Journal of applied physiology最新文献

{"title":"Reduced surfactant protein B levels impede unfolding of the pulmonary blood-gas barrier during inspiration in mice.","authors":"Hannia M Buchholz, Franziska Roeder, Dirk Wedekind, Oliver Dittrich-Breiholz, Jannik Ruwisch, Jens Hansen, Clemens Ruppert, Bradford J Smith, Lars Knudsen","doi":"10.1152/japplphysiol.00234.2025","DOIUrl":"10.1152/japplphysiol.00234.2025","url":null,"abstract":"<p><p>Surfactant protein B (SP-B) contributes to surface tension reduction at the pulmonary air-liquid interface. In lung injury, downregulation of alveolar SP-B is an early finding. During inspiration, unfolding processes of the interalveolar septa are considered as physiological micromechanical mechanisms that might become injurious in the presence of high surface tension, thus propagating injury. The aim of the present study was to quantify SP-B deficiency-related alterations in micromechanics of the blood-gas-barrier (BGB) during inspiration at physiological lung volumes. Our transgenic mouse line expressed SP-B under control of a doxycycline-dependent promoter. Two days after withdrawal of doxycycline (Dox-off), the mean SP-B level declined by 86%. In Dox-on and Dox-off groups, lung mechanics were assessed before the lungs were fixed at increasing airway opening pressures on inspiration or subjected to broncho-alveolar lavage (BAL) and gene expression analyses. Fixed lungs were investigated by design-based stereology. In Dox-off the BAL-albumin, alveolar hypophase volume and tissue elastance slightly increased concomitantly with proinflammatory gene-expression profiles while inflammatory cells remained unchanged. Stereology demonstrated increased derecruited septa and folded BGB in Dox-off. Although in Dox-on inspiratory unfolding of the BGB resulted in an increase of air-exposed alveolar epithelium, this mechanism was not prevalent in Dox-off where, instead, dilation of acinar airspaces occurred (mainly in the alveolar duct compartment). Inspiratory increases in surface area of the epithelial basal lamina were absent in both groups. In essence, while stretching was not observed in any group, inspiratory unfolding of the BGB is a dominant mechanism in healthy lungs but absent in SP-B deficiency.<b>NEW & NOTEWORTHY</b> Surfactant protein B (SP-B) deficiency is an early feature in experimental and clinical acute lung injury and might contribute to injury progression via mechanical stress of the blood-gas barrier (BGB) even at physiological lung volumes. Although in healthy mice, inspiratory micromechanics was dominated by unfolding processes of the BGB, this mechanism was absent in SP-B deficiency. Instead interalveolar septa appeared to be stiffened, resulting in a dilation of alveolar ducts. Stretching of the BGB was not found.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"127-144"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144234228","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Strength training for middle-distance running: a neuromuscular pathway to breaking the women's sub-4-min mile.","authors":"Boqing Wang, Michele Zanini, Richard C Blagrove","doi":"10.1152/japplphysiol.00442.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00442.2025","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":"139 1","pages":"251"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144608423","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Modulation of the human brain oxygen extraction fraction and metabolic rate in response to hyperoxia: The role of hypocapnia.","authors":"Marcos Paulo Rocha, Joao Dario Mattos, Monique O Campos, Daniel E Mansur, Qudus A Ojikutu, Niels Henry Secher, Antonio Claudio Lucas da Nóbrega, Igor A Fernandes","doi":"10.1152/japplphysiol.00354.