Frontiers in Physiology最新文献

{"title":"The effect of acute prolonged swimming on skeletal muscle metabolism in different muscle types of rats after nine days of dexamethasone treatment.","authors":"Damian Jozef Flis, Bartosz Cedro, Alicja Piekarska, Andzelika Borkowska, Malgorzata Halon-Golabek, Ewa Rodziewicz-Flis, Jedrzej Antosiewicz, Wieslaw Ziolkowski","doi":"10.3389/fphys.2026.1890376","DOIUrl":"10.3389/fphys.2026.1890376","url":null,"abstract":"<p><strong>Objectives: </strong>The study investigated the effec of dexamethasone (Dex) treatment, acute prolonged swimming, and their combination on skeletal muscle mass, oxidative stress, iron metabolism, and AKT-mediated signaling in two muscle types.</p><p><strong>Methods: </strong>Rats were divided into four groups (n=8 per group): intraperitoneal saline or Dex (1mg/kg/day) treatment for 9 days (non-exercised and exercised). Animals in exercise groups underwent a 4-day preparatory swimming procedure followed by a single 3h swimming session. The soleus (SOL) and extensor digitorum longus (EDL) muscles were collected, weighed, and used for analysis. We assessed lipid and protein peroxidation markers, catalase activity, iron-metabolism proteins, and AKT-dependent proteolysis and synthesis pathways.</p><p><strong>Results: </strong>Nine days of Dex treatment significantly reduced SOL (-12%, p<0.01) and EDL (-15%, p<0.001) mass, accompanied by oxidative stress (increased protein peroxidation, p<0.001) and alterations in iron metabolism: increased FH (SOL: +88%, p<0.01, EDL: +80%, p<0.01) and decreased PCBP1 (SOL: -59%, p<0.001, EDL: -33%, p<0.05). Dex treatment also affected proteins involved in synthesis and proteolysis pathways: in SOL, lowered total AKT (-22%, p<0.05) and pmTOR (-24%, p<0.05); in EDL, decreased MuRF-1 (-30%, p<0.01) and total mTOR (-24%, p<0.01), highlighting mechanisms underlying muscle loss. In saline-treated rats, acute prolonged swimming, following 4 days of preparatory exercise, did not affect SOL and EDL mass or oxidative stress markers. However, in SOL, swimming reduced PCBP1 (-43%, p<0.001), decreased total AKT (-33%, p<0.01) and pAKT (-47%, p<0.01), increased Atrogin-1 levels (+38%, p<0.001), and decreased pmTOR (-52%, p<0.001) and p70S6K levels (-47%, p<0.05). In EDL, swimming lowered MuRF-1 levels (-23%, p<0.01), indicating specific responses to exercise across muscle types. Dex-induced muscle mass loss was lower after a 4-day preparatory exercise procedure followed by prolonged exercise (p<0.001 for both muscles). Swimming in Dex-treated rats decreased pAKT (-52%, p<0.01) in SOL and increased pmTOR (+52%, p<0.01) in EDL.</p><p><strong>Conclusion: </strong>Dex treatment reduces skeletal muscle mass, regardless of fiber composition. These changes relate to oxidative stress and an imbalance in iron metabolism, but differences between muscle types in the proteolysis/synthesis signaling pathway highlight contrasting responses across muscle types. Acute prolonged swimming, preceded by a 4-day preparatory procedure, attenuates the adverse effects of Dex treatment.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1890376"},"PeriodicalIF":4.3,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13638438/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149106524","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of carbon dioxide hydrate cryotherapy on knee flexor muscle function recovery trajectory after muscle damage: a randomized controlled trial.","authors":"Rina Watabe, Daigo Shiozaki, Kohei Ono, Kosuke Hirata, Ryota Akagi","doi":"10.3389/fphys.2026.1924770","DOIUrl":"10.3389/fphys.2026.1924770","url":null,"abstract":"<p><strong>Introduction: </strong>This study investigated the effects of carbon dioxide hydrate (CDH) cryotherapy on the recovery trajectories of muscle function and physiological markers following exercise-induced muscle damage (EIMD) of the knee flexors.</p><p><strong>Methods: </strong>In a randomized parallel-group design, 24 young men were assigned to the CDH, conventional icing (ICE), or non-intervention control (CON) group (n = 8 per group). To induce muscle damage, participants performed 10 sets of eight maximal eccentric contractions of the knee flexors in a prone position (knee joint range: 75°-15° of flexion at 60°/s; 0° = the fully extended anatomical position). Maximal voluntary isometric contraction (MVIC) torque of the knee flexors was measured at 30° of knee flexion at baseline (PRE), immediately post-exercise (POST), and at 4.5, 24, 48, 72, and 168 h post-exercise. Secondary outcomes, including thigh circumference, hip joint range of motion (ROM), and hamstring muscle stiffness and pressure-induced soreness were assessed at all time points except POST. A 20-min intervention was administered after each assessment from POST to 72 h.