A retrospective comparison of the biceps femoris long head muscle structure in athletes with and without hamstring strain injury history.

INTRODUCTION: Hamstring strain injuries (HSI) and re-injuries are endemic in high-speed running sports. The biceps femoris long head (BFlh) is the most frequently injured muscle among the hamstrings. Structural parameters of the hamstring muscle are stated to be susceptible to strain injuries at this location. This retrospective study targeted comparing the BFlh's structural parameters between previously injured and uninjured athletes. METHODS: Nineteen male athletes with previous BFlh strain injury history and nineteen athletes without former lower extremity injury history were included in this study. Fascicle length, mid-muscle belly and distal musculotendinous (MTJ) passive stiffnesses of the biceps femoris long head (BFlh) were examined via b-mode panoramic ultrasound scanning and ultrasound-based shear-wave elastography. Parameter comparisons of both legs within and between athletes with and without injury history were performed. RESULTS: Comparison of the BFlh fascicle length between the injured leg of the injured group and the legs of the controls revealed a trend to shorter fascicle lengths in the injured leg (p = 0.067, d = -0.62). However, the mid-muscle belly passive stiffness of the BFlh was significantly higher in the injured legs (p = 0.009, d = 0.7) compared with the controls. Additionally, the distal MTJ stiffness was much higher in the previously injured legs compared with controls (p < 0.001, d = 1.6). CONCLUSIONS: Outcomes support the importance of BFlh properties related to stiffness, and fascicle length for injury susceptibility in athletes. Future prospective studies should determine whether the higher stiffness in the injured athletes is a cause or consequence of the HSI. Physical therapy and rehabilitation programmes after HSI should focus on BFlh muscle properties i.e., elasticity and fascicle length for reducing re-injury and increasing sports performance.

Injectable tissue prosthesis for instantaneous closed-loop rehabilitation.

To construct tissue-like prosthetic materials, soft electroactive hydrogels are the best candidate owing to their physiological mechanical modulus, low electrical resistance and bidirectional stimulating and recording capability of electrophysiological signals from biological tissues1,2. Nevertheless, until now, bioelectronic devices for such prostheses have been patch type, which cannot be applied onto rough, narrow or deep tissue surfaces3-5. Here we present an injectable tissue prosthesis with instantaneous bidirectional electrical conduction in the neuromuscular system. The soft and injectable prosthesis is composed of a biocompatible hydrogel with unique phenylborate-mediated multiple crosslinking, such as irreversible yet freely rearrangeable biphenyl bonds and reversible coordinate bonds with conductive gold nanoparticles formed in situ by cross-coupling. Closed-loop robot-assisted rehabilitation by injecting this prosthetic material is successfully demonstrated in the early stage of severe muscle injury in rats, and accelerated tissue repair is achieved in the later stage.

Plasma myoglobin indicates muscle damage associated with acceleration/deceleration during football.

BACKGROUND: Monitoring muscle damage in athletes assists not only coaches to adjust the training workload but also medical staff to prevent injury. Measuring blood myoglobin concentration can help evaluate muscle damage. The novel portable device utilized in this study allows for easy on-site measurement of myoglobin, providing real-time data on the player's muscle damage. This study investigated the relationship between external load (global positioning system parameters) and internal loads (myoglobin concentration and creatine kinase activity) in 15 male professional football players before and after a match. METHODS: Whole blood samples from participants' fingertips were collected before the match (baseline) and at 2, 16, and 40 h after the match. Myoglobin concentrations were measured using the IA-100 compact immunoassay system. Creatine kinase concentrations were measured in a clinical laboratory, and match loads were monitored using a global positioning system device. RESULTS: The mean myoglobin concentration was significantly higher at 2 h than at the other time points (P<0.05), and decreased to baseline levels within 16 h post-match. The mean creatine kinase concentration increased after the match but did not reach a significant level. Muscle damage monitored by myoglobin after football match-play was strongly associated with acceleration/deceleration metrics rather than the sprint/high-speed running distance. CONCLUSIONS: Our findings indicate that myoglobin is a more sensitive marker of muscle damage than creatine kinase after football match-play. Monitoring myoglobin in athletes can aid in determining their recovery status from the previous training load and help practitioners manage the training load.

