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BackgroundThe architectural and morphological adaptations of the hamstrings in response to training with different exercises have not been explored.PurposeTo evaluate changes in biceps femoris long head (BFLH) fascicle length and hamstring muscle size following 10-weeks of Nordic hamstring exercise (NHE) or hip extension (HE) training.Methods30 recreationally active male athletes (age, 22.0±3.6 years; height, 180.4±7 cm; weight, 80.8±11.1 kg) were allocated to 1 of 3 groups: (1) HE training (n=10), NHE training (n=10), or no training (control, CON) (n=10). BFLH fascicle length was assessed before, during (Week 5) and after the intervention with a two-dimensional ultrasound. Hamstring muscle size was determined before and after training via MRI.ResultsCompared with baseline, BFLH fascicles were lengthened in the NHE and HE groups at mid-training (d=1.12–1.39, p<0.001) and post-training (d=1.77–2.17, p<0.001) and these changes did not differ significantly between exercises (d=0.49–0.80, p=0.279–0.976). BFLH volume increased more for the HE than the NHE (d=1.03, p=0.037) and CON (d=2.24, p<0.001) groups. Compared with the CON group, both exercises induced significant increases in semitendinosus volume (d=2.16–2.50, ≤0.002) and these increases were not significantly different (d=0.69, p=0.239).ConclusionNHE and HE training both stimulate significant increases in BFLH fascicle length; however, HE training may be more effective for promoting hypertrophy in the BFLH.

Purpose Comparing the MRI features of the grafts between a group of patients treated with an over-the-top anterior cruciate ligament reconstruction technique that preserves the hamstring attachment and a control group with a classical reconstruction technique. Methods Patients were assigned to a standard reconstruction technique or an Over-the-top plus lateral plasty technique. All patients underwent preoperative, 4-months and 18-months MRI; together with a clinical evaluation with KOOS and KT1000 laxity assessment. MRI study involved different parameters: the “Graft” was evaluated with the continuity, Howell Grading system, presence of liquid and signal noise quotient. The “Tibial Tunnel” was evaluated with the signal noise quotient, presence of edema or liquid and tunnel widening. All points assigned to each parameter formed a composite score ranging from 0–10. Tunnel and graft positioning were evaluated. Results At 18-month 20 MRIs (10 each group) were available, demographics were not significantly different between groups. The non-detached group showed significantly less liquid within the graft at 4-months ( p  = 0.008) and 18-months ( p  = 0.028), the tunnel was significantly smaller ( p  < 0.05) and less enlarged at both follow-ups ( p  < 0.05), signal noise quotient of the intra-tunnel graft was lower at 18-months ( p  < 0.05). The total score of the non-detached group saw a significant improvement at 4-months ( p  = 0.006) that remained stable at 18-months (n.s.). Conclusions Hamstring grafts, which tibial insertions were preserved, showed better MRI features at 4-and 18-months follow-up, especially in terms of liquid effusion, tunnel enlargement and signal noise quotient. Level of evidence IV.

The purpose of this study was to compare the effects of hamstring eccentric (NHE) strength training versus sprint training programmed as complements to regular soccer practice, on sprint performance and its mechanical underpinnings, as well as biceps femoris long head (BFlh) architecture. In this prospective interventional control study, sprint performance, sprint mechanics and BFlh architecture variables were compared before versus after six weeks of training during the first six preseason weeks, and between three different random match-pair groups of soccer players: \"Soccer group\" (n = 10), \"Nordic group\" (n = 12) and \"Sprint group\" (n = 10). For sprint performance and mechanics, small to large pre-post improvements were reported in \"Sprint group\" (except maximal running velocity), whereas only trivial to small negative changes were reported in \"Soccer group\" and \"Nordic group\". For BFlh architecture variables, \"Sprint\" group showed moderate increase in fascicle length compared to smaller augment for the \"Nordic\" group with trivial changes for \"Soccer group\". Only \"Nordic\" group presented small increases at pennation angle. The results suggest that sprint training was superior to NHE in order to increase BFlh fascicle length although only the sprint training was able to both provide a preventive stimulus (increase fascicle length) and at the same time improve both sprint performance and mechanics. Further studies with advanced imaging techniques are needed to confirm the validity of the findings.

