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Functional independence of the transversus abdominis (TrA) from other trunk muscles for postural control is still unclear. This study aimed to clarify the specific function of the TrA to control standing posture by vibratory stimulation of the triceps surae. Fifteen men participated in this study. Muscle activity of the TrA, internal oblique, lumbar multifidus, gluteus maximus, rectus femoris, biceps femoris, gastrocnemius, and tibialis anterior was measured using fine-wire and surface electrodes. Participants were asked to maintain a quiet standing posture with and without vibration of the triceps surae, which induced a kinesthetic illusion and the concomitant backward sway of the body. The muscle activity of each muscle for 10 s was extracted with and without vibration. The muscle activity levels were compared between the conditions by a paired t-test or Wilcoxon signed-rank test. The activity of the TrA and rectus femoris was increased, whereas the internal oblique showed no change as a result of the induced kinesthetic illusion. In addition, the activity of the multifidus and biceps femoris was decreased. The TrA and rectus femoris could contribute to control the backward sway of the body. Furthermore, the TrA may have functional independence from the internal oblique during standing postural control. These results warrant further study in patients with low back pain. [ABSTRACT FROM AUTHOR]

Simple Summary: This study compared the muscle fiber composition of working and companion dog breeds to understand how their muscles adapt to breed-specific tasks. By analyzing the triceps brachii and biceps femoris muscles of 12 dogs, we found that working dogs had larger muscle fibers, a higher proportion of endurance-related fibers (types IIa and I), and more nuclei per fiber, which support strength and endurance. Companion dogs, on the other hand, had more fibers suited for short bursts of activity (type IIb) and fewer nuclei per fiber, suggesting slower muscle regeneration. These results highlight the role of selective breeding in shaping muscle structure and function in dogs. The structural and functional characteristics of skeletal muscle fibers play a crucial role in understanding the physical capabilities of dogs, particularly in relation to their breed-specific roles. This study aimed to compare the muscle fiber composition of working and companion dog breeds by analyzing the triceps brachii and biceps femoris muscles, focusing on fiber morphology, myosin heavy chain (MYH) isoform distribution, and nuclei per fiber. A total of 12 dogs, divided equally into working and companion breed groups, were used in this study. Muscle samples were collected post-mortem and prepared for histological analysis using cryosectioning. Immunohistochemical staining was employed to identify the expression of MYH isoforms, including MYH2, MYH4, and MYH7, which correspond to type IIa, IIb, and type I fibers, respectively. The results demonstrated significant differences between the two breed groups. Working dogs exhibited larger muscle fibers, a higher proportion of type IIa (MYH2) and type I (MYH7) fibers, and a greater number of nuclei per fiber, suggesting adaptations for endurance and strength. In contrast, companion dogs showed a higher proportion of type IIb (MYH4) fibers, indicative of their capacity for short bursts of activity rather than sustained exertion. Companion breeds also displayed a higher fiber density but fewer nuclei per fiber, which may contribute to slower muscle regeneration. These findings may provide insights into the muscle adaptations of dogs based on their breed-specific functional demands and highlight the importance of considering these differences in veterinary care and rehabilitation. The study underscores the influence of selective breeding on muscle structure and function in dogs and suggests further research into breed-specific muscle recovery mechanisms. [ABSTRACT FROM AUTHOR]

Assessment of biomechanical features whilst running on an uneven terrain plays an important role in identifying running-related injury mechanisms. However, feedback and feedforward motor responses and adaptations, an important component of gait retraining and injury rehabilitation programs, have been less investigated during running. Therefore, the current study assessed the whole-session responses and within-session adaptation mechanisms during perturbed running. Twenty three individuals performed an eight-minute perturbed treadmill running protocol with one-sided decelerative belt perturbations. Joint angle curves and muscle activity amplitudes were analysed throughout the running cycle, in both the perturbed and contralateral leg. For the whole-session responses, the average of 10 consecutive strides during the baseline trial and all perturbed strides from the perturbed running trial were compared. To assess within-session adaptation, the first perturbation was compared to the average of the last three perturbations. Data were analysed with one-dimensional statistical parametric mapping of Paired t -tests to assess responses and adaptations to the perturbations (P < 0.025). Regarding whole-session responses (baseline vs. perturbations), statistically significant feedback (after perturbation) responses were detected in most measured joint angles and muscle activity of both perturbed and contralateral legs. Feedforward (before perturbation) responses for whole-session comparison were detected for most joint angles in the contralateral leg and only hip flexion in the perturbed leg. Feedforward muscle activities of whole-session responses were different in the biceps femoris, semitendinosus, and erector spinae of the perturbed leg, and the soleus of the contralateral leg. Regarding within-session (first vs. last three perturbations) adaptation, feedback adaptations included statistically significant changes in ankle, knee, and hip movements, and muscle activities in the perturbed leg, while the contralateral leg showed less adaptation. No significant feedforward within-session adaptations were observed in the perturbed leg, but the contralateral leg showed changes in ankle dorsiflexion, soleus activity, and erector spinae activity. Findings suggest that participants compensated perturbations during running by modifying muscle activities and movement patterns, primarily through feedback mechanisms in the perturbed leg, with limited feedforward adaptations. The current protocol may present a viable approach for testing and training postural control during running. [ABSTRACT FROM AUTHOR]

