Stress-strain relationship of individual hamstring muscles: A human cadaver study

The incidence of hamstring muscle strain varies among muscles, suggesting that the mechanical stresses associated with elongation may differ among muscles. However, the passive mechanical properties of whole human muscles have rarely been directly measured and clarified. This study aimed to clarify the stress-strain relationship of the hamstring muscles using a soft-embalmed Thiel cadaver. The long heads of the biceps femoris (BFlh), semimembranosus (SM), and semitendinosus (ST) muscles were dissected from eight cadavers. The proximal and distal hamstring tendons were affixed to the mechanical testing machine. Slack length was defined as the muscle length at the initial loading point detected upon the application of a tensile load. Muscle length was measured using a tape measure, and the anatomical cross-sectional area (ACSA) of the muscle was measured at the proximal and distal sites using B-mode ultrasonography. In the loading protocol, the muscle was elongated from its slack length to a maximum of 8% strain at an average rate of 0.83 L0/s, and the amount of displacement and tensile load were measured for each muscle. Further, the strain (%, displacement/slack muscle length) and stress (kPa, tensile load/ACSA) were calculated to evaluate the mechanical properties. Two-way repeated-measures analysis of variance (ANOVA) was used to compare stress changes with increasing muscle strain. A significant interaction between the muscle and strain factors was observed with respect to stress. Post-hoc tests revealed higher stresses in the BFlh and SM than in ST after 3% strain (P < 0.01). However, no significant differences were observed between the BFlh and SM groups. At 8% strain, the BFlh, SM, and ST exhibited stresses of 63.7 ± 12.1, 53.7 ± 23.2, and 21.0 ± 11.9 kPa, respectively. The results indicate that the stress changes associated with muscle strain differed among muscles. In particular, the stress applied to the three muscles at the same strain was found to be higher in the BFlh and SM. Thus, these findings suggest that increased mechanical stress during elongation may contribute to the frequent occurrence of muscle strain in BFlh and SM.

Acute fatigue-induced alterations in hamstring muscle properties after repeated Nordic hamstring exercises

This study aimed to investigate the impact of the Nordic hamstring exercises (NHE) on acute fatigue-induced alterations in the mechanical and morphological properties of hamstring muscles. The second aim was to define the blood flow and perfusion after NHE in recreational active volunteers. Twenty-two individuals volunteered to participate in the study. This study investigated fatigue outcomes: rate of perceived exertion (RPE) scale and average force generated during NHE; mechanical properties (stiffness); morphological properties (thickness, pennation angle, and fascicle length), and vascularity index (VI) of the semitendinosus (ST) and biceps femoris long head (BFLH) at baseline, immediately post-exercise and 1-h post-exercise. The NHE fatigue procedure consisted of six bouts of five repetitions. The results showed an increase in thickness and pennation angle of BFLH and ST immediately post-exercise and a decrease in thickness and pennation angle of BFLH and ST 1-h post-exercise. While the fascicle length of BFLH and ST decreased immediately post-exercise and increased 1-h post-exercise. The VI for two muscles increased immediately post-exercise and after 1-h post-exercise. Moreover, we found a relationship between RPE and average force, that is, as RPE increased during NHE, average force decreased. In conclusion, eccentric NHE exercises significantly and acutely affect BFLH and ST. The NHE fatigue protocol significantly affected the mechanical and morphological properties of BFLH and ST muscles, changing their thickness, fascicle length, pennation angle, and VI.

The need for speed - Does the force-velocity property significantly alter strain distributions within skeletal muscle?

Skeletal muscles are complex structures with nonlinear constitutive properties. This complexity often requires finite element (FE) modeling to better understand muscle behavior and response to activation, especially the fiber strain distributions that can be difficult to measure in vivo. However, many FE muscle models designed to study fiber strain do not include force-velocity behavior. To investigate force-velocity property impact on strain distributions within skeletal muscle, we modified a muscle constitutive model with active and passive force-length properties to include force-velocity properties. We implemented the new constitutive model as a plugin for the FE software FEBio and applied it to four geometries: 1) a single element, 2) a multiple-element model representing a single fiber, 3) a model of tapering fibers, and 4) a model representing the bicep femoris long head (BFLH) morphology. Maximum fiber velocity and boundary conditions of the finite element models were varied to test their influence on fiber strain distribution. We found that force-velocity properties in the constitutive model behaved as expected for the single element and multi-element conditions. In the tapered fiber models, fiber strain distributions were impacted by changes in maximum fiber velocity; the range of strains increased with maximum fiber velocity, which was most noted in isometric contraction simulations. In the BFLH model, maximum fiber velocity had minimal impact on strain distributions, even in the context of sprinting. Taken together, the combination of muscle model geometry, activation, and displacement parameters play a critical part in determining the magnitude of impact of force-velocity on strain distribution.

Assessing site-specificity of the biomechanical properties of hamstring aponeuroses using MyotonPRO: A cadaveric study

BACKGROUND

Hamstring muscles are the most frequently reported sites of muscle strain injuries, especially near the bi-articular muscles' myotendinous junction, where aponeurosis provides a connective tissue network linking muscle fibers to the tendon. This study aimed to investigate the reliability and site-specific differences of hamstring aponeuroses under different conditions (formalin and urea) using MyotonPRO.

METHODS

Eight hamstring muscle groups were dissected from four human cadavers (two males and two females) aged 83-93 years. Measurements of the mechanical properties of the aponeuroses from the superficial and deep regions of biceps femoris long head, semitendinosus, and semimembranosus (after formalin solution immersion) were done using MyotonPRO (intra-rater reliability was examined within a 24-h interval), following which the hamstring aponeuroses were measured using a similar procedure after urea solution immersion.

FINDINGS

Test-retest (intra-rater) results revealed that the MyotonPRO measurement of tone, stiffness, relaxation, and creep of cadaveric aponeuroses presented good to excellent reliability (ICC: 0.86 to 0.98). There were no significant differences in tone, stiffness, elasticity, relaxation, and creep among the six sites of hamstring aponeuroses under both formalin and urea conditions. Significant differences between formalin and urea conditions were found in the tone, stiffness, relaxation, and creep of hamstring aponeuroses (P < 0.05).

INTERPRETATION

These results suggested that the biomechanical properties of hamstring aponeuroses showed homogeneity between the sites using MyotonPRO. Urea solution could potentially neutralize the effect of formalin on the biomechanical properties of cadaveric muscle-aponeurosis-tendon units. The present findings might influence the design of subsequent cadaveric studies on hamstring muscle strains.

Medial Patellofemoral Complex Reconstruction (Combined Reconstruction of Medial Patellofemoral Ligament and Medial Quadriceps Tendon-Femoral Ligament) With Semitendinosus Autograft Resulted in Similar Clinical and Radiographic Outcomes to Medial Patellofemoral Ligament Reconstruction in Treating Recurrent Patellar Dislocation

PURPOSE

To compare clinical and radiographic outcomes of medial patellofemoral ligament reconstruction (MPFL-R) and medial patellofemoral complex reconstruction (MPFC-R) for recurrent patellar dislocation. Outcome measures were compared based on the Insall-Salvati index.

METHODS

Patients who were diagnosed with recurrent patellar dislocation and underwent either MPFL-R or MPFC-R (combined reconstruction of MPFL and medial quadriceps tendon-femoral ligament) were retrospectively analyzed. Group allocation was based on surgical procedure and patient characteristics were collected. Clinical assessments included patient-reported outcome measures (PROMs) and return-to-sports rates. Minimal clinically important difference analysis was performed. A subgroup analysis of PROMs was carried out between patients with an Insall-Salvati index ≤1.2 versus >1.2. The patellar tilt angle, lateral patellar displacement, and bisect offset ratio were measured pre- and postsurgery. Functional failures and complications were assessed.

RESULTS

Overall, 70 patients (72 knees) in the MPFL-R group and 58 patients (61 knees) in the MPFC-R group were included. Patient characteristics were comparable between the groups. At a minimum follow-up of 24 (mean, 50.6 ± 22.1) months, all PROMs were substantially improved (P < .001), without significant intergroup differences. The percentages of patients reaching the minimal clinically important difference were similar after MPFL-R and MPFC-R: 98.6% versus 93.4% (International Knee Documentation Committee), 97.2% versus 98.4% (Lysholm), 98.6% versus 100% (Kujala), and 77.8% versus 72.1% (Tegner). The subgroup analysis based on patellar height and the return-to-sport rates also suggested comparable results. Radiographic evaluation demonstrated significantly smaller lateral patellar displacements (P = .004) and bisect offset ratios (P < .001) but similar patellar tilt angles after MPFC-R. Four (5.6%) patients receiving MPFL-R and 2 (3.3%) patients receiving MPFC-R reported recurrence of functional instability, without statistically significant difference.

CONCLUSIONS

MPFC-R resulted in similar overall clinical and radiographic outcomes to MPFL-R in treating recurrent patellar dislocation. MPFC-R might not provide additional benefits for patients with an Insall-Salvati index >1.2.

LEVEL OF EVIDENCE

Level IV, therapeutic, retrospective cohort study.

Bilateral Corticomotor Reorganization and Symptom Development in Response to Acute Unilateral Hamstring Pain: A Randomized, Controlled Study

Accumulating evidence demonstrates that pain induces adaptations in the corticomotor representations of affected muscles. However, previous work has primarily investigated the upper limb, with few studies examining corticomotor reorganization in response to lower limb pain. This is important to consider, given the significant functional, anatomical, and neurophysiological differences between upper and lower limb musculature. Previous work has also focused on unilateral corticomotor changes in response to muscle pain, despite an abundance of literature demonstrating that unilateral pain conditions are commonly associated with bilateral motor dysfunction. For the first time, this study investigated the effect of unilateral acute hamstring pain on bilateral corticomotor organization using transcranial magnetic stimulation (TMS) mapping. Corticomotor outcomes (TMS maps), pain, mechanical sensitivity (pressure pain thresholds), and function (maximal voluntary contractions) were recorded from 28 healthy participants at baseline. An injection of pain-inducing hypertonic (n = 14) or pain-free isotonic (n = 14) saline was then administered to the right hamstring muscle, and pain ratings were collected every 30 seconds until pain resolution. Follow-up measures were taken immediately following pain resolution and at 25, 50, and 75 minutes post-pain resolution. Unilateral acute hamstring pain induced bilateral symptom development and changes in corticomotor reorganization. Two patterns of reorganization were observed-corticomotor facilitation and corticomotor depression. Corticomotor facilitation was associated with increased mechanical sensitivity and decreased function bilaterally (all P < .05). These effects persisted for at least 75 minutes after pain resolution. PERSPECTIVE: These findings suggest that individual patterns of corticomotor reorganization may contribute to ongoing functional deficits of either limb following acute unilateral lower limb pain. Further research is required to assess these adaptations and the possible long-term implications for rehabilitation and reinjury risk in cohorts with acute hamstring injury.

