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.

Hamstring muscle injuries in athletics.

Hamstring muscle injuries (HMI) are a common and recurrent issue in the sport of athletics, particularly in sprinting and jumping disciplines. This review summarizes the latest literature on hamstring muscle injuries in athletics from a clinical perspective. The considerable heterogeneity in injury definitions and reporting methodologies among studies still needs to be addressed for greater clarity. Expert teams have recently developed evidence-based muscle injury classification systems whose application could guide clinical decision-making; however, no system has been adopted universally in clinical practice, yet.The most common risk factor for HMI is a previously sustained injury, particularly early after return-to-sport. Other modifiable (e.g. weakness of thigh muscles, high-speed running exposure) and non-modifiable (e.g. older age) risk factors have limited evidence linking them to injury. Reducing injury may be achieved through exercise-based programs, but their specific components and their practical applicability remain unclear.Post-injury management follows similar recommendations to other soft tissue injuries, with a graded progression through stages of rehabilitation to full return to training and then competition, based on symptoms and clinical signs to guide the individual speed of the recovery journey. Evidence favoring surgical repair is conflicting and limited to specific injury sub-types (e.g. proximal avulsions). Further research is needed on specific rehabilitation components and progression criteria, where more individualized approaches could address the high rates of recurrent HMI. Prognostically, a combination of physical examination and magnetic resonance imaging (MRI) seems superior to imaging alone when predicting 'recovery duration,' particularly at the individual level.

Assessment of idiopathic inflammatory myopathy using a deep learning method for muscle T2 mapping segmentation.

OBJECTIVE: To investigate the utility of an automatic deep learning (DL) method for segmentation of T2 maps in patients with idiopathic inflammatory myopathy (IIM) against healthy controls, and also the association of quantitative T2 values in patients with laboratory and pulmonary findings. METHODS: Structural MRI and T2 mapping of bilateral thigh muscles from patients with IIM and healthy volunteers were segmented using dedicated software based on a pre-trained convolutional neural network. Incremental and federated learning were implemented for continuous adaptation and improvement. Muscle T2 values derived from DL segmentation were compared between patients and healthy controls, and T2 values of patients were further analyzed with serum muscle enzymes, and interstitial lung disease (ILD) which was diagnosed and graded based on chest HRCT. RESULTS: Overall, 64 patients (27 patients with dermatomyositis, 29 with polymyositis, and 8 with antisynthetase syndrome (ASS)) and 10 healthy controls were included. By using DL-based muscle segmentation, T2 values generated from T2 maps accurately differentiated patients from those of controls (p < 0.001) with a cutoff value of 36.4 ms (sensitivity 96.9%, and specificity 100%). In patients with IIM, muscle T2 values positively correlated with all the serum muscle enzymes (all p < 0.05). ILD score of patients with ASS was markedly higher than that of those without ASS (p = 0.011), while dissociation between the severity of muscular involvement and ILD was observed (p = 0.080). CONCLUSION: Automatic DL could be used to segment thigh muscles and help quantitatively assess muscular inflammation of IIM through T2 mapping. KEY POINTS: • Muscle T2 mapping automatically segmented by deep learning can differentiate IIM from healthy controls. • T2 value, an indicator of active muscle inflammation, positively correlates with serum muscle enzymes. • T2 mapping can detect muscle disease in patients with normal muscle enzyme levels.

Muscle Contraction Adaptations in Top-Level Karate Athletes Assessed by Tensiomyography.

