Journal of applied physiology最新文献

{"title":"A small constant external negative pressure improves lung aeration at birth in rabbit kittens with a diaphragmatic hernia.","authors":"Paige J Riddington, Philip L J DeKoninck, Indya M Davies, Dominic Jurkschat, Megan J Wallace, Janneke Dekker, Arjan B Te Pas, Marcus J Kitchen, Stuart B Hooper, Kelly J Crossley","doi":"10.1152/japplphysiol.00154.2025","DOIUrl":"10.1152/japplphysiol.00154.2025","url":null,"abstract":"<p><p>Infants with a congenital diaphragmatic hernia often require high peak inflation pressures to aerate and ventilate their stiff, hypoplastic lungs at birth. However, although high peak inflation pressures are associated with ventilator-induced lung injury, lower peak inflation pressures (considered to be gentle) may not sufficiently aerate the lungs. The objective of the study was to investigate whether a small constant external negative pressure can improve lung aeration at birth in rabbit kittens with a diaphragmatic hernia. A diaphragmatic hernia was surgically induced in 2-3 rabbit fetuses per doe (<i>n</i> = 20) at 24 d gestation. At 30 d, diaphragmatic hernia kittens (<i>n</i> = 21) and control littermates (<i>n</i> = 19) were delivered by caesarean section, intubated, and placed in a water-filled plethysmograph. Kittens were ventilated (volume targeted: 8 mL/kg for control, 4 mL/kg for diaphragmatic hernia kittens) with either an external negative pressure (-6 cmH₂O) without a positive end-expiratory pressure (PEEP; Negative/0PEEP) or at atmospheric pressure (0 cmH₂O) with or without PEEP (Atmos/5PEEP and Atmos/0PEEP). Lung aeration was measured using phase-contrast X-ray imaging and plethysmography. Data (means ± SD) were analyzed using a repeated-measures linear mixed model (<i>P</i> < 0.05). Diaphragmatic hernia kittens ventilated in Negative/0PEEP required lower peak inflation pressures to achieve the target tidal volume than Atmos/5PEEP (10.9 ± 2.6 vs. 15.4 ± 2.6 cmH₂O; <i>P</i> = 0.004) and Atmos/0PEEP kittens (14.2 ± 2.6 cmH₂O; <i>P</i> = 0.052). Negative/0PEEP diaphragmatic hernia kittens also had greater functional residual capacities compared with Atmos/5PEEP (19.9 ± 3.9 vs. 13.8 ± 3.9 mL/kg; <i>P</i> = 0.015) and Atmos/0PEEP kittens (6.4 ± 3.9 mL/kg; <i>P</i> < 0.001). A small constant external negative pressure increased lung aeration with lower peak inflation pressures in mechanically ventilated diaphragmatic hernia rabbit kittens.<b>NEW & NOTEWORTHY</b> This study demonstrates that a small constant external negative pressure applied during conventional mechanical ventilation improves lung aeration and achieves set tidal volumes with significantly lower peak inflation pressures in rabbit kittens with a diaphragmatic hernia and severe lung hypoplasia. The negative extrathoracic pressure improved dynamic lung compliance and stabilized the chest wall. Our findings indicate that negative extrathoracic pressures do more than simply act to replace a positive end-expiratory pressure to enhance respiratory function.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"582-593"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144682642","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":"Active ascent accelerates the onset of acute mountain sickness at 4,300 m.","authors":"Pierre A Fabries, Steven D Landspurg, Peter S Figueiredo, Quint N Berkemeier, Sean P Langan, Emily C Tagesen, Melissa D McInnis, Adam J Luippold, Devin A Connolly, Paul M Bartlett, Robert L Alunday, Aaron J Reilly, Trevor J Mayschak, Nicolas A Weiss, Bianca E Alvarez, Nicole K Munoz, Sean A Buehler, J Philip Karl, Erik R Swenson, William J Tharion, Jon K Femling, Beth A Beidleman","doi":"10.1152/japplphysiol.00391.2025","DOIUrl":"10.1152/japplphysiol.00391.2025","url":null,"abstract":"<p><p>Acute mountain sickness (AMS) usually peaks after the first night at high altitude (HA) and resolves within 2-3 days, but the effect of active ascent on AMS is debated. This study examined the incidence, severity, and time course of AMS following active versus passive ascent from 3,950 to 4,300 m. Thirty-two healthy participants traveled from low altitude (55-399 m) to 3,950 m. Participants either hiked (active group, <i>n</i> = 16) or were driven (passive group, <i>n</i> = 16) to 