Search Results (110)

Background: Exercise-induced fatigue arises primarily from energy substrate depletion and the accumulation of metabolites such as lactate and ammonia, which impair performance and delay recovery. Emerging evidence implicates gut microbiota modulation—particularly via probiotics—as a means to optimize host energy metabolism and accelerate clearance of fatigue-associated by-products. Objective: This study aimed to determine whether live or heat-inactivated Lacticaseibacillus paracasei NB23 can enhance exercise endurance and attenuate fatigue biomarkers in a murine model. Methods: Forty male Institute of Cancer Research (ICR) mice were randomized into four groups (n = 10 each) receiving daily gavage for six weeks with vehicle, heat-killed NB23 (3 × 10¹⁰ cells/mouse/day), low-dose live NB23 (1 × 10¹⁰ CFU/mouse/day), or high-dose live NB23 (3 × 10¹⁰ CFU/mouse/day). Forelimb grip strength and weight-loaded swim-to-exhaustion tests assessed performance. Blood was collected post-exercise to measure serum lactate, ammonia, blood urea nitrogen (BUN), and creatine kinase (CK). Liver and muscle glycogen content was also quantified, and safety was confirmed by clinical-chemistry panels and histological examination. Results: NB23 treatment produced dose-dependent improvements in grip strength (p < 0.01) and swim endurance (p < 0.001). All NB23 groups exhibited significant reductions in post-exercise lactate (p < 0.0001), ammonia (p < 0.001), BUN (p < 0.001), and CK (p < 0.0001). Hepatic and muscle glycogen stores rose by 41–59% and 65–142%, respectively (p < 0.001). No changes in food or water intake, serum clinical-chemistry parameters, or tissue histology were observed. Conclusions: Our findings suggest that both live and heat-treated L. paracasei NB23 may contribute to improved endurance performance, increased energy reserves, and faster clearance of fatigue-related metabolites in our experimental model. However, these results should be interpreted cautiously given the exploratory nature and limitations of our study. Full article

This study systematically investigates 50 μm-diameter 631 stainless steel fine wires subjected to both sequential and simultaneous electrothermomechanical loading to simulate probe spring conditions in microelectronic test environments. Under cyclic current loading (~10⁴ A/cm²), the 50 μm 631SS wire maintained electrical integrity up to 0.30 A for 15,000 cycles. Above 0.35 A, rapid oxide growth and abnormal grain coarsening resulted in surface embrittlement and mechanical degradation. Current-assisted tensile testing revealed a transition from recovery-dominated behavior at ≤0.20 A to significant thermal softening and ductility loss at ≥0.25 A, corresponding to a threshold temperature of approximately 200 °C. These results establish the endurance limit of 631 stainless steel wire under coupled thermal–mechanical–electrical stress and clarify the roles of Joule heating, oxidation, and microstructural evolution in electrical fatigue resistance. A degradation map is proposed to inform design margins and operational constraints for fatigue-tolerant, electrically stable interconnects in high-reliability probe spring applications. Full article

This study introduces a time-efficient rotating bending fatigue testing system featuring 11 dual-end spindles, enabling simultaneous testing of 22 specimens. Designed for high-throughput fatigue life (S–N curve) assessment, the system theoretically allows over 93% reduction in total test duration, with 87.5% savings demonstrated in validation experiments using AISI 304 stainless steel. The PLC-based architecture provides autonomous operation, real-time failure detection, and automatic cycle logging. ER16 collet holders are easily replaceable within one minute, and all the components are selected from widely available industrial-grade parts to ensure ease of maintenance. The modular design facilitates straightforward adaptation to different station counts. The validation results confirmed an endurance limit of 421 MPa, which is consistent with the established literature and within ±5% deviation. Fractographic analysis revealed distinct crack initiation and propagation zones, supporting the observed fatigue behavior. This high-throughput methodology significantly improves testing efficiency and statistical reliability, offering a practical solution for accelerated fatigue life evaluation in structural, automotive, and aerospace applications. Full article

