An anatomical and histological study of the structures surrounding the proximal attachment of the hamstring muscles

Anatomical Relationships of the Proximal Attachment of the Hamstring Muscles with Neighboring Structures: From Ultrasound, Anatomical and Histological Findings to Clinical Implications

BACKGROUND

Injuries of the proximal attachment of the hamstring muscles are common. The present study aimed to investigate the relationship of the proximal attachment of the hamstring muscles with neighboring structures comprehensively.

METHODS

A total of 97 hemipelvis from 66 cryopreserved specimens were evaluated via ultrasound, anatomical and histological samples.

RESULTS

The proximal attachment of the hamstring muscles presents a hyperechogenic line surrounding the origin of the semimembranosus and the long head of the biceps femoris muscles, as well as another hyperechogenic line covering the sciatic nerve. The anatomical and histological study confirms the ultrasound results and shows different layers forming the sacrotuberous ligament. Furthermore, it shows that the proximal attachment of the semimembranosus muscle has a more proximal origin than the rest of the hamstring muscles. Moreover, this muscle shares fibers with the long head of the biceps femoris muscle and expands to the adductor magnus muscle. The histological analysis also shows the dense connective tissue of the retinaculum covering the long head of the biceps femoris and semimembranosus muscles, as well as the expansion covering the sciatic nerve.

CONCLUSIONS

These anatomical relationships could explain injuries at the origin of the hamstring muscles.

Effects of simultaneous short-term neuromuscular electrical stimulation and static stretching on calf muscles

[Purpose] The simultaneous application of static stretching and neuromuscular electrical stimulation (NMES) to calf muscles may enhance physiological parameters in young and healthy individuals; however, the efficacy of this intervention and potential sex variation remain to be elucidated. The present study aimed to investigate these aspects. [Participants and Methods] Thirty healthy university students (15 males and 15 females) participated in this study. All participants simultaneously underwent static stretching and NMES of the calf muscles for 4 min while lying on an upright and tilted table. The mean differences in the dorsiflexion angle (DFA), finger-floor distance (FFD), and straight leg raising (SLR) angle before and after the intervention were calculated. Sex variations were assessed using a two-way analysis of variance (ANOVA). [Results] The DFA, FFD, and SLR angle exhibited significant effects on time. No significant sex variations were observed between the groups. [Conclusion] Simultaneous static stretching and NMES of the calf muscles potentially enhanced the DFA, FFD, and SLR angle in healthy university students, irrespective of sex.

The direct muscular origin of the semitendinosus: a pitfall in categorization of proximal hamstring tendon tears

The ischial origin of the hamstring musculature is complex. While the conjoint tendon and semimembranosus are commonly discussed and understood by radiologists, there is a lesser-known origin of the semitendinosus along the inferior and medial surface of the ischium in the form of a broad direct muscular connection. This secondary origin is infrequently described in the radiology literature and is a potential pitfall during grading of semitendinosus injuries if the interpreting physician is unaware of its presence. In a proximal hamstring tendon tear, the direct muscular origin of the semitendinosus can be spared, torn along with the conjoint tendon, or remain intact and contribute to a vertical shearing injury of the semitendinosus myotendinous junction. Detailed knowledge of this anatomy and its imaging appearance in the setting of injury enables the reader to correctly diagnose these unique hamstring injuries.

Exploring the Role of Sprint Biomechanics in Hamstring Strain Injuries: A Current Opinion on Existing Concepts and Evidence

Hamstring strain injuries are one of the most common injuries in sprint-based sports with the mechanism of injury considered the result of an interaction between applied mechanical strain and the capacity of the muscle to tolerate strain. To date, injury prevention and rehabilitation strategies have frequently focused on enhancing the capacity of the hamstrings to tolerate strain, with little consideration of factors directly influencing mechanical strain. Sprint running biomechanics are one factor proposed to influence the mechanical strain applied to the hamstrings that may be modified (towards reduced strain) within rehabilitation and injury prevention programs. This article aims to explore the theoretical mechanistic link between sprint running mechanics and hamstring strain injury, along with the available supporting evidence. In doing so, it hopes to provide practitioners with an understanding of mechanical parameters that may influence hamstring strain injury whilst also identifying areas for further research exploration.