Functional reconstruction of chronic acromioclavicular joint separation using a double suture technique combined with semitendinosus autograft

PURPOSE

We present the functional and clinical results of a combined surgical technique that functionally restores chronic Acromioclavicular Joint Instability (AJI). The method combines a double-looped suture fixation augmented with a semitendinosus autograft.

METHODS

Between 2017 and 2021, 15 patients were treated using the surgical technique. All patients suffered an Acromioclavicular Joint Separation that remained untreated for at least 6 (6-16) weeks after the initial injury. Four Ethibond sutures were passed below the coracoid process and through a 4.5 drill hole in the clavicle. The sutures provided adequate horizontal and vertical reduction and stabilization of the clavicle. A semitendinosus autograft was passed below the coracoid process and looped around the clavicle. The remaining graft limbs were used to reconstruct the acromioclavicular capsule. Patients were radiologically evaluated with bilateral anteroposterior (AP), Zanca, and Alexander views. The clinical evaluation was based on the Acromioclavicular Joint Instability Score and the Constant-Murley Score.

RESULTS

The mean follow-up period was 31.2 months (17-61). The mean last ACJIS and CMS scores were 96 (90-100) and 97.67 (87-100), respectively. Reduction of the clavicle was radiologically confirmed in all cases throughout the follow-up period. AC arthritis was reported in 1 case without associated clinical symptoms. No significant complications were reported, and all patients returned to the pre-injury activity level.

CONCLUSION

The presented functional reconstruction of the AC joint disruption in chronic cases is an effective and secure method with low complication rates and good clinical results.

LEVEL OF EVIDENCE III

This journal requires that authors assign a level of evidence to each article. For a full description of these Evidence-Based Medicine ratings, please refer to the Table of Contents or the online Instructions to Authors www.springer.com/00266 .

Changes in hamstring contractile properties during the competitive season in young football players

Background

The study aimed to examine alterations and imbalances in hamstring muscle contractile properties among young football players throughout their competitive season, and to understand how these changes might contribute to the risk of muscle injuries. Hamstring injuries are particularly common in football, yet the underlying causes and effective prevention methods remain unclear.

Methods

The research involved 74 young footballers who were assessed before the season (pre-test) and after 12 weeks of training (post-test). To evaluate changes in hamstring muscle contractile properties, specifically the left and right biceps femoris (BF) and semitendinosus (ST), tensiomyography (TMG) parameters were utilized.

Results

In comparison to the BF muscle, significant differences in time delay (Td) between the left and right sides in the post-test (p = 0.0193), and maximal displacement (Dm) between the left and right sides at the pre-test (p = 0.0395). However, significant differences in Dm were observed only in the left ST muscle between the pre- and post-tests (p = 0.0081). Regarding lateral symmetry, BF registered measurements of 79.7 ± 13.43 (pre-test) and 77.4 ± 14.82 (post-test), whereas ST showed measurements of 87.0 ± 9.79 (pre-test) and 87.5 ± 9.60 (post-test).

Conclusions

These assessments provided TMG reference data for hamstring muscles in young footballers, both before the season and after 12 weeks of in-season training. The observed changes in the contractile properties and decrease in lateral symmetry of the BF in both tests suggest an increased risk of injury.

The Influence of a Multistage Mountain-Bike Race on Neuromuscular Activation and Synergies: A Case Study

INTRODUCTION

This case study aimed to describe potential changes in neuromuscular activation and synergies after an 8-day cross-country mountain-bike stage race.

METHODS

A peak power output test was performed 5 days before the race. Two days before the start and after 7 days of racing, the athlete performed a power-based Lamberts Submaximal Cycling Test, including surface electromyography, and completed a Daily Analysis of Life Demands of Athletes questionnaire. Neuromuscular activation, in terms of root mean square, timing (onset-offset) of muscle activation, and synergies, was obtained from electromyography recordings.

RESULTS

The athlete reported an increase in symptoms of experienced stress after the stage race on the Daily Analysis of Life Demands of Athletes questionnaire. Both biceps femoris and tibialis anterior muscles showed a reduction in normalized amplitude after the stage race. In addition, the number of synergies that was necessary to describe neuromuscular activation increased from 2 to 3.

CONCLUSIONS

In this case study, the increase in synergies suggests that, after the stage race, the athlete showed a more complex muscle-recruitment pattern. This may indicate that muscle coordination can change when muscle fatigue occurs; however, further research is needed to confirm these results in a larger sample.

Acute effects of static and proprioceptive neuromuscular facilitation stretching on hamstrings muscle stiffness and range of motion: a randomized cross-over study

This study aimed to compare the acute effects of static stretching (SS) and proprioceptive neuromuscular facilitation (PNF) stretching on hamstrings flexibility and shear modulus. Sixteen recreationally active young volunteers participated in a randomized cross-over study. Participants underwent an aerobic warm-up (WU), followed by either SS or PNF stretching. Range of motion (RoM) during passive straight leg raise and active knee extension, as well as shear modulus of the biceps femoris (BF) and semitendinosus (ST) muscles, were measured at baseline, post-WU, and post-stretching. Both stretching techniques significantly increased RoM, with no differences observed between SS and PNF (p < 0.001; η2 = 0.59-0.68). However, only PNF stretching resulted in a significant decrease in BF shear modulus (time×stretching type interaction: p = 0.045; η2 = 0.19), indicating reduced muscle stiffness. No changes in ST shear modulus were observed after either stretching technique. There was no significant correlation between changes in RoM and shear modulus, suggesting that the increase in RoM was predominantly due to changes in stretch tolerance rather than mechanical properties of the muscles. These findings suggest that both SS and PNF stretching can effectively improve hamstring flexibility, but PNF stretching may additionally reduce BF muscle stiffness. The study highlights the importance of considering individual muscle-specific responses to stretching techniques and provides insights into the mechanisms underpinning acute increases in RoM.

The ability of a portable near infrared instrument to evaluate the shelf-life of fresh and thawed goat muscles

The objective of this study was to evaluate the use of a portable near infrared (NIR) instrument to monitor the shelf-life of four goat muscles [longissimus thoracis et lumborum (LTL), semimembranosus (SM), semitendinosus (ST) and biceps femoris (BF)] stored for up to 8 days (4 °C). The NIR spectra of the muscle samples were collected at day 0, and after 1, 4 and 8 days of storage using a MicroNIR instrument (900-1600 nm). The coefficient of determination in cross-validation (R2) and the standard error in cross validation (SECV) obtained for the prediction of days of storage ranged between 0.76 and 0.86, where the SECV ranged from 0.32 to 0.41. The best statistics in cross-validation were obtained for the prediction of days of storage in the BF samples, followed by the ST and LTL muscles. Differences in the PLS loadings for the cross-validation models were observed due to the interactions between the different muscle samples and days of storage. Overall, these results showed the potential of NIR spectroscopy to identify the time of storage in four different goat muscles. Similar data and techniques could be used to predict the remaining shelf life of meat derived from different species under storage. This information can then be used as a tool to predict and guarantee the safety of meat samples to the consumer along the meat supply and value chains.

The Effect of Active Release Technique on Hamstring Extensibility: A Critically Appraised Topic

CLINICAL SCENARIO

Hamstring extensibility plays a significant role in maintaining postural alignment essential for a functional musculoskeletal system. When hamstring extensibility is lacking, individuals are placed at a higher risk for developing various lumbar spine, pelvis, knee, and foot dysfunctions. Limited hamstring extensibility is common, occurring in as much as 40% of college students and 86% of the adult population. Therefore, it is essential to maintain hamstring extensibility, which can be aided by understanding intervention effectiveness for improving flexibility.

PURPOSE

To critically appraise the literature on the effectiveness of Active Release Technique (ART) for the treatment of hamstring extensibility deficits.

CLINICAL QUESTION

What is the effect of ART in a healthy population with or without hamstring extensibility deficits?

SUMMARY OF KEY FINDINGS

Three studies were included for critical appraisal. Two studies concluded a single treatment session of ART that individuals possessing limited straight leg raise range of motion experienced improved active knee extension, popliteal angle, and sit-and-reach test measures. In the third study, a single session of ART was effective at improving hamstring extensibility in males without hamstring extensibility dysfunction.

CLINICAL BOTTOM LINE

Based on the current level 1 and level 3 evidence, ART may be an effective treatment to produce acute increases in hamstring extensibility. Future research is still needed.

STRENGTH OF RECOMMENDATION

Level B evidence exists to support the use of ART to improve hamstring extensibility in the healthy population.

Hamstring and knee injuries are associated with isometric hip and trunk muscle strength in elite Australian Rules and Rugby League players

OBJECTIVES

This study investigated relationships between isometric trunk and hip extensor strength, lumbar muscle morphology, and the risk of hamstring and knee ligament injuries in Australian Football League and National Rugby League players.

DESIGN

Prospective cohort study.

METHODS

Trunk and hip extensor strength, multifidus and quadratus lumborum cross-sectional area were measured during the 2020 pre-season. Logistic regressions and decision trees were employed to explore associations between maximum strength, strength endurance, multifidus and quadratus lumborum cross-sectional area, age, previous injuries, and hamstring and knee ligament injury risk.