4,300 m, staying for 4 days (HA1-HA4). AMS was assessed daily using the Environmental Symptoms Questionnaire, with an AMS-cerebral (AMS-C) factor score ≥0.7 indicative of sickness. The active group compared with the passive group expended more energy (1,265 ± 351 vs. 408 ± 208 kcal) and demonstrated lower peripheral oxygen saturation (75 ± 3 vs. 82 ± 3%) during ascent. In the active group, the incidence of AMS peaked on HA1 (81%), remained elevated on HA2 (75%) and HA3 (57%), and decreased on HA4 (30%). In the passive group, the incidence of AMS peaked on HA2 (69%) compared with HA1 (44%), remained elevated on HA3 (33%), and decreased on HA4 (8%). The AMS incidence was higher in the active compared with the passive group on HA1. High-intensity exercise during ascent worsens AMS symptoms on HA1, likely due to greater hypoxemia during ascent. Tasks that need to be performed immediately upon arrival at HA may be negatively affected by strenuous exercise, and personnel should consider appropriate countermeasures to minimize the impact of exercise on AMS in the early hours of HA exposure.<b>NEW & NOTEWORTHY</b> Active ascent to 4,300 m high altitude (HA) accelerated the onset of AMS, confirming previous findings at 3,600 m. Peak AMS symptoms occurred on HA1 in active ascenders and on HA2 in passive ascenders. Unlike at 3,600 m, active ascenders did not recover faster compared with passive ascenders. AMS was likely exaggerated in active ascenders on HA1 due to an ∼7% greater arterial desaturation, increasing hypoxemia during the first 2-3 h at high altitude.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"557-569"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144659323","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":"Preoperative serum LOXL2 levels are elevated in patients with pulmonary hypertension undergoing mitral valve surgery in a prospective observational cohort study.","authors":"Sineád M Nyhan, Mahin Gadkari, Travis Brady, Marta Martinez Yus, Rira Choi, Maria Bauer, Samira Vithani, Joseph Walpole, Allison G Hays, Hamza Aziz, Ahmet Kilic, Michael Robich, James S Gammie, Lakshmi Santhanam, Jochen Steppan","doi":"10.1152/japplphysiol.00287.2025","DOIUrl":"10.1152/japplphysiol.00287.2025","url":null,"abstract":"<p><p>Lysyl oxidase-like 2 (LOXL2) is associated with vascular remodeling associated in pulmonary hypertension (PH). This study evaluates the potential of serum LOXL2 levels as a clinical biomarker. We enrolled 158 patients undergoing mitral valve surgery. Using echocardiographic right ventricular systolic pressures (RVSPs), patients were stratified into those with and without PH preoperative, postoperative, and postdischarge. Healthy volunteers served as a nonsurgical control. Serum LOXL2 concentrations preincision were compared with RVSPs using simple regression and their relationship to PH using one-way ANOVA with Tukey's posttest. Serum LOXL2 concentrations were significantly higher in patients with PH compared with patients without PH (2,718 ± 5,187 pg/mL vs. 640 ± 1,367 g/mL; <i>P</i> = 0.0009) and compared with healthy volunteers (283 ± 615 pg/mL; <i>P</i> = 0.04). There was a positive correlation between RVSPs and serum LOXL2 concentrations (<i>P</i> = 0.02, <i>r</i>² = 0.08). Serum LOXL2 levels positively correlated with intraoperative indices of pulmonary compliance, suggesting that PH in this cohort may primarily represent postcapillary PH. Patients with PH postprocedure (and before discharge) had greater preprocedure serum LOXL2 levels compared with patients without PH (4,348 ± 8,498 pg/mL vs. 1,281 ± 2,329 pg/mL, <i>P</i> = 0.006), as did patients assessed after discharge (1,359 ± 2,693 pg/mL vs. 4,195 ± 6,568 pg/mL, <i>P</i> = 0.009). Patients with persistent PH or new PH had elevated presurgical LOXL2 levels compared with those without PH at both timepoints (4,301 ± 7,717 pg/mL vs. 556.6 ± 835.8 pg/mL, <i>P</i> = 0.02; 2,902 ± 5,255 pg/mL vs. 556.6 ± 835.8 pg/mL, <i>P</i> = 0.03). Serum LOXL2 is elevated in patients with PH. LOXL2 is a potential PH biomarker in patients undergoing mitral valve surgery. This could have implications for follow-up care.