Journal of applied physiology最新文献

{"title":"Patient-specific prediction of regional lung mechanics in patients with ARDS with physics-based models: a validation study.","authors":"Maximilian Rixner, Maximilian Ludwig, Matthias Lindner, Inéz Frerichs, Armin Sablewski, Karl-Robert Wichmann, Max-Carl Wachter, Kei W Müller, Dirk Schädler, Wolfgang A Wall, Jonas Biehler, Tobias Becher","doi":"10.1152/japplphysiol.00313.2025","DOIUrl":"10.1152/japplphysiol.00313.2025","url":null,"abstract":"<p><p>Lung-protective ventilation significantly influences outcomes in patients with acute respiratory distress syndrome (ARDS), but identifying optimal settings remains a challenge due to pronounced inter- and intrapatient variability in lung anatomy and pathophysiology. This study demonstrates that physics-based computational lung models tailored to individual patients can predict otherwise unobservable local lung states, enabling a quantitative analysis of regional ventilation and the mechanical load experienced by lung parenchyma during ventilation. For seven mechanically ventilated patients with ARDS, patient-specific computational models were generated using chest computed tomography (CT) scan and ventilatory waveform data. By numerically resolving the lung's interaction with ventilator-imposed pressure and flow, we predict both the regional ventilation and the dynamic, spatially heterogeneous states of the lung. Model-predicted ventilation distributions were validated against clinical measurements from bedside electrical impedance tomography (EIT). The predicted anteroposterior ventilation profiles exhibited excellent agreement with EIT, achieving a Pearson correlation of 96%. Across the full transverse cross section and over the dynamic ventilation range, the models achieved an average correlation exceeding 81% and a root mean square error below 15%. This first systematic validation study indicates that computational lung models can reliably estimate patient-specific regional ventilation. These findings support the use of such models as a tool for individualized decision-making in mechanical ventilation, offering insights into both anatomical and functional lung characteristics that are not directly observable at the bedside. By leveraging detailed patient data and physical modeling, these models have the potential to inform more personalized and physiologically grounded ventilator settings, improving care in critically ill patients with ARDS.<b>NEW & NOTEWORTHY</b> This study presents the first systematic validation of physics-based, patient-specific computational lung models for mechanically ventilated patients. By comparing model-predicted regional ventilation with bedside electrical impedance tomography, we demonstrate the ability of our computational approach to predict regional lung mechanics and patient-specific phenomena. Embedded within a computational pipeline fast enough for clinical workflows, this marks a significant step toward truly personalized, model-informed ventilation management in the ICU.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1029-1049"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144955397","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":"Impact of intravenous iron or exogenous erythropoietin on hemoglobin mass, exercise performance, and acute mountain sickness during altitude acclimatization.","authors":"Karleigh E Bradbury, Elizabeth A Gideon, Marissa N Baranauskas, Aaron W Betts, Kyle A Davis, Kaitlyn G DiMarco, Colin D Hubbard, Tyler Kelly, Michael Thomas Miller, Morgan B Pendleton, Wade E Quilter, Jamie A Rhodine, Michael R Stephens, David J Lore, Joseph W Duke, Robert C Roach, Andrew W Subudhi","doi":"10.1152/japplphysiol.00076.2025","DOIUrl":"10.1152/japplphysiol.00076.2025","url":null,"abstract":"<p><p>Chronic exposure to high altitude leads to increases in hemoglobin mass (Hbmass), which may improve exercise performance and decrease acute mountain sickness (AMS) symptoms. We evaluated the influence of intravenous iron or erythropoietin (EPO) treatment on Hbmass, exercise performance, and AMS during a 14-day exposure to 3,094 m. Thirty-nine participants (12 F) completed the study conducted in Eugene, Oregon [sea level (SL), 130 m] and