Search Results (1,690)

Evaluating maximal strength, inter-limb asymmetries, and the hamstring-to-quadriceps (HQ) ratio is essential for identifying strength deficits in athletes. This cross-sectional study assessed the test–retest (inter-visit) reliability of the EasyForce dynamometer for knee extension and flexion strength in 21 young healthy participants (11 women and 10 men; age = 19.4 ± 0.7 years). The dynamometer demonstrated excellent relative reliability, with ICC values of 0.99 for knee extension and 0.95–0.98 for knee flexion. Absolute reliability was also acceptable (typical error = 5.63–16.44 N; coefficient of variation = 3.94–6.80%). Reliability for inter-limb asymmetries (ICC = 0.90) and HQ ratios (ICC = 0.91–0.92) was good to excellent. Agreement for inter-limb asymmetry direction between visits was excellent for knee extension (κ = 0.90) and substantial for knee flexion (κ = 0.71). These findings suggest that EasyForce is reliable for assessing muscle strength, inter-limb asymmetries, and HQ ratios in physically active adults. Future research should explore the broader applicability of EasyForce in muscle strength assessment, particularly for professional athletes and during rehabilitation. Full article

This study aimed to investigate the effects of different dietary concentrate-to-forage ratios on slaughter performance, meat quality, rumen fermentation, rumen microbiota and fecal microbiota in Tibetan sheep. A total of sixty male Tibetan sheep were equally allocated into three dietary groups based on concentrate-to-forage ratios, i.e., 30:70 (C30), 50:50 (C50), and 70:30 (C70). Compared with the C30 group, sheep fed the C70 diet resulted in a higher (p < 0.05) slaughter live weight (SLW), hot carcass weight (HCW), dressing percentage (DP), eye muscle area, average daily gain (ADG), and ruminal total volatile fatty acids concentration and propionate molar proportion and lower (p < 0.05) shear force and cooking loss of meat, and ruminal acetate molar proportion and acetate:propionate ratio. Sheep in the C50 group exhibited a higher (p < 0.05) SLW, HCW, ADG, and ruminal propionate molar proportion and lower (p < 0.05) shear force and cooking loss of meat, and ruminal acetate molar proportion and acetate: propionate ratio compared with the C30 group. In rumen fluid, the relative abundance of Butyrivibrio was lower (p = 0.031) in the C30 group, and that of Ruminococcus was higher (p = 0.003) in the C70 group compared with the C50 group. In feces, genus Monoglobus and UCG_002 were the most abundant in the C30 group (p < 0.05), and the relative abundance of Prevotella was significantly higher in the C70 group than in other groups (p = 0.013). Correlation analysis revealed possible links between slaughter performance and meat quality and altered microbiota composition in the rumen and feces of Tibetan sheep. Overall, feeding a C70 diet resulted in superior carcass characteristics and meat quality in Tibetan sheep, thus laying a theoretical basis for the application of short-term remote feeding during the cold season. Full article

The zygomatic bone, a fundamental structure in facial anatomy, is exposed to fractures in impact situations, such as traffic accidents or contact sports. The installation of zygomatic implants can also alter the distribution of forces in this region, increasing the risk of fractures. To evaluate this situation, the first step is to develop a complex anatomical model from the stomatognathic point of view so that simulations in this sense can be validated. This study uses numerical simulation using a finite-element method (FEM) to analyze the behavior of the zygomatic bone under impacts of different velocities, offering a more realistic approach than previous studies by including the mandible, cervical spine, and masticatory muscles. Methods: An FEM model was developed based on 3D scans of actual bones, and simulations were performed using Abaqus Explicit 2023 software (Dassault Systemes, Vélizy-Villacoublay, France). The impact was evaluated using a steel cylinder (200 mm length, 40 mm diameter, 2 kg weight) impacted at speeds of 5, 10, 15, and 20 km/h. Zygomatic, maxillary, and mandibular bone properties were based on dynamic stiffness parameters, and bone damage was analyzed using ductile fracture and fracture energy criteria. Results: The results show that at impact velocities of 15 and 20 km/h, the zygomatic bone suffered crush fractures, with impact forces up to 400 kg. At 10 km/h, a combination of crushing and bending was observed, while at 5 km/h, only local damage without complete fracture was detected. The maximum stresses were concentrated at the zygoma–jaw junction, with values above 100 MPa at some critical points. Conclusion: The FEM model developed offers a detailed representation of the mechanical behavior, integrating the main structures of the stomatognathic apparatus of the zygomatic bone under impact, providing valuable information to, for example, advance injury prevention and zygomatic implant design. Higher impact velocities result in severe fractures, underscoring the need for protective measures in clinical and sports settings. Full article