<b>NEW & NOTEWORTHY</b> Serum LOXL2 levels are elevated in patients with PH undergoing mitral valve surgery, and they do correlate with disease severity and persistence, suggesting that LOXL2 plays a role in human PH and holds potential as an important biomarker for PH.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"325-333"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12320476/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144600495","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":"Chemistry versus compensation: comparing integrated respiratory-renal blood acid-base responses between acute inspired normobaric hypoxia versus sustained hypobaric hypoxia.","authors":"Nicole A Johnson, Nicholas D J Strzalkowski, Monica K Russell, Christian A Clermont, Jennifer M Demarty, Leo C Transfiguracion, John F Horton, Michael J Asmussen, Trevor A Day","doi":"10.1152/japplphysiol.01014.2024","DOIUrl":"10.1152/japplphysiol.01014.2024","url":null,"abstract":"<p><p>During acute exposure to hypoxia, peripheral respiratory chemoreceptors detect decreases in blood oxygenation, eliciting a hypoxic ventilatory response (HVR), which is enhanced with the duration and intensity of exposure (ventilatory acclimatization). The HVR protects oxygenation, but a secondary consequence is the elimination of arterial partial pressure of carbon dioxide ([Formula: see text]), resulting acutely in hypocapnia and respiratory alkalosis. With sustained exposure to hypobaric hypoxic conditions (e.g., high-altitude ascent; HA), the renal tubules reduce [Formula: see text] reabsorption and H⁺ excretion, excreting [Formula: see text] and retaining H⁺, returning arterial pHa toward normal values. We aimed to characterize and compare blood oxygenation and acid-base homeostasis between two models of hypoxic exposure with matching inspired partial pressure of oxygen ([Formula: see text]) (∼74-76 mmHg): acute hypoxic exposure eliciting an HVR-mediated hypocapnia over 24 min versus sustained hypoxic-hypocapnia with incremental ascent to HA over 10 days. Using arterial blood draws, we measured arterial partial pressure of oxygen, [Formula: see text], [Formula: see text], [[Formula: see text]]a, and pHa, obtained before and following <i>1</i>) acute stepwise reductions in fraction of inspired oxygen ([Formula: see text]) for ∼24 min, with the last step being an [Formula: see text] of 0.12 ([Formula: see text] ≅ 74 mmHg) and <i>2</i>) sustained exposure to hypoxia during incremental ascent to 5,200 m over 10 days ([Formula: see text] ≅ 76 mmHg). We found that <i>1</i>) acute normobaric hypoxia elicited hypocapnia and respiratory alkalosis, as expected, and <i>2</i>) after sustained exposure to hypobaric hypoxia, there was persistent alkalosis, despite appreciable renal compensation. These findings highlight the time course and magnitude of integrated respiratory responses and subsequent renal compensation mounted by the kidneys, specifically that the hypoxia-mediated hypocapnia and respiratory alkalosis experienced at 5,200 m is likely beyond the threshold for a full renal compensation in healthy lowlanders.<b>NEW & NOTEWORTHY</b> No studies have directly compared differences in oxygenation and acid-base balance after differential time courses of exposure to inspired hypoxia. We show that after exposure to the same hypoxic stimulus ([Formula: see text] ∼ 74-76 mmHg) over acute (24 min; [Formula: see text] of 0.12) versus sustained (10 days; 5,200 m) exposures, sustained exposure resulted in a persistent alkalemia, despite appreciable renal compensation. These findings highlight the time course and magnitude of integrated respiratory-renal responses and acid-base compensations in response to hypoxic exposure in healthy individuals.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"529-540"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144317002","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":"Metformin suppresses the mitochondrial and transcriptional response to exercise, revealing a conserved BCL6B-associated angiogenic program.","authors":"Matthew D Bruss, Christian J Elliehausen, Josef P Clark, Dennis M Minton, Adam R Konopka","doi":"10.1152/japplphysiol.00432.2025","DOIUrl":"10.1152/japplphysiol.00432.2025","url":null,"abstract":"<p><p>We have previously demonstrated that the inhibitory effect of metformin on skeletal muscle mitochondrial