Backgroud: The main function of the hamstring muscles is to bend the knee joint and support the function of the hip extensors. Their frequent injuries are the result of overload related to, among others, dynamic running or jumping, and inadequate preparation for athletics activities. The asymmetry of the work of individual flexor muscle groups is clearly marked in the case of valgus or varus of the knee joint, i.e., in different positions of the lower limb. The aim of the study was to determine the position and form of a rehabilitation exercise in which an isolated group of muscles flexing the knee joint will show the greatest bioelectrical activity. Methods: The study involved 25 students of the Jagiellonian University Medical College. The students were aged 20–26. The average age was 22.9 (±1.4). The study participants included 17 women with an average age of 23.0 (±1.1) and 8 men with an average age of 22.6 (±1.9). Women constituted 68% and men 32% of all respondents. All participants agreed to participate in the study. Surface electromyography measurements in both lower limbs provided an initial number of 50 cases. The activity of the knee flexor muscles during isometric contraction with resistance was measured in correlation with three foot and lower leg settings: internal rotation, neutral position, and external rotation. The bioelectrical activity of the semitendinosus muscle is significantly higher (p < 0.01) in the internal rotation position than in the neutral position of the lower leg, while the bioelectrical activity of the biceps femoris muscle is inversely higher (p < 0.01) in the external rotation position than in the neutral position. Results: The results are significant for both average and maximum values of muscle stimulation. During isometric contraction with resistance, the semitendinosus muscle shows the greatest bioelectrical activity in the internal rotation position of the lower leg and foot, and the biceps femoris muscle in the external rotation position of the lower leg and foot. Conclusions: The above information has important implicational applications when improving isolated groups of hamstrings. In the future, this may contribute to more effective rehabilitation of patients with injuries of the muscles described in the article. [ABSTRACT FROM AUTHOR]

The Nordic hamstring curl appears effective in reducing the incidence of injury in physically active young adults, likely through its capacity as an eccentric exercise to increase muscle stiffness. Although eccentric exercises have been shown to increase muscle stiffness, medium- and long-term Nordic hamstring curl training programs have not demonstrated an effect on muscle stiffness. This study examined the acute effects of a single session of Nordic hamstring curls on the stiffness of the biceps femoris, semitendinosus, and semimembranosus muscles using ultrasound shear wave elastography, an accepted method for measuring passive muscle stiffness. Twenty physically active adults (ages 19–27 years) were randomly assigned to either the Nordic hamstring curl group (n = 10) or the control group (n = 10). Shear wave elastography was performed on the dominant kicking leg for both groups. The exact location of the probe was marked to ensure the same area was assessed during post-testing. Both groups performed a 5-minute cycle ergometer warm-up followed by three 30-second standing static stretches. The Nordic hamstring curl group then performed three sets of six repetitions of the eccentric phase of the Nordic hamstring curl with 1-minute rest intervals between sets. All subjects then rested for five minutes before shear wave elastography was performed. Repeated measures ANOVA revealed no significant main effects or interactions for the biceps femoris or semitendinosus (p >0.05). However, analysis of the semimembranosus was inconclusive due to variability of measurement values. These results are in agreement with findings indicating that long- and short-term Nordic hamstring curl training has no impact on hamstring stiffness, although the effects of Nordic hamstring curl on reducing the probability of hamstring injury are still valid. [ABSTRACT FROM AUTHOR]

• Analysing biomechanical effects of back-support exoskeletons during working tasks using statistical parametric mapping. • Significant reduction in activity of biceps femoris muscle and hip flexion during the downward phase of lifting. • Decreased muscle activity of biceps femoris muscle and increased knee and ankle flexion in carrying and walking. • Biomechanical changes indicate need for improved exoskeleton designs as they suggest potential stain in other body parts. Introduction: In response to physically demanding industrial environments, back-support exoskeletons (BSEs) have emerged as assistive devices. However, their functional interaction with body structures and potential in preventing musculoskeletal disorders (MSDs) remain unclear. The objective of this study was to analyze biomechanical motion sequences throughout the entire process of different work movements and provide a comprehensive assessment of the influence of BSE. Method: Using statistical parametric mapping (SPM) methodology, we examined and quantify the magnitude of significant effects of BSEs on muscle activity (MA) and kinematic movement patterns during lifting, carrying, walking, and static bending in a standardized manner. Results: Significant changes with large effect sizes were identified during the downward phase of the lifting task, indicating decreased MA in the musculus (M.) biceps femoris and a reduced hip flexion. The usage of BSEs during carrying and walking resulted in a decreased MA of M. biceps femoris during the legs' pre- and mid-swing phases, accompanied by an increased knee and ankle flexion. These changes in MA and kinematics, especially when the BSEs exert pressure on the leg shells through their supporting function, may be indicative of strain in other body regions due to the BSEs. Practical Applications: We suggest that the evaluated effects may lead to the non-use of BSEs in the workplace and should therefore be considered in the development of alternative BSE designs. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to identify the contribution of the common synaptic drives to motor units during obstacle avoidance, using coherence analysis between a-pair electromyography (EMG) signals (EMG-EMG coherence). Materials and Methods: Fourteen healthy volunteers walked on a treadmill with and without obstacle avoidance. During obstacle gait, subjects were instructed to step over an obstacle with their right leg while walking that would randomly and unpredictably appear. Surface EMG signals were recorded from the following muscles of the right leg: the proximal and distal ends of tibialis anterior (TAp and TAd), biceps femoris (BF), semitendinosus (ST), lateral gastrocnemius (LG), and medial gastrocnemius (MG). Beta-band (13–30 Hz) EMG-EMG coherence was analysed. Results: Beta-band EMG-EMG coherence of TAp-TAd during swing phase and BF-ST during pre and initial swing phase when stepping over an obstacle were significantly higher compared to normal gait (both p < 0.05). Beta-band EMG-EMG coherence of TAp-TAd, BF-ST, and LG-MG during stance phase were not significantly different between the two gait conditions (all p > 0.05). Conclusions: The present findings suggest increased common synaptic drives to motor units in ankle dorsiflexor and knee flexor muscles during obstacle avoidance. It also may reflect an increased cortical contribution to modify the gait patterns to avoid an obstacle. [ABSTRACT FROM AUTHOR]

