Journal of applied physiology最新文献

{"title":"Peripheral antitussives affect temporal features of tracheobronchial coughing in cats.","authors":"Ivan Poliacek, Marcel Veterník, Lukas Martvon, Michal Simera, Lucia Cibulkova, Zuzana Kotmanova, Denisa Berikova, Donald C Bolser","doi":"10.1152/japplphysiol.00551.2024","DOIUrl":"10.1152/japplphysiol.00551.2024","url":null,"abstract":"<p><p>The influence of peripheral antitussive drugs on spatiotemporal features of coughing has not been reported. We hypothesized that this class of compounds would alter the cough motor pattern, in part, by lengthening cough phases. Peripherally acting antitussives, 3-aminopropylphosphinic acid (3APPi, 5 mg/kg) and levodropropizine (Levo, 3 mg/kg) were injected intravenously in anesthetized spontaneously breathing cats (13 males, 2 females; 4.38 ± 0.19 kg). Spatio-temporal analysis of cough induced by mechanical stimulation of the trachea showed significant reductions in cough number and expiratory cough efforts after the administration of each drug. A significant reduction in inspiratory cough efforts occurred after Levo. Both drugs induced temporal changes in the cough motor pattern, including prolongations of inspiratory phase, inspiratory-expiratory transition, total cough diaphragm activity, and total cough cycle duration. Levo also significantly lengthened the expiratory phase of cough. A shortening of the overlap between diaphragm and abdominal activity and cough abdominal electromyogram (EMG) activity was observed after the administration of 3APPi. No significant changes in cardiorespiratory data were seen, with the exception of prolonged expiratory phase after 3APPi and lower blood pressure after Levo. Peripherally induced cough suppression is accompanied with changes in cough temporal characteristics that are not observed after the administration of centrally acting antitussives. The motor output produced by the cough central pattern generator differs significantly when coughing is perturbed by peripherally and centrally acting antitussives.<b>NEW & NOTEWORTHY</b> In a study on anesthetized cats, peripherally acting antitussives 3-aminopropylphosphinic acid (3APPi) and levodropropizine (Levo) significantly reduced cough number and expiratory efforts, with Levo also reducing inspiratory efforts. Both antitussives altered the cough motor pattern, extending various cough phases. 3APPi shortened diaphragm-abdominal activity overlap, whereas Levo decreased the respiratory rate. These changes contrast with those induced by centrally acting antitussives.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"22-30"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667983","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 contraction frequency during high-intensity training on fatigue resistance and aerobic adaptations in mouse skeletal muscle.","authors":"Azuma Naito, Tatsuya Sato, Iori Kimura, Nao Tokuda, Nao Yamauchi, Hiroyori Fusagawa, Takashi Yamada","doi":"10.1152/japplphysiol.00530.2024","DOIUrl":"10.1152/japplphysiol.00530.2024","url":null,"abstract":"<p><p>In high-intensity and sprint interval training, the frequency of contractions is typically higher compared with moderate-intensity continuous training, but it remains unclear whether this contributes to the effective increase in fatigue resistance mechanisms. Here, we investigated the role of contraction frequency in high-intensity training on endurance adaptations of mouse skeletal muscle. Male C57BL/6 mice were divided into groups based on high (0.25 s contraction every 0.5 s) and low (0.25 s contraction every 4.5 s) contraction frequencies, with either 360 contractions per session (Hi360 and Lo360) or 30 contractions per session (Hi30 and Lo30). The plantar flexor muscles were stimulated using in vivo supramaximal electrical stimulation, where all muscle fibers were maximally activated, every other day for 5 wk. In both the Hi360 and Lo360 groups, where force production declined to less than 40% of the initial value during the training session, muscle endurance, and mitochondrial content and respiratory capacity, were increased to a similar extent. In contrast, the rate of torque decline during