BACKGROUND: This paper aimed to compare the involuntary stimulated neuromuscular response of thigh muscles in top-level karate athletes and recreational groups. METHODS: The study included 13 male karate athletes (KAs) and 14 non-athlete male individuals (NAs). Tensiomyographic (TMG) measurements were obtained from the rectus femoris (RF), vastus medialis (VM), vastus lateralis (VL), biceps femoris (BF) and semitendinosus (ST). RESULTS: Statistically significant differences were observed between KAs and NAs in knee extensor/flexor delay time (Td), contraction time (Tc), total contraction time (Tct), maximal radial displacement of the muscle belly (Dm) and rate of muscle tension development (RMTD). On a group level, KA dominant-leg extensors and flexors and also non-dominant-leg knee flexors had significant differences when compared to NA. Tct is a TMG parameter in which the KAs and NAs differ the most in the case of the knee extensors, while flexor muscles differ the most in the RMTD parameter. CONCLUSIONS: The lower Tct values indicate an improved ability of top-level karateka to make fast contractions of the agonist muscles. KAs' higher RMTD values suggest on strength characteristics needed in breaking actions of the antagonist muscles. Existence of contraction-relaxation-contraction neuromuscular pattern in the RF muscle suggests on implementation of training strategies that involves both rapid muscle contractions and relaxations.

Plasmablastic Lymphoma Mimicking Osteomyelitis of Femur in an Immunocompetent Individual: A Case Report.

Plasmablastic lymphoma (PBL) is an aggressive type of diffuse large B-cell lymphoma. It is most commonly seen in patients with human immunodeficiency virus (HIV) infection and other immunodeficiencies manifesting commonly in the form of oral lesions. Here, we report a case of an HIV-negative, immunocompetent elderly male who presented with a painful solitary tender lesion on the right anterior lateral thigh. A preliminary diagnosis of osteomyelitis (right femur) from a possibly infected dynamic compression plate was made following initial ultrasound and MRI of the right lower extremity. An attempt was made to incise and drain the lesion, which was abruptly stopped as it resulted in drainage of copious blood, leading to hemodynamic instability. Histopathology of the specimen revealed findings consistent with PBL. The diagnosis of PBL was further confirmed by immunohistochemical staining, which was positive for CD138, MUMI, and CD56 and negative for CD20 and ALK. Due to its rarity and heterogeneous presentations, PBL could be easily overlooked clinically in immunocompetent patients. Therefore, our case highlights the importance of considering the diagnosis of PBL even in lesions whose course is consistent with other infectious bone pathologies.

Computed tomography-based skeletal muscle and adipose tissue attenuation: Variations by age, sex, and muscle.

OBJECTIVE: This study aimed to investigate how skeletal muscle attenuation and adipose tissue (AT) attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle vary according to the targeted muscles, sex, and age. DESIGN: Population-based cross-sectional study. SETTING: Community-dwelling old population in Reykjavik, Iceland. SUBJECTS: A total of 5331 older adults (42.8% women), aged 66-96 years from the Age, Gene/Environment Susceptibility (AGES)- Reykjavik Study, who participated in the baseline visit (between 2002 and 2006) and had valid thigh and abdominal computed tomography (CT) scans were studied. METHODS: Muscle attenuation and AT attenuation of the quadriceps, hamstrings, paraspinal muscle groups and the psoas muscle were determined using CT. Linear mixed model analysis of variance was performed for each sex, with skeletal muscle or AT attenuation as the dependent variable. RESULTS: Muscle attenuation decreased, and AT attenuation increased with age in both sexes, and these differences were specific for each muscle, although not in all age groups. Age-related differences in muscle and AT attenuation varied with specific muscle. In general, for both sexes, skeletal muscle attenuation of the hamstrings declined more than average with age. Men and women displayed a different pattern in the age differences in AT attenuation for each muscle. CONCLUSIONS: Our data support the hypotheses that skeletal muscle attenuation decreases, and AT attenuation increases with aging. In addition, our data add new evidence, supporting that age-related differences in skeletal muscle and AT attenuation vary between muscles.

Association of Thigh Muscle Strength with Texture Features Based on Proton Density Fat Fraction Maps Derived from Chemical Shift Encoding-Based Water-Fat MRI.