respiration was associated with attenuated improvements in whole body insulin sensitivity and cardiorespiratory fitness after aerobic exercise training (AET) in older adults. To identify processes associated with the inhibitory effect of metformin on mitochondrial adaptations to AET, we evaluated the skeletal muscle transcriptome, mitochondrial respiration, and hydrogen peroxide (H₂O₂) emissions in 7-mo-old male C57BL6/J mice after 8 wk of nonexercise sedentary control (SED) or progressive AET with and without metformin treatment. Similar to our findings in humans, metformin diminished the improvement in whole body cardiometabolic adaptations and the increase in mitochondrial respiration in both isolated mitochondria and permeabilized muscle fibers after AET in mice. However, AET with or without metformin did not impact resting mitochondrial H₂O₂ emissions. Metformin decreased the number of differentially expressed genes after AET by ∼50% and suppressed several transcription factors and signal transduction pathways involved in skeletal muscle proteostasis, myogenesis, oxidative capacity, and angiogenesis. A parallel analysis of human resistance exercise data revealed overlapping metformin-sensitive transcription factors and B Cell CLL/Lymphoma 6B (BCL6B)-associated signaling networks implicated in angiogenesis, suggesting a conserved regulatory axis across species and exercise modalities. Collectively, these data demonstrate that attenuation of mitochondrial respiration by metformin coincides with transcriptional repression and identify specific pathways and regulators, such as BCL6B, that may contribute to the suppression of exercise adaptations by metformin.<b>NEW & NOTEWORTHY</b> Metformin inhibited skeletal muscle mitochondrial respiration and transcriptional adaptations to aerobic exercise training. The findings from this study suggest BCL6B as a conserved exercise-responsive transcription factor in mice and humans that is sensitive to metformin, enriched in endothelial cells, and implicated in angiogenesis.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"541-556"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12375879/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144690383","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":"A rapid increase in left atrial pressure reduces pulmonary arterial compliance in rats: insights from pulmonary arterial impedance analysis.","authors":"Masafumi Fukumitsu, Naoshi Hotta, Toru Kawada, Takuya Nishikawa, Keita Saku","doi":"10.1152/japplphysiol.00073.2025","DOIUrl":"10.1152/japplphysiol.00073.2025","url":null,"abstract":"<p><p>Pulmonary arterial (PA) impedance is a comprehensive parameter that describes the dynamic properties of pulmonary circulation. PA impedance is estimated using the transfer function that relates PA flow to pressure waveforms. However, both PA flow and pressure may be affected by left atrial (LA) pressure, especially when LA pressure is elevated. This study aimed to evaluate the impact of increased LA pressure on the estimation of PA impedance and its associated parameters. We used eight male Sprague-Dawley rats to measure PA impedance using <i>1</i>) one-input, one-output (I1O1) analysis that does not consider LA pressure in the calculation and <i>2</i>) two-input, one-output (I2O1) analysis that takes into account the potential effect of LA pressure on PA flow and pressure. Under normal physiological conditions, both I1O1 and I2O1 analyses provided accurate estimates of PA impedance with high coherence function. However, when LA pressure was increased by transverse aortic ligation with blood transfusion, I1O1 analysis showed reduced coherence in the low frequency range, whereas I2O1 analysis maintained reasonable estimation of PA impedance. When parameterizing PA impedance estimated by I2O1 analysis, rapid increase in LA pressure was associated with decreased pulmonary arterial compliance (<i>C</i>_p), without affecting peripheral pulmonary resistance (<i>R</i>_p), characteristic impedance of the proximal arteries (<i>Z</i>_c), or transmission time from the main trunk to the reflection sites. In conclusion, increase in LA pressure significantly decreases <i>C</i>_p, whereas <i>R</i>_p and <i>Z</i>_c remain unaltered. When estimating PA impedance under conditions of elevated LA pressure, the effect of LA pressure should not be neglected.