Do athletes with hamstring strain injury have shorter muscle fascicles in the injured limb?

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

How are hamstring strain injuries managed in elite men's football clubs? A survey with 62 Brazilian physical therapists.

OBJECTIVE: To describe perceptions and practices of physical therapists from elite men's football clubs on the management of athletes with hamstring strain injury (HSI). DESIGN: Cross-sectional study. SETTING: Online survey. PARTICIPANTS: Physical therapists from clubs engaged in the two main divisions of Brazilian men's football. MAIN OUTCOME MEASURES: Practices for assessment and rehabilitation of athletes with HSI. RESULTS: This survey had 62 physical therapists from 35 of the 40 eligible clubs (87.5% representativeness). Despite heterogeneity on assessment practices, all respondents use imaging exams, adopt injury classification scales, and evaluate aspects related to pain, range of motion, muscle strength, and functional status of athletes with HSI. Rehabilitation programs are usually divided into 3 to 4 phases. All respondents usually apply electrophysical agents and stretching in HSI rehabilitation programs, 98.4% apply strengthening exercises (93.5% include eccentrics), 96.8% manual therapy, 95.2% exercises that mimic the functional demands of football, and 93.5% lumbopelvic stabilization exercises. Muscle strength was the most reported return to play criterion (71% of respondents). CONCLUSION: The present study allowed the sports physical therapy community to become aware of the approaches usually adopted for management of athletes with HSI who play in the highest level of Brazilian men's football.

Effectiveness of Hematoma Aspiration and Platelet-rich Plasma Muscle Injections for the Treatment of Hamstring Strains in Athletes.

INTRODUCTION: The effect of platelet-rich plasma (PRP) treatment on recovery in acute hamstring injuries is controversial. Previous study results are inconsistent, and a standardized therapeutic approach has not been established yet. PURPOSE: To assess the treatment effect using a combination of hematoma aspiration and muscle strain PRP injection in partial hamstring muscle tears (grade 2 strains) in athletes. METHODS: Magnetic resonance imaging of athletes with grade 2 hamstring strains were reviewed from 2013 to 2018. From 2013 to 2015, athletes were treated conservatively, and from 2016 to 2018, with a combination of ultrasound-guided hematoma aspiration and PRP muscle strain injection. The outcome, including return-to-play (in days) and recurrence rate, was compared retrospectively between both groups (conservative vs aspiration/PRP) using ANOVA and Fisher's exact test. There was no significant difference in age, type of sport, and muscle involvement (including injury grade/location, hamstring muscle type, and length/cross-sectional area of the strain). RESULTS: Fifty-five athletes (28 treated conservatively, 27 with hematoma aspiration/PRP injection) were included. Average return-to-play time (mean) was 32.4 d in the conservative group and 23.5 d in the aspiration/PRP group (P < 0.001). Recurrence rate of the hamstring strain was 28.6% (8/28) in the conservative treatment group and less than 4% (1/27) in the aspiration/PRP group (P = 0.025). CONCLUSIONS: Athletes with grade 2 hamstring strains treated with a combination of hematoma aspiration and PRP injection had a significantly shorter return-to-play and a lower recurrence rate compared with athletes receiving conservative treatment.

Morphological study on the origin of the semitendinosus muscle in the long head of biceps femoris.

Hamstring muscle injuries are the most prevalent among athletes who engage in sprinting activities. Their most frequent location is where the long head of the biceps femoris joins with the semitendinosus muscle to form the conjoint hamstring tendon. Just distal to this area, an additional group of fibers of the semitendinosus originate from medial aspect of biceps femoris. The objective of this study was to analyze the morphological characteristics of this union and to discuss its potential role in hamstring tears. Anatomical dissection was performed on 35 thighs. Samples obtained from this region were sectioned and stained with Masson's trichrome for further histological evaluation. A group of fibers from the semitendinosus muscle originating from the long head of the biceps femoris were observed in all 35 specimens. This origin was located 67 ± 12 mm from the ischial tuberosity and was 32 ± 14 mm in length. This group of muscle fibers had a width of 10.9 ± 5.3 mm and a thickness in the anteroposterior axis of 3.2 ± 1.4 mm. Its pennation angle was 9.2 ± 1.5 degrees. Microscopic examination showed muscle cells from both muscles contacting interposed tendinous tissue. In conclusion, fibers of the semitendinosus muscle consistently arise from the proximal aspect of the long head of biceps femoris. The morphological characteristics of this junction have functional implications. The horizontal component of the semitendinosus vector could pull the long head of the biceps femoris medially during its shortening-lengthening cycle, rendering it an intrinsic risk factor for hamstring injuries.

Eccentric knee flexor strength of professional football players with and without hamstring injury in the prior season.

