Muscle Injuries in Sports: A New Evidence-Informed and Expert Consensus-Based Classification with Clinical Application

Orchard Sports Injury and Illness Classification System (OSIICS) Version 15

BACKGROUND

Sports medicine (injury and illnesses) requires distinct coding systems because the International Classification of Diseases is insufficient for sports medicine coding. The Orchard Sports Injury and Illness Classification System (OSIICS) is one of two sports medicine coding systems recommended by the International Olympic Committee. Regular updates of coding systems are required.

METHODS

For Version 15, updates for mental health conditions in athletes, sports cardiology, concussion sub-types, infectious diseases, and skin and eye conditions were considered particularly important.

RESULTS

Recommended codes were added from a recent International Olympic Committee consensus statement on mental health conditions in athletes. Two landmark sports cardiology papers were used to update a more comprehensive list of sports cardiology codes. Rugby union protocols on head injury assessment were used to create additional concussion codes.

CONCLUSION

It is planned that OSIICS Version 15 will be translated into multiple new languages in a timely fashion to facilitate international accessibility. The large number of recently published sport-specific and discipline-specific consensus statements on athlete surveillance warrant regular updating of OSIICS.

Biomaterials-Based Technologies in Skeletal Muscle Tissue Engineering

For many clinically prevalent severe injuries, the inherent regenerative capacity of skeletal muscle remains inadequate. Skeletal muscle tissue engineering (SMTE) seeks to meet this clinical demand. With continuous progress in biomedicine and related technologies including micro/nanotechnology and 3D printing, numerous studies have uncovered various intrinsic mechanisms regulating skeletal muscle regeneration and developed tailored biomaterial systems based on these understandings. Here, the skeletal muscle structure and regeneration process are discussed and the diverse biomaterial systems derived from various technologies are explored in detail. Biomaterials serve not merely as local niches for cell growth, but also as scaffolds endowed with structural or physicochemical properties that provide tissue regenerative cues such as topographical, electrical, and mechanical signals. They can also act as delivery systems for stem cells and bioactive molecules that have been shown as key participants in endogenous repair cascades. To achieve bench-to-bedside translation, the typical effect enabled by biomaterial systems and the potential underlying molecular mechanisms are also summarized. Insights into the roles of biomaterials in SMTE from cellular and molecular perspectives are provided. Finally, perspectives on the advancement of SMTE are provided, for which gene therapy, exosomes, and hybrid biomaterials may hold promise to make important contributions.

Epidemiology of Non-Contact Muscle Injuries in the Italian Male Elite Under-19 Football (Soccer) Championship

BACKGROUND

While extensive research exists on muscle injuries among adult football players, a notable gap persists in studies concerning younger footballers. The aim of the current study is to provide epidemiological data on the characteristics of time-loss muscle injuries in young football players participating in the Italian Under-19 male elite Championship ("Primavera 1").

RESULTS

Conducted as a multicentre, prospective, observational cohort study, this research gathered injury data from the 2022-23 season across 14 of the 18 Clubs in the first Italian Under-19 championship. The cohort comprised 391 players with a mean age (± standard deviation) of 18.0 ± 0.4 years. A total of 479 injuries were reported, resulting in 14,231 days of activity lost. Of these, muscle injuries were 209 (44%), accounting for 4,519 (32%) days lost. Overall muscle injuries incidence was 1.82/1000 hours, with a mean injury burden of 39.4 days lost/1000 hours. Almost all muscle injuries (206 out of 209: 98.5%) occurred in hamstrings, quadriceps, adductors, calf and iliopsoas. Hamstrings injuries were the most burdensome (18.8 days lost/1000 hours) accounting for nearly half of all days lost due to muscle injuries. Incidence and burden of adductors injuries (0.25 injuries and 4.1 days lost/1000 hours, respectively) were found to be comparable to calf injuries (0.24 injuries and 4.7 days lost/1000 hours, respectively). Iliopsoas injuries accounted for a noteworthy portion of the total, with an injury incidence of 0.16/1000 hours and a burden of 3.3 days lost/1000 hours. Injuries with myo-tendinous or myo-aponeurotic involvement demonstrated delayed return-to-football compared to those without such involvement (35.6 vs. 18.5 days, p < 0.0001).

CONCLUSIONS

The study highlighted a peculiar distribution of non-contact muscle injuries among elite young football players. While hamstring injuries were confirmed as the most burdensome, incidence and burden of adductors and calf injuries were found to be similar. A significant incidence and burden of iliopsoas injuries were observed. These findings suggest potential implementations for targeted injury prevention strategies in the Italian male elite Under-19 football Championship.

Engineering interfacial tissues: The myotendinous junction

The myotendinous junction (MTJ) is the interface connecting skeletal muscle and tendon tissues. This specialized region represents the bridge that facilitates the transmission of contractile forces from muscle to tendon, and ultimately the skeletal system for the creation of movement. MTJs are, therefore, subject to high stress concentrations, rendering them susceptible to severe, life-altering injuries. Despite the scarcity of knowledge obtained from MTJ formation during embryogenesis, several attempts have been made to engineer this complex interfacial tissue. These attempts, however, fail to achieve the level of maturity and mechanical complexity required for in vivo transplantation. This review summarizes the strategies taken to engineer the MTJ, with an emphasis on how transitioning from static to mechanically inducive dynamic cultures may assist in achieving myotendinous maturity.

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.

Hamstring Injuries: A Paradigm for Return to Play

Muscle injuries are the most common sports-related injuries, with hamstring involvement most common in professional athletes. These injuries can lead to significant time lost from play and have a high risk of reinjury. We review the anatomy, mechanisms of injury, diagnostic imaging modalities, and treatment techniques for hamstring injuries. We also present the latest evidence related to return to play (RTP) after hamstring injuries, including a review of articles targeted to RTP in European soccer (Union of European Football Associations), American football (National Football League), and other professional sports. Review of imaging findings in hamstring injury, grading systems for injuries, considerations for RTP, as well as advances in injury prevention, are discussed.

Hamstring muscle injuries in athletics

Hamstring muscle injuries (HMI) are a common and recurrent issue in the sport of athletics, particularly in sprinting and jumping disciplines. This review summarizes the latest literature on hamstring muscle injuries in athletics from a clinical perspective. The considerable heterogeneity in injury definitions and reporting methodologies among studies still needs to be addressed for greater clarity. Expert teams have recently developed evidence-based muscle injury classification systems whose application could guide clinical decision-making; however, no system has been adopted universally in clinical practice, yet.The most common risk factor for HMI is a previously sustained injury, particularly early after return-to-sport. Other modifiable (e.g. weakness of thigh muscles, high-speed running exposure) and non-modifiable (e.g. older age) risk factors have limited evidence linking them to injury. Reducing injury may be achieved through exercise-based programs, but their specific components and their practical applicability remain unclear.Post-injury management follows similar recommendations to other soft tissue injuries, with a graded progression through stages of rehabilitation to full return to training and then competition, based on symptoms and clinical signs to guide the individual speed of the recovery journey. Evidence favoring surgical repair is conflicting and limited to specific injury sub-types (e.g. proximal avulsions). Further research is needed on specific rehabilitation components and progression criteria, where more individualized approaches could address the high rates of recurrent HMI. Prognostically, a combination of physical examination and magnetic resonance imaging (MRI) seems superior to imaging alone when predicting 'recovery duration,' particularly at the individual level.

