among gymnasts indicates that, within reason, spine stretching does not appear to be an unusual threat to gymnasts' health. However, the paucity of information demands that further study be undertaken.

NCAA strength and conditioning coach demographics, current practice trends and common injuries of athletes during strength and conditioning sessions.

BACKGROUND: NCAA strength and conditioning coaches are responsible for the day-to-day conditioning and strength training of collegiate athletes. NCAA regulations will likely require all strength and conditioning coaches to have a strength and conditioning certification. NCAA strength and conditioning coaches have varied philosophies on exercise programming based on educational background. The study aims to further evaluate the backgrounds and exercise philosophies of NCAA strength and conditioning coaches. METHODS: A survey (Survey Monkey®, Palo Alto, CA, USA) was distributed to NCAA strength and conditioning professionals to evaluate their education background, current practice trends, use of specific equipment and footwear, and what injuries occurred during sessions. RESULTS: Of the 208 survey participants, 77.9% were male with an average age of 34.5±9.1 years old. An exercise-related bachelor's degree was held by 80.4% and an exercise-related master's degree by 72.4%. Over 89% had a strength and conditioning certification. Having a master's, bachelor's, or type strength and conditioning certification had no difference in 1-repetition maximal practice with athletes. Lower extremity injuries made up the highest percentage (58.9%) of injuries seen by NCAA Strength and Conditioning Coaches than lumbar spine injuries (16.7%). The five most common injuries reported during workouts were lumbar strain (N.=431, 14.7%), hamstring strain (N.=332, 11.3%), ankle sprain (N.=299, 10.2%), patellar tendonitis (N.=232, 7.9%), and shin splints (N.=226, 7.7%). CONCLUSIONS: Collegiate education and certifications have impact on practice patterns of strength and conditioning coaches in the NCAA.

Intermittent stretching induces fibrosis in denervated rat muscle.

INTRODUCTION: Stretching (St) has been used for treating denervated muscles. However, its effectiveness and safety claims require further study. METHODS: Rats were divided into: (1) those with denervated (D) muscles, evaluated 7 or 15 days after sciatic nerve crush injury; (2) those with D muscles submitted to St during 7 or 15 days; and (3) those with normal muscles. Muscle fiber cross-sectional area, serial sarcomere number, sarcomere length, and connective tissue density were measured. MMP-2, MMP-9, TIMP-1, TGF-ß1, and myostatin mRNAs were determined by real-time polymerase chain reaction. MMP-2 and MMP-9 activity was evaluated by zymography. Collagen I was localized using immunofluorescence. RESULTS: St did not prevent muscle atrophy due to denervation, but it increased fibrosis and collagen I deposition at day 15. St also upregulated MMP-9 and TGF-ß1 gene expressions at day 7, and myostatin at day 15. CONCLUSIONS: Stretching denervated muscle does not prevent atrophy, but it increases fibrosis via temporal modulation of TGF-ß1/myostatin and MMP-9 cascades.