Leadville, Colorado (3,094 m). Participants were dosed with either a placebo (saline; <i>n</i> = 13), iron [Fe(III)-hydroxide sucrose 200 mg, 2 times; <i>n</i> = 14], or EPO (epoetin alfa 50 IU/kg, 3 times/wk; <i>n</i> = 12) at SL for ∼3.5 wk. Hbmass, exercise performance, and AMS symptoms were measured at SL before treatment and on <i>days 1</i>, <i>2</i>, <i>7</i>, <i>13</i>, and <i>14</i> at altitude. Absolute Hbmass (g) increased from SL and <i>day 1</i> to <i>day 13</i> (<i>P</i> < 0.0001) with no differences between treatment groups (<i>P</i> = 0.3868). Five-kilometer run times were slower at altitude compared with SL (<i>P</i> < 0.0001) and did not improve over the 14-day period at altitude for any group (<i>P</i> > 0.05). Hike times improved with acclimatization from <i>day 2</i> to <i>day 14</i> (<i>P</i> = 0.0018) in all groups, independent of treatment. The incidence and severity of AMS remained low across all participants and time points, regardless of treatment. In the current study and dosing, intravenous iron and EPO did not lead to improvements in Hbmass, exercise performance, or AMS with rapid ascent and residence at 3,100 m.<b>NEW & NOTEWORTHY</b> We investigated the influence of iron or erythropoietin treatment on hemoglobin mass, exercise performance, and acute mountain sickness (AMS) during a 14-day exposure to 3,094 m. With the given drug doses of iron [Fe(III)-hydroxide sucrose 200 mg, 2 times over 4 wk] and erythropoietin (epoetin alfa 50 IU/kg, 3 times/wk for 3 wk), we observed no differences in hemoglobin mass, aerobic exercise performance, or symptoms of AMS between groups relative to a placebo.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"954-963"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145006122","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":"Muscle metaboreflex activation via postexercise ischemia increases intercostal muscle blood flow index without evidence of local vasoconstriction in humans.","authors":"Masashi Ichinose, Mikie Nakabayashi, Yumie Ono","doi":"10.1152/japplphysiol.00577.2025","DOIUrl":"10.1152/japplphysiol.00577.2025","url":null,"abstract":"<p><p>Muscle metaboreflex is activated in limb skeletal muscles during high-intensity exercise that increases respiratory demand, but its effects on respiratory muscle blood flow remain unknown. Therefore, we investigated whether metaboreflex activation in the forearm alters blood flow in the intercostal muscles. Sixteen healthy young male subjects performed isometric handgrip at 30% of maximal voluntary contraction for 2 min, followed by either postexercise muscle ischemia (PEMI; metaboreflex activation condition) or a control recovery. Respiratory variables were controlled postexercise to match baseline levels. Microvascular blood flow index (BFI) in the left intercostal muscles was monitored using diffuse correlation spectroscopy, and cardiovascular variables were recorded. To reduce respiratory motion artifacts, BFI and vascular resistance index (VRI) were analyzed during breath-holding periods. During PEMI, both mean arterial pressure (MAP) and BFI were significantly elevated compared with rest [medians (IQRs), MAP: 92.1 (84.4-94.4) vs. 110.2 (102.4-116.4) mmHg, <i>P</i> < 0.001; BFI: 3.5 (2.8-4.9) vs. 4.2 (3.8-6.4) ×10^-9 cm²·s^-1, <i>P</i> = 0.002] and higher than that in the control condition [MAP: 91.0 (89.4-101.7) vs. 110.2 (102.4-116.4) mmHg, <i>P</i> < 0.001; BFI: 3.3 (2.5-4.5) vs. 4.2 (3.8-6.4) ×10^-9 cm²·s^-1, <i>P</i> < 0.001], whereas VRI remained unchanged [23.4 (19.0-29.9) vs. 23.2 (17.4-30.4) mmHg·(×10^-9 cm²·s^-1)^-1, <i>P</i> = 0.375]. These findings suggest that muscle metaboreflex activation enhances intercostal muscle BFI via a pressor response without evidence of significant local vasoconstriction. This study demonstrates reflex-mediated increases in intercostal muscle BFI and highlights the role of the metaboreflex in supporting ventilation.<b>NEW & NOTEWORTHY</b> We show for the first time that activation of the muscle metaboreflex in limb skeletal muscle increases intercostal muscle blood flow index via a pressor response without evidence of significant local vasoconstriction. This reflex-driven enhancement of respiratory muscle perfusion may serve to support ventilation during high-intensity exercise, revealing a novel integrative mechanism by which the cardiovascular system prioritizes oxygen delivery to respiratory muscles under metabolic stress.