Sports-related Muscle Injuries Research Articles

A Novel Minimally Invasive Surgically Induced Skeletal Muscle Injury Model in Sheep.

Sports-related muscle injuries account for 10-55% of all injuries, which is a growing concern, especially given the aging world population. To evaluate the process of skeletal muscle injury and compare it with muscle lesions observed in humans, we developed a novel in vivo model in sheep. In this model, muscle injury was induced by an ultrasound-guided transverse biopsy at the myotendinous junction of the medial gastrocnemius muscle. Twelve male sheep were examined at 3, 7, 14, and 28 days post-injury. Histological, immunofluorescence, and MRI analyses indicate that our sheep model could resemble key human clinicopathological features. Statistically significant differences (p < 0.05) were observed in collagen I, dMHC, α-SMA, and CD68 immunohistochemical detection when comparing injured and healthy muscles. The injured gastrocnemius muscle exhibited elevated levels of type I collagen, infiltration of CD68(+) macrophages, angiogenesis, and the emergence of newly regenerated dMHC(+) myofibers, which persisted for up to 4 weeks post-injury. Similarly, the progression of muscle injury in the sheep model was assessed using advanced clinical 3 T MRI and compared with MRI scans from human patients. The data indicate that the sheep muscle injury model presents features similar to those observed in human skeletal muscle injuries. This makes it a valuable large animal model for studying muscle injuries and developing novel therapeutic strategies.

Imaging of muscle injuries in soccer.

Accurate diagnosis of muscle injuries is a challenge in everyday clinical practice and may have profound impact on the recovery and return-to-play decisions of professional athletes particularly in soccer. Imaging techniques such as ultrasound and magnetic resonance imaging (MRI), in addition to the medical history and clinical examination, make a significant contribution to the timely structural assessment of muscle injuries. The severity of a muscle injury determined by imaging findings has a decisive influence on therapy planning and affects prognosis. Imaging is of high importance when the diagnosis or grade of injury is unclear, when recovery is taking longer than expected, and when interventional or surgical management may be needed. This narrative review will discuss ultrasound and MRI for the assessment of sports-related muscle injuries in the context of soccer, including advanced imaging techniques, with the focus on the clinical relevance of imaging findings for the prediction of return to play.

Imaging of muscle injuries in sports medicine

Early diagnosis of muscle injuries is indispensable in order to initiate appropriate treatment and to facilitate optimal healing. The aim of this review is to provide an update on imaging of muscle injuries in sports medicine with afocus on ultrasound and magnetic resonance imaging (MRI) and to present experimental approaches in addition to routine diagnostic procedures. A PubMed literature search for the years 2012-2022 using the following keywords was performed: muscle, muscle injury, muscle imaging, muscle injury classification, delayed onset muscle soreness, ultrasound, MRI, sodium MRI, potassium MRI, ultra-high-field MRI, injuries of athletes. Imaging is crucial to confirm and assess the extent of sports-related muscle injuries and may help establishing treatment decisions, which directly affect the prognosis. This is of importance when the diagnosis or grade of injury is unclear, when recovery is taking longer than expected, and when interventional or surgical management may be necessary. In addition to established methods such as B‑mode ultrasound and 1H‑MRI, individual studies show promising approaches to further improve the imaging of muscle injuries in the future. Prior to the integration of contrast-enhanced ultrasound and X‑nuclei into clinical routine, additional studies are needed to validate these techniques further. B‑mode ultrasound represents an easily available, cost-effective modality for the initial diagnosis of muscle injuries. MRI is still considered the reference standard and enables an accurate morphological assessment of the extent of the injury. There are still no imaging approaches available for the objective determination of the optimal point of return to play.

Use of GPS to measure external load and estimate the incidence of muscle injuries in men's football: A novel descriptive study.

