Quercetin supplementation promotes recovery after exercise-induced muscle damage: a systematic review and meta-analysis of randomized controlled trials.

Quercetin (Q) is one of the most frequently consumed flavonoids in the human diet. The purpose of this systematic review and meta-analysis was to determine the effects of Q supplementation on muscle damage, muscle soreness and biochemical markers of inflammation, antioxidant capacity and oxidative stress after intense exercise. A literature search of SPORTDiscus, PubMed, Web of Science and Scopus was performed from inception to May 31, 2022. Forest plots were generated with fixed or random-effect models and standardized mean differences (SMD). Data extraction and quality assessment were performed independently by two authors. After application of the inclusion and exclusion criteria, 13 studies with a total of 249 sedentary to well-trained participants were included. For all studies there were some concerns about the risk of bias. All but one study used a supplementation dosage of 1000 mg/day. Q supplementation accelerated recovery of muscle function and significantly decreased muscle soreness 0/24 h after exercise (SMD: -1.33; p = 0.03), creatine kinase levels 24/48 h after exercise (SMD: -1.15; p = 0.02), and post-exercise oxidative stress (SMD: -0.92; p = 0.03). However, Q supplementation had no effect on IL-6 concentration. Q supplementation with a dose of 1000 mg/day for periods of more than seven days and a maximum of 12 weeks appears to be a safe and efficacious strategy to reduce muscle damage and muscle soreness, as well as to enhance recovery after intense exercise in sedentary to well-trained young men. Systematic review registration: PROSPERO CRD42021266801.

Effects of Beetroot Supplementation on Recovery After Exercise-Induced Muscle Damage: A Systematic Review.

CONTEXT: Beetroots have antioxidant and anti-inflammatory properties, which may help attenuate inflammation and oxidative stress, enhancing recovery from exercise-induced muscle damage (EIMD). OBJECTIVE: To evaluate the effects of beetroot supplementation on oxidative stress, inflammation, and recovery after EIMD. DATA SOURCES: SPORTDiscus, PubMed, Web of Science, and Scopus databases were searched, and hand-searching was performed by looking to relevant studies that were cited in other studies. STUDY SELECTION: For a study to be included in this review, the following inclusion criteria had to be met: (1) research conducted with human participants, (2) original articles in peer-reviewed publications, (3) original studies that had investigated beetroot supplementation intervention on muscle damage and recovery, (4) research conducted with 1 control/placebo group, and (5) articles published from inception to October 2020. STUDY DESIGN: Systematic review using the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) statement. LEVEL OF EVIDENCE: Level 3. DATA EXTRACTION: Two of the 4 authors independently extracted data and assessed the methodological quality of the articles with the PEDro scale. All discrepancies were resolved through a consensus meeting. RESULTS: A total of 9 studies were included in this review. The methodological quality of the included studies ranged from moderate to high. Most of the studies found a better recovery of functional variables and muscle soreness, but improvements in markers of muscle damage, inflammation, and oxidative stress were not reported. CONCLUSION: The existing evidence suggests that a short-term beetroot supplementation has the potential to accelerate recovery of functional measures and muscle soreness, but further research is needed to clarify if a longer supplementation period (with some days before exercise and some days after) could also promote recovery of markers of muscle damage, inflammation, and oxidative stress.

Mechanical Properties of Lumbar and Cervical Paravertebral Muscles in Patients with Axial Spondyloarthritis: A Case-Control Study.