the training session was more pronounced in the Hi30 group compared with the Lo30 group. In response, the Hi30 group, but not the Lo30 group, exhibited increased fatigue resistance and mitochondrial respiration, which was accompanied by increased peroxisome proliferator-activated receptor gamma coactivator-1 alpha (PGC-1α) expression and an activation of AMP-activated protein kinase (AMPK)/unc-51-like autophagy activating kinase 1 (Ulk1) pathway. These data suggest that the frequency of contractions is a critical factor in determining the efficient enhancement of mitochondrial respiratory capacity and muscle endurance through high-intensity training, presumably due to promotion of mitochondrial quality control.<b>NEW & NOTEWORTHY</b> We investigated how training programs varying in contraction frequencies impact the endurance capacity of mouse skeletal muscle, using in vivo supramaximal electrical stimulation to ensure maximal activation of all muscle fibers. Increasing the frequency of contractions during high-intensity training led to increased fatigue resistance and mitochondrial respiratory capacity with fewer repetitions per training session, highlighting the pivotal importance of contraction frequency during exercise training in shaping endurance adaptations in skeletal muscle.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"107-120"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142828454","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":"How to train your graduate students to (want to) win you awards.","authors":"W Larry Kenney","doi":"10.1152/japplphysiol.00698.2024","DOIUrl":"10.1152/japplphysiol.00698.2024","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"270-273"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142800873","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":"Combined exercise hinders the progression of pulmonary and right heart harmful remodeling in monocrotaline-induced pulmonary arterial hypertension.","authors":"Luciano Bernardes Leite, Leôncio Lopes Soares, Alexandre Martins Oliveira Portes, Bruna Aparecida Fonseca da Silva, Taís Rodrigues Dias, Thayana Inácia Soares, Mirian Quintão Assis, Luiz Otávio Guimarães-Ervilha, Miguel Araújo Carneiro-Júnior, Pedro Forte, Mariana Machado-Neves, Emily Correna Carlo Reis, Antônio José Natali","doi":"10.1152/japplphysiol.00379.2024","DOIUrl":"10.1152/japplphysiol.00379.2024","url":null,"abstract":"<p><p>The aim of this study was to test whether combined physical exercise training of moderate intensity executed during the development of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) hinders the progression of pulmonary and right heart harmful functional and structural remodeling in rats. Wistar rats were injected with MCT (60 mg/kg) and after 24 h were exposed to a combined exercise training program: aerobic exercise (treadmill running-60 min/day; 60% of maximum running speed); and resistance exercise (vertical ladder climbing-15 climbs; 60% of maximum carrying load), on alternate days, 5 days/wk, for ∼3 wk. After euthanasia, the lung and right ventricle (RV) were excised and processed for histological, single myocyte, and biochemical analyses. Combined exercise increased the tolerance to physical effort (time until fatigue and relative maximum load) and prevented increases in pulmonary artery resistance (acceleration time (TA)/ejection time (TE)] and reductions in RV function [tricuspid annular plane systolic excursion (TAPSE)]. Moreover, in myocytes isolated from the RV, combined exercise preserved contraction amplitude, as well as contraction and relaxation velocities, and inhibited reductions in the amplitude and maximum speeds to peak and to decay of the intracellular Ca²⁺ transient. Furthermore, combined exercise avoided RV (RV weight, cardiomyocyte, extracellular matrix, collagen, inflammatory infiltrate, and extracellular matrix) and lung (pulmonary alveoli and alveolar septum) harmful structural remodeling. In addition, combined exercise restricted RV [nitric oxide (NO) and carbonyl protein (CP)] and lung [catalase (CAT), glutathione S-transferase (GST), and NO] oxidative stress. In conclusion, the applied combined exercise regime hinders the progression of pulmonary and right heart functional and structural harmful remodeling in rats with MCT-induced PAH.