Fatigue Index Research Articles

Insight into motor fatigue mechanisms in natalizumab treated multiple sclerosis patients with wearing off

Motor fatigue in Multiple Sclerosis (MS) is due to reduced motor cortex (M1) output and altered sensorimotor network (SMN) modulation. Natalizumab, a disease-modifying therapy, reduces neuroinflammation and improves fatigue. However, some patients treated with natalizumab experience fatigue recurrence (‘wearing-off’) before subsequent infusions. Wearing-off provides a valuable window into MS-related motor fatigue mechanisms in a controlled, clinically stable, setting. This study investigates whether wearing-off is associated with worsening motor fatigue and its neurophysiological mechanisms and assesses natalizumab’s effect on MS-related fatigue. Forty-five relapsing–remitting MS patients with wearing-off symptoms were evaluated pre- and post-natalizumab infusion. Assessments included evaluating disability levels, depressive symptoms, and the impact of fatigue symptoms on cognitive, physical, and psychosocial functioning. The motor fatigue index was computed through the number of blocks completed during a fatiguing task and peripheral, central, and supraspinal fatigue (M1 output) were evaluated by measuring the superimposed twitches evoked by peripheral nerve and transcranial magnetic stimulation of M1. Transcranial magnetic stimulation-electroencephalography assessed M1 effective connectivity by measuring TMS-evoked potentials (TEPs) within the SMN before- and after the task. We found that wearing-off was associated with increased motor fatigue index, increased central and supraspinal fatigue, and diminished task-related modulation of TEPs compared to post-natalizumab infusion. Wearing-off was also associated with worsened fatigue impact and depression symptom scores. We conclude that the wearing-off phenomenon is associated with worsening motor fatigue due to altered M1 output and modulation of the SMN. Motor fatigue in MS may reflect reversible, inflammation-related changes in the SMN that natalizumab can modulate. Our findings apply primarily to MS patients receiving natalizumab, emphasizing the need for further research on other treatments with wearing-off.

Voice Disorder Prevalence and Vocal Health Characteristics in Adolescents

Voice disorders impede communication and detract from quality of life, yet little is known about how voice problems present in adolescents. This study characterized the prevalence of voice problems and vocal health characteristics of adolescents throughout the US. To determine the prevalence of adolescent voice problems in the US as well as the symptoms, voice use patterns, and risk factors associated with these problems. This prospectively performed, cross-sectional survey study conducted from March to June 2023 included a probability sample of adolescents (aged 13-17 years) who were located across the US. Adolescents were surveyed concerning voice use, voice symptoms, demographic information, and substance use patterns. The Vocal Fatigue Index (VFI) was also completed. Fisher exact tests, χ2 tests, and logistic regression were used to compare those with and without reported voice problems. Five-hundred and two adolescents participated (51.6% participation rate), including 248 female (49.4%), 7 nonbinary (1.3%), 254 male (50.6%), 4 transfemale (0.7%), and 3 transmale individuals (0.5%) (mean [SD] age, 15.2 [1.3] years). The lifetime prevalence of voice problems was 24.3%, and current prevalence was 7.4%. Voice-related diagnoses included dysphonia associated with acute illness, vocal hyperfunction, benign lesions, and muscle tension. The mean (SD) VFI score was 4.7 (8.09) for part 1, 1.6 (3.2) for part 2, and 2.1 (3.2) for part 3. Adolescents with voice complaints presented with significantly higher VFI scores than those without voice problems (Cohen d for part 1 = 0.78, part 2 = 0.59, and part 3 = 0.79). Voice problems interfered with daily tasks, prevented participation in extracurricular activities, limited the ability to sing, and were associated with school absences. Voice use patterns associated with voice problems included frequent loud voice use, coughing, and/or throat clearing. Risk factors for increased voice problem prevalence included part-time employment in childcare (odds ratio [OR], 6.4; 95% CI, 1.6-26.3), singing (OR, 2.08; 95% CI, 1.3-3.1), performance-related extracurricular activities (ie, musical theater [OR, 2.67; 95% CI, 1.1-6.6 ], karaoke [OR, 3.08; 95% CI, 1.3-6.9]), vaping (OR, 1.99; 95% CI, 1.1-3.5), and/or secondhand smoke exposure (OR, 1.83; 95% CI, 1.2-2.7). Adolescents identifying as transgender were more than 4 times (OR, 4.44; 95% CI, 0.63-31.2) as likely to report voice problems compared with cisgender adolescents. The results of this survey study illuminate the nature of voice problems in adolescents and may guide clinicians in preventing and treating voice disorders in this population. Future work may define the mechanisms through which these factors are associated with the risk for voice disorders in adolescents and determine whether observed relationships are causal or associative.