</p><p><strong>Results: </strong>Linear mixed-effects models, adjusted for PRE values, revealed no significant group × time interactions for changes from PRE in any outcome across post-exercise time points (POST to 168 h for MVIC torque; 4.5 to 168 h for secondary outcomes; <i>p</i> = 0.177-0.914). A significant main effect of group was observed only for hip joint ROM (<i>p</i> = 0.039). <i>Post-hoc</i> comparisons revealed a significantly greater overall reduction from PRE in the CDH group than in the CON group (difference: 10.3°, 95% CI: 3.0° to 17.6°, <i>p</i> = 0.017), with no significant differences between the other group pairs (both <i>p</i> = 0.131). Given the multi-outcome testing, this isolated effect should be interpreted as exploratory.</p><p><strong>Conclusion: </strong>Under the present experimental conditions, CDH cryotherapy did not accelerate the recovery of muscle function or attenuate secondary markers following EIMD relative to conventional icing or no intervention.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1924770"},"PeriodicalIF":4.3,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13638424/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149106938","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Unsupervised learning-based optimization of college students' fundamental capacity evaluation method.","authors":"Lei Jiang, Jinxi Zhang, Youwei Zhang, Yanan Gao, Rufeng Su, Zhixiong Zhou","doi":"10.3389/fphys.2026.1921534","DOIUrl":"10.3389/fphys.2026.1921534","url":null,"abstract":"<p><strong>Background: </strong>The Fundamental Capacity Screen (FCS) is a standardized method for assessing athletic performance and fundamental capacity (FC). However, its current framework lacks refinement, yielding qualitative and insufficiently detailed results that hinder precise athletic training and performance evaluation.</p><p><strong>Objective: </strong>This study employs unsupervised learning to refine FC evaluation, enhancing its objectivity and scientific rigor by providing a more data-driven and interpretable approach.</p><p><strong>Methods: </strong>Data from 123 college students (61 males, mean age 20.42 ± 1.88 years; 62 females, mean age 20.35 ± 1.85 years) regarding FC test indicators were initially subjected to a factor analysis (FA) model to identify underlying factors. Hierarchical clustering was then performed on the first factor. Based on these results, relevant rules of abilities were established, and principal component analysis (PCA) was employed to reduce the dimensionality of multidimensional indicators. Finally, the entropy weight method was used to calculate and adjust the scores of each ability, and the scores were summarized and classified by percentile.</p><p><strong>Results: </strong>FA revealed 3 distinct factors (jumping ability, upper limb ability, and lower limb ability) that together explained 0.8569 of the total variance. The hierarchical clustering dendrogram indicated that jumping ability could be further subdivided. Based on this, 5 ability categories were defined: upper limb balance control, lower limb balance control, core-mediated transfer control, explosive control, and impact control. The composite scores were categorized into 5 intervals: poor, pass, good, excellent, and outstanding. The depicted radar map shows the median characteristics of the composite scores of different abilities.</p><p><strong>Conclusions: </strong>Results demonstrate that unsupervised learning provides a more intuitive and objective framework for FC assessment, offering a novel perspective for athletic performance evaluation and training optimization.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1921534"},"PeriodicalIF":4.3,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13640604/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149106718","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Kaempferol ameliorates gestational diabetes mellitus by regulating STAT3-associated AIM2 inflammasome activation and ferroptotic injury in trophoblasts.","authors":"Ronghui Liu, Qiqi Liu, Lanjie Yi","doi":"10.3389/fphys.2026.1857741","DOIUrl":"10.3389/fphys.2026.1857741","url":null,"abstract":"<p><strong>Introduction: </strong>To investigate the protective effects of kaempferol (KPF) against gestational diabetes mellitus (GDM) and elucidate its underlying molecular mechanisms.</p><p><strong>Methods: </strong>A GDM rat model was established to assess metabolic abnormalities, inflammation, oxidative stress, and placental injury following KPF treatment. <i>In vitro</i>, high glucose (HG)-stimulated HTR-8/SVneo trophoblast cells were used to investigate the protective mechanisms of KPF. Mitochondrial dysfunction, lipid peroxidation, ferroptosis-related alterations, and AIM2 inflammasome activation were evaluated. STAT3 knockdown and AIM2 overexpression were further performed to determine their roles in HG-induced trophoblast injury.</p><p><strong>Results: </strong>KPF significantly improved glucose and lipid metabolism, reduced inflammatory cytokine levels, alleviated placental injury, and decreased oxidative stress in GDM rats. In HG-stimulated trophoblasts, KPF attenuated mitochondrial dysfunction, lipid peroxidation, and ferroptosis-related alterations by restoring GPX4 and SLC7A11 expression and inhibiting AIM2 inflammasome activation. Mechanistically, KPF suppressed STAT3 activation, while STAT3 knockdown reduced STAT1/IRF1 activation and AIM2 expression under hyperglycemic conditions. AIM2 overexpression aggravated ferroptosis-related changes and inflammatory responses.