Hamstring muscle fibre typology is not associated with hamstring strain injury history or performance in amateur male soccer players: a retrospective magnetic resonance spectroscopy study.

Hamstring strain injuries (HSI) are still the most common injuries in soccer. Recent research has been focusing on the role of hamstring muscle morphology and architecture. The hamstring's fibre type composition might play a role as well, but this has never been investigated in the light of HSI risk in an athletic population. The purpose of this study was to investigate the association between hamstring muscle fibre type, hamstring strain injury history (HSIH), performance and isokinetic strength in a population of amateur male soccer players. In this cross-sectional observational study, 44 male soccer players (22 with and 22 without HSIH) participated. The research consisted of a non-invasive fibre composition evaluation using proton magnetic resonance spectroscopy (1H-MRS), functional performance (evaluated by means of maximal jumping height, maximal sprinting speed and hamstring muscle strength endurance (single leg hamstring bridge testing)), and isokinetic strength testing. The results revealed that hamstring carnosine concentration demonstrated a high inter-individual variability within this soccer population and was not significantly associated with either HSIH or with any of the functional performance parameters. The only secondary outcome measure presenting a significant association with the intramuscular carnosine content was the hamstrings' explosive strength production capacity, objectified by means of the time to peak torque (TPT), measured concentrically at an angular velocity of 240 degrees/second (°/s) during isokinetic strength testing. This TPT was significantly shorter in players presenting higher carnosine concentrations (p = 0.044). The findings indicate that in male amateur soccer players (1) the hamstrings have no distinct fibre type dominance and (2) fibre typology in this population does not relate to HSIH or performance.

Investigating the autoregulation of applied blood flow restriction training pressures in healthy, physically active adults: an intervention study evaluating acute training responses and safety.

OBJECTIVE: To examine the effects of autoregulated (AUTO) and non-autoregulated (NAUTO) blood flow restriction (BFR) application on adverse effects, performance, cardiovascular and perceptual responses during resistance exercise. METHODS: Fifty-six healthy participants underwent AUTO and NAUTO BFR resistance exercise in a randomised crossover design using a training session with fixed amount of repetitions and a training session until volitional failure. Cardiovascular parameters, rate of perceived effort (RPE), rate of perceived discomfort (RPD) and number of repetitions were investigated after training, while the presence of delayed onset muscle soreness (DOMS) was verified 24 hours post-session. Adverse events during or following training were also monitored. RESULTS: AUTO outperformed NAUTO in the failure protocol (p<0.001), while AUTO scored significantly lower for DOMS 24 hours after exercise (p<0.001). Perceptions of effort and discomfort were significantly higher in NAUTO compared with AUTO in both fixed (RPE: p=0.014, RPD: p<0.001) and failure protocol (RPE: p=0.028, RPD: p<0.001). Sixteen adverse events (7.14%) were recorded, with a sevenfold incidence in the fixed protocol for NAUTO compared with AUTO (NAUTO: n=7 vs AUTO: n=1) and five (NAUTO) vs three (AUTO) adverse events in the failure protocol. No significant differences in cardiovascular parameters were found comparing both pressure applications. CONCLUSION: Autoregulation appears to enhance safety and performance in both fixed and failure BFR-training protocols. AUTO BFR training did not seem to affect cardiovascular stress differently, but was associated with lower DOMS, perceived effort and discomfort compared with NAUTO. TRIAL REGISTRATION NUMBER: NCT04996680.

Extended reality in musculoskeletal rehabilitation and injury prevention - A systematic review.