RESULTS

Greater strength endurance [odds ratio = 0.42 (0.23-0.74), p = 0.004] and maximum strength [odds ratio = 0.55 (0.31-0.94), p = 0.039] reduced hamstring injury risk. Increased risk of knee ligament injuries was associated with larger multifidus [odds ratio = 1.66 (1.14-2.45), p = 0.008] and higher multifidus to quadratus lumborum ratio (odds ratio = 1.57 (1.13-2.23), p = 0.008]. Decision tree models indicated that low strength endurance (< 99 Nm) characterised hamstring strains, while high (≥ 1.33) multifidus to quadratus lumborum ratio mitigated risk. Knee ligament injuries were associated with larger (≥ 8.49 cm2) multifidus, greater (≥ 1.25) multifidus to quadratus lumborum ratio, and lower maximum strength (< 9.24 N/kg).

CONCLUSIONS

Players with lower trunk and hip extensor maximum strength and strength endurance had increased risk of hamstring injuries, while knee ligament injury risk was elevated with larger multifidus cross-sectional area, higher multifidus to quadratus lumborum ratio, and lower maximum trunk and hip extensor strength.

Characterizing focal muscle signal on MRI in flexor-pronator muscles' status post ulnar collateral ligament reconstruction

OBJECTIVE

Focal high signal is commonly seen about the flexor pronator mass on MRI in some patients after ulnar collateral ligament (UCL) reconstruction of the elbow. The etiology of this high signal is unclear and not described in literature. The hypothesis is that the edema we see on post-operative MRI is related to palmaris longus graft harvest rather than secondary to other causes of muscle edema such as denervation or muscle strain.

METHODS AND MATERIALS

An IRB waiver-approved, retrospective search of our radiology database was conducted using the keywords "ucl," "elbow," and "reconstruction" between 1/01/2012 and 1/01/2022, with search parameters set as MRI for exam type. The images were reviewed to evaluate for high signal at the flexor pronator mass by a junior and a senior musculoskeletal radiologist. The surgical notes were then reviewed in electronic medical record system to see which graft was used for the UCL reconstruction.

RESULTS

The cohort comprised of 33 patients (1 female/32males, 14-51 years old) who had undergone UCL reconstructions. Four patients were excluded from the study secondary to the surgical note not specifying which graft was used. The surgical and imaging dates were also recorded with the largest time gap of 7 years between the surgery and imaging. Seventeen of the 29 patients had palmaris longus harvested from the ipsilateral arm, 1 patient had palmaris longus harvested from the contralateral arm, 2 patients had an internal brace, and 9 patients had a hamstring graft. Seventeen out of 17 (100%) patients with ipsilateral palmaris longus graft demonstrated focal edema at the flexor pronator mass while 0/12 of the patients without the palmaris longus graft showed the focal edema seen by its counterparts.

CONCLUSION

High signal which is commonly seen at the flexor pronator mass in patient status most UCL reconstruction of the elbow is secondary to the palmaris longus harvest rather than other etiologies such as muscle strain, retear, or trauma.

Muscle synergies inherent in simulated hypogravity running reveal flexible but not unconstrained locomotor control

With human space exploration back in the spotlight, recent studies have investigated the neuromuscular adjustments to simulated hypogravity running. They have examined the activity of individual muscles, whereas the central nervous system may rather activate groups of functionally related muscles, known as muscle synergies. To understand how locomotor control adjusts to simulated hypogravity, we examined the temporal (motor primitives) and spatial (motor modules) components of muscle synergies in participants running sequentially at 100%, 60%, and 100% body weight on a treadmill. Our results highlighted the paradoxical nature of simulated hypogravity running: The reduced mechanical constraints allowed for a more flexible locomotor control, which correlated with the degree of spatiotemporal adjustments. Yet, the increased temporal (shortened stance phase) and sensory (deteriorated proprioceptive feedback) constraints required wider motor primitives and a higher contribution of the hamstring muscles during the stance phase. These results are a first step towards improving astronaut training protocols.

A transcriptomic analysis of skeletal muscle tissues reveals promising candidate genes and pathways accountable for different daily weight gain in Hanwoo cattle

Cattle traits like average daily weight gain (ADG) greatly impact profitability. Selecting based on ADG considering genetic variability can lead to economic and genetic advancements in cattle breeding. This study aimed to unravel genetic influences on ADG variation in Hanwoo cattle at the skeletal muscle transcriptomic level. RNA sequencing was conducted on longissimus dorsi (LD), semimembranosus (SB), and psoas major (PM) muscles of 14 steers assigned to same feed, grouped by low (≤ 0.71 kg) and high (≥ 0.77 kg) ADG. At P ≤ 0.05 and log2fold > 1.5, the distinct pattern of gene expression was identified with 184, 172, and 210 differentially expressed genes in LD, SB, and PM muscles, respectively. Tissue-specific responses to ADG variation were evident, with myogenesis and differentiation associated JAK-STAT signaling pathway and prolactin signaling pathways enriched in LD and SB muscles, while adipogenesis-related PPAR signaling pathways were enriched in PM muscle. Key hub genes (AXIN2, CDKN1A, MYC, PTGS2, FZD5, SPP1) were upregulated and functionally significant in muscle growth and differentiation. Notably, DPP6, CDKN1A, and FZD5 emerged as possible candidate genes linked to ADG variation. These findings enhance our understanding of genetic factors behind ADG variation in Hanwoo cattle, illuminating skeletal muscle mechanisms influencing ADG.

Tactile stimulation restores inhibited stretch reflex attributable to attenuation of Ia afferents during surprise landing

Arthrogenic muscle inhibition (AMI) is induced by pathological knee conditions. The present study aimed to investigate the effect of tactile stimulation on reflex changes induced by simulated AMI during unpredictable landing performances. Twenty participants performed six unilateral landing tasks: 15 cm normal landing (15NL), 30 cm normal landing (30NL), surprise landing (SL), 30 cm normal landing following vibration (30NLV), SL following vibration (SLV), and SL following vibration with Kinesiology tape (SLK). For SL, the solid landing platform (15 cm) was removed and replaced by a false floor. Since the false floor dislodged easily under load, participants unpredictably fell through the platform to the actual landing surface 15 cm below. After completing 15NL, 30NL, and SL, vibration was applied to participants' knees to induce neurological changes similar to AMI. After vibration, participants performed 30NLV, SLV, and SLK in a random order. EMG signals in the post-landing short latency (31-60 ms) and medium latency (61-90 ms) periods were examined. EMG signals from the vastus lateralis (VL), vastus medialis (VM), and biceps femoris (BF) were recorded and compared between tasks. EMG signals of all muscles in SL were significantly enhanced in the medium latency period as compared with 30NL. Enhanced EMG signals in SL were suppressed by vibration stimulation in the VL, but the suppressed EMG signals were restored after cutaneous stimulation with Kinesiology tape (p < 0.01). Our findings suggest that AMI could alter motor control patterns during unpredictable landing and that tactile stimulation could restore the altered motor control to a normal state.

Six Weeks of Unilateral Flywheel Hip-Extension and Leg-Curl Training Improves Flywheel Eccentric Peak Power but Does Not Enhance Hamstring Isokinetic or Isometric Strength

PURPOSE

This preregistered trial investigated how 6 weeks of unilateral flywheel leg-curl and hip-extension training impact isokinetic, isometric, and flywheel strength and power outcomes.

METHODS

The study involved 11 male university athletes (age 22 [2] y; body mass 77.2 [11.3] kg; height 1.74 [0.09] m) with one leg randomly allocated to flywheel training and one leg to control. Unilateral eccentric and isometric knee-flexion torque and flywheel unilateral leg-curl and hip-extension peak power were tested. Training intensity and volume (3-4 sets of 6 + 2 repetitions) were progressively increased.

RESULTS

The intervention enhanced hip-extension concentric (P < .01, d = 1.76, large) and eccentric (P < .01, d = 1.33, large) peak power more than the control (significant interaction effect). Similarly, eccentric (P = .023, d = 1.05, moderate) peak power was enhanced for the leg curl. No statistically significant differences between conditions were found for isokinetic eccentric (P = .086, d = 0.77, moderate) and isometric (P = .431, d = 0.36, small) knee-flexor strength or leg-curl concentric peak power (P = .339, d = 0.52, small). Statistical parametric mapping analysis of torque-angle curves also revealed no significant (P > .05) time-limb interaction effect at any joint angle.

CONCLUSION

Unilateral flywheel hamstring training improved knee-flexor eccentric peak power during unilateral flywheel exercise but not flywheel concentric, isokinetic eccentric, or isometric (long-lever) knee-flexor strength.

Posterior chain and core training improves pelvic posture, hamstrings-to-quadriceps ratio, and vertical jump performance

BACKGROUND

Poor pelvic posture demonstrated through anterior pelvic tilt (APT) have been known to produce musculoskeletal imbalances involving weakness of the abdominal and pelvic musculature. While stretching and massage techniques have been reported to be effective in alleviating APT, it remains unclear if similar improvements can be elicited by posterior chain and core strength training. Therefore, the aim of this study was to examine the effect of an 8-week posterior and core strengthening program on APT, hamstrings-to-quadriceps (H:Q) strength ratio, and vertical jump performance in healthy individuals.

METHODS

Ten healthy males (age = 26±12 years; mass = 87±14 kg; height = 1.8±0.1 m) and nine healthy females (age = 22±4 years; mass = 70±14 kg; heigh t = 1.7±0.1 m) performed resistance training (2×/week; 40-45 mins) involving a combination of hip extensors and abdominal strengthening exercises for 8 weeks. APT (°), vertical jump power (W), vertical jump height (m), and H:Q ratio at 60, 180, and 300°/s were assessed prior to and following the resistance training program.

RESULTS

APT, vertical jump power, vertical jump height, and H:Q ratio at 60 and 180°/s, were significantly improved following 8 weeks of resistance training (all Ps<0.05).

CONCLUSIONS

Our main finding was that 8 weeks of resistance training emphasizing posterior chain and core strengthening was effective in reducing APT, improving vertical jump performance and H:Q ratio in healthy individuals. Our findings have potential implications for clinicians prescribing resistance training exercises to improve pelvic posture in healthy asymptomatic individuals at risk of developing chronic low back pain and lumbar-spinal pathologies due to excessive anterior pelvic tilt.