BACKGROUND: Axial spondyloarthritis (axSpA) affects spinal muscles, due to inflammation and structural damage. The mechanical properties of the muscles, such as tone or stiffness, could be altered in axSpA. The aim of this work is to analyze the mechanical properties of cervical and lumbar spine muscles in axSpA patients and their relationship with metrology measures, function, disease activity, structural damage and quality of life. METHODS: axSpA patients and age/gender/BMI matched healthy controls were recruited. The muscle mechanical properties (MMPs), such as tone or frequency, stiffness, decrement (linear elastic properties), relaxation and creep (viscoelastic properties), of cervical (semispinalis capitis) and lumbar (erector spinae) muscles were bilaterally measured at rest using myotonometry. Additionally, conventional metrology, BASMI (metrology index), BASDAI (disease activity index), mSASSS (radiological structural damage index) and SF-12 (health-related quality of life questionnaire) were used in the axSpA group. Between-groups comparison, intra-group correlations and multivariable regression analyses were performed to achieve the study aims. RESULTS: Thirty-four axSpA patients (mean age: 46.21 ± 8.53 y) and 34 healthy volunteers (mean age: 43.97 ± 8.49 y) were recruited. Both in cervical and lumbar spine, linear elastic parameters were significantly higher in axSpA patients in comparison with controls, while viscoelastic parameters were significantly lower. Lumbar muscle frequency, stiffness, relaxation, creep and cervical muscle elasticity were fair to strongly correlated (|0.346| < r < |0.774|) with age, functional status, activity of disease, structural damage and quality of life in axSpA patients. Furthermore, moderate to good fitted multivariate models (0.328 < R2 < 0.697) were obtained combining age, conventional metrology, activity of the disease and function for the estimation of cervical and lumbar MMPs. CONCLUSION: Mechanical properties of spinal muscles of axSpA patients differ from controls. Lumbar and cervical muscles exhibit greater linear elastic properties and lower viscoelastic properties, which are related with age, clinical and psychophysiological features of axSpA.

Transcranial Magnetic Stimulation Improves Muscle Involvement in Experimental Autoimmune Encephalomyelitis.

Skeletal muscle is affected in experimental autoimmune encephalomyelitis (EAE), which is a model of multiple sclerosis that produces changes including muscle atrophy; histological features of neurogenic involvement, and increased oxidative stress. In this study, we aimed to evaluate the therapeutic effects of transcranial magnetic stimulation (TMS) on the involvement of rat skeletal muscle and to compare them with those produced by natalizumab (NTZ). EAE was induced by injecting myelin oligodendrocyte glycoprotein (MOG) into Dark Agouti rats. Both treatments, NTZ and TMS, were implemented from day 15 to day 35. Clinical severity was studied, and after sacrifice, the soleus and extensor digitorum longus muscles were extracted for subsequent histological and biochemical analysis. The treatment with TMS and NTZ had a beneficial effect on muscle involvement in the EAE model. There was a clinical improvement in functional motor deficits, atrophy was attenuated, neurogenic muscle lesions were reduced, and the level of oxidative stress biomarkers was lower in both treatment groups. Compared to NTZ, the best response was obtained with TMS for all the parameters analyzed. The myoprotective effect of TMS was higher than that of NTZ. Thus, the use of TMS may be an effective strategy to reduce muscle involvement in multiple sclerosis.

Ultrasonographic and Histological Correlation after Experimental Reconstruction of a Volumetric Muscle Loss Injury with Adipose Tissue.

Different types of scaffolds are used to reconstruct muscle volume loss injuries. In this experimental study, we correlated ultrasound observations with histological findings in a muscle volume loss injury reconstructed with autologous adipose tissue. The outcome is compared with decellularized and porous matrix implants. Autologous adipose tissue, decellularized matrix, and a porous collagen matrix were implanted in volumetric muscle loss (VML) injuries generated on the anterior tibial muscles of Wistar rats. Sixty days after implantation, ultrasound findings were compared with histological and histomorphometric analysis. The muscles with an autologous adipose tissue implant exhibited an ultrasound pattern that was quite similar to that of the regenerative control muscles. From a histological point of view, the defects had been occupied by newly formed muscle tissue with certain structural abnormalities that would explain the differences between the ultrasound patterns of the normal control muscles and the regenerated ones. While the decellularized muscle matrix implant resulted in fibrosis and an inflammatory response, the porous collagen matrix implant was replaced by regenerative muscle fibers with neurogenic atrophy and fibrosis. In both cases, the ultrasound images reflected echogenic, echotextural, and vascular changes compatible with the histological findings of failed muscle regeneration. The ultrasound analysis confirmed the histological findings observed in the VML injuries reconstructed by autologous adipose tissue implantation. Ultrasound can be a useful tool for evaluating the structure of muscles reconstructed through tissue engineering.