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"988-999"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145006163","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":"Vasoconstrictor responsiveness in resting and contracting skeletal muscle following an acute bout of exercise: impact of aging.","authors":"DongNyeuck Seo, Jack E Shelley, Erika Iwamoto, Darren P Casey","doi":"10.1152/japplphysiol.00549.2025","DOIUrl":"10.1152/japplphysiol.00549.2025","url":null,"abstract":"<p><p>Long-term exercise training can attenuate sympathetic vasoconstriction in both resting and contracting skeletal muscle; however, the impact of an acute bout of exercise on vasoconstrictor responsiveness and the influence of aging is unknown. Therefore, we tested the hypothesis that an acute bout of exercise will blunt sympathetic-mediated vasoconstriction in resting and contracting skeletal muscle of young and older adults. Twenty-one adults (10 young: 23 ± 5 yr and 11 older: 65 ± 8 yr) performed a rest and a rhythmic handgrip exercise trial before and after either 30 min of cycling exercise (60%-65% age-predicted maximal heart rate) or a time control period (seated rest). Lower body negative pressure (-30 mmHg) was applied during each trial to induce sympathetic-mediated vasoconstriction. Forearm blood flow (FBF; mL/min) was assessed via Doppler ultrasound and forearm vascular conductance (FVC; mL·min^-1·100 mmHg^-1) was calculated as the quotient of FBF and mean arterial pressure (mmHg). The acute bout of cycling exercise did not change vasoconstrictor responsiveness (% change FVC) in resting skeletal muscle in either age group (<i>P</i> > 0.05). However, vasoconstrictor responsiveness was attenuated in contracting skeletal muscle following the acute bout of cycling exercise in the entire group (-11.0 ± 5.7 to -8.2 ± 5.1%, <i>P</i> < 0.001), as well as separated by age (young: -6.7 ± 3.2 to -5.0 ± 4.0%, older: -14.9 ± 4.6 to -11.0 ± 4.2%, <i>P</i> < 0.01 for both). Our data indicate that an acute bout of exercise does not change vasoconstrictor responsiveness in resting skeletal muscle but enhances functional sympatholysis in young and older adults.<b>NEW & NOTEWORTHY</b> Data from the current study demonstrate that a single bout of exercise can enhance functional sympatholysis in contracting skeletal muscle. In addition, despite aging being associated with reduced functional sympatholysis, older adults experienced similar improvements following an acute bout of exercise as their young counterparts. These results suggest that the previously reported exercise training-induced improvements in functional sympatholysis may occur as early as the first session.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"976-987"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145029913","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":"Integrative physiological study of radiation-induced lung injury: effects on cardiac function and kidney integrity.","authors":"Lucas Rodrigues de Moraes, Maicon Luiz de Lima, Antônio Pedro Abido Ribeiro, Nazareth de Novaes Rocha, Tula Celeste Wilmart Gonçalves, Rodrigo Jorge Vianna Barbosa, Klara de Souza Roque, Giovanna Costa Ferreira Santos, Amanda Pereira da Cruz, Rodrigo Gonzaga Veras, Sabrina Araújo Ferreira, Pedro Henrique Lima da Conceição, Raquel Ferreira de Magalhães Sacramento, Adriana Lopes da Silva Vilardo, Vera Luiza Capelozzi, Camila Machado Baldavira, Sarah Aparecida Dos Santos Alves, Fernanda Ferreira Cruz, Patricia Rieken Macedo Rocco, Celso Caruso-Neves, Sergio Augusto Lopes de Souza, Lorenzo Ball, Pedro Leme Silva","doi":"10.1152/japplphysiol.00241.2025","DOIUrl":"10.1152/japplphysiol.00241.2025","url":null,"abstract":"<p><p>Radiotherapy is used to treat tumors in the chest, but can cause radiation-induced lung injury (RILI) in 5%-50% of patients. The study investigated changes in lung and heart function and kidney integrity in a model of RILI. Primary outcome was lung compliance at 12 wk. Secondary outcomes included analysis of ventilatory effort, cardiovascular