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Wearable robots, sometimes known as exoskeletons, are incredible devices for improving human strength, reducing fatigue, and restoring impaired mobility. The control of powered exoskeletons, on the other hand, is still a challenge. This necessitates the development of a technique to simulate exoskeleton–wearer interaction. This study uses a two-dimensional human skeletal model with a powered knee exoskeleton to predict the optimal lifting motion and assistive torque. For lifting motion prediction, an inverse dynamics optimization formulation is utilized. In addition, the electromechanical dynamics of the exoskeleton DC motor are modeled in the lifting optimization formulation. The design variables are human joint angle profiles and exoskeleton motor current profiles. The human joint torque square is minimized subject to physical and lifting task constraints. Then, the lifting optimization problem is solved by the gradient-based sparse nonlinear optimizer (SNOPT). Furthermore, the optimal exoskeleton torque is implemented through a two-phase control strategy to provide optimal assistance in lifting. Experimental validations of the optimal control with 6 Nm and 16 Nm maximum assistive torque are presented. Both 6 Nm and 16 Nm maximum optimal assistance of the exoskeletons reduce the mean values of vastus lateralis, biceps femoris, and latissimus dorsi muscle activations compared to the lifting without the exoskeleton. However, the mean value of the vastus medialis activation is increased by a small amount for the exoskeleton case, although its peak value is reduced. Finally, the experimental results demonstrate that the proposed lifting optimization formulation and control strategy are promising for powered knee exoskeleton for lifting tasks. [ABSTRACT FROM AUTHOR]

Background: The body exhibits dynamic and static movements in response to the changes in the center of gravity in some positions. Balance plays a key role in all sports branches and daily life because it can control the lowest energy consumption and muscle activation. Objectives: This study investigated the effects of lower extremity static muscle fatigue on static and dynamic balance components. Design/methods: The sample consisted of 40 healthy volunteers aged 18–24 years. Participants took part in an isometric fatigue protocol for lower extremity muscles. A squat position was used for static fatigue for lower extremity muscles. Measurements were performed in a squat press for 25 s, with the knee at a 90-degree angle and a load of about 30% of the participant's weight isometrically. The protocol was repeated five times. The participant was allowed to rest for two minutes between each repetition. The muscles and their antagonists that contracted most actively during the squat press exercise were vastus lateralis obliquus, rectus femoris, tibialis anterior, biceps femoris, semi tendineus, and lateral gastrocnemius. Electromyography (EMG) measurements were conducted on these muscles bilaterally and motion analysis system was used to standardize the 90-degree angle of the knee joint. Results: There was a significant difference between pre-test and post-test Eyes Open (EO) static balance scores, pre- and post-exercise post-test dynamic balance scores between non-athletes and athletes, pre- and post-exercise post-test dominant leg EO, and pre-test non-dominant leg between non-athletes and athletes (p <.05). There was a significant difference in the Median Frequency (MF) (Hz) values of the dominant leg agonist rectus femoris (p <.05) and the antagonist muscle semi tendineus (p <.05) scores during isometric squat press between athletes and non-athletes. Conclusions: We need different applications to understand the mechanisms underlying balance and discover athletes' potential. Lower extremity proprioception exercises have positive effects on static body balance parameters. [ABSTRACT FROM AUTHOR]

Purpose: The purpose of this study was to assess if differences in hamstring strength, hamstring-to-quadriceps (H:Q) strength ratio, and biceps femoris long head (BFLH) fascicle length exist between male and female professional football (soccer) players. Methods: One-hundred professional footballers participated in this cross-sectional study: 50 men and 50 women. Ultrasound images of BFLH muscle and isokinetic dynamometry tests were performed. Results: Men were stronger than women for hamstring concentric (2.01 ± 0.21 Nm/kg vs. 1.55 ± 0.23 Nm/kg; p < 0.001; large effect size, 2.08) and eccentric (2.87 ± 0.45 Nm/kg vs. 2.39 ± 0.32 Nm/kg; p < 0.001; large effect size, 1.23) peak torques. There was no sex-related difference for H:Q conventional ratio (concentric/concentric; 0.55 ± 0.06 vs. 0.55 ± 0.07); but women presented greater H:Q functional ratio (eccentric/concentric; 0.78 ± 0.12 vs. 0.85 ± 0.09; p = 0.003; moderate effect size, 0.66). Men and women presented similar BFLH fascicle length: 0.24 ± 0.05 vs. 0.23 ± 0.05 (values normalized by muscle length). Conclusions: Among the muscular factors assessed in this study, men presented stronger hamstring muscles, women presented greater H:Q functional ratio, and there was no sex-related differences for H:Q conventional ratio or BFLH fascicle length. [ABSTRACT FROM AUTHOR]

The consumer's interest in his/her health and the quality of his/her food has increased as well as in environmental issues such as animal welfare. Consumers believe that organic and similar (traditional) production systems are more advantageous for consumers (providing healthier food) and animals (providing better welfare). The aim of the study was to evaluate the impact of different rearing systems (organic, conventional and traditional) on the physicochemical properties and oxidation states of pork meat. The meat samples were obtained from three different rearing systems of pigs: organic, conventional and traditional. The samples (M. biceps femoris) were obtained from producers directly 3 days after slaughtering for analysis. The following physical and chemical parameters were analyzed: color (according to the CIE L * a * b * system), pH, dry matter, protein, collagen, fat and ash. The oxidation state of the meat samples was measured by thiobarbituric acid reactive substances (TBARSs), free fatty acid (FFA) and antioxidant capacity (2,2-diphenyl-1-picrylhydrazyl). The results indicated that the rearing system affects most of the evaluated parameters. A significant difference (p < 0.05) was observed in color parameters L* and b*, where the conventional pork samples were darker and the organic pork yellower. Total protein content in meat of pigs raised in a conventional system was higher (22.23%) than for organic (20.36%) and traditional (21.21%). The fat content in the meat of organically reared pigs was higher (2.81%) than in pork from conventional and traditional systems (1.43% and 0.37%, respectively). Organic pork was more susceptible to oxidation processes due to its higher TBARS (1.24 mg/kg) and FFA (1.15% fat as oleic acid) values and lower antioxidant capacity (26.42% inhibition), which may result in inferior technological properties of meat. [ABSTRACT FROM AUTHOR]

Background and Aims Genu varus is one of the most common lower limb deformities that can affect a person's daily activities and sports performance. This study aims to investigate the effect of the 8-week use of knee braces on the electrical activity frequency of muscles in men with genu varus during walking. Methods This is a quasi-experimental study on 30 male college students with genu varus (aged 20-30 years) who were randomly divided into control and intervention groups. Corrective exercises were performed for 8 weeks using knee braces in the intervention group. The electrical activity of selected muscles was recorded by an electromyography system. For statistical analysis, ANCOVA was used. The significance level was set at 0.05. Results During the loading phase, the results showed a lower frequency of biceps femoris muscle in the intervention group compared to the control group (P=0.041). The frequency of muscles did not show any significant difference between groups in the mid-stance and push-off phases (P>0.05). Conclusion Given the decrease in the frequency of biceps femoris muscle activity in men who used knee braces, it can be concluded that the 8-week use of these brace can be effective in reducing shock absorption in the lower extremity. [ABSTRACT FROM AUTHOR]

Sixty percent of all law enforcement officers (LEOs) experience low back pain (LBP), with the LEO duty belt (LEODB) commonly reported to be a contributing factor. The primary purpose of the study was to investigate the LEODB's effect on muscular activity and compare it to a tactical vest, which is a commonly used alternative to an LEODB. In total, 24 participants (13 male, 11 female; mass, 73.0 ± 11.1 kg; height, 169.0 ± 10.0 cm; age, 24.0 ± 5.8 years) completed a progressive series of hip hinge tasks in a single testing session. All participants completed four conditions (no belt, leather belt, nylon belt, and weight VEST) in a randomized order. Surface electromyography (sEMG) sensors were placed bilaterally on the rectus abdominus, multifidus, biceps femoris, and rectus femoris. Across all tasks, no significant effects of load on muscle activity were found for any of the muscles. Participants rated the VEST condition as more comfortable (p < 0.05) and less restrictive (p < 0.05) than either LEODB. The findings suggest an LEODB does not alter muscle activity during bodyweight hip hinging or lifting objects from the ground. Future research should examine whether changes in muscle activity occur with durations of LEODB wear more similar to an actual work shift duration for LEOs (≥8 h). [ABSTRACT FROM AUTHOR]

Background: Ultrasound is a powerful tool for diagnostic purposes and provides insight into both normal and pathologic tissue structure. Spatial frequency analysis (SFA) methods characterize musculoskeletal tissue organization from ultrasound images. Both sonographers in clinical imaging and researchers may alter a minimized range of ultrasound settings to optimize image quality, and it is important to know how these small adjustments of these settings affect SFA parameters. The purpose of this study was to investigate the effects of making small adjustments in a typical default ultrasound machine setting on extracted spatial frequency parameters (peak spatial frequency radius (PSFR), Mmax, Mmax%, and Sum) in the biceps femoris muscle. Methods: Longitudinal B-mode images were collected from the biceps femoris muscle in 36 participants. The window depth, foci locations, and gain were systematically adjusted consistent with clinical imaging procedures for a total of 27 images per participant. Images were analyzed by identifying a region of interest (ROI) in the middle portion of the muscle belly in a template image and using a normalized two-dimensional cross-correlation technique between the template image and subsequent images. The ROI was analyzed in the frequency domain using conventional SFA methods. Separate linear mixed effects models were run for each extracted parameter. Results: PSFR was affected by modifications in focus location only (p < 0.001) with differences noted between all locations. Mmax% was influenced by the interaction of gain and focus location (p < 0.001) but was also independently affected by increasing window depth (p < 0.001). Both Mmax and Sum parameters were sensitive to small changes in machine settings with the interaction of focus location and window depth (p < 0.001 for both parameters) as well as window depth and gain (p < 0.001 for both) influencing the extracted values. Conclusions: Frequently adjusted imaging settings influence some SFA statistics. PSFR and Mmax% appear to be most robust to small changes in image settings, making them best suited for comparison across individuals and between studies, which is appealing for the clinical utility of the SFA method. [ABSTRACT FROM AUTHOR]