Measurement of external load in players provides objective information to optimise the weekly balance between training and recovery to improve performance and prevent injuries. Our aim was to evaluate the incidence of sports-related muscle injuries of the lower limb in relation to external load, measured by global positioning system (GPS), in football players. A descriptive study was carried out. Data were collected from 71 professional male football players (30 professionals and 41 youth players) from an elite football club competing in the Spanish and European League in the 2017-2018 season. As external load variables, we measured High Metabolic Load Distance (HMLD), High Speed Running (HSR), Player Load (PL), and Total Distance (TD) through GPS. Injury rate (IR) was calculated both in relation to such GPS load metrics and to load exposure time. We considered categories (youth and professional), playing positions (centre back, full back, midfielder, and forward), and training day with respect to match-day (-4MD, -3MD, -2MD, -1MD, MD, +1MD, +2MD). The GPS load metrics HMLD, HSR, PL, and TD showed very similar patterns across categories and positions, but varied according to training session or MD. The highest loads were observed on MD and three days prior to the match (-3MD). Similarly, the overall IR, both calculated per load exposure time and per GPS load metrics, was highest on MD and -3MD. Again, no differences were observed between youth and professional players. Midfielders demonstrated the highest IR in all metrics, followed by the forwards. In conclusion, this study suggests that external load and incidence of muscle injuries are directly proportional. Therefore, the measurement of more external load variables other than load exposure time, such as the GPS metrics HMLD, HSR, PL, and TD may help to describe the pattern and magnitude of injuries. Future studies based on ours may help to further improve the understanding of the incidence of muscle injuries on the basis of external loads measurements in different football teams.

Muscle Precursor Cells Enhance Functional Muscle Recovery and Show Synergistic Effects With Postinjury Treadmill Exercise in a Muscle Injury Model in Rats

Background: Skeletal muscle injuries represent a major concern in sports medicine. Cell therapy has emerged as a promising therapeutic strategy for muscle injuries, although the preclinical data are still inconclusive and the potential clinical use of cell therapy has not yet been established. Purpose: To evaluate the effects of muscle precursor cells (MPCs) on muscle healing in a small animal model. Study Design: Controlled laboratory study. Methods: A total of 27 rats were used in the study. MPCs were isolated from rat (n = 3) medial gastrocnemius muscles and expanded in primary culture. Skeletal muscle injury was induced in 24 rats, and the animals were assigned to 3 groups. At 36 hours after injury, animals received treatment based on a single ultrasound-guided MPC (105 cells) injection (Cells group) or MPC injection in combination with 2 weeks of daily exercise training (Cells+Exercise group). Animals receiving intramuscular vehicle injection were used as controls (Vehicle group). Muscle force was determined 2 weeks after muscle injury, and muscles were collected for histological and immunofluorescence evaluation. Results: Red fluorescence–labeled MPCs were successfully transplanted in the site of the injury by ultrasound-guided injection and were localized in the injured area after 2 weeks. Transplanted MPCs participated in the formation of regenerating muscle fibers as corroborated by the co-localization of red fluorescence with developmental myosin heavy chain (dMHC)–positive myofibers by immunofluorescence analysis. A strong beneficial effect on muscle force recovery was detected in the Cells and Cells+Exercise groups (102.6% ± 4.0% and 101.5% ± 8.5% of maximum tetanus force of the injured vs healthy contralateral muscle, respectively) compared with the Vehicle group (78.2% ± 5.1%). Both Cells and Cells+Exercise treatments stimulated the growth of newly formed regenerating muscles fibers, as determined by the increase in myofiber cross-sectional area (612.3 ± 21.4 µm2 and 686.0 ± 11.6 µm2, respectively) compared with the Vehicle group (247.5 ± 10.7 µm2), which was accompanied by a significant reduction of intramuscular fibrosis in Cells and Cells+Exercise treated animals (24.2% ± 1.3% and 26.0% ± 1.9% of collagen type I deposition, respectively) with respect to control animals (40.9% ± 4.1% in the Vehicle group). MPC treatment induced a robust acceleration of the muscle healing process as demonstrated by the decreased number of dMHC-positive regenerating myofibers (enhanced replacement of developmental myosin isoform by mature myosin isoforms) (4.3% ± 2.6% and 4.1% ± 1.5% in the Cells and Cells+Exercise groups, respectively) compared with the Vehicle group (14.8% ± 13.9%). Conclusion: Single intramuscular administration of MPCs improved histological outcome and force recovery of the injured skeletal muscle in a rat injury model that imitates sports-related muscle injuries. Cell therapy showed a synergistic effect when combined with an early active rehabilitation protocol in rats, which suggests that a combination of treatments can generate novel therapeutic strategies for the treatment of human skeletal muscle injuries. Clinical Relevance: Our study demonstrates the strong beneficial effect of MPC transplant and the synergistic effect when the cell therapy is combined with an early active rehabilitation protocol for muscle recovery in rats; this finding opens new avenues for the development of effective therapeutic strategies for muscle healing and clinical trials in athletes undergoing MPC transplant and rehabilitation protocols.