ObjectiveThis study examines the correlation between MRI findings and difficult dissection during proximal primary hamstring repair and postoperative sciatica.Materials and methodsA total of 32 cases of surgically repaired hamstring tendon tears that underwent preoperative and postoperative MRI were divided into sciatica (n = 12) and control (n = 20) groups based on the presence or absence of postoperative sciatica. Cases were scored by two blinded musculoskeletal radiologists for imaging features associated with difficult surgical dissection and the development of subsequent sciatica. Intra- and interrater agreements, as well as correlation of MRI findings with symptoms (odds ratio, OR), were calculated.ResultsOn preoperative MRI, diffuse hamstring muscle edema pattern suggestive of active denervation (OR 9.4–13.6), and greater sciatic perineural scar circumference (OR 1.9–2) and length (OR 1.2–1.3) were significantly correlated with both difficult dissection and postoperative sciatica. Preoperatively, a greater number of tendons torn (OR 3.3), greater tear cross-sectional area (CSA, OR 1.03), and increased nerve T2-weighted signal (OR 3.2) and greater perineural scar thickness (OR 1.7) were also associated with difficult dissection, but not postoperative sciatica. On postoperative MRI, hamstring denervation, sciatic nerve tethering to the hamstring tendon, and development of perineural scar and greater perineural scar extent were all significantly correlated with postoperative sciatica.ConclusionPreoperative hamstring MRI demonstrates findings predictive of difficult sciatic nerve dissection; careful MRI evaluation of the nerve and for the presence and extent of perineural scar is important for preoperative planning. Preoperative and postoperative MRI both depict findings that correlate with postoperative sciatica.

To determine the effects of an eccentric hamstrings strength-training program, performed for at least 4 weeks by healthy adults, on muscle architecture and eccentric strength. A systematic search was performed up to October 2018 in the following electronic databases: PubMed, PEDro, CINAHL and SPORTDiscus. Combinations of the following search terms were used: , , , , , , , , , , and . Included articles were randomized controlled trials that allowed comparisons between isolated eccentric strength training of the biceps femoris muscle and other programs. Data from the included studies were extracted by 2 independent reviewers. These data included the study design, participant characteristics, inclusion and exclusion criteria of clinical studies, exercise and intervention characteristics, outcome measures, and the main results of the study. When meta-analysis was possible, we performed quantitative analysis. Ten randomized controlled trials were included. Limited to moderate evidence indicated that eccentric strength training was associated with an increase in fascicle length (mean difference [MD] = 1.97; 95% confidence interval [CI] = 1.48, 2.46), an increase in muscle thickness (MD = 0.10; 95% CI = 0.06, 0.13), and a decrease in pennation angle (MD = 2.36; 95% CI = 1.61, 3.11). Conflicted to moderate evidence indicated that eccentric hamstrings strength was increased after eccentric strength training compared with concentric strength training (standardized mean difference [SMD] = 1.06; 95% CI = 0.26, 1.86), usual level of activity (SMD = 2.72; 95% CI = 1.68, 3.77), and static stretching (SMD = 0.39; 95% CI = -0.97, 1.75). In healthy adults, an eccentric strength-training program produced architectural adaptations on the long head of the biceps femoris muscle and increased eccentric hamstrings strength.