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00354.2025","url":null,"abstract":"<p><p>Hyperoxia provokes hyperventilation, reducing arterial carbon dioxide pressure (PaCO₂), which in turn decreases cerebral blood flow (CBF) and oxygen delivery (DO₂). While hyperoxia-induced hypocapnia reduces CBF, its influence on brain oxygen extraction fraction (OEF) and metabolic rate for oxygen (CMRO₂) remains unclear, particularly given that reduced CDO₂ could modulate these parameters. We investigated how hyperoxia-induced hypocapnia affects CDO₂, OEF, and CMRO₂ in humans. Nine young men underwent two randomized sessions, each consisting of a 5-minute normoxic baseline, followed by either a 10-minute trial of isocapnic hyperoxia (IH; 100%O₂ with PaCO₂ clamp) or poikilocapnic hyperoxia (PKH; 100%O₂). Heart rate, beat-by-beat blood pressure (photoplethysmography), and ventilation were continuously monitored. CBF was measured via Doppler ultrasonography, and CDO₂, OEF, and CMRO₂ were calculated from arterial and right internal jugular venous blood samples. PaCO₂ and systemic hemodynamics remained stable during IH. In contrast, PKH provoked hyperventilation (+3.1 ± 2.9 L/min, P = 0.013) and hypocapnia (-3.0 ± 2.2 mmHg, P = 0.012). Both IH and PKH reduced CBF (ΔPKH: -257.9 ± 127.1 vs. ΔIH: -146.2 ± 105.0 mL/min, P = 0.006) and CDO₂ (ΔPKH: -37.0 ± 24.7 vs. ΔIH: -14.1 ± 21.8 mL/min, P = 0.012), with greater reductions during PKH. OEF remained unchanged during IH but increased significantly during PKH (+7.4 ± 9.3%, P = 0.016). CMRO₂ decreased during IH (-7.8 ± 11.9 mL/min, P = 0.048) but remained stable during PKH. These findings suggest that the reduction in PaCO₂ contributes to the modulation of cerebral hemodynamics and oxidative metabolism during hyperoxia.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144540273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Cardiovascular responses to standing with and without lower body compression garments after long-duration spaceflight.","authors":"Stuart M C Lee, Annelise Miller, L Christine Ribeiro, Marissa Rosenberg, Christopher A Miller, Steven S Laurie, Millennia Young, Jason R Lytle, Igor Kofman, Gilles Clement, Scott J Wood, Ilya Rukavishnikov, Vladimir Kitov, Inessa Kozlovskaya, Elena Tomilovskaya, Millard Reschke, Brandon R Macias","doi":"10.1152/japplphysiol.00646.2024","DOIUrl":"10.1152/japplphysiol.00646.2024","url":null,"abstract":"<p><p>Long-duration astronauts (>4 mo on the International Space Station, 87 total person-missions) participated in an orthostatic test consisting of 2 min of prone rest followed by 3.5 min of standing preflight, within hours of landing on the first day of recovery (R + 0), and 1, 3, 7, 14, and 30 days after landing. Astronauts and cosmonauts performed exercise during spaceflight and fluid loading before landing to mitigate cardiovascular deconditioning. On R + 0, astronauts participated in testing without compression garments or while wearing one of three garments designed to prevent orthostatic intolerance: Russian Kentavr, National Aeronautics and Space Administration's gradient compression garment (GCG), or SpaceX's gradient orthostatic protection garment (OPG). On R + 0, the change in mean arterial pressure (ΔMAP) from prone to standing tended to decrease without compression garments (-8 mmHg, <i>P</i> = 0.053) and was less in astronauts wearing the Kentavr (-5 mmHg, <i>P</i> = 0.02), but not in crewmembers wearing the GCG or OPG. The heart rate response from prone to standing (ΔHR) on R + 0 tended to increase in those not wearing compression garments (+11 beats/min, <i>P</i> = 0.051) and was greater when wearing the Kentavr (+9 beats/min, <i>P</i> < 0.0001) or the OPG (+10 beats/min, <i>P</i> = 0.003), but not different in those wearing the GCG (+1 beats/min, <i>P</i> = 0.74). Although ΔHR when not wearing compression garments was greater (<i>P</i> < 0.05) for at least 2 wk after landing, ΔMAP was not different from preflight. Wearing NASA's GCG mitigates cardiovascular stress during standing after long-duration spaceflight, and full recovery of orthostatic responses to standing without compression garments is not complete for weeks.<b>NEW & NOTEWORTHY</b> Cardiovascular adaptations during long-duration spaceflight increase the likelihood of orthostatic intolerance upon re-exposure to gravity, and thus, countermeasures have been developed. Here we report findings derived across four National Aeronautics and Space Administration- and Russian-sponsored studies using a brief stand test protocol to characterize the efficacy of lower body compression garments in the first hours after landing and orthostatic responses without compression garments during readaptation in the first 4 wk after long-duration spaceflight.