The effect of Platelet-rich plasma on the repair of sports-related muscle, tendon and ligament injuries

Introduction: Platelet-rich plasma (PRP) treatment is a developing technology that ambitions to recover the procedure of tissue overhaul via the distribution of bioactive representatives, which will deliver chemotactic, proliferative, and anabolic cellular retorts and improve retrieval of tissue purpose. Materials and methods: Fifty-three recreational athletes were registered in the study. The patients were enrolled from the Emergency ward in the University Hospital at Parma rendering to a pre-defined procedure. Each patient was evaluated by ultrasound imaging to assess the range and mark of muscle harm. Only grade II lesions were preserved with 3 ultrasound-guided vaccinations of autologous platelet-rich plasma every seven days. Platelet distillate was formed as per the standard methods, with a 10% erraticism in platelet count. The platelet gel for medical use was found by addition thrombin to the distillates beneath regular circumstances. Consequences measured were: pain reduction, muscle function retrieval, and reappearance to sports activity, ultrasound-imaging tissue remedial, relapses, local contagions, and any side effect through the action. Results: In all cases muscle lesions cured completely on ultrasound-imaging, the sting vanished, and muscle function retrieval was recognized with a reappearance to sports activity. A solo patient had a reversion 1 year after cure. Conclusion: Platelet-rich plasma vaccinated into the harm site is one of the greatest significant factors interpreting the behavior operative. Rendering to the present consequences, which document complete muscle retrieval and no reversion excluding for one patient, platelet-rich plasma ultrasound-guided vaccination signifies an effective mini-aggressive cure for muscle harm.

Influence of Intermittent Cold Stimulations on CREB and Its Targeting Genes in Muscle: Investigations into Molecular Mechanisms of Local Cryotherapy.

Local cryotherapy is widely used as a treatment for sports-related skeletal muscle injuries. The molecular mechanisms are unknown. To clarify these mechanisms, we applied one to three 15-min cold stimulations at 4 °C to various cell lines (in vitro), the tibialis anterior (TA) muscle (ex vivo), and mouse limbs (in vivo). In the in vitro assay, cyclic AMP (cAMP) response element binding protein 1 (CREB1) was markedly phosphorylated (p-CREB1), and the CREB-binding protein (CBP) was recruited to p-CREB-1 in response to two or three cold stimulations. In a reporter assay with the cAMP-responsive element, the signals significantly increased after two to three cold stimulations at 4 °C. In the ex vivo study, CREB-targeting genes were significantly upregulated following two or three cold stimulations. The in vivo experiment disclosed that cold stimulation of a mouse limb for 9 days significantly increased mitochondrial DNA copy number and upregulated genes involved in mitochondrial biogenesis. The results suggest that local cryotherapy increases CREB transcription and upregulates CREB-targeting genes, in a manner dependent on cold stimulation frequency and duration. This information will inform further investigations into local cryotherapy as a treatment for sports-related skeletal muscle trauma.

Platelet-rich plasma for sports-related muscle, tendon and ligament injuries: an umbrella review.