Cycling exercise in older individuals is beneficial for the cardiovascular system and quadriceps muscles, including partially reversing the age‐related loss of quadriceps muscle mass. However, the effect of cycling exercise on the numerous other lower limb muscles is unknown. Six older men (74 ± 8 years) underwent MRI before and after 12‐weeks of progressive aerobic cycle exercise training (3–4 days/week, 60–180 min/week, 60%–80% heart rate reserve, VO2max: +13%) for upper (rectus femoris, vastii, adductor longus, adductor magnus, gracilis, sartorius, biceps femoris long head, biceps femoris short head, semimembranosus, semitendinosus) and lower (anterior tibial, posterior tibialis, peroneals, flexor digitorum longus, lateral gastrocnemius, medial gastrocnemius, soleus) leg muscle volumes. In the upper leg, cycle exercise training induced hypertrophy (p ≤ 0.05) in the vastii (+7%) and sartorius (+6%), with a trend to increase biceps femoris short head (+5%, p = 0.1). Additionally, there was a trend to decrease muscle volume in the adductor longus (−6%, p = 0.1) and biceps femoris long head (−5%, p = 0.09). In the lower leg, all 7 muscle volumes assessed were unaltered pre‐ to post‐training (−2% to −3%, p > 0.05). This new evidence related to cycle exercise training in older individuals clarifies the specific upper leg muscles that are highly impacted, while revealing all the lower leg muscles do not appear responsive, in the context of muscle mass and sarcopenia. This study provides information for exercise program development in older individuals, suggesting other specific exercises are needed for the rectus femoris and adductors, certain hamstrings, and the anterior and posterior lower leg muscles to augment the beneficial effects of cycling exercise for older adults. [ABSTRACT FROM AUTHOR]

Purpose: Long exhausted running causes pain at the lateral femoral epicondyle for some runners. The pain has been revealed to be related to the behavior of the iliotibial band (ITB) during running. The purpose of this study is to examine the effects of in-series musculature on the behavior of the ITB in healthy participants during an exhaustive run. Methods: Twenty-five healthy participants (15 males, 10 females) were recruited in the current study. All participants performed a 30-minute exhaustive run at a self-selected speed with laboratory-provided footwear. Muscle activities of ITB-related muscles including tensor fascia latae (TFL), gluteus maximus (Gmax), gluteus medius (Gmed), biceps femoris (BF), and vastus lateralis (VL) were recorded using surface electromyography (EMG). Results: Maximum amplitudes at the initial stage (the first minute), the mid stage (the 15-minute), and the end stage (the 30-minute) were compared during the exhaustive running. Significant decreases (p < 0.05) were observed in the maximum amplitudes of the TFL, Gmax, Gmed, and BF at the mid (decreased by ~ 15%) and end (decreased by ~ 30%) stages compared to the initial stage. The onset and the offset remained unaltered during the running (p ≥ 0.05). Conclusion: The behavior of the healthy ITB might be altered due to the activities of the in-series musculature. Excessive compression forces might be applied to the lateral femoral epicondyle from the ITB to provide stability for the knee joint during an exhaustive run. The findings could provide a basic understanding of the behavior of healthy ITB. [ABSTRACT FROM AUTHOR]

Background: Tensiomyography measures the radial displacement of a muscle during an electrically evoked twitch contraction. Different concepts to determine the rate of displacement (Vc) from the maximum twitch exist, but information on their reproducibility is scarce. Further, different inter-stimuli intervals during progressive stimulation are used, but the effect of different intervals on Vc is unclear. Objectives: The first aim of this study was to investigate the within and between-day reliability of the five most frequently used Vc concepts. The second aim was to investigate the effect of different inter-stimuli intervals on Vc. Methods: On two consecutive days, we determined Vc of the biceps femoris long head and rectus femoris of twenty-four healthy subjects. The maximum displacement was determined twice within three minutes on day one and a third time 24 h later. Also, on day two, we applied three blocks of ten consecutive stimuli at a constant intensity of 50 mA, separated by 3 min each. Inter-stimuli intervals in randomly ordered blocks were 10 s, 20 s or 30 s, respectively. Results: All Vc concepts displayed good to excellent relative (ICC 0.87–0.99) and generally good absolute within- and between-day reliability for both muscles. Across Vc-concepts, absolute reliability was higher for the rectus femoris (CV% 1.3–7.95%) compared to the biceps femoris (CV% 6.06–15.30%). In both muscles, Vc was generally not affected by different inter-stimuli intervals. For most Vc concepts, repeated stimulation induced an increase regardless of the inter-stimuli interval, but this effect was mainly trivial and small at most. Conclusions: The reproducibility of Vc concepts was generally good but varies between different muscles. A rest interval of 10 s seems preferable to longer intervals for less time required per measurement. Following this initial study, the effect of different inter-stimuli intervals on Vc should be further investigated. [ABSTRACT FROM AUTHOR]

The Huai pig is a well-known indigenous pig breed in China. The main advantages of Huai pigs over Western commercial pig breeds include a high intramuscular fat (IMF) content and good meat quality. There are significant differences in the meat quality traits of the same muscle part or different muscle parts of the same variety. To investigate the potential genetic mechanism underlying the meat quality differences in different pig breeds or muscle groups, longissimus dorsi (LD), psoas major (PM), and biceps femoris (BF) muscle tissues were collected from two pig breeds (Huai and Duroc). There were significant differences in meat quality traits and amino acid content. We assessed the muscle transcriptomic profiles using high-throughput RNA sequencing. The IMF content in the LD, PM, and BF muscles of Huai pigs was significantly higher than that in Duroc pigs (p < 0.05). Similarly, the content of flavor amino acids in the three muscle groups was significantly higher in Huai pigs than that in Duroc pigs (p < 0.05). We identified 175, 110, and 86 differentially expressed genes (DEGs) between the LD, PM, and BF muscles of the Huai and Duroc pigs, respectively. The DEGs of the different pig breeds and muscle regions were significantly enriched in the biological processes and signaling pathways related to muscle fiber type, IMF deposition, lipid metabolism, PPAR signaling, cAMP signaling, amino acid metabolism, and ECM–receptor interaction. Our findings might help improve pork yield by using the obtained DEGs for marker-assisted selection and providing a theoretical reference for evaluating and improving pork quality. [ABSTRACT FROM AUTHOR]

Surface electromyogram (SEMG) shows the vital information of human motor activity. This information can identify the motor activity and controlling assistive and rehabilitative devices. However, its efficient extraction and interpretation plays a very critical role. The present study is focused on lower limb activity classification by selecting the efficient feature vector of the lower limb SEMG signal. Here, the SEMG signal-dependent continuous locomotion mode classification method has been proposed along with a dual-stage Feature Selection Algorithm (FSA). To evaluate the proposed method, SEMG signals of fifteen subjects were recorded from two lower limb muscles (Fibularis longus and Biceps Femoris) for five lower limb activities. The performance of six different classifiers was compared for intuitive feature vectors and FSA. The study analysed the performance of the proposed model for a single muscle approach and a dual muscle approach of activity classification. The time domain features were found more effective over other features, whereas Biceps Femoris muscle came out as a dominant muscle. The FSA enhanced the performance of classification model with fewer features as compared to intuitive feature subsets. Moreover, the dual muscle approach outperformed (p-value<0.05) over the single muscle approach. The best performance, for the dual muscle approach, was achieved 97.73 ± 2.47%, 98.99 ± 1.26% and 96.33 ± 2.70% for Neural Network, Linear Discriminant Analysis and Support Vector Machine classifiers, respectively (p-value > 0.05). [ABSTRACT FROM AUTHOR]

The structural and functional differences of individual hamstrings have not been sufficiently evaluated. This study aimed to clarify the morphological architecture of the hamstrings including the superficial tendons in detail using isolated muscle specimens, together with quantification of structural parameters of the muscle. Sixteen lower limbs of human cadavers were used in this study. The semimembranosus (SM), semitendinosus (ST), biceps femoris long head (BFlh), and biceps femoris short head (BFsh) were dissected from cadavers to prepare isolated muscle specimens. Structural parameters, including muscle volume, muscle length, fiber length, sarcomere length, pennation angle, and physiological cross‐sectional area (PCSA) were measured. In addition, the proximal and distal attachment areas of the muscle fibers were measured, and the proximal/distal area ratio was calculated. The SM, ST, and BFlh were spindle‐shaped with the superficial origin and insertion tendons on the muscle surface, and the BFsh was quadrate with direct attachment to the skeleton and BFlh tendon. The muscle architecture was pennate in the four muscles. The four hamstrings possessed either of two types of structural parameters, one with shorter fiber length and larger PCSA, as in the SM and BFlh, and the other with longer fiber length and smaller PCSA, as in the ST and BFsh. Sarcomere length was unique in each of the four hamstrings, and thus the fiber length was suitably normalized using the average sarcomere length for each, instead of uniform length of 2.7 μm. The proximal/distal area ratio was even in the SM, large in the ST, and small in the BFsh and BFlh. This study clarified that the superficial origin and insertion tendons are critical determinants of the unique internal structure and structural parameters representing the functional properties of the hamstring muscles. [ABSTRACT FROM AUTHOR]