PURPOSE: Based on conventional and quantitative magnetic resonance imaging (MRI), texture analysis (TA) has shown encouraging results as a biomarker for tissue structure. Chemical shift encoding-based water-fat MRI (CSE-MRI)-derived proton density fat fraction (PDFF) of thigh muscles has been associated with musculoskeletal, metabolic, and neuromuscular disorders and was demonstrated to predict muscle strength. The purpose of this study was to investigate PDFF-based TA of thigh muscles as a predictor of thigh muscle strength in comparison to mean PDFF. METHODS: 30 healthy subjects (age = 30 ± 6 years; 15 females) underwent CSE-MRI of the lumbar spine at 3T, using a six-echo 3D spoiled gradient echo sequence. Quadriceps (EXT) and ischiocrural (FLEX) muscles were segmented to extract mean PDFF and texture features. Muscle flexion and extension strength were measured with an isokinetic dynamometer. RESULTS: Of the eleven extracted texture features, Variance(global) showed the highest significant correlation with extension strength (p < 0.001, R2adj = 0.712), and Correlation showed the highest significant correlation with flexion strength (p = 0.016, R2adj = 0.658). Multivariate linear regression models identified Variance(global) and sex, but not PDFF, as significant predictors of extension strength (R2adj = 0.709; p < 0.001), while mean PDFF, sex, and BMI, but none of the texture features, were identified as significant predictors of flexion strength (R2adj = 0.674; p < 0.001). CONCLUSIONS: Prediction of quadriceps muscle strength can be improved beyond mean PDFF by means of TA, indicating the capability to quantify muscular fat infiltration patterns.

Evaluation of the Lower Limb Muscles' Electromyographic Activity during the Leg Press Exercise and Its Variants: A Systematic Review.

The aim of this study was to analyze the literature on muscle activation measured by surface electromyography (sEMG) of the muscles recruited when performing the leg press exercise and its variants. The Preferred Reporting Items of Systematic Reviews and Meta-Analyses (PRISMA) guidelines were followed to report this review. The search was carried out using the PubMed, Scopus, and Web of Science electronic databases. The articles selected met the following inclusion criteria: (a) a cross-sectional or longitudinal study design; (b) neuromuscular activation assessed during the leg press exercise, or its variants; (c) muscle activation data collected using sEMG; and (d) study samples comprising healthy and trained participants. The main findings indicate that the leg press exercise elicited the greatest sEMG activity from the quadriceps muscle complex, which was shown to be greater as the knee flexion angle increased. In conclusion, (1) the vastus lateralis and vastus medialis elicited the greatest muscle activation during the leg press exercise, followed closely by the rectus femoris; (2) the biceps femoris and the gastrocnemius medialis showed greater muscular activity as the knee reached full extension, whereas the vastus lateralis and medialis, the rectus femoris, and the tibialis anterior showed a decreasing muscular activity pattern as the knee reached full extension; (3) evidence on the influence of kinematics modifications over sEMG during leg press variants is still not compelling as very few studies match their findings.

Spatial difference can occur between activated and damaged muscle areas following electrically-induced isometric contractions.

KEY POINTS: T2 mapping combined to image registration and statistical parametric mapping analysis is a suitable methodology to accurately localize and compare the extent of both activated and damaged muscle areas. Activated muscle areas following electrically-induced isometric contractions are superficial, but damaged regions are muscle specific and can be related to the muscle morphology and/or the relative spatial position within a muscle group leading to potential intramuscular muscle shear strain. Tissues other than active skeletal muscle fibres can be altered during unaccustomed neuromuscular electrical stimulation-induced isometric contractions. ABSTRACT: Skeletal muscle isometric contractions induced by neuromuscular electrical stimulation (NMES) exercise can generate damage within activated muscles. This study aimed at comparing the localization and the extent of NMES-activated muscle areas and induced damage regions using magnetic resonance imaging. Thirteen healthy subjects performed a single bout of NMES-induced isometric contractions known to induce a decrease in maximal voluntary isometric contraction (MVC) and increase in muscle volume and transverse relaxation time (T2 ). All the parameters were measured before, immediately after (POST), 7 days (D7), 14 days (D14) and 21 days (D21) after the NMES session. Spatial normalization of T2 maps were performed to compare the localization of muscle activation areas and damaged muscle regions from statistical mapping analyses. A significant decrease in MVC was found at POST (-26 ± 9%) and in delayed time at D7 (-20 ± 6%) and D14 (-12 ± 5%). Although muscle activation was statistically detected through T2 increase at POST in superficial parts of the two muscles located beneath the stimulation electrodes (i.e. vastus lateralis and vastus medialis), alterations quantified in a delayed time from increased T2 were mainly located in the deep muscle region of the vastus lateralis (+57 ± 24% of mean T2 ) and superficial area of the vastus medialis (+24 ± 16% of mean T2 ) at D7 and were still observed in whole muscle at D21. The discrepancy between activated and damaged areas in the vastus lateralis implies that tissues other than active skeletal muscle fibres were altered during unaccustomed NMES-induced isomeric contractions.