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"70-80"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144036079","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An anerobic boost to a sub-4-min mile.","authors":"Shalaya Kipp, Andrew H Ramsook, Michael J Joyner","doi":"10.1152/japplphysiol.00452.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00452.2025","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":"139 1","pages":"262"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144608416","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Effects of heat therapy on exercise tolerance in a rat model of heart failure with preserved ejection fraction.","authors":"Michael D Belbis, Bohyun Ro, Luke E Schepers, Kun Ho Kim, Zhen Yap, Taylor A Schultz, Mckayla D Tallman, Morgan F Killam, Sara E Hobart, Oluwapamimo J Fafowora, Jessica N Bray, Mitchell E Fister, Vanessa C C da Silva, Hamood Ur Rehman, Binayok Sharma, Xinyue Lu, Guilherme P T Arêas, James F Markworth, Kyoungrae Kim, Terence E Ryan, Shihuan Kuang, Craig J Goergen, Timothy P Gavin, Bruno T Roseguini, Daniel M Hirai","doi":"10.1152/japplphysiol.00247.2025","DOIUrl":"10.1152/japplphysiol.00247.2025","url":null,"abstract":"<p><p>Heart failure with preserved ejection fraction (HFpEF) impairs cardiac and skeletal muscle function, reducing exercise tolerance. Few therapies are available to improve physical capacity in HFpEF. We tested the hypothesis that chronic whole body heat therapy (HT) induces central and peripheral adaptations that enhance exercise tolerance in a model of HFpEF. Male obese ZSF1 rats underwent 8 wk (6 days/wk) of HT (<i>n</i> = 14) or control (CON; <i>n</i> = 13) interventions. HT was delivered by placing animals in chambers set to 39°C, whereas CON animals were placed in chambers kept at room temperature (∼22°C). Assessments included exercise tolerance, body composition, echocardiography, mitochondrial respiration, and skeletal muscle interstitial oxygenation (Po₂), with and without nitric oxide synthase inhibition (<i>N</i>^G-nitro-l-arginine methyl ester, l-NAME). HT prevented the decline in exercise tolerance (PRE: 411 ± 13, POST: 427 ± 11; <i>P</i> > 0.05) observed in CON (PRE: 441 ± 16, POST: 344 ± 17 s; <i>P</i> < 0.05). Similarly, HT preserved left ventricular ejection fraction (PRE: 71.5 ± 1.3, POST: 74.1 ± 1.6; <i>P</i> > 0.05), which declined in CON (PRE: 72.2 ± 2.0, POST: 67.4 ± 2.2%; <i>P</i> < 0.05). Total body mass was not different between groups postintervention (CON: 624 ± 12, HT: 617 ± 14 g; <i>P</i> > 0.05). CON increased fat mass (PRE: 0.37 ± 0.01, POST: 0.38 ± 0.01; <i>P</i> < 0.05) without affecting lean mass (PRE: 0.56 ± 0.01, POST: 0.56 ± 0.01; <i>P</i> > 0.05). In contrast, HT reduced fat mass (PRE: 0.38 ± 0.01, POST: 0.34 ± 0.01; <i>P</i> < 0.05) and increased lean mass (PRE: 0.56 ± 0.01, POST: 0.61 ± 0.01; <i>P</i> < 0.05). HT improved resting and contracting muscle Po₂ partly via enhanced nitric oxide bioavailability. There were no differences in skeletal muscle mitochondrial respiration between groups. These findings indicate that HT promotes central and peripheral adaptations that improve exercise tolerance in a preclinical model of HFpEF.<b>NEW & NOTEWORTHY</b> This is the first evaluation of the effects of heat therapy (HT) in heart failure with preserved ejection fraction (HFpEF). HT elicited multiple central and peripheral adaptations that impacted positively exercise tolerance in a preclinical model of HFpEF. HT adaptations included improvements in cardiac function, body composition, and skeletal muscle oxygenation (mediated partially via enhanced nitric oxide bioavailability). These novel findings indicate that HT may hold important clinical significance for the treatment of HFpEF.