The design of custom abutments (CA) can affect the mechanical reliability of implant-supported restorations. The purpose of the study was to evaluate the influence of design parameters on the fatigue limit of CA and to compare optimized custom designs with the reference abutment (RA). A morse-tapered dental implant, an anatomical abutment, and a connector screw were digitalized using microcomputed tomography. A cone beam computed tomography scan was obtained from one of the authors to virtually place the implant-abutment assembly in the upper central incisor. Ten design parameters were selected according to the structural geometry of the RA and the implant planning. A reverse-engineered RA model was created in SOLIDWORKS and was modified considering a Taguchi orthogonal array to generate 36 CAs with ±20% dimensional variations. Finite element analysis was conducted in ABAQUS, and fatigue limits were estimated using Fe-safe. ANOVA (α = 0.1) identified the most influential parameters. Von Mises stress values ranged from 229 MPa to 302 MPa, and 94.4% of the CAs had a higher fatigue limit than the RA. Three parameters significantly affected the fatigue performance of the implant system. The design process of custom abutments includes critical design parameters that can be optimized for longer lifetimes of implant-abutment restorations. Full article

The investigation of the neuromuscular components of fatigue in team sports, especially in developmental ages, is limited. This study aimed to examine the neuromuscular fatigue and recovery patterns in prepubertal and adult female handball players, focusing on the soleus (SOL) and tibialis anterior (TA) muscles. Fifteen prepubertal (11.1 ± 0.9 years) and fourteen adult (22.0 ± 3.4 years) females performed a sustained isometric plantar flexion at 25% of maximal voluntary contraction (MVC) until exhaustion. The electromyographic (EMG) activity of the SOL and TA, torque, and central activation ratio (CAR) were recorded throughout the experiment. Endurance time was similar between groups (girls: 104 ± 93.5 s; women: 94.4 ± 30.2 s, p > 0.05), and both demonstrated progressive increases in muscle activation, without significant group differences for SOL and TA EMG (p > 0.05). Following fatigue, the torque and soleus (SOL) EMG activity decreased significantly compared to the pre-fatigue values in both groups (p < 0.001) and recovered (p > 0.05) in prepubertal and adult females within the first 3 and 6 min, respectively. The CAR remained unchanged over time, without significant differences observed between age groups (p > 0.05). These findings suggest that neuromuscular responses to fatigue are comparable between prepubertal and adult females, but recovery is significantly faster in prepubertal girls. Consequently, these findings underscore the need for age-specific recovery strategies in training programs, with tailored exercise-to-rest ratios to enhance performance and reduce fatigue during handball-specific activities. Full article

Introduction: Basketball performance requires not only intermittent high-intensity movements—such as sprinting, jumping, and rapid directional changes—but also rapid decision-making under cognitive and psychological stress. Transcranial direct current stimulation (tDCS) has emerged as a potential modality to enhance both physical and mental performance due to its capacity to modulate cortical excitability and promote synaptic plasticity. Although the broader literature suggests that tDCS can benefit motor performance and endurance across various sports, its specific impact on basketball remains underexplored. Methods: This scoping review aimed to summarize current evidence on the effects of tDCS in basketball. A comprehensive literature search was conducted across databases including PubMed/Medline, Google Scholar, and Cochrane, identifying studies published between January 2008 and February 2025. Only clinical trials investigating tDCS interventions in basketball players were included. Eleven articles met the inclusion criteria and were synthesized narratively, with a focus on stimulation parameters (site, duration, intensity) and performance outcomes (shooting accuracy, dribbling, sprinting, decision-making, fatigue). Results: The reviewed studies indicated that tDCS—particularly when applied over the motor cortex—was associated with moderate improvements in shooting accuracy, dribbling time, repeated-sprint performance, and decision-making under fatigue. Some studies reported delayed rather than immediate benefits, suggesting that tDCS may prime neural networks for enhanced learning and retention. However, not all findings were consistent; certain interventions produced minimal or no significant effects, especially regarding subjective mental fatigue and cognitive workload. The variability in electrode placements and stimulation protocols highlights the need for methodological standardization. Conclusions: Current evidence partially supports the potential of tDCS to improve specific performance domains in basketball, particularly in skill acquisition, neuromuscular efficiency, and decision-making. Nevertheless, the findings are limited by small sample sizes, heterogeneous protocols, and a lack of long-term follow-up. Future research should prioritize larger, multisite studies with standardized tDCS parameters and ecologically valid outcome measures to confirm the efficacy and practical relevance of tDCS in competitive basketball settings. Full article