Both injury history and eccentric knee flexor strength have been associated with risk of football players sustaining hamstring strain injury (HSI). However, it remains unclear whether football players who sustained HSIs in the prior season present persistent eccentric strength deficits. Therefore, the aim of the present study was to verify the eccentric knee flexor strength of professional male football players with and without history of HSI in the prior season. This case-control study assessed 210 professional male football players from 10 Brazilian clubs: 182 included in the control group and 28 in the previously injured group. Players from the injured group had suffered unilateral HSI in the prior season. We measured the knee flexors peak force during the Nordic hamstring exercise and calculated the between-limb asymmetry. Groups were similar for age, body mass and height (p > 0.05). Control group had similar strength values between left and right limbs (376.29 ± 61.77 N vs. 380.28 ± 61.77 N; p = 0.27; d = 0.06), while the previously injured limb was weaker than the contralateral uninjured limb in the injured group (350.87 ± 60.79 N vs. 385.75 ± 63.49 N; p < 0.01; d = 0.56). Thirty-seven percent of players in the control group and 50% in the injured group presented between-limb asymmetry >10%. This study demonstrates that players with history of HSI in the prior season present reduced eccentric knee flexor strength in the injured limb, but half of them have between-limb asymmetry within the most commonly adopted benchmark value of 10%.

Effects of low-level laser therapy on hamstring strain injury rehabilitation: A randomized controlled trial.

OBJECTIVES: To evaluate the effects of low-level laser therapy (LLLT) on functional rehabilitation following hamstring strain injury (HSI) in amateur athletes treated with an exercise-based rehabilitation program. DESIGN: Randomized controlled trial. METHODS: Male athletes (18-40 years old) who sustained HSI were randomized in LLLT or placebo groups. All patients were engaged in the same exercise-based rehabilitation program until they met specific criteria to return to sport. Hamstring muscles were treated with LLLT or placebo immediately after each rehabilitation session. The primary outcome was time-to-return to sport. Secondary outcomes were the number of rehabilitation sessions, hamstring flexibility, hamstring strength, and re-injury rate. RESULTS: Twenty-four athletes began rehabilitation, and 22 (11 per group) completed the study schedule. Participants of LLLT and placebo groups had similar age, body size, injury characteristics, and baseline levels of hamstring flexibility and strength. The two groups increased flexibility and strength similarly throughout the rehabilitation program. Time-to-return to sport was the same for athletes treated with LLLT (23 ± 9 days) and placebo (24 ± 13 days). There were no re-injuries within 6 months after return to sport. CONCLUSION: LLLT, as used in this study, did not optimize functional rehabilitation following HSI in amateur athletes treated with an exercise-based rehabilitation program.

Clinical Features and isokinetic Parameters in Assessing Injury Risk in elite Football Players.

Football players frequently face the occurrence of non-contact injuries. Although there are likely multiple factors that contribute to increased risk of non-contact injury, it remains a challenge to correlate all these factors. However, it is not clear how much of individual training abilities may interfere in these events. As such, the primary aim of the present study was to determine whether the reduction of functional performance of the thigh in the isokinetic knee tests, anthropometric and morbid history can establish risk factors for lower-limb musculoskeletal injuries throughout the season. The incidence of injuries and odds ratios were calculated for suspected risk factors. Hamstring/Quadriceps conventional ratio outside of the safety range (55-64%) may be involved in the occurrence of non-contact muscle injuries and the risk for any musculoskeletal injuries in the lower extremities is 16 times higher when extensor peak of torque exceeds 10% and 12 times higher when flexor peak of torque difference was greater than 10%. This kind of evaluation can result in intervention programs that may decrease the risk of lower-limb musculoskeletal injuries. Based on these results we can establish a specific and individualized exercise program for each athlete and thus protect them during the season.

Hamstring Injuries in Athletes: Evidence-based Treatment.

Hamstring injuries are common in athletes and can cause notable disability. They can be separated based on proximal, muscle belly, and distal injuries, with proximal and distal injuries more commonly requiring surgical intervention. Most injuries do not require acute MRI; however, MRI is useful in proximal and distal injuries as well as muscle belly tears that fail to respond to nonsurgical treatment. Acute repair of proximal avulsions, both partial and complete, result in successful outcomes, whereas chronic complete repairs are more difficult and less reliable. Muscle belly injuries have predictable outcomes but recurrence is common. Nonsurgical treatments focus on eccentric strengthening with the possible addition of low WBC platelet-rich plasma, which may have the potential to hasten recovery and decrease re-rupture. Distal injuries are relatively rare but may require surgical intervention. Hamstring reinjury is common, making continuation of preventive therapies after return to sport essential. Future research with larger sample sizes are required to determine how to decrease injury and reinjury rates, to evaluate the efficacy of platelet-rich plasma and to determine other treatments that may accelerate recovery after injury.

Is radial extracorporeal shock wave therapy combined with a specific rehabilitation program (rESWT + RP) more effective than sham-rESWT + RP for acute hamstring muscle complex injury type 3b in athletes? Study protocol for a prospective, randomized, double-blind, sham-controlled single centre trial.