<b>NEW & NOTEWORTHY</b> This study reveals that combined exercise improves tolerance to physical effort, prevents increases in pulmonary artery resistance, and conserves the right heart function during the progression of pulmonary arterial hypertension. Our analyses show that combined exercise hinders harmful right ventricular and lung structural remodeling and oxidative stress, which reflects in the maintenance of right ventricular myocytes' contractile function by preserving the intracellular calcium cycling. An attenuated progression of the disease impacts positively on its prognosis.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"182-194"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142750395","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":"New insights into the impact of bed rest on lumbopelvic muscles: a computer-vision model approach to measure fat fraction changes.","authors":"Evert O Wesselink, Julie Hides, James M Elliott, Mark Hoggarth, Kenneth A Weber, Sauro E Salomoni, Vienna Tran, Kirsty Lindsay, Luke Hughes, Tobias Weber, Jonathan Scott, Paul W Hodges, Nick Caplan, Enrico De Martino","doi":"10.1152/japplphysiol.00502.2024","DOIUrl":"10.1152/japplphysiol.00502.2024","url":null,"abstract":"<p><p>Space agencies plan crewed missions to the Moon and Mars. However, microgravity-induced lumbopelvic deconditioning, characterized by an increased fat fraction (FF) due to reduced physical activity, poses a significant challenge to spine health. This study investigates the spatial distribution of FF in the lumbopelvic muscles to identify the most affected regions by deconditioning, utilizing a computer-vision model and a tile-based approach to assess FF changes. Twenty-four healthy individuals (8 F) were recruited, and automatic segmentation of the lumbopelvic muscles was applied before and after 59 days of head-down tilt bed rest (HDTBR + 59) and 13 days of reconditioning (R + 13). Axial Dixon sequence images were acquired from 3 T magnetic resonance imaging. FF in the lumbar multifidus (LM), lumbar erector spinae (LES), quadratus lumborum, psoas major, gluteus maximus (GMax), gluteus medius (GMed), and gluteus minimus (GMin) muscles from the upper margin of L1 vertebra to the inferior border of GMax muscle were automatically derived using a computer-vision model. Lumbar muscles were segmented into eight tiles (superficial and deep, lateral to medial), and gluteal muscles into regions (anterior/superior for GMed and GMin, superior/inferior for GMax). At HDTBR + 59, the deep centrolateral region at L5/S1 for LM (18.7 ± 15.7%, <i>P</i> < 0.001; <i>d</i> = 0.97) and the deep medial region at Upper L4 for LES (5.4 ± 5.9%, <i>P</i> < 0.001; <i>d</i> = 0.34) showed the largest increase in FF compared with baseline data collection. These regions did not recover at R + 13 (<i>P</i> < 0.05; <i>d</i> ≥ 0.25). These findings highlight the need to target deep fascicles of LM and LES in countermeasure strategies to mitigate microgravity-induced lumbopelvic deconditioning, optimizing spine health, and performance.<b>NEW & NOTEWORTHY</b> This study reveals novel insights into fat fraction changes in lumbopelvic muscles after 60 days of head-down bed rest and 13 days of reconditioning. Lipids increased in the deep regions of the lumbar multifidus (LM) and lumbar erector spinae (LES), particularly at lower vertebral levels, and persisted after reconditioning. These findings highlight the need to target deep fascicles of LM and LES in future countermeasures to mitigate microgravity-induced deconditioning and optimize spine health.