Strengthening football: The role of the nordic hamstring exercise in preventing hamstring injuries

BackgroundHamstring strain injuries (HSIs) are among the most common injuries in football, causing significant time-loss and impacting player performance. Despite various preventive strategies, the incidence of HSIs remains high, necessitating evidence-based approaches to reduce injury rates.ObjectiveThis scoping review aims to evaluate the effectiveness of the Nordic Hamstring Exercise (NHE) in reducing the incidence and recurrence of HSIs in football players and to provide practical recommendations for its implementation.MethodsA comprehensive literature search was conducted in PubMed, Scopus, Web of Science, PEDro, and the Cochrane Library. Randomized controlled trials (RCTs) focusing on NHE interventions for football players were included. The primary outcomes were injury incidence, recurrence, and compliance with NHE programs.ResultsThe review found that NHE significantly reduces the incidence of new hamstring injuries by up to 60% and recurrent injuries by up to 85%. Players performing NHE demonstrated a 35% increase in eccentric hamstring strength. Compliance with NHE programs was a critical factor in achieving these outcomes, with higher adherence rates leading to better preventive effects.ConclusionsThe Nordic Hamstring Exercise is an effective, evidence-based intervention for preventing hamstring injuries in football. Its integration into regular training programs, combined with education to improve compliance, can significantly reduce injury rates and enhance player performance. Future research should focus on standardizing protocols and exploring long-term outcomes.

Impact of Nordic hamstring breaking point angle on football player performance

Background

Football demands both aerobic and anaerobic capacities due to its dynamic movements, which include jumps, directional changes, ball control, and sprints. The Nordic hamstring exercise (NHE) enhances eccentric strength, which is crucial for high-intensity movements. However, the relationship between Nordic breaking point angle (NHEbpa), which is associated with eccentric hamstring peak torque during Nordic hamstring exercise, and sprint, countermovement jump (CMJ), and change of direction (COD) speed in soccer players has not been sufficiently investigated.

Objective

This analysis examines the relationship between the Nordic breaking point angle and critical performance indicators-sprint speed, COD ability, and vertical jump-in football players.

Methods

Fifty-eight male soccer players volunteered for the study. Assessments included anthropometric measurements, CMJ tests, 10-20-30 m sprint tests, and COD (zig-zag) tests. NHEbpa was measured using motion analysis software. Correlation analysis was used to determine the relationship between variables. A multiple linear regression analysis was conducted to evaluate the individual effects of the sprint, CMJ, and COD performances on NHEbpa, with data analyzed using JASP 0.18.

Results

Correlation analysis showed strong positive correlations between NHEbpa and sprint performances (r = 0.633 to 0.666), moderate negative correlation between NHEbpa and CMJ (r = -0.406), and moderate positive correlation between NHEbpa and COD (r = 0.580). Regression analysis results were used to analyze the independent coefficients of multiple variables more comprehensively, revealing significant predictors for performance: 20-m sprint (β = 24.166, p = 0.030), 10-m sprint (β = 22.564, p = 0.047), 30-m sprint (β = 10.677, p = 0.027), and CMJ (β = 4.974, p = 0.034). Conversely, COD performance (β = -0.154, p = 0.470) did not demonstrate a significant effect.

Conclusions

The study identified significant relationships between NHEbpa and sprint/CMJ performances (p < 0.05), while no meaningful effect was observed for COD speed (p > 0.05). These findings highlight the importance of eccentric strength in sprint performance, suggesting that other factors may play a more prominent role in COD. Incorporating eccentric-focused training, particularly through Nordic exercises, is recommended to enhance sprint performance and hamstring strength, which are essential for football players.

Regional differences in amplitude and spatial homogeneity of muscle activity in the biceps femoris long head

PURPOSE

Hamstring injuries, particularly in the proximal Biceps femoris long head (BFlh), remain frequent in sports involving sprints and accelerations despite extensive research. Non-uniform muscle activity may contribute to these injuries by causing uneven load distribution. This study examines spatial homogeneity of muscle activity and amplitude in the proximal and distal BFlh at different knee flexion torque levels and muscle-tendon unit (MTU) lengths under controlled isometric conditions.

METHODS

Fifteen male recreational athletes performed unilateral isometric knee flexion contractions at three MTU lengths (0°, 45°, 90° hip flexion) and torque levels (30% MVC90, 60% MVC90, 90%MVC90) with high-density surface electromyography (HDsEMG) assessing proximal and distal activity.

RESULTS

The proximal BFlh exhibited lower spatial homogeneity and amplitude compared to the distal region across all conditions, with the largest homogeneity differences at lower torques and longer MTU lengths. Proximal homogeneity increased with torque and decreased with MTU length, while the distal region remained consistent. Amplitudes were lower proximally and decreased with MTU length in both regions.

CONCLUSION

The proximal-distal differences in spatial homogeneity and amplitude within the BFlh reflect non-uniform activation patterns along the BFlh and the proximal regions lower spatial homogeneity and amplitude of activation reflect non-uniform patterns, possibly contributing to injury risk.

Young male players exhibit higher eccentric hamstring muscle fatigue than females and older males after a basketball match participation

OBJECTIVES

Investigating hamstring eccentric strength before and after a basketball match.

DESIGN

Cohort observational study.

SETTING

Playing facilities of local basketball teams on official championship matches.

PARTICIPANTS

Forty-four healthy male and female 14-25-year-old basketball athletes.

MAIN OUTCOME MEASURES

Hamstring mean, absolute peak torque, and total work were measured during the execution of the Nordic hamstring exercise before and after a match. Anterior knee laxity was also measured.

RESULTS

The results showed non-significant intersex pre- vs. post-match changes for all measured parameters. The 14-19-year-old male players showed a significantly lower post-match mean hamstring peak torque than their 20-25-year-old peers (p = 0.013). Hamstring strength correlated with age in males with the younger players significantly weaker post-match than the older athletes. Younger vs. older males experienced a mean eccentric hamstring peak torque decrease of 16.4 ± 38.18 Nm (-5.6 %) vs. an increase of 27.55 ± 41.87 Nm (11.8 % - Spearman R = 0.408), an absolute eccentric hamstring peak torque reduction of 13.32 ± 35.45 Nm (-4 %) vs. an improvement of 31.5 ± 43.83 Nm (11.6 % - R = 0.434), and a hamstring work decline of 1474.5 ± 1370.83 J (-19.2 %) vs. an increment of 560.32 ± 1584.28 J (13.2 % - R = 0.627) respectively.

CONCLUSIONS

Younger male basketball players were more fatigued post-match compared to their older same-sex peers.

Concurrent Repetitions Overestimate Hamstring:Quadriceps Ratios at Extended Knee Joint Positions: Implications for Clinical Practice

Most measurements of isokinetic hamstring:quadriceps (H:Q) strength ratios are conducted using concurrent repetitions, whereby active knee extension is immediately followed by active knee flexion. To reduce the influence of the stretch-shortening cycle and limit axis misalignment, isolated repetitions have been recommended, whereby extension and flexion are completed separately. To inform screening protocols, this study examined the effect of concurrent and isolated trials on discrete and angle-specific H:Q ratios. Fifteen males (age: 27 ± 4 years; height: 184 ± 9 cm; body mass: 80 ± 9 kg) performed isokinetic tests of the knee flexors and extensors (60°/s) using concurrent and isolated trials while sagittal kinematics were captured (100 Hz). Statistical parametric mapping enabled the effects of protocol type (concurrent vs. isolated) and axis misalignment (uncorrected vs. corrected) to be compared. Uncorrected data resulted in an underestimation of discrete conventional (-10.17%, p < 0.001) and functional (-9.21%, p <  0.05) ratios, with differences being observed for all angle-specific ratios (p < 0.001). The use of concurrent repetitions resulted in a significant overestimation of the conventional H:Q ratio (+7.41%, p < 0.05) with the differences being most prevalent at more extended (24°-45° knee flexion, p < 0.05) knee joint positions. Dynamometer users should be aware that concurrent repetitions increase the likelihood of "false-negative" injury risk categorization. Nevertheless, the common practice of using uncorrected data from concurrent repetitions does not lead to significant differences in discrete or angle-specific H:Q ratios when compared with corrected data obtained from isolated repetitions.

Knee strength balance ratios are not affected by aging among male runners

Objectives

This study aimed to assess thigh muscular strength, conventional and functional strength balance ratios, and muscle quality in well-trained male runners aged 20-70 yr.

Methods

Eighty-nine male runners were divided into five age categories: 20-29, 30-39, 40-49, 50-59, and 60-70 yr. Participants underwent an isokinetic strength test for knee flexor and extensor muscles and a body composition analysis via dual-energy X-ray absorptiometry.

Results

No significant difference was observed in concentric peak torque of the knee extensor muscles between the 20-29 and 40-49 age groups. However, the 50-59 age group showed significantly lower strength than the 20-29 age group (p = 0.049), and the 60-70 age group demonstrated significantly lower strength than the 40-49 group (p < 0.001). The conventional and functional balance ratios remain stable across all age groups.

Conclusion

Knee flexor and extensor strength in male runners decreases significantly after the age of 50, while conventional and functional strength balance ratios remain stable.