A Novel Tendon Injury Model, Induced by Collagenase Administration Combined with a Thermo-Responsive Hydrogel in Rats, Reproduces the Pathogenesis of Human Degenerative Tendinopathy

Patellar tendinopathy is a common clinical problem, but its underlying pathophysiology remains poorly understood, primarily due to the absence of a representative experimental model. The most widely used method to generate such a model is collagenase injection, although this method possesses limitations. We developed an optimized rat model of patellar tendinopathy via the ultrasound-guided injection of collagenase mixed with a thermo-responsive Pluronic hydrogel into the patellar tendon of sixty male Wistar rats. All analyses were carried out at 3, 7, 14, 30, and 60 days post-injury. We confirmed that our rat model reproduced the pathophysiology observed in human patients through analyses of ultrasonography, histology, immunofluorescence, and biomechanical parameters. Tendons that were injured by the injection of the collagenase-Pluronic mixture exhibited a significant increase in the cross-sectional area (p < 0.01), a high degree of tissue disorganization and hypercellularity, significantly strong neovascularization (p < 0.01), important changes in the levels of types I and III collagen expression, and the organization and presence of intra-tendinous calcifications. Decreases in the maximum rupture force and stiffness were also observed. These results demonstrate that our model replicates the key features observed in human patellar tendinopathy. Collagenase is evenly distributed, as the Pluronic hydrogel prevents its leakage and thus, damage to surrounding tissues. Therefore, this model is valuable for testing new treatments for patellar tendinopathy.

Epidemiology of hamstring injuries in 538 cases from an FC Barcelona multi sports club

OBJECTIVES

Hamstring injuries are the most common muscle injuries in team sports. The aims of this study were to describe the epidemiology of hamstring muscle injuries in the professional and amateur sport sections of a multi-sport club Football Club Barcelona (FCB) and to determine any potential correlation between return-to-play (RTP) and injury location, severity of connective tissue damage, age, sex, and athlete's level of competition.

METHODS

This descriptive epidemiological study with data collected from September 2007 to September 2017 stored in the FCB database. The study included non-contact hamstring injuries sustained during training or competition.

RESULTS

A total of 538 hamstring injuries were reported in the club's database, of which 240 were structurally verified by imaging as hamstring injuries. The overall incidence for the 17 sports studied was 1.29 structurally verified hamstring injuries per 100 athletes per year. The muscle most commonly involved in hamstring injuries was the biceps femoris, and the connective tissue most frequently involved was the myofascial. There was no evidence of a statistically significant association between age and RTP after injury, and no statistically significant difference between sex and RTP. However, the time loss by professionals was shorter than for amateurs, and proximal hamstring injuries took longer RTP than distal ones.

CONCLUSION

In the 17 sports practiced at multi-sport club, the incidence of hamstring injury was 1.29 per 100 athletes per year. Players from sports in which high-speed sprinting and kicking are necessary, and amateurs, were at higher risk of suffering a hamstring injury. In addition, proximally located hamstring injuries involving tendinous connective tissue showed the longest RTP time. Age did not seem to have any influence on RTP. Documenting location and the exact tissue involved in hamstring injuries may be beneficial for determining the prognosis and RTP.

Ultrasound shear wave seeds reduced following hamstring strain injury but not after returning to sport

OBJECTIVES

The purpose of the study was to investigate differences in ultrasound shear wave speed (SWS) between uninjured and injured limbs following hamstring strain injury (HSI) at time of injury (TOI), return to sport (RTS), and 12 weeks after RTS (12wks).

METHODS

This observational, prospective, cross-sectional design included male and female collegiate athletes who sustained an HSI. SWS imaging was performed at TOI, RTS, and 12wks with magnetic resonance imaging. SWS maps were acquired by a musculoskeletal-trained sonographer at the injury location of the injured limb and location-matched on the contralateral limb. The average SWS from three 5 mm diameter Q-boxes on each limb were used for analysis. A linear mixed effects model was performed to determine differences in SWS between limbs across the study time points.

RESULTS

SWS was lower in the injured limb compared to the contralateral limb at TOI (uninjured - injured limb difference: 0.23 [0.05, 0.41] m/s, p = 0.006). No between-limb differences in SWS were observed at RTS (0.15 [-0.05, 0.36] m/s, p = 0.23) or 12wks (-0.11 [-0.41, 0.18] m/s, p = 0.84).

CONCLUSIONS

The SWS in the injured limb of collegiate athletes after HSI was lower compared to the uninjured limb at TOI but not at RTS or 12 weeks after RTS.

CRITICAL RELEVANCE STATEMENT

Hamstring strain injury with structural disruption can be detected by lower injured limb shear wave speed compared to the uninjured limb. Lack of between-limb differences at return to sport may demonstrate changes consistent with healing. Shear wave speed may complement traditional ultrasound or MRI for monitoring muscle injury.

KEY POINTS

• Ultrasound shear wave speed can non-invasively measure tissue elasticity in muscle injury locations. • Injured limb time of injury shear wave speeds were lower versus uninjured limb but not thereafter. • Null return to sport shear wave speed differences may correspond to structural changes associated with healing. • Shear wave speed may provide quantitative measures for monitoring muscle elasticity during recovery.

Automated recognition of the major muscle injury in athletes on X-ray CT images1

BACKGROUND

In this research, imaging techniques such as CT and X-ray are used to locate important muscles in the shoulders and legs. Athletes who participate in sports that require running, jumping, or throwing are more likely to get injuries such as sprains, strains, tendinitis, fractures, and dislocations. One proposed automated technique has the overarching goal of enhancing recognition.

OBJECTIVE

This study aims to determine how to recognize the major muscles in the shoulder and leg utilizing X-ray CT images as its primary diagnostic tool.

METHODS

Using a shape model, discovering landmarks, and generating a form model are the steps necessary to identify injuries in key shoulder and leg muscles. The method also involves identifying injuries in significant abdominal muscles. The use of adversarial deep learning, and more specifically Deep-Injury Region Identification, can improve the ability to identify damaged muscle in X-ray and CT images.

RESULTS

Applying the proposed diagnostic model to 150 sets of CT images, the study results show that Jaccard similarity coefficient (JSC) rate for the procedure is 0.724, the repeatability is 0.678, and the accuracy is 94.9% respectively.

CONCLUSION

The study results demonstrate feasibility of using adversarial deep learning and deep-injury region identification to automatically detect severe muscle injuries in the shoulder and leg, which can enhance the identification and diagnosis of injuries in athletes, especially for those who compete in sports that include running, jumping, and throwing.