A pilot study was conducted with the aim of adapting the processing of "Kraški pršut", dry-cured ham, for thighs from heavy pigs. The focus was on the effect of ham weight and salting duration on the quality of dry-cured ham. From a pool of thighs harvested from heavy pigs, a total of 32 green hams were selected (from 16 carcasses) based on weight (two classes; L—lighter, H—heavier) and we used left and right ham for either the standard or a shortened salting phase. Salting duration consisted of phase 1 (7 days for all hams) and phase 2 (7 or 14 days for L, 10 or 17 days for H, in the case of shortened and standard salting, respectively). Equivalent conditions for all hams were maintained during the remaining phases, with a total maturation period of 18 months. The analysis focused on chemical, physical and rheological properties, sensory attributes, and consumer perceptions. The H hams had lower processing losses, resulting in higher moisture and water activity, lower salt content in internal biceps femoris muscle, and a softer texture (instrumental and sensory) than L hams. The salting duration mainly affected weight losses in the salting phase and, consequently, salt content, which was lower in the shortened salting phase, while no effects were observed on texture. The sensory panel perceived weight's effect on hardness, with L hams being perceived as harder, and salting's effect on sourness, with hams submitted to longer salting perceived as sourer than H hams. Consumer testing indicated a general preference for softer and less salty hams. Overall, the results show that the applied reduction in salting duration was not substantial, and future trials should explore further optimization in terms of salting and resting phases. [ABSTRACT FROM AUTHOR]

Purpose: Muscle activation often occurs in muscles ipsilateral to a voluntarily activated muscle and to a greater extent after stroke. In this study, we measured muscle activation in non-target, ipsilateral leg muscles and used transcranial magnetic stimulation (TMS) to provide insight into whether corticomotor pathways contribute to involuntary activation. Materials and methods: Individuals with stroke performed unilateral isometric ankle dorsiflexion, ankle plantarflexion, knee extension, and knee flexion. To quantify involuntary muscle activation in non-target muscles, muscle activation was measured during contractions from the ipsilateral tibialis anterior (TA), medial gastrocnemius (MG), rectus femoris (RF), and biceps femoris (BF) and normalized to resting muscle activity. To provide insight into mechanisms of involuntary non-target muscle activation, TMS was applied to the contralateral hemisphere, and motor evoked potentials (MEPs) were recorded. Results: We found significant muscle activation in nearly every non-target muscle during isometric unilateral contractions. MEPs were frequently observed in non-target muscles, but greater non-target MEP amplitude was not associated with greater non-target muscle activation. Conclusions: Our results suggest that non-target muscle activation occurs frequently in individuals with chronic stroke. The lack of association between non-target TMS responses and non-target muscle activation suggests that non-target muscle activation may have a subcortical or spinal origin. Non-target muscle activation has important clinical implications because it may impair torque production, out-of-synergy movement, and muscle activation timing. [ABSTRACT FROM AUTHOR]

[Objectives] This study aimed to determine the effects of maternal addition with probiotics and synbiotics on the muscular amino acid composition and gene expression of offspring Bama mini-pigs. [Methods] A total of 64 pregnant Bama mini-pigs were selected and randomly divided into control (antibiotic-free basal diet), antibiotic (50 g·t-1 virginiamycin), probiotics (200 mL·d-1 probiotic mixture), and synbiotics (500 g xylo-oligosaccharide per ton diet+200 mL·d-1 probiotics mixture) groups, with 16 sows in each group. The sows were raised individually and fed with the corresponding experimental diets during pregnancy and lactation periods. After weaning, two piglets per litter and thirty-two piglets per group were selected and fed a basal diet (eight pens per group, four pigs per pen) . At 65, 95, and 125 days of age, eight pigs per group were selected and biceps femoris (BF) and psoas major (PM) muscles were sampled to determine hydrolyzed amino acid composition and gene expression. [Results] Compared with the control group, the contents of crude protein, Gly, Ser, Ala, Asp, Glu, Pro, and Ile in the BF muscle and Gly, Glu, Ser, and His in the PM muscle increased in the synbiotics group (P<0.05); the expression levels of muscle atrophy F-box protein 32 and myogenin (MyoG) in the BF muscle and myogenic factor 5 (Myf5) in the PM muscle were upregulated in the probiotics group (P<0.05), whereas the expression levels of myosin heavy chain Ⅱb (MyHCⅡb) in the BF muscle and myostatin (MSTN) in the BF and PM muscles were downregulated in the probiotics group (P<0.05); the expression levels of Myf6, myogenic differentiation factor, and MyoG in the BF muscle and Myf5 and MyoG in the PM muscle were upregulated in the synbiotics group (P<0.05), whereas those of MSTN in the BF muscle were downregulated (P<0.05); the expression levels of MyHCⅡx in the BF muscle were downregulated in the probiotics and synbiotics groups (P<0.05); the expression levels of MyHCⅡx in the PM muscle were upregulated whereas MyHCⅠ in the BF muscle and MyHCⅡa in the PM muscle were downregulated in the antibiotic group (P<0.05) . [Conclusions] Maternal addition with probiotics and synbiotics could alter muscular amino acids composition, regulate the expression of genes related to growth factors, upregulate oxidative muscle fiber gene expression, and downregulate glycolytic muscle fiber gene expression, which were beneficial to improving the meat quality of offspring. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate changes in muscle contractile properties during a training microcycle in semi-professional female football players and explore their relationship with training load variables. Nineteen players (age: 23.9 ± 3.9 years; body mass: 60.6 ± 6.9 kg; height: 164.5 ± 6.7 cm) underwent myotonometric assessments of the biceps femoris (BF) and rectus femoris (RF) before and after the following training sessions: MD1 (i.e., 1 day after the match), MD3, MD4, and MD5. Training loads were quantified for each session, revealing significant variations, with MD4 exhibiting the highest values for high-speed running distance, number of sprints, and accelerations. Notably, MD3 showed the highest perceived exertion (RPE), while MD5 recorded the lowest total distance run. Myotonometric assessments indicated significant differences in stiffness of the RF in MD3 and BF in MD5, as well as RF tone in MD5. The findings underscore a notable relationship between training load and myotometric variables, particularly in muscle stiffness and tone. These results emphasize the need for further research to clarify how training loads affect muscle properties in female athletes. [ABSTRACT FROM AUTHOR]