Platelet-rich plasma (PRP) has been used in different non-transfusion indications due to its role in tissue regeneration and healing. The aim of this overview of systematic reviews (umbrella review) is to provide a summary of the existing research syntheses related to PRP use for sports-related muscle, tendon and ligament injuries. Literature searches were performed in MEDLINE, Embase, and Cochrane Library to identify systematic reviews focusing on PRP use for sports-related muscle, tendon and ligament injuries. The methodological quality of included studies was assessed using the checklist for systematic reviews and research syntheses developed by the Joanna Briggs Institute and the GRADE assessment. Twenty-two studies met the inclusion criteria. Five studies evaluated PRP use for acute muscle injury, and 17 evaluated PRP use for tendon and ligament injury. Studies were heterogeneous in terms of the dose and number of PRP injections, and the control groups. Three of the 5 reviews evaluating acute muscle injury concluded that PRP had no effect on the outcomes considered. One review shows superior efficacy of rehabilitation exercise compared to PRP. One review shows that PRP may result in an earlier return to sport for acute grade I-II injury. Eight out of the 17 reviews evaluating PRP for tendon and ligament injuries show a statistically significant (p<0.05) difference in pain and/or function outcome measures favouring PRP compared to controls, although most of the observed differences were small. Adverse events data and quality of life outcomes were rarely analysed or reported in the included studies and were considered clinically insignificant. In most of the included reviews, the available evidence was judged to be of low/very low quality due to risk of bias, inconsistency and imprecision, thus making the level of certainty of these findings low and not adequate to support the general use of PRP in this setting.

Ibuprofen inhibited migration of skeletal muscle cells in association with downregulation of p130cas and CrkII expressions

BackgroundNonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to treat sports-related muscle injuries. However, NSAIDs were recently shown to impede the muscle healing process after acute injury. Migration of skeletal muscle cells is a crucial step during the muscle healing process. The present study was performed to investigate the effect and molecular mechanisms of action of ibuprofen, a commonly used NSAID, on the migration of skeletal muscle cells.MethodsSkeletal muscle cells isolated from the gastrocnemius muscle of Sprague-Dawley rats were treated with ibuprofen. MTT assay (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) was used to evaluate cell viability, and cell apoptosis was evaluated by TUNEL assay, after ibuprofen treatment. Skeletal muscle cell migration and spreading were evaluated using the transwell filter migration assay and F-actin staining, respectively. The protein expression of p130cas and CrkII, which are cell migration facilitating genes, was determined by western blot analysis. The overexpression of p130cas of muscle cells was achieved by p130cas vector transfection.ResultsThe results demonstrated that ibuprofen did not have a significant negative effect on cell viability and apoptosis. Ibuprofen inhibited the migration and spreading of skeletal muscle cells in a dose-dependent manner. Ibuprofen also dose-dependently decreased the protein expression of p130cas and CrkII. Furthermore, overexpression of p130cas resulted in the promotion of cell migration and spreading and counteracted ibuprofen-mediated inhibition.ConclusionThis study suggested that ibuprofen exerts a potentially adverse effect on the migration of skeletal muscle cells by downregulating protein expression of p130cas and CrkII. These results indicate a possible mechanism underlying the possible negative effect of NSAIDs on muscle regeneration.

Imaging of Muscle Injuries in Sports Medicine: Sports Imaging Series.

In sports-related muscle injuries, the main goal of the sports medicine physician is to return the athlete to competition-balanced against the need to prevent the injury from worsening or recurring. Prognosis based on the available clinical and imaging information is crucial. Imaging is crucial to confirm and assess the extent of sports-related muscle injuries and may help to guide management, which directly affects the prognosis. This is especially important when the diagnosis or grade of injury is unclear, when recovery is taking longer than expected, and when interventional or surgical management may be necessary. Several imaging techniques are widely available, with ultrasonography and magnetic resonance imaging currently the most frequently applied in sports medicine. This state of the art review will discuss the main imaging modalities for the assessment of sports-related muscle injuries, including advanced imaging techniques, with the focus on the clinical relevance of imaging features of muscle injuries. © RSNA, 2017 Online supplemental material is available for this article.