Managing Lower Limb Muscle Reinjuries in Athletes: From Risk Factors to Return-to-Play Strategies

Muscle injuries and subsequent reinjuries significantly impact athletes, especially in football. These injuries lead to time loss, performance impairment, and long-term health concerns. This review aims to provide a comprehensive overview of the current understanding of muscle reinjuries, delving into their epidemiology, risk factors, clinical management, and prevention strategies. Despite advancements in rehabilitation programs and return-to-play criteria, reinjury rates remain alarmingly high. Age and previous muscle injuries are nonmodifiable risk factors contributing to a high reinjury rate. Clinical management, which involves accurate diagnosis, individualized rehabilitation plans, and the establishment of return-to-training and return-to-play criteria, plays a pivotal role during the sports season. Eccentric exercises, optimal loading, and training load monitoring are key elements in preventing reinjuries. The potential of artificial intelligence (AI) in predicting and preventing reinjuries offers a promising avenue, emphasizing the need for a multidisciplinary approach to managing these injuries. While current strategies offer some mitigation, there is a pressing need for innovative solutions, possibly leveraging AI, to reduce the incidence of muscle reinjuries in football players. Future research should focus on this direction, aiming to enhance athletes' well-being and performance.

Traumatic muscle injury

Traumatic muscle injury represents a collection of skeletal muscle pathologies caused by trauma to the muscle tissue and is defined as damage to the muscle tissue that can result in a functional deficit. Traumatic muscle injury can affect people across the lifespan and can result from high stresses and strains to skeletal muscle tissue, often due to muscle activation while the muscle is lengthening, resulting in indirect and non-contact muscle injuries (strains or ruptures), or from external impact, resulting in direct muscle injuries (contusion or laceration). At a microscopic level, muscle fibres can repair focal damage but must be completely regenerated after full myofibre necrosis. The diagnosis of muscle injury is based on patient history and physical examination. Imaging may be indicated to eliminate differential diagnoses. The management of muscle injury has changed within the past 5 years from initial rest, immobilization and (over)protection to early activation and progressive loading using an active approach. One challenge of muscle injury management is that numerous medical treatment options, such as medications and injections, are often used or proposed to try to accelerate muscle recovery despite very limited efficacy evidence. Another challenge is the prevention of muscle injury owing to the multifactorial and complex nature of this injury.

Complete Distal Rupture of the Rectus Femoris in an Elite Football Player: A Non-operative Treatment

Although muscle injuries represent the most frequent injury in professional football, isolated complete distal ruptures of the rectus femoris (RF) muscle are rare, and there is no consensus on their treatment and return to play (RTP). In this article, we report a clinical case of successful non-surgical management of an RF grade 4c muscle injury in a professional football player, in which the athlete was able to RTP 21 weeks after the injury, had no re-injury >1 year after RTP, and is playing at an elite level in the Portuguese Football First League.

Indirect Rectus Femoris Injury Mechanisms in Professional Soccer Players: Video Analysis and Magnetic Resonance Imaging Findings

OBJECTIVE

To describe injury mechanisms and magnetic resonance imaging (MRI) findings in acute rectus femoris (RF) injuries of soccer players using a systematic video analysis.

DESIGN

Descriptive case series study of consecutive RF injuries from November 2017 to July 2022.

SETTING

Two specialized sports medicine hospitals.

PARTICIPANTS

Professional male soccer players aged between 18 and 40 years, referred for injury assessment within 7 days after a RF injury, with an available video footage of the injury and a positive finding on an MRI.

INDEPENDENT VARIABLES

Rectus femoris injury mechanisms (specific scoring based on standardized models) in relation to RF muscle injury MRI findings.

MAIN OUTCOME MEASURES

Rectus femoris injury mechanism (playing situation, player/opponent behavior, movement, and biomechanics), location of injury in MRI.

RESULTS

Twenty videos of RF injuries in 19 professional male soccer players were analyzed. Three different injury mechanisms were seen: kicking (80%), sprinting (10%), and change of direction (10%). Isolated single-tendon injuries were found in 60% of the injuries. Of the kicking injuries, 62.5% included complete tendon ruptures, whereas both running injuries and none of the change of direction injuries were complete ruptures. The direct tendon was involved in 33% of the isolated injuries, and the common tendon was affected in all combined injuries.

CONCLUSIONS

Rectus femoris injuries typically occur during kicking among football players. Most of the RF injuries involve a complete rupture of at least one tendon. Kicking injuries can also affect the supporting leg, and sprinting can cause a complete tendon rupture, whereas change of direction seems not to lead to complete ruptures.

Low Back Pain and Its Risk Factors Among Nurses Working in East Bale, Bale, and West Arsi Zone Government Hospitals, Oromia Region, South East Ethiopia, 2021 -Multicenter Cross-Sectional Study

Background

Hospital nursing staff are particularly susceptible to low back pain (LBP) a widespread health issue worldwide. There was little available data on the prevalence of LBP and risk factors related to it in this population.

Objective

Assessed the prevalence of LBP and risk factors in nurses working in South-East Ethiopia's Oromia region in the East Bale, Bale, and West Arsi zone government hospitals.

Methods

A cross-sectional study was carried out within an institution in the East Bale, Bale, and West Arsi zone government hospitals; 440 nurses were chosen to use a process of systematic random sampling, and data was gathered between June 1 and July 30, 2021. Using pre-designed questionnaires, I interrogated participants. After being verified as complete, the gathered data was entered into Epi-data version 3.1 and exported to SPSS version 25 for analysis. Bi variate and multivariate logistic regressions with 95% confidence intervals and crude and adjusted odd ratios were generated and interpreted as necessary. To deem a result statistically significant, a p-value of 0.05 or lower was required.

Results

A total of 427 nurses engaged in the interview out of the 440 participants that wanted to take part in the study, yielding a response rate of 97.1%. Low back pain was 42.6% more common over a year [95% CI: (0.384, 0.476)]. According to the multivariate analysis, females [AOR = 1.791; 95% CI: (1.121, 2.861)], age higher than forty [AOR=2.388, 95% CI: (1.315, 4.337)], age grouped 31-40 years [(AOR=2.064, 95% CI: 1.233, 3.455)], divorced [(AOR=10.288, 95% CI: (3.063, 34.553)], married [(AOR=1.676 (1.675, 16.999)].

Conclusion

The study suggests that implementing preventive measures and offering ergonomic training can help reduce LBP among nurses in these hospitals.

Association Between Magnetic Resonance Imaging Findings and Time to Return to Sport After Muscle Injuries in High-Level Youth Athletes

OBJECTIVE

To describe the relationship between magnetic resonance imaging (MRI) findings and time to return to sport (RTS) from muscle injuries in youth athletes.

DESIGN

Prospective collection of injury surveillance data over 6 seasons (2014-2015 to 2019-2020) and reanalysis of MRIs by a radiologist blinded to RTS time after the data collection period.

SETTING

National sports academy and sports medicine hospital.

PARTICIPANTS

Male youth (11-19 years) athletes participating in the football (soccer) or athletics (track and field) programs with a muscle injury.

INDEPENDENT VARIABLES

Magnetic resonance imaging findings (eg, grade and location) in time-loss muscle injuries.

MAIN OUTCOME VARIABLES

Injury incidence, distributions, and RTS time.

RESULTS

In total, 353 time-loss muscle injuries were recorded for 1089 athlete-seasons, of which 85 satisfied our inclusion criteria (MRI within 14 days). Return to sport time was significantly longer for reinjuries compared with index injuries. Associations between MRI findings and RTS time were specific to the muscle group, with significant differences in RTS time observed between categories of structure, location, and grade. The largest number of injuries was to the hamstrings (n = 46), where injuries involving the tendon were more severe than those involving the myotendinous junction and muscle, proximal injuries were more severe than mid-portion and distal, and longer RTS time was observed for higher injury grade ( P < 0.05).