Performing Lower-Limb Strength Exercises Before or After Training Does not Influence Fatigue Indices in Competitive Youth Soccer Players.

Gantzer, C, Huff, D, Butterick, B, Chalmers, S, Marshall, P, Lovell, R, and Siegler, JC. Performing lower-limb strength exercises before or after training does not influence fatigue indices in competitive youth soccer players. J Strength Cond Res XX(X): 000-000, 2024-A multicenter approach was used to conduct a controlled, laboratory-based study (Part A) in conjunction with an ecologically focused, field-based study (Part B) of the influence of timing on hamstring fatigue induced by lower-limb strength exercises. Part A required players to perform the FIFA 11+ warm-up before a simulated soccer training session, whereas the other session involved removing the lower-limb strength exercises from the warm-up and delivering them after the simulated session. For Part B, players completed 2 live training sessions, where one session included the Nordic hamstring exercise (NHE) as part of a standardized warm-up before training and the other session incorporated the NHE at the end of training. Maximal hamstring force (MVC), rate of force development (RFD), countermovement jump (CMJ), and sprint speed (SS) were assessed before, during, and after the simulation and field training, respectively, to quantify fatigue across both study cohorts. There was no suggestion that timing of the intervention had an influence fatigue in either Part A or B, with no condition (MVC [Part A & B]: p > 0.43; RFD: p = 0.43; CMJ: p = 0.10; SS: p = 0.62), time (MVC: p > 0.30; RFD: p = 0.72; CMJ: p = 0.87; SS: p = 0.85), or interactions (MVC: p > 0.93; RFD: p = 0.78; CMJ: p = 0.99; SS: p = 0.94) evident. Our findings suggest youth soccer coaches should not be concerned with the timing of interventions, allowing them to focus instead on adherence and player buy-in.

Unveiling vocal profiles in adolescent anorexia nervosa: a Software Based, Multiparametric Analysis.

Dysphonia, characterized by disturbances in voice quality and modulation, has been sporadically observed in individuals with Anorexia Nervosa (AN), potentially stemming from both organic and psychopathological factors. This study seeks to employ software-based voice analysis to compare the voices of girls with AN to those of female healthy controls (HC). Case-control study adopting "Praat" software to assess voices. Various parameters, including Acoustic Voice Quality Index (AVQI), Fundamental Frequency (F0), Yanagihara's Spectrographic Dysphonia Classifications, and "GIRBAS" perceptual qualitative voice rating, were investigated. Participants completed questionnaires for Vocal Fatigue Index (VFI) and the Reflux Symptoms Index (RSI). Puberty-related voice spectrum changes were considered, and Bonferroni-corrected BMI-adjusted Analyses of Covariance (ANCOVAs) were conducted. The study enrolled 15 girls with AN and 23 girls with HC. AN patients demonstrated greater impairment in voice tiredness/voice avoidance (VFI-1, p < 0.001), vocal physical discomfort (VIF-2, p = 0.002), and rest as alleviation (VFI-3, p = 0.012). Reflux-related scores were higher in AN (p < 0.001). Differences were observed in voice quality (AVQI) (p = 0.001), and GIRBAS scales showed alterations in multiple parameters. Spectrograms documented more frequent pathological findings in AN patients (p = 0.021). No difference was observed in Fundamental Frequency. These group (AN/HC) differences were independent of weight measures. This study is the first to connect voice irregularities in AN by employing standardized, non-invasive tools and accounting for weight-related factors. Young AN patients demonstrated substantial voice quality changes and heightened self-reported symptoms. Future research should expand on these findings with prospective designs and invasive investigations.

Hydrogen-Rich Gas Enhanced Sprint-Interval Performance: Metabolomic Insights into Underlying Mechanisms.

