Factors Associated with Recurrent Hamstring Injuries

REDUCTION IN KNEE PAIN SYMPTOMS IN ATHLETES USING AN ACUPUNCTURE PROTOCOL

Pain in the lower limbs is common in athletes and a limiting factor in performance. Acupuncture has shown positive effects as an analgesic treatment and may potentially be used for pain reduction in runners. This study aimed to analyze the parameters associated with knee pain by correlating strength parameters of the musculature assessed in runners treated with acupuncture. A descriptive longitudinal study was conducted on 34 runners of both sexes aged 20 to 52 years, who presented with knee-related pain from January to June, 2015. Two pain questionnaires and a maximal strength test with electromyographic evaluation of the rectus femoris, vastus lateralis, and medialis muscles were used, and patients were monitored during five follow-up visits after an acupuncture protocol. All participants reported experiencing a decrease in knee pain after treatment. The affected limbs showed an increase in average strength by 34% and 25% compared to the contralateral limb. An increase in the number of motor units recruited for the three muscles was observed in both limbs. In conclusion, the proposed acupuncture protocol was effective in reducing pain symptoms in the knee region of athletes, thus influencing their gain in strength and muscle balance. Level of Evidence IV, Case series.

Concordance between sentinel and subsequent injuries: A prospective study of injured New Zealanders

OBJECTIVES

To describe: 1) settings, activities and types of injuries for an 'initial' (sentinel) injury and subsequent injuries over 24 months, and 2) concordance between sentinel and subsequent injury events.

METHODS

Participants (n = 2856) were recruited to the Prospective Outcomes of Injury Study (POIS) following their sentinel injury event, an injury event resulting in an Accident Compensation Corporation (ACC) entitlement claim. Subsequent injuries were those from additional ACC claims in the following 24 months. Injury settings, activities and types were from electronic ACC claims data. The risks of having a subsequent injury of the same type as the sentinel injury were estimated.

RESULTS

Overall, 1653 (58%) participants had 3444 subsequent injury events in 24 months, resulting in 4470 injury diagnoses. Twenty one percent had at least one subsequent injury event of the same type as their sentinel injury; 33% with a spine sprain/strain had at least one subsequent spine sprain/strain. Many participants had at least one subsequent injury event at same setting (26%) as their sentinel injury; of note, 36% of participants whose sentinel injury occurred at home had at least one subsequent injury at home. Seventeen percent of participants had at least one subsequent injury involving the same activity as their sentinel injury; 28% of those whose sentinel injury was a result of contact in sport had at least one subsequent injury also involving sport.

CONCLUSIONS

Subsequent injuries among people presenting to healthcare providers are common. Greater emphasis should be placed on maximising such healthcare provider contact as an injury prevention opportunity.

Comparison of Thigh Muscle Strain Occurrence and Injury Patterns Between Male and Female High School Soccer Athletes

Context: Thigh muscle strains are among the most common injuries in high school soccer for both males and females. Similar results have been reported among college soccer players, specifically for hamstring strains. In college soccer, males have a higher injury rate than women, although they share common injury characteristics. Currently, no studies exist comparing the injury rate or injury characteristics of thigh muscle strains between sexes playing high school soccer. Objective: To compare thigh muscle strain injury rates and injury event characteristics among sexes participating in high school soccer. Design: Descriptive epidemiology study. Setting: A total of 100 nationally representative high schools that participated in the High School Sports-Related Injury Surveillance System, Reporting Information Online. Participants: High school soccer athletes who had a thigh muscle strain. Main Outcome Measures: Injury rates of thigh muscle strains were calculated between sexes. The occurrence of the following variables during a thigh muscle injury was compared between sexes: grade level, age, level of play, event type, time of practice, time of competition, basic injury mechanism, soccer activity, player position, field location, practice type, and time of season. Results: Males had a lower injury rate of thigh muscle strains during competition than females (rate ratio = 0.66; 95% confidence interval, 0.47–0.93). No differences between sexes existed in the distribution of first-time or recurrent event characteristics. When combining sexes, recurrent strains (93%) occurred more frequently on the offensive side of the field than first-time strains (59%), P < .001. The majority of strains occurred among the varsity players (71%), during running activities (60%) and practices (58%). Conclusions: Males were less likely to sustain a thigh muscle strain during competitions, but no other differences existed between sexes. The events surrounding all thigh muscle strains may be described with some common properties. Consideration of these characteristics may assist in the development of preventive and rehabilitative programs as well as direct future research on thigh muscle strains among high school soccer players.

Effectiveness of PRP Injection in Reducing Recovery Time of Acute Hamstring Injury: A Critically Appraised Topic

Clinical Scenario: Hamstring strains are common athletic injuries, with a high-recurrence rate (34%). Recently, platelet-rich plasma (PRP) injections have gained popularity as a potential treatment option to accelerate healing of hamstring injury. Focused Clinical Question: Does the combination of PRP injection and rehabilitation decrease recovery time of acute hamstring injury as compared to rehabilitation alone in college athletes? Summary of Key Findings: A literature search resulted in 3 randomized controlled trials. One study showed benefits in various outcome measures with PRP, compared to rehabilitation alone, while 2 showed no benefits. One study reported improved pain, ultrasonography regenerative indications, and recovery time with PRP injection following acute hamstring injury; however, larger studies have shown no benefits. The literature demonstrates conflicting evidence regarding benefits of PRP injections in hamstring injuries. Clinical Bottom Line: At this time, PRP injections cannot be recommended as having value for hamstring injuries, compared to rehabilitation alone. Strength of Recommendation: Due to inconsistent or limited quality patient-oriented evidence in existing literature, the strength of this recommendation is grade B, based on the strength of recommendation taxonomy.

Profiling the Isokinetic Muscle Strength of Athletes Involved in Sports Characterized by Constantly Varied Functional Movements Performed at High Intensity: A Cross-Sectional Study

BACKGROUND

Constantly varied functional movements performed at high intensity (FMHI) is a type of strength and general conditioning program that has gained widespread popularity in recent years. The very intense exercises performed with lower and upper limbs may create muscular asymmetry or imbalance between agonist and antagonist muscles, and therefore the characterization of isokinetic muscle strength, side-to-side difference, and balance ratios for lower and upper limbs may contribute to a better understanding of the modality characteristics.

OBJECTIVE

To evaluate the knee and shoulder strength of FMHI athletes of both sexes.

DESIGN

Cross-sectional study.

SETTING

Exercise physiology laboratory.

PARTICIPANTS

Sixty FMHI athletes (30 M/30 W) with more than 2 years' experience.

METHODS

Athletes performed isokinetic tests in both lower and upper limbs: concentrically at 60°/s and 240°/s and eccentrically at 240°/s.

MAIN OUTCOME MEASUREMENTS

Isokinetic peak torque of knee flexor and extensor and shoulder internal and external rotator muscles. Conventional and functional strength balance ratios and side-to-side strength difference.