CONCLUSIONS

Muscle injuries in youth are diverse and cannot be treated as a single injury type. Specific injury durations can be expected depending on injury characteristics such as reinjury, location, structure, and grade.

London International Consensus and Delphi study on hamstring injuries part 1: classification

Muscle injury classification systems for hamstring injuries have evolved to use anatomy and imaging information to aid management and prognosis. However, classification systems lack reliability and validity data and are not specific to individual hamstring muscles, potentially missing parameters vital for sport-specific and activity-specific decision making. A narrative evidence review was conducted followed by a modified Delphi study to build an international consensus on best-practice decision-making for the classification of hamstring injuries. This comprised a digital information gathering survey to a cohort of 46 international hamstring experts (sports medicine physicians, physiotherapists, surgeons, trainers and sports scientists) who were also invited to a face-to-face consensus group meeting in London . Fifteen of these expert clinicians attended to synthesise and refine statements around the management of hamstring injury. A second digital survey was sent to a wider group of 112 international experts. Acceptance was set at 70% agreement. Rounds 1 and 2 survey response rates were 35/46 (76%) and 99/112 (88.4%) of experts responding. Most commonly, experts used the British Athletics Muscle Injury Classification (BAMIC) (58%), Munich (12%) and Barcelona (6%) classification systems for hamstring injury. Issues identified to advance imaging classifications systems include: detailing individual hamstring muscles, establishing optimal use of imaging in diagnosis and classification, and testing the validity and reliability of classification systems. The most used hamstring injury classification system is the BAMIC. This consensus panel recommends hamstring injury classification systems evolve to integrate imaging and clinical parameters around: individual muscles, injury mechanism, sporting demand, functional criteria and patient-reported outcome measures. More research is needed on surgical referral and effectiveness criteria, and validity and reliability of classification systems to guide management.

Phase angle in localized bioimpedance measurements to assess and monitor muscle injury

Localized bioimpedance (L-BIA) measurements are an innovative method to non-invasively identify structural derangement of soft tissues, principally muscles, and fluid accumulation in response to traumatic injury. This review provides unique L-BIA data demonstrating significant relative differences between injured and contralateral non-injured regions of interest (ROI) associated with soft tissue injury. One key finding is the specific and sensitive role of reactance (Xc), measured at 50 kHz with a phase-sensitive BI instrument, to identify objective degrees of muscle injury, localized structural damage and fluid accretion, determined using magnetic resonance imaging. The predominant effect of Xc as an indicator of severity of muscle injury is highlighted in phase angle (PhA) measurements. Novel experimental models utilizing cooking-induced cell disruption, saline injection into meat specimens, and measurements of changing amounts of cells in a constant volume provide empirical evidence of the physiological correlates of series Xc as cells in water. Findings of strong associations of capacitance, computed from parallel Xc (X_CP), with whole body counting of 40-potassium and resting metabolic rate support the hypothesis that parallel Xc is a biomarker of body cell mass. These observations provide a theoretical and practical basis for a significant role of Xc, and hence PhA, to identify objectively graded muscle injury and to reliably monitor progress of treatment and return of muscle function.

Imaging of Muscle Injuries

Ultrasound (US) and MR imaging are the most common imaging modalities used to assess sports muscle injuries. The site of the muscle injury can be located at the peripheral aspect of the muscle (myofascial), within the muscle belly (musculotendinous), and with tendon involvement (intratendinous). Tears that affect the intramuscular tendon have a worse prognosis in terms of recovery time. US is an excellent method to evaluate muscle injuries, with high spatial and contrast resolution. MR imaging can be reserved for evaluation of professional athletes, surgical planning, differential diagnosis, and assessment of deep located and proximal muscle groups.

Risk Factors for Injury in CrossFit®-A Retrospective Analysis

CrossFit^® is a physical activity program and sport which is based on functional movements performed at high intensity and with high variability of exercises. It develops all motor skills. The study included 424 athletes (266 men and 158 women) from twelve centers in Poland, actively practicing CrossFit^® between 18 and 60 years of age. A questionnaire consisting of 25 questions was used, which was divided into four subsections concerning the characteristics of the sample, training routine, injuries, and information about environment. In total, 48% of respondents participating in the study suffered at least one injury during their entire training history. The injuries suffered most often involved shoulder joint and lumbar spine. Men were found to face a higher risk of injury than women, at 32.78% vs. 15.33% (p = 0.027). The shorter the training period, the smaller the number of injuries observed among the trainees. It was also noted that the shorter the training period, the lower the number of injuries that occurred (p = 0.041). An increase in the number of training sessions per week did not increase the incidence of injuries (p > 0.05). Performing isometric exercises during warm-up reduced the likelihood of injury during CrossFit^® training itself (p = 0.012). Training despite of concomitant acute pain had a significant adverse effect on the incidence of injuries (p = 0.002). The most common risk factors for injury in the CrossFit^® training process include, in particular: gender, training experience, and length of training sessions. Proper warm-up including isometric exercises and training conducted without accompanying pain symptoms reduces the risk of injury.

Isolated Adductor Magnus Injuries in Athletes: A Case Series

Background

Little is known about injuries to the adductor magnus (AM) muscle and how to manage them.

Purpose

To describe the injury mechanisms of the AM and its histoarchitecture, clinical characteristics, and imaging features in elite athletes.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 11 competitive athletes with an AM injury were included in the study. Each case was clinically assessed, and the diagnosis and classification were made by magnetic resonance imaging (MRI) according to the British Athletics Muscle Injury Classification (BAMIC) and mechanism, location, grade, and reinjury (MLG-R) classification. A 1-year follow-up was performed, and return-to-play (RTP) time was recorded.

Results

Different mechanisms of injury were found; most of the athletes (10/11) had flexion and internal rotation of the hip with extension or slight flexion of the knee. Symptoms consisted of pain in the posteromedial (7/11) or medial (4/11) thigh during adduction and flexion of the knee. Clinically, there was a suspicion of an injury to the AM in only 3 athletes. According to MRI, 5 lesions were located in the ischiocondylar portion (3 in the proximal and 2 in the distal myoconnective junction) and 6 in the pubofemoral portion (4 in the distal and 2 in the proximal myoconnective junction). Most of the ischiocondylar lesions were myotendinous (3/5), and most of the pubofemoral lesions were myofascial (5/6). The BAMIC and MLG-R classification coincided in distinguishing injuries of moderate and mild severity. The management was nonoperative in all cases. The mean RTP time was 14 days (range, 0-35 days) and was longer in the ischiocondylar cases than in the pubofemoral cases (21 vs 8 days, respectively). Only 1 recurrence, at <10 months, was recorded.

Conclusion

Posteromedial thigh pain after an eccentric contraction during forced adduction of the thigh from hip internal rotation should raise a suspicion of AM lesions. The identification of the affected portion was possible on MRI. An injury in the ischiocondylar portion entailed a longer RTP time than an injury in the pubofemoral portion.

Imaging of common hip pathologies in runners

Running is an increasingly popular sport and form of exercise. Because of the importance of the hip in the biomechanics involved with running, forming the primary connection between the axial and appendicular skeleton of the lower extremities, accurate diagnosis and reporting of hip pathology are vital for appropriate management. This review provides an overview of the most common hip pathologies and injuries encountered in runners. Radiologic studies, primarily conventional radiography and magnetic resonance imaging (MRI) provide useful diagnostic information and should be used in combination with clinical findings to help guide therapeutic management.