(1) Background: The diversity of blood biomarkers used to assess the metabolic mechanisms of hydrogen limits a comprehensive understanding of its effects on improving exercise performance. This study evaluated the impact of hydrogen-rich gas (HRG) on metabolites following sprint-interval exercise using metabolomics approaches, aiming to elucidate its underlying mechanisms of action. (2) Methods: Ten healthy adult males participated in the Wingate Sprint-interval test (SIT) following 60 min of HRG or placebo (air) inhalation. Venous blood samples were collected for metabolomic analysis both before and after gas inhalation and subsequent to completing the SIT. (3) Results: Compared with the placebo, HRG inhalation significantly improved mean power, fatigue index, and time to peak for the fourth sprint and significantly reduced the attenuation values of peak power, mean power, and time to peak between the first and fourth. Metabolomic analysis highlighted the significant upregulation of acetylcarnitine, propionyl-L-carnitine, hypoxanthine, and xanthine upon HRG inhalation, with enrichment pathway analysis suggesting that HRG may foster fat mobilization by enhancing coenzyme A synthesis, promoting glycerophospholipid metabolism, and suppressing insulin levels. (4) Conclusions: Inhaling HRG before an SIT enhances end-stage anaerobic sprint capabilities and mitigates fatigue. Metabolomic analysis suggests that HRG may enhance ATP recovery during interval stages by accelerating fat oxidation, providing increased energy replenishment for late-stage sprints.

Platelet Rich plasma injection of the vocal folds in benign vocal pathologies

PurposeThere are few options for treatment of dysphonia secondary to vocal pathology related to lamina propria scar, atrophy, sulcus, or inflammatory disorders. Platelet rich plasma (PRP) may provide anti-inflammatory and regenerative properties seen with other tissue engineering therapies without the risks associated with these treatments. We evaluated vocal fold (VF) injection of PRP for feasibility, phonatory effects, patient satisfaction and durability.MethodsPatients with dysphonia secondary to vocal fold scar, atrophy, sulcus and inflammatory lesions were included. PRP injections were administered in office, to bilateral vocal folds. Patients were followed up at 1 week, 1 month, 3 months and 6 months to assess outcomes (GRBAS scale, maximum phonation time, vocal fatigue index (VFI), voice handicap index (VHI-10) and stroboscopy).Results75 intracordal PRP injections were administered to 48 patients. All injections were completed, and no adverse reactions were experienced. Improvements in VHI-10 scores at 1,3,6 months were seen (mean VHI 21.73 at baseline, 15.62 at six months, p < 0.001). 72.3% rated improvement at 7 or above on Likert scale. 95.7% of patients would consider a future PRP injection. Secondary outcomes VFI, MPT, and GRBAS also demonstrated significant improvements over time. Patients receiving a single PRP injection (n = 26) still demonstrated significant VHI-10 improvements at 1,3 and 6 months.ConclusionsVF office PRP injections are feasible and safe and can provide phonatory benefit and reduce vocal effort in benign VF disorders. A single PRP injection is sufficient to provide sustained benefit in some cases.Level of evidenceLevel III: prospective cohort study.

Validity and Reliability of the German Vocal Fatigue Index in Adults With Voice Disorders.

Vocal fatigue-related symptoms, frequent in patients with voice disorders, are reliably quantifiable with the Vocal Fatigue Index (VFI) in several languages. The main aim of this work was to investigate the content and construct validity of the German Vocal Fatigue Index (VFI-D) by comparison with the German Voice Handicap Index 9 international (VHI9i) and the Vocal Tract Discomfort Scale (VTD). Moreover, the scale and retest reliability were investigated. In a prospective cohort study at two tertiary care hospitals, 93 adults with all types of voice complaints filled out the VFI-D, the VHI-9i, and the VTD. Eighty-one adults (Mage = 53.5 years, SD = 15.7) completed them one time, and additional 12 patients (Mage = 53.8 years, SD = 15.6) did a test-retest, completed them twice at an interval of 1 week. The validity was assessed by Spearman's rho and Mokken scaling and the reliability by a factor analysis and a two-tailed t test. Mokken scaling has proven the VFI-D as one-dimensional questionnaire (one cluster, r = .95). All VFI-D items could be assigned to one of three factors according to principal component and principal axis factor analysis. Although Factor 1 related best to the VHI9i (∅ rs = .76) and Factor 2 to the VTD (∅ rs = .74), Factor 3 correlated moderately with the VHI9i (rs = .34) and weakly with the VTD (rs = .25). Results from the first and second VFI-D completion agreed strongly (t = -1.78, p = .10). In this study, the content and construct validity of the VFI-D were confirmed. Also, both scale reliability with identical factors as those in the original study and retest reliability were verified. The VHI9i and VTD were highly indicative of VFI-D Factors 1 and 2, respectively. No correlation between Factor 3 and the other questionnaires was determined. Future research should evaluate which characteristics are specific to vocal fatigue versus general voice disorder-related symptoms.