Background. Tai Chi is an excellent traditional Chinese physical fitness exercise, and its unique balancing movements are very important for improving human balance. In this study, the two most representative Tai Chi balance movements, "knee lift balance" and "leg stirrup balance", were selected to establish the lower limb bone muscle model of Tai Chi balance movements by using computer simulation modeling technology, aiming to analyze the characteristics of the lower limb movement mechanisms of typical balance movements, to provide a quantitative theoretical basis for improving the scientific level of Tai Chi. Method. A total of 16 subjects were recruited for this study. the BTS three-dimensional motion capture system and three-dimensional force platform were used for motion data acquisition, the physiological electromyographic signals were collected using BTS surface electromyography, and the lower limb bone muscle model of Tai Chi balance movements was established by AnyBody human simulation. Result. In the knee lift balancing movement, the balance leg hip abduction/adduction angle, hip flexion/extension moment, and the strength of the rectus femoris muscle, biceps femoris short capitis, and iliacus muscle of the amateur group was significantly smaller than that of the professional group (P < 0:01). In the leg stirrup balance movement, the knee flexion/extension angle of the balancing leg in the amateur group was significantly greater than that in the professional group (P < 0:01), and the hip flexion/extension angle, hip inversion/abduction angle, knee flexion/extension moment, hip flexion/extension moment, the strength iliacus, gluteus maximus, and obturator internus were significantly smaller than those in the professional group (P <0:01). The integral EMG of the biceps femoris of the support leg in the amateur group was significantly smaller than that of the professional group (P < 0:01). The integral EMG of the lateral femoral muscle of the balance leg was significantly smaller than that of the professional group (P <0:01). Conclusion. In this study, we found that the balancing leg of the balancing movement has a larger hip joint angle, the stirrup balancing knee joint angle is smaller, and the hip and knee joint moments are larger. This is related to joint activity and muscle activation, and amateurs should pay attention to increasing the range of motion of the hip joint and decreasing the range of motion of the knee joint when practicing to better stimulate exercise of the lower limb joints. In addition, the practice of balancing movements should strengthen the iliacus muscle, which plays an important role in maintaining the stable balance of the lower limbs, and strengthen the knee flexor and extensor muscles and hip adductor/abductor muscles of the balancing leg, thus promoting the stability of the balancing leg movements. [ABSTRACT FROM AUTHOR]

Knowledge about the acute effects of supramaximal-loaded resistance exercises on muscle mechanical properties is scarce. Therefore, this study aimed to examine changes in dominant limb biceps femoris and vastus lateralis oscillation frequency and stiffness before and after high- and supramaximal-loaded front squats. Nineteen male handball players participated in the experimental session with a barbell front squat 1RM. The first set was performed at 70% of the 1RM for four repetitions, and the second and third sets were performed at 90%1RM in an eccentric–concentric or an eccentric-only manner at 120% of the 1RM for three repetitions. The handheld myometer was used for the measurement of the biceps femoris and vastus lateralis stiffness and the oscillation frequency of the dominant limb 5 min before and at the 5th and 10th min after front squats. A two-way ANOVA neither indicated a statistically significant interaction (p = 0.335; η2 = 0.059 and p = 0.103; η2 = 0.118), the main effect of a condition (p = 0.124; η2 = 0.126 and p = 0.197; η2 = 0.091), nor the main effect of the time point (p = 0.314; η2 = 0.06 and p = 0.196; η2 = 0.089) for vastus lateralis and biceps femoris stiffness. However, there was a statistically significant interaction (F = 3.516; p = 0.04; η2 = 0.163) for vastus lateralis oscillation frequency. The post hoc analysis showed a significantly higher vastus lateralis oscillation frequency at POST (p = 0.037; d = 0.29) and POST_10 (p = 0.02; d = 0.29) compared to PRE during the SUPRA condition. Moreover, Friedman's test indicated statistically significant differences in biceps femoris oscillation frequency (test = 15.482; p = 0.008; Kendall's W = 0.163). Pairwise comparison showed a significantly lower biceps femoris oscillation frequency in POST (p = 0.042; d = 0.31) and POST_10 (p = 0.015; d = 0.2) during the HIGH condition compared to that in the corresponding time points during the SUPRA condition. The results of this study indicate that the SUPRA front squats, compared to the high-loaded ones, cause a significant increase in biceps femoris and vastus lateralis oscillation frequency. [ABSTRACT FROM AUTHOR]

Advancements in instrumentation support improved powered ankle prostheses hardware development. However, control algorithms have limitations regarding number and type of sensors utilized and achieving autonomous adaptation, which is key to a natural ambulation. Surface electromyogram (sEMG) sensors are promising. With a minimized number of sEMG inputs an economic control algorithm can be developed, whereas limiting the use of lower leg muscles will provide a practical algorithm for both ankle disarticulation and transtibial amputation. To determine appropriate sensor combinations, a systematic assessment of the predictive success of variations of multiple sEMG inputs in estimating ankle position and moment has to conducted. More importantly, tackling the use of nonnormalized sEMG data in such algorithm development to overcome processing complexities in real-time is essential, but lacking. We used healthy population level walking data to (1) develop sagittal ankle position and moment predicting algorithms using nonnormalized sEMG, and (2) rank all muscle combinations based on success to determine economic and practical algorithms. Eight lower extremity muscles were studied as sEMG inputs to a long-short-term memory (LSTM) neural network architecture: tibialis anterior (TA), soleus (SO), medial gastrocnemius (MG), peroneus longus (PL), rectus femoris (RF), vastus medialis (VM), biceps femoris (BF) and gluteus maximus (GMax). Five features extracted from nonnormalized sEMG amplitudes were used: integrated EMG (IEMG), mean absolute value (MAV), Willison amplitude (WAMP), root mean square (RMS) and waveform length (WL). Muscle and feature combination variations were ranked using Pearson’s correlation coefficient (r > 0.90 indicates successful correlations), the root-mean-square error and one-dimensional statistical parametric mapping between the original data and LSTM response. The results showed that IEMG+WL yields the best feature combination performance. The best performing variation was MG + RF + VM (rposition = 0.9099 and rmoment = 0.9707) whereas, PL (rposition = 0.9001, rmoment = 0.9703) and GMax+VM (rposition = 0.9010, rmoment = 0.9718) were distinguished as the economic and practical variations, respectively. The study established for the first time the use of nonnormalized sEMG in control algorithm development for level walking. [ABSTRACT FROM AUTHOR]

Cerebral palsy is a neurologic disorder caused by lesions on an immature brain, often resulting in spasticity and gait abnormality. This study aimed to compare the muscle activation patterns of real level and stair walking with those of simulated walking using an end-effector-type robot in children with spastic cerebral palsy. The electromyographic activities of the vastus lateralis, biceps femoris, tibialis anterior and medial gastrocnemius of nine children with spastic bilateral cerebral palsy were measured during gait using a wireless surface EMG device. Morning walk was used for the simulated gait. Differences in the muscle activation patterns between the real and simulated gait conditions were analyzed. In the loading response, all four muscles showed reduced activity during two simulated conditions. In mid-stance, mGCM showed reduced activity during simulated conditions, whereas BFem showed greater activity during simulated level walking. In the swing phase, BFem and TAnt activity was reduced during the simulated conditions. The onset–offset of the VLat, BFem and TAnt activity was significantly delayed during simulated versus real level walking. No differences in activity onset–offset were observed between the simulated level and stair conditions. In conclusion, the robot-simulated gait showed differences in its muscle activation patterns compared with the real gait conditions, which must be considered for gait training using an end-effector-type robot. [ABSTRACT FROM AUTHOR]

The reliability of surface electromyography (sEMG) has not been adequately demonstrated in the equine literature and is an essential consideration as a methodology for application in clinical gait analysis. This observational study investigated within-session, intra-subject (stride-to-stride) and inter-subject reliability, and between-session reliability of normalised sEMG activity profiles, from triceps brachii (triceps), latissimus dorsi (latissimus), longissimus dorsi (longissimus), biceps femoris (biceps), superficial gluteal (gluteal) and semitendinosus muscles in n = 8 clinically non-lame horses during in-hand trot. sEMG sensors were bilaterally located on muscles to collect data during two test sessions (session 1 and 2) with a minimum 24-hour interval. Raw sEMG signals from ten trot strides per horse and session were DC-offset removed, high-pass filtered (40 Hz), full-wave rectified, and low-pass filtered (25 Hz). Signals were normalised to peak amplitude and percent stride before calculating intra- and inter-subject ensemble average sEMG profiles across strides for each muscle and session. sEMG profiles were assessed using waveform similarity statistics: the coefficient of variation (CV) to assess intra- and inter-subject reliability and the adjusted coefficient of multiple correlation (CMC) to evaluate between-session reliability. Across muscles, CV data revealed that intra-horse sEMG profiles within- and between-sessions were comparatively more reliable than inter-horse profiles. Bilateral gluteal, semitendinosus, triceps and longissimus (at T14 and L1) and right biceps showed excellent between-session reliability with group-averaged CMCs > 0.90 (range 0.90–0.97). Bilateral latissimus and left biceps showed good between-session reliability with group-averaged CMCs > 0.75 (range 0.78–0.88). sEMG profiles can reliably describe fundamental muscle activity patterns for selected equine muscles within a test session for individual horses (intra-subject). However, these profiles are more variable across horses (inter-subject) and between sessions (between-session reliability), suggesting that it is reasonable to use sEMG to objectively monitor the intra-individual activity of these muscles across multiple gait evaluation sessions at in-hand trot. [ABSTRACT FROM AUTHOR]