OBJECTIVE: Unlike in neurological patient populations, the effects of Extended Reality within the context of sports medicine have rarely been studied. This systematic review was conducted to investigate the value of Extended Realty-assisted rehabilitation and injury prevention strategies on injury rehabilitation and prevention outcomes. METHODS: PubMed and Web of Science databases were consulted. The search strategy consisted of the terms Virtual Reality (Intervention), rehabilitation and injury prevention (Outcome) and healthy athletes or athletes with a musculoskeletal sports injury (Population). After eligibility and Risk of Bias screening, ten articles were included. Risk of Bias analysis resulted in a level of evidence varying between C (three articles), B (six articles) and A2 (one article) scores. RESULTS: Extended Reality was found to provide an added value for both sports injury prevention and rehabilitation outcomes. It particularly provides clinicians with the opportunity to address the underlying biomechanical risk profile for common sports injuries, allowing the athletes to train protective movement patterns more effectively. CONCLUSION: More large-scale high-quality prospective research is needed in order to determine whether Extended Reality-assisted therapy is superior to conventional therapy in sports rehabilitation and injury prevention circles with strong conclusive evidence.

Sports injury prevention programmes from the sports physical therapist's perspective: An international expert Delphi approach.

OBJECTIVE: To provide consensus on how to plan, organize and implement exercise-based injury prevention program (IPP) in sports. DESIGN: Delphi. SETTING: LimeSurvey platform. PARTICIPANTS: Experienced sports physical therapists from the International Federation of Sports Physical Therapy member countries. MAIN OUTCOME MEASURES: Factors related to sports IPP planning, organization and implementation. RESULTS: We included 305 participants from 32 countries. IPP planning should be based on an athlete's injury history, on pre-season screening results, and on injury rates (respectively, 98%, 92%, 89% agreement). In total 97% participants agreed that IPP organization should depend on the athlete's age, 93% on the competition level, and 93% on the availability of low-cost materials. It was agreed that IPP should mainly be implemented in warm-up sessions delivered by the head or strength/conditioning coach, with physical training sessions and individual physical therapy sessions (respectively, 94%, 92%, 90% agreement). CONCLUSION: Strong consensus was reached on (1) IPP based on the athlete's injury history, pre-season screening and evidence-based sports-specific injury rates; (2) IPP organization based on the athlete's age, competition level, and the availability of low-cost materials and (3) IPP implementation focussing on warm-up sessions implemented by the strength/conditioning coach, and/or individual prevention sessions by the physical therapist.

Association between SARS-COV-2 infection and muscle strain injury occurrence in elite male football players: a prospective study of 29 weeks including three teams from the Belgian professional football league.

OBJECTIVES: The aim of this study was to investigate the association between SARS-CoV-2 infection and muscle strain injury in elite athletes. METHODS: A prospective cohort study in three Belgian professional male football teams was performed during the first half of the 2020-2021 season (June 2020-January 2021). Injury data were collected using established surveillance methods. Assessment of SARS-CoV-2 infection was performed by a PCR test before each official game. RESULTS: Of the 84 included participants, 22 were infected with SARS-CoV-2 and 14 players developed a muscle strain during the follow-up period. Cox's proportional hazards regression analyses demonstrated a significant association between SARS-CoV-2 infection and the development of muscle strain (HR 5.1; 95% CI 1.1 to 23.1; p=0.037), indicating an increased risk of developing muscle strains following SARS-CoV-2 infection. All athletes who sustained a muscle strain after infection were injured within the first month (15.71±11.74 days) after sports resumption and completed a longer time in quarantine (14.57±6.50 days) compared with the infected players who did not develop a muscle strain (11.18±5.25 days). CONCLUSION: This study reported a five times higher risk of developing a muscle strain after a SARS-CoV-2 infection in elite male football players. Although this association should be examined further, it is possible that short-term detraining effects due to quarantine, and potentially pathological effects of the SARS-CoV-2 infection are associated with a higher risk of muscle strain injury.

The Effect of Aquabag Use on Muscle Activation in Functional Strength Training.

CONTEXT: Although training with an aquabag (AB) has gained popularity, there is a lack of evidence of its effect. This study wanted to evaluate the effect of AB implementation on muscle activity of core and lower limb muscles during 3 functional exercises. DESIGN: Cross-sectional observational study. METHODS: Twenty healthy subjects performed a squat, lunge, and step-up, while using a stick and an AB. Surface electromyography signals were recorded from the trunk, pelvis, and thigh muscles in the dominant leg. Linear-mixed models were used to analyze the normalized surface electromyography signals. RESULTS: Results demonstrated a significant increase in muscle activity of the back muscles during all 3 exercises (P < .001 to P = .003), abdominals during squat (P = .034) and step-up (P = .046), hamstrings during lunge (P = .008) and step-up (P = .008), and gluteal muscles during lunge (P < .001 and P = .010, respectively). CONCLUSIONS: These results indicate that an AB promotes functional strength training by demanding compensatory/additional activity of both stabilizing muscles (specifically in the core and pelvis regions) and prime movers of the lower limb. The authors recommend the use of an AB to enhance training and rehabilitation effects.