High-altitude landing maneuvers can pose a significant injury risk, particularly when performed with different landing techniques. This study aims to compare the biomechanical parameters and injury risks associated with two landing positions—staggered foot landing and simultaneous bilateral landing—using Xsens inertial units and electromyography (EMG) sensors. A total of 26 university students (13 males, 13 females) participated in this study. Kinematic data were collected using inertial measurement units (IMUs), muscle activity was recorded with EMG, and ground reaction forces were captured using 3D force plates. The data were processed and analyzed using the AnyBody modeling system to simulate joint forces, moments, and muscle activation. This study found that simultaneous bilateral landing exhibited greater hip flexion-extension, knee flexion-extension, and ankle inversion. Vertical joint forces were also significantly higher in the hip, knee, and ankle during simultaneous bilateral landing. Staggered foot landing showed higher muscle forces in the gluteus maximus, iliopsoas, and quadriceps femoris (p < 0.001). The EMG analysis revealed significant differences in the biceps femoris (p = 0.008) and quadriceps femoris (p < 0.001). These findings suggest that simultaneous bilateral landing increases joint load, while staggered foot landing increases muscle activation, which may lead to different injury risks between the two techniques. [ABSTRACT FROM AUTHOR]

Objective: To investigate the effects of mild fatigue on the biomechanics of the lower limbs of young male volleyball players while performing single leg landing tasks. Methods: A total of ten young male volleyball players were recruited as participants in this study. After the single leg landing was performed, we compared the performance between those with and without fatigue (post- and non-fatigue, respectively). Kinematics and kinetics were collected using instruments, and related captured data were imported into OpenSim to analyze the hip, knee, and ankle joints. Results: We found that the ankle dorsiflexion angle at initial contact was significantly decreased in the post-fatigue group compared to the non-fatigue one. Meanwhile, the peak gluteus maximus force, peak gluteus medius force, peak tibialis posterior force, and peak gastrocnemius force significantly increased. There were no significant differences in the hip and knee joint flexion angles as well as the quadriceps and biceps femoris long head forces between the two groups. Conclusions: Mild fatigue can affect the performance of single leg landing, and players need to control the lower limbs by generating a higher muscle force to cope with the instability induced by fatigue. In a fatigued state, following initial contact with the ground, a decreased ankle dorsiflexion angle necessitates an increase in gastrocnemius and tibialis posterior muscle force to maintain stance during landing. [ABSTRACT FROM AUTHOR]

Ankle fractures can lead to issues such as limited dorsiflexion, strength deficits, swelling, stiffness, balance disorders, and functional limitations, which complicate daily activities. This study aimed to describe neuromuscular adaptations at 6 and 12 months post-surgery during static and dynamic balance tasks, specifically using the Y-Balance Test (YBT). Additionally, the relationship between neuromuscular patterns, balance, and musculoskeletal deficits was evaluated. In 21 participants (14 at 6 months and 21 at 12 months) with bimalleolar fractures, hip strength, ankle dorsiflexion, ankle functionality, and static and dynamic balance were assessed using electromyography of five lower limb muscles (tibialis anterior, peroneus longus, lateral gastrocnemius, biceps femoris, and gluteus medius). A significant interaction effect (limb × proximal [hip]—distal [ankle] muscle) (F = 30.806, p < 0.001) was observed in the anterior direction of the Y-Balance Test (YBTA) at 6 months post-surgery. During the YBTA and YBT posteromedial (YBTPM), it was found that a lower dorsiflexion range of movement was associated specifically at 6 months with greater activation of the lateral gastrocnemius. However, these differences tended to diminish by 12 months. These findings suggest that neuromuscular patterns differ between operated and non-operated limbs during the YBTA at 6 months post-surgery. The Y-Balance Test, particularly its anterior direction, effectively highlighted these neuromuscular changes. This is a preliminary study; further research is needed to explore these findings in depth. [ABSTRACT FROM AUTHOR]

Purpose: Most athletes experience short-term training cessation because of illness, injury, post-season vacation, or other reasons. Passive muscle stiffness is a potential risk factor for a sprint-type hamstring strain injury, but limited information is available about the effect of short-term training cessation on passive muscle stiffness. The present study aimed to identify whether and how passive muscle stiffness of the biceps femoris long head (BFlh) would vary due to 2 weeks of training cessation in sprinters. Methods: Passive BFlh shear-wave speed (a proxy for stiffness) was measured using ultrasound shear-wave elastography in 28 male sprinters, before and after 2 weeks of intervention. During the 2 weeks, the participants in the training-cessation group (n = 14) were allowed to maintain their normal daily activities but not to perform any physical training, including stretching and resistance exercises. The participants in the training continuation group (n = 14) performed the training (including maximum speed sprint, plyometric, and weight training) prescribed by their coaches 5 days per week. Results: In the training-cessation group, passive BFlh shear-wave speed increased after the 2 weeks of training cessation (4.75 ± 0.77 to 5.00 ± 0.88 m/s, P < 0.001). In contrast, there was no significant difference before and after the 2 weeks of training continuation (4.90 ± 0.85 to 4.93 ± 0.85 m/s, P = 0.521). Conclusions: The present findings indicate that muscles stiffen by training cessation in sprinting athletes. [ABSTRACT FROM AUTHOR]