Effect of thoracic mobilization exercises on hamstring flexibility: a randomized controlled trial

Background and aim

The aim was to investigate the effect of thoracic mobilization exercises on hamstring flexibility.

Materials and methods

One hundred twenty individuals with hamstring tightness were included in the study. The participants were randomized into two groups: the experimental group (EG) (n = 60) or the control group (CG) (n = 60). The EG performed a home-based thoracic mobilization exercise program comprising 2 sets with 10 repetitions, once a day, 3 days a week, for 4 weeks. The CG performed active-assisted stretching of the hamstring comprising 3 sets with 10 repetitions for 15 seconds. The active knee extension (AKE) test was used to measure hamstring flexibility, and self-reported hamstring pain intensity was evaluated with a visual analog scale (VAS). All evaluations were conducted at the beginning and end of the intervention.

Results

Both groups showed significant improvement in AKE (p<0.05). Pain intensity during the stretching exercises was significantly decreased only in the EG. The improvements in AKE and VAS score were greater in the EG than in the CG (p < 0.05). Between-group effect sizes were large for AKE (d = 1.075) and VAS score (d = 1.077).

Conclusion

The current study showed that thoracic mobilization exercises may increase hamstring flexibility and reduce pain intensity during hamstring stretch exercises.

Foam Rolling vs. Proprioceptive Neuromuscular Facilitation Stretching in the Hamstring Flexibility of Amateur Athletes: Control Trials

BACKGROUND

the use of stretching techniques in the sports world is frequent and common thanks to their many effects. One of the main benefits of stretching is an increased range of motion (ROM). Recently, the use of a foam roller has spread in sports practice due to benefits that are similar to those of shoes observed in stretching. The objective of the following study was to compare the results of proprioceptive neuromuscular facilitation stretching (PNF) with foam rolling (FR).

METHODS

The design of the study was a single-blind, randomized controlled trial (clinicaltrial.gov NCT05134883), and the participants were 80 healthy young athletes. The range of motion was evaluated with a modified sit-and-reach test before, during (at 30 s), and at the end of the intervention (at 2 min). The subject's discomfort sensation was measured using the Borg scale. Effect sizes were calculated using Cohen's d coefficient. Volunteers were randomized into the PNF group or FR group.

RESULTS

the differences were statistically significant (p < 0.001) during the intervention in favor of PNF group. The differences at the end of intervention showed that the PNF group had a greater increase in flexibility, with this difference being statically significant (p < 0.001). The sensation of perceived exertion with PNF at the end of the intervention was similarly classified as moderate for both groups.

CONCLUSION

Despite the fact that the use of FR is spreading in the field of sports and rehabilitation, the results of the present study suggest that the gain in flexibility in the hamstrings is greater if PNF-type stretches are used instead of FR.

The gracilis and semitendinosus muscles: a morphometric study on 18 specimens with clinical implications

INTRODUCTION

The pes anserinus consists of the sartorius, semitendinosus, and gracilis muscles. They coalesce together with the leg fascia to form the anserine plate. The semitendinosus and gracilis both form the deep layer of this plate and are clinically relevant for ligament reconstruction. The aim of the study is to report a detailed morphometric evaluation of the semitendinosus and gracilis muscles and assess their clinical implications.

METHODS

Using a rigorous dissection process on 18 cadaveric hips, measurements of both the semitendinosus and gracilis muscles with bone parameters were conducted. We measured the following: (a) total femur, femoral shaft, and neck lengths, (b) total muscle lengths, and (c) intra-muscular and extra-muscular (free) tendon lengths. Correlation values between bone variables, muscle variables, and in-between muscle variables were computed.

