UNASSIGNED: Earlier statements suggested a negative impact of coronavirus disease 2019 (COVID-19) infection on sports performance and injury risk. With the COVID-19 pandemic under control and the dominance of a less-severe strain of the virus, there is a need to confirm whether these adverse effects still apply to the current situation.
UNASSIGNED: Infected players would have a higher noncontact muscle injury incidence compared with noninfected counterparts.
UNASSIGNED: Cohort observational study.
UNASSIGNED: Level 3.
UNASSIGNED: Seven teams (n = 147 players) competing in the Spanish professional women\'s football league (Liga F) were prospectively monitored during the 2021-2022 season. Data from noncontact injuries were recorded and classified following the latest consensus statement from the International Olympic Committee. COVID-19 was certified by the medical staff by regular polymerase chain reaction analysis.
UNASSIGNED: Ninety-two players suffered at least 1 noncontact muscle injury during the season. Injury incidence during the season was similar in players with COVID-19 (n = 83) and players without infection (5.1 ± 6.7 versus 4.9 ± 10.0 injuries/1000 h of play, respectively; P = 0.90). Players with COVID-19 were not more likely to suffer noncontact injuries compared with those players without infection (R2 = 0.02; odds ratio [OR] 95% confidence interval [95% CI] = 0.36-1.38; P = 0.31). There was no effect of COVID-19 on the days of absence due to injury (R2 = 0.01; OR 95% CI = 1.00-1.01; P = 0.44) or in the classification of the severity of the injury (P = 0.79).
UNASSIGNED: COVID-19 has no significant effect on noncontact injury incidence and severity in professional female football players.
UNASSIGNED: Currently, COVID-19 infection does not alter noncontact muscle injury risk in professional football and requires no further attention in terms of injury management. Usual return-to-play protocols apply to COVID-19 considering the particularities of each player since the severity of infection, period of inactivity, and effects on the player\'s health and performance.

This study sought to assess how post-game creatine kinase (CK) levels correlate with the number of sprints and the impact of the ACTN3 polymorphism on this response. This research constituted a descriptive/observational, retrospective cross-sectional study. DNA was extracted from blood samples for ACTN3 polymorphism genotyping. CK was measured 48 h after official matches, and the number of sprints (>19 km/h) was tracked using Global Positioning System (GPS) technology. The main cohort included 23 professional soccer players from the top tier of the Brazilian Championship. We analyzed 115 GPS + CK data sets. The replication cohort comprised 18 professional soccer players from the First Division of the Championship, had the same methodology applied, and featured a total of 90 GPS (sprints > 25.2 km/h) + CK data sets. For the main cohort, a significant positive correlation was seen between the number of sprints and the CK levels (p = 0.009). Athletes with the ACTN3 RR genotype had higher CK levels as more sprints were performed during the match (p = 0.017). However, the relationship was not found for X allele carriers (p > 0.05). For the replication cohort, there was a near-significant correlation between CK levels and the number of sprints (p = 0.05), and RR individuals showed a significant association (p = 0.01), whereas X allele carriers did not (p = 0.06). A greater number of sprints during matches is linked to higher CK levels, primarily among players with the ACTN3 RR genotype, which is potentially due to an increased presence of type II muscle fibers. These findings were replicated for both cohorts of elite Brazilian soccer players, emphasizing the importance of genetic factors in injury prevention.

The primary aim of the present investigation was to compare the acute physiological and perceptual responses between two modes of interval training using a randomized crossover design. More specifically, eleven young adult participants (23 ± 4 years, 77 ± 13 kg, 178 ± 7 cm) performed two protocols: one composed of whole-body calisthenics exercises and another on a cycle ergometer. Both protocols encompassed eight 20 s bouts at intensities equivalent to all-out (HIIT-WB) and 170% of the maximal power output (HIIT-C), respectively, interspersed with 10 s of passive rest. The peak and average heart rate, the rating of perceived effort, and blood lactate, creatine kinase, and lactate dehydrogenase concentrations were measured. Aside from blood lactate (HIIT-WB = 9.4 ± 1.8 mmo/L; HIIT-C = 12.5 ± 2.5 mmol/L, p < 0.05) and the rating of perceived exertion (HIIT-WB = 8.8 ± 0.9; HIIT-C = 9.6 ± 0.5, p < 0.05), physiological responses did not significantly differ between protocols (all p > 0.05), with high average heart rate values (HIIT-WB = 86 ± 6% HRmax; HIIT-C = 87 ± 4% HRmax) and a low magnitude of muscle damage, as inferred by CK and LDH concentrations (HIIT-WB = 205.9 ± 56.3 and 203.5 ± 72.4 U/L; HIIT-C = 234.5 ± 77.1 and 155.1 ± 65.3 U/L), respectively. It can be concluded that both protocols elicit vigorous heart rate responses and a low magnitude of muscle damage and, therefore, appear as viable alternatives to improve aerobic fitness. The inclusion of a whole-body HIIT protocol may be an interesting alternative for training prescription in relation to more common interval training protocols.