Prevention and Rehabilitation of the Athletic Hamstring Injury

Hamstring injuries are a common occurrence in both recreational and competitive athletes. Professional athletes have an increased incidence of hamstring-related injuries because most of these injuries are often attributed to movements involving forceful and rapid hamstring lengthening. The incidence of hamstring injuries is particularly high in professional baseball players, likely due to the high-speed running and frequent transition from static standing to dynamic movements inherent to the sport itself. To improve an athlete's ability to return to sport and minimize days off due to injury, a programmed rehabilitation program combining a range of training parameters that ensure the athlete can work near the limit of their capacity while concurrently allowing sufficient time for the injured tissue to heal is essential. The purpose of this article is to summarize the different features and evaluation of hamstring injuries in athletes, highlight evidence-based rehabilitation interventions, and identify preventative strategies to effectively and efficiently treat athletes, particularly baseball players, with hamstring injuries.

Level of Evidence

Level V, expert opinion.

Effectiveness of Electrical Muscle Elongation and Proprioceptive Neuromuscular Facilitation Programs on Muscle Flexibility and Stiffness in Young Adults with Functional Hamstring Disorder: A Randomized Clinical Trial with 4-Week Follow-Up

BACKGROUND

Adequate hamstring flexibility is crucial for musculoskeletal health as increased muscle tone can lead to stretch-type injuries, muscle weakness, dysfunctional neuromuscular control, postural changes, and lower back pain. The aim was to compare the effectiveness of a program based on Electrical Muscle Elongation (EME), Proprioceptive Neuromuscular Facilitation (PNF), and no intervention in improving flexibility and viscoelastic properties of hamstring and quadriceps muscles in active young adults with functional hamstring disorder (type 2B according to the Munich Consensus).

METHODS

Sixty-five participants (45 male, 20 female) were randomly assigned to three groups: the EME group (n = 21) received a simultaneous combination of interferential current and stretching, the PNF group (n = 22) underwent active stretching, and the Control group (n = 22) received no intervention. Hamstring and quadricep flexibility and muscle stiffness were measured in both limbs at baseline, post-intervention, and at the 4-week follow-up.

RESULTS

The EME group showed significant improvements in hamstring flexibility in the left limb compared to the Control group and in some myotonometric variables of the quadriceps muscle compared to the PNF and Control groups (p < 0.05). Within-groups differences indicated higher improvements in the EME group.

CONCLUSIONS

This study suggests that EME may offer greater benefits than PNF stretching in young adults with functional hamstring disorder.

Supine Bridge Exercise: A Narrative Review of the Literature (Part I)

This article represents the first part of a larger work aimed at exploring the use of the supine bridge exercise (SBE) for both therapeutic and preventive purposes concerning lower back and hip joint pathologies, which will be presented in a subsequent article. The current article presents various execution modes of SBE found in the literature. It discusses what is involved in performing the traditional SBE with different angles at the ankle, knee, hip, and spine. It also addresses SBE variations, such as (1) single-leg; (2) with simultaneous activation of the hip adductors; (3) with simultaneous activation of the hip abductors; (4) with elevated upper trunk support; and (5) with foot-elevated support on a stable or unstable surface. Additionally, it reviews the literature on how different methods of performing the SBE engage muscles responsible for the stability of the hip, pelvis, and lumbar spine, including the gluteus maximus, gluteus medius, hamstrings, erector spinae, multifidus, transversus abdominis, and external oblique. The aim of this article is to serve as a practical guide or "manual" for utilizing SBE across a variety of rehabilitative contexts, providing insights into how the exercise can be adapted to target specific muscles effectively in different clinical scenarios.

3.0-Tesla MRI Observation at Return to Play After Hamstring Injuries

OBJECTIVE

To describe 3.0-Tesla (T) magnetic resonance imaging (MRI) findings of hamstring muscles in clinically recovered athletes who were cleared for return to play (RTP).

DESIGN

Prospective observational study.

SETTING

Hospital.

PARTICIPANTS

Athletes (amateur and professional) who were cleared for RTP after hamstring injury. Fifty-eight participants were included in the analysis.

INDEPENDENT VARIABLES

3-T MRI at baseline (within 7 days from initial injury) and MRI at RTP (within 10 days of RTP).

MAIN OUTCOME MEASURES

Injury location, grade of injury (modified Peetrons and British Athletics Muscle Injury Classification/BAMIC), presence and the extent of intramuscular signal abnormality, intramuscular tendon disruption, and thickness. Reinjuries within 1 year of RTP were recorded.

RESULTS

Magnetic resonance images at RTP showed that 55 (95%) participants had intramuscular increased signal intensity (edema) and 44 (76%) participants had intramuscular abnormal low-signal intensity (suggesting fibrosis) on MRI. There was an overall reduction of injury grades according to the modified Peetrons and BAMIC classification at initial injury to RTP. Three (5%) participants had no abnormal signal intensities (grade 0 or grade 0A) on MRI at RTP. Intramuscular tendon disruption, waviness, and tendon thickening were present at RTP in, respectively, 22 (38%), 15 (26%), and 36 (62%). We recorded 3 (5%) reinjuries.

CONCLUSIONS

At RTP, 3.0-T MRI shows high percentages of MRI abnormalities (edema, fibrosis, and intramuscular tendon disruption and thickening). We conclude that complete normalization of 3.0-T MRI is not expected for RTP decision after a hamstring injury. Its possible association with reinjury risk has to be determined in larger cohorts.

A new field-test for assessing the medial and lateral hamstring strength at long-muscle length

This research investigates the influence of tibial rotations with knee flexion (KF) on the electromyographic (EMG) activities of hamstring muscles (HM) groups and the strength ratio between the medial and lateral rotation of the tibia. A cross-sectional design was employed to assess muscle activity, isometric strength and reliability. The research was conducted in a controlled laboratory environment. Thirty-six amateur male athletes were recruited as volunteers. The measures included peak muscle activity of the semitendinosus and biceps femoris long head, the knee flexors' isometric strength ratio and reliability. The isometric strength ratios of medial (MR) to lateral (LR) tibial rotations were 0.94 ± 0.17 at 90°, and 0.93 ± 0.10 at both 60° and 30° of KF angulation. Tibial position significantly influenced knee flexion strength as well as HM activity, irrespective of KF angulation. Specifically, biceps femoris activity increased by 33.6% in LR compared to MR, while semitendinosus activity increased by 22.6% in MR compared to LR. The Knee-Rotation test (KR-test) can be a valuable tool for evaluating both HM groups (ICC >0.87), and identifying the primary target for strengthening purposes during the injury prevention process. It provides insights for effective rehabilitation and training interventions.

Investigating the effects of previous injury on subsequent training loads, physical fitness, and injuries in youth female basketball players

Background

Previous studies have shown that athletes accustomed to higher chronic workloads are less susceptible to injury than those exposed to lower chronic workloads. However, few studies have evaluated whether previous injury influences them. Therefore, this study investigated the impact of previous injuries on subsequent training loads, physical fitness, and injury rates in female youth basketball players.

Methods

Training load, physical fitness, and injuries of 18 young female basketball players (age 16.8 ± 1.4 years) were monitored. Previous injury status was clustered using the K-means clustering algorithm to separate players into high-risk and low-risk groups. Linear mixed models were used to analyze the effects of previous injury status on subsequent training load and physical fitness. Meanwhile, the differences between the players' injury groups were analyzed.

Results

Previous injury status can significantly impact a player's subsequent training loads, including acute loads, chronic loads, skill-based training loads, training monotony, and training strain (all p < 0.05). The two groups had no significant differences in physical fitness (all p > 0.05). Furthermore, the incidence of non-contact injuries was significantly higher in the high-risk group than low-risk group, which would result in more training time lost (all p < 0.05).

Conclusion

This study identified the impact of previous injury status on subsequent training load, physical fitness, and injuries in youth female basketball players. These findings provide valuable insight for coaches to optimize training loads according to previous injury status, aiming to minimize the likelihood of subsequent injuries.

Analyzing Lower Limb Muscle Imbalance Patterns Associated With Chronic Ankle Instability

OBJECTIVES

 Our main objective was to find a complex relationship between chronic ankle instability (CAI) and factors contributing to lower limb proximal-distal muscle imbalance.

METHODS

 This cross-sectional study, conducted in the physiotherapy department of Krishna Vishwa Vidyapeeth, Karad, included 111 volunteers selected through simple random sampling. Outcome assessments involved manual muscle testing, range of motion evaluation, and gait pattern analysis based on specific inclusion and exclusion criteria.

RESULTS

 The study interpreted that individuals with CAI exhibited significant muscle imbalances on the affected side compared to the unaffected side. Core muscle weakness was present in 97 (87.2%) of patients involving multifidus and rectus abdominals majorly, while 90 (84.6%) experienced lower limb muscle weakness. The ankle joint's range of motion was the most affected, with ankle plantar flexors and evertors showing the greatest weakness. Abnormalities in gait were also noted, with cautious gait observed in 83 (75%) patients, knee hyperextension in 24 (22%), and foot slap in four (3%).