RESULTS

Concentric peak torque values relative to total body mass for shoulder and knee joints were higher in men than women on both sides. Eccentric peak torque values for knee flexor-dominant and extensor-nondominant limbs showed no difference between the sexes. The knee conventional strength balance ratio for dominant and nondominant sides in women (51.5% ± 7.0% and 51.0% ± 7.1%, respectively) and for dominant and nondominant sides in men (54.4% ± 15.2% and 51.5% ± 9.9%, respectively) were no different between the sexes or limbs. The shoulder conventional strength balance ratio was higher in women (78.1 ± 13.2%) than in men (67.6% ± 10.9%) on the nondominant side. Knee and shoulder functional strength balance ratios in nondominant limbs were higher for women than men. Both sexes presented no side-to-side difference for knee joints or muscles, or for shoulder IR muscles, but ER was stronger in dominant limbs.

CONCLUSIONS

These data from highly trained FMHI athletes can be compared to that of other athletes to help determine individual weaknesses, strengths, and imbalances, and may be useful for designing training programs.

LEVEL OF EVIDENCE

III.

Isolated Tearing and Avulsion of the Distal Biceps Femoris Tendon During Sporting Activities: A Systematic Review

Background:

Isolated tearing and avulsions of the distal biceps femoris sustained during sporting activities are uncommon.

Purpose:

To systematically review the literature to identify distal biceps femoris tears and avulsions experienced during sporting activities to determine injury prevalence, sporting activities/mechanisms, management, and time to return to sport.

Study Design:

Systematic review; Level of evidence, 4.

Methods:

A systematic review was conducted investigating studies published between January 1970 and December 2017 that reported on athletes sustaining tears and avulsions of the distal biceps femoris during sporting activity. The review followed the PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines and used the PubMed, Biosis Previews, SPORTDiscus, PEDro, and EMBASE databases. Inclusion criteria were studies reporting on (1) partial or complete tears and avulsions of the distal biceps femoris with documented sporting activity causing injury, (2) injury management (operative vs nonoperative), and (3) patient outcome. Exclusion criteria consisted of studies reporting on (1) distal biceps femoris injuries without tearing, (2) injuries secondary to nonsporting activities (mechanical falls, trauma), (3) concomitant injuries to adjacent structures about the knee, and (4) studies not reporting injury management or patient outcomes. Sporting activities, injury characteristics, management, and time to return to sport were analyzed.

Results:

A total of 22 athletes with isolated distal biceps femoris tears or avulsions were identified. Injuries were predominantly associated with noncontact knee hyperextension with concurrent hip flexion during soccer or track and field, most commonly isolated to the musculotendinous junction. Injuries were treated surgically in 91% (20/22) of athletes. Mean (±SD) overall time to return to sport was 4.9 ± 3.3 months, and for athletes who underwent operative repair, there were no significant postoperative differences based on injury location (musculotendinous junction vs avulsion, P = .25) or injury severity (partial vs complete injury, P = .13).

Conclusion:

Isolated distal biceps femoris injuries occurred primarily via noncontact mechanisms. The majority of cases were treated surgically, with successful return to sport at preinjury levels. No significant difference in return to sport was appreciated based on injury location or severity. Further studies are necessary to determine the impact of treatment method.

Effect of Injury Prevention Programs that Include the Nordic Hamstring Exercise on Hamstring Injury Rates in Soccer Players: A Systematic Review and Meta-Analysis

BACKGROUND

Hamstring injuries are among the most common non-contact injuries in sports. The Nordic hamstring (NH) exercise has been shown to decrease risk by increasing eccentric hamstring strength.

OBJECTIVE

The purpose of this systematic review and meta-analysis was to investigate the effectiveness of the injury prevention programs that included the NH exercise on reducing hamstring injury rates while factoring in athlete workload.

METHODS

Two researchers independently searched for eligible studies using the following databases: the Cochrane Central Register of Controlled Trials via OvidSP, AMED (Allied and Complementary Medicine) via OvidSP, EMBASE, PubMed, MEDLINE, SPORTDiscus, Web of Science, CINAHL and AusSportMed, from inception to December 2015. The keyword domains used during the search were Nordic, hamstring, injury prevention programs, sports and variations of these keywords. The initial search resulted in 3242 articles which were filtered to five articles that met the inclusion criteria. The main inclusion criteria were randomized controlled trials or interventional studies on use of an injury prevention program that included the NH exercise while the primary outcome was hamstring injury rate. Extracted data were subjected to meta-analysis using a random effects model.

RESULTS

The pooled results based on total injuries per 1000 h of exposure showed that programs that included the NH exercise had a statistically significant reduction in hamstring injury risk ratio [IRR] of 0.490 (95 % confidence interval [CI] 0.291-0.827, p = 0.008). Teams using injury prevention programs that included the NH exercise reduced hamstring injury rates up to 51 % in the long term compared with the teams that did not use any injury prevention measures.

CONCLUSIONS

This systematic review and meta-analysis demonstrates that injury prevention programs that include NH exercises decrease the risk of hamstring injuries among soccer players. A protocol was registered in the International Prospective Register of Systematic Reviews, PROSPERO (CRD42015019912).

Hip and trunk muscles activity during nordic hamstring exercise

The nordic hamstring exercise (NHE) is a dynamic lengthening hamstring exercise that requires trunk and hip muscles activation. Thigh muscles activation, specifically hamstring/quadriceps contractions has been previously examined during NHE. Trunk and hip muscles activity have not been enough studied. The aim of this study was to analyze of hip and trunk muscles activity during NHE. Surface electromyography (EMG) and kinematic data were collected during NHE. Ten healthy men with the age range of 21–36 years performed two sets of two repetitions with downward and upward motions each of NHE. EMG activity of fifteen trunk and hip muscles and knee kinematic data were collected. Muscle activity levels were calculated through repeated measure analysis of variance in downward and upward motions, through Paired t-test between downward and upward motions and gluteus maximus to erector spine activity ratio (Gmax/ES ratio) using Pearson correlation analyses were evaluated. Semitendinosus and biceps femoris muscles activity levels were the greatest in both motions and back extensors and internal oblique muscles activity were greater than other muscles (P<0.05). The decreased Gmax/ES ratio was significantly related to peak knee extension angle in downward (r=0.687) and upward motions (r=0.753) (P<0.05). These findings indicate the importance of synergistic muscles and trunk muscles coactivation in eccentric and concentric hamstrings contractions. It could be important for early assessment of subjects with hamstring injury risk.

[Muscle injuries in professional football : Treatment and rehabilitation]

BACKGROUND

Muscle injuries are common in professional sports, especially in football. Recent epidemiological studies showed that muscle injuries account for more than 30% of professional football injuries (1.8-2.2/1000 h exposure); however, even though there are significant differences within a European comparison, a single professional football team diagnosed on average 12 muscle injuries per season, corresponding to more than 300 availability days lost.

OBJECTIVE

The aim of this work is to present the diagnosis, general treatment and comprehensive management of muscle injuries in professional football.

MATERIAL AND METHODS

The present work is based on current scientific findings, experiences of the authors and examples from routine practice in the management of muscle injuries in a professional sports environment.