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"157-168"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142750410","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 interaction of adenosine and dopamine in modulating the consequences of central nervous system oxygen toxicity.","authors":"Benming You, Guorong Shi, Yanan Zhang, Xiang Fu, Qian Li, Yu Wang, Guoyang Huang, Yiqun Fang, Runping Li","doi":"10.1152/japplphysiol.00500.2024","DOIUrl":"10.1152/japplphysiol.00500.2024","url":null,"abstract":"<p><p>Hyperbaric oxygen (HBO) refers to pure oxygen with a pressure greater than 1 atmospheres absolute (ATA), and when the pressure is too high, it can cause convulsive attacks. Adenosine and dopamine have been shown to be closely associated with HBO-induced convulsion seizures, and their receptors exhibited a coexisting relationship of mutual antagonism on the membrane of nerve cells. We explored the influence of adenosine and dopamine interplay on the occurrence of oxygen convulsion. Rats were individually exposed to HBO of 6 ATA and treated with adenosine, dopamine, and their receptor modulators separately and jointly, with the latency of convulsion onset recorded. In addition, after administering adenosine to rats and exposing them to HBO for 30 min, the content of dopamine and its metabolites and the activity of enzymes related to their metabolism were measured. The results revealed that dopamine was effective in resisting convulsion (>60 min vs. 32.53 ± 5.31 min, <i>P</i> = 0.000), and low-dose adenosine partially counteracted its effect (>60 min vs. 28.18 ± 6.24 min, <i>P</i> = 0.002). The combined use of adenosine A1 and dopamine D1 receptor modulators significantly impacted the incidence of convulsion. The activation or inhibition of the A2A receptor had a particularly significant impact on convulsion, whereas modulating the D2 receptor did not affect their effects. The combination of A1 agonist and D2 agonist was highly effective in resisting convulsion (>60 min vs. 32.53 ± 5.31 min, <i>P</i> = 0.000). Exposure to HBO accelerated the metabolism of dopamine to its end products, which may be related to the enhanced activity of monoamine oxidase (MAO). Adenosine can inhibit MAO activity (0.0766 ± 0.0150 U/mg.prot vs. 0.1055 ± 0.0086 U/mg.prot, <i>P</i> = 0.004), maintaining a higher level of dopamine (1.820 ± 0.379 mg/g vs. 0.602 ± 0.087 mg/g, <i>P</i> = 0.000). The study demonstrated that dopamine plays a significant role in oxygen convulsion and adenosine can affect dopamine metabolism. The interaction between them can have a crucial impact on the occurrence of oxygen convulsion. The findings offer a novel perspective for further investigating the mechanism of oxygen convulsion and exploring effective preventive strategies.<b>NEW & NOTEWORTHY</b> The interaction between adenosine and dopamine is critically important in determining the incidence of oxygen convulsion. Simultaneous regulation of both adenosine and dopamine offers a superior approach to counteract oxygen convulsion, achieving a synergistic effect exceeding the sum of their individual impacts. These findings provide new directions and insights for future in-depth and systematic exploration of the pathogenesis of central nervous system oxygen toxicity.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"169-181"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142728909","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":"In vivo intracellular Ca²⁺ profiles after eccentric rat muscle contractions: addressing the mechanistic bases for repeated bout protection.","authors":"Ayaka Tabuchi, Yudai Kikuchi, Ryo Takagi, Yoshinori Tanaka, Daisuke Hoshino, David C Poole, Yutaka Kano","doi":"10.1152/japplphysiol.00164.2024","DOIUrl":"10.1152/japplphysiol.00164.2024","url":null,"abstract":"<p><p>Eccentric contractions (ECC) are accompanied by the accumulation of intracellular calcium ions ([Ca²⁺]_i) and induce skeletal muscle damage. Suppressed muscle damage in repeated bouts of ECC is well characterized; however, whether it is mediated by altered Ca²⁺ profiles remains unknown. We tested the hypothesis that repeated ECC suppresses Ca²⁺ accumulation via adaptations in Ca²⁺ regulation. Male Wistar rats were divided into two groups: ECC single bout (ECC-SB) and repeated bout (ECC-RB). Tibialis anterior (TA) muscles were subjected to ECC (40 times, 5 sets) once (ECC-SB) or twice 14 days apart (ECC-RB). Under anesthesia, the TA muscle was loaded with Ca²⁺ indicator Fura 2-AM, and the 340/380 nm ratio was evaluated as [Ca²⁺]_i. Ca²⁺ handling proteins were measured by Western blots. ECC induced [Ca²⁺]_i increase in both groups, but ECC-RB evinced a