CONCLUSION

 The present study concluded that CAI could cause abnormal gait patterns due to weak muscle strength, impaired muscle length-tension relationships, and reduced range of motion. An efficient core gives optimal efficiency in the entire kinetic chain during movements like acceleration, deceleration, and dynamic stabilization and provides proximal stability to the lower extremities. In the study, lower limb muscle imbalance and core muscle weakness are significant contributors to CAI, impacting both stability and functional performance. Considering the study findings as an important part of patient assessment, it will be used to customize the rehabilitation programs as per the patient's requirement and, thus, enhance positive outcomes.

Acute Changes in Hamstring Injury Risk Factors After a Session of High-Volume Maximal Sprinting Speed Efforts in Soccer Players

BACKGROUND

Maximal sprinting speed (MSS) overexposure is associated with increased risk of injury. This study aimed to describe changes in sprint performance-related factors and hamstring strain injury (HSI) risk factors after a high-volume sprinting session in soccer players.

HYPOTHESIS

A high-volume sprinting session can induce acute changes in several sprint performance-related factors (sprint time and mechanical properties) and HSI risk factors (posterior chain muscle strength, hamstring range of motion, and dynamic lumbo-pelvic control [LPC], measured as changes in anterior pelvic tilt [APT] during maximal speed sprinting).

STUDY DESIGN

Prospective observational case series.

LEVEL OF EVIDENCE

Level 4.

METHODS

Fifteen active male amateur soccer players participated. Changes in sprint performance-related factors and HSI risk factors were examined for 72 hours after high-volume MSS efforts (H-VMSSE) using a soccer-contextualized multifactorial approach. Muscle damage proxy markers (hamstring perceived soreness and creatine kinase) were also examined.

RESULTS

H-VMSSE induced decrements in sprint performance-related factors. Significant reductions in theoretical maximal horizontal velocity (P < 0.01; effect size [ES], -0.71) and performance (P = 0.02; ES, -0.59) were observed for 48 and 72 hours after H-VMSSE. Small but significant reductions in posterior chain muscle force-generating capacity were detected for 48 and 72 hours after H-VMSSE for the nondominant (P < 0.03; ES, -0.60) and dominant (P < 0.04; ES, -0.40) leg. Finally, players exhibited persistent small, albeit nonsignificant (P = 0.06; ES, 0.53), decreases in dynamic LPC (APT increases) for 72 hours after H-VMSSE.

CONCLUSION

H-VMSSE induced declines in both sprint performance-related factors and HSI risk factors. Sprinting can alter a player's anatomic structure by increasing APT during the maximum speed phase of the sprint.

CLINICAL RELEVANCE

A soccer-contextualized multifactorial approach might allow for the regulation of MSS dosage depending on individual HSI risk factor status, thereby serving as a tailored "vaccine" for sprinting needs.

Proximal avulsion of the hamstring in young athlete patients: a case series and review of literature

Hamstring injuries are a frequent occurrence of athletes, leading to a stop in practice and long-term alterations in sports performance. About 12% of these lesions involve avulsion at the level of the proximal insertion that can be complete (about 6%) or partial. Starting from an epidemiological and treatment evaluation of these lesions in literature, the aim of this study was to examine the functional outcomes and the rate of "return to play" in a population composed of athletes of various levels who have undergone surgery to reinsert the hamstring muscles at the ischial insertion, for a complete detachment of one or more tendon heads. Therefore, a retrospective study was carried out where 18 patients treated at the Orthopedics and Traumatology Unit of the I.R.C.C.S. San Matteo in Pavia (Italy) were identified in a time span ranging from March 2012 to August 2020. The sample was analysed taking into account age, sex and risk factors, as well as the pathophysiology and anatomy of the injury using the Wood classification, the time elapsed before surgery, the duration of the rehabilitation protocol and the possible return to sports activity, comparing the level of sports performance in the pre- and post-operative period using the Tegner Activity Score (TAS). Different post-operative outcome evaluation scores (Perth Hamstring Assessment Tool PHAT and Lower Extremity Functional Scale LEFS) were also compared with each other in order to find a correlation with the real level of return to sporting activity. The mean age at surgery was 26.4 11.6 years. The population is composed of 14 males (77.8%) and 4 females (22.2%). All 18 patients returned to sports following surgery (100%). Of these patients, 17 (94%) maintained a level of sports performance equal to that before the injury. 100% of patients rated the outcome of the surgery as satisfactory. This study has shown that Hamstring reinsertion surgery is a correct indication in all athletes, allowing them a satisfactory return to sports practice.

The relationship between sustained hamstring pain and reorganisation of somatosensory representations: a randomised, controlled study

ABSTRACT

Recurrent hamstring injuries are highly prevalent amongst sporting populations. It has been hypothesised that pain from an initial hamstring injury may induce reorganisation of somatosensory representations that could contribute to reinjury. However, because of the cross-sectional nature of existing research, it remains unknown whether somatosensory changes are a cause or effect of pain or if they are driven by other potentially confounding factors. Here, we explored the effect of experimentally induced sustained hamstring pain on tasks that interrogate somatosensory and spatial representations. Fifty healthy participants were randomly allocated to an experimental group that performed an eccentric exercise protocol on the right hamstring to induce delayed onset muscle soreness or a control group performing a repetition-matched concentric exercise protocol. The tactile cortical representation was assessed using two-point discrimination and tactile localisation, whereas the proprioceptive representation was assessed using a left-right judgement task. Peripersonal spatial representations were assessed using an auditory localisation task. Assessments were performed at baseline and day 2. No between-group differences in tactile acuity were observed. However, improvements in left-right judgments and worsening of auditory localisation occurred in the experimental group compared with the control group. This study provides preliminary evidence showing that somatosensory changes occur in response to sustained hamstring pain. Experimentally induced, sustained hamstring pain elicited enhancements in proprioceptive processing and deficits in peripersonal spatial processing, suggesting a shift in the allocation of attentional resources from the external (peripersonal) to internal (body) environment. These findings may hold important implications for reinjury risk and rehabilitation following hamstring pain.

Smaller Biceps Femoris Aponeurosis Size in Legs with a History of Hamstring Strain Injury

Biceps femoris long head (BFLH) aponeurosis size was compared between legs with and without prior hamstring strain injury (HSI) using two approaches: within-group (injured vs. uninjured legs of previous unilateral HSI athletes) and between-group (previously injured legs of HSI athletes vs. legs of No Prior HSI athletes). MRI scans were performed on currently healthy, competitive male athletes with Prior HSI history (n=23;≥1 verified BFLH injury; including a sub-group with unilateral HSI history; most recent HSI 1.6±1.2 years ago) and pair-matched athletes with No Prior HSI history (n=23). Anonymized axial images were manually segmented to quantify BFLH aponeurosis and muscle size. Prior unilateral HSI athletes' BFLH aponeurosis maximum width, aponeurosis area, and aponeurosis:muscle area ratio were 14.0-19.6% smaller in previously injured vs. contralateral uninjured legs (paired t-test, 0.008≤P≤0.044). BFLH aponeurosis maximum width and area were also 9.4-16.5% smaller in previously injured legs (n=28) from Prior HSI athletes vs. legs (n=46) of No Prior HSI athletes (unpaired t-test, 0.001≤P≤0.044). BFLH aponeurosis size was smaller in legs with prior HSI vs. those without prior HSI. These findings suggest BFLH aponeurosis size, especially maximum width, could be a potential cause or consequence of HSI, with prospective evidence needed to support or refute these possibilities.

Early Versus Late Rapid Force Production During Single-Joint Isometric Hamstring Assessment Using Force Plates

ABSTRACT

Ripley, NJ, Barber, R, Fahey, JT, and Comfort, P. Early versus late rapid force production during single-joint isometric hamstring assessment using force plates. J Strength Cond Res 38(12): 2074-2078, 2024-The aim of this study was to assess differences in time-matched early versus late rapid force (RF) development in female soccer players in the 90-90 isometric hamstring assessment. Twenty-one elite female soccer players (age: 20.7 ± 4.7 years; height: 168.2 ± 5.5 cm; body mass: 62.8 ± 7.0 kg), with no recent (>6 months) history of hamstring strain injury, volunteered to participate in the study. Following a standardized warm-up, each subject performed 3 maximal isometric unilateral hamstring contractions, with their heel resting on a force plate, elevated on a box, to ensure that their hips and knees were at 90°. Data were analyzed to determine peak force, early RF (ERF) 0-100 milliseconds and late RF (LRF) 100-200 milliseconds. Significant and large differences were observed in the percentage of peak force achieved between ERF (52.85 ± 11.53%; 54.99 ± 9.80%) and LRF (15.82 ± 5.58%; 15.25 ± 3.91%) for the left and right limbs, respectively ( p < 0.001, g = 2.13-3.06). The large differences between ERF and LRF can be used by practitioners to streamline performance assessment, which in turn will allow practitioners to act upon data collected more effectively. Additionally, regular monitoring ERF production could inform practitioners of any interventions that maybe required, such as reduction of load or introduction of specific recovery modalities and during return to play protocols.

The Single Leg Bridge Test Does Not Measure Isolated Hamstring Endurance in Healthy Men

Background

The Single Leg Bridge Test (SLBT) is commonly described as a measure of 'hamstring endurance'. Nevertheless, the relationship between the SLBT score and isolated hamstring endurance remains uncertain.

Purpose

This study aimed to investigate the correlation between SLBT scores and isolated hamstring endurance in healthy men. Additionally, the study aimed to assess the correlation between the limb symmetry index obtained from the SLBT and hamstring endurance test results.