Between-day reliability of common muscle fatigue measures during a repeated upper limb fatigue protocol

Neuromuscular fatigue manifestation is of interest in both basic neurophysiological and applied (e.g. sporting, ergonomics) contexts. A unique challenge in fatigue research is that experimental sessions often need to be collected across many days to allow for adequate recovery. The purpose of this study was to examine the between-day reliability of several surface electromyography- and strength-based fatigue measures in response to a repeated fatigue protocol. Twenty participants (10 M, 10 F) performed an isometric elbow flexion fatigue protocol on three different days. The reliability of commonly used amplitude- and frequency-based myoelectric and performance-based indicators of fatigue were assessed using traditional reliability assessment methods. Baseline MVC strength (N) demonstrated excellent between-day reliability (ICCA, 1: 0.96, 95%CI[0.92, 0.98]) with good absolute reliability (SEM: 5.10%, MD95: 14.1%). The absolute reliability of all slope-based fatigue measures was low. However, %MVC Slope (ICC: 0.67, [49, .82]), %MnPF Slope (ICC: 0.75, [.60, .87]), and endurance time (ICC: 0.60, [0.39, 0.77]) had poor/moderate to good relative reliability. Baseline MVC strength was shown to be very repeatable between days. Caution is recommended when using slope-based fatigue measures for cyclic repetitive upper limb tasks, as slope-based measures of muscle fatigue were shown to have low between-session reliability.

Activation of α7 Nicotinic Acetylcholine Receptor Improves Muscle Endurance by Upregulating Orosomucoid Expression and Glycogen Content in Mice.

There are presently no acknowledged therapeutic targets or official drugs for the treatment of muscle fatigue. The alpha7 nicotinic acetylcholine receptor (α7nAChR) is expressed in skeletal muscle, with an unknown role in muscle endurance. Here, we try to explore whether α7nAChR could act as a potential therapeutic target for the treatment of muscle fatigue. Results showed that nicotine and PNU-282987 (PNU), as nonspecific and specific agonists of α7nAChR, respectively, could both significantly increase C57BL6/J mice treadmill-running time in a time- and dose-dependent manner. The improvement effect of PNU on running time and ex vivo muscle fatigue index disappeared when α7nAChR deletion. RNA sequencing revealed that the differential mRNAs affected by PNU were enriched in glycolysis/gluconeogenesis signaling pathways. Further studies found that PNU treatment significantly elevates glycogen content and ATP level in the muscle tissues of α7nAChR+/+ mice but not α7nAChR-/- mice. α7nAChR activation specifically increased endogenous glycogen-targeting protein orosomucoid (ORM) expression both in vivo skeletal muscle tissues and in vitro C2C12 skeletal muscle cells. In ORM1 deficient mice, the positive effects of PNU on running time, glycogen and ATP content, as well as muscle fatigue index, were abolished. Therefore, the activation of α7nAChR could enhance muscle endurance via elevating endogenous anti-fatigue protein ORM and might act as a promising therapeutic strategy for the treatment of muscle fatigue.

A two-scale approach for assessing the role of defects in fatigue crack nucleation in metallic structures

Metal structures often exhibit macroscopic defects from which cracks can nucleate during cyclic loading. The current work presents a two-scale approach to enable the prediction of crack nucleation from such defects by taking into account local microstructure features. The geometrical description of the defect and associated non-homogeneous strain fields are modeled using a macroscale model which employs a continuum elastoplastic material model for cyclic deformation. The cyclic deformation of the microstructure near the defect is modeled using a mesoscale model which employs a crystal plasticity material model and uses multiple realizations to address the statistical microstructure variability. The boundary conditions of the mesoscale model are extracted from the macroscale model. By simulating the deformation of the microstructure using the strain fields near the defect and by introducing a fatigue indicator parameter for crack nucleation, along with the weakest-link based upscaling methodology, the developed approach enables the prediction of the distribution of crack nucleation life. The approach is used for analyzing different defects for crack nucleation by considering local grain orientations. The predictions are shown to not only capture phenomena such as scatter, size effects, etc. qualitatively, but also agree with a classical engineering approach and experimentally reported data sets quantitatively.