</p><p><strong>Conclusion: </strong>KPF alleviates GDM-associated placental dysfunction by modulating STAT3-associated signaling and AIM2 inflammasome activation, thereby reducing ferroptosis-related injury and inflammatory activation in trophoblasts. These findings provide new insights into the mechanisms of GDM and support KPF as a potential therapeutic candidate.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1857741"},"PeriodicalIF":4.3,"publicationDate":"2026-09-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13640141/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149107069","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Post-exposure effects of simulator sickness in motion-based flight simulators: a review of symptom duration and implications for flight fitness.","authors":"Nico Willebrand Genannt Overgahr, David Feibus, Stefan Sammito","doi":"10.3389/fphys.2026.1848400","DOIUrl":"https://doi.org/10.3389/fphys.2026.1848400","url":null,"abstract":"<p><strong>Introduction: </strong>The increasing use of modern motion-based flight simulators in military and civil aviation, despite their high relevance for training, is accompanied by the occurrence of simulator sickness. While acute symptoms during simulation are well described, the duration of post-exposure complaints and their significance for subsequent real flight capability have not yet been sufficiently investigated. The aim of this exploratory review was to summarise the available studies on the (persistence of) symptoms after flight-related simulator training.</p><p><strong>Methods: </strong>A systematic literature search was conducted in PubMed, Web of Science and Scopus in accordance with PRISMA guidelines. From a total of 4,404 hits, 14 full texts were included in this review.</p><p><strong>Results: </strong>The studies showed considerable heterogeneity in terms of participants, simulator types, exposure duration and measuring instruments. Typical symptoms included eye strain, nausea, disorientation and, less frequently, dizziness and fatigue. Only a few studies systematically investigated after-effects beyond the immediate period following the simulation. The limited available data suggest that most complaints subside significantly within four to six hours, although individual cognitive and postural impairments may persist for longer. It is currently not possible to make reliable statements about the objective restoration of flight fitness or an evidence-based minimum waiting period between simulator training and actual flight.</p><p><strong>Discussion: </strong>Overall, there is a considerable need for research, particularly using modern full-motion simulators and standardised objective performance parameters, for deriving valid safety-related recommendations and examining symptom decay.</p><p><strong>Systematic review registration: </strong>https://www.crd.york.ac.uk/PROSPERO/, identifier CRD420251161357.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1848400"},"PeriodicalIF":4.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13634811/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149107081","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Sublethal cadmium exposure disrupts cardiac function and tissue structure in zebrafish larvae.","authors":"Alexander Machikhin, Anastasia Guryleva, Viacheslav Krylov, Valeriya Bukova, Artem Slavin, Leonid Shuman, Alexander Selyukov, Alexander Burlakov, Anirban Chakraborty","doi":"10.3389/fphys.2026.1865285","DOIUrl":"https://doi.org/10.3389/fphys.2026.1865285","url":null,"abstract":"<p><p>Cadmium remains a primary toxicological concern because it does not degrade and easily enters the food chain, affecting diverse ecosystems. This study aimed to evaluate the effects of sublethal cadmium exposure on cardiac function and on brain and heart tissues in zebrafish (<i>Danio rerio</i>) larvae, utilizing photoplethysmography as a rapid, non-invasive approach. Larvae (1 day post-hatching) were exposed for five days to cadmium sulfate at concentrations of 0.005, 0.025, and 0.05 mg/L under controlled laboratory conditions. Cardiac activity was assessed twice a day using a non-invasive photoplethysmography-based technique. Histological analyses of brain and heart tissues were conducted using standard fixation, sectioning, and staining protocols. At the highest cadmium concentration, histological examination revealed neuronal degeneration in brain tissue and thinning of the cardiac wall. Cadmium exposure led to heart rate suppression, with the most pronounced effect observed at 0.05 mg/L. Lower concentrations exhibited attenuated but still significant effects compared to controls. These findings indicate that cadmium exerts both functional and structural toxicity in zebrafish larvae, affecting cardiovascular development and neural integrity. The results support the use of heart rate, measured via photoplethysmography, as a sensitive and non-invasive endpoint for detecting sublethal cardiotoxic effects.