Design

Cross-sectional study.

Methods

Forty healthy and physically active men were evaluated at the research laboratory on two separate occasions, with a minimum interval of 48 hours between visits. During each visit, participants performed either the single-leg balance test (SLBT) or the hamstring endurance test on an isokinetic dynamometer, which involved 30 concentric knee flexion repetitions performed at maximum intensity, with an angular velocity of 120°/s and a range of motion of 90°. Correlations were analyzed between SLBT scores and hamstring fatigue indexes provided by peak torque and work outcomes.

Results

The SLBT score (27±7 reps) demonstrated no significant correlation with isolated hamstring endurance, as measured by isokinetic peak torque (52±9%; p=0.737, r=-0.038) or work (57±9%; p=0.489, r=0.078). Likewise, the limb symmetry index obtained from the SLBT (99±12%) did not significantly correlate with index from the hamstring endurance test: peak torque (107±26%; p=0.540, r=-0.100) and work (102±18%; p=0.849, r=0.031).

Conclusion

The SLBT does not appear to be a suitable tool for measuring isolated hamstring endurance in healthy men.

Level of evidence

3.

Intramuscular Hamstring Stiffness Affects Anatomically Modeled Localized Muscle Strain During Passive Hip Flexion

ABSTRACT

Rehbein, CO, McDougle, JM, Peñailillo, L, and Earp, JE. Intramuscular hamstring stiffness affects anatomically modeled localized muscle strain during passive hip flexion. J Strength Cond Res 38(11): 1860-1866, 2024-Hamstring strain injuries occur when localized tissue strain capacity is exceeded. Localized strain may be affected by intramuscular variation in stiffness, but research in this area is lacking. The purpose of this study was to determine the effects of intramuscular hamstring stiffness on localized muscle strain during passive hip flexion. Twenty-eight (age 25.0 ± 4.9 years) healthy women ( n = 15) and men ( n = 13) had biceps femoris, semitendinosus, and semimembranosus stiffness measured proximally, medially, and distally during passive hip flexion and extension using shear-wave elastography. Anthropometric and stiffness measurements were entered into an anatomical model of equivalent springs to estimate localized tissue strain and differentiate between the relative contribution to passive strain from each muscular region. In shortened and stretched positions, stiffness was lowest proximally for all muscles (Cohen's d = 0.66-0.79, p < 0.001). In addition, relative strain contribution was greater proximally (37.5-39.4%) compared with middle (31.74-32.2%) or distal (28.6-30.3%) regions ( p < 0.001), with proximal contribution to strain increasing with greater hip flexion. Our results suggest that intramuscular variations in passive hamstring stiffness contribute to inhomogeneous strain throughout the muscle during passive hip flexion. Given the prevalence of proximal stretch-pattern strain injuries, variation in intramuscular stiffness may contribute to risk for such injuries.

Novel Ultrasound-Guided Sub-Piriformis Injection (SPI) May Produce Effective Analgesia for Both Open and Arthroscopic Hamstring Repair: A Case Report

Open or arthroscopic repair of hamstring tear requires both hard and soft, posterior and proximal thigh analgesia. Regional injections to completely relieve this unique pain are not available to the best of our knowledge. We present a novel, single injection, performed under ultrasound guidance, that utilizes the deep piriformis space. This space contains multiple nerves involved in the surgery and can be completely anesthetized with only 10 ml of local anesthetic. We further extended the block for a total of 80 hours through the use of liposomal bupivacaine.

Multiscale hamstring muscle adaptations following 9 weeks of eccentric training

BACKGROUND

Eccentric training, such as Nordic hamstring exercise (NHE) training, is commonly used as a preventive measure for hamstring strains. Eccentric training is believed to induce lengthening of muscle fascicles and to be associated with the addition of sarcomeres in series within muscle fibers. However, the difficulty in measuring sarcomere adaptation in human muscles has severely limited information about the precise mechanisms of adaptation. This study addressed this limitation by measuring the multiscale hamstring muscle adaptations in response to 9 weeks of NHE training and 3 weeks of detraining.

METHODS

Twelve participants completed 9 weeks of supervised NHE training, followed by a 3-week detraining period. We assessed biceps femoris long-head (BFlh) muscle fascicle length, sarcomere length, and serial sarcomere number in the central and distal regions of the muscle. Additionally, we measured muscle volume and eccentric strength at baseline, post-training, and post-detraining.

RESULTS

NHE training over 9 weeks induced significant architectural and strength adaptations in the BFlh muscle. Fascicle length increased by 19% in the central muscle region and 33% in the distal muscle region. NHE also induced increases in serial sarcomere number (25% in the central region and 49% in the distal region). BFlh muscle volume increased by 8%, and knee flexion strength increased by 40% with training. Following 3 weeks of detraining, fascicle length decreased by 12% in the central region and 16% in the distal region along with reductions in serial sarcomere number.

CONCLUSION

Nine weeks of NHE training produced substantial, region-specific increases in BFlh muscle fascicle length, muscle volume, and force generation. The direct measurement of sarcomere lengths revealed that the increased fascicle length was accompanied by the addition of sarcomeres in series within the muscle fascicles.

Performing Lower-Limb Strength Exercises Before or After Training Does not Influence Fatigue Indices in Competitive Youth Soccer Players

ABSTRACT

Gantzer, C, Huff, D, Butterick, B, Chalmers, S, Marshall, P, Lovell, R, and Siegler, JC. Performing lower-limb strength exercises before or after training does not influence fatigue indices in competitive youth soccer players. J Strength Cond Res 38(10): 1760-1767, 2024-A multicenter approach was used to conduct a controlled, laboratory-based study ( Part A ) in conjunction with an ecologically focused, field-based study ( Part B ) of the influence of timing on hamstring fatigue induced by lower-limb strength exercises. Part A required players to perform the FIFA 11+ warm-up before a simulated soccer training session, whereas the other session involved removing the lower-limb strength exercises from the warm-up and delivering them after the simulated session. For Part B , players completed 2 live training sessions, where one session included the Nordic hamstring exercise (NHE) as part of a standardized warm-up before training and the other session incorporated the NHE at the end of training. Maximal hamstring force (MVC), rate of force development (RFD), countermovement jump (CMJ), and sprint speed (SS) were assessed before, during, and after the simulation and field training, respectively, to quantify fatigue across both study cohorts. There was no suggestion that timing of the intervention had an influence fatigue in either Part A or B , with no condition (MVC [ Part A & B ]: p > 0.43; RFD: p = 0.43; CMJ: p = 0.10; SS: p = 0.62), time (MVC: p > 0.30; RFD: p = 0.72; CMJ: p = 0.87; SS: p = 0.85), or interactions (MVC: p > 0.93; RFD: p = 0.78; CMJ: p = 0.99; SS: p = 0.94) evident. Our findings suggest youth soccer coaches should not be concerned with the timing of interventions, allowing them to focus instead on adherence and player buy-in.

Comparing activity of the gluteus maximus and hamstring muscles in fatigue conditions between hamstring injury-experienced and inexperienced individuals

INTRODUCTION

Muscle fatigue is considered a risk factor for hamstring injury (HSI), which occurs during high-speed running. To decrease this risk, higher gluteal muscle activity may have a role to play. This study aimed to compare the muscle activities of the gluteus maximus (GMax) and hamstring (HS) muscles between HSI-experienced and inexperienced people in pre- and post-fatigue conditions during the swing and stance phases of running.

METHODS

Participants were asked to run 13 sets of 20 km/h on the treadmill. GMax and HS muscle activities of the (i) injured and (ii) uninjured legs in the HSI-experienced group and (iii) dominant leg (healthy leg) in the inexperienced group were collected using the first run as pre-fatigue data, and the last (13th) run as post-fatigue data.

RESULTS

GMax activity of the injured legs was higher than in the healthy leg during the stance phase in pre-fatigue condition (p < 0.05). The activity of the GMax and semitendinosus were higher in the uninjured legs than in the healthy legs during the swing phase in pre-fatigue condition (p < 0.05). However, no differences in muscle activities between pre- and post-fatigue or the injured and uninjured legs were found.

CONCLUSION

The GMax may prevent HSI recurrence during the stance phase of running. The GMax and semitendinosus of the uninjured leg may act as stabilizers of the body while the injured leg is placed on the ground.

Landing error scoring system: A scoping review about variants, reference values and differences according to sex and sport

OBJECTIVE

The Landing Error Scoring System (LESS) is a movement analysis tool proposed to identify the risk of anterior cruciate ligament injuries, very useful for injury prevention. The aim of this study is to review the variants of the LESS, their normative scores and the differences according to sex and sport practiced.

METHODS

PubMed, Scopus and ScienceDirect databases were searched from inception to October 19, 2023. Studies were eligible if the objective was finding normative or reference scores for the LESS, analyze the differences between sexes or sports, or used some variant of the test. Results were limited to available full-text articles published in English in peer-reviewed journals.

RESULTS

Of the 360 articles identified, 20 were included for a full analysis (18,093 participants, age = 8-30 years, males = 70.6%). The military population was the most frequently analyzed (7 studies, n = 16,603). Results showed six variants of the LESS and average values ranged from 2.56 to 7.1. Males and females showed different pattern landing with errors in different planes.