Purpose The purpose of this study was to assess clinical and radiological outcome in patients after proximal hamstring tendon repair. We hypothesized that there is a significant correlation among subjective clinical outcome and interlimb asymmetries in muscle strength, fatty infiltration, and hamstring volume. Methods This retrospective monocentric case series included patients with surgical repair after proximal hamstring tendon rupture. Clinical outcome was assessed utilizing: Healthy Days Core Module (CDC HRQOL-4), numeric pain rating scale (NRS), modified Harris Hip Score (mHHS), Tegner Activity Scale (TAS), return to pre-injury activity level (RTPA), and patient satisfaction score. Postoperative hamstring strength was measured using a handheld dynamometer and radiological outcome was determined by postoperative magnetic resonance imaging (MRI). Results Twenty-seven patients with a mean age of 51.2 (± 12.6) years were available for follow-up at a mean of 41.11 (± 18.4) months. Patients state a mean of 10.6 (± 11.5) days in the unhealthy days (UHD) index and 88.9% show “good health” in the simple summary score (SSS). Mean subjective outcome scores were as follows: NRS 1.1 (± 2.4), mHHS 90.3 (± 14.8) and TAS 5.7 (± 2.2). A total of 59.3% RTPA and 88.9% state to be somewhat or very satisfied with their surgery. Mean interlimb strength ratio was 0.88 (± 0.21). MRI demonstrated a fully restored muscle–tendon unit, significantly greater fatty infiltration in the injured hamstrings ( p  = 0.009, d  = 0.558), and a mean interlimb hamstring volume ratio of 0.94 (± 0.11). With respect to the 10% benchmark, patients had no significant asymmetries in muscle strength ( p  = 0.677, d  = 0.084) or hamstring volume ( p  = 0.102, d  = − 0.34). Correlation analysis revealed moderate correlation among asymmetries in strength and volume ( p  = 0.073, r  = 0.373). In patients with the operated side inferior to the healthy side ( n  = 15), there was strong correlation among asymmetries in strength and volume ( p  = 0.002, r  = 0.725). Statistically significant correlation was found between interlimb muscle volume atrophy and increase in fatty infiltration ( p  = 0.015, r  = 0.481). Conclusion Proximal hamstring repair results in good clinical outcome with satisfactory recovery of hamstring strength and volume. Interlimb asymmetries, in terms of muscle strength, fatty infiltration, and hamstring volume do not correlate with clinical outcome. Study Type Retrospective cohort study; Level of evidence, 3.

Purpose Hamstring strain injury is a frequent and serious injury in competitive and recreational sports. While Nordic hamstring (NH) eccentric strength training is an effective hamstring injury-prevention method, the protective mechanism of this exercise is not understood. Strength training increases muscle strength, but also alters muscle architecture and stiffness; all three factors may be associated with reducing muscle injuries. The purpose of this study was to examine the effects of NH eccentric strength training on hamstring muscle architecture, stiffness, and strength. Methods Twenty healthy participants were randomly assigned to an eccentric training group or control group. Control participants performed static stretching, while experimental participants performed static stretching and NH training for 6 weeks. Pre- and post-intervention measurements included: hamstring muscle architecture and stiffness using ultrasound imaging and elastography, and maximal hamstring strength measured on a dynamometer. Results The experimental group, but not the control group, increased volume (131.5 vs. 145.2 cm 3 , p  < 0.001) and physiological cross-sectional area (16.1 vs. 18.1 cm 2 , p  = 0.032). There were no significant changes to muscle fascicle length, stiffness, or eccentric hamstring strength. Conclusions The NH intervention was an effective training method for muscle hypertrophy, but, contrary to common literature findings for other modes of eccentric training, did not increase fascicle length. The data suggest that the mechanism behind NH eccentric strength training mitigating hamstring injury risk could be increasing volume rather than increasing muscle length. Future research is, therefore, warranted to determine if muscle hypertrophy induced by NH training lowers future hamstring strain injury risk.

Background Ischial tuberosity apophyseal fractures are avulsion fractures of the anatomic footprint of the proximal hamstring tendons. Generally, these injuries are rare and frequently occur in skeletally immature, active patients due to incomplete ossification. Depending on the fragment displacement, non-operative or operative treatment approaches are used. Case presentation We report a case of a 29-year-old professional volleyball athlete who has suffered from a nonunion avulsion fracture for 14 years. Isolated suture anchor fixation was performed after open excision of a large bony fragment followed by excellent clinical and functional outcome at 1 year postoperatively. Conclusion In conclusion, avulsion fractures of the ischial tuberosity with large fragments and restrictions to activities of daily living due to pain can, in individualized cases, be treated with an open excision of the fragment followed by repair of the proximal hamstring tendons using suture anchors.