RESULTS AND CONCLUSION

The authors present a model of gradual progression for the treatment of muscular injuries and their rehabilitation. Due to the time-pressured nature of the professional sports environment, often promoted by coaches and media, this model could help lead players to recover as quickly as possible and return to competitive sports without relapse or sequel injury. This model integrates the player into the treatment plan. The progression sequences in the rehabilitation should be made clear to players and other parties involved, which are crucial for optimal healing. Even if absolute certainty cannot be achieved, i.e. the occurrence of re-injury or secondary injury, this model attempts to minimize the level of risk involved for the returning athlete. Since it is hardly possible to act strictly in line with more conservative guidelines due to the particular circumstances of the professional sport environment, the experiences of the authors are presented in the sense of best practice in order to support future decision-making processes.

A previous hamstring injury affects kicking mechanics in soccer players

BACKGROUND

Although the kicking skill is influenced by limb dominance and sex, how a previous hamstring injury affects kicking has not been studied in detail. Thus, the objective of this study was to evaluate the effect of sex and limb dominance on kicking in limbs with and without a previous hamstring injury.

METHODS

Forty-five professional players (males: N.=19, previously injured players=4, age=21.16±2.00 years; females: N.=19, previously injured players =10, age= 22.15±4.50 years) performed 5 kicks each with their preferred and non-preferred limb at a target 7m away, which were recorded with a three-dimensional motion capture system. Kinematic and kinetic variables were extracted for the backswing, leg cocking, leg acceleration and follow through phases.

RESULTS

A shorter backswing (20.20±3.49% vs. 25.64±4.57%), and differences in knee flexion angle (58±10º vs. 72±14º) and hip flexion velocity (8±0 rad/s vs. 10±2 rad/s) were observed in previously injured, non-preferred limb kicks for females. A lower peak hip linear velocity (3.50±0.84 m/s vs. 4.10±0.45 m/s) was observed in previously injured, preferred limb kicks of females. These differences occurred in the backswing and leg-cocking phases where the hamstring muscles were the most active. A variation in the functioning of the hamstring muscles and that of the gluteus maximus and iliopsoas in the case of a previous injury could account for the differences observed in the kicking pattern.

CONCLUSIONS

Therefore, the effects of a previous hamstring injury must be considered while designing rehabilitation programs to re-educate kicking movement.

Does the FIFA 11+ Injury Prevention Program Reduce the Incidence of ACL Injury in Male Soccer Players?

BACKGROUND

The FIFA 11+ injury prevention program has been shown to decrease the risk of soccer injuries in men and women. The program has also been shown to decrease time loss resulting from injury. However, previous studies have not specifically investigated how the program might impact the rate of anterior cruciate ligament (ACL) injury in male soccer players.

QUESTIONS/PURPOSES

The purpose of this study was to examine if the FIFA 11+ injury prevention program can (1) reduce the overall number of ACL injuries in men who play competitive college soccer and whether any potential reduction in rate of ACL injuries differed based on (2) game versus practice setting; (3) player position; (4) level of play (Division I or II); or (5) field type.

METHODS

This study was a prospective cluster randomized controlled trial, which was conducted in 61 Division I and Division II National Collegiate Athletic Association men's soccer teams over the course of one competitive soccer season. The FIFA 11+ is a 15- to 20-minute on-the-field dynamic warm-up program used before training and games and was utilized as the intervention throughout the entire competitive season. Sixty-five teams were randomized: 34 to the control group (850 players) and 31 to the intervention group (675 players). Four intervention teams did not complete the study and did not submit their data, noting insufficient time to complete the program, reducing the number for per-protocol analysis to 61. Compliance to the FIFA 11+ program, athletic exposures, specific injuries, ACL injuries, and time loss resulting from injury were collected and recorded using a secure Internet-based system. At the end of the season, the data in the injury surveillance system were crosshatched with each individual institution's internal database. At that time, the certified athletic trainer signed off on the injury collection data to confirm their accuracy and completeness.

RESULTS

A lower proportion of athletes in the intervention group experienced knee injuries (25% [34 of 136]) compared with the control group (75% [102 of 136]; relative risk [RR], 0.42; 95% confidence interval [CI], 0.29-0.61; p < 0.001). When the data were stratified for ACL injury, fewer ACL injuries were reported in the intervention group (16% [three of 19]) compared with the control group (84% [16 of 19]), accounting for a 4.25-fold reduction in the likelihood of incurring ACL injury (RR, 0.236; 95% CI, 0.193-0.93; number needed to treat = 70; p < 0.001). With the numbers available, there was no difference between the ACL injury rate within the FIFA 11+ group and the control group with respect to game and practice sessions (games-intervention: 1.055% [three of 15] versus control: 1.80% [12 of 15]; RR, 0.31; 95% CI, 0.09-1.11; p = 0.073 and practices-intervention: 0% [zero of four] versus control: 0.60% [four of four]; RR, 0.14; 95% CI, 0.01-2.59; p = 0.186). With the data that were available, there were no differences in incidence rate (IR) or injury by player position for forwards (IR control = 0.339 versus IR intervention = 0), midfielders (IR control = 0.54 versus IR intervention = 0.227), defenders (IR control = 0.339 versus IR intervention = 0.085), and goalkeepers (IR control = 0.0 versus IR intervention = 0.0) (p = 0.327). There were no differences in the number of ACL injuries for the Division I intervention group (0.70% [two of nine]) compared with the control group (1.05% [seven of nine]; RR, 0.30; CI, 0.06-1.45; p = 0.136). However, there were fewer ACL injuries incurred in the Division II intervention group (0.35% [one of 10]) compared with the control group (1.35% [nine of 10]; RR, 0.12; CI, 0.02-0.93; p = 0.042). There was no difference between the number of ACL injuries in the control group versus in the intervention group that occurred on grass versus turf (Wald chi square [1] = 0.473, b = 0.147, SE = 0.21, p = 0.492). However, there were more ACL injuries that occurred on artificial turf identified in the control group (1.35% [nine of 10]) versus the intervention group (0.35% [one of 10]; RR, 0.14; 95% CI, 0.02-1.10; p = 0.049).

CONCLUSIONS

This program, if implemented correctly, has the potential to decrease the rate of ACL injury in competitive soccer players. In addition, this may also enhance the development and dissemination of injury prevention protocols and may mitigate risk to athletes who utilize the program consistently. Further studies are necessary to analyze the cost-effectiveness of the program implementation and to analyze the efficacy of the FIFA 11+ in the female collegiate soccer cohort.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Relationships among hamstring muscle optimal length and hamstring flexibility and strength

BACKGROUND

Hamstring muscle strain injury (hamstring injury) due to excessive muscle strain is one of the most common injuries in sports. The relationships among hamstring muscle optimal lengths and hamstring flexibility and strength were unknown, which limited our understanding of risk factors for hamstring injury. This study was aimed at examining the relationships among hamstring muscle optimal length and flexibility and strength.

METHODS

Hamstring flexibility and isokinetic strength data and three-dimensional kinematic data for hamstring isokinetic tests were collected for 11 male and 10 female recreational athletes. The maximal hamstring muscle forces, optimal lengths, and muscle lengths in standing were determined for each participant.