Simple Summary: The current work revealed the developmental characteristics of skeletal muscle and the expression patterns of related regulatory genes in the embryonic stage of quails. During the embryonic stage, the weight and fiber size of the leg muscle was larger than the breast muscle. The MyoD and Pax7 genes were critical myogenic regulatory factors and were highly expressed in the middle stage of the embryonic period in breast and leg muscles. Overall, these results imply that day 12 of quail embryos may be a crucial point for muscle development. The quail is an important research model, and the demand for quail meat has been increasing in recent years; therefore, it is worthwhile investigating the development of embryonic skeletal muscle and the expression patterns of regulatory genes. In this study, the expression of MyoD and Pax7 in the breast muscle (m. pectoralis major) and leg muscle (m. biceps femoris) of quail embryos on days 10 through 17 were determined using qRT-PCR. Paraffin sections of embryonic muscle were analyzed to characterize changes over time. Results showed that MyoD and Pax7 were expressed in both breast and leg muscles and played a significant role in embryonic muscle development. Compared to breast muscle, leg muscle grew faster and had greater weight and myofiber size. The findings suggested that embryonic day 12 (E12) may be a key point for muscle development. Correlation analysis showed that MyoD expression was significantly negatively correlated with muscle and embryo weight, whereas Pax7 gene expression had no significant correlation with these characteristics. These fundamental results provide a theoretical basis for understanding the characteristics and transition points of skeletal muscle development in quail embryos and an important reference for farmers raising quail from eggs. [ABSTRACT FROM AUTHOR]

Dystrophic muscle is characterized by necrosis/regeneration cycles, inflammation, and fibro-adipogenic development. Conventional histological stainings provide essential topographical data of this remodeling but may be limited to discriminate closely related pathophysiological contexts. They fail to mention microarchitecture changes linked to the nature and spatial distribution of tissue compartment components. We investigated whether label-free tissue autofluorescence revealed by Synchrotron deep ultraviolet (DUV) radiation could serve as an additional tool for monitoring dystrophic muscle remodeling. Using widefield microscopy with specific emission fluorescence filters and microspectroscopy defined by high spectral resolution, we analyzed samples from healthy dogs and two groups of dystrophic dogs: naïve (severely affected) and MuStem cell-transplanted (clinically stabilized) animals. Multivariate statistical analysis and machine learning approaches demonstrated that autofluorescence emitted at 420–480 nm by the Biceps femoris muscle effectively discriminates between healthy, dystrophic, and transplanted dog samples. Microspectroscopy showed that dystrophic dog muscle displays higher and lower autofluorescence due to collagen cross-linking and NADH respectively than that of healthy and transplanted dogs, defining biomarkers to evaluate the impact of cell transplantation. Our findings demonstrate that DUV radiation is a sensitive, label-free method to assess the histopathological status of dystrophic muscle using small amounts of tissue, with potential applications in regenerative medicine. [ABSTRACT FROM AUTHOR]

The aim of the research was to investigate the effects of different stocking densities on fattening performance, slaughter, carcass, meat quality characteristics, and fatty acid composition in New Zealand rabbits raised in cage conditions and also determine the ideal housing frequency so that yields were not adversely affected. In the study, 36 New Zealand rabbits were used. After weaning, the fattening was started and rabbits were put into cages at different stocking densities as 1 rabbit/cage, 2 rabbits/cage, and 3 rabbits/cage. The live weight of rabbits and feed consumption data were taken every week. At the end of 8 weeks of fattening, slaughtering was carried out and slaughter weights of the rabbits were recorded. The internal organ weights and hot carcass weights were determined. After 24 h, chilled carcass weight and reference carcass weight were defined. As quality parameters of meat; pH, color, cooking loss, water holding capacity, drip loss, and fatty acid composition were determined. In the results of the study, 3 rabbits/cage group had the lowest final live weight (2353.60 g) and daily live weight gain (25.62 g) but 1 rabbit/cage group had the lowest feed conservation ratio (3.56) (p = 0.05). There were no significant differences in dressing out percentage, hot, chilled, and reference carcass weight. Head and hind part percentages were higher for 2 rabbits/cage and 3 rabbits/cage groups (p = 0.05). Stocking density had no relationship between meat quality and fatty acid composition data except b* value for the longissimus dorsi muscle measured at the 24th h and for the biceps femoris muscle measured at the 0th h (p = 0.05). In conclusion, 1 rabbit/cage and 2 rabbits/cage groups had better fattening performance values comparing the 3 rabbits/cage group because of movement area, social and hierarchical behavior between rabbits and advised for laboratory and commercial rabbit breeding for uniformity and profitability. [ABSTRACT FROM AUTHOR]

Diffusion‐tensor magnetic resonance imaging (DT‐MRI) offers objective measures of muscle characteristics, providing insights into age‐related changes. We used DT‐MRI to probe skeletal muscle microstructure and architecture in a large healthy‐aging cohort, with the aim of characterizing age‐related differences and comparing these to muscle strength. We recruited 94 participants (43 female; median age = 56, range = 22–89 years) and measured microstructure parameters—fractional anisotropy (FA) and mean diffusivity (MD)—in 12 thigh muscles, and architecture parameters—pennation angle, fascicle length, fiber curvature, and physiological cross‐sectional area (PCSA)—in the rectus femoris (RF) and biceps femoris longus (BFL). Knee extension and flexion torques were also measured for comparison to architecture measures. FA and MD were associated with age (β = 0.33, p = 0.001, R2 = 0.10; and β = −0.36, p < 0.001, R2 = 0.12), and FA was negatively associated with Type I fiber proportions from the literature (β = −0.70, p = 0.024, and R2 = 0.43). Pennation angle, fiber curvature, fascicle length, and PCSA were associated with age in the RF (β = −0.22, 0.26, −0.23, and −0.31, respectively; p < 0.05), while in the BFL only curvature and fascicle length were associated with age (β = 0.36, and −0.40, respectively; p < 0.001). In the RF, pennation angle and PCSA were associated with strength (β = 0.29, and 0.46, respectively; p < 0.01); in the BFL, only PCSA was associated with strength (β = 0.43; p < 0.001). Our results show skeletal muscle architectural changes with aging and intermuscular differences in the microstructure. DT‐MRI may prove useful for elucidating muscle changes in the early stages of sarcopenia and monitoring interventions aimed at preventing age‐associated microstructural changes in muscle that lead to functional impairment. [ABSTRACT FROM AUTHOR]

People with mild-to-moderate hip osteoarthritis (OA) exhibit hip muscle weakness, alterations in hip kinematics and kinetics and hip contact forces during gait compared to healthy controls. However, it is unclear if those with hip OA use different motor control strategies to coordinate the motion of the centre of mass (COM) during gait. Such information could provide further critical assessment of conservative management strategies implemented for people with hip OA. Do muscle contributions to the acceleration of the COM during walking differ between individuals with mild-to-moderate hip OA and controls? Eleven individuals with mild-to-moderate hip OA and 10 healthy controls walked at a self-selected speed while whole-body motion and ground reaction forces were measured. Muscle forces during gait were obtained using static optimisation and an induced acceleration analysis was performed to determine individual muscle contributions to the acceleration of the COM during single-leg stance (SLS). Between-group comparisons were made using independent t-tests via Statistical Parametric Modelling. There were no between-group differences in spatial-temporal gait parameters or three-dimensional whole-body COM acceleration. The rectus femoris, biceps femoris, iliopsoas and gastrocnemius muscles in the hip OA group contributed less to the fore-aft accelerations of the COM (p < 0.05), and more to the vertical COM acceleration with the gluteus maximus (p < 0.05), during SLS, compared to the control group. Subtle differences exist in the way people with mild-to-moderate hip OA use their muscles to accelerate the whole-body centre of mass during the SLS phase of walking relative to healthy controls. These findings improve understanding of the complex functional consequences of hip OA and enhance our understanding of how to monitor the effectiveness of an intervention on biomechanical changes in gait in people with hip OA. • Individuals with mild to moderate hip OA use different muscle lower limb coordination strategies. • Differing coordination during gait may be a response to neuromuscular deficits such as strength. • Interventions targeting muscles associated with altered patterns of muscle coordination may be warranted. [ABSTRACT FROM AUTHOR]

Measuring muscle quantity and quality is very important because the loss of muscle quantity and quality is associated with several adverse effects specifically in older people. Ultrasound is a method widely used to measure muscle quantity and quality. One problem with ultrasound is its limited field of view, which makes it impossible to measure the muscle quantity and quality of certain muscles. In this study, we aimed to evaluate the intra- and inter-rater reliability of extended-field-of-view (EFOV) ultrasound for the measurement of muscle quantity and quality in nine muscles of the limbs and trunk. Two examiners took two ultrasound EFOV images with a linear probe from each of the muscle sites. The intraclass correlation coefficient (ICC) was used, and the standard error of measurement and coefficient of variation were calculated. Intra-rater reliability was good to excellent (ICC = 0.2–1.00) for all muscle measurements. The inter-rater reliability for most of the muscle measurements was good to excellent (ICC = 0.82–0.98). Inter-rater reliability was moderate (0.58–0.72) for some muscle quantity measurements of the tibialis anterior, gastrocnemius, rectus femoris, biceps femoris and triceps brachii muscles. Muscle quantity and quality can be measured reliably using EFOV US. [ABSTRACT FROM AUTHOR]