How injury prevention programs are being structured and implemented worldwide: An international survey of sports physical therapists.

OBJECTIVE: To identify the role of sports physical therapists (PT) in the injury prevention process and to compare the structure of preventive programs and associated (organization) policies applied in athletic organizations and sports teams of varying gender and level world-wide. DESIGN: cross-sectional study. SETTING: LimeSurvey platform. PARTICIPANTS: Sports PT working with athletes invited through the International Federation of Sports Physical Therapy. MAIN OUTCOME MEASURES: Sports injury prevention program (IPP) structure and implementation. RESULTS: 414 participants fully participate in this survey study. Athlete's injury history (68.84%), the most common injuries within the sport modality (67.87%) and athlete's preseason screening results (64.01%) were most frequently used to customize IPPs. Warm-up (70.04%) and individually PT-guided exercise-therapy (70.04%) were the preferred methods to organize the prevention routine. The main barrier for IPP implementation was lack of time within the athlete's weekly training schedule (66.66%). The majority of the participants (72.84%) reported to evaluate the perception of IPP's effect by comparing current and preceding seasons' injury occurrences. CONCLUSION: These survey results are the first identifying contemporary sports injury prevention organization and implementation policies on an international level. This information might support the sports PT community in improving and standardizing IPP (implementation) strategies worldwide.

How injury registration and preseason assessment are being delivered: An international survey of sports physical therapists.

OBJECTIVE: To identify the role of sports physical therapists (PT) in the organization of injury registration and preseason assessment, applied in athletic organizations and sports teams of different gender and level world-wide. DESIGN: cross-sectional study. SETTING: LimeSurvey platform. PARTICIPANTS: Sports PTs working with athletes invited through International Federation of Sports Physical Therapy. MAIN OUTCOME MEASURES: injury registration and athlete's screening. RESULTS: 414 sports PTs participated in this international survey (mean age of 37.66 (SD = 9.38) years). 340 participants indicated that the PT as the responsible for injury registration. Barriers to properly register injury throughout the season were indicated by 157 sports PT and 86 (54.77%) indicated a lack of time on their routine as the main factor. 93 participants (30.09%) indicated that they customize the prevention program based on the preseason assessment. Sports PTs who reported not performing a preseason assessment (92 participants - 22.22%) mainly indicated this to be consequence of lack of structure in the organization (44 participants - 47.82%). CONCLUSION: The majority of the sports PTs participate on injury registration and perform preseason assessment in athletes. However, lack of time in their routine and structure in the organization were recognized as the most important barriers to organize these properly.

Value of isokinetic strength testing for hamstring injury risk assessment: Should the 'strongest' mates stay ashore?

Although isokinetic strength testing is commonly used in hamstring strain injury (HSI) rehabilitation and prevention, research findings concerning its predictive value remain inconclusive. Existing research focuses on peak torque (PT) and angle of PT, not analysing the torque behaviour throughout the testing range of motion (ROM). This study intended to assess the value of isokinetic curve evaluation in association with HSI. A sample of 116 male football players with and without a recent HSI history was submitted to bilateral isokinetic assessment of the knee and hip muscles. Raw isokinetic data were filtered and normalized prior to curve analysis submission in MATLAB. Torque development of each muscle group throughout the entire testing ROM was assessed using HSI history as an independent variable. Curve analysis revealed significant differences in torque behaviour in function of injury history. Players with an HSI history demonstrated significantly stronger concentric knee flexion and extension, eccentric knee extension and concentric hip extension patterns compared to the controls and their uninjured limb. HSI history was also associated with lower concentric hip flexion torques and lower mixed H:Q ratios compared to the control group and their contralateral limb. HSI history was associated with altered knee and hip muscle strength profiles, potentially due to isolated focus on local strength training in rehabilitation or mechanisms of neuromuscular inhibition. Because the differences in torque amplitude were range-dependent and did not systematically concur with the point of PT achievement, isokinetic strength evaluation should most probably be conducted using curve analysis.