Analysis of rolling contact and tooth root bending fatigue in a new high-strength steel: Experiments and micromechanical modelling

To find materials that meet the future requirements of increasing load density in wind turbine gear structures, the commonly used reference material, 18CrNiMo7-6, and another high-strength steel were analysed. Their fatigue properties were studied through rolling contact fatigue (RCF) and gear tooth root bending fatigue (TRBF) tests. The reference steel exhibited better fatigue performance under RCF conditions compared to the new steel; however, it was outperformed by the new steel under TRBF conditions. This study aims to understand gear contact fatigue at the microscopic level, moving beyond the macroscopic focus that dominates current research literature. To establish the causal link between the varied fatigue performance observed in these materials, we proposed a multiscale modelling workflow based on crystal plasticity. This crystal plasticity framework is combined with the fatigue indicator parameter (FIP) to explore the fatigue resistance of materials subjected to RCF and TRBF conditions. Emphasis has been placed on the role of retained austenite (RA) in fatigue performance. Utilizing representative elementary volumes (REVs) generated based on statistically representative crystallographic features and measured size distribution of RA, we examined the effects of various RA levels on fatigue resistance. Our findings reveals that the fatigue damage accumulation is significantly influenced by the level of RA. Different fatigue damage accumulation behaviours were observed under RCF and TRBF conditions. These insights offer new perspectives on RA’s role in fatigue resistance and highlight its complex influence under varied loading conditions.

Determination of walking energy expenditure as an indicator of walking fatigue

Determination of walking energy expenditure as an indicator of walking fatigue

A non-antibiotic erythromycin derivative improves muscle endurance by regulating endogenous anti-fatigue protein orosomucoid in mice.

At present, there are no official approved drugs for improving muscle endurance. Our previous research found acute phase protein orosomucoid (ORM) is an endogenous anti-fatigue protein, and macrolides antibiotics erythromycin can elevate ORM level to increase muscle bioenergetics and endurance parameters. Here, we further designed, synthesized and screened a new erythromycin derivative named HMS-01, which lost its antibacterial activity in vitro and in vivo. Data showed that HMS-01 could time- and dose-dependently prolong mice forced-swimming time and running time, and improve fatigue index in isolated soleus muscle. Moreover, HMS-01 treatment could increase the glycogen content, mitochondria number and function in liver and skeletal muscle, as well as ORM level in these tissues and sera. In Orm-deficient mice, the anti-fatigue and glycogen-elevation activity of HMS-01 disappeared. Therefore, HMS-01 might act as a promising small molecule drug targeting ORM to enhance muscle endurance.

Acute ingestion of acetaminophen improves cognitive and repeated high intensity short-term maximal performance in well-trained female athletes: a randomized placebo-controlled trial

This study examined the effect of acute acetaminophen (ACTP) ingestion on physical performance during the 5 m shuttle run test (5mSRT), attention, mood states, and the perception of perceived exertion (RPE), pain (PP), recovery (PRS), and delayed onset of muscle soreness (DOMS) in well-trained female athletes. In a randomized, placebo-controlled, double-blind, crossover trial, fifteen well-trained female athletes (age 21 ± 2 years, height 165 ± 6 cm, body mass 62 ± 5 kg) swallowed either 1.5 g of ACTP or 1.5 g of placebo. The profile of mood states (POMS) and digit cancellation (DCT) were assessed 45 min postingestion, and 5mSRT was performed 60 min postingestion. The RPE and PP were determined immediately after each 30-s repetition of the 5mSRT, and the PRS and DOMS were recorded at 5 min and 24 h post-5mSRT. For the 5mSRT, ACTP ingestion improved the greatest distance (+ 10.88%, p < 0.001), total distance (+ 11.33%, p = 0.0007) and fatigue index (+ 21.43%, p = 0.0003) compared to PLA. Likewise, the DCT score was better on the ACTP (p = 0.0007) than on the PLA. RPE, PP, PRS, and DOMS scores were improved after ACTP ingestion (p < 0.01 for all comparisons) compared to PLA. POMS scores were enhanced with ACTP ingestion compared to PLA (p < 0.01). In conclusion, this study indicates that acute acetaminophen ingestion can improve repeated high intensity short-term maximal performance, attention, mood states, and perceptions of exertion, pain, recovery, and muscle soreness in well-trained female athletes, suggesting potential benefits for their overall athletic performance and mood state.