Postinjury Exercise and Platelet-Rich Plasma Therapies Improve Skeletal Muscle Healing in Rats But Are Not Synergistic When Combined

Background: Skeletal muscle injuries are the most common sports-related injury and a major concern in sports medicine. The effect of platelet-rich plasma (PRP) injections on muscle healing is still poorly understood, and current data are inconclusive. Purpose: To evaluate the effects of an ultrasound-guided intramuscular PRP injection, administered 24 hours after injury, and/or posttraumatic daily exercise training for 2 weeks on skeletal muscle healing in a recently established rat model of skeletal muscle injury that highly mimics the muscle trauma seen in human athletes. Study Design: Controlled laboratory study. Methods: A total of 40 rats were assigned to 5 groups. Injured rats (medial gastrocnemius injury) received a single PRP injection (PRP group), daily exercise training (Exer group), or a combination of a single PRP injection and daily exercise training (PRP-Exer group). Untreated and intramuscular saline–injected animals were used as controls. Muscle force was determined 2 weeks after muscle injury, and muscles were harvested and evaluated by means of histological assessment and immunofluorescence microscopy. Results: Both PRP (exhibiting 4.8-fold higher platelet concentration than whole blood) and exercise training improved muscle strength (maximum tetanus force, TetF) in approximately 18%, 20%, and 30% of rats in the PRP, PRP-Exer, and Exer groups, respectively. Specific markers of muscle regeneration (developmental myosin heavy chain, dMHC) and scar formation (collagen I) demonstrated the beneficial effect of the tested therapies in accelerating the muscle healing process in rats. PRP and exercise treatments stimulated the growth of newly formed regenerating muscle fibers (1.5-, 2-, and 2.5-fold increase in myofiber cross-sectional area in PRP, PRP-Exer, and Exer groups, respectively) and reduced scar formation in injured skeletal muscle (20%, 34%, and 41% of reduction in PRP, PRP-Exer, and Exer groups, respectively). Exercise-treated muscles (PRP-Exer and Exer groups) had significantly reduced percentage of dMHC-positive regenerating fibers (35% and 47% decrease in dMHC expression, respectively), indicating that exercise therapies accelerated the muscle healing process witnessed by the more rapid replacement of the embryonic-developmental myosin isoform by mature muscle myosin isoforms. Conclusion: Intramuscular PRP injection and, especially, treadmill exercise improve histological outcome and force recovery of the injured skeletal muscle in a rat injury model that imitates sports-related muscle injuries in athletes. However, there was not a synergistic effect when both treatments were combined, suggesting that PRP does not add any beneficial effect to exercise-based therapy in the treatment of injured skeletal muscle. Clinical Relevance: This study demonstrates the efficacy of an early active rehabilitation protocol or single intramuscular PRP injection on muscle recovery. The data also reveal that the outcome of the early active rehabilitation is adversely affected by the PRP injection when the two therapies are combined, and this could explain why PRP therapies have failed in randomized clinical trials where the athletes have adhered to postinjection rehabilitation protocols based on the principle of early, active mobilization.

Imaging of Muscle Injuries in Sports Medicine: Sports Imaging Series.

In sports-related muscle injuries, the main goal of the sports medicine physician is to return the athlete to competition-balanced against the need to prevent the injury from worsening or recurring. Prognosis based on the available clinical and imaging information is crucial. Imaging is crucial to confirm and assess the extent of sports-related muscle injuries and may help to guide management, which directly affects the prognosis. This is especially important when the diagnosis or grade of injury is unclear, when recovery is taking longer than expected, and when interventional or surgical management may be necessary. Several imaging techniques are widely available, with ultrasonography and magnetic resonance imaging currently the most frequently applied in sports medicine. This state of the art review will discuss the main imaging modalities for the assessment of sports-related muscle injuries, including advanced imaging techniques, with the focus on the clinical relevance of imaging features of muscle injuries. © RSNA, 2017 Online supplemental material is available for this article.