CONCLUSIONS

Our findings highlight the need for more field studies on LESS reference scores, particularly for females and basketball or hockey players. Further research is required before conducting a systematic review and meta-analysis.

Epidemiology of Hamstring Tears in National Collegiate Athletic Association Athletes: Findings From the National Collegiate Athletic Association Injury Surveillance Program Between 2014/2015 and 2018/2019

OBJECTIVE

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

DESIGN

Descriptive epidemiology study. Athletic trainers from NCAA schools reported injuries to the NCAA Injury Surveillance Program.

SETTING

A convenience sample of NCAA hamstring tear injuries during the 2014/2015 through 2018/2019 academic years.

PATIENTS OR PARTICIPANTS

NCAA student-athletes.

INDEPENDENT VARIABLES

Sport, sex, event type, season segment, injury history, and activity at the time of injury.

MAIN OUTCOME MEASURES

Injury counts, rates, and proportions were used.

RESULTS

Two thousand ninety-six hamstring tears from 8 474 400 athlete-exposures (AEs) were reported (2.47 per 10 000 AEs). Rates were highest in Men's Soccer (5.97 per 10 000 AEs) and Women's Soccer (3.13 per 10 000 AEs), among all Men's and Women's sports, respectively. Competition-related rates in Men's and Women's sports were highest in 2015 to 2016 then followed a decreasing pattern across the remainder of the study period. Among sex-comparable sports, rates were higher in men's (compared with women's) Baseball/Softball, Soccer, and Track and Field. The prevalence of recurrent injuries was comparable among men's (14.8%) and women's (11.5%) sports. Time loss hamstring tears were more prevalent in Men's sports than Women's sports [injury proportion ratio = 1.33; 95% confidence interval, (1.21, 1.47)].

CONCLUSIONS

Overall, hamstring tear rates were higher across all Men's sports compared with Women's sports. Rates across event type were comparable in several sports; and so, adjustments to practice are needed considering that practice environments are more modifiable than competitions. Indeed, improving hamstring tear prevention programs to reduce the burden of this injury in NCAA athletes remains critical.

Prognosticating Return-To-Play Time Following a Hamstring Strain Injury Using Early Flexibility Asymmetry and Musculoskeletal Ultrasound Imaging Outcomes: An Exploratory Study Among Canadian University Football Players

OBJECTIVE

Identify key flexibility and point-of-care musculoskeletal ultrasound (POCUS) measures for prognosticating return-to-play (RTP) following a first hamstring strain injury (HSI) and informing the clinical decision-making process.

DESIGN

Exploratory prospective cohort study.

SETTING

Sport medicine and rehabilitation clinic of a Canadian university.

PARTICIPANTS

One hundred and sixty-seven elite Canadian university football athletes followed over 5 seasons.

INTERVENTIONS

Clinical and POCUS measures collected within 7 days after HSI and preseason clinical measures.

MAIN OUTCOME MEASURES

Active knee extension (AKE) and Straight Leg Raise (SLR) to quantify hamstring flexibility, POCUS-related outcomes to characterize tissue alteration, and RTP until full sport resumption were documented (categorized as Early [1-40 days] or Late [>40 days] RTP).

RESULTS

A total of 19 and 14 athletes were included in the Early RTP (mean RTP = 28.84 ± 8.62 days) and Late RTP groups (mean 51.93 ± 10.54 days), respectively, after having been diagnosed with a first HSI. For the clinical results, height and a greater flexibility asymmetry measure with the AKE or SLR when compared with both ipsilateral preseason and acute contralateral values significantly increases the chance of facing a long delay before returning to play (ie, RTP). For the POCUS-related results, the Peetrons severity score, extent of the longitudinal fibrillary alteration, and novel score lead to similar results.

CONCLUSIONS

Early hamstring flexibility asymmetry following acute HSI, particularly the AKE, along with some POCUS-related measures are valuable in prognosticating late RTP following among Canadian university football athletes.

Hamstring Injuries, From the Clinic to the Field: A Narrative Review Discussing Exercise Transfer

PURPOSE

The optimal approach to hamstring training is heavily debated. Eccentric exercises reduce injury risk; however, it is argued that these exercises transfer poorly to improved hamstring function during sprinting. Some argue that other exercises, such as isometric exercises, result in better transfer to running gait and should be used when training to improve performance and reduce injury risk. Given the performance requirements of the hamstrings during the terminal swing phase, where they are exposed to high strain, exercises should aim to improve the torque production during this phase. This should improve the hamstrings' ability to resist overlengthening consequently, improving performance and limiting strain injury. Most hamstring training studies fail to assess running kinematics postintervention. Of the limited evidence available, only eccentric exercises demonstrate changes in swing-phase kinematics following training. Studies of other exercise modalities investigate effects on markers of performance and injury risk but do not investigate changes in running kinematics.

CONCLUSIONS

Despite being inconsistent with principles of transfer, current evidence suggests that eccentric exercises result in transfer to swing-phase kinematics. Other exercise modalities may be effective, but the effect of these exercises on running kinematics is unknown.

Visualisation of Studies on Knee Injuries in Football: A Bibliometric Analysis

Football is a popular sport on a global scale, and injuries sustained by football players have become a significant concern for sports physicians and researchers. Among these injuries, knee injuries are a commonly encountered problem in football players with long-term effects. This paper aims to perform a visual mapping and a bibliometric analysis of research on knee injuries in football, examining the current state and research trends. For this purpose, all publications from the Social Sciences Citation Index (SSCI), Science Citation Index Expanded (SCIE), Emerging Sources Citation Index (ESCI), and Arts & Humanities Citation Index (AHCI) within the Web of Science database were analysed. VOSviewer 1.6.18 was utilised for visualising bibliometric data. A total of 2159 publications were included in the study. The analysis covers publication year, authors, citation counts, and distributions among publishing journals. Authors, institutions, and international relationships were investigated, and keyword analysis, bibliometric coupling, and co-citation network analyses were conducted. The findings reveal that the United States and Australia are the countries with the highest number of publications. From 2018, there has been a noticeable increase in the number of publications. Citation and publication counts reached their peak in 2021. Turkey takes the 28th rank in terms of citation and centrality. The keywords "soccer," "football," "knee", and "anterior cruciate ligament" were found to be intensively used with high centrality. In conclusion, visual mapping through bibliometric analysis highlights the magnitude and diversity of research in the field of knee injuries in football. It emphasises the need for further studies in this area for future researchers, shedding light on important research areas. Moreover, it provides insights into the prevention of such injuries in football players and the development of effective treatment strategies by fostering more knowledge and understanding of knee injuries.

Relationships between quantitative magnetic resonance imaging measures at the time of return to sport and clinical outcomes following acute hamstring strain injury

Hamstring strain injuries (HSI) are a common occurrence in athletics and complicated by high rates of reinjury. Evidence of remaining injury observed on magnetic resonance imaging (MRI) at the time of return to sport (RTS) may be associated with strength deficits and prognostic for reinjury, however, conventional imaging has failed to establish a relationship. Quantitative measure of muscle microstructure using diffusion tensor imaging (DTI) may hold potential for assessing a possible association between injury-related structural changes and clinical outcomes. The purpose of this study was to determine the association of RTS MRI-based quantitative measures, such as edema volume, muscle volume, and DTI metrics, with clinical outcomes (i.e., strength and reinjury) following HSI. Spearman's correlations and Firth logistic regressions were used to determine relationships in between-limb imaging measures and between-limb eccentric strength and reinjury status, respectively. Twenty injuries were observed, with four reinjuries. At the time of RTS, between-limb differences in eccentric hamstring strength were significantly associated with principal effective diffusivity eigenvalue λ1 (r = -0.64, p = 0.003) and marginally associated with mean diffusivity (r = -0.46, p = 0.056). Significant relationships between other MRI-based measures of morphology and eccentric strength were not detected, as well as between any MRI-based measure and reinjury status. In conclusion, this preliminary evidence indicates DTI may track differences in hamstring muscle microstructure, not captured by conventional imaging at the whole muscle level, that relate to eccentric strength.

Unique advantages of dynamic l-[11C]methionine PET/CT for assessing the rate of skeletal muscle protein synthesis: A pilot trial in young men

Although the standard method to evaluate skeletal muscle protein synthesis (MPS) is muscle biopsy, the method is invasive and problematic for multisite use. We conducted a small pilot study in volunteers to investigate changes in MPS according to skeletal muscle site using a noninvasive method in which 6 healthy young men were given yogurt (containing 20 g milk protein) or water, and 1 h later, l-[11C]methionine ([11C]Met) was administered intravenously. Dynamic PET/CT imaging of their thighs was performed for 60 min. The influx constant Ki of [11C]Met in skeletal muscle protein was calculated as an index of MPS using a Patlak plot, and found to be 0.6%-28% higher after ingesting yogurt than after water in 5 of the 6 volunteer participants, but it was 34% lower in the remaining participant. Overall, this indicated no significant increase in Ki after ingesting milk protein. However, when the quadriceps and hamstring muscles were analyzed separately, we found a significant difference in Ki. This demonstrates the potential of visualizing MPS by calculating the Ki for each voxel and reconstructing it as an image, which presents unique advantages of [11C]Met PET/CT for evaluating MPS, such as site-specificity and visualization.