MRI findings prior to return to play as predictors of reinjury in professional athletes: a novel decision-making tool

BACKGROUND

Because MRI has shown great accuracy in assessing acute muscle injuries, identification of risk factors for reinjury before return to play (RTP) in professional athletes during the healing process could be very relevant. We assessed the value of MRI findings prior to RTP as predictors of reinjury.

METHODS

Retrospective observational study of 59 professional athletes, mean age 26 years, with first-time acute muscle injury and successful rehabilitation ready to RTP. They underwent MRI within 6 days of the injury and within 7 days prior to RTP. The primary outcome was reinjury. Risk of reinjury was assessed using radiological signs in control MRI scans before RTP. The risk was classified as low, medium or high when none, one or two radiological signs were observed, respectively.

RESULTS

Reinjury occurred in 9 participants, with a rate of 15.2%. None of the baseline MRI-related variables was significantly associated with reinjury. In the control MRI scan performed within 7 days prior to RTP, three independent findings were significantly associated with reinjury. These included transversal and/or mixed connective tissue gap (p = 0.002), intermuscular oedema (p = 0.015) and callus gap (p = 0.046). In the predictive model of the risk of reinjury, the presence of two of these radiological signs, together with interstitial feathery oedema, was associated with a high risk of recurrence (OR 29.58, 95% CI 3.86-226.64; p = 0.001).

CONCLUSIONS

In professional athletes with acute muscle injuries of the lower limbs successfully rehabilitated, some radiological signs on MRI performed shortly before RTP were associated with a high risk of reinjury.

An experimental model of contusion injury in humans

INTRODUCTION

Contusion injuries are common in sport, but our knowledge of the responses to injury primarily come from animal studies and research using eccentric exercise. Therefore, the aim of this study was to develop a model of contusion injury in human participants and, additionally, investigate and compare physiological responses to four impact loads.

METHODS

Thirty-two males were exposed to a single impact of either 4.2, 5.2, 6.2 or 7.2kg, dropped from 67 cm, on to the vastus lateralis of one leg. Maximum voluntary and electrically induced quadriceps force, and pressure pain threshold were measured, and blood sampling carried out, prior to and 30min, 24, 48 and 72h post-impact. Magnetic resonance imaging was carried out 24h post-impact to quantify oedema.

RESULTS

Despite impact force with 7.2kg (1681.4 ± 235.6 N) not being different to 6.2kg (1690.7 ± 117.6 N), 7.2kg resulted in greater volume of oedema, voluntary force loss, pain and elevations in creatine kinase than the other loads. Although electrically induced force changed over time, post-hoc analysis failed to identify any changes. Interleukin-6 and prostaglandin-E2 did not change over time for any of the loads. Significant correlations were found between oedema volume, pressure pain threshold and maximum voluntary contraction force.

CONCLUSIONS

This is the first experimental study to investigate traumatic loading of skeletal muscle and the subsequent physiological responses associated with contusion injuries in humans. The absence of immediate elevations in creatine kinase and changes in electrically induced force suggest impact, with forces similar to those experienced in contact sport, does not cause significant, direct damage to skeletal muscle. However, the relationship between oedema volume, changes in pressure pain threshold and maximum voluntary contraction force suggests central inhibition plays a role in contusion-related muscle dysfunction.

Sport-Specific Rehabilitation, but Not PRP Injections, Might Reduce the Re-Injury Rate of Muscle Injuries in Professional Soccer Players: A Retrospective Cohort Study

Platelet-rich plasma (PRP) injections are extremely popular in the management of sports injuries in elite athletes. However, data on the use of various administration protocols of PRP are contradictory. The efficacy of platelet-rich plasma in the treatment of muscle injuries in professional soccer players has to be contextualized within the sport-specific rehabilitation program. Despite the questionable role of PRP, a well-structured rehabilitation program is still regarded as the gold standard. We examined the efficacy of various PRP protocols in the management of muscle injuries in professional soccer players in respect to treatment duration and injury recurrence. A retrospective cohort study. Muscle injuries in professional soccer players (n = 79, height 182.1 ± 5.9 cm, weight 76.8 ± 5.8 kg, BMI 23.1 ± 1.4 kg/m2) from three elite soccer clubs from the Russian Premier League were recorded during the 2018−2019 season. The injuries were graded based on MRI, using the British Athletic Muscle Injury Classification. Treatment protocols included the POLICE regimen, short courses of NSAID administration, and the specific rehabilitation program. The sample group of players were administered PRP injections. The average treatment duration with PRP injection was significantly longer than conventional treatment without PRP, 21.5 ± 15.7 days and 15.3 ± 11.1 days, respectively (p = 0.003). Soccer-specific rehabilitation and obtaining MRI/US before the treatment was associated with significantly reduced injury recurrence rate (p < 0.001). There was no significant difference between the PRP injection protocol applied to any muscle and the treatment duration in respect of grade 2A−2B muscle injuries. The total duration of treatment of type 2A−2B injuries was 15 days among all players. In the group receiving local injections of PRP, the total duration of treatment was 18 days; in the group without PRP injections, the treatment duration was 14 days. In our study, PRP treatment was associated with longer treatment duration, regardless of which muscle was injured. This may reflect the tendency to use PRP in higher-degree injuries. Soccer-specific rehabilitation significantly reduced the injury recurrence rate when compared to the administration of PRP injections. MRI/US imaging before returning to play was also associated with a lower injury recurrence rate. There was no significant difference between the PRP injection protocol applied to any muscle and the treatment duration in treatment of type 2A−2B muscle injuries.

Electroacupuncture of Weizhong (BL-40) Acupoint Inspires Muscular Satellite Cell Regeneration and Promotes Muscle Repair Capacity after Back Muscle Injury in Sprague-Dawley Rat Model

Background

Back muscle injury is the most common illness involved in aged people. Muscular satellite cells, playing a key role in the muscle repairing process, are gradually losing their regenerative ability with aging, which attenuates the injured muscle repairing process. Electroacupuncture at Weizhong acupoint has been widely used in the treatment of young and aged patients with back muscle damage. Its efficacy has been proven by a randomized double-blind placebo clinical trial. However, the rehabilitation mechanisms are largely unknown. This study will explore the possible mechanisms associated with electroacupuncture at the Weizhong acupoint (BL 40) promoting muscle repairing ability.

Method

A total of 58 male and female Sprague-Dawley rats were divided into a younger group (4-month-old) and an aged group (16-month-old), younger and aged rats were further divided as a sham, injured, injured rats treated with electroacupuncture at Weizhong point or treated with Non-Weizhong point groups. The back muscle injury model was produced in rats as a previously described method with modification. Furthermore, Weizhong acupoints underwent electroacupuncture treatment with 15 V magnitude, 2 Hz/10 Hz frequency density, 1.0 mA current intensity, and 10 min each day for 10 consecutive days using HANS's electroacupuncture apparatus. After the last treatment, the paravertebral muscles and serum of all animals were undergone histological, immunohistochemistry, and flow cytometry analysis. Serum levels of Creatine Kinase (CK) and proinflammatory cytokine, interleukin 6 (IL-6), were measured separately by using ELISA kit.