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Purpose: To analyze the muscle activation of the rectus femoris (RF), vastus lateralis (VL), gluteus maximus (GM), and biceps femoris (BF) in concentric and eccentric actions in the squat at 90° and 140° range of motion. Methods: Thirty-five women (32.9 ± 7.4 years; 64.5 ± 11.5 kg; 1.63 ± 0.1 m; BMI: 24.2 ± 2.9 kg/m2; %fat: 24.9 ± 6.5%) experienced exercise for at least eight weeks. Electrodes were positioned in standardized locations. The signals were acquired by an A/D SAS1000 V8 converter and the electromyographic activity normalized in the percentage of the highest produced value (%RMS). The data were analyzed using repeated measures two-way ANOVA, with effect size (η2) and differences calculated in percentage points (∆ p.p.). Results: The RF (p = 0.001; ∆ = 5.1 p.p.) and BF activation (p = 0.020; ∆ = 4.0 p.p.) was higher at 90° in the eccentric action. The RF showed an interaction between the range of motion and %RMS, with a large effect size (F = 37.9; p = 0.001; η2 = 0.485). The VL activation was higher at 140° (p = 0.005; ∆ = 3.9 p.p.) in the concentric action and higher at 90° (p = 0.006; ∆ = 3.7 p.p.) in the eccentric action, with a large effect size significant interaction (F = 21.3; p = 0.001; η2 = 0.485). The GM activation was higher at 90° in the concentric (p = 0.020; ∆ = 5.4 p.p.) and eccentric action (p = 0.022; ∆ = 41 p.p.). Conclusions: The biarticular muscles were influenced by the squat range only in the eccentric action of the movement, while the monoarticular muscles were influenced by the squat in both concentric and eccentric muscle action.

Hamstring injuries are among the most common muscle injuries. They have been reported in many different sports, such as running, soccer, track and field, rugby, and waterskiing. However, they are also present among the general population. Most hamstring injuries are mild strains, but also moderate and severe injuries occur. Hamstring injuries usually occur in rapid movements involving eccentric demands of the posterior thigh. Sprinting has been found to mainly affect the isolated proximal biceps femoris, whereas stretching-type injuries most often involve an isolated proximal injury of the semimembranosus muscle. The main cause of severe 2- or 3-tendon avulsion is a rapid forceful hip flexion with the ipsilateral knee extended. Most hamstring injuries are treated non-surgically with good results. However, there are also clear indications for surgical treatment, such as severe 2- or 3-tendon avulsions. In athletes, more aggressive recommendations concerning surgical treatment can be found. For a professional athlete, a proximal isolated tendon avulsion with clear retraction should be treated operatively regardless of the injured tendon. Surgical treatment has been found to have good results in severe injuries, especially if the avulsion injury is repaired in acute phase. In chronic hamstring injuries and recurring ruptures, the anatomical apposition of the retracted muscles is more difficult to be achieved. This review article analyses the outcomes of surgical treatment of hamstring ruptures. The present study confirms the previous knowledge that surgical treatment of hamstring tendon injuries causes good results with high satisfaction rates, both in complete and partial avulsions. Early surgical repair leads to better functional results with lower complication rates, especially in complete avulsions.KEY MESSAGEsSurgical treatment of hamstring tendon ruptures leads to high satisfaction and return to sport rates.Both complete and partial hamstring tendon ruptures have better results after acute surgical repair, when compared to cases treated surgically later.Athletes with hamstring tendon ruptures should be treated more aggressively with operative methods.

Introduction: Aging of skeletal muscles results in a cascade of events negatively affecting muscle mass, strength, and function, leading to reduced mobility, increased risk of falls, disability, and loss of independence. To date, different methods are used to assess muscle mechanical function, tensiomyography (TMG) being one of them. The aim of this review was twofold: to summarize the evidence-based usefulness of tensiomyography in older adults and to establish reference values for the main tensiomyography parameters in older adults. Methods: The PubMed, Web of Science, SPORTDiscus, and tensiomyography databases were searched from inception until 25 December 2022. Studies investigating older adults (aged 60+ years) that reported tensiomyographyderived parameters such as contraction time (Tc) and/or maximal displacement (Dm) were included. Methodological quality was assessed using the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies. Results: In total, eight studies satisfied the inclusion criteria. Tensiomyography has been used on different groups of older adults, including asymptomatic, master athletes, patients with peripheral arterial disease, and patients with end-stage knee osteoarthritis with a mean age of 71.5 ± 5.38 (55.7% male subjects). The most evaluated were leg muscles such as vastus lateralis (VL), gastrocnemius medialis (GM), and biceps femoris (BF). The present review demonstrates that tensiomyography is used to assess neuromuscular function in asymptomatic and diseased older adults. When compared to asymptomatic individuals, power master athletes, knee osteoarthritis patients, and patients diagnosed with peripheral arterial disease have the shortest Tc in BF, VL, and GM muscles, respectively. On the other hand, endurance master athletes showed the longest Tc in all three evaluated muscles. Less mobile, nursing-home residents showed higher Dm in VL and BF, while lower Dm in GM than the asymptomatic group. The knee osteoarthritis group showed the largest Dm in BF and VL while having the smallest Dm in GM. Conclusion: Tensiomyography can serve as a valuable tool for assessing neuromuscular function in older adults. The method is sensitive to muscle composition, architecture, and (pre) atrophic changes of the skeletal muscles and might be responsive to muscle quality changes in aging and diseased populations. [ABSTRACT FROM AUTHOR]

Background: The hamstrings are an important muscle group that contribute to horizontal force during sprint acceleration and are also the most injured muscle group in running-based sports. Given the significant time loss associated with hamstrings injury and impaired sprinting performance following return to sport, identifying exercises that drive adaptations that are both protective of strain injury and beneficial to sprint performance is important for the strength and conditioning professional. This paper describes the study protocol investigating the effects of a 6-week training program using either the hip-dominant Romanian deadlift (RDL) or the knee-dominant Nordic hamstring exercise (NHE) on hamstring strain injury risk factors and sprint performance. Methods: A permuted block randomized (1:1 allocation) intervention trial will be conducted involving young, physically-active men and women. A target sample size of 32 will be recruited and enrolled participants will undergo baseline testing involving extended-field-of-view ultrasound imaging and shear wave elastography of the biceps femoris long head muscle, maximal hamstrings strength testing in both the RDL and NHE, and on-field sprint performance and biomechanics. Participants will complete the 6-week training intervention using either the RDL or NHE, according to group allocation. Baseline testing will be repeated at the end of the 6-week intervention followed by 2 weeks of detraining and a final testing session. The primary outcome will be regional changes in fascicle length with secondary outcomes including pennation angle, muscle cross sectional area, hamstring strength, and maximal sprint performance and biomechanics. An exploratory aim will determine changes in shear wave velocity. Discussion: Despite extensive research showing the benefits of the NHE on reducing hamstring strain injury risk, alternative exercises, such as the RDL, may offer similar or potentially even greater benefits. The findings of this study will aim to inform future researchers and practitioners investigating alternatives to the NHE, such as the RDL, in terms of their effectiveness in reducing rates of hamstring strain injury in larger scale prospective intervention studies. Trial Registration: The trial is prospectively registered on ClinicalTrials.gov (NCT05455346; July 15, 2022). [ABSTRACT FROM AUTHOR]

Introduction: This study investigated kinematic and EMG changes in gait across simulated gravitational unloading levels between 100% and 20% of normal body weight. This study sought to identify if each level of unloading elicited consistent changes—particular to that percentage of normal body weight—or if the changes seen with unloading could be influenced by the previous level(s) of unloading. Methods: 15 healthy adult participants (26.3 ± 2.5 years; 53% female) walked in an Alter-G anti-gravity treadmill unloading system (mean speed: 1.49 ± 0.37 mph) for 1 min each at 100%, 80%, 60%, 40% and 20% of normal body weight, before loading back to 100% in reverse order. Lower-body kinematic data were captured by inertial measurement units, and EMG data were collected from the rectus femoris, biceps femoris, medial gastrocnemius, and anterior tibialis. Data were compared across like levels of load using repeated measures ANOVA and statistical parametric mapping. Difference waveforms for adjacent levels were created to examine the rate of change between different unloading levels. Results: This study found hip, knee, and ankle kinematics as well as activity in the rectus femoris, and medial gastrocnemius were significantly different at the same level of unloading, having arrived from a higher, or lower level of unloading. There were no significant changes in the kinematic difference waveforms, however the waveform representing the change in EMG between 100% and 80% load was significantly different from all other levels. Discussion: This study found that body weight unloading from 100% to 20% elicited distinct responses in the medial gastrocnemius, as well as partly in the rectus femoris. Hip, knee, and ankle kinematics were also affected differentially by loading and unloading, especially at 40% of normal body weight. These findings suggest the previous level of gravitational load is an important factor to consider in determining kinematic and EMG responses to the current level during loading and unloading below standard g. Similarly, the rate of change in kinematics from 100% to 20% appears to be linear, while the rate of change in EMG was non-linear. This is of particular interest, as it suggests that kinematic and EMG measures decouple with unloading and may react to unloading uniquely. [ABSTRACT FROM AUTHOR]