Effect of PNF stretching performed in the AKE position on hip, knee, and ankle flexibility

BACKGROUND

To measure hamstring flexibility, the active knee extension (AKE) test is preferred over the straight leg raise (SLR) test as it can be used to measure hamstring flexibility more selectively. However, hamstring stretching is primarily conducted in the SLR position (maximal hip flexion in the supine position) as it allows for maximal hip flexion in the supine position.

OBJECTIVE

This study evaluates the effects of proprioceptive neuromuscular facilitation (PNF) stretching in the AKE position (maximal knee extension with 90∘ flexion of the hip in the supine position) on hip, knee, and ankle flexibility.

METHODS

SLR, AKE, and active dorsiflexion (ADF) tests were used to determine the range of motion (ROM) before (pre-ROM) and after (post-ROM) stretching. PNF stretching consisted of maximal isometric knee flexion at the end range with external resistance to prevent knee flexion. One set of PNF stretches (five trials of six seconds each) was conducted.

RESULTS

The post-ROMs of hip, knee, and ankle measured via the SLR, AKE, and ADF tests, respectively, were significantly higher than the pre-ROMs.

CONCLUSIONS

The improvement in knee flexibility was greater than the improvement in hip and ankle flexibility. The AKE position is recommended in clinical settings during PNF stretching for individuals with hamstring tightness. Furthermore, PNF stretching in the AKE position increases the ADF ROM.

Combined effect of myofascial release and passive stretching on plantar pressure in individual with hamstring tightness- an experimental study

INTRODUCTION

The lower kinetic chain is known to be affected by hamstring tightness which causes biomechanical alterations. As per the literature, short hamstring might cause prolonged forefoot loading, which can cause higher repeated stress on the plantar fascia. There is evidence supporting the use of various stretching and myofascial release techniques for hamstring tightness, further research is needed to investigate their impact on plantar pressure. Hence the study aims to determine combined effect of myofascial release and passive stretching on plantar pressure in individual with hamstring tightness.

METHODS

This was an experimental pre-post study design with 67 randomised screenings from asymptomatic health care science students aged 18 to 25. From this scientific survey, a sample size of 47 students having HMS tightness based on the popliteal angle were recruited using a universal goniometer. An intervention was proposed that included MFR and passive stretching in 3 sessions on alternate days. Plantar pressure of these individuals was noted by using the "Harris and Beath foot printing mat" before and after the intervention.

RESULT

Significant pressure changes were observed after intervention: great toe of right side (p = 0.001), toes 2 to 5 of right side (p = 0.010) and left side (p = 0.008), first metatarsal of left side (p = 0.010), lateral forefoot of right side (p = 0.019) and left (p = 0.018), medial heel (p = 0.044), and lateral heel of right side (p = 0.025). These values substantiate the enhancement in plantar pressure.

CONCLUSION

The combined effect of Myofascial release and passive stretching in an individual with hamstring tightness resulted in a significant increase in popliteal angle and plantar pressure.

Genetic lines influenced the texture, collagen and intramuscular fat of pork longissimus and semimembranosus

The effects of genetic lines (PM-LR - Pure maternal, Landrace-type; PM-LW - Pure maternal, Large White-type; PM-D - Pure maternal, Duroc-type; SynT-LWLR - Synthetic terminal, Large white and Landrace-type; PT-D - Pure terminal, Duroc-type; and PT-LW - Pure terminal, Large White-type) on carcass traits and pork quality, including cooking loss, Warner-Bratzler shear force (WBSF), texture profile analysis (TPA), collagen content and solubility and intramuscular fat (IMF) content of Longissimus thoracis et lumborum (LTL) and Semimembranosus (SM), were investigated. The results showed that all terminal lines had lower backfat thickness than maternal lines, but muscles from line SynT-LWLR had the highest hardness and cohesiveness and the lowest IMF content. The SM showed higher hardness, adhesiveness, springiness, chewiness, collagen, and IMF content but lower WBSF and collagen solubility than LTL. Collagen and IMF content affected WBSF and TPA parameters across both muscles and in LTL alone. Significant relationships between collagen content and texture parameters were found in line PT-D. Genetic lines and muscles affect the contribution of collagen and IMF to pork texture.

Editorial Commentary: Proper Anterior Cruciate Ligament Graft Choice Mitigates Against the Need for Anterolateral Ligament Reconstruction

It is not coincidence that fervor surrounding anterolateral ligament (ALL) reconstruction increased as double-bundle anterior cruciate ligament reconstruction (ACLR) enthusiasm cooled. But perhaps we shifted our focus too soon, or perhaps we shifted our focus too much. But we must remember that the ACL is primary. Increases in ACL graft diameter by 1 or 2 mm can significantly increase graft strength and decrease revision rate. Biomechanical and clinical evidence suggests that quadriceps tendon ACLR and patellar tendon ACLR demonstrates less pivot shift phenomena than hamstring ACLR. In addition, As biologically active suture tapes become more mainstream, augmented allografts are an increasingly attractive option. Proper ACL graft choice mitigates against the need for ALL reconstruction. Risk factors for anterolateral rotatory instability may include low body mass index and lateral meniscal pathology, in addition to the well-known risks such as age, gender, activity level, and revision cases. Perhaps lateral extra-articular tenodesis should be reserved for high-risk cases.

New insights into the function of lipid droplet-related proteins and lipid metabolism of salt-stimulated porcine biceps femoris: label-free quantitative phosphoproteomics, morphometry and bioinformatics

BACKGROUND

Lipid droplets (LDs) are important multifunctional organelles responsible for lipid metabolism of postmortem muscle. However, the dynamics in their building blocks (cores and layers) and phosphorylation of lipid droplet-related proteins (LDRPs) regulating meat lipolysis remain unknown at salt-stimulated conditions.

RESULTS

LDRPs extracted from cured porcine biceps femoris (1% and 3% salt) were subjected to label-free quantitative phosphoproteomic analysis and LDs morphological validation. Results indicated that 3% salt curing significantly decreased triglyceride (TG) content with increase in glycerol and decrease in LDs fluorescence compared to 1% salt curing. Comparative phosphoproteomics showed that there were significant changes in phosphorylation at 386 sites on 174 LDRPs between assayed groups (P < 0.05). These differential proteins were mainly involved in lipid and carbohydrate metabolism. Curing of 3% salt induced more site-specific phosphorylation of perilipin 1 (PLIN1, at Ser81) and adipose triglyceride lipase (ATGL, at Ser399) than 1%, whereas the phosphorylation (at Ser600) of hormone-sensitive lipase (HSL) was up-regulated. Ultrastructure imaging showed that LDs were mostly associated with mitochondria, and the average diameter of LDs decreased from 2.34 μm (1% salt) to 1.73 μm (3% salt).

CONCLUSION

Phosphoproteomics unraveled salt-stimulated LDRPs phosphorylation of cured porcine meat provoked intensified lipolysis. Curing of 3% salt allowed an enhanced lipolysis than 1% by up-regulating the phosphorylation sites of LDRPs and recruited lipases. The visible splitting of LDs, together with sarcoplasmic disorganization, supported the lipolysis robustness following 3% salt curing. The finding provides optimization ideas for high-quality production of cured meat products. © 2023 Society of Chemical Industry.

Discrete Hamstring: Quadriceps Strength Ratios Do Not Represent Angle-Specific Ratios in Premier League Soccer Players

ABSTRACT

Lunn, DE, Nicholson, G, Cooke, M, Crespo, R, Robinson, T, Price, RJ, and Walker, J. Discrete hamstring: quadriceps strength ratios do not represent angle-specific ratios in Premier League soccer players. J Strength Cond Res 37(12): 2417-2422, 2023-This study compared angle-specific hamstring:quadriceps (H:Q) ratios with their discrete counterparts during strength testing in professional male soccer players. Twenty-seven professional English Premier League soccer players were recruited for this study (age: 22 ± 4 years; stature: 1.81 ± 0.08 m; body mass: 74.7 ± 6.5 kg). Isokinetic testing of the knee flexors and extensors was conducted concentrically at two angular velocities (60° and 240°·s -1 ) and eccentrically (for the knee flexors only) at 30°·s -1 . Conventional H:Q ratio was calculated as the ratio between peak joint moment in the flexors and extensors at 60°·s -1 . Functional H:Q ratio was calculated as the peak joint moment in the flexors during the eccentric condition and the extensors at 240°·s -1 . Discrete conventional and functional H:Q ratios were 0.56 ± 0.06 and 1.28 ± 0.22, respectively. The residual differences between discrete values and angle-specific residual values were 13.60 ± 6.56% when normalized to the magnitude of the discrete value. For the functional ratios, the normalized residual was 21.72 ± 5.61%. Therefore, neither discrete ratio was representative of angle-specific ratios, although the conventional ratio had lower error overall. Therefore, practitioners should consider H:Q ratio throughout the full isokinetic range of motion, not just the discrete ratio calculated from peak joint moments, when designing and implementing training programs or monitoring injury risk, recovery from injury, and readiness to return to play.

Biomechanical Comparison of Proximal Hamstring Reconstruction Using Distal Hamstring Graft Versus Fascia Lata Graft for Treatment of Chronic Hamstring Injury

BACKGROUND

Surgical reconstruction using autografts is often required in treating chronic proximal hamstring injuries where the hamstring has retracted >5 cm. There is a paucity of evidence that evaluates reconstructive procedures using the 2 most popular autografts, distal hamstring and fascia lata.

PURPOSE

To (1) compare failure load and elongation at failure between the proximal hamstring tendon reconstruction with distal hamstring and fascia lata grafts and (2) compare the stiffness between these reconstructions and the native state.

STUDY DESIGN

Controlled laboratory study.

METHODS

Seven pairs of human cadaveric hemipelvises (mean age, 60.4 ± 5.0 years; 6 male, 1 female) with no evidence of previous injury or abnormality were dissected to the proximal hamstring origin. Through use of a dynamic tensile testing system, each specimen underwent preconditioning followed by a distraction test to determine the native specimen stiffness. Each pair of specimens was assigned to undergo proximal hamstring reconstruction with distal hamstring and reconstruction with fascia lata. Each specimen then underwent preconditioning followed by pull to failure. The failure load, elongation at failure, mode of failure, and stiffness were determined for each repair.