Beef carcass aging, which enhances tenderness and flavor through proteolysis, is traditionally costly and slow, requiring long-term storage at temperatures near 0 °C. To reduce energy consumption, a new technique using moderate cooling room temperatures was tested. Six carcasses of Holstein bulls were used. From each carcass, two shoulders were processed in different ways: one was refrigerated at 8 °C (W), and after spraying with a solution with calcium chloride and sodium chloride, was coated with sodium alginate. The other shoulder was stored at 2 ± 1 °C as a cold control (C). After five days of aging, the shoulders were dissected, and two muscles (Caput longum triceps brachii and Supraspinatus) were subjected to physico-chemical analysis, microbiological safety assessment, and sensory testing. The remaining samples of both muscles were stored in domestic conditions for an additional 5 days at various temperatures (2, 4, 8 °C), where the same physic-chemical and sensory tests were conducted. The results showed that moderate aging temperature improved meat quality, significantly reducing the shear force (p = 0.001) and increasing sarcomere length, the myofibrillar fragmentation index, and sensory tenderness (p = 0.042, p = 0.039, and p = 0.027, respectively). However, domestic storage post-dissection should not exceed 4 °C to prevent rapid lipid oxidation, as observed at 8 °C for both muscles (p < 0.001). Mild aging temperature maintained legal safety standards, enhanced certain meat qualities, and promoted enzymatic activity similar to traditional dry aging while reducing high energy consumption. Full article

This experiment aimed to explore the effects of flavonoids in Fructus Aurantii Immaturus (FFAI) on carcass traits, meat quality, and the antioxidant capacity of finishing pigs. The results indicated that the addition of an appropriate amount of FFAI into their diet could significantly reduce the backfat thickness and perirenal fat percentage of finishing pigs, as well as the drip loss, water-holding capacity, shear force, and the levels of lactate, glucose-6-phosphate, glucose, ATP, phosphofructokinase, and pyruvate in the longissimus dorsi (LD) muscle. It also elevated the levels of flavor amino acids such as glutamate, serine, and threonine, and enriched the composition of flavor substances, including benzene and octanal, which significantly contributed to the enhancement of pork flavor. Furthermore, it enhanced the expression levels of MyHC I and MyHC IIa. In summary, the appropriate addition of FFAI to the diet could improve the carcass traits, meat quality, and antioxidant capacity of finishing pigs. The optimal level of FFAI supplementation is 0.12%. Full article

Custom implants used for pelvic reconstruction in pelvic sarcoma surgery face a high complication rate due to mechanical failures of fixation screws. Consequently, patient-specific finite element (FE) models have been employed to analyze custom pelvic implant durability. However, muscle forces have often been omitted from FE studies of the post-operative pelvis with a custom implant, despite the lack of evidence that this omission has minimal impact on predicted bone, implant, and fixation screw stress distributions. This study investigated the influence of muscle forces on FE predictions of fixation screw pullout and fatigue failure in a custom pelvic implant. Specifically, FE analyses were conducted using a patient-specific FE model loaded with seven sets of personalized muscle and hip joint contact force loading conditions estimated using a personalized neuromusculoskeletal (NMS) model. Predictions of fixation screw pullout and fatigue failure—quantified by simulated screw axial forces and von Mises stresses, respectively—were compared between analyses with and without personalized muscle forces. The study found that muscle forces had a considerable influence on predicted screw pullout but not fatigue failure. However, it remains unclear whether including or excluding muscle forces would yield more conservative predictions of screw failures. Furthermore, while the effect of muscle forces on predicted screw failures was location-dependent for cortical screws, no clear location dependency was observed for cancellous screws. These findings support the combined use of patient-specific FE and NMS models, including loading from muscle forces, when predicting screw pullout but not fatigue failure in custom pelvic implants. Full article