Clinical predictors of time to return to competition following hamstring injuries

hamstring strain injuries are the most common sports-related muscle injuries and one of the main causes of missed sporting events. clinical findings reflecting hamstring injury severity at presentation predict time to sports resumption. cohort study (prognosis); Level of evidence, 2. five sports medicine specialists at four sports medicine centers prospectively evaluated 120 athletes within 5 days of acute hamstring injury. Patients were interviewed and asked to evaluate their worst pain on a visual analog scale (VAS). Four physical criteria were assessed at baseline: bruising, tenderness to palpation, pain upon isometric contraction, and pain upon passive straightening. The same standardized rehabilitation protocol was used in all patients. A standardized telephone interview was conducted 45 days after the injury to determine the time to-full recovery (≤40 days or >40 days). by univariate analysis, clinical criteria associated with a full recovery time >40 days were VAS pain score greater than 6, popping sound injury, pain during everyday activities for more than 3 days, bruising, and greater than 15° motion-range limitation. By multivariate analysis, only VAS pain score and pain during everyday activities were significantly associated with time to recovery >40 days (53% sensitivity, 95% specificity). the initial examination provides valuable information that can be used to predict the time to full recovery after acute hamstring injuries in athletes.

Sports-related acute and chronic avulsion injuries in children and adolescents with special emphasis on tennis

Acute and chronic sports-related muscle and tendon injuries are not infrequent in youngsters. In particular, the physis is prone to trauma as it constitutes the weakest part of the immature...

Ultrasound and magnetic resonance imaging in sports-related muscle injuries

The objective of this study was to evaluate the role of magnetic resonance imaging (MRI) and ultrasonography (US) in the diagnosis of traumatic muscle injuries. From June 2003 to June 2004, 81 football players with a history of traumatic muscle injuries to the lower limbs were examined. US was performed shortly after the trauma (from 6 to 72 h afterwards) and MRI within a maximum of 5 days. MRI revealed 26 minor and 55 major traumas. MRI and US showed complete concordance in 71 patients (site, type and extent of injury). US produced ten false negative results, including six minor lesions and four major lesions. US had a sensitivity of 87.65% in the correct identification of muscle injuries; its sensitivity was 92.72% for major lesions and 76.92% for minor lesions, 57% for delayed-onset muscle soreness (DOMS), 80% for lengthenings, 83% for contractures, 84% for strains, 87.5% for mild contusions and 100% for severe contusions. US is the first-line technique for examination of muscle injuries. MRI is able to reveal lesions that may be missed at US and provide a more accurate assessment of site and extent of injury.

Hyperbaric oxygen increases the contractile function of regenerating rat slow muscles.

Human trials of hyperbaric oxygen (HBO) treatment of sports-related muscle injuries are equivocal. Although most human skeletal muscles are composed of mixed muscle fiber types, it is unclear whether HBO affects fiber types differently. We tested the hypothesis that HBO can enhance the functional properties of regenerating rat soleus muscles that are composed predominantly of slow fibers. After intramuscular injection of bupivacaine hydrochloride to induce the degeneration of all fibers within the soleus muscle, treated rats received daily HBO treatment at 3 atmospheres absolute. In untreated rats, injured muscles demonstrated a reduced force-producing capacity (control soleus vs injured soleus, 220.3 +/- 2.5 vs 157.6 +/- 3.3 kN.m(-2) at 25 d postinjury, respectively, P < 0.05) and contained smaller regenerating muscle fibers than uninjured soleus muscles (fiber cross sectional area in control soleus vs injured soleus, 2289 +/- 164 vs 1154 +/- 92 microm 2 at 25 d postinjury, respectively, P < 0.05). The regenerating soleus muscles of HBO-treated rats demonstrated a greater force-producing capacity as a percentage of contralateral control muscles than the regenerating muscles from untreated rats at 14 d postinjury (regenerating HBO-soleus peak tension and untreated soleus peak tension, 42.9 +/- 1.9 and 35.8 +/- 3.9% of contralateral control muscles, respectively, P < 0.05), but no effect of treatment was observed at 25 d postinjury. HBO enhanced the contractile properties of regenerating rat soleus muscles after myotoxic injury, but this improvement was not sustained for the duration of the regenerative process. The data indicate that the outcome of HBO treatment of a muscle injury may be influenced by the fiber type composition of the injured muscle.