Lipid metabolism during curing of meat products is an essential biological process that affects their eating quality. Lipid droplets (LDs) are the main sites for storing neutral lipids and participating in lipid metabolism, and their surface lipid droplet-related proteins (LDRPs) directly regulate lipid degradation. In this study, we analyzed the expression changes of LDRPs in porcine biceps femoris muscle under curing conditions (1% and 3% salt concentration) by proteomics and discussed the role played by LDs in the regulation of lipid metabolism. A total of 1127 quantitative proteins were identified by mass spectrometry. Among them, the differential proteins between the control and cured groups were mainly involved in biological processes such as lipid metabolism and carbohydrate metabolism. Protein quantification results showed that RAB18 expression was downregulated after curing, suggesting that curing caused LDs to become small and dispersed. Besides, the expression trends of proteins responsible for macroautophagy (RAB7 and RAB10) and those responsible for CMA (HSPA8 and PLIN2) in LDs were opposite. The upregulation of CPT2, ACADL, FABP4, and FABP5, which were related to fatty acid transport and β-oxidation, intensified the degradation of fatty acid in cured samples. Consequently, we concluded that curing promoted LD degradation. Macroautophagy, CMA, and lipolysis were likely to occur alternately and synergistically during the degradation process. The results have significant implications for our understanding of the metabolic processes involved in lipid molecules during meat processing. [ABSTRACT FROM AUTHOR]

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Background: Fibular collateral ligament (FCL) injuries are uncommon incidents, with less favorable healing rates compared to medial collateral ligament injuries, often necessitating repair or reconstruction as the predominant treatment approach. Indications: Using a partial-thickness biceps femoris tendon (PTBFT) autograft for FCL reconstruction or augmentation is a viable option for both acute and chronic FCL injuries, especially in patients unwilling to accept allograft tissue and in settings with limited access to allografts. Technique: The fibular head attachments of the biceps femoris tendon (BFT), FCL, and popliteofibular ligament are inspected for injury. The biceps–iliotibial band (ITB) interval is opened, and the native FCL is assessed at its midsubstance for injury. The mid-aspect of the ITB was incised in line with its fibers, and the femoral insertion of FCL is localized. A 10-mm × 70-mm graft is harvested from the middle third of the BFT, preserving the distal insertion on the fibular head. Locking Krackow sutures are placed into the proximal end of the graft, which is passed under the ITB. A femoral tunnel is created at the FCL attachment site, and the graft is placed into the femoral tunnel and secured to the femur using an interference screw. Results: Postoperatively, the patient is instructed on foot-flat touch weightbearing with 2 crutches, on a knee immobilizer, for the first 2 weeks. Increasing weightbearing status and range of motion are expected in a stepwise manner. Return to sports is permitted after 6 to 9 months and depends on the presence of any additional injuries, strength, and functional recovery. There no studies available yet on clinical outcomes. Discussion/Conclusion: FCL reconstruction or augmentation utilizing a PTBFT autograft is an underused treatment option for patients with isolated FCL insufficiency or as part of multiligamentous injuries. This procedure offers advantages such as an anatomic reconstruction; single incision for both graft harvest and FCL reconstruction; shorter, cost-effective surgery with fewer implants used; and a safer approach with reduced risk of neurovascular structures due to lack of a fibular head tunnel. This is a valuable option in the limited source setting or in a patient not accepting of allografts. Patient Consent Disclosure Statement: The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication. [ABSTRACT FROM AUTHOR]

This study aimed to develop and evaluate the reliability of a surface electromyography-based (sEMG) index to quantify knee muscle coactivation in healthy recreational athletes during the Lower Quarter Y-Balance Test (YBT-LQ). A prospective observational repeated measures design was used to assess both intra- and inter-rater reliability. Forty males completed three trials, with two raters independently conducting assessments. sEMG signals from the vastus medialis, vastus lateralis, biceps femoris, and semitendinosus muscles were collected to calculate four coactivation indices (CoAIs) for different muscle pairs. The reliability evaluation of these CoAIs was based on intraclass correlation coefficients. The results revealed that the reliability of the CoAIs varied depending on the muscle pair, direction, and limb examined. The highest intra- and inter-rater reliability was noted for the left lower limb in the posterolateral direction. The lowest reliability was found for the right lower limb in the anterior direction. Statistical analyses indicated significant differences in specific CoAIs across different YBT-LQ directions. These findings highlight the potential of sEMG-based CoAIs for assessing knee muscle activity during the YBT-LQ in healthy male recreational athletes. However, choosing CoAIs is critical for reliable clinical and research assessments of knee stability and neuromuscular control. [ABSTRACT FROM AUTHOR]