Return to Play After a Hamstring Strain Injury: It is Time to Consider Natural Healing.

Return to play (RTP) criteria after hamstring strain injuries (HSIs) help clinicians in deciding whether an athlete is ready to safely resume previous sport activities. Today, functional and sport-specific training tests are the gold standard in the decision-making process. These criteria lead to an average RTP time between 11 and 25 days after a grade 1 or 2 HSI. However, the high re-injury rates indicate a possible inadequacy of the current RTP criteria. A possible explanation for this could be the neglect of biological healing time. The present review shows that studies indicating time as a possible factor within the RTP-decision are very scarce. However, studies on biological muscle healing showed immature scar tissue and incomplete muscle healing at the average moment of RTP. Twenty-five percent of the re-injuries occur in the first week after RTP and at the exact same location as the index injury. This review supports the statement that functional recovery precedes the biological healing of the muscle. Based on basic science studies on biological muscle healing, we recommend a minimum period of 4 weeks before RTP after a grade 1 or 2 HSI. In conclusion, we advise a comprehensive RTP functional test battery with respect for the natural healing process. Before deciding RTP readiness, clinicians should reflect whether or not it is biologically possible for the injured tissue to have regained enough strength to withstand the sport-specific forces. In an attempt to reduce the detrimental injury-reinjury cycle, it is time to start considering (biological healing) time.

Biceps Femoris Compensates for Semitendinosus After Anterior Cruciate Ligament Reconstruction With a Hamstring Autograft: A Muscle Functional Magnetic Resonance Imaging Study in Male Soccer Players.

BACKGROUND: Rates of reinjury, return to play (RTP) at the preinjury level, and hamstring strain injuries in male soccer players after anterior cruciate ligament reconstruction (ACLR) remain unsatisfactory, due to multifactorial causes. Recent insights on intramuscular hamstring coordination revealed the semitendinosus (ST) to be of crucial importance for hamstring functioning, especially during heavy eccentric hamstring loading. Scientific evidence on the consequences of ST tendon harvest for ACLR is scarce and inconsistent. This study intended to investigate the repercussions of ST harvest for ACLR on hamstring muscle function. HYPOTHESIS: Harvest of the ST tendon for ACLR was expected to have a significant influence on hamstring muscle activation patterns during eccentric exercises, evaluated at RTP in a population of male soccer athletes. STUDY DESIGN: Controlled laboratory study. METHODS: A total of 30 male soccer players with a history of ACLR who were cleared for RTP and 30 healthy controls were allocated to this study during the 2018-2019 soccer season. The influence of ACLR on hamstring muscle activation patterns was assessed by comparing the change in T2 relaxation times [ΔT2 (%) = post-exercise-T2pre-exerciseT2pre-exercise] of the hamstring muscle tissue before and after an eccentric hamstring loading task between athletes with and without a recent history of ACLR through use of muscle functional magnetic resonance imaging, induced by an eccentric hamstring loading task between scans. RESULTS: Significantly higher exercise-related activity was observed in the biceps femoris (BF) of athletes after ACLR compared with uninjured control athletes (13.92% vs 8.48%; P = .003), whereas the ST had significantly lower activity (19.97% vs 25.32%; P = .049). Significant differences were also established in a within-group comparison of the operated versus the contralateral leg in the ACLR group (operated vs nonoperated leg: 14.54% vs 11.63% for BF [P = .000], 17.31% vs 22.37% for ST [P = .000], and 15.64% vs 13.54% for semimembranosus [SM] [P = .014]). Neither the muscle activity of SM and gracilis muscles nor total posterior thigh muscle activity (sum of exercise-related ΔT2 of the BF, ST, and SM muscles) presented any differences in individuals who had undergone ACLR with an ST tendon autograft compared with healthy controls. CONCLUSION: These findings indicate that ACLR with a ST tendon autograft might notably influence the function of the hamstring muscles and, in particular, their hierarchic dimensions under fatiguing loading circumstances, with increases in relative BF activity contribution and decreases in relative ST activity after ACLR. This between-group difference in hamstring muscle activation pattern suggests that the BF partly compensates for deficient ST function in eccentric loading. These alterations might have implications for athletic performance and injury risk and should probably be considered in rehabilitation and hamstring injury prevention after ACLR with a ST tendon autograft.