This study investigated the effect of five consecutive days of cold‐water immersion (CWI) on recovery from exercise‐induced muscle damage (EIMD) in the hamstrings following maximal eccentric contraction (EC) exercise. Eighteen healthy adult women were randomly assigned to a CWI group and a control group (CG) (n = 9/group). Participants performed 10 sets of 10 repetitions of isokinetic EC at 30°/second and underwent maximum voluntary isometric contraction (MVC), delayed onset muscle soreness (DOMS) assessment, straight leg raise (SLR) test, and plasma myoglobin (Mb) measurement. The CWI group received one 14‐min session of CWI treatment (14°C) at 1, 25, 49, 73, and 97 h after the EC test, whereas the CG rested in a seated position at the same five time points without receiving treatment. (1) All the dependent variables in the CWI group and CG exhibited significant changes after the EC test (p < 0.05). (2) The recovery effect in the CWI group was significantly greater than in the CG in terms of the MVC, DOMS, SLR, and plasma Mb concentration results. MVC increased by 89.3 ± 2.0% on the fourth day (p < 0.013), DOMS decreased by 15.4 ± 1.5 mm on the second day (p < 0.000), SLR increased by 86.3 ± 1.1% on the second day (p < 0.014), and plasma Mb decreased by 436.3 ± 60.8% on the third day (p < 0.014). The study indicates that five consecutive days of CWI at 14°C significantly enhance recovery from exercise‐induced muscle damage in the hamstrings. Highlights CWI treatment was beneficial for recovery from EIMD after high‐intensity exercise. All the participants exhibited similar and significant responses in their MVC, DOMS, SLR, and plasma Mb concentration results after the EC test. The CWI group demonstrated mostly superior recovery responses compared with the CG after receiving the CWI treatment on 5 consecutive days after the EC test.

Background Anterior cruciate ligament (ACL) reconstruction, using hamstring auto-graft is a common surgical procedure, which often leads to persistent hamstring muscle-strength deficiency and reduced function. The purpose of this randomized controlled trial (RCT) is to investigate the effect of a combined, progressive, strength and neuromuscular exercise intervention on knee muscle strength, functional capacity and hamstring muscle-tendon morphology in ACL-reconstructed patients with persistent hamstring muscle-strength deficiency compared with controls. Methods/design The study is designed as a multicenter, parallel-group RCT with balanced randomization (1:1) and blinded outcome assessments (level of evidence: II) and will be reported in accordance with the CONSORT Statement. Fifty ACL-reconstructed patients (hamstring auto-graft) with persistent limb-to-limb knee-flexor muscle-strength asymmetry at 12–24 months’ post surgery, will be recruited through outpatient clinics and advertisements. Patients will be randomized to a 12-week progressive, strength and neuromuscular exercise group (SNG) with supervised training twice weekly or a control intervention (CON) consisting of a home-based, low-intensity exercise program. Outcome measures include between-group change in maximal isometric knee-flexor strength (primary outcome) and knee-extensor muscle strength, hamstring-to-quadriceps strength ratios of the leg that has been operated on and Knee injury and Osteoarthritis Outcome Score (KOOS) (secondary outcomes). In addition, several explorative outcomes will be investigated: The International Knee Documentation Committee Subjective Knee Form (IKDC), the Tegner Activity Score, rate of force development (RFD) for the knee flexors and extensors, tendon regeneration and potential muscle hypertrophy at graft harvest site evaluated by magnetic resonance imaging (MRI), postural control, kinetic/kinematic gait characteristics and knee-related functional capacity. Discussion This RCT is designed to investigate the effect of combined, progressive-resistance and neuromuscular exercises on knee-flexor/extensor strength, in the late rehabilitation phase following ACL reconstruction. Reduced hamstring strength represents a potential risk factor for secondary ACL rupture and accelerated progression of osteoarthritis. If deemed effective, the intervention paradigm introduced in this study may help to improve current treatment strategies in ACL-reconstructed patients. Trial registration ClinicalTrials.gov, ID: NCT02939677 (recruiting). Registered on 20 October 2016.