The effects of heat stress on aquatic animals are increasingly being discerned, but little is known about the effects of heat stress on muscle meat quality or the flavor of muscle. This study aimed to evaluate the effects of heat stress on the muscle antioxidant properties, structural and physical properties (e.g., pH, muscle color, shear force, and expressible moisture), chemical composition (e.g., nucleotides, organic acids, amino acids, and minerals), and volatile substances of rainbow trout. We observed that the antioxidant capacity of muscle decreased after stress experiments at 22.5 °C for 24 h. The content of inflammatory factors notably increased (p < 0.05), the pH value and red value of muscle decreased (p < 0.05), the interfiber space increased, and several muscle fibers were broken. Heat stress changed the contents of nucleotides, organic acids, minerals, and amino acids in muscle. The contents of IMP and AMP, which play an important role in the flavor of muscle, decreased (p < 0.05). The contents of two amino acids that provide a sweet taste decreased; those of five amino acids that provide a bitter taste increased (p < 0.05). Heat stress also affected the amount and type of volatile substances in muscle, which affected muscle odor. These results suggest that heat stress may exert adverse effects on the oxidative stability, structure, meat quality, and flavor of muscle, requiring attention and prevention. Full article

Our investigation demonstrates the necessity of mathematical modeling and design methodologies for nerve signals in the creation of artificial arms. Nerve impulses vary widely in speed; for example, unmyelinated nerves transmit impulses at around one mile per hour, while myelinated nerves conduct impulses at around 200 miles per hour. The electrical signals originating from the brain, such as those measured by electroencephalography, are translated into chemical reactions in each organ to produce energy. In this paper, we describe the mechanism by which nerve signals are transferred to various organs, not just the brain or spinal cord, as these signals account for the measured amounts of physical force—i.e., energy—as nerve signals. Since these frequency signals follow no fixed pattern, we consider wavelength and amplitude over a particular time frame. Our simulation results begin with the mechanical distinction that occurs throughout the entire process of nerve signal transmission in the artificial arm as an artificial biological system, and show numerical approaches and algebraic equations as a matrix in mathematical modeling. As a result, the mathematical modeling of nerve signals accurately reflects actual human nerve signals. These chemical changes, involving K (potassium), Na (sodium), and Cl (chloride), are linked to muscle states as they are converted into electrical signals. Investigating and identifying the neurotransmitter signal transmission system through theoretical approaches, mechanical analysis, and mathematical modeling reveals a strong relationship between mathematical simulation and algebraic matrix analysis. Full article

Store-operated Ca²⁺ entry (SOCE) controls Ca²⁺ homeostasis and mediates multiple Ca²⁺-dependent signaling pathways and cellular processes. It relies on the concerted activity of the reticular Ca²⁺ sensor STIM1 and the plasma membrane Ca²⁺ channel ORAI1. STIM1 and ORAI1 gain-of-function (GoF) mutations induce SOCE overactivity and excessive Ca²⁺ influx, leading to tubular aggregate myopathy (TAM) and Stormorken syndrome (STRMK), two overlapping disorders characterized by muscle weakness and a variable occurrence of multi-systemic anomalies affecting spleen, skin, and platelets. To date, different STIM1 mouse models exist, but only a single ORAI1 mouse model with muscle-specific TAM/STRMK phenotype has been described, precluding a comparative analysis of the physiopathology in all affected tissues. Here, we generated and characterized mice harboring a prevalent ORAI1 TAM/STRMK mutation and we provide phenotypic, physiological, biochemical, and functional data. Examination of Orai1^V109M/+ mice revealed smaller size, spleen enlargement, reduced muscle force, and decreased platelet numbers. Morphological analyses of muscle sections evidenced the presence of tubular aggregates, the histopathological hallmark on biopsies from TAM/STRMK patients absent in all reported STIM1 models. Overall, Orai1^V109M/+ mice reliably recapitulate the human disorder and highlight the primary physiological defects caused by ORAI1 gain-of-function mutations. They also provide the possibility to investigate the formation of tubular aggregates and to develop a common therapy for different TAM/STRMK forms. Full article