Worldwide Sports Injury Prevention.

The number one goal of the sports physical therapist is to make sure that the athlete is in optimal shape to perform, but with a minimal risk for developing an injury at the same time. The aim of this International Federation of Sports Physical Therapy (IFSPT) Perspective is to raise awareness about the importance of contextual and behavioral factors when planning and implementing injury prevention. Also, it outlines the potential role of the IFSPT as a facilitator of data and information exchange among sports physical therapists worldwide.

Neurodynamic sliders promote flexibility in tight hamstring syndrome.

ABSTRACT Hamstring injury prevention puts emphasis on optimizing the muscle's strength-length relationship. To assure appropriate muscle length, flexibility training is imperative. As neurodynamics play an important role herein, the goal of this study was to explore the intervention effect of home-based neurodynamic slider program on hamstring flexibility. Fifty physically active male subjects were randomly assigned to either performing a neurodynamic sliding technique (3 × 20 reps) or a static stretching protocol (3 × 30″) on a daily basis for a 6-week period. Hamstring flexibility was assessed by means of the Straight Leg Raise at baseline, immediately after the intervention and after 4 weeks follow up. There was no between group baseline difference in hamstring flexibility. The repeated measure ANOVA showed a significant interaction effect for group × time (p < 0.001). Independent sample t-test showed a significantly higher increase in flexibility gain in the neurodynamic group immediately after the intervention (p < 0.001), as well as at 4 weeks retention analysis (p = 0.001) compared to the static stretch group. In conclusion, neurodynamic sliders might be more efficient than regular static stretching in affecting hamstring flexibility in the long run.

Deviating running kinematics and hamstring injury susceptibility in male soccer players: Cause or consequence?

BACKGROUND: Although the vast majority of hamstring injuries in male soccer are sustained during high speed running, the association between sprinting kinematics and hamstring injury vulnerability has never been investigated prospectively in a cohort at risk. PURPOSE: This study aimed to objectify the importance of lower limb and trunk kinematics during full sprint in hamstring injury susceptibility. STUDY DESIGN: Cohort study; level of evidence, 2. METHODS: At the end of the 2013 soccer season, three-dimensional kinematic data of the lower limb and trunk were collected during sprinting in a cohort consisting of 30 soccer players with a recent history of hamstring injury and 30 matched controls. Subsequently, a 1.5 season follow up was conducted for (re)injury registry. Ultimately, joint and segment motion patterns were submitted to retro- and prospective statistical curve analyses for injury risk prediction. RESULTS: Statistical analysis revealed that index injury occurrence was associated with higher levels of anterior pelvic tilting and thoracic side bending throughout the airborne (swing) phases of sprinting, whereas no kinematic differences during running were found when comparing players with a recent hamstring injury history with their matched controls. CONCLUSION: Deficient core stability, enabling excessive pelvis and trunk motion during swing, probably increases the primary injury risk. Although sprinting encompasses a relative risk of hamstring muscle failure in every athlete, running coordination demonstrated to be essential in hamstring injury prevention.

Prone Hip Extension Muscle Recruitment is Associated with Hamstring Injury Risk in Amateur Soccer.