The objective of the study was to determine the effects of sex and hunting season on the carcass, meat and fat quality of hunted brown hares (Lepus europaeus). Twenty-two hares of both sexes hunted in winter (December) during two hunting seasons in accordance with the law on hunting in Lithuania were evaluated using reference methods The data were subjected to two-factor analysis of variance in the general linear (GLM) procedure. No significant differences in carcass measurements and muscularity or internal organs between the sexes of brown hares were found; however, the hunting season appeared to affect the size of hares. The biceps femoris (BF) thigh muscle of males had lower (p < 0.05) dry matter content and higher (p < 0.05) drip loss compared with females. The hunting season demonstrated an effect (p < 0.001) on protein and hydroxyproline contents in the longissimus thoracis et lumborum (LTL) and affected dry matter, protein and hydroxyproline contents (p < 0.05, p < 0.001 and p < 0.01, respectively) in BF muscles, and differences in the colour of muscles were also observed. The shear force in the Warner–Bratzler (WB) test was higher (p < 0.001 and p < 0.01, respectively) for LTL and BF muscles during the first hunting season. The hunting season did not affect the total SFA in the intramuscular fat (IMF) of all the tissues, but it affected levels of monounsaturated (MUFA) and polyunsaturated (PUFA) fatty acids in the muscles. No differences were found in the total saturated fatty acids (SFA) of both muscles between the sexes, but females demonstrated lower (p < 0.05 and p < 0.01, respectively) and more favourable n-6/n-3 PUFA ratios in the muscles and fat and a lower (p < 0.05) thrombogenic (TI) index in the LTL compared with males. [ABSTRACT FROM AUTHOR]

Introduction: Originally developed for astronauts, lower body positive pressure treadmills (LBPPTs) are increasingly being used in sports and clinical settings because they allow for unweighted running. However, the neuromuscular adjustments to unweighted running remain understudied. They would be limited for certain lower limb muscles and interindividually variable. This study investigated whether this might be related to familiarization and/or trait anxiety. Methods: Forty healthy male runners were divided into two equal groups with contrasting levels of trait anxiety (high, ANX+, n = 20 vs. low, ANX-, n = 20). They completed two 9-min runs on a LBPPT. Each included three consecutive 3-min conditions performed at 100%, 60% (unweighted running), and 100% body weight. Normal ground reaction force and electromyographic activity of 11 ipsilateral lower limb muscles were analyzed for the last 30 s of each condition in both runs. Results: Unweighted running showed muscle- and stretch-shortening cycle phase-dependent neuromuscular adjustments that were repeatable across both runs. Importantly, hamstring (BF, biceps femoris; STSM, semitendinosus/ semimembranosus) muscle activity increased during the braking (BF: +44 ± 18%, p < 0.001) and push-off (BF: +49 ± 12% and STSM: +123 ± 14%, p < 0.001 for both) phases, and even more so for ANX+ than for ANX-. During the braking phase, only ANX+ showed significant increases in BF (+41 ± 15%, p < 0.001) and STSM (+53 ± 27%, p < 0.001) activities. During the push-off phase, ANX+ showed a more than twofold increase in STSM activity compared to ANX- (+119 ± 10% vs. +48 ± 27, p < 0.001 for both). Conclusion: The increase in hamstring activity during the braking and push-off phases may have accelerated the subsequent swing of the free-leg, likely counteracting the unweighting-induced slowing of stride frequency. This was even more pronounced in ANX+ than in ANX-, in an increased attempt not to deviate from their preferred running pattern. These results highlight the importance of individualizing LBPPT training and rehabilitation protocols, with particular attention to individuals with weak or injured hamstrings. [ABSTRACT FROM AUTHOR]

Athletic women have shown a higher risk of ACL injury during jump landing compared to men. Plyometric training can be an alternative way to minimize the risk of knee injuries via the changed muscle activity patterns. Hence, the aim of this study was to determine the effects of a 4-week plyometric training program on the muscle activity pattern in different phases of one-leg drop jump in active girls. Active girls were randomly allocated into 2 groups (Plyometric training = 10, Control group = 10) where the plyometric training group (PTG) performed 60 min exercises, 2 sessions/1 week for 4 weeks while the control group (CG) had their daily activity. In the pre to post test, the sEMG was recorded from the Rectus Femoris (RF), Biceps Femoris (BF), Medial Gastrocnemius (GaM), and Tibialis Anterior (TA) muscles of the dominant leg during the Preparatory phase (PP), Contact Phase (CP), Flight Phase (FP) of one-leg drop jump. Electromyography variables (Signal amplitude, Maximum activity, Time to peak (TTP), Onset and activity time and Order muscle activity) and Ergo jump variables (Time of preparatory phase (TPP), Time of contact phase (TCP), Time of flight (jump height) phase (TFP), and Explosive power were analyzed. The Univariate ANCOVA test showed a significant difference between the two groups in Activity Time, whilst adjusting for pre-test as a Covariate, only in TA muscle (F(1,17) = 5.09, p = 0.038, η2 = 0.230). In PTG. TA (− 15%), GaM (− 19%), and BF muscles (− 9%) started their activity earlier while there was no significant difference between the two groups at the Onset time. TTP of RF was significantly different between the 2 groups only in the PR phase (0.216 ± 0.07 vs 0.153 ± 0.09 s) (p = 0.049, 95% CI = 0.001, 0.127). Results of the present study suggest that a 4-week plyometric training can improve the stability of leg joints via earlier recruitment of muscles and change activity patterns in lower limb muscles. It also recommends that the preparatory phase before landing be considered an important stage in preventing sports injuries in a training program. [ABSTRACT FROM AUTHOR]

The aim of the study was to analyze muscle activation in the three positions of the deadlift (DL). Twenty male participants (33.4 ± 3.9 years; 42.2 ± 9.1 months of experience with DL; 91.0 ± 14.8 kg; and 1.78 ± 0.06 m) pulled a bar through isometric actions in three DL positions: lift-off, mid-pull, and lockout. Isometric strength, knee angle, and activation of the rectus femoris (RF), biceps femoris (BF), lateral gastrocnemius (GAL), and erector spinae (ERE) muscles were collected. The analysis of variance showed that the maximum isometric force presented differences between the positions (p = 0.001; η2 = 0.973) considered large with higher values at the mid-pull position. Interactions were found between muscles and position (p = 0.001; η2 = 0.527) considered large. The RF and ERE showed greater activation in the lift-off position, while in the mid-pull position, there was greater activation of the BF and GAL muscles. The DL positions produce different activations in the bi-articular and uni-articular muscles. The lift-off requires more activation from the RF and ERE positions. The mid-pull position, despite generating greater force, presented greater activations in the BF and GAL. The ERE showed higher activations as the external torque was greater. [ABSTRACT FROM AUTHOR]

Background: This study aimed to derive the effects of walking while using a mobile phone on balance perturbation and joint movement among young adults. Methods: Sixteen healthy college students with no history of brain injury were tested. The participants were asked to walk under four different conditions: (1) walking, (2) browsing, (3) dialing, and (4) texting. Indicators related to balance control and lower limb kinematic/kinetic parameters were analyzed using the continuous relative phase and statistical nonparametric mapping methods. Results: Walking while using a mobile phone slowed participants' gait speed and reduced the cadence, stride length, and step length. The posterior tilt angle (0–14%, 57–99%), torque of the hip flexion (0–15%, 30–35%, 75–100%), and angle of the hip flexion (0–28%, 44–100%) decreased significantly. The activation of biceps femoris and gastrocnemius, hip stiffness, and ankle stiffness increased significantly. This impact on gait significantly differed among three dual tasks: texting > browsing > dialing. Conclusion: Che overlap of walking and mobile phone use affects the gait significantly. The "hip–ankle strategy" may result in a "smooth" but slower gait, while this strategy was deliberate and tense. In addition, this adjustment also increases the stiffness of the hip and ankle, increasing the risk of fatigue. Findings regarding this effect may prove that even for young healthy adults, walking with mobile phone use induces measurable adjustment of the motor pattern. These results suggest the importance of simplifying the control of the movement. [ABSTRACT FROM AUTHOR]

The validity and reliability of 3-D ultrasound (US) in estimation of muscle and tendon volume was assessed in a very limited number of muscles that can be easily immersed. The objective of the present study was to assess the validity and reliability of muscle volume measurements for all hamstring muscle heads and gracilis (GR), as well as tendon volume for the semitendinosus (ST) and GR using freehand 3-D US. Three-dimensional US acquisitions were performed for 13 participants in two distinct sessions on separate days, in addition to one session dedicated to magnetic resonance imaging (MRI). Volumes of ST, semimembranosus (SM), biceps femoris short (BFsh) and long (BFlh) heads, and GR muscles and from the tendon from semitendinosus (STtd) and gracilis (GRtd) were collected. The bias and the 95% confidence intervals of 3-D US compared with MRI ranged from –1.9 mL (–0.8%) to 1.2 mL (1.0%) for muscle volume and from 0.01 mL (0.2%) to –0.03 mL (–2.6%) for tendon volume. For muscle volume assessed using 3-D US, intraclass correlation coefficients (ICCs) ranged from 0.98 (GR) to 1.00, and coefficients of variation (CV) from 1.1% (SM) to 3.4% (BFsh). For tendon volume, ICCs were 0.99, and CVs between 3.2% (STtd) and 3.4% (GRtd). Three-dimensional US can provide a valid and reliable inter-day measurement of hamstrings and GR for both muscle and tendon volumes. In the future, this technique could be used as an outcome for strengthening interventions and potentially in clinical environments. [ABSTRACT FROM AUTHOR]