Framework and Function of Integrated Water Resources Management in Support of Sustainable Development

Sustainable Development Goal 6 addresses water issues, and Target 6.5.1 sets a goal to implement integrated water resources management (IWRM) at all levels. The reporting system shows slow progress, which indicates that changes are needed. The assessments focus mainly on the function of IWRM as a framework of institutional arrangements and less on its function as a process for water resources management, with emphasis on practices like multi-objective planning and stakeholder participation. While IWRM has a rich body of knowledge and wide recognition among water management communities, it is still misunderstood and criticized by some stakeholders, even after 25 years of explanations. While its support base appears stable, indications of fatigue and waning interest in IWRM point to the need for fresh explanations and demonstrations. These can be facilitated by distinguishing the functionalities of IWRM as a framework and a process. SDG data focuses on its framework function, which generally tracks the status of environmental governance in countries. Case studies provide better indicators of its use as a process, but their narratives may not be persuasive. If educators adopt the framework and function model of IWRM advocated in the paper, the narratives can improve and facilitate greater acceptance. Advancement of IWRM implementation to support the Sustainable Development Goals requires continued support by the Global Water Partnership, which might be bolstered by cooperation with international water associations for standardization, accreditation, and credentialing. IWRM’s future implementation will also depend on its adoption among educators and on interdisciplinary approaches.

Preventive effect of one-session brief focused attention meditation on state fatigue: Resting state functional magnetic resonance imaging study

IntroductionThe extended practice of meditation may reduce the influence of state fatigue by changing neurocognitive processing. However, little is known about the preventive effects of one-session brief focused attention meditation (FAM) on state fatigue in healthy participants or its potential neural mechanisms. This study examined the preventive effects of one-session brief FAM on state fatigue and its neural correlates using resting-state functional MRI (rsfMRI) measurements. MethodsWe randomly divided 56 meditation-naïve participants into FAM and control groups. After the first rsfMRI scan, each group performed a 10-minute each condition while wearing a functional near-infrared spectroscopy (fNIRS) device for assessing brain activity. Subsequently, following a second rsfMRI scan, the participants completed a fatigue-inducing task (a Go/NoGo task) for 60 min. We evaluated the temporal changes in the Go/NoGo task performance of participants as an indicator of state fatigue. We then calculated changes in the resting-state functional connectivity (rsFC) of the rsfMRI from before to after each condition and compared them between groups. We also evaluated neural correlates between the changes in rsFC and state fatigue. Results and discussionThe fNIRS measurements indicated differences in brain activity during each condition between the FAM and control groups, showing decreased medial prefrontal cortex activity and decreased functional connectivity between the medial prefrontal cortex and middle frontal gyrus. The control group exhibited a decrement in Go/NoGo task performance over time, whereas the FAM group did not. These results, thus, suggested that FAM could prevent state fatigue. Compared with the control group, the rsFC analysis revealed a significant increase in the connectivity between the left dorsomedial prefrontal cortex and right superior parietal lobule in the FAM group, suggesting a modification of attention regulation by cognitive effort. In the control group, increased connectivity was observed between the bilateral posterior cingulate cortex and left inferior occipital gyrus, which might be associated with poor attention regulation and reduced higher-order cognitive function. Additionally, the change in the rsFC of the control group was related to state fatigue. ConclusionOur findings suggested that one session of 10-minute FAM could prevent behavioral state fatigue by employing cognitive effort to modify attention regulation as well as suppressing poor attention regulation and reduced higher-order cognitive function.

The effects of aerobic gymnastics training on performance-related variables in an elite athlete: a 2-year follow-up study.

This study investigates individual performance adaptations on 2years of training between European Aerobics Championships. An elite, 22-year-old aerobic gymnast performed postural coordination test, Y-Balance test, squat and countermovement jumps, 60s test of repeated jumps, an isokinetic leg muscle strength test, and the Wingate test. Postural stability and flexibility improved in terms of increased distance achieved in the Y-Balance test in the anterior (by 6.3%), posteromedial (by 2%), and posterolateral (by 4.8%) directions. Lower limb muscular endurance also increased, which can be corroborated by a reduced fatigue index in the 60s test of repeated jumps (from 42% to 27% after the 1st and to 22% after the 2nd year of training). In addition, mean power increased during dominant (by 23.2% at 60°/s and by 18.5% at 180°/s) and non-dominant leg extension (by 4.9% at 180°/s and by 15.5% at 300°/s), plus dominant leg flexion (by 2.0% at 60°/s and by 6.9% at 300°/s). Similarly, peak torque/body weight ratio increased during dominant (by 24.9% at 60°/s, by 11.5% at 180°/s, and by 2.1% at 300°/s) and non-dominant leg extension (by 0.5% at 60°/s and by 6.4% at 300°/s), plus dominant leg flexion (by 1.7% at 60°/s and by 5.4% at 300°/s). However, 2years of training failed to show any significant improvements in the explosive power of lower limbs and anaerobic performance. These findings indicate that general aerobic gymnastics training without any specific inputs leads to performance adaptation, namely, in abilities closely related to competition routine (dynamic balance and strength endurance of lower limbs).