<b>NEW & NOTEWORTHY</b> Pulmonary arterial impedance estimation is minimally affected by left atrial pressure under physiological conditions; however, it is substantially affected by excessive increase in left atrial pressure. Rapid increase in atrial pressure is associated with significant decrease in pulmonary arterial compliance, with no changes in peripheral pulmonary resistance and characteristic impedance of proximal pulmonary arteries. Consequently, left atrial pressure should be taken into account when estimating pulmonary arterial impedance under conditions of elevated left atrial pressure.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"496-508"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144600492","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":"Leg vascular function with advancing age in men: the impact of physical activity and endurance exercise training.","authors":"Eivind Wang, Matthew J Rossman, H Jonathan Groot, Ryan S Garten, Catherine L Jarrett, Jan Helgerud, Jan Hoff, Russell S Richardson","doi":"10.1152/japplphysiol.00784.2024","DOIUrl":"10.1152/japplphysiol.00784.2024","url":null,"abstract":"<p><p>Regular physical activity and endurance exercise training prevent age-related vascular endothelial dysfunction in the arm in men. However, the effects of physical activity and/or endurance exercise training in the legs, which have a greater predisposition for vascular disease, have not been completely elucidated. This study sought to examine the impact of aging, physical activity, and endurance exercise training on leg vascular function in men. Flow-mediated dilation (FMD) of the superficial femoral and popliteal arteries (SFA and PA, respectively) was assessed in a total of 39 men, comprised of 10 young sedentary (Y; 23 ± 2 yr), 8 older sedentary (OS; 76 ± 8 yr), 9 older physically active (OA; 71 ± 8 yr), and 12 older endurance exercise trained (OT) subjects with exceptional aerobic exercise capacity (V̇o_2max) for their age (70 ± 3 yr, V̇o_2max = 53 ± 6 mL·kg^-1·min^-1). FMD was lower in the OS group compared with the Y in the SFA (Y: 4.3 ± 2.1%, OS: 1.7 ± 1.0%, <i>P</i> = 0.005) and PA (Y: 5.8 ± 2.4%, OS: 1.9 ± 1.1%, <i>P</i> < 0.05). SFA and PA FMD were not different from OS in the OA group (SFA: 2.8 ± 1.5%; PA: 1.6 ± 1.0%) but were higher than OS in the OT group (SFA: 3.4 ± 2.3%, <i>P</i> = 0.043; PA: 4.2 ± 3.0%, <i>P</i> = 0.025) and not different from Y. There was evidence of a moderate-strong correlation between SFA (<i>r</i> = 0.32, <i>P</i> = 0.052) and PA (0.36, <i>P</i> = 0.037) FMD and V̇o_2max but not physical activity levels. These findings suggest that habitual physical activity in general, and endurance exercise training in particular, diminishes the detrimental effect of aging on lower limb vascular function in men, and this may be linked to an augmented V̇o_2max.<b>NEW & NOTEWORTHY</b> In the current study, we provide evidence of a relation between high levels of physical activity associated with lifelong endurance exercise training and protection from age-related declines in vascular endothelial function in the lower limb in men. Moreover, our findings suggest that aerobic fitness, in particular, may confer the benefits of endurance exercise training in maintaining lower limb endothelial function with advancing age.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"473-481"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"https://www.ncbi.nlm.nih.gov/pmc/articles/PMC12366479/pdf/","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144600494","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":"Corrigendum for Debenham et al., volume 136, 2024, p. 1468-1477.","authors":"","doi":"10.1152/japplphysiol.00592.2023_COR","DOIUrl":"https://doi.org/10.1152/japplphysiol.00592.2023_COR","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":"139 2","pages":"570"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144835193","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 J 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":"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 the 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 × 3 h