RESULTS

Hamstring muscle optimal lengths were significantly correlated to hamstring flexibility score and gender, but not to hamstring strength. The greater the flexibility score, the longer the hamstring muscle optimal length. With the same flexibility score, females tend to have shorter hamstring optimal muscle lengths compared to males. Hamstring flexibility score and hamstring strength were not correlated. Hamstring muscle optimal lengths were longer than but not significantly correlated to corresponding hamstring muscle lengths in standing.

CONCLUSION

Hamstring flexibility may affect hamstring muscle maximum strain in movements. With similar hamstring flexibility, hamstring muscle maximal strain in a given movement may be different between genders. Hamstring muscle lengths in standing should not be used as an approximation of their optimal lengths in calculation of hamstring muscle strain in musculoskeletal system modeling.

Balance Training Programs in Athletes - a Systematic Review

It has become almost routine practice to incorporate balance exercises into training programs for athletes from different sports. However, the type of training that is most efficient remains unclear, as well as the frequency, intensity and duration of the exercise that would be most beneficial have not yet been determined. The following review is based on papers that were found through computerized searches of PubMed and SportDiscus from 2000 to 2016. Articles related to balance training, testing, and injury prevention in young healthy athletes were considered. Based on a Boolean search strategy the independent researchers performed a literature review. A total of 2395 articles were evaluated, yet only 50 studies met the inclusion criteria. In most of the reviewed articles, balance training has proven to be an effective tool for the improvement of postural control. It is difficult to establish one model of training that would be appropriate for each sport discipline, including its characteristics and demands. The main aim of this review was to identify a training protocol based on most commonly used interventions that led to improvements in balance. Our choice was specifically established on the assessment of the effects of balance training on postural control and injury prevention as well as balance training methods. The analyses including papers in which training protocols demonstrated positive effects on balance performance suggest that an efficient training protocol should last for 8 weeks, with a frequency of two training sessions per week, and a single training session of 45 min. This standard was established based on 36 reviewed studies.

The preventive effect of the bounding exercise programme on hamstring injuries in amateur soccer players: the design of a randomized controlled trial

Background

Hamstring injuries are the most common muscle injury in amateur and professional soccer. Most hamstring injuries occur in the late swing phase, when the hamstring undergoes a stretch-shortening cycle and the hamstring does a significant amount of eccentric work. The incidence of these injuries has not decreased despite there being effective injury prevention programmes focusing on improving eccentric hamstring strength. As this might be because of poor compliance, a more functional injury prevention exercise programme that focuses on the stretch-shortening cycle might facilitate compliance. In this study, a bounding exercise programme consisting of functional plyometric exercises is being evaluated.

Methods

A cluster-randomized controlled trial (RCT). Male amateur soccer teams (players aged 18–45 years) have been randomly allocated to intervention and control groups. Both groups are continuing regular soccer training and the intervention group is additionally performing a 12-week bounding exercise programme (BEP), consisting of a gradual build up and maintenance programme for the entire soccer season. The primary outcome is hamstring injury incidence. Secondary outcome is compliance with the BEP during the soccer season and 3 months thereafter.

Discussion

Despite effective hamstring injury prevention programmes, the incidence of these injuries remains high in soccer. As poor compliance with these programmes may be an issue, a new plyometric exercise programme may encourage long-term compliance and is expected to enhance sprinting and jumping performance besides preventing hamstring injuries.

Trial registration

NTR6129. Retrospectively registered on 1 November 2016.

Aging of the skeletal muscle extracellular matrix drives a stem cell fibrogenic conversion

Age‐related declines in skeletal muscle regeneration have been attributed to muscle stem cell (MuSC) dysfunction. Aged MuSCs display a fibrogenic conversion, leading to fibrosis and impaired recovery after injury. Although studies have demonstrated the influence of in vitro substrate characteristics on stem cell fate, whether and how aging of the extracellular matrix (ECM) affects stem cell behavior has not been investigated. Here, we investigated the direct effect of the aged muscle ECM on MuSC lineage specification. Quantification of ECM topology and muscle mechanical properties reveals decreased collagen tortuosity and muscle stiffening with increasing age. Age‐related ECM alterations directly disrupt MuSC responses, and MuSCs seeded ex vivo onto decellularized ECM constructs derived from aged muscle display increased expression of fibrogenic markers and decreased myogenicity, compared to MuSCs seeded onto young ECM. This fibrogenic conversion is recapitulated in vitro when MuSCs are seeded directly onto matrices elaborated by aged fibroblasts. When compared to young fibroblasts, fibroblasts isolated from aged muscle display increased nuclear levels of the mechanosensors, Yes‐associated protein (YAP)/transcriptional coactivator with PDZ‐binding motif (TAZ), consistent with exposure to a stiff microenvironment in vivo. Accordingly, preconditioning of young fibroblasts by seeding them onto a substrate engineered to mimic the stiffness of aged muscle increases YAP/TAZ nuclear translocation and promotes secretion of a matrix that favors MuSC fibrogenesis. The findings here suggest that an age‐related increase in muscle stiffness drives YAP/TAZ‐mediated pathogenic expression of matricellular proteins by fibroblasts, ultimately disrupting MuSC fate.

Return to play after hamstring injuries in football (soccer): a worldwide Delphi procedure regarding definition, medical criteria and decision-making

There are three major questions about return to play (RTP) after hamstring injuries: How should RTP be defined? Which medical criteria should support the RTP decision? And who should make the RTP decision? The study aimed to provide a clear RTP definition and medical criteria for RTP and to clarify RTP consultation and responsibilities after hamstring injury. The study used the Delphi procedure. The results of a systematic review were used as a starting point for the Delphi procedure. Fifty-eight experts in the field of hamstring injury management selected by 28 FIFA Medical Centres of Excellence worldwide participated. Each Delphi round consisted of a questionnaire, an analysis and an anonymised feedback report. After four Delphi rounds, with more than 83% response for each round, consensus was achieved that RTP should be defined as ‘the moment a player has received criteria-based medical clearance and is mentally ready for full availability for match selection and/or full training’. The experts reached consensus on the following criteria to support the RTP decision: medical staff clearance, absence of pain on palpation, absence of pain during strength and flexibility testing, absence of pain during/after functional testing, similar hamstring flexibility, performance on field testing, and psychological readiness. It was also agreed that RTP decisions should be based on shared decision-making, primarily via consultation with the athlete, sports physician, physiotherapist, fitness trainer and team coach. The consensus regarding aspects of RTP should provide clarity and facilitate the assessment of when RTP is appropriate after hamstring injury, so as to avoid or reduce the risk of injury recurrence because of a premature RTP.

Prevention of Hamstring Injuries in Collegiate Sprinters

BACKGROUND

No studies have been reported on how strength, agility, and flexibility training reduce the occurrence of hamstring injuries in sprinters. Therefore, a program for preventing hamstring injury in these athletes has not been established.