OBJECTIVE: To describe the injury mechanism and situational patterns of severe (absence >28 days) hamstring muscle injuries in professional male and female football (soccer) players.
METHODS: The data for males were sourced from Serie A clubs participating in both national and international competitions from 2018 to 2021. For the female cohort, hamstring injuries were identified during matches of the top national/international competitions from 2017 to 2023. Video footage was obtained, and three raters categorised injury mechanisms and situational patterns. Injuries were also examined according to the month, minute and location.
RESULTS: A total of 129 severe hamstring injuries were identified, with 64 occurring in females and 65 in males. Video analysis was possible for 29 (45%) female cases and 61 (94%) male cases. Female injuries had longer lay-off times (97.8 ± 77.1 days) than males (39.6 ± 20.9 days). Females had a higher proportion of indirect contact injuries (34%) than males (13%) and a lower proportion of non-contact injuries (66% vs. 87%). Four situational patterns were identified: running was the most common for both sexes, representing 59% of female injuries and 41% of male injuries. Over-stretching injuries were split across open and CKC scenarios but collectively explained nearly half (48%) of male injuries but only one in five (21%) female injuries. Kicking injuries had a higher proportion in females (17%) than males (10%). Injuries were more common in the second half for females and the first half for males.
CONCLUSIONS: Females had a higher proportion of indirect contact, running and kicking injuries and a lower proportion of non-contact and stretch-type injuries than males. Understanding injury patterns can inform tailored prevention programs, considering sex-specific differences.
METHODS: Level IV.

Changes in protein turnover play an important role in dynamic physiological processes, including skeletal muscle regeneration, which occurs as an essential part of tissue repair after injury. The inability of muscle tissue to recapitulate this regenerative process can lead to the manifestation of clinical symptoms in various musculoskeletal diseases, including muscular dystrophies and pathological atrophy. Here, we employed a workflow that couples deuterated water (2H2O) administration with mass spectrometry (MS) to systematically measure in-vivo protein turnover rates across the muscle proteome in 8-week-old male C57BL6/J mice. We compared the turnover kinetics of over 100 proteins in response to cardiotoxin (CTX) induced muscle damage and regeneration at unique sequential stages along the regeneration timeline. This analysis is compared to gene expression data from mRNA-sequencing (mRNA-seq) from the same tissue. The data reveals quantitative protein flux signatures in response to necrotic damage, in addition to sequential differences in cell proliferation, energy metabolism, and contractile gene expression. Interestingly, the mRNA changes correlated poorly with changes in protein synthesis rates, consistent with post-transcriptional control mechanisms. In summary, the experiments described here reveal the signatures and timing of protein flux changes during skeletal muscle regeneration, as well as the inability of mRNA expression measurements to reveal changes in directly measured protein turnover rates. The results of this work described here provide a better understanding of the muscle regeneration process and could help to identify potential biomarkers or therapeutic targets.

BACKGROUND: Fibrosis is a significant pathological feature of chronic skeletal muscle injury, profoundly affecting muscle regeneration. Fibro-adipogenic progenitors (FAPs) have the ability to differentiate into myofibroblasts, acting as a primary source of extracellular matrix (ECM). the process by which FAPs differentiate into myofibroblasts during chronic skeletal muscle injury remains inadequately explored.
METHODS: mouse model with sciatic nerve denervated was constructed and miRNA expression profiles between the mouse model and uninjured mouse were analyzed. qRT/PCR and immunofluorescence elucidated the effect of miR-27b-3p on fibrosis in vivo and in vitro. Dual-luciferase reporter identified the target gene of miR-27b-3p, and finally knocked down or overexpressed the target gene and phosphorylation inhibition of Smad verified the influence of downstream molecules on the abundance of miR-27b-3p and fibrogenic differentiation of FAPs.
RESULTS: FAPs derived from a mouse model with sciatic nerves denervated exhibited a progressively worsening fibrotic phenotype over time. Introducing agomiR-27b-3p effectively suppressed fibrosis both in vitro and in vivo. MiR-27b-3p targeted Transforming Growth Factor Beta Receptor 1 (TGF-βR1) and the abundance of miR-27b-3p was negatively regulated by TGF-βR1/Smad.
CONCLUSIONS: miR-27b-3p targeting the TGF-βR1/Smad pathway is a novel mechanism for regulating fibrogenic differentiation of FAPs. Increasing abundance of miR-27b-3p, suppressing expression of TGF-βR1 and inhibiting phosphorylation of smad3 presented potential strategies for treating fibrosis in chronic skeletal muscle injury.