Patients with Axial Spondyloarthritis Show an Altered Flexion/Relaxation Phenomenon.

Axial spondyloarthritis (axSpA) is a chronic rheumatic disease characterized by the presence of inflammatory back pain. In patients with chronic low back pain, the lumbar flexion relaxation phenomenon measured by surface electromyography (sEMG) differs from that in healthy individuals. However, sEMG activity in axSpA patients has not been studied. The purpose of this study was to analyze the flexion relaxation phenomenon in axSpA patients. A study evaluating 39 axSpA patients and 35 healthy controls was conducted. sEMG activity at the erector spinae muscles was measured during lumbar full flexion movements. sEMG activity was compared between axSpA patients and the controls, as well as between active (BASDAI ≥ 4) and non-active (BASDAI < 4) patients. The reliability (using intraclass correlation coefficients (ICC)), criterion validity and discriminant validity using the area Under the curve (AUC) for the inverse flexion/relaxation ratio (1/FRR) were evaluated. Significant differences (p < 0.05) were observed between axSpA patients and the control group in lumbar electric activity, especially during flexion, relaxation, and extension and in FRR and 1/FRR (0.66 ± 0.39 vs. 0.25 ± 0.19, respectively). In addition, significant differences were found between active and non-active but also between non-active and healthy subjects. The sEMG showed good reliability (ICC > 0.8 for 1/FRR) and criterion validity. ROC analysis showed good discriminant validity for axSpA patients (AUC = 0.835) vs. the control group using 1/FRR. An abnormal flexion/relaxation phenomenon exists in axSpA patients compared with controls. sEMG could be an additional objective tool in the evaluation of patient function and disease activity status.

The musculotendinous transition of the extracellular matrix

Histoarchitectural arrangement of muscle is prolonged with tendons, establishing a relationship through myotendinous junctions. However, the characteristics of the transition between myoconnective structures and tendon are not well known and it remains unclear whether the histoarchitectural organization of the extracellular matrix (ECM) of both organs continues to maintain the same structuring. (AU)

A Histoarchitectural Approach to Skeletal Muscle Injury: Searching for a Common Nomenclature.

In recent years, different classifications for muscle injuries have been proposed based on the topographic location of the injury within the bone-tendon-muscle chain. We hereby propose that in addition to the topographic classification of muscle injuries, a histoarchitectonic (description of the damage to connective tissue structures) definition of the injury be included within the nomenclature. Thus, the nomenclature should focus not only on the macroscopic anatomy but also on the histoarchitectonic features of the injury.

Structural abnormalities in the human diaphragm in drowning and hanging deaths: preliminary results.

PURPOSE: Previous experiments in rats have indicated that there are histological changes in skeletal muscle in drowning deaths; these changes include muscle fibers that contain ragged red fibers (RRF). The purpose of this study was to examine whether these changes also occur in humans. METHODS: Histologic and histochemical examinations of three muscles (diaphragm, pectoralis, and psoas) were performed on 24 cadavers with three different causes of death: 8 drowning, 8 hanging, and 8 sudden cardiac disease. Muscle samples were stained with hematoxylin-eosin, MGT, nicotinamide adenine dinucleotide-tetrazolium reductase, succinate dehydrogenase, ATPase, and acid phosphatase via standard staining procedures. RESULTS: There were statistically significant differences in the detection of RRFs in these cohorts. Additionally, several other cytoarchitectural changes (whorled and core-like fibers) were observed in the diaphragm in the drowning cohort and to a lesser extent in the hangings. These structural abnormalities were not observed in the sudden cardiac disease deaths, thus suggesting a common mechanism for the production of these muscular changes that is not shared in the cardiac death group. The mechanism is most likely intense hypoxia and mechanical trauma of the respiratory muscles in the setting of active blood circulation with intense muscle contraction. CONCLUSIONS: Our results confirmed that there are histological changes in the diaphragm in drownings and, to a lesser extent, in hangings.

Histology of skeletal muscle reconstructed by means of the implantation of autologous adipose tissue: an experimental study.