PURPOSE

To document the incidence of hamstring injuries during times when different prevention strategies were employed to see whether a particular prevention program reduced their occurrence.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

The study subjects were a total of 613 collegiate male sprinters trained by the same coach over 24 seasons. Tow training was used throughout the research period as a normal sprint training method. The hamstring injury prevention program evolved over time. From 1988 to 1991 (period 1), prevention focused on strength training alone; from 1992 to 1999 (period 2), a combination of strength and agility training was used; and from 2000 to 2011 (period 3), the program incorporated strength, agility, and flexibility training. The incidence of hamstring injuries was compared for each of the 3 prevention strategies.

RESULTS

The incidence of hamstring injuries per athlete-seasons was 137.9 for period 1, 60.6 for period 2, and 6.7 for period 3. A significant difference was observed in the incidence of hamstring injury according to the different prevention programs (χ²(2) = 31.78, P < .001, effect size: Cramer V = 0.23, 1 - β = 0.999). Residual analysis showed that the number of hamstring injuries for period 1 was significantly greater than the expected value (P < .01), whereas that for period 3 was significantly lower than the expected value (P < .01).

CONCLUSION

The incidence of hamstring injuries in sprinters decreased as agility and flexibility were added to strength training.

Running exposure is associated with the risk of hamstring strain injury in elite Australian footballers

Background

To investigate the association between running exposure and the risk of hamstring strain injury (HSI) in elite Australian footballers.

Methods

Elite Australian footballers (n=220) from 5 different teams participated. Global positioning system (GPS) data were provided for every athlete for each training session and match for the entire 2015 season. The occurrences of HSIs throughout the study period were reported. Receiver operator characteristic curve analyses were performed and the relative risk (RR) of subsequent HSI was calculated for absolute and relative running exposure variables related to distance covered above 10 and 24 km/hour in the preceding week/s.

Results

30 prospective HSIs occurred. For the absolute running exposure variables, weekly distance covered above 24 km/hour (>653 m, RR=3.4, 95% CI 1.6 to 7.2, sensitivity=0.52, specificity=0.76, area under the curve (AUC)=0.63) had the largest influence on the risk of HSI in the following week. For the relative running exposure variables, distance covered above 24 km/hour as a percentage of distance covered above 10 km/hour (>2.5%, RR=6.3, 95% CI 1.5 to 26.7, sensitivity=0.93, specificity=0.34, AUC=0.63) had the largest influence on the risk of HSI in the following week. Despite significant increases in the RR of HSI, the predictive capacity of these variables was limited.

Conclusions

An association exists between absolute and relative running exposure variables and elite Australian footballers' risk of subsequent HSI, with the association strongest when examining data within 7–14 days. Despite this, the use of running exposure variables displayed limited clinical utility to predict HSI at the individual level.

No Association Between Return to Play After Injury and Increased Rate of Anterior Cruciate Ligament Injury in Men's Professional Soccer

BACKGROUND

Studies have shown that previous injury, not necessarily anatomically related, is an important injury risk factor. However, it is not known whether a player runs an increased risk of anterior cruciate ligament (ACL) injury after returning to play from other injury types.

PURPOSE

To analyze whether professional soccer players are more susceptible to ACL injury after returning to play from any previous injury.

STUDY DESIGN

Case-control study; Level of evidence, 3.

METHODS

A total of 101 elite male soccer players suffering a first-time complete ACL injury between 2001 and 2014 were included and matched according to team, age, and playing position with control players who did not have a current injury (1:1 match). For each injured player, the 90-day period prior to the ACL injury was analyzed for injuries and compared with that of control players by using odds ratios (ORs) and 95% CIs.

RESULTS

The odds of a player with an ACL injury sustaining a previous injury in the 90-day period did not differ significantly from that of controls (OR, 1.20; 95% CI, 0.66-2.17; P = .65). Testing the frequency of absence periods due to injury between the groups revealed that the odds of a player with an ACL injury having a previous period of absence due to injury did not differ compared with controls (OR, 1.14; 95% CI, 0.64-2.01; P = .77).

CONCLUSION

Players with ACL injury did not have a greater occurrence of absence due to injury in the 3 months preceding their ACL injury compared with matched controls. This indicates that previous injury of any type does not increase the risk of suffering an ACL injury.

Comparative assessment of knee extensor and flexor muscle strength measured using a hand-held vs. isokinetic dynamometer

[Purpose] To compare measurements of knee extensor and flexor muscle strength performed using a hand-held dynamometer and an isokinetic dynamometer in apparently healthy subjects. [Subjects and Methods] Thirty adult volunteers underwent knee muscle strength evaluation using an isokinetic or a hand-held dynamometer. [Results] Strong positive correlations were found between the 2 methods, with correlation coefficients r ranging from 0.72 (95% confidence interval [CI], 0.48-0.86) to 0.87 (95% CI, 0.75-0.94), depending on the muscle group and the isokinetic evaluation mode. The reproducibility of the hand-held dynamometer findings was good, judged by a coefficient of variation of 3.2-4.2%. However, the correlation between the 2 methods for the assessment of flexor/extensor ratios ranged from -0.04 to 0.46. [Conclusion] Knee extensor and flexor muscle strength recorded with a hand-held dynamometer is reproducible and significantly correlated with the isokinetic values, indicating that this method may in some cases be a useful replacement for isokinetic strength measurement. However, for strength ratio assessment, and when judged against the isokinetic standard, a hand-held dynamometer is not a valid option.

Evaluating injury risk in first and second league professional Portuguese soccer: muscular strength and asymmetry

Strength imbalances between the hamstrings and quadriceps are an essential predictor for hamstring strain in soccer. The study aimed to investigate and compare the muscle strength imbalances of professional soccer players of different performance levels. One hundred and fifty nine senior male professional soccer players from first (n = 75) and second league (n = 84) Portuguese clubs participated in this study. Muscle strength was evaluated with a REV9000 isokinetic dynamometer. Maximal peak torque data were used to calculate quadriceps and hamstrings strength during concentric and eccentric actions, bilateral asymmetry, conventional strength ratios and dynamic control ratios. Second league athletes produced slightly lower conventional strength ratios in the right and left legs (ES = 0.22, p = 0.17 and ES = 0.36, p = 0.023, respectively) compared to the first league athletes. No significant differences were found in dynamic control ratios or in bilateral asymmetry among first and second league athletes. These findings do not show a clear link between the competitive level and injury risk in soccer players. However, some of the differences found, particularly in conventional strength ratios, highlight the importance of performing off-season and pre-season strength assessments to prescribe and adjust individual strength training programs among professional soccer players.

Spanish Consensus Statement: The Treatment of Muscle Tears in Sport

On the 21st of March, 2015, experts met at Clínica CEMTRO in Madrid, Spain, under the patronage of The Spanish Society for Sports Traumatology (SETRADE), The Spanish Federation of Sports Medicine (FEMEDE), The Spanish Association of Medical Services for Football Clubs (AEMEF), and The Spanish Association of Medical Services for Basketball Clubs (AEMB) with the aim of establishing a round table that would allow specialists to consider the most appropriate current general actions to be taken when treating muscle tears in sport, based on proven scientific data described in the medical literature. Each expert received a questionnaire prior to the aforementioned meeting comprising a set of questions concerning therapeutic indications generally applied in the different stages present during muscle repair. The present Consensus Document is the result of the answers to the questionnaire and resulting discussion and consensus over which are the best current indications in the treatment of muscle tears in sport. Avoiding immobilization, not taking nonsteroidal anti-inflammatory drugs (NSAIDs) randomly, fostering early mobilization, increasing vascularization of injured, site and regulating inflammatory mechanisms—without inhibiting these from the early stages of the recovery period—all stood out as main points of the Consensus Document. Additionally, there is controversy concerning cell stimulation techniques and the use of growth factors or cell inhibitors. The decision concerning discharge was unanimous, as was the criteria considered when it came to performing sport techniques without pain.