Effect of muscle pre-tension and pre-impact neck posture on the kinematic response of the cervical spine in simulated low-speed rear impacts.

Computational human body models (HBMs) can identify potential injury pathways not easily accessible through experimental studies, such as whiplash induced injuries. However, previous computational studies investigating neck response to simulated impact conditions have neglected the effect of pre-impact neck posture and muscle pre-tension on the intervertebral kinematics and tissue-level response. The purpose of the present study was addressing this knowledge gap using a detailed neck model subjected to simulated low-acceleration rear impact conditions, towards improved intervertebral kinematics and soft tissue response for injury assessment. An improved muscle path implementation in the model enabled the modeling of muscle pre-tension using experimental muscle pre-stretch data determined from previous cadaver studies. Cadaveric neck impact tests and human volunteer tests with the corresponding cervical spine posture were simulated using a detailed neck model with the reported boundary conditions and no muscle activation. Computed intervertebral kinematics of the model with pre-tension achieved, for the first time, the S-shape behavior of the neck observed in low severity rear impacts of both cadaver and volunteer studies. The maximum first principal strain in the muscles for the model with pre-tension was 27% higher than that without pre-tension. Although, the pre-impact neck posture was updated to match the average posture reported in the experimental tests, the change in posture was generally small with only small changes in vertebral kinematics and muscle strain. This study provides a method to incorporate muscle pre-tension in HBM and quantifies the importance of pre-tension in calculating tissue-level distractions.

Effect of muscle activation scheme in human head-neck model on estimating cervical spine ligament strain from military volunteer frontal impact data.

Cervical spine (c-spine) injuries are a common injury during automobile crashes. The objective of this study is to verify an existing head-neck (HN) finite element model with military volunteer frontal impact kinematics by varying the muscle activation scheme from previous literature. Proper muscle activation will allow for accurate percent elongation (strain) of the c-spine ligaments and will serve to establish ligamentous response during non-injury frontal impacts. Previous human research volunteer (HRV) frontal impact sled tests reported kinematic data that served as the input for HN model simulation. Peak sled acceleration (PSA) was varied between 10G and 30G for HRVs. Muscle activation was shifted to begin at 0 ms at start of impact to allow for proper muscle contraction in the HN model. Then, extensor muscle activation magnitude was varied between 20 and 100% to determine the proper activation necessary to match kinematic outputs from the model with experimental results. The model was validated against 10G test recorded response. Ligament strain was measured from multiple ligaments along the c-spine once the model was verified. The 40% activated extensor muscle scheme was deemed the most biofidelic, with CORA scores of 0.743 and 0.686 for head X linear acceleration and angular Y acceleration for 10G pulse. All PSA groups scored well with this muscle activation. Most ligaments were buffered well by the active simulation, with only the interspinous ligament nearing physiologic injury. With the HN model verified against additional kinematic data, simulations with higher accelerations to predict areas of injury in real life crash scenarios are possible.

Are Football Players More Prone to Muscle Injury after COVID-19 Infection? The "Italian Injury Study" during the Serie a Championship.

INTRODUCTION: Football was the first sport to resume competitions after the coronavirus disease 2019 (COVID-19) lockdown and promptly the hypothesis was raised of a potential relationship between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and musculoskeletal injuries in athletes. This study aimed to confirm the association between SARS-CoV-2 infection and muscle strain injury in a large population of elite football players and to investigate if the COVID-19 severity level could affect the risk of injury. METHODS: A retrospective cohort study involving 15 Italian professional male football teams was performed during the Italian Serie A 2020-2021 season. Injuries and SARS-CoV-2 positivity data were collected by team doctors through an online database. RESULTS: Of the 433 included players, we observed 173 SARS-CoV-2 infections and 332 indirect muscle strains. COVID-19 episodes mostly belonged to severity level I and II. The injury risk significantly increased after a COVID-19 event, by 36% (HR = 1.36, CI95% 1.05; 1.77, p-value = 0.02). The injury burden demonstrated an 86% increase (ratio = 1.86, CI95% 1.21; 2.86, p-value = 0.005) in the COVID-19 severity level II/III versus players without a previous SARS-CoV-2 infection, while level I (asymptomatic) patients showed a similar average burden (ratio = 0.92, CI95% 0.54; 1.58, p-value = 0.77). A significantly higher proportion of muscle-tendon junction injuries (40.6% vs. 27.1%, difference = 13.5%, CI95% 0.002%; 26.9%, p-value = 0.047) was found when comparing level II/III versus Non-COVID-19. CONCLUSIONS: This study confirms the correlation between SARS-CoV-2 infection and indirect muscle injuries and highlights how the severity of the infection would represent an additional risk factor.