RESULTS

The total muscle and the distal intra-muscular tendon length of the St and Gr are correlated with the total femur length. When compared to gracilis, the total muscle and distal intra-muscular tendon lengths of the ST are much better correlated with the total femur length. The free distal tendon length for both muscles did not show a significant correlation with any of the femoral bone lengths.

CONCLUSION

The variability of tendon length of the ST/Gr poses a significant challenge to surgeons. This study reports a detailed morphometric evaluation of the ST/Gr hamstring muscle and tendons. It revealed a positive correlation between the femoral length and the ST/Gr graft lengths. This could help orthopedic surgeons in predicting the graft lengths pre-operatively and develop better planning for reconstructive surgeries.

Does Self-Myofascial Release Cause a Remote Hamstring Stretching Effect Based on Myofascial Chains? A Randomized Controlled Trial

BACKGROUND

The hamstring muscles are described as forming part of myofascial chains or meridians, and the superficial back line (SBL) is one such chain. Good hamstring flexibility is fundamental to sporting performance and is associated with prevention of injuries of these muscles. The aim of this study was to measure the effect of self-myofascial release (SMR) on hamstring flexibility and determine which segment of the SBL resulted in the greatest increase in flexibility.

METHODS

94 volunteers were randomly assigned to a control group or to one of the five intervention groups. In the intervention groups, SMR was applied to one of the five segments of the SBL (plantar fascia, posterior part of the sural fascia, posterior part of the crural fascia, lumbar fascia or epicranial aponeurosis) for 10 min. The analyzed variables were hamstring flexibility at 30 s, 2, 5, and 10 min, and dorsiflexion range of motion before and after the intervention.

RESULTS

Hamstring flexibility and ankle dorsiflexion improved when SMR was performed on any of the SBL segments. The segments with the greatest effect were the posterior part of the sural fascia when the intervention was brief (30 s to 2 min) or the posterior part of the crural fascia when the intervention was longer (5 or 10 min). In general, 50% of the flexibility gain was obtained during the first 2 min of SMR.

CONCLUSIONS

The SBL may be considered a functional structure, and SMR to any of the segments can improve hamstring flexibility and ankle dorsiflexion.

Can We Modify Maximal Speed Running Posture? Implications for Performance and Hamstring Injury Management

PURPOSE

Sprint kinematics have been linked to hamstring injury and performance. This study aimed to examine if a specific 6-week multimodal intervention, combining lumbopelvic control and unning technique exercises, induced changes in pelvis and lower-limb kinematics at maximal speed and improved sprint performance.

METHODS

Healthy amateur athletes were assigned to a control or intervention group (IG). A sprint test with 3-dimensional kinematic measurements was performed before (PRE) and after (POST) 6 weeks of training. The IG program included 3 weekly sessions integrating coaching, strength and conditioning, and physical therapy approaches (eg, manual therapy, mobility, lumbopelvic control, strength and sprint "front-side mechanics"-oriented drills).

RESULTS

Analyses of variance showed no between-group differences at PRE. At POST, intragroup analyses showed PRE-POST differences for the pelvic (sagittal and frontal planes) and thigh kinematics and improved sprint performance (split times) for the IG only. Specifically, IG showed (1) a lower anterior pelvic tilt during the late swing phase, (2) greater pelvic obliquity on the free-leg side during the early swing phase, (3) higher vertical position of the front-leg knee, (4) an increase in thigh angular velocity and thigh retraction velocity, (5) lower between-knees distance at initial contact, and (6) a shorter ground contact duration. The intergroup analysis revealed disparate effects (possibly to very likely) in the most relevant variables investigated.

CONCLUSION

The 6-week multimodal training program induced clear pelvic and lower-limb kinematic changes during maximal speed sprinting. These alterations may collectively be associated with reduced risk of muscle strain and were concomitant with significant sprint performance improvement.

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.

Biceps Femoris Activation during Hamstring Strength Exercises: A Systematic Review

BACKGROUND

The aim of the study was to systematically evaluate the biceps femoris long head activation across cross-sectional hamstring strength exercise studies.