function, and renal integrity. About 30 adult Wistar rats (8-10 wk old, 390 ± 22 g) were randomized into two groups: one received 15 Gray (Gy) of irradiation to the right lung radiation (RLR group, <i>n</i> = 20), whereas control group (CTRL group, <i>n</i> = 10) received no irradiation. After irradiation, echocardiography and chest computed tomography (CT) were performed every 3 wk, whereas respiratory mechanics and right ventricle systolic pressure (RVSP) were assessed at 12 wk. Lung tissue was analyzed for collagen deposition and immunohistochemistry markers, including signal transducer and activator of transcription-3 (STAT-3) and transforming growth factor-beta (TGF-β). Kidney tissue was evaluated for tubular cell spacing and collagen deposition. In RLR, compared with CTRL group, lung compliance reduced (0.24 ± 0.02 mL·cmH₂O^-1 vs. 0.29 ± 0.03 mL·cmH₂O^-1; <i>P</i> = 0.039), whereas respiratory effort increased. CT analysis demonstrated progressive left lung volume expansion over time. Radiation exposure increased lung macrophages, arterial wall thickness, fibroblast proliferation, and collagen deposition in peripheral and perivascular regions (<i>P</i> < 0.001). Moreover, both STAT-3- and TGF-β - positive cells were increased in lung parenchyma. Pulmonary hypertension developed, detected by echocardiography and confirmed by invasive RVSP measurement. RLR group exhibited increased kidney collagen deposition and tubular cell thickening (<i>P</i> = 0.002). These findings demonstrate the systemic impact of radiation on cardiorespiratory function and kidney integrity.<b>NEW & NOTEWORTHY</b> Radiotherapy is used to treat chest tumors, but may induce radiation-induced lung injury (RILI) in some patients. In the current RILI model, significant changes were observed in both irradiated and nonirradiated lungs. Increased right ventricle afterload and kidney morphological alterations were detected, suggesting vascular congestion. This study highlights the well-known impact of RILI on lungs but also emphasizes the often-overlooked effects on heart and kidneys in clinical practice.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1050-1063"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145199394","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":"The impact of menstrual phase on lower limb microvascular function, ERα, eNOS, and p-eNOS protein in premenopausal females.","authors":"Lindsay A Lew, James P Thoms, Dylan J Hian-Cheong, Emily J Ferguson, Jacob T Bonafiglia, Chris McGlory, Joe Quadrilatero, Brendon J Gurd, Kyra E Pyke","doi":"10.1152/japplphysiol.00848.2024","DOIUrl":"10.1152/japplphysiol.00848.2024","url":null,"abstract":"<p><p>There is variability in the impact of the menstrual phase on microvascular function with some studies reporting an increase from the early follicular (EF) to late follicular (LF) phase. Estradiol (E2) may increase nitric oxide bioavailability and thereby microvascular function through increasing estrogen receptor α (ERα), endothelial nitric oxide synthase (eNOS), and phosphorylated eNOS (p-eNOS) protein. It is unknown whether variability in ERα, eNOS, and p-eNOS protein levels drives menstrual cycle-related changes in microvascular endothelial function. We hypothesized that microvascular function would be positively related to ERα, eNOS, and p-eNOS protein across the menstrual cycle. Premenopausal females (21 ± 3 yr) completed two visits (EF and LF phase) to assess leg microvascular function (<i>n</i> = 23) and protein levels (<i>n</i> = 17). Microvascular function was quantified by passive leg movement hyperemia leg blood flow area under the curve (LBF AUC) and change to peak (LBF Δpeak). eNOS, p-eNOS, and ERα content were quantified from quadricep muscle biopsies. E2 increased from the EF to LF phase (<i>P</i> = 0.002). There were no phase differences in LBF AUC (<i>P</i> = 0.252) and LBF Δpeak (<i>P</i> = 0.477), or eNOS (<i>P</i> = 0.722), p-eNOS (<i>P</i> = 0.079), and ERα (<i>P</i> = 0.182) protein assessed via immunoblotting, or eNOS (<i>P</i> = 0.610) and p-eNOS (<i>P</i> = 0.510) assessed via immunofluorescence. E2, eNOS, and p-eNOS proteins were positively related to microvascular function (<i>P</i> < 0.05). This study does not support a group-level role of the EF to LF menstrual phase transition in influencing leg microvascular function or ERα, eNOS, and p-eNOS protein. Rather, it highlights that individual quantification of E2 and eNOS protein may be more indicative of microvascular function.