Core Muscle Injury Producing Groin Pain in the Athlete: Diagnosis and Treatment.

Groin pain is a common cause of pain in the athlete and may be the result of a variety of causes. Musculoskeletal groin injuries are often associated with muscle strain, particularly the adductor and abdominal muscles, termed "core muscle injury" (CMI). Since the early 1960s, there have been a growing number of articles intending to identify, define, prevent, and treat this condition; to date, however, the lack of a universal definition and treatment approach has complicated the narrative around CMI. This article intends to review the recent literature surrounding CMI, identifying common defining characteristics, as well as delineating treatment protocols that benefit the injured patient populations. Emphasis is placed on the clinical outcomes of different treatment methodologies and failure rates.

[Research progress of lower limb muscle strength training in the treatment of lliotibial band syndrome].

Iliotibial band syndrome (ITBS), as an overused injury of the lower extremities, has developed into a common cause of lateral knee pain. At present, the treatment of ITBS includes drug therapy, muscle strength training, physical therapy, and surgical treatment. Among these methods, physical therapy, drug therapy, and surgical treatment can only alleviate the symptoms of patients. As a safe and effective treatment, lower limb muscle strength training can improve patients' muscle strength, correct abnormal gait, and reduce the recurrence rate of the disease by paying attention to the dynamic changes of patients' recovery process. At present, the pathogenesis of ITBS remains unclear, and the treatment methods are not unified. It is necessary to further study the biomechanical factors related to the lower extremities and develop more scientific and comprehensive muscle strength training methods.

Research progress of lower limb muscle strength training in the treatment of lliotibial band syndrome / 中国骨伤

Iliotibial band syndrome (ITBS), as an overused injury of the lower extremities, has developed into a common cause of lateral knee pain. At present, the treatment of ITBS includes drug therapy, muscle strength training, physical therapy, and surgical treatment. Among these methods, physical therapy, drug therapy, and surgical treatment can only alleviate the symptoms of patients. As a safe and effective treatment, lower limb muscle strength training can improve patients' muscle strength, correct abnormal gait, and reduce the recurrence rate of the disease by paying attention to the dynamic changes of patients' recovery process. At present, the pathogenesis of ITBS remains unclear, and the treatment methods are not unified. It is necessary to further study the biomechanical factors related to the lower extremities and develop more scientific and comprehensive muscle strength training methods.

[Effect of electroacupuncture of "Weizhong" (BL40) on iron metabolism disorder in rats with lumbar multifidus muscle injury].