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1865285"},"PeriodicalIF":4.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13634864/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149107098","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Alterations in corticospinal excitability in individuals with ankle sprains: a systematic review of transcranial magnetic stimulation studies.","authors":"Yanli Chen, Mengyu Li, Songlin Xiao","doi":"10.3389/fphys.2026.1951700","DOIUrl":"https://doi.org/10.3389/fphys.2026.1951700","url":null,"abstract":"<p><strong>Objective: </strong>This study aimed to systematically review the literature on corticospinal excitability in individuals with ankle sprains.</p><p><strong>Methods: </strong>This systematic review adhered to the guidelines established by the Preferred Reporting Items for Systematic Reviews and Meta-Analyses. A systematic search was performed on PubMed, SPORTDiscus, and Web of Science. Studies were included according to the Participants, Intervention, Comparison, Outcomes, and Setting inclusion criteria.</p><p><strong>Results: </strong>The electronic search yielded 233 studies, of which eleven studies were included after careful screening. Eight of the nine studies consistently reported reduced corticospinal excitability of several lower limb muscles in chronic ankle instability (CAI). Two studies identified an elevated motor evoked potential in cases of acute lateral ankle sprain.</p><p><strong>Conclusions: </strong>CAI exhibits lower corticospinal excitability and high cortical inhibitory activity. Individuals with acute ankle sprain exhibit increased corticospinal excitability, which be presented cautiously as a preliminary finding requiring further confirmation. This review offers a theoretical basis for revealing potential changes in spinal cord segmental activities after ankle sprains, suggesting that altered corticospinal excitability may associate with impaired sensorimotor function and represents a potential target for future rehabilitation research.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1951700"},"PeriodicalIF":4.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13634940/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149106974","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Enabling artificial placenta cannulation: mechanisms of postnatal umbilical vessel closure and strategies to prolong patency.","authors":"Nils B Römer, Sjoerd Haalstra, Danny J M van Galen, Daan R M G Ophelders, G Adrienne Weiss, Jan Däbritz, Tim G A M Wolfs, Jutta Arens, Christoph Fusch, Niels Rochow","doi":"10.3389/fphys.2026.1928360","DOIUrl":"https://doi.org/10.3389/fphys.2026.1928360","url":null,"abstract":"<p><p>Umbilical vessel closure after birth prevents hemorrhage but limits the time window for large-bore umbilical cannulation required for artificial placenta support. This review synthesizes physiologic triggers, vasoactive pathways, and vessel-wall specializations that drive rapid postnatal occlusion and highlights engineering-relevant targets to prolong functional patency. Umbilical vessel closure is promoted by the transition to extrauterine life (cooling, rising oxygen tension, oxidative stress, loss of placental vasodilator influence), altered hemodynamics after lung aeration, and mechanical stimulation of the cord. At the molecular level, vasoconstriction is driven by redundant mediator networks-most prominently serotonin and thromboxane A₂, with supportive contributions from endothelin-1, acetylcholine, bradykinin, catecholamines, and histamine-occurring in the context of limited vasorelaxation capacity. Structurally, the umbilical arteries exhibit a distinctive bilayered tunica media: an outer contractile smooth-muscle-rich layer and an inner proteoglycan-rich layer prone to inward buckling, supported by longitudinal intimal protrusions (Folds of Hoboken) that further promote mechanical occlusion of the lumen. Together, these features form a robust \"fail-safe\" closure program, although the specific mechanisms governing the intra-abdominal segments remain less understood.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1928360"},"PeriodicalIF":4.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13635895/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149107097","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Aerospace stressors and brain health in military aviators: a glymphatic-neurovascular framework.","authors":"Joel Ramirez, Vincent N Marraffino, Ursula A Anirud, Shawn G Rhind","doi":"10.3389/fphys.2026.1953796","DOIUrl":"https://doi.org/10.3389/fphys.2026.1953796","url":null,"abstract":"<p><p>Military aviation exposes aircrew to interacting physiological and operational stressors that are often studied in isolation. These stressors are experienced by the whole body: pulmonary, cardiovascular, musculoskeletal, endocrine, and immune responses may influence cerebral perfusion, blood-brain barrier function, fatigue, and recovery. Evidence from aviation cohorts, altitude-chamber