Objectives: The aim of this study was to investigate the effects of acorn diets on the composition of fatty acid (FA) and the intramuscular fat (IMF) content in Yuxi black pigs. Methods: Ninety Yuxi black pigs with similar body weight (99.60 ± 2.32 kg) were randomly divided into five groups. The control group was fed a basal diet, and the AD20, AD30, AD40, and AD50 groups were fed experimental diets which contained 20%, 30%, 40%, and 50% acorns, respectively. The feeding experiment lasted for 120 days. Results: The results showed that compared with the control group, the content of SFA in longissimus dorsi and biceps femoris tissues in the AD30 group decreased by 8.57% and 20.10%, and the content of MUFA increased by 5.40% and 15.83%, respectively, while the PUFA content of biceps femoris increased by 5.40% (p < 0.05). Meanwhile, the IMF content of the AD30 group was significantly higher than that of the control group in the longissimus dorsi and biceps femoris. In addition, the mRNA expression levels of the ATGL, PPARγ, and FABP4 genes in longissimus dorsi (p < 0.05) were up-regulated, and HSL were down-regulated (p < 0.05) in the AD30 group. In the biceps femoris of the AD30 group, it was observed that the expression levels of the ACC and FAS genes were up-regulated (p < 0.05), while HSL and ATGL genes were down-regulated (p < 0.05). Conclusions: These results demonstrated that the addition of appropriate amounts of acorn to the diet (a 30% acorn diet) could improve the nutritional value of pork. [ABSTRACT FROM AUTHOR]

BACKGROUND: Surface electromyography has been extensively utilized for monitoring muscle fatigue. However, traditional electromyographic metrics typically focus on individual muscles and fail to assess the variations in a muscle group during the fatigue process. OBJECTIVE: To establish a muscle functional network to extract complex network parameters and investigate the topological property changes of the muscle functional network under different levels of fatigue, aiming to provide theoretical and methodological foundations for fatigue monitoring and prevention. METHODS: Eleven participants performed single-leg leg press exercise at 50% of one-repetition maximum until exhaustion. Simultaneously, electromyographic signals of seven muscles (rectus femoris, vastus lateralis, vastus medialis, biceps femoris, tibialis anterior, lateral gastrocnemius, and medial gastrocnemius), electrocardiographic signals, and Borg CR-10 scale scores were collected. The Borg CR-10 scale was used to categorize three fatigue stages: mild, moderate, and severe. Heart rate and heart rate variability were calculated to validate the effective division of fatigue stages. Using the coherence of muscle signals, a muscle functional network was constructed with the seven muscles as nodes, and four complex network parameters (clustering coefficient, average weighted degree, global efficiency, and eigenvector centrality) were extracted. Additionally, four electromyographic indices (root mean square, median frequency, instantaneous mean frequency, and co-activation ratio) were extracted and compared under the three levels of fatigue. RESULTS AND CONCLUSION: (1) Differences in heart rate and heart rate variability were observed across three fatigue stages, indicating the effectiveness of fatigue stage delineation. (2) Electromyographic indicators for different muscles under three levels of fatigue: root mean square and co-activation ratio showed no differences; however, median frequency exhibited robust fatigue trends in vastus lateralis, vastus medialis, and biceps femoris, while instantaneous mean frequency demonstrated robust fatigue trends in rectus femoris, vastus lateralis, vastus medialis, and biceps femoris. Instantaneous mean frequency outperformed median frequency and root mean square, yet all three indicators showed robust trends only for the major working muscle groups, unaffected by fatigue factors, unlike the co-activation ratio. (3) The connectivity strength between vastus lateralis and vastus medialis, vastus lateralis and biceps femoris, vastus lateralis and gastrocnemius medialis, and vastus medialis and biceps femoris gradually increased, showing significant differences in average weighted degree, clustering coefficient, and global efficiency post-fatigue, significantly correlated with fatigue levels. To conclude, changes in connectivity strength reflect the synergy and complementarity among muscles during fatigue. Clustering coefficient, average weighted degree, and global efficiency serve as fatigue markers reflecting overall muscle changes. [ABSTRACT FROM AUTHOR]

Abstract Despite the increase in research of hamstring stiffness through the use of ultrasound-based shear wave elastography, the active stiffness of biceps femoris long head (BFlh) and semitendinosus (ST) muscles under fatigue conditions at various contraction intensities has not been sufficiently explored. This study aimed to compare the effects of knee flexor’s isometric contraction until exhaustion performed at 20% vs. 40% of maximal voluntary isometric contraction (MVIC), on the active stiffness responses of BFlh and ST. Eighteen recreationally active males performed two experimental sessions. The knee flexors’ MVIC was assessed before the fatiguing task, which involved a submaximal isometric contraction until failure at 20% or 40% of MVIC. Active muscle stiffness of the BFlh and ST was assessed using shear wave elastography. BFlh active stiffness remained relatively unaltered at 20% of MVIC, while ST active stiffness decreased from ≅ 91% contraction time (55.79 to 44.52 kPa; p 0.05) or ST (63.62 to 53.54 kPa; p > 0.05) at 40% of MVIC session. Intermuscular active stiffness at 20% of MVIC differed until 64% contraction time (p 0.05), but a steeper increase in BFlh/ST ratio was found for 20% (0.004 ± 0.003 ratio/%) compared to 40% (0.001 ± 0.003 ratio/%) of MVIC (p = 0.003). These results suggest that contraction duration could play a major role in inducing changes in hamstrings’ mechanical properties during fatigue tasks compared to contraction intensity.

Given the posterior chain configuration, it is anticipated that tibial positioning influences hamstring recruitment; medial hamstrings should be more activated during medial rotation, while lateral hamstrings should be more activated during lateral rotation. However, most studies showing this pattern have focused on concentric or isometric strength, leaving the influence on eccentric strength fairly unknown. Therefore, the aim of this study was to investigate the electromyographic response of the hamstring muscles during Nordic hamstring exercises in three leg positions: internal rotation, external rotation, and neutral. This study encompassed a randomized crossover study and used surface electromyography to analyze the activity of the biceps femoris and semitendinosus muscles during the Nordic hamstring exercise, in the three positions. Results indicated no statistically significant differences in muscle activation between positions or sides (p > 0.05), though small effect sizes were observed for the biceps femoris in different positions (η2 = 0.01–0.03). Furthermore, the internal rotation position generally elicited the highest muscle activations. Notably, biceps femoris muscles exhibited higher activations compared to semitendinosus muscles, with the greatest differences seen in the internal rotation position. This suggests that tibial rotation influences hamstring recruitment patterns; however, it was lower than expected.