<b>NEW & NOTEWORTHY</b> This study provides the first parallel assessments of microvascular function and estrogen-related protein content across the early to late follicular phases of the menstrual cycle in humans. Both microvascular function assessed via passive leg movement hyperemia and estrogen-related protein (eNOS, p-eNOS, and ERα) from skeletal muscle biopsies did not differ across phases; however, correlation analysis suggests a mechanistic link between estradiol, eNOS, and p-eNOS protein levels and peripheral microvascular function in premenopausal females.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"875-888"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144955400","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":"Hypoxic ventilatory decline in young healthy adults persists during moderate-intensity exercise in isocapnic hypoxia.","authors":"Antonia N Berdeklis, Benjamin P Thompson, Paolo B Dominelli","doi":"10.1152/japplphysiol.00053.2025","DOIUrl":"10.1152/japplphysiol.00053.2025","url":null,"abstract":"<p><p>Hypoxic ventilatory decline (HVD) is part of the mammalian ventilatory response to hypoxia and is characterized by a decline in ventilation that begins after 3-5 min of sustained, moderate hypoxia. Exercise is a powerful ventilatory stimulus that increases ventilation and chemosensor sensitivity. The extent to which these opposing ventilatory stimuli interact is not fully characterized. We compared the ventilatory response to moderate exercise during two conditions: during pre-established HVD and shortly after the onset of hypoxia but before the establishment of HVD. Eleven (<i>n</i> = 6 males) young, healthy participants completed three testing visits. <i>Day 1</i> was a maximal exercise test and <i>days 2</i> and <i>3</i> were randomized experimental visits separated by > 48 h. Each experimental visit began with a 5 min normoxic baseline followed by 15 min of rest and 15 min of exercise at 30% of peak power. The experimental visits differed in that, during the \"sustained hypoxia\" protocol (oxyhemoglobin saturation ∼80%), hypoxia began at the start of rest, whereas in the \"acute hypoxia\" protocol, hypoxia began 1 min before exercise. At the onset of exercise, ventilation was significantly lower in the sustained hypoxia protocol (-5.1 L·min^-1), suggesting a persistent blunting of ventilation. At end exercise, ventilation was not different between protocols (51.2 ± 11.6 vs. 50.5 ± 7.3 L·min^-1, for sustained and acute hypoxia, respectively). The percent decline in ventilation (HVD) was greater during the sustained hypoxia (-23 ± 13 vs. -14 ± 9%, <i>P</i> = 0.04). We conclude that HVD persists when acute exercise is imposed on sustained isocapnic hypoxia.<b>NEW & NOTEWORTHY</b> Imposing moderate-intensity exercise on acute, sustained isocapnic hypoxia in close temporal proximity showed evidence of hypoxic ventilatory decline in the first 15 min of exercise. The percent decline in ventilation during exercise was smaller than the hypoxic ventilatory decline at rest, indicating a blunting of the ventilatory decline when occurring together with exercise. Duration of pre-exercise hypoxic exposure should be considered when interpreting hypoxic exercise ventilation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1010-1018"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145053538","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 during artificial gravity preserves cardiorespiratory fitness but not orthostatic tolerance following 60 days of head-down bed rest (BRACE).","authors":"Eric T Hedge, Carol G Bryans, Carmelo J Mastrandrea, Christoph Siebenmann, Alan R Hargens, Lars L Karlsson, Richard L Hughson, Dag Linnarsson","doi":"10.1152/japplphysiol.00224.2025","DOIUrl":"10.1152/japplphysiol.00224.2025","url":null,"abstract":"<p><p>Exercise is a critical countermeasure to prevent cardiovascular deconditioning during spaceflight; however, exercise does not protect astronauts from postflight