METHODS

A systematic review design was followed. The search strategy conducted in PubMed, Cochrane Library, and Web of Sciences databases found a total of 3643 studies. Once inclusion and exclusion criteria were applied, 29 studies were finally included in this systematic review. A total of 507 participants and 114 different exercises were analyzed. Exercises were evaluated individually and grouped into several categories: Nordics, isokinetic exercises, lunges, squats, deadlifts, good mornings, hip thrusts, bridges, leg curls, swings, hip and back extensions, and others.

RESULTS

Results showed the isokinetic and Nordic exercises as the categories with highest biceps femoris activation (>60% of Maximal Voluntary Isometric Contraction). Nordic hamstring exercise ankle dorsiflexion was the exercise that achieved the highest biceps femoris long head activation (128.1% of its Maximal Voluntary Isometric Contraction).

CONCLUSIONS

The results from this systematic review suggest that isokinetic and Nordic exercises seem to be the best option to activate biceps femoris long head. Future studies evaluating the implementation of these exercises in prevention programs are needed.

Effects of Diacutaneous Fibrolysis on Passive Neuromuscular Response and Mechanosensitivity in Athletes with Hamstring Shortening: A Randomized Controlled Trial

Introduction. Diacutaneous Fibrolysis is defined as specific instrumental intervention to normalize function in the musculoskeletal system. It is considered a treatment method for the mechanical alterations of the locomotor system, and it is widely used in sports for therapeutic and preventive purposes. Despite the clinical benefits observed in different musculoskeletal conditions, the action mechanism of diacutaneous fibrolysis remains uncertain. There are no studies evaluating the neuromuscular response on the posterior muscular chain of the lower extremity in athletes, where overload, stiffness, and injury incidence are high. Objective. To evaluate the immediate, and 30 min post treatment effects of a single diacutaneous fibrolysis session on passive neuromuscular response and mechanosensitibity on hamstring and gluteus in athletes with shortening. Design. A randomized within participant clinical trial. Methods. Sixty-six athletes with hamstring shortening were included (PKE < 160). The lower limbs were randomized between the experimental limb and control limb, regardless of dominance. A single session of diacutaneous fibrolysis was applied to the posterior gluteus maximus, biceps femoris, and semitendinosus of the experimental lower limb whereas the control limb was not treated. Viscoelastic muscle properties (myotonometry), contractile muscle properties (tensomiography), and mechanosensitivity (algometry) were tested before treatment (T0), after treatment (T1), and 30 min post treatment (T2). Results. Regarding viscoelastic properties, in the intra-group analysis we found statistically significant differences in the experimental limb at T1, decreasing muscle stiffness in gluteus maximus (p < 0.042), in biceps femoris (p < 0.001) and in semitendinosus (p < 0.032). We also observed statistically significant differences in Tone decrease (p < 0.011) and relaxation increase (p < 0.001) in biceps femoris. At T2, the decrease in stiffness in all tested muscles was maintained (p < 0.05). There were statistically significant inter-groups differences in stiffness on gluteus (p < 0.048) and biceps femoris (p < 0.019) and in tone on biceps femoris (p < 0.009) compared to the control limb. For contractile properties, we only found statistically significant differences on maximal radial displacement (Dm) in gluteus, both control and experimental at T2 (p < 0.05) and in biceps femoris control (p < 0.030). No changes were found in the mechanosensitivity. Conclusions. A single session of diacutaneous fibrolysis produces changes in some parameters related to viscoelasticity properties of the biceps femoris and gluteus. There were no changes on contractile properties on semitendinosus. Only small changes on the contractile properties on the gluteus maximus and biceps femoris were found. No effect was found on the mechanosensitivity of the posterior chain muscles in athletes with hamstring shortening.