BACKGROUND: Acute injuries of the hamstring muscle complex (HMC) type 3b (interfascicle/bundle-tear) are frequently observed in various sports disciplines both in elite and recreational sport. The treatment of choice of acute HMC injuries type 3b is a progressive physiotherapeutic exercise programme. Besides this, there is currently only insufficient scientific evidence to support other treatment methods, including local infiltrations and injections of platelet-rich-plasma. Very recently, it was demonstrated that extracorporeal shock wave therapy (ESWT) may accelerate regeneration after acute skeletal muscle injury. The aim of the present study is to test the hypothesis that the combination of radial ESWT (rESWT) and a specific rehabilitation program (RP) is effective and safe in treatment of acute HMC injury type 3b in athletes, and is statistically significantly more effective than the combination of sham-rESWT and RP. METHODS: We will perform a double blind, randomized, sham-controlled clinical trial at the clinic KinEf Kinesiología Deportiva, Ciudad Autónoma de Buenos Aires, Argentina. Forty patients with acute HMC injury type 3b will be randomly allocated to receive either rESWT (nine rESWT sessions; three sessions per week; 2500 radial extracorporeal shock waves (rESWs) per session; energy density depending on what the patient tolerates) or sham-rESWT. In addition, all patients will receive a specific rehabilitation program that will last for 8 weeks. The primary outcome measure will be the individual time (days) necessary to return to play. Secondary outcomes will include the presence or absence of reinjury during a time period of 6 months after inclusion into the study. DISCUSSION: Because of the lack of adequate treatment options for acute HMC injury type 3b in athletes and particularly the high reinjury rate, we hypothesize that the results of this trial will be of importance and have impact on clinical practice. TRIAL REGISTRATION: ClinicalTrials.gov ID NCT03473899 . Registered March 22, 2018.

Photobiomodulation therapy as a tool to prevent hamstring strain injuries by reducing soccer-induced fatigue on hamstring muscles.

Muscle fatigue is a potential risk factor for hamstring strain injuries in soccer players. The aim of this study was to verify the effect of photobiomodulation therapy (PBMT) on the hamstrings' muscle fatigue of soccer players during a simulated match. Twelve male amateur soccer players (~ 25 years) participated in this randomized, crossover, double-blinded, placebo-controlled trial. The volunteers were evaluated in two sessions, with a minimum 7-day interval. At each session, volunteers received either PBMT (300 J per thigh) or placebo treatment on the hamstrings prior to the simulated soccer match. Muscle strength and functional capacity were evaluated through isokinetic dynamometry and countermovement jump (CMJ) tests, respectively, before and immediately after the simulated soccer match. Players had lower reductions on hamstring eccentric peak torque [4.85% (ES = 0.31) vs. 8.72% (ES = 0.50)], hamstring-to-quadriceps torque ratio [3.60% (ES = 0.24) vs. 7.75% (ES = 0.50)], and CMJ height [1.77% (ES = 0.09) vs. 5.47% (ES = 0.32)] when treated with PBMT compared to placebo. Magnitude-based inference supports that PBMT promoted 75%, 69%, and 53% chances for beneficial effects on hamstring eccentric peak torque, hamstring-to-quadriceps torque ratio, and CMJ height, respectively, compared to placebo treatment. In conclusion, PBMT applied before a simulated soccer match proved to be effective in attenuating the hamstrings' muscle fatigue. These findings support PBMT as a promising tool to prevent hamstring strain injury in soccer players.

Hamstring Injuries in Professional Soccer Players: Extent of MRI-Detected Edema and the Time to Return to Play.

BACKGROUND: Discrepancies exist in the literature regarding the association of the extent of injuries assessed on magnetic resonance imaging (MRI) with recovery times. HYPOTHESIS: MRI-detected edema in grade 1 hamstring injuries does not affect the return to play (RTP). STUDY DESIGN: Retrospective cohort study. LEVEL OF EVIDENCE: Level 4. METHODS: Grade 1 hamstring injuries from 22 professional soccer players were retrospectively reviewed. The extent of edema-like changes on fluid-sensitive sequences from 1.5-T MRI were evaluated using craniocaudal length, percentage of cross-sectional area, and volume. The time needed to RTP was the outcome. Negative binomial regression analysis tested the measurements of MRI-detected edema-like changes as prognostic factors. RESULTS: The mean craniocaudal length was 7.6 cm (SD, 4.9 cm; range, 0.9-19.1 cm), the mean percentage of cross-sectional area was 23.6% (SD, 20%; range, 4.4%-89.6%), and the mean volume was 33.1 cm3 (SD, 42.6 cm3; range, 1.1-161.3 cm3). The mean time needed to RTP was 13.6 days (SD, 8.9 days; range, 3-32 days). None of the parameters of extent was associated with RTP. CONCLUSION: The extent of MRI edema in hamstring injuries does not have prognostic value. CLINICAL RELEVANCE: Measuring the extent of edema in hamstring injuries using MRI does not add prognostic value in clinical practice.