RESULTS

The distal hamstring group exhibited a greater failure load (mean, 334 ± 108 N; P = .031) and higher stiffness (mean, 47.6 ± 16.0 N/mm; P = .009) compared with the fascia lata group (mean, 179 ± 78 N and 23.0 ± 11.2 N/mm, respectively). Although the stiffness of the repair state in the distal hamstring group (mean, 61.4 ± 13.4 N/mm) was not significantly different from that of the native state (mean, 47.6 ± 16.0 N/mm), the stiffness of the repair state in the fascia lata group (mean, 23.0 ± 11.2 N/mm) was significantly lower than that of the native state (mean, 60.1 ± 17.7 N/mm) (P < .0001). The elongation at failure of the distal hamstring graft group (mean, 33.0 ± 6.6 mm) was not significantly different from that of the fascia lata graft group (mean, 29.2 ± 14.9 mm) (P = .58). The most common modes of failure for the distal hamstring group (29% each) were at the repair site, at the graft-muscle interface, and at the muscle, while the most common modes of failure for the fascia lata graft were at the tendon-graft interface.

CONCLUSION

The distal hamstring group achieved higher failure load and stiffness than the fascia lata group, and stiffness of the distal hamstring group was not significantly different from that of the native tendon. Elongation at failure was not different between repair techniques. Although distal hamstring graft failure predominantly occurred in 3 distinct locations, failure of the fascia lata repair occurred predominantly at the tendon-graft interface. These cadaveric results suggest that it may be more clinically appropriate to use distal hamstring versus fascia lata for proximal hamstring reconstruction.

CLINICAL RELEVANCE

Our time-zero study suggests that the proximal hamstring reconstruction with distal hamstring could be the preferred surgical treatment for chronic hamstring injury over reconstruction with fascia lata. The failure load of reconstruction with distal hamstring was inferior to that of primary suture anchor, suggesting that rehabilitation after reconstruction should not be more aggressive than the standard postoperative rehabilitation protocol for acute repair.

Functional popliteal angle tests improve identification of short hamstring muscle-tendon length in patients with a central neurological lesion

This study introduces a functional exercise protocol to improve the identification for short hamstring muscle-tendon length (HMTL), a common contributor to crouch gait in patients with central neurological lesions (CNL). The functional exercise protocol incorporates a knee extension movement with hip in a flexed position, while standing on one leg (functional popliteal angle test) and walking with large steps to the current standard protocol (walking at comfortable speed and as fast as possible). The main aim was to establish whether the new protocol allows better determination of maximum HMTLs and diagnostics of short HMTL in patients with a CNL. Lower limb 3D marker position data from 39 patient limbs and 10 healthy limbs performing the exercises were processed in OpenSim to extract HMTLs. The new protocol provoked significantly larger HMTLs compared to the current standard protocol. The total number of limbs classified as having too short HMTLs reduced from 16 to 4 out of a total of 30 limbs walking in crouch. The new protocol improves determination of maximum HMTL, thereby improving short HMTL diagnostics and identification of patients in need of lengthening treatment. Inter-individual variability observed among patients, indicating the need to include all exercises for comprehensive diagnosis.

The effects of knee ligament load using simulated hip abductor and hamstring muscle strengthening during cutting maneuver

BACKGROUND

This study aimed to analyze knee ligament of load and joint moment to simulate the strengthening of the hip abductor and hamstring muscles using musculoskeletal modeling, thereby contributing to decrease of knee ligament load.

METHODS

Forty participants (age: 21.85 ± 1.90 years; height: 1.76 ± 0.06 m; body mass: 68.5 ± 7.06 kg) were instructed to run at 4.5 ± 0.2 m/s from a 5 m distance posterior to the force plate, land their feet on the force plate, and perform the cutting maneuver on the left. In the musculoskeletal modeling, the hip abductor and hamstring muscles were targeted to construct a model with a 30% increase in the contraction force of the hip abductor, hamstring, and both 2 muscles. The variables were the ligament force and knee joint moment. One-way repeated measure ANOVA and Bonferroni test were used to compare the abductor/hamstring, abductor, hamstring and control models.

RESULTS

There were significant differences in anterior bundle of the anterior cruciate ligament (ACL) (P = .001), inferior bundle of the superficial layer of the medial collateral ligament (MCL) (P = .016), and posterior bundle of the superficial layer of the MCL (P = .022) force. The post hoc showed that the hamstring model had lower anterior bundle of the ACL and inferior bundle of the superficial layer of the MCL than the abductor/hamstring and abductor models (P < .05) and lower posterior bundle of the superficial layer of the MCL than the abductor and control models (P < .05). There was a significant difference in the adduction (P = .028) and internal rotation moments (P = .014). The post hoc showed that both moments were lower in the hamstring model than in the other models (P < .05).

CONCLUSIONS

The hamstring strengthening may contribute significantly to preventing ACL or MCL injury by reducing knee ligament load.

Alternate Graft Options for Staged Flexor Tendon Reconstruction: A Cadaveric Study of Hamstring Autografts Compared to Conventional Autografts

PURPOSE

To compare the semitendinosus and gracilis tendon lengths and diameters to the palmaris longus, plantaris, flexor digitorum profundus, and flexor pollicis longus (FPL) tendons in a cadaveric model to evaluate the feasibility of hamstring autograft use for staged flexor tendon reconstruction.

METHODS

Fifteen fresh cadavers were evaluated for surgical incisions about the knee, forearm, and hand. All flexor digitorum profundus (FDP), FPL, palmaris longus, plantaris, semitendinosus, and gracilis tendons were harvested from each specimen. Diameter and length were recorded and means with SDs were calculated. The mean diameters of the gracilis and semitendinosus were compared to the mean diameters of the FDP and FPL tendons. The hamstring tendon lengths were then compared in terms of percentage of the palmaris longus and plantaris tendon lengths.

RESULTS

The gracilis (18.0 cm) and semitendinosus (19.9 cm) means were notably longer than the palmaris longus (16.0 cm) and shorter than the plantaris (30.0 cm). The average gracilis tendon diameter (3.8 mm) was smaller than the flexor tendon diameters except for the little finger FDP (3.8 mm). The semitendinosus tendon diameter (4.8 mm) was larger than all flexor tendons with the exception of the middle finger FDP (4.6 mm). Average gracilis and semitendinosus tendon diameters were 3.7 mm and 4.5 mm in males, and 3.8 mm and 4.8 mm in females.

CONCLUSIONS

This study showed the gracilis tendon to have adequate length and diameter for potential autograft use in staged flexor tendon reconstruction in all digits but the little finger. The semitendinosus is larger in diameter than the native flexor tendons, making it a poor autograft option in cases with an intact pulley system.

CLINICAL RELEVANCE

Common tendon autograft options for flexor tendon reconstruction are variably present, and the use of gracilis and semitendinosus autograft present potential graft options.

Effects of muscle fatigue on exercise-induced hamstring muscle damage: a three-armed randomized controlled trial

PURPOSE

Hamstring injuries in soccer reportedly increase towards the end of the matches' halves as well as with increased match frequency in combination with short rest periods, possibly due to acute or residual fatigue. Therefore, this study aimed to investigate the effects of acute and residual muscle fatigue on exercise-induced hamstring muscle damage.

METHODS

A three-armed randomized-controlled trial, including 24 resistance-trained males, was performed allocating subjects to either a training group with acute muscle fatigue + eccentric exercise (AF/ECC); residual muscle fatigue + eccentric exercise (RF/ECC) or a control group with only eccentric exercise (ECC). Muscle stiffness, thickness, contractility, peak torque, range of motion, pain perception, and creatine kinase were assessed as muscle damage markers pre, post, 1 h post, and on the consecutive three days.

RESULTS

Significant group × time interactions were revealed for muscle thickness (p = 0.02) and muscle contractility parameters radial displacement (Dm) and contraction velocity (Vc) (both p = 0.01), with larger changes in the ECC group (partial η2 = 0.4). Peak torque dropped by an average of 22% in all groups; stiffness only changed in the RF/ECC group (p = 0.04). Muscle work during the damage protocol was lower for AF/ECC than for ECC and RF/ECC (p = 0.005).

CONCLUSION

Hamstring muscle damage was comparable between the three groups. However, the AF/ECC group resulted in the same amount of muscle damage while accumulating significantly less muscle work during the protocol of the damage exercise.

TRIAL REGISTRATION

This study was preregistered in the international trial registration platform (WHO; registration number: DRKS00025243).

Low-load strength resistance training with blood flow restriction compared with high-load strength resistance training on performance of professional soccer players: a randomized controlled trial

BACKGROUND

The aim of this study is to evaluate the effectiveness of low-load blood flow restriction strength resistance training (LL-BFR) compared to high load strength resistance training (HL) on performance of professional soccer players.

METHODS

Eighteen male players from National Soccer Professional League were randomly allocated into two groups: LL-BFR, who performed a 6-weeks strength training program with low load (20-35% of one-repetition maximum-[1RM]), or HL, who performed a 6-week resistance training program with high load (70-85% 1RM). Before and after, thigh girth, vertical jump, lower limb strength, vertical force-velocity profile (F-v), and 30-m sprint were evaluated.

RESULTS

After the training program, both LL-BFR and HL induced significant increases compared to baseline in thigh girth (+3.3% for LL-BFR and +3.1% for HL) and maximal velocity during sprinting (+6.0 and +6.2%, respectively), without between-group differences. In reference to FV, only HL players improved imbalance (-54.4%), maximal theoretical force production (+10.4%) and decreased extension velocity (-20.5%) compared to baseline, without between-group differences. Only LL-BFR induced increases in maximum voluntary contraction of left hamstring compared to baseline (+13.8%), without between-group differences. No differences were shown for the rest of variables (P>0.05).

CONCLUSIONS

Although LL-BFR may increase muscle circumference and sprint ability, these results are similar to those induced with HL in male professional soccer. In terms of F-v, only HL induced improvements, but these changes were not greater than those observed after LL-BFR.