Results

Electroacupuncture of Weizhong (BL 40) acupoints significantly attenuated back muscle damage in both young and aged rats, increasing PAX7 (a marker of muscle satellite cells) and MYOD (major marker of myoblasts) cells, simultaneously, reducing serum proinflammatory cytokines, IL-6, and downregulation of p38 MAPK signaling in aged muscular satellite cells.

Conclusion

Our studies suggest that electroacupuncture of Weizhong (BL 40) acupoints can restore aged back muscular satellite cells and their regeneration capacity. These suggested electroacupuncture may be a potential means of promoting rehabilitation for muscular injury in aged patients.

Return to Play Prediction Accuracy of the MLG-R Classification System for Hamstring Injuries in Football Players: A Machine Learning Approach

BACKGROUND AND OBJECTIVE

Muscle injuries are one of the main daily problems in sports medicine, football in particular. However, we do not have a reliable means to predict the outcome, i.e. return to play from severe injury. The aim of the present study was to evaluate the capability of the MLG-R classification system to grade hamstring muscle injuries by severity, offer a prognosis for the return to play, and identify injuries with a higher risk of re-injury. Furthermore, we aimed to assess the consistency of our proposed system by investigating its intra-observer and inter-observer reliability.

METHODS

All male professional football players from FC Barcelona, senior A and B and the two U-19 teams, with injuries that occurred between February 2010 and February 2020 were reviewed. Only players with a clinical presentation of a hamstring muscle injury, with complete clinic information and magnetic resonance images, were included. Three different statistical and machine learning approaches (linear regression, random forest, and eXtreme Gradient Boosting) were used to assess the importance of each factor of the MLG-R classification system in determining the return to play, as well as to offer a prediction of the expected return to play. We used the Cohen's kappa and the intra-class correlation coefficient to assess the intra-observer and inter-observer reliability.

RESULTS

Between 2010 and 2020, 76 hamstring injuries corresponding to 42 different players were identified, of which 50 (65.8%) were grade 3^r, 54 (71.1%) affected the biceps femoris long head, and 33 of the 76 (43.4%) were located at the proximal myotendinous junction. The mean return to play for grades 2, 3, and 3^r injuries were 14.3, 12.4, and 37 days, respectively. Injuries affecting the proximal myotendinous junction had a mean return to play of 31.7 days while those affecting the distal part of the myotendinous junction had a mean return to play of 23.9 days. The analysis of the grade 3^r biceps femoris long head injuries located at the free tendon showed a median return to play time of 56 days while the injuries located at the central tendon had a shorter return to play of 24 days (p = 0.038). The statistical analysis showed an excellent predictive power of the MLG-R classification system with a mean absolute error of 9.8 days and an R-squared of 0.48. The most important factors to determine the return to play were if the injury was at the free tendon of the biceps femoris long head or if it was a grade 3^r injury. For all the items of the MLG-R classification, the intra-observer and inter-observer reliability was excellent (k > 0.93) except for fibres blurring (κ = 0.68).

CONCLUSIONS

The main determinant for a long return to play after a hamstring injury is the injury affecting the connective tissue structures of the hamstring. We developed a reliable hamstring muscle injury classification system based on magnetic resonance imaging that showed excellent results in terms of reliability, prognosis capability and objectivity. It is easy to use in clinical daily practice, and can be further adapted to future knowledge. The adoption of this system by the medical community would allow a uniform diagnosis leading to better injury management.

Tensiomyography Allows to Discriminate between Injured and Non-Injured Biceps Femoris Muscle

The hamstring muscle group is the most frequently injured muscle group in non-contact muscle injuries in sports involving high-speed running. A total of 84% of hamstring injuries affect the biceps femoris (BF) muscle. Clinical assessments and magnetic resonance imaging (MRI) are routinely used for diagnosis and plan management. MRI-negative scans for clinically diagnosed hamstring injuries range from 14% to 45%. We tested the hypothesis that the functional differences between injured and non-injured BF assessed by tensiomyography can be used for diagnostic and classification purposes. We compared an injured group of 53 international-level soccer players and sprinters with 53 non-injured international-level soccer players and sprinters of both sexes. Comparing the injured vs. non-injured athletes and the left vs. right side in all of the athletes, we used the percentage of absolute differences in the BF contraction time (Tc) to classify non-injured and injured BF muscles. The receiver operating characteristic (ROC) curve and the area under the curve (AUC) and the precision−recall curve (PRC) were used to measure the classification accuracy and to identify cut-off limits using the Tc differences. There was a very high ROC AUC value of 0.981 (SE = 0.009, p < 0.000), with 98.11% of the injured muscles being correctly classified (cut-off point 12.50% on Tc differences), and an AUPRC value of 0.981, with association classification criteria at >9.87. Tensiomyography has a high predictive ability to discriminate between injured and non-injured BF non-invasively and functionally.

Hamstrings injuries in football

Background

Hamstrings injuries are a major concern in football (soccer), affecting both recreational players and professional athletes. Although being a recognized issue within the football community, its incidence has been increasing over the last years and still poses a challenge to all practitioners involved.

Study objectives and rationale

The goal of this narrative review is to outline hamstrings injuries epidemiology and mechanisms of injury, identify and discuss its risk factors, provide an approach to a proper early diagnosis, evaluate the efficacy of current treatment options and return to sports, and present the best strategies for hamstrings injury prevention. These guidelines will help the sports medicine staff team on how to better manage their players with or at risk of hamstrings injuries.

Conclusion

Despite several breakthroughs in research of hamstrings injuries, there is still heterogeneity across studies and lack of consensus in regards to classification, diagnosis, treatment and prevention. Hamstrings injuries compromise the athlete's performance with time loss due to injury, shortens their highest-level career longevity with higher risk of reinjury rates, and is a defying problem for clubs to balance financial losses due to having their players off the pitch. Further research is warranted to keep moving forward with evidence on treating and preventing hamstrings injuries to mitigate its high incidence and keep the players safe.

Lesão muscular: Fisiopatologia, diagnóstico e tratamento

O tecido muscular esquelético possui a maior massa do corpo humano, correspondendo a 45% do peso total. As lesões musculares podem ser causadas por contusões, estiramentos ou lacerações. A atual classificação separa as lesões entre leves, moderadas e graves. Os sinais e sintomas das lesões grau I são edema e desconforto; grau II, perda de função, gap e equimose eventual; grau III, rotura completa, dor intensa e hematoma extenso. O diagnóstico pode ser confirmado por ultrassom (dinâmico e barato, porém examinador-dependente); e ressonância magnética (RM) (maior definição anatômica). A fase inicial do tratamento se resume à proteção, ao repouso, ao uso otimizado do membro afetado e crioterapia. Anti-inflamatórios não hormonais (AINHs), ultrassom terapêutico, fortalecimento e alongamento após a fase inicial e amplitudes de movimento sem dor são utilizados no tratamento clínico. Já o cirúrgico possui indicações precisas: drenagem do hematoma, reinserção e reforço musculotendíneos.