Hamstring Muscle Stiffness in Athletes with and without Anterior Cruciate Ligament Reconstruction History: A Retrospective Study

Introduction: Sports requiring sprinting, jumping, and kicking tasks frequently lead to hamstring strain injuries (HSI). One of the structural risk factors of HSI is the increased passive stiffness of the hamstrings. Anterior cruciate ligament (ACL) injury history is associated with a 70% increase in the incidence of HSI, according to a recent meta-analysis. The same report recommended that future research should concentrate on the relationships between the HSI risk factors. Hence, the present study aimed to retrospectively compare changes in the passive stiffness of the hamstrings in athletes with and without ACL reconstruction history. Methods: Using ultrasound-based shear-wave elastography, the mid-belly passive muscle stiffness values of the biceps femoris long head, semimembranosus, and semitendinosus muscles were assessed and compared amongst athletes with and without a history of ACL reconstruction. Results: There were no significant differences in the biceps femoris long head (injured leg (IL): 26.19 ± 5.28 KPa, uninjured contralateral (UL): 26.16 ± 7.41 KPa, control legs (CL): 27.64 ± 5.58 KPa; IL vs. UL: p = 1; IL vs. CL: p = 1; UL vs. CL: p = 1), semimembranosus (IL: 24.35 ± 5.58 KPa, UL: 24.65 ± 8.35 KPa, CL: 22.83 ± 5.67 KPa; IL vs. UL: p = 1; IL vs. CL: p = 1; UL vs. CL, p = 1), or semitendinosus (IL: 22.45 ± 7 KPa, UL: 25.52 ± 7 KPa, CL: 22.54 ± 4.4 KPa; IL vs. UL: p = 0.487; IL vs. CL: p = 1; UL vs. CL, p = 0.291) muscle stiffness values between groups. Conclusions: The passive mid-muscle belly stiffness values of the biceps femoris long head, semitendinosus, and semimembranosus muscles did not significantly differ between previously injured and uninjured athletes; therefore, further assessment for other muscle regions of hamstrings may be necessary. To collect more comprehensive data related to the structural changes that may occur following ACL reconstructions in athletes, a future study should examine the passive stiffness of wider muscle regions from origin to insertion.

Acute effects of Nordic hamstring exercise on hip and knee joints proprioception

BACKGROUND AND OBJECTIVES

Nordic Hamstring Exercise (NHE) is one of the best exercises proposed for injury prevention of hamstring muscles. However, its effects on lower extremity proprioception are unclear. The aim of this study was to investigate the immediate effects of a single bout of NHE on hip and knee joints' proprioception.

METHODS

Forty collegiate male soccer players participated in this study with a mean age of 22.85 ± 1.82 years and were randomized into either control (n = 20) or experimental (n = 20) groups. Each subject participated in pre-test measurements in which hip and knee active joints position sense (JPS) were assessed in standing and lying tasks using the image-capturing method. The experimental group then performed three sets of NHE with 10 repetitions in each set, while the control group rested for 10 min. Paired and independent t-tests were used for calculating the differences within and between groups on SPSS software, respectively. The level of significance was P ≤ 0.05.

RESULTS

Hip JPS in the lying task and knee JPS in both of the standing and lying tasks were impaired significantly after performing a single bout of NHE (P ≤ 0.05). However, the effects of this exercise on hip JPS in the standing task were not significant (P ≥ 0.05).

CONCLUSIONS

NHE performing with three sets of 10 repetitions can significantly impair hip and knee JPS immediately after exercise and reduce the proprioception acuity of the lower limbs. It is recommended to perform this exercise at a time rather than before training or match sessions.

Posterior thigh muscles activity during the active H-test: An electromyographic and kinematic analysis

The Askling's H-test is considered a useful return to play criterion after a hamstring muscle injury (HMI). However, it assesses only the active and passive flexibility of posterior thigh muscles. This may lead the practitioner to underestimate a compensation or abnormal movement pattern. The aim of this study was to analyze these kinematic aspects and their reliability, and evaluate the hamstring (HM) and gluteus maximus (GM) muscles' activities. Twelve healthy male volunteers were tested during two session of three trials for passive and active tests. Dynamic flexibility (97.2 ± 6.0°) was significantly greater than the passive one (70.5 ± 14.7°) (p < 0.001), and good intra-individual reproductibility for most kinematic characteristics was observed. Biceps Femoris long head, semitendinosus and GM mean activities (20.1 ± 11.2%; 14.3 ± 7.3% and 25.2 ± 22.1%, respectively) were found to be low to moderate, indicating that only a moderate level of activity occurred during the active H-test, in comparison to other movements such as sprinting itself. In addition, the activity of the posterior thigh muscles during the active H-test appeared to be variable among the volunteers. These findings suggest that the H-test should be interpreted on an individual basis rather than relying on general characteristics, and be considered as an intermediate tool before more strenuous activities such as returning to sprint. With this comprehensive approach, clinicians can gain a more accurate understanding of their patients' progress and make more informed decisions about their readiness to return to play.

Practitioners' perspective of non-contact injury risk factors and injury prevention programming in professional North American male soccer

OBJECTIVE

To evaluate non-contact injury prevention strategies of professional men's soccer clubs in elite North American league soccer. To understand the application, perceived effectiveness and barriers to implementation.

DESIGN

Online cross-Sectional Study.

SETTING

North American elite soccer teams.

PARTICIPANTS

96 medical and performance support staff of elite North American teams.

MAIN OUTCOME MEASURE

The survey consisted of 20 questions and captured 1) practitioners' demographics; 2) perceptions of risk factors; 3) the use of assessment and monitoring strategies; and 4) perceptions of the implementation of injury prevention programmes'.

RESULTS

Injury prevention programmes were perceived as 'effective' (Median 4, Interquartile range 4-4) and reduced injury rates (n = 94, 98%, 95 CI% 93 to 99). A range of potential risk factors were rated as "very important" (4.58 ± 0.52 Likert scale points; mean ± standard deviation). A multi-disciplinary approach to the design, application and monitoring of programmes was generally adopted. Competing training priorities (n = 75, 78%, 95 CI% 69 to 85) and game schedules (n = 71, 74%, 95 CI% 64 to 82) were the most prevalent barriers to injury prevention implementation.

CONCLUSIONS

Injury prevention programmes were perceived as effective in reducing non-contact injuries. Managing the conflicting priorities between scheduling training, tactical and conditioning goals were considered the key barriers to desired implementation.

Diffusion tensor imaging of hamstring muscles after acute strain injury and throughout recovery in collegiate athletes

OBJECTIVE

To identify the region of interest (ROI) to represent injury and observe between-limb diffusion tensor imaging (DTI) microstructural differences in muscle following hamstring strain injury.

MATERIALS AND METHODS

Participants who sustained a hamstring strain injury prospectively underwent 3T-MRI of bilateral thighs using T1, T2, and diffusion-weighted imaging at time of injury (TOI), return to sport (RTS), and 12 weeks after RTS (12wks). ROIs were using the hyperintense region on a T2-weighted sequence: edema, focused edema, and primary muscle injured excluding edema (no edema). Linear mixed-effects models were used to compare diffusion parameters between ROIs and timepoints and limbs and timepoints.

RESULTS

Twenty-four participants (29 injuries) were included. A significant ROI-by-timepoint interaction was detected for all diffusivity measures. The edema and focused edema ROIs demonstrated increased diffusion at TOI compared to RTS for all diffusivity measures (p-values < 0.006), except λ1 (p-values = 0.058-0.12), and compared to 12wks (p-values < 0.02). In the no edema ROI, differences in diffusivity measures were not observed (p-values > 0.82). At TOI, no edema ROI diffusivity measures were lower than the edema ROI (p-values < 0.001) but not at RTS or 12wks (p-values > 0.69). A significant limb-by-timepoint interaction was detected for all diffusivity measures with increased diffusion in the involved limb at TOI (p-values < 0.001) but not at RTS or 12wks (p-values > 0.42). Significant differences in fractional anisotropy over time or between limbs were not detected.

CONCLUSION

Hyperintensity on T2-weighted imaging used to define the injured region holds promise in describing muscle microstructure following hamstring strain injury by demonstrating between-limb differences at TOI but not at follow-up timepoints.

Hamstrings on focus: Are 72 hours sufficient for recovery after a football (soccer) match? A multidisciplinary approach based on hamstring injury risk factors and histology

This study aimed to assess acute and residual changes in sprint-related hamstring injury (HSI) risk factors after a football (soccer) match, focusing on recovery within the commonly observed 72-h timeframe between elite football matches. We used a multifactorial approach within a football context, incorporating optical and ultrastructural microscopic analysis of BFlh (biceps femoris long head) muscle fibres, along with an examination of BFlh fibre composition. Changes in sprint performance-related factors and HSI modifiable risk factors were examined until 3 days after the match (MD +3) in 20 football players. BFlh biopsy specimens were obtained before and at MD +3 in 10 players. The findings indicated that at MD +3, sprint-related performance and HSI risk factors had not fully recovered, with notable increases in localized BFlh fibre disruptions. Interestingly, match load (both external and internal) did not correlate with changes in sprint performance or HSI risk factors nor with BFlh fibre disruption. Furthermore, our study revealed a balanced distribution of ATPase-based fibre types in BFlh, with type-II fibres associated with sprint performance. Overall, the results suggest that a 72-h recovery period may not be adequate for hamstring muscles in terms of both HSI risk factors and BFlh fibre structure following a football match.