Anthropometry in predicting Semitendinosus and Gracilis graft diameter for arthroscopic ACL reconstruction among the Bengali population

Semitendinosus and Gracilis autografts are commonly used for anterior cruciate ligament (ACL) reconstruction. However, its main drawback is individual variation in the tendon diameter. This study aimed to evaluate the usefulness of the anthropometric measurements for the prediction of Semitendinosus and Gracilis combined (quadrupled) strands graft diameter in arthroscopic ACL reconstruction among the Bengali population. Sixty consecutive patients who underwent ACL reconstruction between July 2019 to June 2020 were observed in this cross-sectional study. In all cases, the doubled (2 strands) Gracilis and Semitendinosus tendons were combined to get the final quadrupled (combined 4 strands) graft for use. Anthropometries such as body mass index (BMI), body weight, and height were recorded preoperatively and quadrupled combined tendon diameter was measured at the operating theater. The relationship between these parameters was statistically determined using the Pearson correlation coefficient, and scatter diagrams were plotted. Among the study subjects, most (54) were male, and the mean age of all subjects was 24 ± 6.92 years. The average graft diameter was 7.20 ± 0.76 mm. Correlations between the mean graft diameter with BMI (r = 0.018, and P = .891), body height (r = 0.011 and P = .933), and weight (r = 0.028 and P = .832) were not significant. Scatter diagrams also showed that the variables were not correlated. Anthropometries like BMI, body weight, or body height cannot be used in predicting Semitendinosus and Gracilis tendon graft diameter for arthroscopic ACL reconstruction among the Bengali population.

Effect of sex (ram or wether) and short duration, high volt electrical stimulation on tenderisation of Longissimus thoracis et lumborum and Semimembranosus muscles derived from Boer Goat and large frame Indigenous Veld Goat

This study determined whether castration and electrical stimulation (ES) influenced chevon tenderness and related physiological characteristics in Boer Goat (BG; n = 36; 21 bucks and 15 wethers) and large frame Indigenous Veld Goat (IVG; n = 41; 21 bucks and 20 wethers). Half of buck and wether carcasses were ES (20s, 400 Volts peak, 5 ms pulses at 15 pulses/s) 10 min post-mortem. Dressed carcasses were chilled (4 °C within 1-h post-mortem). pH and temperature decline, % drip loss, sarcomere length (SL), myofibril fragmentation length (MFL; 1- and 4-days post-mortem), Calpain-1, -2 and calpastatin activities (1- and 24-h), Warner-Bratzler shear force (WBSF; 1-day post-mortem) and sensory attributes (tenderness and juiciness; 4-days post-mortem) were measured on Longissimus thoracis et lumborum (LTL) and Semimembranosus (SM) muscles. ES carcasses had significantly lower pH irrespective of sex or breed. Buck LTL and SM were less tender (P ≤ 0.05) supported by longer MFL and higher calpastatin activity (P < 0.05), than wether muscles. ES LTL were more tender (WBSF and sensory) (P ≤ 0.001) while ES SM were less affected (P = 0.055). ES caused lower Calpain-1 activity in the LTL. SL do not support cold shortening and calpastatin played a major role in the tenderisation of chevon early post-mortem. A longer ageing period is recommended for goat meat in general to achieve acceptable levels of tenderness.

Preserving the hamstring tendon insertion during ACL reconstruction with an autograft: Systematic literature review

INTRODUCTION

The hamstring tendons (gracilis and semitendinosus) are often used as an autograft for anterior cruciate ligament (ACL) reconstruction. Healing of this graft involves a slow biological process called ligamentization. To encourage this process, some authors have proposed preserving the insertion of the hamstring tendons.

HYPOTHESIS

Leaving the tibial insertion of the hamstring tendons intact will provide better early biological incorporation and superior tibial mechanical fixation resulting in various clinical advantages.

MATERIALS AND METHODS

In January 2022, a systematic literature review was carried out independently by two authors of the Medline, PubMed and Embase databases. The keywords used were "pedicular" or "pedicled" or "preservation of tibial attachment" or "hamstring tibial insertion" AND "ACL reconstruction". Each author's data was analyzed separately.

RESULTS

Sixteen articles were analyzed. Preserving the hamstring tibial insertion during ACL reconstruction improves the graft's biological incorporation during the initial postoperative phase according to clinical studies with MRI analysis and provides a mechanical advantage at the graft's tibial attachment according to biomechanical studies (construct up to 65% stiffer). There was no difference in the clinical and functional scores when compared to the conventional technique in which the hamstring tendons are detached from their tibial insertion.

DISCUSSION

The main conclusion of this systematic literature review was that preserving the hamstring tibial insertion during ACL reconstruction appears to improve the graft's ligamentization with biological and mechanical advantages relative to detaching the hamstring tendons. The clinical and functional results were comparable to other techniques. Prospective studies with large cohorts are still needed to confirm these findings.

LEVEL OF EVIDENCE

IV; Systematic review of literature.

Size Comparison of the Cadaveric Anterior Cruciate Ligament Midsubstance Cross-Sectional Area and the Cross-Sectional Area of Semitendinosus Double-Bundle Anterior Cruciate Ligament Reconstruction Autografts in Surgery

The purpose of this study was to compare the cadaveric midsubstance cross-sectional anterior cruciate ligament (ACL) area and the cross-sectional semitendinosus (ST) double-bundle ACL autograft area in surgery. Thirty-nine nonpaired formalin-fixed cadaveric knees and 39 subjects undergoing ST double-bundle ACL reconstruction were included in this study. After soft tissue resection, cadaveric knees were flexed at 90 degrees, and the tangential line of the femoral posterior condyles was marked and sliced on the ACL midsubstance. The cross-sectional ACL area was measured using Image J software. In the patients undergoing ACL surgery, the harvested ST was cut and divided into anteromedial (AM) bundle and posterolateral (PL) bundle. Each graft edge diameter was measured by a sizing tube, and the cross-sectional graft area was calculated: (AM diameter/2)2 × 3.14 + (PL diameter/2)2 × 3.14. Statistical analysis was performed for the comparison of the cross-sectional area between the cadaveric ACL midsubstance and the ST double-bundle ACL autografts. The cadaveric midsubstance cross-sectional ACL area was 49.0 ± 16.3 mm2. The cross-sectional ST double-bundle autografts area was 52.8 ± 7.6 mm2. The ST double-bundle autograft area showed no significant difference when compared with the midsubstance cross-sectional ACL area. ST double-bundle autografts were shown to be capable of reproducing the midsubstance cross-sectional ACL area.

Effects of Low-Intensity Torque-Matched Isometric Training at Long and Short Muscle Lengths of the Hamstrings on Muscle Strength and Hypertrophy: A Randomized Controlled Study

ABSTRACT

Nakao, S, Ikezoe, T, Taniguchi, M, Motomura, Y, Hirono, T, Nojiri, S, Hayashi, R, Tanaka, H, and Ichihashi, N. Effects of low-intensity torque-matched isometric training at long and short muscle lengths of the hamstrings on muscle strength and hypertrophy: A randomized controlled study. J Strength Cond Res 37(10): 1978-1984, 2023-This study investigated the effects of low-intensity torque-matched isometric training on muscle hypertrophy and strengthening at long (LL) and short muscle lengths (SL). Twenty-eight young subjects completed an 8-week hamstring isometric training program (30% of maximal voluntary contraction (MVC) × 5 s × 20 repetitions × 5 sets × 3 times/week) at 30° knee flexion (LL) or 90° knee flexion (SL). The cross-sectional area (CSA) of the hamstrings and MVC were measured before and after the intervention. The active torque because of muscle contraction was calculated by subtracting the passive torque at rest from the total torque (30% MVC). The active torque was significantly lower in the LL training group than in the SL training group (p < 0.01), whereas there was no between-group difference in total torque during training. For CSA and MVC at 30° knee flexion, the split-plot analysis of variance (ANOVA) showed no significant time × group interaction; however, it did show a significant main effect of time (p < 0.05), indicating a significant increase after training intervention. As for MVC at 90° knee flexion, there was a significant time × group interaction (p < 0.05) and a significant simple main effect of time in both the LL (p < 0.01; Cohen's d effect size [ES] = 0.36) and SL (p < 0.01; ES = 0.64) training groups. Therefore, low-intensity isometric training at LL can induce hypertrophy and strengthening, even in cases where the active torque production is lower than that at SL, whereas the training at SL may be more effective for muscle strengthening at SL.

Evaluation of semitendinosus muscle transposition for treatment of perineal hernias in 33 small-breed dogs

Little is known about the perioperative complications and treatment outcomes of repairing perineal hernias using semitendinosus muscle transposition (SMT) in small-breed dogs. The objective of this study was to retrospectively evaluate the complications and prognosis of perineal hernia repair using SMT in 33 small, male dogs (weighing < 15 kg). Before the study began, the medical records of all small-breed dogs that underwent SMT from March 2013 to June 2022 at the Veterinary Medical Center, University of Tokyo were analyzed, and telephone interviews were conducted with their owners or referring physicians. Short-term complications were observed in 42.4% of the patients. Lameness was the most common complication, although all cases were resolved within a few days. The recurrence rate during the study period (median: 265 d) was 9.1%. The results of this study showed that transposition of the semitendinosus muscle is more invasive than other surgical procedures for perineal hernias. It is, however, an effective alternative when repair with internal obturator muscle transposition alone is expected to be difficult, such as severe atrophy of the internal obturator muscle or herniation in the ventral direction, and in cases with a history of surgery by transposition of the internal obturator muscle.

Release-reinsertion of the biceps femoris tendon onto the fibula in biceps femoris impingement on the knee with or without snap

Ectopic insertions of the biceps femoris tendon at the knee can cause impingement with the fibular head, leading to pain with or without snap. There are several variant insertions that have recently been described and classified. Pain syndrome primarily affects athletic patients, often cyclists, disrupting sports practice. Diagnosis is difficult and often late. Medical treatment is often disappointing, leading to surgery. The aim of surgery is to remove the impingement between the ectopic insertion of the biceps tendon and the fibular head, by releasing the unduly anterior tendon, sometimes from the tibia and reinserting it in an anteroposterior tunnel in the fibular head. This reinsertion in a physiological zone without impingement is then fixed by an interference screw.