Exoskeletons potentially reduce physical strain on workers. However, studies investigating the long-term effects of exoskeletons in the workplace are rare, not least because demonstrating physical long-term impacts faces several challenges, including the collection of reliable biomechanical data with the exoskeleton. By examining the potential impact of using an exoskeleton on inter-day measurements, we can provide valuable insights into the suitability of long-term studies. Therefore, this study aims to investigate the inter-day variation in muscle activity (MA) and kinematics of the trunk and legs during lifting, carrying, walking, and static bending with and without a passive back exoskeleton. The majority of results show no significant differences in inter-day variation. However, we found minor significant unilateral variation in knee and ankle kinematics when using the BSE during the lifting, carrying, and walking tasks, as well as in MA of M. biceps femoris when measuring without the BSE during the lifting tasks. Cohen's d showed small effect sizes, ranging from −0.0045 ≤ d ≤ 0.384 for all significant p-values. While we classify the observed significant differences as minor, it is still crucial to consider day-to-day variations in long-term studies. However, by implementing high levels of standardization in study designs, including precise exoskeleton fitting, consistent assistance level, familiarization with measurement systems, and standardized working tasks, the impact of the exoskeleton on inter-day measurements can be minimized. Additional field studies are necessary to validate our findings in real work conditions. [ABSTRACT FROM AUTHOR]

Background: The reaching-transporting task as an essential daily activity impacts balance control and falling in older women. This study investigated the different muscle strategies during the head/knee level of the functional reaching-transporting task in postmenopausal women with osteoporosis. Methods: 24 postmenopausal volunteers were classified into two groups based on the lumbar T-score: osteoporosis (≤ -2.5, n = 12) and non-osteoporosis (> –1, n = 12). Using a custom-designed device, participants randomly performed 12 reaching-transporting tasks at the head and knee levels. Electromyography signals were collected while reaching and transporting phases with a wireless system. The peak of the root means square (PRMS) and time to PRMS (TPRMS) were measured. In addition, the isometric muscle strength and the fear of falling were assessed. Results: The isometric muscle strength in the osteoporotic group was significantly lower than in the non-osteoporotic group (P < 0.05), except for vastus lateralis (VL). The PRMS of VL, (P = 0.010) during the reaching phase and VL (P = 0.002) and gastrocnemius lateralis (GL) (P < 0.001) during transporting phase was greater than the non-osteoporotic group. The PRMS value of the muscles was greater for reaching-transporting at the knee level than the head level; this increase was significant just for VL and biceps femoris during the transporting phase (P = 0.036 and P = 0.004, respectively). Conclusion: Osteoporotic women have more muscle activities during the reaching-transporting task, especially at the knee level, compared to the head level. Their muscle weakness may lead to insufficient stability during the task and cause disturbance and falling, which requires further investigation. [ABSTRACT FROM AUTHOR]

We investigated the coordinated activity patterns of muscles based on cosine tuning in the elderly during an isometric force exertion task. We also clarified whether these coordinated activity patterns contribute to the control of hip and knee joint torque and endpoint force as co-activation. Preferred direction (PD) of activity for each muscle in 10 young and 8 older males was calculated from the lower limb muscle activity during isometric force exertion task in various directions. The covariance of endpoint force (η) was calculated from the exerted force data using a force sensor. Relationship between PD and η was used to examine the effect of muscle co-activation on the control of endpoint force. Co-activation between rectus femoris and semitendinosus/biceps femoris increased with changes in muscle PD. Additionally, the η values were significantly low, suggesting that co-activation of multiple muscles may contribute to endpoint force exertion. The mechanism for cooperative muscle activity is determined by the cosine tuning of the PD of each muscle, which affects the generation of hip and knee joint torque and endpoint force exertion. Co-activation of each muscle's PD changes with age, causing increased muscle co-activation to control torque and force. We demonstrated that co-activation in the elderly is a stabilizer of unsteady joints and a muscle control strategy for cooperative muscle activity. [ABSTRACT FROM AUTHOR]

Fluoroscopy guidance is commonly utilized for injections in the upper extremity, with increased accuracy for injection placement compared to blind injection. Injection of the glenohumeral joint is the most commonly performed upper extremity procedure. However, there are a number of other sites which can be easily injected under fluoroscopy including the acromioclavicular joint, subacromial subdeltoid bursa, biceps tendon sheath, scapulothoracic bursa, elbow, wrist, first CMC joint, and pisotriquetral joint. Fluoroscopy can be used to guide injections into the glenohumeral, elbow, or wrist joints preceding MR arthrography. While there are technique similarities when injecting any of these sites, some particular approaches and pitfalls are unique to each anatomic site. [ABSTRACT FROM AUTHOR]

The objective of the study was to investigate the effect of leg supports on the anticipatory and compensatory postural adjustments of sitting subjects exposed to external perturbations in the anterior-posterior direction. Ten young participants received perturbations applied to the upper body while sitting on a stool with an anterior or posterior leg support and when using a footrest. Electromyographic activities of the trunk and leg muscles and center of pressure displacements were recorded and analyzed during the anticipatory and compensatory phases of postural control. Anticipatory activities were observed in the tibialis anterior, biceps femoris, and erector spinae muscles in the anterior leg support condition. Early onset of muscle activity was observed in the tibialis anterior, biceps femoris, rectus femoris, and erector spinae muscles in the posterior leg support condition compared to the feet support condition. Moreover, to maintain balance participants utilized co-contraction of muscles as the main mechanism of balance control in sitting regardless of the availability of the anterior or posterior leg support. There was no effect of a leg support on center of pressure displacements. The outcome of the study provides a background for future investigations of the effect of leg supports on control of balance in sitting when perturbed. [ABSTRACT FROM AUTHOR]

Metabolic syndrome is an epidemic of non-infectious origin, which is associated with the consumption of a large amount of high-calorie food and a sedentary lifestyle. It is not excluded that bacterial lipopolysaccharides (LPS) may enter the body during metabolic syndrome. The purpose of this work is to study the combined effect of bacterial lipopolysaccharide and high fructose diet on the concentration of glycosaminoglycans and their individual fractions, the content of free L-oxyproline and sialic acids in rat biceps femoris muscle. Bacterial LPS was injected intraperitoneally at a dose of 0.4 μg/kg. Metabolic syndrome was modelled by using 20% fructose solution as only source of drinking water. In the test group of animals total concentration of glycosaminoglycans increased by 22.53%, the heparin-heparan and keratan-dermatan fraction concentrations raised by 26.18 and 35.91%, but concentration of the chondroitin fraction did not change compared to the control. The concentrations of free L-oxyproline and sialic acids increased by 120.71 and 156.78%, respectively. Thus, high fructose diet, stimulation of the organism with bacterial lipopolysaccharide and their combination lead to increased degradation of glycoproteins and proteoglycans and intensify collagenolysis in the biceps femoris muscle of rats. [ABSTRACT FROM AUTHOR]

Human standing is the anatomical and functional framework for independent movement. The study of weight bearing during standing and movement is crucial to support the development of technology aimed at restoring independent gait, where unsupported weight bearing is still elusive. This study aims to determine muscle and spinal activation at different gravitational loads in young, healthy individuals to provide potential patterns of spinal stimulation for standing. Muscle activity was recorded with surface electromyography (EMG) from 18 healthy participants at different body angles while on a motorised plinth. The body angles tested and the relative gravitational loadings were: 0 deg (supine) corresponding to ~0% of total body weight (BW), 15 deg (~26% BW), 30 deg (~50% BW), 45 deg (~71% BW), 60 deg (~87% BW), 75 deg (~97% BW), upright on and off the plinth (~100% BW). The muscles recorded were soleus, gastrocnemius medialis and lateralis, tibialis anterior, adductor longus, peroneus longus, vastus medialis and lateralis, rectus femoris, sartorius, extensor digitorum longus, semimembranosus, semitendinosus, biceps femoris, gracilis, rectus abdominis, external oblique, erector spinae and latissimus dorsi. From the recorded muscle activity, spinal activation maps were calculated. Despite high variability in EMG data, the group muscle activity changed with body angle. Vastus lateralis became activated at 60 deg (~87% BW), soleus became activated at 75 deg, and the gastrocnemii at 90 deg. The spinal segments that showed significant differences in mean activation between angles were the fifth lumbar L5 and the first sacral S1 segments. The data from this study suggest that weight‐bearing independent standing could be achieved with increased activation of a limited number of superficial muscles tested, and 87% BW is a critical loading for increased muscle activation compared to the supine position. The spinal activation in the lower lumbar and sacral segments shows the involvement of these regions in maintaining weight‐bearing standing. By reproducing this pattern of muscle and spinal segment activity through tonic stimulation, we speculate that restoration of independent standing and walking may be possible for patients following spinal cord injuries. [ABSTRACT FROM AUTHOR]