Hamstring injuries are associated with decreased hamstring strength. Matinlauri et al.'s 90:20 Isometric Posterior Chain Test (90:20 IPCT) efficiently assesses hamstring strength, but has not been validated so far. Furthermore, their rather unprecise original instruction allows high variability in test execution. We added a new instruction and variables and examined, whether this measure leads to increased reliability and validity. We assessed hamstring strength of 23 sport students via the 90:20 IPCT under the original instruction, to exert vertical force, and our new instruction, to exert vertical and horizontal force. Instead of only using bare vertical force as variable under the original (Fz_V) and our new instruction (Fz_VH), we also calculated the resultant force (Fres_VH) and the applied torque onto the force place (M_F_ortho_VH). To test for validity, we correlated the outcome variables with peak torque of gold standard dynamometry. Furthermore, we measured muscle activities of the mm. rectus femoris, biceps femoris, semitendinosus, and gluteus maximus under our new instruction and compared them to those under the original variable (Fz_V) via one sample t-tests. To evaluate reliability, tests were repeated on two separate days, for which we calculated intra class correlation coefficients (ICCs) and coefficients of variation (CVs). Our new instruction and variables (Fz_VH, Fres_VH, M_F_ortho_VH) showed better validity (mean r = 0.77, r = 0.81, and r = 0.85) and equally good or better reliability (ICCs: 0.87, 0.89, and 0.94; CVs: 4.7%, 4.1%, and 4.7%) than the original instruction and variable (Fz_V) (mean r = 0.70; ICC: 0.91; CV: 5.6%). There were no differences in muscle activities between the variables and instructions of the 90:20 IPCT. We recommend our new instruction and the applied torque onto the force plate as it makes the 90:20 IPCT a more reliable and valid tool to assess hamstring strength. [ABSTRACT FROM AUTHOR]

The foot structure is associated with different running mechanics. The central nervous system is responsible for using the muscles through synergies during locomotion. The purpose of the present study was to examine the effect of foot structure on the electromyography factors and the synergy of the selected muscles of the lower extremity. Tibialis anterior, extensor digitorum longus, peroneus longus, soleus, biceps femoris, vastus lateralis, gastrocnemius lateralis and medialis muscles activity of 60 barefoot recreational runners with different foot structures was recorded while running at a speed of 3.3 m/s. Muscle activity was measured in the running cycle. Besides, muscle synergies were extracted using non-negative matrix factorization algorithm. The results showed that there were differences between groups with different foot type in muscle activity under different phases of running in some muscles. Furthermore, the findings indicated that the number of synergies was similar in different groups and the relative weight of muscles was not different across groups. In conclusion, despite the difference in muscle activity under different phases of the running cycle, muscle synergies are similar among the groups. This can indicate similar control by the central nervous system in runners with different arch structures while running and the observed changes in muscle activity can be attributed to the type of forces exerted on the body, the length-tension relationship, and changes in the direction of the lower limbs in people with different arch structures. [ABSTRACT FROM AUTHOR]

Prolonged squatting is a well-documented cause of common peroneal neuropathy, wherein the common peroneal nerve is thought to be compressed between the biceps femoris tendon and the lateral head of the gastrocnemius muscle or the fibular head. However, deep peroneal neuropathy resulting from prolonged squatting has not been previously reported. We present the case of a tile installer who developed unilateral deep peroneal neuropathy following extended squatting, diagnosed through ultrasonography, which identified the bilateral division of the common peroneal nerves between the knee joint and the fibular head. This case underscores the value of ultrasonography, particularly when electrodiagnostic results are inconsistent with clinical expectations. [ABSTRACT FROM AUTHOR]

The study aimed to explore the differences in muscle quality characteristics between the longissimus muscle and the biceps femoris muscle of Yanshan cashmere goats. The experiment selected 10 Yanshan cashmere goats at the age of 30 months and measured their slaughter performance, muscle physicochemical properties, and nutritional components respectively. The results showed that the average pre-slaughter body weight of the Yanshan cashmere goats was 34.81 kg, with a carcass weight of 16.5 kg, a slaughter rate of 48.2%, an eye muscle area of 13.69 cm², and a GR value of 7.43 mm. The crude protein content in the longissimus muscle was extremely higher than that in the biceps femoris (P<0.01), while the intramuscular fat content in the biceps femoris was extremely higher than in the longissimus muscle (P<0.01). The C18 : 0 content in the longissimus muscle was extremely higher than in the biceps femoris (P<0.01), and the C20 : 0 content in the biceps femoris was significantly higher than in the longissimus muscle (P<0.05). Correlation analysis showed that in the longissimus muscle, moisture content was extremely positively correlated with crude protein content (P<0.01), and water loss was extremely negatively correlated with shear force (P<0.01). In the biceps femoris, moisture content was significantly positively correlated with pH value (P<0.05), water loss was significantly positively correlated with redness (a*) value (P<0.05), the muscle a* value was extremely positively correlated with yellowness (b*) value (P<0.01), lightness (L*) value was extremely positively correlated with b* value (P<0.01), and intramuscular fat content was significantly negatively correlated with cooked meat yield (P<0.05). The study suggests that the biceps femoris of Yanshan cashmere goats has more intramuscular fat deposition, while the longissimus muscle has a higher crude protein content. [ABSTRACT FROM AUTHOR]