Prediction of hamstring injury in professional soccer players by isokinetic measurements

OBJECTIVES

previous studies investigating the ability of isokinetic strength ratios to predict hamstring injuries in soccer players have reported conflicting results.

HYPOTHESIS

to determine if isokinetic ratios are able to predict hamstring injury occurring during the season in professional soccer players.

STUDY DESIGN

case-control study;

LEVEL OF EVIDENCE

3.

METHODS

from 2001 to 2011, 350 isokinetic tests were performed in 136 professional soccer players at the beginning of the soccer season. Fifty-seven players suffered hamstring injury during the season that followed the isokinetic tests. These players were compared with the 79 uninjured players. The bilateral concentric ratio (hamstring-to-hamstring), ipsilateral concentric ratio (hamstring-to-quadriceps), and mixed ratio (eccentric/concentric hamstring-to-quadriceps) were studied. The predictive ability of each ratio was established based on the likelihood ratio and post-test probability.

RESULTS

the mixed ratio (30 eccentric/240 concentric hamstring-to-quadriceps) <0.8, ipsilateral ratio (180 concentric hamstring-to-quadriceps) <0.47, and bilateral ratio (60 concentric hamstring-to-hamstring) <0.85 were the most predictive of hamstring injury. The ipsilateral ratio <0.47 allowed prediction of the severity of the hamstring injury, and was also influenced by the length of time since administration of the isokinetic tests.

CONCLUSION

isokinetic ratios are useful for predicting the likelihood of hamstring injury in professional soccer players during the competitive season.

Effect of Ankle Positioning During Hamstring Stretches for Improving Straight Leg Hip Flexion Motion

OBJECTIVE

To compare the effects of stretching the hamstrings with the ankle in either a plantar-flexed (PF) or dorsiflexed (DF) position for improving straight leg hip flexion range of motion (ROM) over a 4-week period.

DESIGN

Randomized, single-blinded, pretest, posttest design.

SETTING

Athletic training facility.

PARTICIPANTS

Each limb of 34 asymptomatic individuals (15 males, 19 females) was randomly assigned to one of the 3 groups. Twenty-four limbs received hamstring stretches with the ankle in DF, 24 limbs received hamstring stretches with the ankle in PF, and 20 limbs received no stretch (control).

INDEPENDENT VARIABLES

Ankle position (PF, DF) during hamstring stretching.

MAIN OUTCOME MEASURES

We measured pretest and posttest passive straight leg hip flexion ROM with the test ankle in a neutral position. For the intervention groups, the test limb was passively stretched with the ankle held in end range DF or PF for their respective group. Each stretch was held for 30 seconds for a total of 3 applications. Two treatment sessions were completed per week for a total of 4 weeks. The control limbs received no stretching during the 4-week period. We conducted 1-way analyses of covariance to determine significant changes in ROM between groups (P < 0.05).

RESULTS

There was no significant difference between treatment groups (P = 0.90), but a significant difference was found for both the PF (P = 0.04) and DF (P = 0.01) groups when compared with the control group.

CONCLUSIONS

Our findings indicate that both stretching the hamstrings in either PF or DF improve straight leg hip ROM compared with a control group.

CLINICAL RELEVANCE

The results of this study should be considered by clinicians when determining the optimal stretching techniques aimed at increasing hamstring length.

Hip adduction and abduction strength profiles in elite, sub-elite and amateur Australian footballers

OBJECTIVES

It has been reported that obtaining an adduction-to-abduction strength ratio of 90-100%, and an adduction strength equal to that of the uninjured side, are suitable clinical milestones for return to sport following groin injury. Little is known about hip adduction and abduction strength profiles in Australian footballers. This study aimed to compare isometric hip adduction and abduction strength profiles between preferred and non-preferred kicking legs in elite, sub-elite and amateur Australian footballers.

DESIGN

Cross sectional study

METHODS

36 elite, 19 sub-elite and 18 amateur Australian footballers, with a mean age of 24, 19 and 23 years respectively, were included. Maximal hip isometric adduction and abduction strength were measured using a hand held dynamometer with external belt fixation.

RESULTS

There were no significant differences in isometric hip adduction (p=0.262) or abduction (p=0.934) strength, or the adduction-to-abduction ratio (p=0.163), between preferred and non-preferred kicking legs, regardless of playing level. Elite players had significantly greater isometric hip adduction and abduction strength than both sub-elite (mean difference; adduction=46.01N, p<0.001, abduction=30.79N, p=0.003) and amateur players (mean difference; adduction=78.72N, p<0.001, abduction=59.11N, p<0.001). There was no significant difference in the adduction-to-abduction ratio between the playing levels (p=0.165).

CONCLUSIONS

No significant differences were found between preferred and non-preferred kicking legs across the playing levels for isometric hip adduction, abduction or the adduction-to-abduction ratio. This may have implications for developing groin injury prediction and return to sport criteria in Australian footballers.

Active knee range of motion assessment in elite track and field athletes: normative values

BACKGROUND

flexibility is an important physical characteristic in athletes in terms of performance and injury prevention. Active Range Of Motion (AROM) was assessed in elite Greek track and field athletes.

METHODS

prospective cohort study was carried out. In the period 2000-2010, the AROM was measured bilaterally with the Active Knee Extension (AKE) test during an in-season period with a goniometer in 127 athletes.

RESULTS

male runners and jumpers had a higher mean AROM than throwers, but this result was not statistically significant. Female jumpers had a higher mean AROM than both runners and throwers, but the difference was also not statistically significant.

CONCLUSION

in athletes, mean posterior thigh muscle flexibility is likely to be between 72.3° and 73.9°. Posterior thigh muscle flexibility is associated with performance, the higher the AROM, the better performance is achieved athletes have generally high AROM, and this may be a result of their increased muscle flexibility. The normative values of posterior thigh flexibility may assist in better monitoring rehabilitation of the posterior thigh muscle injuries and be useful in pre-season screening of athletes' flexibility.

Epidemiology of Hamstring Strains in 25 NCAA Sports in the 2009-2010 to 2013-2014 Academic Years

BACKGROUND

The epidemiology of hamstring strains among student-athletes has been extensively researched. However, there is a paucity of recent data describing patterns of hamstring strains.

PURPOSE

To describe the epidemiology of hamstring strains in 25 National Collegiate Athletic Association (NCAA) championship sports.

STUDY DESIGN

Descriptive epidemiology study.