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"185-205"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144293823","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Circulating miRNA levels following a 14-wk aerobic exercise intervention during pregnancy: a secondary exploratory analysis of the PEACH RCT.","authors":"Alejandro A Candia, Rachel J Skow, Anita Quon, Craig D Steinback, Sandra T Davidge, Margie H Davenport","doi":"10.1152/japplphysiol.00101.2025","DOIUrl":"10.1152/japplphysiol.00101.2025","url":null,"abstract":"<p><p>Physical activity (PA) during pregnancy decreases the risk of developing hypertensive disorders of pregnancy by 40%, yet the underlying molecular mechanisms are unknown. microRNAs (miRNAs) have shown potential in cardiovascular disease prevention and diagnosis. Circulating levels of miR-21-3p and miR-146b-5p are associated with early pregnancy leisure time PA energy expenditure. However, it is not clear how miRNA levels change in response to exercise across pregnancy. We aimed to determine the change in circulating levels of miRNAs after a 14-wk, moderate-intensity aerobic exercise intervention in pregnant women. A subset of 10 pregnant women from the Prenatal Exercise and Cardiovascular Health (PEACH) study were included. Participants were randomized to a supervised aerobic exercise program (<i>n</i> = 5) or a control group (<i>n</i> = 5). At 18-21 (baseline) and 34-36 [postintervention (PI)] wk of pregnancy, a fasted blood draw and neurovascular assessment were carried out. Muscle sympathetic nerve activity burst incidence (BI), heart rate (HR), systolic blood pressure (SBP), diastolic blood pressure (DBP), and mean arterial pressure (MAP), respectively, cardiac output (CO), and plasma miRNA levels were measured at each timepoint. Exercise prevented the rise in BI from baseline to PI. At baseline, both miRNA-146b-5p and miR-21-3p levels were not different between the groups. miR-21-3p increased from baseline to PI in both groups, but the exercise group had significantly higher levels at PI. A 14-wk aerobic exercise training intervention during pregnancy increases miR-21-3p levels in maternal plasma. Future work in a larger cohort will allow us to determine the relationship of miR-21-3p with maternal outcomes.<b>NEW & NOTEWORTHY</b> Pregnant women who were exposed to 14-wk aerobic exercise training intervention have increased miR-21-3p levels in plasma accompanied by an attenuation in the increase of burst incidence across pregnancy.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"37-44"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143965615","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Disuse and subsequent recovery resistance training affect skeletal muscle angiogenesis-related markers regardless of prior resistance training experience.","authors":"Mason C McIntosh, J Max Michel, Joshua S Godwin, Daniel L Plotkin, Derick A Anglin, Madison L Mattingly, Anthony Agyin-Birikorang, Nicholas J Kontos, Harsimran S Baweja, Matt S Stock, C Brooks Mobley, Michael D Roberts","doi":"10.1152/japplphysiol.00988.2024","DOIUrl":"10.1152/japplphysiol.00988.2024","url":null,"abstract":"<p><p>We recently reported that resistance-trained (T, <i>n</i> = 10) and untrained (UT, <i>n</i> = 11) young adults experience vastus lateralis (VL) muscle atrophy following 2 wk of disuse, and 8 wk of recovery resistance training (RT) promotes VL hypertrophy in both participant cohorts. Skeletal muscle angiogenesis is appreciated for supporting skeletal muscle hypertrophy, but its activity following disuse-induced atrophy in humans is largely unexplored in the context of RT. Thus, we sought to determine whether these outcomes were affected. VL biopsies were obtained at baseline (PRE), immediately after disuse (MID), and after RT (POST). Western blotting was used to assay angiogenesis markers, and immunohistochemistry was performed in 16/21 participants to determine type I and II muscle fiber capillary number. Significant main effects of time (<i>P</i> < 0.05) were observed for protein levels of vascular endothelial growth factor (VEGF) (MID < POST), VEGF receptor-2 (VEGFR2; PRE&MID < POST), thrombospondin1 (TSP-1; PRE < POST), TIMP metallopeptidase inhibitor 1 (TIMP1; MID < POST), phosphorylated/pan endothelial nitric oxide synthase (eNOS) (Ser1177) (POST < PRE), and pan eNOS (PRE < POST). VEGFR2 exhibited a training status × time interaction (<i>P</i> = 