The purpose of this study was to determine the histological characteristics of a skeletal muscle reconstructed by means of the implantation of autologous adipose tissue following an experimentally-induced volumetric muscle loss. A cylindrical piece in the belly of the rat anterior tibial muscle was removed. In the hole, inguinal subcutaneous adipose tissue of the same rat was grafted. Animals were sacrificed 7, 14, 21, 28 and 60 days posttransplantation. Histological, histochemical, immunohistochemical and morphometric techniques were used. At all times analyzed, the regenerative muscle fibers formed from the edges of the muscle tissue showed histological, histochemical and immunohistochemical differences in comparison with the control group. These differences are related to delays in the maturation process and are related to problems in reinnervation and disorientation of muscle fibers. The stains for MyoD and desmin showed that some myoblasts and myotubes seem to derive from the transplanted adipose tissue. After 60 days, the transplant area was 20% occupied by fibrosis and by 80% skeletal muscle. However, the neo-muscle was chaotically organized showing muscle fiber disorientation and centronucleated fibers with irregular shape and size. Our results support the hypothesis that, at least from a morphological point of view, autologous adipose tissue transplantation favors reconstruction following a volumetric loss of skeletal muscle by combining the inherent regenerative response of the organ itself and the myogenic differentiation of the stem cells present in the adipose tissue. However, in our study, the formed neo-muscle exhibited histological differences in comparison with the normal skeletal muscle.

Gender variability in electromyographic activity, in vivo behaviour of the human gastrocnemius and mechanical capacity during the take-off phase of a countermovement jump.

PURPOSE: The purpose of this study was to analyse gender differences in neuromuscular behaviour of the gastrocnemius and vastus lateralis during the take-off phase of a countermovement jump (CMJ), using direct measures (ground reaction forces, muscle activity and dynamic ultrasound). METHODS: Sixty-four young adults (aged 18-25 years) participated voluntarily in this study, 35 men and 29 women. The firing of the trigger allowed obtainment of data collection vertical ground reaction forces (GRF), surface electromyography activity (sEMG) and dynamic ultrasound gastrocnemius of both legs. RESULTS: Statistically significant gender differences were observed in the jump performance, which appear to be based on differences in muscle architecture and the electrical activation of the gastrocnemius muscles and vastus lateralis. So while men developed greater peak power, velocity take-offs and jump heights, jump kinetics compared to women, women also required a higher electrical activity to develop lower power values. Additionally, the men had higher values pennation angles and muscle thickness than women. CONCLUSION: Men show higher performance of the jump test than women, due to significant statistical differences in the values of muscle architecture (pennation angle and thickness muscle), lower Neural Efficiency Index and a higher amount of sEMG activity per second during the take-off phase of a CMJ.

Muscle physiology changes induced by every other day feeding and endurance exercise in mice: effects on physical performance.

Every other day feeding (EOD) and exercise induce changes in cell metabolism. The aim of the present work was to know if both EOD and exercise produce similar effects on physical capacity, studying their physiological, biochemical and metabolic effects on muscle. Male OF-1 mice were fed either ad libitum (AL) or under EOD. After 18 weeks under EOD, animals were also trained by using a treadmill for another 6 weeks and then analyzed for physical activity. Both, EOD and endurance exercise increased the resistance of animals to extenuating activity and improved motor coordination. Among the groups that showed the highest performance, AL and EOD trained animals, ALT and EODT respectively, only the EODT group was able to increase glucose and triglycerides levels in plasma after extenuating exercise. No high effects on mitochondrial respiratory chain activities or protein levels neither on coenzyme Q levels were found in gastrocnemius muscle. However, exercise and EOD did increase ß-oxidation activity in this muscle accompanied by increased CD36 levels in animals fed under EOD and by changes in shape and localization of mitochondria in muscle fibers. Furthermore, EOD and training decreased muscle damage after strenuous exercise. EOD also reduced the levels of lipid peroxidation in muscle. Our results indicate that EOD improves muscle performance and resistance by increasing lipid catabolism in muscle mitochondria at the same time that prevents lipid peroxidation and muscle damage.