orthostatic intolerance. Artificial gravity (AG) by short-arm centrifugation can attenuate reductions in orthostatic tolerance following prolonged head-down bed rest (HDBR), but AG does not protect cardiorespiratory fitness. The European Space Agency hypothesized that exercise and AG countermeasures could be applied simultaneously to protect both cardiorespiratory fitness and orthostatic tolerance following prolonged HDBR. Twenty-four healthy men (age: 29 ± 6 yr, peak oxygen uptake: 47.5 ± 6.0 mL·min^-1·kg^-1) completed 60 days of HDBR and were randomized into either sedentary control (<i>n</i> = 8), exercise (<i>n</i> = 8), or exercise + AG (<i>n</i> = 8) groups. Exercise participants performed 30 min of high-intensity interval cycling on 49 of 60 days during HDBR. The exercise + AG group performed the same 30-min exercise program while spinning in supine position in a short-arm centrifuge to generate a head-to-foot acceleration. Peak oxygen uptake (HDBR × group: <i>P</i> < 0.001) was reduced in the control group following HDBR (Δ = -24 ± 5%) but was protected by the exercise (Δ = 0 ± 6%) and exercise + AG (Δ = 4 ± 6%) countermeasures. Time to presyncope was reduced in all groups (control: Δ = -9.0 ± 3.4 min, exercise: Δ = -12.4 ± 5.2 min, exercise + AG: Δ = -4.5 ± 8.8 min) following HDBR (main effect: <i>P</i> < 0.001). Activation of the muscle pump during exercise likely minimized the redistribution of blood volume into the legs and consequently, the simulated orthostatic stress experienced during centrifugation, preventing benefits of exercise + AG on orthostatic tolerance following HDBR. Therefore, AG by short-arm centrifugation should be implemented at rest or postexercise to protect orthostatic tolerance.<b>NEW & NOTEWORTHY</b> Exposing participants to artificial gravity (AG) while performing high-intensity interval cycling protects cardiorespiratory fitness after 60 days of head-down bed rest but not orthostatic tolerance. These effects are not different than performing exercise without AG. Accordingly, to gain the previously reported benefits of AG by short-arm centrifugation on the cardiovascular system, AG should be applied while participants are at rest or postexercise.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"943-950"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145069633","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":"The sense and control of standing balance in the presence of motor noise.","authors":"Lucas Mensink, Amin M Nasrabadi, Brandon G Rasman, Jean-Sébastien Blouin, Patrick A Forbes","doi":"10.1152/japplphysiol.00325.2025","DOIUrl":"10.1152/japplphysiol.00325.2025","url":null,"abstract":"<p><p>This study aimed to characterize motor noise in human standing balance and uncover mechanisms that enable the nervous system to robustly sense and control upright posture despite this variability. We conducted three experiments using a robotic balance simulator. First, we quantified the natural variability of ankle torques, revealing that torque variability was stable within preferred postures and increased only at more extreme orientations. The range of constant variability may be explained by passive mechanisms that contribute to plantarflexion torque along with the bilinear scaling of motor noise with torque magnitude. Together, these factors help maintain stable motor variability, despite the substantial increase (6% of <i>mgL</i>) in gravitational torque load. Second, we investigated perceptual thresholds for detecting the sensory consequences of artificially imposed torque noise, designed to replicate and amplify the variability of ankle torque during quiet standing. Participants detected the consequences of imposed torque when it exceeded ∼50% of baseline torque variability, which was accompanied by a twofold increase in whole body angular velocity variability. Third, we assessed the impact of artificially imposed torque noise on the vestibular control of balance. We found that the threshold for generating corrective responses remained unchanged, as increased variability in balance-correcting responses was accompanied by proportional increases in vestibulomotor gain. Collectively, these findings reveal that the nervous system accommodates motor noise by leveraging passive stiffness and the minimal scaling of motor noise at ankle torques near preferred postures, while also engaging robust error correction mechanisms-such as increased vestibulomotor gain-that operate outside conscious awareness.