METHODS

Hamstring strains data were analyzed from the NCAA Injury Surveillance Program during the 2009-2010 to 2013-2014 academic years. Hamstring strain injury rates, rate ratios (RRs), and injury proportion ratios were reported with 95% CIs.

RESULTS

During the study period, 1142 hamstring strains were reported, leading to an injury rate of 3.05 per 10,000 athlete-exposures (AEs). Most hamstring strains occurred during practices (68.2%). However, the competition rate (5.24 per 10,000 AEs) was larger than the practice rate (2.56 per 10,000 AEs; RR = 2.05; 95% CI, 1.81-2.32). A slight majority occurred during the regular season (52.9%). However, the preseason rate (5.00 per 10,000 AEs) was larger than the regular season/postseason rate (2.34 per 10,000 AEs; RR = 2.14; 95% CI, 1.90-2.40). Men's football, men's soccer, and women's soccer contributed the greatest proportion of hamstring strains (35.3%, 9.9%, and 8.3%, respectively). Most hamstring strains were due to noncontact (72.3%). Of all hamstring strains, 12.6% were recurrent, 37.7% resulted in a time loss of <24 hours, and 6.3% resulted in a time loss >3 weeks. Variations in hamstring strain patterns existed by sport. The hamstring strain rate was larger in men than in women in soccer (RR = 1.60; 95% CI, 1.22-2.11), baseball/softball (RR = 1.66; 95% CI, 1.07-2.59), and indoor track (RR = 1.88; 95% CI, 1.26-2.78). In addition, proportions of hamstring strains that were recurrent were higher among men in most sex-comparable sports, but this difference was not significant.

CONCLUSION

Hamstring strain rates were higher in the preseason and in competition. Student-athletes should be acclimatized to the rigors of preseason participation. Meanwhile, further surveillance should investigate the effectiveness of prospective prevention programs in an effort to reduce the prevalence of initial and recurrent hamstring strain injuries.

Surgical Management of Recurrent Musculotendinous Hamstring Injury in Professional Athletes

BACKGROUND

Hamstring injury is the most common muscular lesion in athletes. The conservative treatment is well described, and surgical management is often indicated for proximal tendinous avulsions. To our knowledge, no surgical treatment has been proposed for failure of conservative treatment in musculotendinous hamstring lesions.

PURPOSE

To describe the surgical management of proximal and distal hamstring musculotendinous junction lesions in professional athletes after failure of conservative treatment.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A consecutive series of 10 professional athletes, including 4 soccer players, 4 rugby players, and 2 handball players, underwent surgical intervention between October 2010 and June 2014 for the treatment of recurrent musculotendinous hamstring injuries. All athletes had failed at least 3 months of conservative treatment for a recurrent musculotendinous hamstring injury. Surgical resection of the musculotendinous scar tissue was performed using a longitudinal muscular suture. Lower Extremity Functional Scale (LEFS) and Marx scores were obtained at the 3-month follow-up, and a final phone interview was completed to determine recurrence of hamstring injury and return to previous level of play.

RESULTS

The mean age at surgery was 25.2 years (range, 19-35 years). The musculotendinous hamstring lesions involved 8 semitendinosus and 2 biceps femoris, with 6 injuries located proximally and 4 distally. Conservative treatment lasted a mean 5.1 months (range, 3-9 months) after last recurrence, and the patients had an average of 2.7 (range, 2-5) separate incidents of injury recurrence before surgical intervention was decided upon. At the 3-month follow-up, all patients had Marx activity scores of 16 and LEFS scores of 80. All 10 patients returned to the same level of play at a mean 3.4 months (range, 2-5 months). At a mean follow-up of 28.7 months, none of the athletes had suffered a recurrence. No surgical complication was encountered.

CONCLUSION

In cases of failed conservative treatment of musculotendinous hamstring lesions, surgical intervention may be a viable treatment option in professional athletes and allows the patient to return to the same level of play.

A qualitative and quantitative analysis of the attachment sites of the proximal hamstrings

PURPOSE

Proximal hamstring tears represent a challenge. Surgical repair of such tears has been reported utilizing both open and endoscopic techniques. It was hypothesized that the proximal attachments of the hamstring muscle group could be reproducibly and consistently measured from pertinent bony anatomical reference landmarks.

METHODS

Fourteen fresh-frozen, human cadaveric specimens were dissected, and measurements were taken regarding the proximal attachments of the hamstring muscle group in reference to bony landmarks. A highly precise coordinate measuring device was used for three-dimensional measurements of tendon footprints and bony landmarks, and relevant distances between structures were calculated.

RESULTS

The semitendinosus and long head of the biceps femoris shared a proximal origin (conjoined tendon), having an oval footprint with an average area of 567.0 mm(2) [95 % CI 481.0-652.9]. The semimembranosus (SM) footprint was crescent-shaped and located anterolateral to the conjoined tendon, with an average area of 412.4 mm(2) [95 % CI 371.0-453.8]. The SM footprint had an accessory tendinous extension that extended anteromedially forming a distinct footprint. A consistent bony landmark was found at the medial ischial margin, 14.6 mm [95 % CI 12.7-16.5] from the centre of the conjoined tendon footprint, which coincided with the distal insertion of the sacrotuberous ligament.

CONCLUSION

The conjoined tendon was the largest attachment of the proximal hamstring group. Two other distinct attachment footprints were identified as the SM footprint and the accessory tendinous extension. The sacrotuberous ligament insertion served as a bony landmark. The anatomical data established in this study may aid in better restoring the anatomy during repair of proximal hamstring tears.

Programas de exercício na prevenção de lesões em jogadores de futebol: uma revisão sistemática

Dentre as lesões ocorridas em jogadores de futebol, as lesões dos isquiotibiais são as mais frequentes. Programas de exercício que previnam o seu aparecimento e diminuam a sua recorrência e severidade são de extrema importância para os fisioterapeutas, treinadores e jogadores. Conhecer as evidências científicas sobre a eficácia de programas de exercício na prevenção de lesões dos isquiotibiais, em jogadores de futebol masculino. Os estudos foram selecionados para revisão em diferentes bases de dados. Para avaliar a qualidade metodológica dos estudos e a força de evidência dos resultados utilizou-se a escala da Base de dados de Evidência em Fisioterapia (PEDro) e o sistema de classificação Melhor Síntese de Evidência, respectivamente. Os programas de exercício utilizados foram: força concêntrica e excêntrica; força excêntrica Nordic Hamstrings; The FIFA 11+; e elasticidade. As variáveis estudadas foram a incidência de lesões, a incidência de novas lesões, a recorrência de lesões, a severidade das lesões e o risco de lesão. O programa de força concêntrica e excêntrica e o programa de força excêntrica Nordic Hamstrings parecem ser os mais eficazes na redução da incidência das lesões e da incidência de novas lesões dos isquiotibiais, respetivamente (evidências limitadas). O programa de exercício de força excêntrica Nordic Hamstring não é eficaz na diminuição do risco de lesão (evidências limitada) e na melhoria da severidade das lesões (evidência moderada). O programa The FIFA 11+ não é eficaz na redução da incidência das lesões (evidência limitada). Há evidências contraditórias nas variáveis restantes.