'Core stability' is considered essential in rehabilitation and prevention. Particularly with respect to hamstring injury prevention, assessment and training of lumbo-pelvic control is thought to be key. However, supporting scientific evidence is lacking. To explore the importance of proximal neuromuscular function with regard to hamstring injury susceptibility, this study investigated the association between the Prone Hip Extension (PHE) muscle activation pattern and hamstring injury incidence in amateur soccer players. 60 healthy male soccer players underwent a comprehensive clinical examination, comprising a range of motion assessments and the investigation of the posterior chain muscle activation pattern during PHE. Subsequently, hamstring injury incidence was recorded prospectively throughout a 1.5-season monitoring period. Players who were injured presented a PHE activation pattern that differed significantly from those who did not. Contrary to the controls, hamstring activity onset was significantly delayed (p=0.018), resulting in a shifted activation sequence. Players were 8 times more likely to get injured if the hamstring muscles were activated after the lumbar erector spinae instead of vice versa (p=0.009). Assessment of muscle recruitment during PHE demonstrated to be useful in injury prediction, suggesting that neuromuscular coordination in the posterior chain influences hamstring injury vulnerability.

Proximal Neuromuscular Control Protects Against Hamstring Injuries in Male Soccer Players: A Prospective Study With Electromyography Time-Series Analysis During Maximal Sprinting.

BACKGROUND: With their unremittingly high incidence rate and detrimental functional repercussions, hamstring injuries remain a substantial problem in male soccer. Proximal neuromuscular control ("core stability") is considered to be of key importance in primary and secondary hamstring injury prevention, although scientific evidence and insights on the exact nature of the core-hamstring association are nonexistent at present. HYPOTHESIS: The muscle activation pattern throughout the running cycle would not differ between participants based on injury occurrence during follow-up. STUDY DESIGN: Case-control study; Level of evidence, 3. METHODS: Sixty amateur soccer players participated in a multimuscle surface electromyography (sEMG) assessment during maximal acceleration to full-speed sprinting. Subsequently, hamstring injury occurrence was registered during a 1.5-season follow-up period. Hamstring, gluteal, and trunk muscle activity time series during the airborne and stance phases of acceleration were evaluated and statistically explored for a possible causal association with injury occurrence and absence from sport during follow-up. RESULTS: Players who did not experience a hamstring injury during follow-up had significantly higher amounts of gluteal muscle activity during the front swing phase ( P = .027) and higher amounts of trunk muscle activity during the backswing phase of sprinting ( P = .042). In particular, the risk of sustaining a hamstring injury during follow-up lowered by 20% and 6%, with a 10% increment in normalized muscle activity of the gluteus maximus during the front swing and the trunk muscles during the backswing, respectively ( P < .024). CONCLUSION: Muscle activity of the core unit during explosive running appeared to be associated with hamstring injury occurrence in male soccer players. Higher amounts of gluteal and trunk muscle activity during the airborne phases of sprinting were associated with a lower risk of hamstring injuries during follow-up. Hence, the present results provide a basis for improved, evidence-based rehabilitation and prevention, particularly focusing on increasing neuromuscular control of the gluteal and trunk muscles during sport-specific activities (eg, sprint drills, agility drills).

Susceptibility to Hamstring Injuries in Soccer: A Prospective Study Using Muscle Functional Magnetic Resonance Imaging.