Regional differences in behaviors of fascicle and tendinous tissue of the biceps femoris long head during hamstring exercises

The biceps femoris long head (BFLH) gains its properties from internal elements (fascicles and tendinous tissues) which behaviors remain poorly understood across BFLH regions and dynamic tasks. The aim of this study was to assess the in vivo behaviors of fascicles and tendinous tissue in the proximal and distal regions of BFLH during different dynamic knee and hip tasks. Twenty males performed the Nordic hamstring exercise (NHE) (n = 9) and Romanian deadlift (RDL) (n = 11). Activation of the BFLH was assessed using surface electromyography signals. Ultrasound images of BFLH and kinematic data were used to estimate the interaction between fascicle and tendinous tissue. The fascicles changed less in length (p < 0.05) and contributed less to BFLH length change (p < 0.05) in NHE with higher activation (p < 0.05) relative to RDL. The higher pennation angle changes of BFLH were found in distal region compared to proximal region in both tasks (p < 0.05), while the activation of distal region was higher than activation of proximal region in NHE (p < 0.05). The BFLH length change was primarily contributed by the tendinous tissue during dynamic resistance tasks, and was contributed less by fascicles which operated more isometrically in knee-dominant NHE with higher activation relative to hip-dominant RDL. Regional differences in pennation angle change and activation during dynamic tasks suggest potential regional differences in the mechanical function of BFLH, warranting further investigation.

Comparing right and left hamstring flexibility and its association to nonspecific lowr back pain among women of different age groups

BACKGROUND AND OBJECTIVES

Decreased hamstring flexibility has been associated with LBP (lower back pain). Increased tightness or shortening of hamstring muscle may cause pelvis imbalance or tilt and create instability and increase LBP risk. This study was conducted to pinpoint the differences between right and left hamstring length and their association to LBP in Israeli adult and elderly women.

METHODS

N = 109 women which were divided into two groups: Adult group, 41 women (aged 45-60) and older group, 68 women (aged 60-75), with LBP that exercise regularly (minimum twice weekly) were selected based on inclusion criteria. Hamstring flexibility was measured using the Passive Straight Leg Raise test and Sit and Reach test, and LBP was measured using the Oswestry Disability Index (OS), the Roland-Morris questionnaire (RM), and a personal information questionnaire.

FINDINGS

Findings indicate a statistically significant difference (p < .05) in hamstring flexibility between right and left legs in PSLR test, with the left being shorter than the right. A significant negative correlation was found between hamstring shortening to function in OS and RM questionnaires in the older group, no significant correlation was found between left -right hamstring flexibility differences and reduced function with LBP in the OS and RM questionnaires.

CONCLUSION

s: Hamstring shortening in adult and elderly women exists despite regular exercise. Future studies must be incorporated to improve hamstring flexibility with emphasis on balance of left and right legs to examine how this will affect LPB reports and compare women who exercise versus women who do not.

Effects of whole-body vibration training in static and dynamic semi-squat patterns on the lower limb muscle activity

The decline in physical function and the deterioration of the neuromusculoskeletal system in older people can easily lead to reduced muscle strength and slower mobility in the joints of the lower limbs, increasing the incidence of chronic diseases such as muscle wasting disorders, osteoporosis, debilitation and fall and fracture. It may also affect the quality of life and functional independence of older people, and in serious cases, even directly threaten their health. This study was conducted to determine the differences in lower limb muscle activation characteristics between static semi-squat (SSS) and dynamic semi-squat (DSS) training in middle-aged and old women at different frequencies and amplitudes and to explore a personalized whole-body vibration (WBV) training instruction program suitable for them. Fifteen healthy middle-aged and old women (60.8 ± 4.18 years old) were recruited for SSS and DSS WBV training. Their muscle activity of the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and gastrocnemius (GS) were calculated using the BTS FreeEMG300 wireless surface electromyography (EMG), which participants were completed that the two different contraction patterns of squats on WBV training. The knee flexion was maintained at 45° while the subjects were performing the SSS training, while during the DSS training, the knee flexion fluctuates between 10° and 45°. The SSS exercise requires the subject to remain stationary in the squatting position and the DSS to be performed at a rhythm of 4 s/repetition, with 2 s of squatting, 1 s of standing up, and 1 s intervals. The vibration frequencies and amplitudes were changed to the WBV training intensity, and the vibration frequencies were set to 0 Hz, 30 Hz and 40 Hz, and the amplitudes were set to 0 mm, 2 mm and 4 mm. Each subject is randomised to participate in WBV training with 5 combinations of frequency and amplitude in both static and dynamic semi-squat patterns. These were 0 Hz 0 mm, 30 Hz 2 mm, 30 Hz 4 mm, 40 Hz 2 mm, 40 Hz 4 mm for the static and dynamic demi-squat patterns of WBV training. A two-way repeated measures ANOVA was applied to compare the changes in surface EMG of the lower limb muscles in different modes of SSS and DSS with WBV training. (1) Our results showed significantly interaction effects in the frequency × amplitude of root mean square (EMGrms) in GS (P < 0.05), while no significant differences were observed in the interaction effects of SSS/DSS patterns, frequencies and amplitude of RF, VM, VL and BF (P > 0.05). (2) Comparisons between groups showed that the EMGrms of the RF were significantly higher for the DSS than the SSS (P < 0.05). Additionally, the EMGrms of VL and BF at 30 Hz and 40 Hz were greater than 0 Hz (P < 0.05). Also, The EMGrms at 4 mm for the VM, VL and BF were significantly higher than 0 mm, the EMGrms at 4 mm for the VM and VL were significantly higher than 2 mm (P < 0.05), and the EMGrms at 2 mm of VL and BF were significantly higher than 0 mm (P < 0.05). (3) The results showed that WBV stimulation significantly increased the EMGrms of the GS in the SSS compared with the vibration free semi-squat alone (P < 0.05). However, there were no significant differences between WBV training protocols for SSS patterns with different frequencies and amplitudes (frequencies and amplitudes not were 0 Hz and 0 mm) (P > 0.05). Comparison of EMGrms for WBV training of the GS in DSS patterns showed that 40 Hz/4 mm was significantly higher than 0 Hz/0 mm (P < 0.05), but there was no significant difference between the remaining vibration conditions (P > 0.05). WBV training for DSS can significantly improve the activation of the RF compared to SSS pattern. Compared with no vibration, WBV could significantly improv the activity of the lower limb muscles. Additionally, an increase in amplitude from 2 to 4 mm could significantly improve VM and VL activation, while no significant improvement on lower limb muscle activation was observed for increasing vibration frequency from 30 to 40 Hz.

Estimating Quadriceps and Hamstrings Strength Through Myoton Among Recreational Athletes

CONTEXT

The assessment of strength is one of the most usual practices among professionals involved in health care or sport. Quadriceps and hamstrings are the most commonly assessed muscle groups. Generally, the methods used to assess muscle strength are active and, therefore, alternative passive methods could be useful. Myoton provides measures on 3 mechanical properties of the muscle: tone, elasticity, and stiffness.

OBJECTIVE

This study aimed to analyze the association of Myoton, an easy-to-use tool not requiring voluntary stimulus from the subject, with strength values in quadriceps and hamstrings.

STUDY DESIGN

Experimental.

SETTING

University kinesiology laboratory.

PARTICIPANTS

Thirty-eight recreational athletes were evaluated.

MAIN OUTCOME MEASURES

Anthropometric and demographic data, Myoton-based measures of vastus lateralis, rectus femoris, vastus medialis, biceps femoris, and semitendinosus, and the maximum voluntary isometric contraction of quadriceps and hamstrings.

PROCEDURES

The association was examined using multiple regression models to estimate strength through Myoton-based parameters and different patient characteristics. The models encompassed either 2 or 3 independent variables.

RESULTS

The adjusted R2 values for predicting quadriceps strength were .666 for rectus femoris, .726 for vastus lateralis, and .667 for vastus medialis, while in regard to hamstrings, they were .617 for biceps femoris and .604 for semitendinosus.

CONCLUSIONS

The main finding was that acceptable relationships were found between muscle strength and Myoton-based parameters when variables such as gender and/or age are considered. Our study reveals a new tool for estimating strength with outstanding advantages: it is easy, time-efficient, adaptable, and highly manageable through the feasible equations provided.

Is peak hamstrings muscle-tendon length criterion a sufficient indicator to recommend against surgical lengthening of hamstrings?

BACKGROUND

Excessive knee flexion during stance in children with cerebral palsy is often treated by surgical hamstrings lengthening. Pre-operative hamstrings muscle-tendon length can be estimated from kinematics and often used for decision making to rule out surgical lengthening if peak hamstrings muscle-tendon length is 'Not Short'.

RESEARCH QUESTION

If peak hamstrings muscle-tendon length is within two standard deviations of typical, is that a sufficient indicator to rule out surgical hamstrings lengthening?

METHODS

Three motion analysis centers retrospectively identified children with cerebral palsy, age 6-17 years, who had consecutive gait analyses with knee flexion at initial contact > 20° and popliteal angle > 35° at initial study. Three groups were considered: Medial Hamstrings Lengthening (MHL), Medial and Lateral Hamstrings Lengthening (MLHL), no surgical intervention (Control). Peak hamstrings muscle-tendon length at initial gait study was computed and categorized as 'Short' or 'Not Short'. Two outcomes variables were considered: change in peak knee extension (PKE) and change in pelvic tilt. Univariate comparisons of all variables were assessed along with a multivariate stepwise regression analysis to identify pre-operative characteristics that may predict post-operative improvement.

RESULTS

440 individuals met inclusion criteria. Percentage of individuals with improved PKE by grouping were- MHL-'Short': 60%, MHL-'Not Short': 65%, MLHL-'Short': 74%, MLHL-'Not Short': 74%, Control 'Short': 20%, Control 'Not Short': 19%. Percentage of individuals with worsened pelvic tilt were- MHL-'Short': 25%, MHL-'Not Short': 11%, MLHL-'Short': 42%, MLHL-'Not Short': 21% with significantly more individuals in MHL-'Short' subgroup compared to MHL-'Not Short'. Multivariate analysis suggested that pre-operative pelvic tilt and weak hip extensor strength have the largest effect on predicting post-operative increase in APT. Peak muscle-tendon length was not a significant predictor of post-operative knee kinematics or increase in APT.