In this study, we examine the evolution of dislocation substructures influenced by the fatigue behavior of SSM 6063 aluminum alloy processed through friction stir welding (FSW). The findings indicate that dislocation substructures have a significant impact on fatigue life. Cyclic loading induced recrystallization in the stir zone (SZ), the advancing-side thermomechanically affected zone (AS-TMAZ), and the retreating-side thermomechanically affected zone (RS-TMAZ). The transformation of the α-primary aluminum matrix phase into an S/S’ structure and the precipitation of Al₅FeSi intermetallic compounds into the T-phase were observed. Furthermore, the precipitation of Si and Mg, the primary alloying elements, was observed in the Guinier–Preston (GP) zone within the SZ. Transmission electron microscopy (TEM) analysis revealed small rod-like particles in the T-phase, measuring approximately 10–20 nm in width and 20–30 nm in length in the SZ. In the AS-TMAZ, these rod-like structures ranged from 10 to 120 nm in width and 20 to 180 nm in length, whereas in the RS-TMAZ, they varied between 10 and 70 nm in width and from 20 to 110 nm in length. The dislocation substructures influenced the stress amplitude, which was 42.46 MPa in the base metal (BM) and 33.12 MPa in the FSW-processed SSM 6063 aluminum alloy after undergoing more than 2 × 10⁶ loading cycles. The endurance limit was 42.50 MPa for BM and 32.40 MPa for FSW. Fractographic analysis of the FSW samples revealed distinct laminar crack zones and shear fracture surface zones, differing from those of other regions. Both brittle and ductile fracture characteristics were identified. Full article

Background: Guillain-Barré Syndrome (GBS) is a rare post-infectious, immune-mediated inflammatory disorder of the peripheral nervous system that can manifest in multiple distinct forms. It significantly impacts patients’ quality of life, causing both short-term and long-term impairments, including reduced strength, respiratory deficits, functional limitations, decreased endurance, and increased fatigue. This scoping review aimed to assess the impact of physical activity on strength, functional independence, and fatigue in patients with GBS, as well as to identify effective types of physical activity for rehabilitation programs. Methods: A literature search was conducted in March 2024 and updated in June 2024 across PubMed, Embase, Cochrane, Scopus, and Web of Science using predefined inclusion and exclusion criteria. We included full-text, peer-reviewed articles written in English, French, Polish, or Italian that focused on strength, fatigue, and functional independence within the context of physical exercise. Results: A total of 1021 papers were eligible for screening, and after the screening process, 16 papers were included in this review. Conclusions: Physical exercise may enhance strength, reduce fatigue, and promote functional independence in GBS. Recommended interventions often include muscle strengthening, functional training, and endurance exercises. Larger, high-quality studies and further research into chronic fatigue mechanisms are needed to refine long-term rehabilitation strategies. Full article

This study explores the fatigue properties of EN AW-6082-T6 aluminum alloy in the gigacycle range (10⁶–10⁹ cycles), using ultrasonic resonance fatigue testing at 20 kHz in a push–pull mode with a symmetric load cycle (R = −1). A custom-built ultrasonic fatigue machine, developed at TU-Varna, comprising a generator, ultrasonic train (including a high-power transducer, booster, custom-made sonotrode, and specimen), monitoring, data logging systems, and an air-cooling capability, was used for the experiments conducted. A Bezier curve sonotrode, with an amplification ratio of 1:6, was designed and produced for the test. Hourglass-shaped specimens were designed on the base of the dynamic Young’s modulus E = 71.3 GPa, determined through the impulse resonance method (ASTM E1876-01), and validated with FEM analysis for resonance length and stress amplitude. The fatigue testing revealed a fatigue strength reduction of approximately 60 MPa between 10⁶ and 10⁹ cycles. The percentile of failure curves based on a Cactillo–Canteli model fits well with the experimental data and gives a fatigue limit at 10⁹ cycles σl = 104 MPa and “endurance strength” σw = 84 MPa. Surface crack initiation was consistently observed with predominately cleavage transgranular fractures in the fatigue zone. The present research highlights the utility of ultrasonic testing for examining fatigue behavior in the gigacycle regime. Full article