BACKGROUND: Running-related hamstring strain injuries remain a delicate issue in several sports such as soccer. Their unremittingly high incidence and recurrence rates indicate that the underlying risk has not yet been fully identified. Among other factors, the importance of neuromuscular coordination and the quality of interplay between the different hamstring muscle bellies is thought to be a key determinant within the intrinsic injury risk. Muscle functional magnetic resonance imaging (mfMRI) is one of the tools that has been proven to be valid for evaluating intermuscular coordination. PURPOSE: To investigate the risk of sustaining an index or recurring soccer-related hamstring injury by exploring metabolic muscle characteristics using mfMRI. STUDY DESIGN: Cohort study; Level of evidence, 2. METHODS: A total of 27 healthy male soccer players and 27 soccer players with a history of hamstring injuries underwent standardized mfMRI. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise, and a postexercise scan. The exercise-related T2 change, or the signal intensity shift between both scans, was used to detect differences in metabolic characteristics between (1) the different hamstring muscle bellies and (2) the prospective cohorts based on the (re)occurrence of hamstring injuries during a follow-up period of 18 months. RESULTS: The risk of sustaining a first hamstring injury was associated with alterations in the intermuscular hierarchy in terms of the magnitude of the metabolic response after a heavy eccentric effort, with the dominant role of the semitendinosus set aside for a higher contribution of the biceps femoris (P = .017). Receiver operating characteristic (ROC) curve analysis demonstrated that this variable was significantly able to predict the occurrence of index injuries with a sensitivity of 100% and a specificity of 70% when the metabolic activity of the biceps femoris exceeded 10%. The risk of sustaining a reinjury was associated with a substantial deficit in hamstring strength endurance (P = .031). Soccer players who sustained a reinjury were only able to perform prone leg curls for a mean duration of 146.50 ± 76.16 seconds, whereas those with an injury history but no recurrence during follow-up were able to continue for a mean of 237.45 ± 110.76 seconds (95% CI, 11.9-230.5 seconds; P = .031). CONCLUSION: This was the first study to assess the causal relation between the intramuscular recruitment pattern and the risk of sustaining an index or secondary hamstring strain. Changes in intermuscular interplay seem to significantly increase the risk of sustaining index hamstring injuries in male amateur soccer players. Inadequate eccentric muscle endurance could be associated with an increased risk of sustaining a recurring hamstring injury.

Biceps femoris and semitendinosus--teammates or competitors? New insights into hamstring injury mechanisms in male football players: a muscle functional MRI study.

BACKGROUND: The hamstring injury mechanism was assessed by investigating the exercise-related metabolic activity characteristics of the hamstring muscles using a muscle functional MRI (mfMRI) protocol. METHODS: 27 healthy male football players and 27 football players with a history of hamstring injuries (recovered and playing fully) underwent standardised mfMR Imaging. The mfMRI protocol consisted of a resting scan, a strenuous bilateral eccentric hamstring exercise and a postexercise scan. The exercise-related T2 increase or the signal intensity shift between both scans was used to detect differences in metabolic activation characteristics (1) between the different hamstring muscle bellies and (2) between the injury group and the control group. RESULTS: A more symmetrical muscle recruitment pattern corresponding to a less economic hamstring muscle activation was demonstrated in the formerly injured group (p<0.05). The injured group also demonstrated a significantly lower strength endurance capacity during the eccentric hamstring exercise. CONCLUSIONS: These findings suggest that the vulnerability of the hamstring muscles to football-related injury is related to the complexity and close coherence in the synergistic muscle recruitment of the biceps femoris and the semitendinosus. Discrete differences in neuromuscular coordination and activity distribution, with the biceps femoris partly having to compensate for the lack of endurance capacity of the semitendinosus, probably increase the hamstring injury risk.

Proliferation of epithelial rests of Malassez following auto-transplantation of third molars: a case report.

INTRODUCTION: Auto-transplantation of third molars is frequently undertaken in order to restore a perfect occlusion and to improve mastication following a substantial loss of molars. However, little is known about the precise role of the periodontal membrane during this procedure. Therefore, we investigated if the epithelial rests of Malassez persist in the periodontal ligament of auto-transplanted teeth and, if so, whether these may show signs of a neuro-epithelial relationship. CASE PRESENTATION: We report a case of a 21-year-old Caucasian woman who underwent an auto-transplantation of two third molars. After two years, renewed progressive caries of the auto-transplanted teeth led to the removal of the auto-transplanted elements. The periodontal ligament was removed and studied with a light and transmission electron microscope. CONCLUSION: In this report we examined the ultrastructure of the periodontal ligament after auto-transplantation in order to see if the periodontal ligament recovers completely from this intervention. We observed fully developed blood vessels and a re-innervation of the epithelial rests of Malassez which were proliferating following auto-transplantation. This proliferation might be critical in the remodelling of the alveolar socket in order to provide a perfect fit for the transplanted tooth. In order to minimalise the damage to the epithelial rests of Malassez, the extraction of the tooth should be as atraumatic as possible in order to provide an optimal conservation of the periodontal ligament which will be beneficial to the healing-process.