SIGNIFICANCE

This study suggests that hamstrings muscle-tendon length criteria by itself is not a sufficient indicator to recommend against hamstrings lengthening.

Acute and Long-Term Effects of Static Stretching on Muscle-Tendon Unit Stiffness: A Systematic Review and Meta-Analysis

Static stretching can increase the range of motion of a joint. Muscle-tendon unit stiffness (MTS) is potentially one of the main factors that influences the change in the range of motion after static stretching. However, to date, the effects of acute and long-term static stretching on MTS are not well understood. The purpose of this meta-analysis was to investigate the effects of acute and long-term static stretching training on MTS, in young healthy participants. PubMed, Web of Science, and EBSCO published before January 6, 2023, were searched and finally, 17 papers were included in the meta-analysis. Main meta-analysis was performed with a random-effect model and subgroup analyses, which included comparisons of sex (male vs. mixed sex and female) and muscle (hamstrings vs. plantar flexors) were also performed. Furthermore, a meta-regression was conducted to examine the effect of total stretching duration on MTS. For acute static stretching, the result of the meta-analysis showed a moderate decrease in MTS (effect size = -0.772, Z = -2.374, 95% confidence interval = -1.409 - -0.325, p = 0.018, I2 = 79.098). For long-term static stretching, there is no significant change in MTS (effect size = -0.608, Z = -1.761, 95% CI = -1.284 - 0.069, p = 0.078, I2 = 83.061). Subgroup analyses revealed no significant differences between sex (long-term, p = 0.209) or muscle (acute, p =0.295; long-term, p = 0.427). Moreover, there was a significant relationship between total stretching duration and MTS in acute static stretching (p = 0.011, R2 = 0.28), but not in long-term stretching (p = 0.085, R2 < 0.01). Whilst MTS decreased after acute static stretching, only a tendency of a decrease was seen after long-term stretching.

Comparison of Muscle Activity and Muscle Thickness According to Knee Flexion Angle during Supine Bridge Exercises using the Abdominal Drawing-in Maneuver on an Unstable Surface

This study evaluated changes in deep trunk muscle thickness and lower extremity muscle activities during bridge exercises with the abdominal drawing-in maneuver. Bridge exercises were conducted on an unstable surface at different knee flexion angles (60º, 90º and 120º), with the aim of identifying more effective angles for bridge exercises. This study included 21 healthy adults, aged 20-27 years. Biceps femoris (BF), rectus abdominis, and rectus femoris activity was measured using surface electromyography. The thicknesses of the transverse abdominis (TrA), external oblique (EO) and internal oblique (IO) muscles were measured. BF (p = 0.000, partial η2 = 0.670) activity increased considerably as the knee flexion angle decreased. TrA (p = 0.000, partial η2 = 0.883) and IO (p = 0.000, partial η2 = 0.892) thickness significantly increased, while EO (p = 0.000, partial η2 = 0.893) thickness decreased as the knee flexion angle decreased. When performing bridge exercises using the abdominal drawing-in maneuver on an unstable surface, the knee flexion angles should be at 120º and 60º to increase trunk stability and lower extremity muscle activity, respectively.

Lower Body Joint Moments during the Golf Swing in Older Adults: Comparison to Other Activities of Daily Living

Golf participation has increased dramatically in the last several years. With this increase in participation, clinicians need better evidenced based strategies to advise those golfers with different pathologies when it is safe to return to the game. Golf teaching professionals also need to understand how to alter golf mechanics to protect injured and/or diseased joints in golfers to allow them to play pain free and avoid further injury. This study used a 3-dimensional link segment model to calculate the net joint moments on the large lower limb joints (knee and hip) during golf (lead and trail leg) and two commonly studied activities of daily living (gait and sit-to-stand) in 22 males, healthy, adult golfers. It also examined the correlations between these knee and hip joint loads and club head speed. The external valgus knee moment and the internal hip adduction moment were greater in the lead leg in golf than in the other activities and were also correlated with club head speed. This indicates a strategy of using the frontal plane GRF moment during the swing. The internal hip extension and knee flexion moment were also greater in the golf swing as compared with the other activities and the hip extension moment was also correlated with club head speed. This emphasizes the importance of hip extensor (i.e., gluteus maximus and hamstring) muscle function in golfers, especially in those emphasizing the use of anterior-posterior ground reaction forces (i.e., the pivoting moment). The golf swing places some loads on the knee and the hip that are much different than the loads during gait and sit-to-stand tasks. Knowledge of these golf swing loads can help both the clinician and golf professional provide better evidence-based advice to golfers in order to keep them healthy and avoid future pain/injury.

Predicting Injury and Illness with Machine Learning in Elite Youth Soccer: A Comprehensive Monitoring Approach over 3 Months

The search for monitoring tools that provide early indication of injury and illness could contribute to better player protection. The aim of the present study was to i) determine the feasibility of and adherence to our monitoring approach, and ii) identify variables associated with up-coming illness and injury. We incorporated a comprehensive set of monitoring tools consisting of external load and physical fitness data, questionnaires, blood, neuromuscular-, hamstring, hip abductor and hip adductor performance tests performed over a three-month period in elite under-18 academy soccer players. Twenty-five players (age: 16.6 ± 0.9 years, height: 178 ± 7 cm, weight: 74 ± 7 kg, VO2max: 59 ± 4 ml/min/kg) took part in the study. In addition to evaluating adherence to the monitoring approach, data were analyzed using a linear support vector machine (SVM) to predict illness and injuries. The approach was feasible, with no injuries or dropouts due to the monitoring process. Questionnaire adherence was high at the beginning and decreased steadily towards the end of the study. An SVM resulted in the best classification results for three classification tasks, i.e., illness prediction, illness determination and injury prediction. For injury prediction, one of four injuries present in the test data set was detected, with 96.3% of all data points (i.e., injuries and non-injuries) correctly detected. For both illness prediction and determination, there was only one illness in the test data set that was detected by the linear SVM. However, the model showed low precision for injury and illness prediction with a considerable number of false-positives. The results demonstrate the feasibility of a holistic monitoring approach with the possibility of predicting illness and injury. Additional data points are needed to improve the prediction models. In practical application, this may lead to overcautious recommendations on when players should be protected from injury and illness.

Neuromuscular changes after a Long Distance Triathlon World Championship

ABSTRACTThis study aimed to determine the neuromuscular changes in muscle contractile properties and countermovement jump (CMJ) performance after a long distance (LD) triathlon, inquiring to what extent it is influenced by gender and the evaluated muscle, and to explore for response differences. Four elite (2 females and 2 males) and 18 well-trained triathletes (3 females and 15 males) who competed in the 2019 LD Triathlon World Championship undergone, prior and post-race, a CMJ and a muscle contractile properties assessment in vastus lateralis (VL) and biceps femoris (BF) using tensiomyography. A mixed ANOVA was carried out to detect triathletes' neuromuscular changes after the competition. A large decrease in jump height and flight time was found in CMJ (p = 0.001, ηp2 = 0.767) with gender differences (ηp2 = 0.308). contraction (Tc), delay (Td) and sustain times (Ts) also showed a large decrease (p = 0.001, ηp2 = 0.174-0.413). However, maximum radial muscle belly displacement was not altered by the competition, but did greatly increase radial displacement velocity (p = 0.031; ηp2 = 0.212). No gender differences were found in contractile properties. Correlation analysis between race performance and the jumping and tensiomyography parameters only showed a moderate negative correlation with Tc of the BF in pre- and post-competition (r = -0.44; -0.43; p = 0.05). In conclusion, triathletes after a LD World Championship suffer a sharp drop in jump performance and variations in VL's and BF's contractile properties, showing decreases in Tc, Td and Ts without gender differences. The regular use of these parameters can allow the monitoring of triathlete's neuromuscular fatigue and aid in the distribution of more efficient loads in their training cycles.HighlightsTrainers and researchers in neuromuscular fatigue can have reference data of elite and well-trained triathletes after performing LD race.The magnitude of change in the CMJ and the contractile properties of BF and VL achieved in competition by these elite reference triathletes can guide to modulate triathletes training.The regular use of the parameters using these references can allow an exhaustive neuromuscular fatigue monitoring during the sessions or training cycles throughout the season.

Synergistic Dominance Induced by Hip Extension Exercise Alters Biomechanics and Muscular Activity During Sprinting and Suggests a Potential Link to Hamstring Strain

ABSTRACT

Iguchi, J, Hojo, T, Fujisawa, Y, Kuzuhara, K, Yanase, K, Hirono, T, Koyama, Y, Tateuchi, H, and Ichihashi, N. Synergistic dominance induced by hip extension exercise alters biomechanics and muscular activity during sprinting and suggests a potential link to hamstring strain. J Strength Cond Res 37(9): 1770-1776, 2023-Hamstring strain is likely to occur during the late swing phase or the first half of the stance phase in sprinting. During the late swing phase, the hamstrings and gluteus maximus (Gmax) contract eccentrically to decelerate the lower limb. We hypothesized that, when the Gmax becomes dysfunctional because of delayed onset muscle soreness (DOMS), the hamstring workload is increased (i.e., there is synergetic dominance), which could lead to an increased risk of strain. A total of healthy 15 male undergraduate or graduate students (age 23.1 ± 1.28 years) were recruited to perform exercises and maximal sprints. On day 1, before subjects performing DOMS-causing exercises, and on day 3, while subjects were experiencing DOMS in the Gmax, lower-limb biomechanical and muscle activity data were recorded using a motion analysis system and electromyography (EMG), respectively. Data were analyzed and compared between day 1 and day 3. Hip flexion angle on day 3 was significantly lower than that on day 1, but the opposite was true for the knee flexion angle (P < 0.05). Vastus medialis (VM), biceps femoris (BF), and Gmax muscle activities on day 3 were significantly higher than those on day 1 (P < 0.05). Peak propulsive forces on day 3 were significantly higher than those on day 1 (P < 0.05). Kinematic changes such as decreased hip flexion angle and EMG changes such as increased BF EMG activity on day 3 to compensate for the loss of function of the Gmax may potentially increase the risk of hamstring strain.