Characteristics of individual thigh muscles including cross-sectional area and adipose tissue content measured by magnetic resonance imaging in knee osteoarthritis: a cross-sectional study.

This study aimed to identify the parameters related to the area and adipose tissue content of thigh muscles that are associated with radiographic knee osteoarthritis grade. Fifty patients (mean age ± standard deviation, 73.0 ± 4.5 years) were divided into early osteoarthritis (n = 23) and established osteoarthritis (n = 27) groups based on Kellgren-Lawrence classification. The femorotibial angle was measured from anteroposterior radiographs of the lower limbs. Individual thigh muscle and adipose tissue areas were analyzed using axial T1-weighted magnetic resonance imaging. After intergroup comparison, logistic regression analysis was performed to determine independent parameters associated with established osteoarthritis. Moreover, correlation coefficients were assessed between the left-right differences of osteoarthritis grade and parameters. Established osteoarthritis exhibited a significantly greater femorotibial angle and increased adipose tissue content in the subcutaneous, intermuscle, and intramuscle of the adductor, vastus lateralis, vastus intermedius, as well as a lower vastus medialis area, in comparison to early osteoarthritis. A greater femorotibial angle, increased intermuscular adipose tissue, and a lower vastus medialis area to knee extensor ratio were significantly independently associated with established osteoarthritis (odds ratio 3.2, 1.8, and 2.0, respectively). The left-right differences of femorotibial angle and vastus medialis area were significantly correlated with osteoarthritis grade, whereas adipose tissue content had no significant correlations with osteoarthritis grade. Greater femorotibial angle and lower vastus medialis area were related with higher osteoarthritis grade. Greater intermuscular adipose tissue content was associated with established osteoarthritis; however, in the left-right differences, adipose tissue content was not related with osteoarthritis grade.

Ultrasound Features of the Proximal Hamstring Muscle-Tendon-Bone Unit.

The hamstring muscle complex is made by a group of posterior biarticular thigh muscles, originating at the ischial tuberosity, which extend the hip and flex the knee joint. Proximal hamstring injuries are frequent among athletes, commonly involving their long myotendinous junction during an eccentric contraction. In this pictorial essay, we describe the ultrasound technique to visualize the normal anatomy of the proximal hamstring muscle-tendon-bone complex and present ultrasound findings in patients with traumatic injuries and tendinopathies.

Simultaneous Multislice Accelerated Diffusion Tensor Imaging of Thigh Muscles in Myositis.