Days to Return to Participation After a Hamstrings Strain Among American Collegiate Soccer Players

CONTEXT

Among US collegiate soccer players, the incidence rate and the event characteristics of hamstrings strains differ between sexes, but comparisons in the return-to-participation (RTP) time have not been reported.

OBJECTIVE

To compare the RTP time between male and female collegiate soccer players and analyze the influence of event characteristics on the RTP time for each sex.

DESIGN

Descriptive epidemiology study.

SETTING

Data were collected from collegiate teams that voluntarily participated in the National Collegiate Athletic Association Injury Surveillance System.

PATIENTS OR OTHER PARTICIPANTS

Collegiate soccer athletes who sustained 507 hamstrings strains (306 men, 201 women) during the 2004 through 2009 fall seasons.

MAIN OUTCOME MEASURE(S)

Nonparametric statistics were used to evaluate RTP time differences between sexes and among categories of each event characteristic (ie, time of season, practice or competition, player position). Negative binomial regression was used to model the RTP time for each sex. All analyses were performed separately for first-time and recurrent strains.

RESULTS

We found no differences in the RTP time between sexes for first-time (median: men = 7.0 days, women = 6.0 days; P = .07) or recurrent (median: men = 11 days, women = 5.5 days; P = .06) hamstrings strains. For male players with first-time strains, RTP time was increased when the strain occurred during competition or the in-season/postseason and varied depending on the division of play. Among female players with first-time strains, we found no differences in RTP time within characteristics. For male players with recurrent hamstrings strains, the RTP time was longer when the injury occurred during the in-season/postseason. Among female players with recurrent strains, RTP time was longer for forwards than for midfielders or defenders.

CONCLUSIONS

Although we found no differences in the RTP time after hamstrings strains in male and female collegiate soccer players, each sex had unique event characteristics that influenced RTP time.

Determination of the criterion-related validity of hip joint angle test for estimating hamstring flexibility using a contemporary statistical approach

OBJECTIVE

To examine the criterion-related validity of the horizontal hip joint angle (H-HJA) test and vertical hip joint angle (V-HJA) test for estimating hamstring flexibility measured through the passive straight-leg raise (PSLR) test using contemporary statistical measures.

DESIGN

Validity study.

SETTING

Controlled laboratory environment.

PARTICIPANTS

One hundred thirty-eight professional trampoline gymnasts (61 women and 77 men).

ASSESSMENT OF RISK FACTORS

Hamstring flexibility.

MAIN OUTCOME MEASURES

Each participant performed 2 trials of H-HJA, V-HJA, and PSLR tests in a randomized order. The criterion-related validity of H-HJA and V-HJA tests was measured through the estimation equation, typical error of the estimate (TEEST), validity correlation (β), and their respective confidence limits.

RESULTS

The findings from this study suggest that although H-HJA and V-HJA tests showed moderate to high validity scores for estimating hamstring flexibility (standardized TEEST = 0.63; β = 0.80), the TEEST statistic reported for both tests was not narrow enough for clinical purposes (H-HJA = 10.3 degrees; V-HJA = 9.5 degrees). Subsequently, the predicted likely thresholds for the true values that were generated were too wide (H-HJA = predicted value ± 13.2 degrees; V-HJA = predicted value ± 12.2 degrees).

CONCLUSIONS

The results suggest that although the HJA test showed moderate to high validity scores for estimating hamstring flexibility, the prediction intervals between the HJA and PSLR tests are not strong enough to suggest that clinicians and sport medicine practitioners should use the HJA and PSLR tests interchangeably as gold standard measurement tools to evaluate and detect short hamstring muscle flexibility.

Skeletal muscle as a regulator of the longevity protein, Klotho

Klotho is a powerful longevity protein that has been linked to the prevention of muscle atrophy, osteopenia, and cardiovascular disease. Similar anti-aging effects have also been ascribed to exercise and physical activity. While an association between muscle function and Klotho expression has been previously suggested from longitudinal cohort studies, a direct relationship between circulating Klotho and skeletal muscle has not been investigated. In this paper, we present a review of the literature and preliminary evidence that, together, suggests Klotho expression may be modulated by skeletal muscle activity. Our pilot clinical findings performed in young and aged individuals suggest that circulating Klotho levels are upregulated in response to an acute exercise bout, but that the response may be dependent on fitness level. A similar upregulation of circulating Klotho is also observed in response to an acute exercise in young and old mice, suggesting that this may be a good model for mechanistically probing the role of physical activity on Klotho expression. Finally, we highlight overlapping signaling pathways that are modulated by both Klotho and skeletal muscle and propose potential mechanisms for cross-talk between the two. It is hoped that this review will stimulate further consideration of the relationship between skeletal muscle activity and Klotho expression, potentially leading to important insights into the well-documented systemic anti-aging effects of exercise.

Preventive Effects of Eccentric Training on Acute Hamstring Muscle Injury in Professional Baseball

BACKGROUND

Hamstring injuries are the second most common injury causing missed days in professional baseball field players. Recent studies have shown the preventive benefit of eccentric conditioning on the hamstring muscle group in injury prevention. Specifically, Nordic-type exercises have been shown to decrease the incidence of acute hamstring injuries in professional athletes.

PURPOSE

This was a prospective study performed in coordination with a single Major League Baseball (MLB) organization (major and minor league teams) that targeted the effects of Nordic exercises on the incidence of acute hamstring injuries in the professional-level baseball player.

STUDY DESIGN

Prospective cohort study; Level of evidence, 2.

METHODS

The daily workouts of 283 professional baseball players throughout all levels of a single MLB organization were prospectively recorded. The intervention group participated in the Nordic exercise program and was compared with a randomly selected control group of professional athletes within the organization not participating in the exercise program. The incidence of hamstring injuries in both groups was compared, and the total number of days missed due to injury was compared with the 2 previous seasons.

RESULTS

There were 10 hamstring injuries that occurred during the 2012 season among the 283 professional athletes that required removal from play. There were no injuries that occurred in the intervention group (n = 65, 0.00%; P = .0381). The number needed to treat (NNT) to prevent 1 hamstring injury was 11.3. The average repetitions per week of the injured group were assessed at multiple time points (2, 4, 6, and total weeks) prior to injury. There were significantly fewer repetitions per week performed in the injured group at all time points compared with overall average repetitions per week in the noninjured group (P = .0459, .0127, .0164, and .0299, respectively). After beginning the Nordic exercise program, there were 136 total days missed due to a hamstring injury during the 2012 season. This number was less than the 2011 season (273 days missed) and the 2010 season (309 days missed).

CONCLUSION

Study results indicate the initiation of Nordic hamstring exercises may decrease the incidence of acute hamstring injuries and potentially decrease the total number of days missed due to injury in professional baseball players.

CLINICAL RELEVANCE

The financial and competitive interest in professional baseball players is of large importance to the player, team, and fans. Prevention of injuries is as important to all parties involved as the treatment and rehabilitation following an injury. This prospective study shows the initiation of a simple, free exercise can reduce the incidence of hamstring injury in the professional-level baseball player.