Mechanical joints, regardless of materials, are useful when joining multiple components, though there are certain limits when applying them in engineering applications such as fatigue loading. The purpose of this research is to provide a comprehensive review of the trend of fatigue properties of common non-thermal mechanical connections such as adhesive, bolted, clinched and riveted joints. Towards that, a narrative approach was taken. In modern engineering applications, most of the joints contain both metallic and non-metallic components. The relevant experimental studies have proven many factors that can affect each type of joint and how they can be implemented in real-time appliances. For instance, the fatigue behaviour of adhesive joints is affected by the bond length, thickness and the use of different materials. Increasing the bond length can enhance its fatigue resistance up to a certain length, whilst increasing the thickness of laminate or adhesive decreases the fatigue life unless the surface roughness increases. On the other hand, different laminate materials can affect the fatigue performance depending on their mechanical properties. These findings will allow readers to have an overall concept of the fatigue behaviour of mechanical joints and the influence of various internal and external parameters on that. Full article

Muscle atrophy, an age-related condition, presents a growing healthcare concern within the context of global population aging. While studies have investigated Hirsutella sinensis for its potential antifatigue properties, reports on its active components remain limited. This study evaluated the efficacy of H. sinensis mycelium extract on muscle health, utilizing a 1:1 water–ethanol preparation administered to C57BL/6 mice exhibiting acute hind leg atrophy. The results indicated no adverse effects, with significant improvements in muscle endurance and soleus muscle mass observed over a 14-day period. To further elucidate the mechanisms and effects of H. sinensis mycelium on dexamethasone-induced muscle atrophy, the water extract was fractionated into components of <3.5 kDa, 3.5–10 kDa, and >10 kDa using dialysis membranes. The investigation utilized a C2C12 cell atrophy model, induced by dexamethasone, to analyze the expression of relevant genes via qPCR. The results demonstrated that the <3.5 kDa and >10 kDa fractions significantly upregulated the expression of Myh2 and Myh7 genes while simultaneously downregulating the expression of MuRF-1 and Atrogin-1. It is noteworthy that the <3.5 kDa fraction exclusively enhanced MYHC protein expression and suppressed AMPK expression, as confirmed by Western blot analysis. This comprehensive pilot study suggests that the low-molecular-weight fraction of H. sinensis mycelium exhibits considerable potential for muscle mass preservation and atrophy mitigation. As a result, it offers a promising direction for the development of supplements aimed at addressing fatigue and preventing muscle atrophy. Full article

Aluminium alloys have been one of the leading materials used in aircraft structural components due to their mechanical performance, low density, and different manufacturing and inspection techniques. The mechanical, chemical, and electrical properties of metallic alloys relate to the microstructural arrangement, which depends on the alloying elements and manufacturing parameters. Therefore, this study aims to experimentally develop an Al-2wt.%Ni-0.5wt.%Co alloy as an alternative for aerospace applications, evaluating the main metallurgical aspects influencing mechanical strength. The samples were solidified in brass moulds with four different diameters, allowing four different cooling rates. A statistical analysis of the correlation between microstructural parameters and mechanical properties is proposed to optimise the conditions for obtaining the best mechanical strength. A microstructure with an essentially cellular matrix of the α-Al phase was observed. The tensile strength limit values (σ_U) of 117 MPa, specific elongation (δ) of 13.8%, and average microhardness of 33 HV were obtained. The Al-2wt.%Ni-0.5wt.%Co alloy exhibits impressive high cycle fatigue performance, with an endurance limit of 91 MPa at 10⁷ cycles, driven by the synergistic effects of Al₃Ni for strength and Al₉Co₂ for enhanced ductility and toughness. Full article