markedly suppressed [Ca²⁺]_i (Time: <i>P</i> < 0.01, Group: <i>P</i> = 0.0357). Five hours post-ECC, in contrast to the localized [Ca²⁺]_i accumulation in ECC-SB, ECC-RB exhibited lower and more uniform [Ca²⁺]_i (<i>P</i> < 0.01). In ECC-RB, mitochondria Ca²⁺ uniporter complex (MCU) components MCU and MICU2 were significantly increased pre-second ECC bout (<i>P</i> < 0.01), and both SERCA1 and MICU1 were better preserved after contractions (<i>P</i> < 0.01). Fourteen days after novel ECC, skeletal muscle mitochondrial Ca²⁺ regulating proteins were elevated. Following subsequent ECC, [Ca²⁺]_i accumulation and muscle damage were suppressed and SERCA1 and MICU1 preserved. These findings suggest that tolerance to a subsequent ECC bout is driven, at least in part, by enhanced mitochondrial and sarcoplasmic reticulum Ca²⁺ regulation.<b>NEW & NOTEWORTHY</b> We demonstrated a reduced [Ca²⁺]_i profile with suppressed muscle damage after a repeated bout of ECC in vivo: the ECC-induced immediate [Ca²⁺]_i increase was suppressed and the persistence of increased [Ca²⁺]_i with localized accumulation was diminished after repeated ECC. This effect occurred consonant with the upregulation of the mitochondrial Ca²⁺ uniporter complex and better preservation of SERCA1 and MICU1. These findings suggest that the mechanistic bases for repeated bout protection involve adaptation of Ca²⁺ regulation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1-12"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142639072","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":"Evidence on sex differences in sports performance.","authors":"Michael J Joyner, Sandra K Hunter, Jonathon W Senefeld","doi":"10.1152/japplphysiol.00615.2024","DOIUrl":"10.1152/japplphysiol.00615.2024","url":null,"abstract":"<p><p>Sex differences in sports performances continue to attract considerable scientific and public attention, driven in part by high profile cases of: <i>1</i>) biological male (XY) athletes who seek to compete in the female category after gender transition, and <i>2</i>) XY athletes with medical syndromes collectively known as disorders or differences of sex development (DSDs). In this perspective, we highlight scientific evidence that informs eligibility criteria and applicable regulations for sex categories in sports. There are profound sex differences in human performance in athletic events determined by strength, speed, power, endurance, and body size such that males outperform females. These sex differences in athletic performance exist before puberty and increase dramatically as puberty progresses. The profound sex differences in sports performance are primarily attributable to the direct and indirect effects of sex-steroid hormones and provide a compelling framework to consider for policy decisions to safeguard fairness and inclusion in sports.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"274-281"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142882038","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 body posture on pulmonary diffusing capacity at rest and during exercise in endurance-trained and untrained individuals.","authors":"Andrew R Brotto, Stephanie de Waal, Andrew W D'Souza, Rhys I Beaudry, Cameron M Ehnes, Sophie É Collins, Desi P Fuhr, Sean van Diepen, Michael K Stickland","doi":"10.1152/japplphysiol.00447.2024","DOIUrl":"10.1152/japplphysiol.00447.2024","url":null,"abstract":"<p><p>Endurance-trained athletes exhibit a greater diffusing capacity for carbon monoxide (DLCO) at rest and during exercise as compared with untrained individuals; however, the mechanism(s) are unclear. The supine position translocates blood centrally and can be used to investigate DLCO responses independent of metabolic rate. We hypothesized that endurance-trained individuals would have a greater DLCO response to postural change at rest as compared with untrained and that the supine position would elicit a greater DLCO response as compared with the upright position during exercise in both groups. Fourteen endurance-trained (Trained) individuals (V̇o_2peak: 61.1 ± 4.4 mL·kg^-1·min^-1) and 14 untrained individuals (V̇o_2peak: 37.4 ± 3.0 mL·kg^-1·min^-1) completed DLCO