daily, <i>n</i> = 12) or use of venoconstrictive thigh cuffs (VTC) following 1 h of moderate aerobic cycle exercise (Ex + CUFF, 6 h daily for 6 of 7 days, <i>n</i> = 12) across 30 days of HDTBR. The study also included a seated posture group (Upright, 2 × 3 h daily, <i>n</i> = 11), which was conducted in the two campaigns with the LBNP group, and a control group that did not receive a countermeasure (<i>n</i> = 12) that was studied across the two campaigns with the Ex + CUFF group. All LBNP sessions and Ex + CUFF sessions were well tolerated. On HDTBR day 3, 17, and 30, both countermeasures decreased internal jugular vein cross-sectional area (LBNP: -0.97 cm²; Ex + CUFF: -0.64 cm²), stroke volume (SV) (LBNP: -40.2 mL; Ex + CUFF: -33.5 mL), and intraocular pressure (LBNP: -0.5 mmHg; Ex + CUFF: not significant), 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.<b>NEW & NOTEWORTHY</b> We demonstrate that daily use of lower body negative pressure or venoconstrictive thigh cuffs following aerobic exercise is well tolerated throughout 30 days of exposure to the spaceflight analog strict head-down tilt bed rest. Both countermeasures reduced SV and internal jugular vein cross-sectional area, indicators of the venous fluid shift, but to a lesser degree than the upright posture.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"394-413"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","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}

{"title":"Exercise-induced bronchodilation is not different in healthy males and females.","authors":"Benjamin P Thompson, Connor J Doherty, Paolo B Dominelli","doi":"10.1152/japplphysiol.00829.2024","DOIUrl":"10.1152/japplphysiol.00829.2024","url":null,"abstract":"<p><p>Exercise-induced bronchodilation (EIBD) is the dilation of the airways that occurs during whole body dynamic exercise. Females have greater β2-adrenergic receptor activity in the peripheral vasculature, which accentuates vasodilation, but it is unknown if this translates to the airways. EIBD can be quantified by performing maximal expiratory maneuvers before and immediately after exercise; however, the assessment is impacted by thoracic gas compression. Accordingly, we sought to determine if there are sex differences in the extent of EIBD. Twenty-two healthy adults (<i>n</i> = 11 female) performed multiple forced expiratory maneuvers in a custom-designed volume-displacement body plethysmograph, before and after incremental cycle exercise to volitional exhaustion. The customized body plethysmograph allows for simultaneous assessment of compressed and compression-free flow-volume loops. During exercise, inspired air was warmed (24 ± 0.7°C) and humidified (94 ± 6%) and postexercise pulmonary function was completed <10 min after exercise cessation. Males had a greater maximal oxygen uptake than females (51 ± 7 mL kg^-1min^-1 vs. 42 ± 6 mL kg^-1min^-1, <i>P</i> < 0.01). Using compressed flow-volume loops, forced expiratory volume in 1 s was increased following exercise in males (5.03 ± 0.58 L vs. 4.80 ± 0.63 L, <i>P</i> < 0.01) and females (3.96 ± 0.32 L vs. 3.81 ± 0.31 L, <i>P</i> < 0.01), but the relative change from baseline was not different between the sexes (<i>P</i> = 0.39). Likewise, the relative change in mid-expiratory flows was not different between sexes (<i>P</i> = 0.77). Using compression-free flow-volume loops, bronchodilation was evident using mid flows in both sexes. In conclusion, the extent of EIBD is not different between the sexes, but the use of compression-free flow-volume curves only shows EIBD for mid flows in both sexes similarly.<b>NEW & NOTEWORTHY</b> The magnitude of exercise-induced bronchodilation (EIBD) was not different in healthy young males and females. Both sexes exhibited a ∼5% improvement in forced expired volume in 1 s and an 8%-20% improvement in mid-expiratory flows. When accounting for thoracic gas compression using a volume displacement plethysmograph, the lack of sex differences in EIBD persisted but the absolute magnitude of EIBD was diminished.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"444-453"},"PeriodicalIF":3.3,"publicationDate":"2025-08-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144608414","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}