This study used a 12-week plyometric and strength training program as an intervention to improve upper- and lower-extremity muscle strength for jumping and landing when climbing high walls. Sixty general non-athlete male college students were openly recruited and divided into an experimental group and a control group. The experimental group underwent a plyometric and strength training program twice a week for 12 weeks (24 sessions). The intervention was divided into three phases, each lasting four weeks, with the training intensity gradually increasing in each phase. A hand grip dynamometer was used to measure grip strength, and a PASCO double-track force plate was used to assess upper-extremity push-up force and lower-extremity take-off and landing strength. The results of the 12-week intervention showed that the experimental group experienced significant increases in grip strength (both hands), hand-ground reaction force, and upper-extremity hang time. Additionally, the time of upper-extremity action on the force plate decreased. Lower-extremity take-off strength improved, as reflected in increased ground reaction force, rate of force development, and passage time. Upon landing, ground reaction force decreased by 3.2%, and cushioning time shortened by 52.7%. This study concludes that plyometric and strength training have promising effects in enhancing upper- and lower-extremity strength, particularly in climbing and landing tasks. Full article

Objectives: The purpose of this study was to examine the acute effects of branched-chain amino acids (BCAAs)-containing electrolyte beverage (AE) on water–electrolyte balance, muscle damage, time to finish the final 5 km, and muscle strength compared to a standard commercially available carbohydrate–electrolyte sports beverage (CE), pure water (W), and no rehydration (N). Methods: Fourteen trained male participants (20 ± 2 years old) completed four randomized 21 km running trials. The participants were instructed to consume their drink (150 mL W, 150 mL CE, or 150 mL AE) or no rehydration (N) at 5 km, 10 km, and 15 km. Body mass and muscle strength were assessed, and blood samples were collected before and after exercise. Perceptual scales were administered during and after running. Blood electrolyte levels (sodium, potassium, and chloride) and creatine kinase (CK) concentration were analyzed. Results: The change in plasma volume with AE was significantly smaller than that with N (p < 0.05). Consuming AE maintained the best potassium balance (p < 0.05). Twenty-four hours after exercise, serum CK concentrations significantly elevated in N, W, and CE (p < 0.05), but did not reach statistical significance in the AE group (p > 0.05). Compared to N, consuming AE resulted in significantly less soreness 24 h after exercise (p < 0.05). There was no difference in time to finish the final 5 km (p > 0.05). Maximal voluntary isometric force output was significantly lower after exercise with N and W (p < 0.05) but not with CE or AE (p > 0.05). Conclusions: Consuming a BCAAs-containing sports beverage during a 21 km run can help reduce dehydration, maintain potassium balance, lower muscle damage, and prevent the decline in lower limb strength after 21 km running. Full article

Objectives: This study aimed to assess the impact of a 20-week resistance training program on force–velocity (F-V) parameters using an isokinetic two-point method and comparing one-repetition maximum (1-RM) methods in novice lifters. Methods: Previously untrained individuals completed a supervised, three-session weekly resistance training program involving concentric, eccentric, and isometric phases, repeated every 2 to 4 weeks. Isokinetic dynamometry measured the strength of elbow flexors/extensors at 60°/s and 150°/s, and knee flexors/extensors at 60°/s and 240°/s at Baseline, 3 months, and 5 months. F-V parameters, including maximal theoretical force (F0) and the F-V slope, were calculated. Participants also performed 1-RM tests for the upper and lower limbs. Repeated measures ANOVA with effect size (η² > 0.14 as large) was used to analyze changes in F-V parameters and repeated measures correlation was used to test their association with 1-RM outcomes. Results: Eighteen male participants (22.0 ± 3.4 years) were analyzed. F0 significantly increased for all muscle groups (η² = 0.423 to 0.883) except elbow flexors. F-V slope significantly decreased (steeper) for knee extensors and flexors (η² = 0.348 to 0.695). Knee extensors showed greater F0 gains and steeper F-V slopes than flexors (η² = 0.398 to 0.686). F0 gains were associated with 1-RM changes (r = 0.38 to 0.83), while F-V slope changes correlated only with lower limb 1-RM (r = −0.37 to −0.68). Conclusions: The 20-week resistance training program significantly increased F0 and shifted the F-V profile towards a more “force-oriented” state in knee muscles. These changes correlated with improved 1-RM performance. Future studies should include longer follow-ups and control groups. Full article