This study was aimed at determining the effects of dietary supplementation with thyme essential oil (TEO) and rosemary essential oil (REO) on blood parameters, the anti-oxidant metabolism in the liver, breast and drumstick muscle tissues, the morphology of the small intestine, and the myofibril structure of the superficial pectoral and biceps femoris muscles. For this purpose, 400 three-day-old male Ross 308 chicks were used. Five groups, each comprising 80 broilers, were established. The control group was fed on a basal diet alone and groups thyme-1, thyme-2, rosemary-1 and rosemary-2 received basal diets supplemented with 0.15 g kg-1 of TEO, 0.30 g kg-1 of TEO, 0.10 g kg-1 of REO and 0.20 g kg-1 of REO, respectively. The serum total cholesterol and low-density lipoprotein levels were decreased significantly in group thyme-1. Dietary TEO and REO significantly increased glutathione levels in all tissues. Drumstick catalase activity was significantly increased in groups thyme-1, thyme-2 and rosemary-2. Superoxide dismutase activity was significantly increased in the breast muscle of all groups that received dietary TEO and REO. Histomorphometrical analyses demonstrated that dietary supplementation with TEO and REO increased both crypt depth and villus height in the small intestine. In result, the tested doses of dietary TEO and REO were ascertained to improve the intestinal morphology and to increase the anti-oxidant metabolism mainly in the breast muscle, the drumstick muscle and liver. [ABSTRACT FROM AUTHOR]

Eccentric hamstring strength training is a common training method applied in sport settings due to it being largest driver for increasing BFLH fascicle length compared to other contraction modes (3). This is important given that for every 1cm increase in fascicle length, the probability of sustaining a future HSI is reduced by 21% reduction (16). Additionally, those with shorter BFLH fascicle length (<10.56cm) have a 4.41x greater risk of sustaining a future HSI (16). Therefore, the purpose of this review is to identify the time course for detraining to occur in the BFLH following a period of eccentric strength training in the hamstrings. A search of the literature was conducted of the following electronic databases; CINAHL, MEDLINE, Google Scholar and SPORTDiscus. This search was conducted for; biceps femoris long head, fascicle length, eccentric training, flywheel, and detraining. After this search 8 papers were selected to form the basis of this review. BFLH fascicle length was found to increase significantly within 2-6weeks following eccentric hamstring training. The earliest identified significant increase occurring at 2-weeks following high-volume eccentrics (48-repetitions per week). After the application of an eccentric stimulus, when a period of detraining is applied, fascicle lengths can detrain in 1-week and return to baseline in as quickly as 2-weeks. Therefore, continued exposure to eccentric contraction in the hamstrings is a key factor to maintaining BFLH fascicle length adaptations. In applied settings where HSI risk is high, weekly low-dose eccentric hamstring training of 8-repetitons are recommended for inclusion in all HSI prevention programs following 2-weeks of high-volume training. This is to ensure these adaptations to the BFLH fascicle length are not lost. [ABSTRACT FROM AUTHOR]

Law enforcement officers (LEOs) commonly wear a duty belt (DB) or tactical vest (TV) and from prior findings, these forms of load carriage (LC) likely alter muscular activity. However, studies on the effects of LEO LC on muscular activity and coordination are limited in the current literature. The present study examined the effects of LEO load carriage on muscular activity and coordination. Twenty-four volunteers participated in the study (male = 13, age = 24.5 ± 6.0 years). Surface electromyography (sEMG) sensors were placed on the vastus lateralis, biceps femoris, multifidus, and lower rectus abdominus. Participants completed treadmill walking for two load carriage conditions (duty belt and tactical vest) and a control condition. Mean activity, sample entropy and Pearson correlation coefficients were computed for each muscle pair during the trials. The duty belt and tactical vest resulted in an increase in muscle activity in several muscles; however, no differences between the duty belt and tactical vest were found. Consistently across the conditions, the largest correlations were observed between the left and right multifidus (r = 0.33–0.68) and rectus abdominus muscles (0.34–0.55). There were statistically small effects (p < 0.05, η2 = 0.031 to 0.076) of the LC on intermuscular coordination. No effect (p > 0.05) of the LC on sample entropy was found for any muscle. The findings indicate that LEO LC causes small differences in muscular activity and coordination during walking. Future research should incorporate heavier loads and longer durations. [ABSTRACT FROM AUTHOR]

Piglets are susceptible to cold, and piglet death caused by cold stress leads to economic losses in the pig industry in cold areas. Skeletal muscle plays a key role in adaptive thermogenesis in mammals, but the related mechanism in pigs is unclear. In this study, cold-tolerant Tibetan pigs and cold-sensitive Bama pigs were subjected to either a cold environment (4 °C) or a room temperature environment (25 °C) for 3 days. The biceps femoris (BF) and longissimus dorsi muscle (LDM) were collected for phenotypic analysis, and the BF was used for genome-wide transcriptional profiling. Our results showed that Tibetan pigs had a higher body temperature than Bama pigs upon cold stimulation. RNA-seq data indicated a stronger transcriptional response in the skeletal muscle of Tibetan pigs upon cold stimulation, as more differentially expressed genes (DEGs) were identified with the same criteria (p < 0.05 and fold change > 2). In addition, distinct pathway signaling patterns in skeletal muscle upon cold exposure were found between the breeds of pigs. Mitochondrial beta-oxidation-related genes and pathways were significantly upregulated in Tibetan pigs, indicating that Tibetan pigs may use fatty acids as the primary fuel source to protect against cold. However, the significant upregulation of inflammatory response- and glycolysis-related genes and pathways in the skeletal muscle of Bama pigs suggested that these pigs may use glucose as the primary fuel source in cold environments. Together, our study revealed the distinct transcriptional responses of skeletal muscle to cold stimulation in Tibetan pigs and Bama pigs and provided novel insights for future investigation of the cold adaptation mechanism in pigs. [ABSTRACT FROM AUTHOR]

The purpose of this study was to compare changes in muscle pre-activation and short-latency responses in the lower limbs during drop jumps performed on different common soft and hard surfaces and at various platform heights. The study aimed to collect electromyography data from the rectus femoris, biceps femoris, tibialis anterior, gastrocnemius, and soleus of the dominant leg during drop jumps on sand, turf, polyurethane, and wood surfaces from platform heights of 30, 40, 50, and 60 cm. Muscle pre-activation refers to muscle activity 100 ms before ground contact during a drop jump, while short-latency responses refer to muscle activation occurring 30–60 ms after ground contact. These definitions were used to measure and analyze neuromuscular responses in the lower limb muscles during drop jumps using various surfaces and platform heights. Sand as a ground material and platform heights of 50 and 60 cm significantly enhanced pre-activation and activation in short-latency responses of the lower limb muscles (all p < 0.01). The difficulty of the drop jump task can enhance pre-activation and activation in the latency responses of lower limb muscles. It is recommended that athletes perform drop jumps on sandy surfaces or from platforms higher than 50 cm to induce muscle pre-activation of the lower limbs and to improve muscle activation levels in the latency responses after landing. [ABSTRACT FROM AUTHOR]

Purpose: Hamstring strain injuries may occur due to differential fatigue and compromised mechanical properties among the hamstring muscles. We examined (1) the effect of fatigue on hamstrings active muscle stiffness, and (2) whether contraction type affects active muscle stiffness changes during a submaximal fatiguing task. Methods: Nine healthy males completed 99 submaximal knee flexions in isometric (ISO), concentric (CON), and eccentric (ECC) conditions. We measured the knee flexor maximal voluntary torque (MVT) (pre/post), shear wave velocity (SWV) during contraction and transverse relaxation times (T2) (pre/post) in biceps femoris long head (BFlh), semitendinosus (ST), and semimembranosus (SM) muscles. Results: MVT decreased substantially after all conditions (− 18.4 to − 33.6%). The average relative torque sustained during the task was lower in CON than ISO and ECC, but absolute torque was similar. SWV interindividual responses were highly variable across muscles and contraction types. On average, BFlh SWV tended to increase in ISO (0.4 m/s, 4.5%, p = 0.064) but decreased in ECC condition (− 0.8 m/s, − 7.7%, p < 0.01). ST SWV decreased in CON (− 1.1 m/s, − 9.0%, p < 0.01), while it remained unchanged in ISO and ECC. SM SWV decreased in CON (− 0.8 m/s, − 8.1%, p < 0.01), but it was unaffected in ISO and variable in ECC. Conclusion: Fatigue has a differential effect on the mechanical properties of the constituent hamstring muscles, as measured with shear wave elastography, depending upon contraction type. We found preliminary evidence that BFlh is more fatigued than ST or SM during eccentric contractions, which may explain its susceptibility to strain injuries. [ABSTRACT FROM AUTHOR]

This study examined the effects of fatigue on hamstring muscles and gluteus maximus passive and active shear modulus in hip extension (HE) and knee flexion (KF) at 20% of maximal voluntary isometric contraction performed until task failure. Measurements were taken before and after the fatigue tasks and the delta (post-pre) was calculated. No differences in the fatigue effects on passive shear modulus were seen between muscles nor between tasks. For the active shear modulus: a task × muscle interaction was seen (p = 0.002; η2 p = 0.401). The results for the tasks separately demonstrated only a significant effect for muscle in KF (p < 0.001; η2 p = 0.598), with different individual contributions identified between BFlh-SM (p = 0.006; d = 1.10), BFlh-ST (p = 0.001; d = 1.35) and SM-ST (p = 0.020; d = 0.91). The comparisons between tasks for each muscle demonstrated significant differences for SM (p = 0.025; d = 0.60) and ST (p = 0.026; d = 0.60); however, no differences were seen for BFlh (p = 0.062; d = 0.46). Therefore, fatigue effects induce different patterns on the hamstring muscles in HE and KF tasks when performed at 20% MVIC. [ABSTRACT FROM AUTHOR]