OBJECTIVE: To observe the effect of electroacupuncture (EA) of "Weizhong" (BL40) on the disorder of iron metabolism and the level of oxidative stress after lumbar multifidus muscle injury (LMMI), so as to explore its mechanisms underlying promoting the repair of LMMI. METHODS: Male SD rats were randomly divided into normal, model and EA groups (6 rats in each group). The LMMI model was established by injecting 0.5% bupivacaine (BPVC) solution (400 µL) into the lumbar multifidus muscle with the syringe-needle close to the spinous process (L4-L5). Twenty-four hours after successful establishment of the model, EA (2 Hz/15 Hz, 2 mA) was applied to bilateral BL40 for 30 min, once a day for 2 days. Histopathological changes of the multifid muscle were observed under microscope after H.E. staining, and the iron granules in the multifid muscle tissue observed after Prussian blue staining. The expression of glutathione synthase (GSS) was detected by Western blot, and the expressions of iron regulatory protein 1 (IRP1), ferroportin (Fpn), ferritin heavy chain 1 (FTH1, iron metabolism-related proteins) and gluta-thione peroxidase 4 (GPX4, functions in protecting cells against detrimental lipid peroxidation and governing a novel form of regulated necrotic cell death, called ferroptosis) mRNAs were detected by quantitative real-time PCR. The contents of glutathione (GSH) and malondialdehyde (MDA) were measured by biochemical methods. RESULTS: H.E. staining showed large areas of necrosis and breakage of muscle fibers, disordered arrangement of muscle fibers, widened muscle cell space, accompanying with a large number of inflammatory cell infiltration in the multifidus muscle tissue of the model group, which was relatively milder in the EA group. Outcomes of Prussian blue staining showed that compared with the normal group, there were more iron particles in the multifidus muscle tissue and enlarged muscle fiber gaps, which was also milder in the EA group. Compared with the normal group, the expression level of IRP1 mRNA and content of MDA were significantly increased (P<0.001), the expression levels of Fpn, FTH1 and GPX4 mRNAs and GSS protein, and the content of GSH were considerably decreased (P<0.001) in the model group. In comparison with the model group, the increase of IRP1 mRNA expression and MDA content, as well as the decrease of Fpn, FTH1 and GPX4 mRNAs expressions and GSH content were reversed in the EA group (P<0.001,P<0.05,P<0.01). CONCLUSION: EA of BL40 has a protect effect in BPVC-induced injury of lumbar multifidus muscle in rats, which may be related to its functions in improving iron metabolism to reduce oxidative damage by regulating expression of IRP1, Fpn and FTH1.

The Effect of 13 Weeks Long-Distance Bicycle Riding on Inflammatory Response Indicators Related to Joint Cartilage and Muscle Damage.

This study was to investigate the effects of 13 weeks of long-distance cycling on biomarkers of joint cartilage, muscle damage and inflammation. All subjects in this study were seven participants of the "One Korea New-Eurasia Peace Cycle Expedition", in which they rode cycles from Berlin, Germany to Seoul, Korea for thirteen weeks. The total course of the expedition was divided into three sub-courses: course 1 (from Berlin to Moscow), course 2 (from Moscow to Ulaanbaatar) and course 3 (from Ulaanbaatar to Seoul). All the selected participants rode 87.4 km/day (course 1), 70.4 km/day (course 2) and 57.6 km/day (course 3) on average, respectively. We collected their blood samples before the expedition in Seoul (S1), after course 1 in Moscow (M), after course 2 in Ulaanbaatar (U) and after the expedition in Seoul (S2), to analyze biomarkers of joint cartilage damage (Cartilage Oligomeric Matrix Protein; COMP), muscle damage (Creatine Phosphokinase; CPK, Lactate Dehydrogenase; LDH, Myoglobin), inflammation (Interleukin-6; IL-6, Interleukin-1ß; IL-1ß, Tumor Necrosis Factor-α; TNF-α, C-Reactive Protein; CRP) and stress hormone (Cortisol). According to this result, COMP (S1; 188.37 ± 46.68 ng/mL) showed a significant increase after the expedition course 1 (M; 246.69 ± 51.69 ng/mL, p = 0.012) and course 2 (U; 237.09 ± 62.57 ng/mL, p = 0.047), and recovered to the stable state after expedition course 3 (S2; 218.46 ± 34.78. p = 0.047). Biomarkers of muscle damage (CPK, LDH and Myoglobin) and inflammation (IL-6, IL-1ß, TNF-α and CRP) were not significantly changed in all courses, but CRP (S1; 1.07 ± 0.76 ng/mL) showed a tendency to decrease after the expedition course 1 (M; 0.3 ± 0.1 mg/mL, p = 0.044). Lastly, the Cortisol level significantly increased in all courses (per p < 0.05), but the Cortisol level after expedition course 3 (S2; 21.00 ± 3.65 mg/mL) was lower than that of after the expedition course 1 (M; 24.23 ± 2.47 mg/mL, p = 0.028). In summary, it seems that repetitive and continuous 50−90 km/day of cycling can increase joint cartilage damage risk and stress hormone temporarily. However, this result suggests that the appropriate intensity of cycling for thirteen weeks does not increase physical damage, and rather enhances the human body to adapt to exercise training.

COVID-19 as a Potential Cause of Muscle Injuries in Professional Italian Serie A Soccer Players: A Retrospective Observational Study.