Sonographic measures and sensory threshold of the normal sciatic nerve and hamstring muscles

PURPOSE

The sciatic nerve innervates the hamstring muscles. Occasionally, the sciatic nerve is injured along with a hamstring muscle. Detailed biomechanical and sensory thresholds of these structures are not well-characterized. Therefore, we designed a prospective study that explored high-resolution ultrasound (US) at multiple sites to evaluate properties of the sciatic nerve, including cross-sectional area (CSA) and shear-wave elastography (SWE). We also assessed SWE of each hamstring muscle at multiple sites. Mechanical algometry was obtained from the sciatic nerve and hamstring muscles to assess multi-site pressure pain threshold (PPT).

METHODS

Seventy-nine asymptomatic sciatic nerves and 147 hamstring muscles (25 males, 24 females) aged 18-50 years were evaluated. One chiropractic radiologist with 4.5 years of US experience performed the evaluations. Sciatic nerves were sampled along the posterior thigh at four sites obtaining CSA, SWE, and algometry. All three hamstring muscles were sampled at two sites utilizing SWE and algometry. Descriptive statistics, two-way ANOVA, and rater reliability were assessed for data analysis with p ≤ 0.05.

RESULTS

A significant decrease in sciatic CSA from proximal to distal was correlated with increasing BMI (p < 0.001). Intra-rater and inter-rater reliability for CSA was moderate and poor, respectively. Elastographic values significantly increased from proximal to distal with significant differences in gender and BMI (p = 0.002). Sciatic PPT significantly decreased between sites 1 and 2, 1 and 3, and 1 and 4. Significant correlation between gender and PPT was noted as well as BMI (p < 0.001). Hamstring muscle elastographic values significantly differed between biceps femoris and semitendinosus (p < 0.001) and biceps femoris and semimembranosus (p < 0.001). All three hamstring muscles demonstrated increased PPT in males compared to females (p < 0.001). In addition, PPT of the biceps femoris correlated with BMI (p = 0.02).

CONCLUSION

High-resolution US provided useful metrics of sciatic nerve size and biomechanical properties. PPT for the normal sciatic nerve and hamstring muscles was obtained for future clinical application.

Thermal and Current Flow Effects of a Capacitive-Resistive Electric Transfer Application Protocol on Chronic Elbow Tendinopathy. A Cadaveric Study

Lateral elbow tendinopathy, or "tennis elbow," is a pathology that affects around 1.3% of the general population. Capacitive-resistive electric transfer therapy aims to provoke temperature and current flow changes in superficial and deep tissues. The aim of this in vitro study was to analyze the thermal behavior and transmission of electric current on the superficial and deep tissues of the elbow during the application of different modalities of a capacitive-resistive electric transfer treatment protocol for chronic elbow tendinopathy. A cross-sectional study was designed; five fresh cryopreserved cadavers (10 elbows) were included in this study. A 30 min intervention was performed based on a protocol commonly used in clinics for the treatment of chronic lateral elbow tendinopathy by diathermy using the "T-Plus." Common extensor tendon, radiohumeral capsule, and superficial temperatures were registered after each application for the duration of the 30 min treatment protocol. During all applications, we observed a current flow of over 0.03 A. The protocol showed a statistically significant increase in superficial temperature by 24% (5.02°) (p < 0.005), the common extensor tendon by 19.7% (4.36°) (p < 0.007), and the radiohumeral joint capsule by 17.5% (3.41°) (p < 0.005) at the end of the 30 min protocol compared with the baseline temperature. The different applications of the protocol showed specific effects on the temperature and current flow in the common extensor tendon and radiohumeral capsule. All applications of the protocol produced a current flow that is associated with the generation of cell proliferation. These results strengthen the hypothesis of cell proliferation and thermal changes in deep and distal structures. More studies are needed to confirm these results.