<b>NEW & NOTEWORTHY</b> This study reveals how the nervous system accommodates motor noise to maintain postural stability. In preferred postures, passive ankle stiffness and bilinear noise scaling naturally minimize torque variability. When challenged with artificially imposed torque noise, the system adaptively increases vestibulospinal gain-even at subperceptual torque noise levels-demonstrating a decoupling of balance control from conscious perception.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"918-933"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145000605","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 with overdressing for heat acclimation: a multilayered approach using biophysical modeling and two randomized crossover trials.","authors":"Andrew M Greenfield, Shaun C Brazelton, Billie K Alba, Phillip O Bodurtha, Karleigh E Bradbury, Aaron R Caldwell, Christopher L Chapman, Nisha Charkoudian, K Riley Connor, Koby Conz, Benjamin A Fry, Gabrielle E W Giersch, David H Gonzalez-Rojas, Molly E Heikkinen, David P Looney, Thomas A Mayer, Kathryn G McCarthy, Adam W Potter, Timothy P Rioux, Roy M Salgado, Afton D Seeley, MariaLena A Shaw, Xiaojiang Xu, Benjamin J Ryan","doi":"10.1152/japplphysiol.00624.2025","DOIUrl":"10.1152/japplphysiol.00624.2025","url":null,"abstract":"<p><p>Individuals who work in the heat, such as military personnel and athletes, are often required to rapidly transition from temperate or cooler climates to hot environments. Thus, acclimation strategies are needed for individuals lacking access to hot weather. We sought to develop and validate a practical exercise with overdressing protocol for heat acclimation. We began by using biophysical modeling to identify a combination of clothing and treadmill exercise (speed/duration) predicted to facilitate appropriate increases in core temperature in a gym-like environment (20°C/50% RH/1 mph wind). We tested this novel protocol (6 mph run for 30 min followed by 3.5 mph walk for 60 min in a standardized overdressing ensemble) against control exercise (shorts/t-shirt) using two randomized crossover trials in fit males and females. In <i>study I</i>, we showed that a single session of exercise with overdressing elicited significantly higher peak core temperature (38.9 ± 0.4 vs. 38.5 ± 0.3°C), skin temperature (35.3 ± 0.6 vs. 32.5 ± 0.7°C), and heart rate (166 ± 20 vs. 147 ± 16 beats/min) compared with control exercise (<i>P</i> < 0.01; <i>n</i> = 15). In <i>study II</i>, we conducted heat stress tests (60 min at 50% maximal oxygen uptake in 40°C/40%RH/3 mph wind in shorts/t-shirt) before and after five sessions of exercise with overdressing or control exercise (<i>n</i> = 12). Five days of exercise with overdressing in a gym-like environment significantly (<i>P</i> < 0.01) lowered resting core temperature (-0.3 ± 0.2°C), peak core temperature (-0.4 ± 0.2°C), skin temperature (-0.5 ± 0.6°C), and heart rate (-11 ± 11 beats/min) during exercise in the heat. These adaptations were superior compared with control exercise (interactions <i>P</i> < 0.05). This practical exercise with overdressing approach effectively induces heat acclimation in fit males and females without requiring hot weather.<b>NEW & NOTEWORTHY</b> We developed a novel exercise with overdressing protocol for heat acclimation and validated it using two randomized crossover trials. Five sessions of exercise with overdressing in a gym-like environment significantly lowered resting core temperature and peak core temperature, skin temperature, and heart rate during exercise in the heat. These adaptations were superior compared with five sessions of control exercise. This practical exercise with overdressing protocol induces heat acclimation without requiring hot weather.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"889-901"},"PeriodicalIF":3.3,"publicationDate":"2025-10-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"145006109","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}