Effects of ankle position during the Nordic Hamstring exercise on range of motion, heel contact force and hamstring muscle activation

One of the main benefits of the Nordic Hamstring Exercise (NHE) is that it can be performed without the need of any extra material. However, numerous technical execution variables such as the ankle and pelvis position can influence the performance. The primary aims of this study were to investigate the effects of ankle position (i.e., plantar or dorsal flexion) on Nordic Hamstring Break Point (NHBP), repetition time and heel contact force. A secondary aim was to investigate differences in biceps femoris long head and semitendinosus muscle activation. Male professional field hockey players (n = 12) volunteered for the study. Paired t-tests were used to analyse the effect of ankle position on muscle NHBP, eccentric peak torque and repetition time. Ankle dorsal flexion resulted in a higher NHBP (p = 0.002, effect size [ES] = 1.48 [0.57 to 2.38]), repetition time (p = 0.004, ES = 0.98 [0.24 to 1.72]) and both absolute and relative heel contact force (p = 0.028, ES = 0.67 [0.01 to 1.34], p = 0.017, ES = 0.76 [0.07 to 1.44], respectively) compared to plantar flexion. Muscle activation was not significant different. This study showed a higher NHBP, absolute and relative heel contact force and repetition time with a dorsal flexed ankle vs. a plantar flexed ankle in the NHE, without changes in hamstrings muscle activation.

[CME-Sonography 105: Ultrasound in Sports Injuries]

CME-Sonography 105: Ultrasound in Sports Injuries Abstract. Muscle injuries are frequent in athletes and in the general population. For therapy and prognosis, it is important to understand the total extent of the injury and to be aware of possible complications. In most cases ultrasound is a useful tool for diagnostics of muscle injuries. However, muscle ultrasound is not as common as joint ultrasound; this article discusses the possibilities of high-resolution dynamic ultrasound in diagnostics and its limitations.

Spatial frequency analysis detects altered tissue organization following hamstring strain injury at time of injury but not return to sport

Background

Hamstring strain injury (HSI) diagnosis is often corroborated using ultrasound. Spatial frequency analysis (SFA) is a quantitative ultrasound method that has proven useful in characterizing altered tissue organization. The purpose of this study was to determine changes in muscular tissue organization using SFA following HSI.

Methods

Ultrasound B-mode images were captured at time of injury (TOI) and return to sport (RTS) in collegiate athletes who sustained an HSI. Spatial frequency parameters extracted from two-dimensional Fourier Transforms in user-defined regions of interest (ROI) were analyzed. Separate ROIs encompassed injured and adjacent tissue within the same image of the injured limb and mirrored locations in the contralateral limb at TOI. The ROIs for RTS images were drawn to correspond to the injury-matched location determined from TOI imaging. Peak spatial frequency radius (PSFR) and the fascicular banded pattern relative to image background (Mmax%) were compared between injured and adjacent portions within the same image with separate paired t-tests. Within-image differences of SFA parameters in the injured limb were calculated and compared between TOI and RTS with Wilcoxon rank sum tests.

Results

Within the injured limb at TOI, PSFR differences in injured and healthy regions did not strictly meet statistical significance (p = 0.06), while Mmax% was different between regions (p < 0.001). No differences were observed between regions in the contralateral limb at TOI (PSFR, p = 0.16; Mmax%, p = 0.30). Significant within-image differences in PSFR (p = 0.03) and Mmax% (p = 0.04) at RTS were detected relative to TOI.

Conclusions

These findings are a first step in determining the usefulness of SFA in muscle injury characterization and provide quantitative assessment of both fascicular disruption and edema presence in acute HSI.

Intratendinous hamstring injuries: sequential MRIs as a tool to reduce the risk of reinjury in elite sport

Hamstring injuries are the most common muscle injuries in elite football. Injuries involving the intramuscular tendon are considered more significant, with longer return to play (RTP) times and an increased risk of reinjury. MRI is the gold standard investigation for muscle injuries, but initial findings cannot accurately determine RTP times. The role of MRI in monitoring muscle and tendon healing is not well described. We present three cases of hamstring injuries with intramuscular tendon involvement, illustrating the changes seen on MRI during progressive tendon healing and describing how we utilised this information to inform safe rehabilitation progression. We conclude that intramuscular hamstring tendon healing can be accurately seen on sequential MRI scans and that this information, when combined with traditional rehabilitation markers in and elite sport environment, can be utilised by clinicians to determine the earliest but safe RTP.

Electrical Impedance Myography in Health and Physical Exercise: A Systematic Review and Future Perspectives

Background: Electrical impedance myography (EIM) is a non-invasive method that provides information about muscle health and changes that occur within it. EIM is based on the analysis of three impedance variables: resistance, reactance, and the phase angle. This systematic review of the literature provides a deeper insight into the scope and range of applications of EIM in health and physical exercise. The main goal of this work was to systematically review the studies on the applications of EIM in health and physical exercise in order to summarize the current knowledge on this method and outline future perspectives in this growing area, including a proposal for a research agenda. Furthermore, some basic assessment principles are provided. Methods: Systematic literature searches on PubMed, Scopus, SPORTDiscus and Web of Science up to September 2020 were conducted on any empirical investigations using localized bioimpedance devices to perform EIM within health and physical exercise contexts. The search included healthy individuals, elite soccer players with skeletal muscle injury, and subjects with primary sarcopenia. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) checklist was used to develop the systematic review protocol. The quality and risk of bias of the studies included were assessed with the AQUA tool. Results: Nineteen eligible original articles were included in this review, which were separated into three tables according to the nature of the study. The first table includes six studies on the bioelectrical characterization of muscle. The second table includes five studies analyzing muscle changes in injured elite soccer players. The third table includes studies on the short-, medium-, and long-term bioelectrical adaptations to physical exercise. Conclusions: EIM has been used for the evaluation of the muscle condition in the clinical field over the last few years, especially in different neuromuscular diseases. It can also play an important role in other contexts as an alternative to complex and expensive methods such as magnetic resonance imaging. However, further research is needed. The main step in establishing EIM as a valid tool in the scientific field is to standardize the protocol for performing impedance assessments.

Ultrasound Imaging in Sport-Related Muscle Injuries: Pitfalls and Opportunities

Muscle injuries occur frequently in athletes, accounting for more than one-third of sport-related trauma. Athletes most affected by these injuries are those practicing football and track and field, with hamstrings and gastrocnemius-soleus as the mainly involved sites. Muscle injuries lead to loss of competitions, long recovery times and risk of re-injury with a consequent increase of the management costs. It is therefore advisable to make an accurate and timely diagnosis to establish appropriate interventions for proper healing in the shortest time. In this context, ultrasound imaging is widely used for diagnosis of musculoskeletal disorders because of several advantages including absence of radiation, portability, good spatial resolution, and the ability to perform dynamic tests. The aim of this review is to address the role of US in the evaluation of athletes with muscle injuries. US may play a pivotal role for the management of sport-related muscle injuries because it is fast and relatively cheap, allowing dynamic muscle assessment and time series evaluation of the healing process.