The Role of Platelet-Rich Plasma Injection for Muscle Strains in Athletes

Muscle tears/strains are among the most common musculoskeletal injuries, posing a serious challenge for sports medicine. Aiming to reduce the time to return to play and the rate of reinjuries, apart from the traditional conservative treatments and rehabilitation protocols, new and innovative therapeutic options have emerged, particularly platelet-rich plasma (PRP). This study aims to present the available evidence regarding PRP injection for the treatment of muscle strains in athletes. Two databases were searched for articles published between January 2012 and December 2022 in Portuguese or English. The query used for the PubMed database was ("Muscles/injuries"[Mesh]) AND ("Athletes"[Mesh] OR "Athletic Injuries"[Mesh]) AND "Platelet-Rich Plasma"[Mesh], while for the Web of Science database the search was performed for "Platelet-rich plasma" AND "Muscle injuries" AND ("Athletes" OR "Athletic injuries"). Eleven studies involving athletes diagnosed with muscle injuries who received treatment with PRP injection alone, or in combination with traditional conservative treatment, compared to a control group, were included. Four randomized controlled trials, four systematic reviews/meta-analyses, two retrospective studies, and one comparative study were included. Current evidence from the highest-quality studies does not support the hypothesis of reduction of time to return to play and the rate of reinjuries after PRP injection, even though some studies reported positive results. However, the available evidence suggests that PRP might have a beneficial effect on the pain perceived by athletes following an acute muscle strain. It is challenging to arrive at definitive conclusions and translate these findings into a clinical context for treating muscle strains in athletes. The existing trials present several inconsistencies and limitations, with a heterogeneous set of patients and injuries, as well as the use of different and inconsistent methods for preparing, administering, and measuring the effects of PRP. To achieve consistent outcomes, standardizing PRP administration procedures is essential.

Eccentric Hamstring Strength Imbalance among Football and Soccer Athletes

OBJECTIVES

Hamstring strain injuries (HSI) are common among football and soccer athletes. Eccentric strength imbalance is considered a contributing factor for HSI. There is, however, a paucity of data on hamstring imbalances of soccer and American football athletes as they age and advance in skill level. High school athletes will display greater interlimb discrepancies compared with collegiate and professional athletes. In addition, soccer athletes will exhibit greater hamstring asymmetry than American football athletes.

METHODS

Hamstring testing was performed on soccer and American football athletes using the NordBord Hamstring Testing System (Vald Performance, Albion, Australia). Age, sex, weight, sport specialization, and sport level were recorded. Maximum hamstring forces (N), torque (N · m), and work (N · s) were measured. Hamstring imbalance (%) was calculated by dividing the absolute value of the difference in leg forces divided by their sum. One-way analysis of variance and independent sample t tests compared measurements between athlete groups.

RESULTS

A total of 631 athletes completed measurements, including 88 high school male soccer, 25 college male soccer, 23 professional male soccer, 83 high school female soccer, 28 college female soccer, 288 high school football, and 96 college football athletes. High school soccer players displayed significantly greater imbalances for torque (P = 0.03) and work (P < 0.01) than football athletes. Imbalances for maximum force (P = 0.035), torque (P = 0.018), and work (P = 0.033) were significantly higher for male soccer athletes in high school compared with college- and professional-level athletes. Female high school soccer players had significantly higher imbalance in torque (P = 0.045) and work (P = 0.001) compared with female collegiate soccer players. Football athletes did not experience significant changes in force imbalances between skill levels.

CONCLUSIONS

High school soccer athletes exhibit greater hamstring imbalances than football athletes. Higher levels of play in soccer, for both male and female athletes, correlate with less hamstring asymmetry.

Hamstring Injuries: A Paradigm for Return to Play

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

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.

The Effect of Combining Blood Flow Restriction with the Nordic Hamstring Exercise on Hamstring Strength: Randomized Controlled Trial

(1) Background: It is a matter of curiosity what effect the blood flow restriction (BFR) method, which is usually combined with low-intensity resistance exercises, will have when used with high-intensity eccentric exercises. (2) Methods: The present study examined the effects of combining BFR with nordic hamstring exercises (NHEs) on hamstring muscle strength, bilateral deficit (BLD), and training volume. Thirty young female volleyball players, who trained three times a week, participated voluntarily in the study. These players were stratified into three groups, each comprising ten individuals: a control group (CG), an NHE group, and an NHE + BFR group. Hamstring muscle strength and BLD values were determined using an H-BORD device, while training volume was measured in terms of sets and repetitions. (3) Results: Statistical analysis revealed that there were no statistically significant differences in non-dominant and dominant leg peak torque parameters in the exercise groups (F = 2.65; p = 0.097; ηp2 = 0.17; F = 1.15; p = 0.0334; ηp2 = 0.084), while the total training volume was lower in the NHE + BFR group. (4) Conclusions: As a result, it was seen that adding the BFR method to NHE did not provide additional gains. However, due to the low training volume of BFR + NHE, it may be recommended to apply BFR together with NHE to athlete groups.

MRI radiomics for hamstring strain injury identification and return to sport classification: a pilot study

OBJECTIVE

To determine if MRI-based radiomics from hamstring muscles are related to injury and if the features could be used to perform a time to return to sport (RTS) classification. We hypothesize that radiomics from hamstring muscles, especially T2-weighted and diffusion tensor imaging-based features, are related to injury and can be used for RTS classification.

SUBJECTS AND METHODS

MRI data from 32 athletes at the University of Wisconsin-Madison that sustained a hamstring strain injury were collected. Diffusion tensor imaging and T1- and T2-weighted images were processed, and diffusion maps were calculated. Radiomics features were extracted from the four hamstring muscles in each limb and for each MRI modality, individually. Feature selection was performed and multiple support vector classifiers were cross-validated to differentiate between involved and uninvolved limbs and perform binary (≤ or > 25 days) and multiclass (< 14 vs. 14-42 vs. > 42 days) classification of RTS.

RESULT

The combination of radiomics features from all diffusion tensor imaging and T2-weighted images provided the most accurate differentiation between involved and uninvolved limbs (AUC ≈ 0.84 ± 0.16). For the binary RTS classification, the combination of all extracted radiomics offered the most accurate classification (AUC ≈ 0.95 ± 0.15). While for the multiclass RTS classification, the combination of features from all the diffusion tensor imaging maps provided the most accurate classification (weighted one vs. rest AUC ≈ 0.81 ± 0.16).

CONCLUSION

This pilot study demonstrated that radiomics features from hamstring muscles are related to injury and have the potential to predict RTS.

Association Between Total Genotype Score and Muscle Injuries in Top-Level Football Players: a Pilot Study

BACKGROUND

Recently, genetic predisposition to injury has become a popular area of research and the association between a few single nucleotide polymorphisms (SNPs) and the susceptibility to develop musculoskeletal injuries has been shown. This pilot study aimed to investigate the combined effect of common gene polymorphisms previously associated with muscle injuries in Italian soccer players.

RESULTS

A total of 64 Italian male top football players (age 23.1 ± 5.5 years; stature 180.2 ± 7.4 cm; weight 73.0 ± 7.9 kg) were genotyped for four gene polymorphisms [ACE I/D (rs4341), ACTN3 c.1729C > T (rs1815739), COL5A1 C > T (rs2722) and MCT1 c.1470A > T (rs1049434)]. Muscle injuries were gathered for 10 years (2009-2019). Buccal swabs were used to obtain genomic DNA, and the PCR method was used to genotype the samples. The combined influence of the four polymorphisms studied was calculated using a total genotype score (TGS: from 0 to 100 arbitrary units; a.u.). A genotype score (GS) of 2 was assigned to the "protective" genotype for injuries, a GS of 1 was assigned to the heterozygous genotype while a GS of 0 was assigned to the "worst" genotype. The distribution of genotype frequencies in the ACE I/D (rs4341), ACTN3 c.1729C > T (rs1815739) and MCT1 c.1470A > T (rs1049434) polymorphisms was different between non-injured and injured football players (p = 0.001; p = 0.016 and p = 0.005, respectively). The incidence of muscle injuries was significantly different among the ACE I/D (rs4341), ACTN3 c.1729C > T (rs1815739) and COL5A1 C > T (rs2722) genotype groups, showing a lower incidence of injuries in the "protective" genotype than "worse" genotype (ACE, p < 0.001; ACTN3, p = 0.005) or intermediate genotype (COL5A1, p = 0.029). The mean TGS in non-injured football players (63.7 ± 13.0 a.u.) was different from that of injured football players (42.5 ± 12.5 a.u., p < 0.001). There was a TGS cut-off point (56.2 a.u.) to discriminate non-injured from injured football players. Players with a TGS beyond this cut-off had an odds ratio of 3.5 (95%CI 1.8-6.8; p < 0.001) to suffer an injury when compared with players with lower TGS.

CONCLUSIONS

These preliminary data suggest that carrying a high number of "protective" gene variants could influence an individual's susceptibility to developing muscle injuries in football. Adapting the training load parameters to the athletes' genetic profile represents today the new frontier of the methodology of training.