studies, and adjacent fields suggests that some exposures may converge on neurovascular, blood-brain barrier, perivascular, and inflammatory pathways before overt neurological disease is apparent. This narrative review evaluates the glymphatic system as one potentially important component of that broader injury-and-recovery network, rather than as a sole or established primary mechanism. We synthesize evidence concerning hypobaria and decompression, intermittent hypoxia and hyperoxia, high +Gz, sleep and circadian disruption, operational wakefulness-promoting agents, noise, cosmic ionizing radiation, and context-dependent chemical exposures. Direct human evidence of glymphatic dysfunction in tactical aviators remains absent, and findings from lower-intensity hypobaric exposure and retrospective clinical cohorts are mixed or null. Exposure profiles also differ substantially among fighter, cargo/tanker, helicopter, and remotely piloted aircraft communities. We therefore propose an exposure-resolved research agenda combining longitudinal neuroimaging, circulating biomarkers, electroencephalography, cognitive testing, sleep phenotyping, dosimetry, and controlled single- and combined-stressor experiments. This calibrated glymphatic-neurovascular framework generates testable hypotheses about cumulative brain stress and recovery while preserving alternative explanations involving direct tissue injury, cerebral perfusion, endothelial dysfunction, oxidative stress, systemic and central inflammation, and autonomic regulation.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1953796"},"PeriodicalIF":4.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13635881/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149106915","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Intra-subject covariates of QT variability indices: influence of ECG noise.","authors":"Jan Řehoř, Kateřina Helánová, Martina Šišáková, Tomáš Novotný, Irena Andršová, Marek Malik","doi":"10.3389/fphys.2026.1926685","DOIUrl":"https://doi.org/10.3389/fphys.2026.1926685","url":null,"abstract":"<p><strong>Background/objectives: </strong>Electrocardiogram (ECG) assessment of increased beat-to-beat QT interval variability indices has repeatedly been proposed to indicate adverse outcomes in different clinical populations. Nevertheless, the reported values of the indices appear poorly reproducible. Consequently, there is no clear consensus on the physiologic normal values. The limited stability of the indices might be linked to their relation to heart rate and other ECG factors such as the underlying heart rate variability. We have therefore investigated covariates of QT variability indices to answer the question of whether correction for covariates might, in principle, increase the reproducibility.</p><p><strong>Methods: </strong>In a population of 251 healthy subjects (mean age 33.6 ± 9.1 years, 108 females) who underwent repeated provocative manoeuvres, ECG measurements were performed in recordings obtained during different postural positions. In each subject, measurements of QT variability and of its plausible covariates were made in 32 separate sections of the recordings. The measurements included mean normal-to-normal RR intervals, mean QT intervals, standard deviations of RR and QT intervals, and root mean square of successive differences of QT and RR intervals. In each repeated postural position, the measurements were made in 5-minute intervals of stable heart rate. Electrocardiographic noise was assessed based on signal-to-noise ratios. Univariable and multivariable regression analyses were performed in each subject separately to assess the stability of QT variability relationship to the covariates.</p><p><strong>Results: </strong>Univariably, QT variability indices were significantly more strongly related to ECG noise than to other covariates. The regression coefficients relating QT variability to other covariates were also highly variable. In multivariable regression analyses with backwards elimination, ECG noise remained a statistically significant covariate of QT variability indices in approximately one third and one half of the population in the regression analyses of standard deviation of QT intervals and of root mean square of successive QT differences, respectively.</p><p><strong>Conclusions: </strong>It is not feasible to reduce the inconsistency of QT variability expressions by correcting them for other ECG measurements. When QT variability measures are used in clinical studies, e.g., studies of risk prediction, influence of ECG noise needs to be considered. Multivariable regression models of QT variability need to involve ECG noise data to eliminate unfounded conclusions.</p>","PeriodicalId":12477,"journal":{"name":"Frontiers in Physiology","volume":"17 ","pages":"1926685"},"PeriodicalIF":4.3,"publicationDate":"2026-09-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC13634824/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"149107031","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"OA","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}