Indirect Structural Muscle Injuries of Lower Limb: Rehabilitation and Therapeutic Exercise

Muscle injuries are the most common trauma in team and individual sports. The muscles most frequently affected are those of the lower limb, and in particular hamstrings, adductors, rectus femoris and calf muscles. Although several scientific studies have tried to propose different rehabilitation protocols, still too often the real rehabilitation process is not based on scientific knowledge, especially in non-elite athletes. Moreover, the growing use of physical and instrumental therapies has made it increasingly difficult to understand what can be truly effective. Therefore, the aim of the present paper is to review proposed therapeutic algorithms for muscle injuries, proposing a concise and practical summary. Following a three-phase rehabilitation protocol, this review aims to describe the conservative treatment of indirect structural muscle injuries, which are the more routinely found and more challenging type. For each phase, until return to training and return to sport are completed, the functional goal, the most appropriate practitioner, and the best possible treatment according to current evidence are expressed. Finally, the last section is focused on the specific exercise rehabilitation for the four main muscle groups with a structured explanatory timetable.

Diagnostic performance of the Strength and Pain Assessment (SPA) score for non-contact muscle injury screening in male soccer players

OBJECTIVES

The aims of this study were to develop a clinical-feature based scoring system for muscle injury screening and to assess its diagnostic accuracy when large number of injuries are suspected.

METHODS

A prospective diagnostic accuracy study was performed according to the Standards for Reporting of Diagnostic Accuracy (STARD) criteria. The diagnostic accuracy of the Strength and Pain Assessment (SPA) score (index test) was assessed in relation to muscle ultrasonography (reference standard). A large (n = 175) number of male soccer players met the inclusion/exclusion criteria: clinical assessment (i.e., evaluation of pain onset modality, location, distribution, impact on performance, and manual muscle strength testing) and ultrasonography were performed in all players after 48 hours from the sudden or progressive onset of muscle pain during or after a soccer competition.

RESULTS

91 of 175 cases (52%) were classified as functional muscle disorders, while signs of muscle tear were observed in the remaining 84 of 175 (48%) cases that were classified as structural muscle injuries. The median (1st - 3rd quartile) value of the SPA score was significantly (P < 0.001) lower in the functional disorder group [9 (9-10)] compared to the structural injury group [12 (12-13)]. The area under the Receiver Operating Characteristic curve for different cutoff points of the SPA score was 0.977 (95% confidence intervals: 0.957-0.998) and the optimal cutoff value of the SPA score providing the greatest sensitivity and specificity (respectively, 99% and 89%) was 11.

CONCLUSION

This study found that the SPA score has high diagnostic accuracy for structural muscle injuries and could be used as a valid screening tool in soccer players presenting with sudden or progressive onset of muscle pain during or after a competition.

Update on sports imaging

Sports Imaging has dramatically increased in the past decade with increasing number of adolescents, young and middle-aged adults participating in non-competitive/hobby sports. Therefore, sports injuries are no longer confined to elite athletes. Furthermore, newer forms of sports such as mountain climbing, pickle ball and curling etc. are gaining popularity. Majority of the injuries in sports medicine are from musculoskeletal trauma. Therefore, it is imperative that the musculoskeletal radiologist becomes familiar with various sports related injury patterns as these are commonly encountered in daily practice. This update aims to briefly encapsulate the major aspects of sports imaging. It includes the imaging manifestations of various types of musculoskeletal injuries on different modalities (commonly US and MRI) and briefly mentions the various image guided interventions, performed both on the sports field and in the hospital setting.

Musculoskeletal Disorders' Classification Proposal for Application in Occupational Medicine

Occupational-specific classifications of musculoskeletal disorders (MSD) are scarce and do not answer specific clinical questions. Thus, a specific classification was developed and proposed, covering criteria applicable to daily clinical activity. It was considered that the disorder development process is the same across all work-related MSDs (WRMSDs). Concepts of clinical pathology were applied to the characteristics of WRMSDs pathophysiology, cellular and tissue alterations. Then, the correlation of the inflammatory mechanisms with the injury onset mode was graded into four levels (MSDs 0-3). Criteria of legal, occupational and internal medicine, semiology, physiology and orthopaedics, image medicine and diagnostics were applied. Next, the classification was analysed by experts, two occupational physicians, two physiatrists and occupational physicians and one orthopaedist. This approach will allow WRMSD prevention and improve therapeutic management, preventing injuries from becoming chronic and facilitating communication between occupational health physicians and the other specialities. The four levels tool relate aetiopathogenic, clinical, occupational and radiological concepts into a single classification. This allows for improving the ability to determine a WRMSD and understanding what preventive and therapeutic measures should be taken, avoiding chronicity. The developed tool is straightforward, easy to understand and suitable for WRMSDs, facilitating communication between occupational physicians and physicians from other specialities.

Neuromuscular fatigue and recovery after strenuous exercise depends on skeletal muscle size and stem cell characteristics

Hamstring muscle injury is highly prevalent in sports involving repeated maximal sprinting. Although neuromuscular fatigue is thought to be a risk factor, the mechanisms underlying the fatigue response to repeated maximal sprints are unclear. Here, we show that repeated maximal sprints induce neuromuscular fatigue accompanied with a prolonged strength loss in hamstring muscles. The immediate hamstring strength loss was linked to both central and peripheral fatigue, while prolonged strength loss was associated with indicators of muscle damage. The kinematic changes immediately after sprinting likely protected fatigued hamstrings from excess elongation stress, while larger hamstring muscle physiological cross-sectional area and lower myoblast:fibroblast ratio appeared to protect against fatigue/damage and improve muscle recovery within the first 48 h after sprinting. We have therefore identified novel mechanisms that likely regulate the fatigue/damage response and initial recovery following repeated maximal sprinting in humans.

Effects of Physical Agents on Muscle Healing with a Focus on Animal Model Research

Skeletal muscle injury is caused by a variety of events, such as muscle laceration, contusions, or strain. Muscle fibers respond to minor damage with immediate repair mechanisms that reseal the cell membrane. On the other hand, repair of irreversibly damaged fibers is achieved by activation of muscle precursor cells. Muscle repair is not always perfect, especially after severe damage, and can lead to excessive fibroblast proliferation that results in the formation of scar tissue within muscle fibers. Remaining scar tissue can impair joint movement, reduce muscular strength, and inhibit exercise ability; therefore, to restore muscle function, minimizing the extent of injury and promoting muscle regeneration are necessary. Various physical agents, such as cold, thermal, electrical stimulation, and low-intensity pulsed ultrasound therapy, have been reported as treatments for muscle healing. Although approaches based on the muscle regeneration process have been under development, the most efficacious physiological treatment for muscle injury remains unclear. In this review, the influence of these physical agents on muscle injury is described with a focus on research using animal models.

New Frontiers of Body Composition in Sport

The body composition phenotype of an athlete displays the complex interaction among genotype, physiological and metabolic demands of a sport, diet, and physical training. Observational studies dominate the literature and describe the sport-specific physique characteristics (size, shape, and composition) of adult athletes by gender and levels of competition. Limited data reveal how body composition measurements can benefit an athlete. Thus, the objective is to identify purposeful measurements of body composition, notably fat and lean muscle masses, and determine their impact on the health and performance of athletes. Areas of interest include relationships among total and regional body composition measurements, muscle function, sport-specific performance, risk of injury, return to sport after injury, and identification of activity-induced fluid shifts. Discussion includes the application of specific uses of dual X-ray absorptiometry and bioelectrical impedance including an emphasis on the need to minimize measurement errors and standardize protocols, and highlights opportunities for future research. This focus on functional body composition can benefit the health and optimize the performance of an athlete.