Surgical treatment of distal hamstring tendon injuries yield a higher return-to-sports rate: A systematic review

PURPOSE

The purpose of this study is to compare the patient-reported outcomes and return to sports of the conservative and surgical treatment of distal hamstring tendon injuries.

METHODS

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines, two reviewers searched PubMed, Scopus and Virtual Health Library databases in January 2023. Clinical studies evaluating conservative or surgical management outcomes of distal hamstring tendon injuries were considered eligible for this systematic review if predefined criteria were fulfilled: (1) published in English or Spanish; (2) evaluated any of the following: patient-reported outcomes, return-to-sports rate (RTS-R) or return-to-sports time (RTS-T). Data were presented in tables using absolute values from individual studies and derived pooled percentages.

RESULTS

Eighteen studies were included for 67 patients and 68 distal hamstring tendon injuries. Initially, 39 patients (58.2%) underwent surgical treatment, whereas 28 (41.8%) were treated conservatively. Among conservative treatment patients, 15 failed and had to be operated on (53.6%), all with distal semitendinosus tendon injuries. Anchor fixation was the technique of choice in 20 lesions (36.4%), tenodesis in 16 (29.1%), tenectomy in 14 (25.5%) and sutures were preferred in five (9%). Thirteen out of 28 patients (46.4%) undergoing initial conservative treatment returned to sports at a mean of 3.6 months (range 1 week to 12 months), in contrast to surgical treatment, in which 36 out of 39 patients (92.3%) returned at a mean of 4.2 months (range 6 weeks to 12 months). Additionally, 14 of 15 patients (93.3%) converted to surgical treatment after failed conservative treatment returned to sports at a mean of 7.6 months after injury.

CONCLUSION

Initial surgical treatment of distal hamstring tendon injuries yields a high RTS-R (92.3%) at a mean of 4.2 months. Furthermore, 15 out of 28 patients (53.6%) initially treated conservatively had to be operated on, delaying the RTS-T (mean 7.6 months after injury) without affecting their RTS-R.

LEVEL OF EVIDENCE

IV.

Relationships Between Modifiable Risk Factors of Hamstring Strain Injury

ABSTRACT

Ripley, NJ, Comfort, P, and McMahon, JJ. Relationships between modifiable risk factors of hamstring strain injury. J Strength Cond Res 38(3): 510-516, 2024-The aims of this study were to determine whether any relationship exists between eccentric hamstring strength and isokinetic strength imbalances and bicep femoris long head (BF LH ) architecture. Eighteen physically active men (age 24.7 ± 4.3 years, height 181.9 ± 7.2 cm, mass 84.9 ± 12.9 kg) had resting BF LH muscle architecture assessed using ultrasound, with images taken at the midmuscle belly. Measures of isokinetic strength of the knee extensors and flexors involved subjects performing 3 maximal effort repetitions of concentric knee extension and eccentric knee flexion at 60°·s -1 . Good-excellent relative reliability (intraclass correlation coefficient ≥0.86) and low variability (coefficient of variation <10%) were observed for all variables. Relative BF LH fascicle length (FL) demonstrated significant moderate-to-nearly-perfect associations with isokinetic measures identified as hamstring strain injury risk factors ( p < 0.05, r = 0.38-0.92), whereas absolute BF LH FL was not significantly or meaningfully associated with isokinetic measures ( p = 0.07-0.961, r = 0.01-0.30). Relative BF LH FL should be considered when assessing resting BF LH muscle architecture because it is potentially a more appropriate measure of injury risk because of its greater association with strength measures. However, absolute BF LH FL may have a greater usefulness during growth, maturation, and individual proportions.

Anterior pelvic tilt increases hamstring strain and is a key factor to target for injury prevention and rehabilitation

PURPOSE

Hamstring muscle strain injury is very common in sports involving high-speed running. Hamstring muscles originate from the ischial tuberosity and thus pelvic position may influence hamstring strain during different sports movements like sprinting, but this has only been evaluated by indirect methods. This study tested the hypothesis that a change in anterior pelvic tilt causes elongation of the overall hamstring complex and disproportionately elongates proximal relative to distal muscle regions.

METHODS

Seven fresh-frozen specimens (full lower limb with pelvis and lumbar spine) were used for this in vitro study. Specimens were dissected to enable visualization of the hamstring muscles and then fixed into a custom-made testing bench that allowed controlled movement of the pelvis over a fixed femur and tibia. Nine markers were inserted into the hamstring muscles to allow intra- and intermuscle difference measurements. Then, six different anterior pelvic angles were used to measure the difference in hamstring muscle lengthening through a three-dimensional reconstruction system based on stereoscopic machine vision technology.

RESULTS

An increase in anterior pelvic tilt produced a significant non-uniform increase in tissue elongation in all regions of the three hamstring muscles (semitendinosus, semimembranosus [SMB] and biceps femoris long head), which was greater in the proximal (>1 cm every 5°) compared to the distal region (≈0.4 cm every 5°). At the proximal hamstring region, SMB showed significantly greater length changes compared to conjoint tendons with nonstatistically significant elongation differences between muscles at the distal region.

CONCLUSION

Considering the results of the study, the pelvis segment will likely play a fundamental role as a strain regulator of hamstring muscles. These results will have an impact on injury rehabilitation and prevention processes of hamstring injuries, as well as optimize future musculoskeletal models and avoid potential underestimation of the hamstring muscle-tendon complex lengthening during high-speed running.

LEVEL OF EVIDENCE

N/A.

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

INTRODUCTION

Hamstring strain injuries (HSI) and re-injuries are endemic in high-speed running sports. The biceps femoris long head (BFlh) is the most frequently injured muscle among the hamstrings. Structural parameters of the hamstring muscle are stated to be susceptible to strain injuries at this location. This retrospective study targeted comparing the BFlh's structural parameters between previously injured and uninjured athletes.

METHODS

Nineteen male athletes with previous BFlh strain injury history and nineteen athletes without former lower extremity injury history were included in this study. Fascicle length, mid-muscle belly and distal musculotendinous (MTJ) passive stiffnesses of the biceps femoris long head (BFlh) were examined via b-mode panoramic ultrasound scanning and ultrasound-based shear-wave elastography. Parameter comparisons of both legs within and between athletes with and without injury history were performed.

RESULTS

Comparison of the BFlh fascicle length between the injured leg of the injured group and the legs of the controls revealed a trend to shorter fascicle lengths in the injured leg (p = 0.067, d = -0.62). However, the mid-muscle belly passive stiffness of the BFlh was significantly higher in the injured legs (p = 0.009, d = 0.7) compared with the controls. Additionally, the distal MTJ stiffness was much higher in the previously injured legs compared with controls (p < 0.001, d = 1.6).

CONCLUSIONS

Outcomes support the importance of BFlh properties related to stiffness, and fascicle length for injury susceptibility in athletes. Future prospective studies should determine whether the higher stiffness in the injured athletes is a cause or consequence of the HSI. Physical therapy and rehabilitation programmes after HSI should focus on BFlh muscle properties i.e., elasticity and fascicle length for reducing re-injury and increasing sports performance.

The effects of eccentric training on hamstring flexibility and strength in young dance students

The objective of this research is to examine the impact of eccentric training on hamstring flexibility and strength in young dancers during the concluding stages of their foundational dance training program. A total of 24 female, second-year dance students from Hebei Normal University were selected as participants. They were divided into three distinct groups: Nordic hamstring exercise and single-leg deadlift group (NHE&SLD), forward bending exercises and standing leg lift group (FBE&SLL), and a control group (CG). The study was designed around a 6-week training regimen. An isokinetic dynamometer was used to measure seated knee flexor-extensor strength, while electronic goniometry was employed to measure hamstring flexibility in the supine position. Paired sample t-tests were conducted within each group, and one-way analysis of covariance (ANCOVA) was utilized for comparisons between groups. In the NHE&SLD group, significant disparities were observed in both concentric (T = - 5.687, P = 0.001) and eccentric (T = - 3.626, P = 0.008) hamstring strength pre and post-intervention. The pre-intervention dominant leg concentric strength test values significantly influenced the post-intervention outcomes (F = 5.313, P = 0.001, η2 = 0.840). Similarly, the pre-intervention dominant leg eccentric strength test values impacted the post-intervention results (F = 4.689, P = 0.043, η2 = 0.190). Following the intervention, the NHE&SLD group displayed marked changes in the active straight leg raising angle on both left (T = - 4.171, P = 0.004) and right (T = - 6.328, P = 0.001) sides. The FBE&SLL group also revealed significant changes in the active straight leg raising angle on both left (T = - 4.506, P = 0.003) and right (T = - 4.633, P = 0.002) sides following the intervention. The pre-intervention left leg concentric strength test value significantly influenced the post-intervention outcomes (F = 25.067, P = 0.001, η2 = 0.556). Likewise, the pre-intervention right leg eccentric strength test value significantly influenced the post-intervention results (F = 85.338, P = 0.01, η2 = 0.810). Eccentric training can better enhance the flexibility and strength of hamstring muscles in dance students. Traditional stretching training significantly improves the flexibility of the hamstring muscles. Eccentric training has more training benefits than traditional stretching training. It is recommended for dance students to use eccentric training when increasing hamstring flexibility and strength.