OBJECTIVE: Intramuscular fat (IMF) infiltration and extracellular matrix (ECM) deposition are characteristic features of muscle dysfunction, such as muscular dystrophy and severe muscle injuries. However, the underlying mechanisms of cellular origin, adipocyte formation and fibrosis in skeletal muscle are still unclear.
METHODS: Pigs were injected with 50 % glycerol (GLY) to induce skeletal muscle injury and regeneration. The acyl chain composition was analyzed by lipidomics, and the cell atlas and molecular signatures were revealed via single-cell RNA sequencing (scRNA-seq). Adipogenesis analysis was performed on fibroblast/fibro-adipogenic progenitors (FAPs) isolated from pigs.
RESULTS: The porcine GLY-injured skeletal muscle regeneration model was characterized by IMF infiltration and ECM deposition. Skeletal muscle stem cells (MuSCs) and FAP clusters were analyzed to explore the potential mechanisms of adipogenesis and fibrosis, and it was found that the TGF-β signaling pathway might be a key switch that regulates differentiation. Consistently, activation of the TGF-β signaling pathway increased SMAD2/3 phosphorylation and inhibited adipogenesis in FAPs, while inhibition of the TGF-β signaling pathway increased the expression of PPARγ and promoted adipogenesis.
CONCLUSIONS: GLY-induced muscle injury and regeneration provides comprehensive insights for the development of therapies for human skeletal muscle dysfunction and fatty infiltration-related diseases in which the TGF-β/SMAD signaling pathway might play a primary regulatory role.

BACKGROUND: Previous studies have suggested that a reduced length of the biceps femoris long head (BFlh) fascicles may increase the risk of hamstring strain injury (HSI). However, it remains unclear whether the BFlh fascicles of the injured limb are shorter than those of the contralateral limb in athletes with an acute HSI.
OBJECTIVE: To investigate the between-limb asymmetry of BFlh fascicle length in amateur athletes with an acute HSI.
METHODS: Male amateur athletes were evaluated using ultrasound scans within five days following an HSI. The BFlh fascicle length was estimated using a validated equation.
RESULTS: Eighteen injured athletes participated in this study. There was no significant difference (p = 0.27) in the length of BFlh fascicles between the injured limb (9.53 ± 2.55 cm; 95%CI 8.26 to 10.80 cm) and the uninjured limb (10.54 ± 2.87 cm; 95%CI 9.11 to 11.97 cm). Individual analysis revealed high heterogeneity, with between-limb asymmetries (percentage difference of the injured limb compared to the uninjured limb) ranging from -42% to 25%. Nine out of the 18 athletes had a fascicle length that was more than 10% shorter in the injured limb compared to the uninjured limb, five athletes had a difference of less than 10%, and four athletes had a fascicle length that was more than 10% longer in the injured limb compared to the uninjured limb.
CONCLUSIONS: The architecture characteristics of injured and uninjured muscles is not consistent among athletes with HSI. Therefore, rehabilitation programs focused on fascicle lengthening should be evaluated on a case-by-case basis.

Surveillance of drug safety is an important aspect in the routine medical care. Adverse events caused by real-world drug utilization has become one of the leading causes of death and an urgent issue in the field of toxicology. Cardiovascular disease is now the leading cause of fatal diseases in most countries, especially in the elderly population who often suffer from multiple diseases and need long-term multidrug therapy. Among which, statins have been widely used to lower bad cholesterol and regress coronary plaque mainly in patients with hyperlipidemia and atherosclerotic cardiovascular diseases (ASCVD). Although the real-world benefits of statins are significant, different degrees and types of adverse drug reactions (ADR) such as liver dysfunction and muscle injury, have a great impact on the original treatment regimens as well as the quality of life. This review describes the epidemiology, mechanisms, early identification and post-intervention of statin-associated liver dysfunction and muscle injury based on the updated clinical evidence. It provides systematic and comprehensive guidance and necessary supplement for the clinical safety of statin use in cardiovascular diseases.

The objectives of this study were to analyse the peak muscle-tendon (MT) strain of the hamstring during an entire acceleration sprint overground and examine their relationship with relative joint angles and segment orientation in the sagittal plane, which are the direct causes of MT strain. Kinematic data were recorded using a 3D inertial motion capture system in 21 male semi-professional soccer players during 40-metre overground sprint. Scaled musculoskeletal models were used to estimate peak MT strain in the hamstring over 16 steps. Biceps femoris long head (BFLH) exhibited the largest peaks in MT strain compared to semitendinosus (ST) and semimembranosus (SM) muscles across all the steps, with its overall strain decreased as the number of steps and maximum speed increased. Hip flexion angle was found to be a strong predictor (p < 0.001) of joint angles, being the orientation of the pelvis in the sagittal plane of the segment with the greatest influence (p < 0.001) on the peak MT strain of BFLH during sprinting. The current study provides a biomechanical explanation for the high proportion of hamstring injuries in the acceleration phase of sprinting.