OBJECTIVE: Diffusion tensor imaging (DTI) has long been proposed as a potential tool for quantitatively evaluating muscle lesions of dermatomyositis (DM) and polymyositis (PM), but adapting DTI to thigh muscles requires minimizing acquisition time. We investigated the clinical feasibility of using SMS-EPI-DTI (simultaneous multislice [SMS] accelerated echo planar imaging [EPI] DTI) to image and analyze the anisotropic diffusion characteristics of thigh muscles in patients with DM or PM. SUBJECTS AND METHODS: Both thighs of 20 patients (seven patients with DM and 13 patients with PM) and 10 healthy control subjects were prospectively scanned using SMSEPI-DTI. Tractographic images and DTI-derived parameters, including fractional anisotropy (FA) and apparent diffusion coefficient (ADC) values and three eigenvalues (λ1, λ2, and λ3), were obtained from four selected muscles (vastus medialis, vastus intermedius, adductor magnus, and semimembranosus) and were analyzed. After Bonferroni correction, p < 0.017 (0.05/3) was considered to denote statistical significance. RESULTS: SMS-EPI-DTI allowed imaging of both thighs of patients with DM or PM and healthy control subjects within approximately 5 minutes. For each of the four measured muscles, FA values for patients with edematous muscles were lower than those for patients with unaffected muscles and healthy control subjects with normal muscles (p < 0.017 for all). The ADC and λ1, λ2, and λ3 values of edematous muscles were significantly higher than those for patients with unaffected muscles and healthy control subjects (p < 0.017 for all). Unaffected muscles of patients and healthy control subjects were similar in terms of all parameters (p > 0.017 for all). CONCLUSION: SMS-EPI-DTI is clinically feasible for imaging thigh muscles and quantitatively evaluating edematous muscles of patients with DM or PM.

Trunk muscle quality assessed by computed tomography: Association with adiposity indices and glucose tolerance in men.

BACKGROUND/OBJECTIVES: Thigh muscle attenuation measured by computed tomography (CT) has been shown to be a reliable and useful index of skeletal muscle fat infiltration. Thigh muscle fat content assessed by CT has been linked to obesity and type 2 diabetes and is a correlate of insulin resistance in sedentary individuals. However, as measurement of mid-thigh fat content requires the assessment of another region of interest beyond the usual abdominal scan required to measure levels of visceral and subcutaneous abdominal adipose tissue, this study aimed at testing the hypothesis that skeletal muscle fat measured from a single abdominal scan (L4-L5) would also provide information relevant to the estimation of muscle fat infiltration as it relates to cardiometabolic risk. METHODS: Abdominal (L4-L5) and mid-thigh CT scans were performed in a sample of 221 sedentary men covering a wide range of adiposity values. Trunk muscles on the L4-L5 scan were classified into 2 groups: 1) psoas and 2) core muscles. The two scans were segmented to calculate muscle areas, mean attenuation values as well as low-attenuation muscle (LAM) areas, the latter being considered as an index of skeletal muscle fat infiltration. Body mass index (BMI), body composition and waist circumference were assessed and a 75 g oral glucose tolerance test (OGTT) was performed. RESULTS: Mid-thigh, psoas and core LAM areas were all significantly associated with body composition indices (0.46 ≤ r ≤ 0.71, p < 0.0001) whereas trunk muscle indices were more strongly associated with visceral adiposity and waist circumference (0.54 ≤ r ≤ 0.79, p < 0.0001) than were mid-thigh muscle variables (0.44 ≤ r ≤ 0.62, p < 0.0001). Mid-thigh LAM area as well as psoas and core LAM areas were significantly associated with fasting glucose, 2-h plasma glucose levels, the glucose area under the curve and with the HOMA-IR index (mid-thigh LAM area: 0.18 ≤ r ≤ 0.25, p < 0.01; psoas LAM area: 0.27 ≤ r ≤ 0.33, p < 0.0001; core LAM area: 0.24 ≤ r ≤ 0.34, p < 0.01). Multivariable stepwise regression analyses revealed that the associations between trunk muscle indices and glucose tolerance/insulin resistance were no longer significant after controlling for visceral adiposity measured at L4-L5. CONCLUSION: Our results suggest that CT-imaging derived indices of trunk muscle quality are related to glucose tolerance and visceral adiposity. However, the relationship between skeletal muscle fat and insulin resistance appears to be largely mediated by the concomitant variation in visceral adiposity. Finally, our results suggest that a single CT scan performed at L4-L5 is adequate to assess skeletal muscle fat content related to cardiometabolic risk.