Objective: To describe the relationship between bilateral electrical activity in the biceps femoris and the variation of triaxial acceleration in three 50 m sprints. Methods: Biceps femoris muscle activation and acceleration in the anterior–posterior, mediolateral, and superior–inferior axes were measured in three 50 m sprints in nine national-level sprinters. Results: There was significant asymmetry between both legs, and the variations between axes were significant between the anterior–posterior with respect to the lateral and superior–inferior, and between the lateral and superior–inferior (p < 0.05). Conclusions: Increased biceps femoris activation during running increases speed regardless of asymmetry in force application. In the maintenance of horizontal velocity, acceleration of the anterior–posterior axis is the most relevant and depends on the flexion-extension muscle actions contained in the lateral axis. [ABSTRACT FROM AUTHOR]

BACKGROUND RESULTS CONCLUSION Consumers' preferences for lamb meat vary greatly depending on the specific cut. Variations in the chemical composition across different muscle types play a crucial role in determining meat quality, particularly with regard to flavor. Therefore, it is essential to study the variations in chemical composition among different muscle types in lamb, as well as the mechanisms behind their formation, aiming to understand the flavor variation across the muscle types.Flank muscles showed significantly higher intramuscular fat content and muscle fiber diameter compared to triceps brachii and biceps femoris (BF), at the same time as displaying a significantly lower percentage of type I muscle fibers. Forty‐three differentially abundant volatile compounds (DAVC) were identified across five muscles, with the majority of DAVCs being more abundant in the BF. In total, 161 differentially abundant lipids were identified across five muscles, with triglycerides (TG), phosphatidylcholines (PC), phosphatidyl ethanolamines (PE) and phosphatidylmethanol (PMeOH) showing a strong correlation with DAVCs. A lipid‐gene regulatory network was established, encompassing 664 lipids and 11 107 genes, leading to the identification of pathways and genes that regulate the metabolism of PEs, PMeOH, PCs and TGs.The present study showed the significant variation in flavor compounds among the five edible muscles, as well as the potential reasons for their formation. The results potentially provide a theoretical foundation for improving the meat quality of lamb. © 2024 Society of Chemical Industry. Published by John Wiley & Sons Ltd [ABSTRACT FROM AUTHOR]

Objective Methods Results Conclusion An important reason for the poor recovery of anterior cruciate ligament (ACL) injuries is the poor recovery of muscle function. Therefore, we used surface electromyography (sEMG) and gait analysis to explore the muscle activation patterns and gait characteristics between lower limbs under different exercise states in patients, following anterior cruciate ligament reconstruction (ACLR).Forty‐one adults with unilateral ACL injuries in Binzhou Medical University Hospital from October 2022 to June 2023 were allocated to three groups according to the time after ACL reconstruction: group A (≤3 months, 16), group B (3 months–1 year, 13), and group C (>1 year, 12). Patients were tested by sEMG and gait, while straight leg raising (SLR), walking at normal speed, fast walking, and walking up and down the stairs. Two related sample tests were performed for the normalized root mean square (RMS) values and gait parameters.Muscle function changes varied in different training tasks. The RMS value of the involved side was more than the uninvolved side in biceps femoris and semitendinosus of group A (p < 0.010), and for the bilateral rectus femoris (RS), vastus medialis (VM), and vastus lateralis in group B, only the comparison of the RS was significant in group C during fast walking and going up and down the stairs. The ground impact (0.90 [0.63, 1.33] vs. 0.71 [0.43, 1.02], p = 0.035) of the uninvolved side was significantly decreased compared to those of the involved side in patients with ACLR when going down the stairs.Different muscles need to be focused on at different stages of the postoperative period. sEMG and gait analysis can guide the development of a rehabilitation program. [ABSTRACT FROM AUTHOR]

Cable-driven robots are commonly applied in the rehabilitation field. Many tendon-based systems use parallel end-effector structures because of the advantages of fast reactions and high force outputs. We previously developed an active cable-driven robotic system that enabled accurate force control and was applied while walking on a treadmill. However, the kinematic and kinetic assistance methods need to be improved. Given the advantages of tendon-based parallel systems, this study investigated walking generated by four cables that were directly attached around the ankle. The aim of this work was to develop a tendon-based parallel robotic system to provide assisted walking on a treadmill with gait-specific position guidance and force compensation. To demonstrate the assistance effects, preliminary physiological responses of leg muscles during walking with the system were investigated. A parallel robotic system with four cable-driven units was developed. Kinematic and kinetic analyses of walking were performed, followed by the development of control algorithms for walking with impedance assistance only and walking with impedance assistance plus kinetic compensation. The muscle activity of the rectus femoris, vastus lateralis, gluteus maximus, biceps femoris, and gastrocnemius muscles was recorded and analyzed. On the basis of the kinematic and kinetic analyses, the tendon-based parallel robotic system produced treadmill walking with position and force assistance. The force control algorithms tracked the target force profile with a mean error of 6.4 N. During impedance-assisted walking, the rectus femoris, gluteus maximus and biceps femoris muscles produced a mean electromyography of 115.1% of the activity during independent walking (without assistance). However, the activity of the vastus lateralis and gastrocnemius reduced to only 82.5% of that during independent walking. Further kinetic compensation generally reduced the muscle activity, with the mean electromyography result being 88.7% of that during independent walking. From a technical point of view, the tendon-based parallel robotic system provided walking-specific position and force assistance in leg movement, accompanied by reduced muscle activity compared with independent walking. A technical feasibility study will be conducted to evaluate whether the tendon-based parallel robotic system is feasible for assisted treadmill walking in the general population and whether position guidance and force assistance are acceptable. [ABSTRACT FROM AUTHOR]