The COVID-19 pandemic has shocked the entire planet. The soccer world has also suffered major upheavals, and many professional soccer players have been infected with the virus. The aim of this study was to evaluate the incidence of injuries in Italian Serie A professional soccer players before and during the COVID-19 pandemic. Methods: We evaluated the incidence of muscle injuries between four competitive seasons of the Italian Serie A (2016-2017, 2017-2018, and 2018-2019 pre-COVID-19 vs. 2020/2021 post-COVID-19) in professional soccer players. Results: Significant differences were found in muscular injuries between the post-COVID-19 season and the previous seasons (p < 0.001). The median split of the players' positivity duration was of 15 days. The players' long positivity (PLP) group showed a significant number of muscular injuries compared to the players' short positivity (PSP) group (p < 0.0014, ES = 0.81, Large). The total teams' days of positivity were significantly related to the total team number of muscular injuries (r = 0.86; CI 95% 0.66 to 0.94; p < 0.0001). In conclusion, this data showed that the competitive season post-COVID-19 lockdown has a higher incidence of muscle injuries in Italian Serie A soccer players compared to the pre-pandemic competitive season.

Prognostic factors of muscle injury in elite football players: A media-based, retrospective 5-year analysis.

OBJECTIVES: Motor function has been demonstrated to be weakly predictive for the occurrence of muscle injury in team sports. This study examined the value of non-motor prognostic factors in elite football (soccer). DESIGN: Retrospective cohort study. SETTING: Analysis of a public data register (Transfermarkt.com). PARTICIPANTS: 1148 players of 38 German and English first-division football clubs. MAIN OUTCOME MEASURES: Binary logistic regression examining the association of prognostic factors (age, height, weight, BMI, playing position, market value, history of injury, number of played matches and minutes) and time-loss muscle injuries sustained during five consecutive seasons (2014/2015 to 2018/2019). RESULTS: A total of 1722 muscle injuries were observed in 619 players. History of general musculoskeletal injury (OR 5.3, 95% CI 3.8-7.5), playing position (OR 2.4-2.5), market value (OR 2.3, 95% CI 1.7-3.1), and history of muscle injury (OR 1.6, 95% CI 1.1-2.2) were associated with muscle injury. Sub-analyses revealed location-specific patterns. Playing position was not predictive for adductor injury and, except for one weak association (defender vs. goalkeeper: OR 1.05, 95%CI 0.42-2.62), the same applied to the calf. Contrary to other locations, thigh re-injury was not predicted by previous muscle injury. CONCLUSIONS: Non-motor factors display significant associations with injury risk in elite football players. Conditioning coaches may use this information to improve primary and secondary prevention, while scouting departments may benefit during recruitment.

Paramagnetic contrast medium in high-level athletes with lower limb muscle injuries: can it make the return to sport safer reducing the recurrence rate?

PURPOSE: The aim is to investigate whether contrast medium can improve accuracy in the assessment of healing muscle injury in high-level professional athletes. MATERIALS AND METHODS: Our series is a retrospective study including the records of 22 players (mean age 28 ± 5 SD) with lower limbs muscle injuries type 3a (Mueller-Wohlfarth). All athletes received two MRIs: the day after the injury and before resuming heavy effort activities. Contrast medium uptake was measured in the second MRI by comparing the mean enhancement at the lesion site (ME) with that of the healthy contralateral muscle (HM). The result is a percentage referred to as muscular contrast index (MC index). The difference between the mean MC index value between athletes with and without re-injury was assessed with both the Mann-Whitney and the Kruskal-Wallis test. RESULTS: Twenty-nine muscle injuries matched the inclusion criteria. The mean MC index values, adjusted for the variable of time elapsed between the last contrast examination and return to the field, were significantly different in the two study groups (p < .001). CONCLUSION: The contrast medium in the follow-up of muscle injuries may be useful in determining the degree of scar stability in a healing injury. Injuries with a high MC index were found to be 'unstable', with a higher rate of recurrence than those with a low MC index. Resumption of competitive activity after achieving not only clinical resolution but also a satisfactory MC index value may increase the safety of return to the field and reduce the recurrence rate.

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.