Structural changes in the thigh muscles following trans-femoral amputation.

INTRODUCTION: Early ambulation is the principal objective in trans-femoral amputees. Postamputation modifications complicate the rehabilitation process due to a reduced control at the interface between stump and prosthesis. The aim of this study is to determine whether magnetic resonance imaging depicts the amount of fatty degeneration of the thigh muscles after trans-femoral amputation (TFA). METHODS: A total of 12 patients following a TFA on the basis of a bone neoplasm or metastasis with an evaluable postoperative MRI were identified. Using the Goutallier classification, the fatty degeneration of the thigh muscles was analyzed in the middle (M) and at the distal end (E) of the residual limb at T1 (10.6 months) and T2 (25.6 months). RESULTS: Analysis at two different levels showed different grades of fatty degeneration of thigh muscles after TFA at T1 and T2. Comparing fatty degeneration at both levels of the stump, the quadriceps femoris revealed a significant change (p = 0.01) at T1 and M. sartorius and adductor (p = 0.02) at T2. CONCLUSIONS: MRI is an excellent diagnostic tool to evaluate fatty degeneration after TFA. The highest amount of fatty degeneration of the quadriceps muscle was monitored within the first 10 months. Early physiotherapy is important to strengthen the remaining stump muscles during rehabilitation.

Three-dimensional comparison of intramuscular fat content between young and old adults.

BACKGROUND: Fat infiltration within skeletal muscle is known as intramuscular fat (IMF), which increases with aging. Studies have assessed IMF content, using the mid-thigh as a representative location. However, three-dimensional IMF distribution is not well understood. The aim of this study was to compare the IMF content in young and old adults by assessing its distribution along the length of the thigh. METHODS: Consecutive transaxial images of the right thighs in 15 young (age, 21.0 ± 0.4) and 15 old (age, 70.7 ± 3.8) were obtained by magnetic resonance imaging. We measured IMF cross-sectional area (CSA), skeletal muscle CSA and calculated volume- and CSA-based IMF content for the quadriceps femoris (QF), hamstring (HM) and adductor (AD). CSA-based calculations were performed at every 10% of femur length (Lf), with 0% Lf and 100% Lf indicating the proximal and distal ends of femur. RESULTS: IMF CSAs along the length of the thigh were similar in both age groups. In contrast, skeletal muscle CSAs in all three muscle groups were significantly lower in old adults than in young adults (variation: -15.2 to -1.6 cm2, P < 0.05). Thus, in volume-based measurements, the older adults had higher IMF contents than the younger adults (9.5% to 14.3% vs. 4.8% to 8.6%, respectively; P < 0.05). However, such age-dependent differences were not observed at the mid-thigh in the QF and AD. CONCLUSION: The results demonstrated an age-related increase in IMF content-confirmed in areas of the thigh-primarily based on finding lower amounts of skeletal muscle mass in CSAs in the older adults.

Quadriceps and hamstring muscle activity during cycling as measured with intramuscular electromyography.

PURPOSE: The aim of this study was to describe thigh muscle activation during cycling using intramuscular electromyographic recordings of eight thigh muscles, including the biceps femoris short head (BFS) and the vastus intermedius (Vint). METHODS: Nine experienced cyclists performed an incremental test (start at 170 W and increased by 20 W every 2 min) on a bicycle ergometer either for a maximum of 20 min or to fatigue. Intramuscular electromyography (EMG) of eight muscles and kinematic data of the right lower limb were recorded during the last 20 s in the second workload (190 W). EMG data were normalized to the peak activity occurring during this workload. Statistical significance was assumed at p ≤ 0.05. RESULTS: The vastii showed a greater activation during the 1st quadrant compared to other quadrants. The rectus femoris (RF) showed a similar activation, but with two bursts in the 1st and 4th quadrants in three subjects. This behavior may be explained by the bi-articular function during the cycling movement. Both the BFS and Vint were activated longer than, but in synergy with their respective agonistic superficial muscles. CONCLUSION: Intramuscular EMG was used to verify muscle activation during cycling. The activation pattern of deep muscles (Vint and BFS) could, therefore, be described and compared to that of the more superficial muscles. The complex coordination of quadriceps and hamstring muscles during cycling was described in detail.