Background: Hydrogen-rich water (HRW) has garnered significant interest within the sports and exercise science community due to its selective antioxidant properties. Despite its potential benefits, comprehensive reviews specifically addressing its effects on athletic performance are limited. This review aims to assess the impact of HRW on sports performance and explore the underlying molecular biological mechanisms, with the goal of elucidating how HRW might enhance athletic performance. Methods: This review synthesizes research on HRW by examining articles published between 1980 and April 2024 in databases such as PubMed, the Cochrane Library, Embase, Scopus, and Web of Science. Results: It highlights HRW’s effects on various aspects of athletic performance, including endurance, strength, sprint times, lunge movements, countermovement jump height, and time to exhaustion. While the precise mechanisms by which HRW affects athletic performance remain unclear, this review investigates its general molecular biological mechanisms beyond the specific context of sports. This provides a theoretical foundation for future research aimed at understanding how HRW can enhance athletic performance. HRW targets the harmful reactive oxygen and nitrogen species produced during intense exercise, thereby reducing oxidative stress—a critical factor in muscle fatigue, inflammation, and diminished athletic performance. HRW helps to scavenge hydroxyl radicals and peroxynitrite, regulate antioxidant enzymes, mitigate lipid peroxidation, reduce inflammation, protect against mitochondrial dysfunction, and modulate cellular signaling pathways. Conclusions: In summary, while a few studies have indicated that HRW may not produce significant beneficial effects, the majority of research supports the conclusion that HRW may enhance athletic performance across various sports. The potential mechanisms underlying these benefits are thought to involve HRW’s role as a selective antioxidant, its impact on oxidative stress, and its regulation of redox homeostasis. However, the specific molecular biological mechanisms through which HRW improves athletic performance remain to be fully elucidated. Full article

Background/Objectives: Low-level laser therapy (LLLT) has gained traction in sports and exercise medicine as a non-invasive therapeutic for preconditioning the body, exertion recovery, repair and injury rehabilitation. LLLT is hypothesized to modulate cellular metabolism, tissue microenvironment(s) and to decrease inflammation while posing few adverse risks. This review critically examines the evidence-base for LLLT effectiveness focusing on immediate care settings and acute/subacute applications (<6 months post-injury). Methods: A comprehensive literature search was conducted, prioritizing systematic reviews, meta-analyses and their primary research papers. Results: Findings are relevant to trainers and athletes as they manage a wide range of issues from superficial abrasions to deeper tissue concerns. LLLT parameters in the research literature include wide ranges. For body surface structures, studies show that LLLT holds promise in accelerating wound healing. In sport performance studies, LLLT is typically delivered pre-exercise and reveals beneficial effects on exertion recovery, improvements in muscle strength, endurance and reduced fatigue. Evidence is less convincing for acute, deep tissue injury models, where most studies do not report significant benefits for functional outcomes over conventional therapeutic modalities. Conclusions: Variability in LLLT delivery parameters and findings across studies underscores a need for clear treatment guidelines for the profession. Technical properties of laser light delivery to the body also differ materially from LED devices. Sport physiotherapists, team physicians, trainers and athletes should understand limitations in the current evidence-base informing photobiomodulation use in high-performance sport settings and weigh potential benefits versus shortcomings of LLLT use in the mentioned therapeutic contexts. Full article

High-strength bolts are widely used in outdoor steel structures such as transmission towers and bridges, where they not only endure cyclic wind loads and vehicle loads but also frequently operate in low-temperature environments. However, there is limited research on the axial fatigue performance of high-strength bolts, particularly regarding their mechanical behavior at low temperatures. Therefore, this study conducted a series of fatigue tests on high-strength bolts at 20 °C and 0 °C, both with and without pretension. We established S-N curves and fatigue limits for the three scenarios, revealing that pretension significantly enhances the fatigue life of the bolts, with a 10% increase in fatigue limit at 0 °C compared to 20 °C. However, due to the influence of pretension, the external load has a minimal effect on the actual stress experienced by the bolts, resulting in S-N curves for bolts with pretension being very similar to those for bolts without pretension during cyclic loading. Additionally, we obtained the load–displacement curves and corresponding stiffness degradation patterns of the bolts at both temperatures, finding that all bolts exhibited significant stiffness degradation after reaching 0.8 times their fatigue life. The high-strength bolts at 0 °C demonstrated greater stiffness and faster crack propagation rates, with increases of approximately 6% and 8%, respectively. Furthermore, electron microscope scans were used to clarify the fatigue crack initiation and the evolution of fatigue striations at both temperatures. Finally, by combining refined numerical simulations with the local stress–strain method, the effectiveness of the local stress–strain method for evaluating the fatigue life of bolts without pretension was validated. Building on this, we extended the method to bolts at 0 °C and those subjected to pretension, recommending notch sizes of 0.4 mm and 1.1 mm for fatigue life assessment of bolts with pretension at 0 °C and 20 °C, respectively. Full article