Training-induced changes in anterior pelvic tilt: potential implications for hamstring strain injuries management

An association has been reported between dynamic anterior pelvic tilt (APT) and hamstring injuries; however, no research has examined if a training-based preventive intervention could alter APT. Therefore, the aim of the present study was to examine if a specific 6-week multimodal intervention, based on the theoretical influence of neighbouring joints and biomechanical interactions between muscles that are inserted to the pelvis, induced changes in APT, during walking gait, hamstring flexibility and trunk endurance. Thirty-five active healthy males volunteered for this single-blind controlled trial and were split into two groups based on baseline data: a control group (CG, n = 20, continued their normal physical activities), and an intervention group (IG, n = 15, performed the intervention programme for 18 sessions over 6 weeks). A significant (p = 0.001) decrease in the APT kinematics during gait, significant increase in the Active Knee Extension Test (p = 0.001), and a significant increase in trunk endurance performance for flexion (p = 0.001), extension (p = 0.001) and side bridge (p = 0.001) were observed, in IG after the 6-week programme, compared to CG.

Differential movement of the sciatic nerve and hamstrings during the straight leg raise with ankle dorsiflexion: Implications for diagnosis of neural aspect to hamstring disorders

INTRODUCTION

In hamstrings injuries, sciatic nerve and muscle disorders can coexist. Therefore, differential diagnosis to include or exclude nerve involvement is an important aspect of evaluation. The objective of this paper is to investigate the mechanical behaviour of the sciatic nerve and biceps femoris muscle in the proximal thigh with the ankle dorsiflexion manoeuvre at different degrees of hip flexion during the straight leg raise in cadavers.

MATERIAL AND METHODS

A cross-sectional study was carried out. Linear displacement transducers were inserted into the sciatic nerve and the biceps femoris muscle of 11 lower extremities from 6 fresh cadavers to measure potential strain of both structures during ankle dorsiflexion at 0°, 30°, 60° and 90° of hip flexion during the straight leg raise. Excursion was also measured with a digital calliper.

RESULTS

Ankle dorsiflexion resulted in significant strain and distal excursion of the sciatic nerve at all ranges of hip flexion during the straight leg raise (p < 0.05). In contrast, the ankle movement did not affect the strain in biceps femoris at any position of the hip (p > 0.05).

CONCLUSION

Ankle dorsiflexion at different degrees of hip flexion during the straight leg raise produces changes in the strain and excursion of the sciatic nerve in the upper thigh. In contrast, the biceps femoris muscle at the same location was not affected by ankle movement. These findings show differential behaviour between the nerve and muscle with ankle dorsiflexion at this location that could be used as differential diagnosis in posterior hip pain.

Effectiveness of low-frequency electrical stimulation in proprioceptive neuromuscular facilitation techniques in healthy males: a randomized controlled trial

BACKGROUND

Hamstring muscle injuries are common in the sports field, with lack of hamstring flexibility being a risk factor. Stretching the hamstring muscles is an important part of the training and rehabilitation programs used to prevent or treat injury and improve performance. We aim to compare the immediate and follow-up effect on hamstring muscle flexibility between 2 different stretching protocols, proprioceptive neuromuscular facilitation (PNF) stretching and PNF stretching combined with electrostimulation. A second aim is to determine whether physical activity level is related to flexibility.

METHODS

Design of study: Single-blind, randomized controlled trial; Participants: 30 healthy volunteers (30 men, 18-39 years old); Intervention: A 6-session intervention program spanning over 2 weeks and 1-week and 3-week follow-up. The control group underwent PNF stretching with a voluntary contraction. The experimental group underwent PNF stretching but the muscle contraction was triggered with an electrical stimulation device (TENS); Main outcome measu: Hamstring muscles flexibility was assessed using the Modified Sit and Reach (MSR) and the Back Saver Sit and Reach (BSSR) tests. Physical activity level was evaluated with the short form of the International Physical Activity Questionnaire (IPAQ).

RESULTS

Both groups showed an overall increase in hamstring muscle flexibility. However, when comparing flexibility gain between baseline and the end of the stretching program (session 6), and at the 1-week and 3-week follow-ups, only the experimental group showed significant differences. No correlation between the IPAQ score and the degree of hamstring muscle flexibility was observed.

CONCLUSIONS

Hamstring muscle PNF stretching combined with electrical stimulation to trigger muscle contraction during the muscle contraction phase of the stretch achieves better flexibility results when compared to PNF alone.