Active knee range of motion assessment in elite track and field athletes: normative values.

BACKGROUND: flexibility is an important physical characteristic in athletes in terms of performance and injury prevention. Active Range Of Motion (AROM) was assessed in elite Greek track and field athletes. METHODS: prospective cohort study was carried out. In the period 2000-2010, the AROM was measured bilaterally with the Active Knee Extension (AKE) test during an in-season period with a goniometer in 127 athletes. RESULTS: male runners and jumpers had a higher mean AROM than throwers, but this result was not statistically significant. Female jumpers had a higher mean AROM than both runners and throwers, but the difference was also not statistically significant. CONCLUSION: in athletes, mean posterior thigh muscle flexibility is likely to be between 72.3° and 73.9°. Posterior thigh muscle flexibility is associated with performance, the higher the AROM, the better performance is achieved athletes have generally high AROM, and this may be a result of their increased muscle flexibility. The normative values of posterior thigh flexibility may assist in better monitoring rehabilitation of the posterior thigh muscle injuries and be useful in pre-season screening of athletes' flexibility.

Identification of hyperelastic properties of passive thigh muscle under compression with an inverse method from a displacement field measurement.

The mechanical behavior of muscle tissue is an important field of investigation with different applications in medicine, car crash and sport, for example. Currently, few in vivo imaging techniques are able to characterize the mechanical properties of muscle. Thus, this study presents an in vivo method to identify a hyperelatic behavior from a displacement field measured with ultrasound and Digital Image Correlation (DIC) techniques. This identification approach was composed of 3 inter-dependent steps. The first step was to perform a 2D MRI acquisition of the thigh in order to obtain a manual segmentation of muscles (quadriceps, ischio, gracilis and sartorius) and fat tissue, and then develop a Finite Element model. In addition, a Neo-Hookean model was chosen to characterize the hyperelastic behavior (C10, D) in order to simulate a displacement field. Secondly, an experimental compression device was developed in order to measure the in vivo displacement fields in several areas of the thigh. Finally, an inverse method was performed to identify the C10 and D parameters of each soft tissue. The identification procedure was validated with a comparison with the literature. The relevance of this study was to identify the mechanical properties of each investigated soft tissues.

Effect of pre-fatigue method by leg extension exercise on recruitment state of synergists in thigh muscles during leg press exercise / 体力科学

The purpose of this study was to examine the recruitment state of synergistic muscles in the thigh muscles in leg press exercise with and without pre-fatigue method using transverse relaxation time (T2) on muscle functional magnetic resonance imaging (MRI). Nine healthy male subjects performed the following two types of exercise trials on separate days: 1) 5 sets of a leg press exercise with pre-fatigue method, which consisted of 3 sets of knee extension exercise (LP-pre), 2) 5 sets of a leg press exercise without pre-fatigue method (LP). Both exercises were performed at a load of 80% one-repetition maximum. Before and immediately after exercise, T2-weighted MR images of right-thigh were taken to calculate T2 values of twelve-thigh muscles. The T2 values for quadriceps femoris muscle and hamstrings in LP increased significantly after the exercise, except in the adductor magnus, adductor longus, gracilis, and sartorius. In contrast, the T2 values for all of the twelve-thigh muscles in LP-pre increased significantly after the exercise. Upon comparison between the two trials, the percentage changes in T2 value for the adductor magnus, adductor longus, and sartorius in LP-pre were found to be significantly greater than those in LP. These results suggest leg press exercise with pre-fatigue method may be effective to increase activity of synergistic muscles in thigh muscles during exercise.