Background: the effects of gait training based on the positioning of affected foot muscle activity, gait parameters, and balance ability were investigated in patients with subacute stroke. Material and Methods: Forty-five patients with subacute stroke were randomly assigned to three groups: straight gait training (SGT) group (n = 15), outward curved gait training group (OCGT) with the paretic foot positioned laterally (n = 15), or inward curved gait training (ICGT) group with the paretic foot positioned medially (n = 15). All groups received 30 min interventions, comprising 15 min of gait training, five times per week for four weeks. Outcomes were measured in terms of muscle activation of the gluteus maximus (GM), vastus medialis, and vastus lateralis; five gait parameters (step length, stance phase, swing phase, velocity, and maximum force); and balance ability assessed using the timed up and go (TUG) test. Results: All groups exhibited significant improvements in all variables after the four-week intervention period (p < 0.05). Specifically, the overall muscle activation and gait parameters for each group increased as follows: the SGT showed increases of 38.8% and 5.7%, respectively; the OCGT exhibited improvements of 38.9% and 7.4%; and the ICGT demonstrated enhancements of 59.8% and 9.2%. However, except for comparisons between the SGT and ICGT groups in terms of GM muscle activity and TUG, no significant differences were observed between the groups for the other variables (p > 0.05). Conclusions: although patients with subacute stroke can improve their overall physical function regardless of the gait training method, ICGT may be more effective in enhancing muscle activity and balance ability. Full article

The trampoline is a popular piece of sports equipment both for recreational use and for Olympic trampolining as a competitive sport. Maintaining body position during jumps is influenced by sensory inputs (visual, auditory, and somatosensory) and symmetrical muscle activity that help athletes to perform consecutive jumps as vertically as possible. To evaluate the effects of these inputs, 15 male and 15 female students (with an average age of 24.4 years, height of 174.3 cm, and average weight of 69.7 kg) performed 10 consecutive straight jumps under four sensory conditions: (1) looking at the edge of the trampoline, (2) without sight, (3) without hearing, and (4) without hearing or sight. Using insoles with integrated pressure sensors (Pedar^®, novel GmbH, Munich, Germany), the contact forces on the trampoline during the jump were measured separately for the left and right feet. The results showed that the lack of visual input significantly shortened flight times and increased the asymmetry of ground reaction forces between the left and right legs. For example, in the second series without vision, the average normalized force difference between the legs increased by 0.33 G compared to the control condition. An ANOVA revealed significant differences in the ground reaction forces between sensory conditions, with vision playing a key role in maintaining body control. These results provide practical insights for coaches looking to improve jumping performance and address asymmetries during training by focusing on sensory feedback strategies. Full article

Preparation of athletes to begin a competition or enter mid-competition with the ability to reach peak performance immediately may be partly dependent on the efficacy of the warmup protocol. Previous research on flexible barbells reported significant differences in muscle activation when compared to steel barbells. The manufacturers of handheld flexible bars with a combined weight of 3.63 kg claim that using them immediately before competition helps increase power and jump height. The purpose of the study was to determine the effects of maximal jumping with handheld flexible bars on maximal jump parameters in Division-I American collegiate football players. Participants completed 10 warmup jumps with no weight, flexible barbells, or similarly weighted dumbbells and immediately completed a maximal countermovement jump. When comparing the effects of different high-velocity warmup (HVW) protocols, there were no differences in any jump parameters as measured by a portable force plate. Likewise, the use of flexible bars during the warmup did not result in enhanced muscle activity when executing a maximal jump in comparison to control conditions. Based on these results there is no evidence to support the use of flexible bars during a warmup just prior to entry into a competition to enhance jumping power. Full article