Hyperbaric oxygen increases the contractile function of regenerating rat slow muscles

GREGOREVIC, P., D. A. WILLIAMS, and G. S. LYNCH. Hyperbaric oxygen increases the contractile function of regenerating rat slow muscles. Med. Sci. Sports Exerc., Vol. 34, No. 4, pp. 630–636, 2002. Human trials of hyperbaric oxygen (HBO) treatment of sports-related muscle injuries are equivocal. Although most human skeletal muscles are composed of mixed muscle fiber types, it is unclear whether HBO affects fiber types differently. Purpose We tested the hypothesis that HBO can enhance the functional properties of regenerating rat soleus muscles that are composed predominantly of slow fibers. Methods After intramuscular injection of bupivacaine hydrochloride to induce the degeneration of all fibers within the soleus muscle, treated rats received daily HBO treatment at 3 atmospheres absolute. Results In untreated rats, injured muscles demonstrated a reduced force-producing capacity (control soleus vs injured soleus, 220.3 ± 2.5 vs 157.6 ± 3.3 kN·m−2 at 25 d postinjury, respectively, P < 0.05) and contained smaller regenerating muscle fibers than uninjured soleus muscles (fiber cross sectional area in control soleus vs injured soleus, 2289 ± 164 vs 1154 ± 92 μm2 at 25 d postinjury, respectively, P < 0.05). The regenerating soleus muscles of HBO-treated rats demonstrated a greater force-producing capacity as a percentage of contralateral control muscles than the regenerating muscles from untreated rats at 14 d postinjury (regenerating HBO-soleus peak tension and untreated soleus peak tension, 42.9 ± 1.9 and 35.8 ± 3.9% of contralateral control muscles, respectively, P < 0.05), but no effect of treatment was observed at 25 d postinjury. Conclusion HBO enhanced the contractile properties of regenerating rat soleus muscles after myotoxic injury, but this improvement was not sustained for the duration of the regenerative process. The data indicate that the outcome of HBO treatment of a muscle injury may be influenced by the fiber type composition of the injured muscle.

Sports-related muscle injuries of the lower extremity: MR imaging appearances.

Sports-related injuries of the lower extremity are frequent. Before magnetic resonance (MR) imaging was available, ultrasound, radionuclide scintigraphy and computed tomography were used to evaluate muscle trauma. Although relatively inexpensive, these imaging modalities are limited by their low specificity. The high degree of soft tissue contrast and multiplanar capability of MR imaging, allow direct visualization as well as characterization of traumatic muscle lesions. This pictorial review highlights the spectrum of traumatic muscle lesions on MRI, with emphasis on its typical appearances.

MR imaging of sports-related muscle injuries.

Magnetic resonance (MR) imaging of the thighs of 26 baseball athletes and one softball athlete were studied to evaluate muscle injuries. We documented the abnormalities present in MR imaging after a muscle injury and evaluated the role of MR imaging in muscle injuries. Fifteen of the athletes showed muscle abnormalities in MR images. These include muscle strains without tear, muscle tear, scar and chronic tendon injury. Having the advantages of high tissue contrast and multiplanar display capability, MR allowed direct visualization of the injured muscles and characterization of traumatic lesions. We conclude that MR could be a good imaging modality for evaluating muscle injuries.

Spin-Echo and STIR MR Imaging of Sports-Related Muscle Injuries at 1.5 T

Seventy patients with clinically diagnosed athletic muscle injuries of varying severity were studied with MR imaging at 1.5 T. Twenty underwent follow-up MR studies. In all cases, SE T1-weighted and double-echo T2-weighted pulse sequences were used. These were supplemented by short T1 inversion recovery (STIR) sequence in 36 cases. Muscle injuries were more readily seen with STIR images than with SE T2-weighted images. In both initial assessment and follow-up of tears, the use of the STIR technique allowed the greatest lesion/muscle contrast. Short TR, short TE SE images provided anatomic detail and were an adjunct to T2-dependent SE images in the evaluation of organized hematomas (11 cases). Follow-up MR studies in 20 patients at variable time intervals allowed demonstration of regression of the tear in 11 cases, fibrous scar formation in 5 cases, and recurrence of the tear in 4 cases. Evolution of hematomas into scar and into cyst was demonstrated in three and two cases, respectively. Owing to the additive effect of T1 and T2 mechanisms, the STIR sequence is well suited for initial evaluation and can replace T2-weighted images in the follow-up of muscle trauma.