maneuvers at rest and during exercise in the upright and supine position. At rest, there was a significant group-by-position interaction (<i>P</i> = 0.02) effect on DLCO with post hoc analysis determining DLCO increased from upright to supine position in Trained (<i>P</i> < 0.01), but not untrained (<i>P</i> = 0.58). There was no effect of position on exercising DLCO (<i>P</i> = 0.16) regardless of group; however, pulmonary capillary blood volume (V_C) was increased with supine exercise (<i>P</i> = 0.03). There was an apparent plateau in DLCO and V_C in the Trained group near-maximal exercise as Trained failed to increase DLCO (<i>P</i> = 0.25) and Vc (<i>P</i> = 0.46) up to near-maximal exercise. Trained individuals demonstrate greater DLCO recruitment with postural change at rest suggesting a greater ability to recruit/distend the pulmonary microvasculature. However, the supine position did not augment DLCO as compared with upright position in Trained individuals near-maximal exercise, suggesting a plateau may be reached at maximal exercise.<b>NEW & NOTEWORTHY</b> We demonstrate that the supine position increases resting DLCO significantly more in endurance-trained individuals as compared with untrained individuals. Furthermore, the supine position increases pulmonary capillary blood volume, but not diffusing capacity during exercise. Lastly, there was an apparent plateau in DLCO and V_C in the Trained group suggesting the pulmonary microvasculature may reach a morphological limit.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"301-310"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142835957","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":"Respiratory muscle strength pre- and post-maximal apneas in a world champion breath-hold diver.","authors":"Joseph W Duke, Colin D Hubbard, Dario Vrdoljak, Geoff B Coombs, Andrew T Lovering, Ivan Drvis, Željko Dujić, Nikola Foretic","doi":"10.1152/japplphysiol.00671.2024","DOIUrl":"10.1152/japplphysiol.00671.2024","url":null,"abstract":"<p><p>Maximal static dry, that is, on land, apneas (breath-holds) result in severe hypoxemia and hypercapnia and have easy-going and struggle phases. During the struggle phase, the respiratory muscles involuntarily contract against the closed glottis in increasing frequency and magnitude, that is, involuntary breathing movements (IBMs). IBMs during maximal static apnea have been suggested to fatigue respiratory muscles, but this has yet to be measured. Thus, the purpose of this study was to quantify respiratory muscle strength pre- and post-apneas in an elite, world champion, world record-holding apneist. To do so, maximal inspiratory and expiratory pressure maneuvers (MIP and MEP, respectively) were performed pre- and post-apnea protocol, which included three preparatory apneas with 2.5-min rest. All preparatory apneas were ended after the participant reported 7-10 IBMs. Next, he performed three maximal static dry apneas with 5-min rest in between. The participant had maximal apneas lasting 363, 408, and 460 s. Including preparatory apneas, the participant's total apnea duration was 33.4 min in 57.0 min. Following the apnea protocol, that is, pre versus post, there was no change in MIP (-124.2 vs. -123.6 cmH₂O) or MEP (259.4 vs. 262.5 cmH₂O). These data, albeit in a single individual, suggest that respiratory muscle strength is not impacted by maximal static breath-holds. This could be the result of training and/or be a feature of this individual that allows him to excel in this sport.<b>NEW & NOTEWORTHY</b> Previous work has suggested that respiratory muscle fatigue may result from maximal breath-holds but this has not been measured. We measured respiratory muscle strength pre- and post-maximal apneas in a world champion breath-hold diver. We found no change in respiratory muscle strength following a series of apneas. This may be an adaptation of the diver's training or a feature of their physiology that allows them to be successful in this physiologically challenging sport.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"66-72"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142667992","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}