Stored energy density solution for TSV-Cu structure deformation under thermal cyclic loading based on PINN

TSV-Cu is widely used for chip interconnects, where high testing costs and complex crystal plasticity finite element (CPFE) limit the research of its deep microplastic evolution process. Considering the stored energy density (SED) based on dislocation density and plastic work as a fatigue indicator factor (FIP), this paper proposes for the first time a physics-informed neural network (PINN) framework based on SED, which aims to achieve the solution of SED distributions quickly and efficiently to save computational time and cost. The grain orientation, geometrical compatibility factor, back stress, and effective plastic strain are taken into account as inputs to the PINN model. The total dislocation density is used as an indirect solution variable to construct the associated loss boundary terms, which results in the solution of the SED. The results of the two real EBSD tests show that the PINN model is able to accurately and sensitively predict the SED concentration distribution for different thermal cycle loadings, and maintains a high degree of agreement with the CPFE calculation results. Moreover, The superiority of PINN over other machine learning algorithms in terms of physical model interpretation and prediction accuracy is verified. These make it a reality for PINN to solve for the FIP distribution for the first time, and to accurately and quickly predict the location of crack initiation.

Effect of grain orientation distribution on the mechanical properties of Al-7.02Mg-1.78Zn alloys

PurposeDuring the forming process, aluminum alloy sheets develop various types of textures and are subjected to cyclic loading as structural components, resulting in fatigue damage. This study aims to develop polycrystalline models with different orientation distributions and incorporate suitable fatigue indicator parameters to investigate the effect of orientation distribution on the mechanical properties of Al-7.02Mg-1.78Zn alloys under cyclic loading.Design/methodology/approachIn this study, a two-dimensional polycrystalline model with 150 equiaxed grains was constructed based on optical microscope images. Subsequently, six different orientation distributions were assigned to this model. The fatigue indicator parameter of strain energy dissipation is utilized to analyze the stress response and fatigue crack driving force in polycrystalline models with different orientation distributions subjected to cyclic loading.FindingsThe study found that orientation distribution significantly influences fatigue crack initiation. Orientation distributions with a larger average Schmid factor exhibit reduced stress response and lower fatigue indicator parameters. Locations with a larger average Schmid factor experience greater plastic deformation and present a higher risk for fatigue crack initiation. RVE with a single orientation undergoes more rotation to reach cyclic steady state under cyclic loading due to the ease of deformation transfer.Originality/valueCurrently, there are no reports in the literature on the calculation of fatigue crack initiation for Al-Mg-Zn alloys using the crystal plasticity finite element method. This study presents a novel strategy for simulating the response of Al-7.02Mg-1.78Zn materials with different orientation distributions under symmetric strain cyclic loading, providing valuable references for future research.

A physics‐informed neural network framework based on fatigue indicator parameters for very high cycle fatigue life prediction of an additively manufactured titanium alloy

AbstractThe exploitation of fatigue life prediction methods based on fatigue indicator parameters revealed the influence of the defect size, position, and morphology on the fatigue life and fatigue behavior of additively manufactured metals. Meanwhile, Data‐driven life prediction methods are time‐efficient but inexplainable. Current machine learning‐based fatigue life prediction methods call for not only the accuracy but also the interpretability and stability of prediction results. Thus, the fusion of physical methods and machine learning methods has been a prevailing research topic in fatigue life prediction. In this study, a novel physics‐informed neural network framework is proposed by integrating a fatigue indicator parameter based on defects into the physical constraints term of a loss function. This method outperforms conventional machine learning methods in high‐cycle and very high‐cycle regimes, exhibiting superior prediction performance and generalization ability. Furthermore, the prediction results can be explained from a physical standpoint, correlating with the applicability range of the introduced physical equation describing defect positions.