0.018), but no differences existed between T and UT at any time point. A significant main effect of time was observed for type II fiber capillary number (PRE < POST), and type II fiber cross-sectional area (fCSA) increased from MID to POST (+25%, <i>P</i> < 0.001) and PRE to POST (+20%, <i>P</i> = 0.019). No significant correlations exist for percentage changes in type II fiber capillary number and type II fCSA from PRE-to-MID (<i>r</i> = 0.020), MID-to-POST (<i>r</i> = 0.392), or PRE-to-POST (<i>r</i> = -0.120) across all participants (<i>P</i> > 0.100). Although disuse and recovery RT affect skeletal muscle angiogenesis-related protein targets, prior training history does not differentially affect these outcomes.<b>NEW & NOTEWORTHY</b> As a follow-up to our original investigation by Michel JM et al. <i>J Appl Physiol (1985)</i> 138: 450-467, 2025, we sought to examine how limb immobilization and recovery resistance training affect molecular outcomes related to angiogenesis in younger adults with or without a prior training history. Regardless of resistance training history, the molecular responses are largely similar between participant cohorts and are suggestive of a reduced (PRE-MID) and increased (MID-POST) angiogenic response, with disuse and subsequent recovery resistance training.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"81-90"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144247999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Buffering your way to sub-4! An important consideration for middle-distance performance.","authors":"Trent Stellingwerff, Bryan Saunders, Jason C Siegler","doi":"10.1152/japplphysiol.00441.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00441.2025","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":"139 1","pages":"252-253"},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144608419","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Daily use of countermeasures to prevent headward fluid shifts throughout 30 days of strict head-down tilt bed rest.","authors":"Steven S Laurie, Jason R Lytle, Sarah K Pickering, Matthew James Poczatek, Stuart M C Lee, Laura P Pardon, Annelise E Miller, David S Martin, Edwin Mulder, Stefan Moestl, Dominik Pesta, Timo Frett, Claudia Stern, Jens Tank, Jan-Niklas Hoenemann, SriniVas Sadda, Rustum Karanjia, Karina Marshall-Goebel, Millennia Young, Christine W Cole, Alex S Huang, Brandon R Macias","doi":"10.1152/japplphysiol.00635.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00635.2024","url":null,"abstract":"<p><p>Strict 6° head-down tilt bed rest (HDTBR) induces a chronic headward fluid shift similar to weightlessness that may underlie development of spaceflight associated neuro-ocular syndrome. We tested the efficacy of two headward fluid shift countermeasures, using either 25 mmHg lower body negative pressure (LBNP, 2 x 3 hours daily, n=12) or use of venoconstrictive thigh cuffs (VTC) following 1 hour of moderate aerobic cycle exercise (Ex+CUFF, 6 hours daily for 6 of 7 days, n=12) across 30 days of HDTBR. The study also included a seated posture group (Upright, 2 x 3 hours daily, n=11) which was conducted in the 2 campaigns with the LBNP group, and a control group that did not receive a countermeasure (n=12) that was studied across the 2 campaigns with the Ex+CUFF group. All LBNP sessions and Ex+CUFF sessions were well-tolerated. On HDT 3, 17, and 30 both countermeasures decreased internal jugular vein cross-sectional area (LBNP: -0.97 cm²; Ex+CUFF: -0.64 cm²), stroke volume (LBNP: -40.2 mL; Ex+CUFF: -33.5 mL), and IOP (LBNP: -0.5 mmHg; Ex+CUFF: NS), but to lesser degrees than occurred in Upright for all variables. Reversal of the headward fluid shift during use of each countermeasure presented with positive comfort scores throughout the 30-day bed rest study, highlighting that use of LBNP or VTCs following exercise should be tested during spaceflight to address risks associated with the chronic headward fluid shift that occurs in weightlessness.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-07-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144540271","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}