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 high-intensity interval training and moderate-intensity continuous training on neural dynamics and firing in the CA1-MEC region of mice.","authors":"Yuncheng Liu, Shiqiang Chen, Junliang Li, Zengfei Song, Jihui Wang, Xiping Ren, Yongdong Qian, Wei Ouyang","doi":"10.1152/japplphysiol.00778.2024","DOIUrl":"10.1152/japplphysiol.00778.2024","url":null,"abstract":"<p><p>The aim of this study is to investigate the differential impacts of high-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on neural circuit dynamics and neuronal firing in the hippocampal CA1 subregion (CA1) region and medial entorhinal cortex (MEC) of mice. Forty-two male ICR mice were randomized into control, HIIT, and MICT groups. Electrophysiological recordings were performed pre- and postintervention to assess neural circuit dynamics and neuronal firing patterns in the CA1-MEC pathway. Both exercise protocols increased local field potential (LFP) coherence, with MICT showing a more pronounced effect on δ and γ coherences (<i>P</i> < 0.05). Both modalities reduced δ power spectral density (PSD) (HIIT, <i>P</i> < 0.05; MICT, <i>P</i> < 0.01) and elevated θ, β, and γ PSDs. Neuronal firing frequency improved in both CA1 and MEC following HIIT and MICT (<i>P</i> < 0.05). HIIT enhanced firing regularity in CA1 (<i>P</i> < 0.05), whereas MICT improved regularity in both regions (<i>P</i> < 0.05). Both protocols reduced firing latency (HIIT, <i>P</i> < 0.05; MICT, <i>P</i> < 0.01) and enhanced burst firing ratio, interburst interval (IBI), burst duration (BD), and LFP phase locking (<i>P</i> < 0.05 or <i>P</i> < 0.01). Notably, MICT significantly improved spatial working memory and novel recognition abilities, as evidenced by increased novel arm time, entries, and preference index (<i>P</i> < 0.01). This study reveals that both HIIT and MICT positively impact neural processing and information integration in the CA1-MEC network of mice. Notably, MICT exhibits a more pronounced impact on neural functional connectivity and cognitive function compared with HIIT. These findings, coupled with the similarities in hippocampal electrophysiological characteristics between rodents and humans, suggest potential exercise-mediated neural plasticity and cognitive benefits in humans.<b>NEW & NOTEWORTHY</b> This study is the first to investigate HIIT and MICT's effects on neural activity in the mouse CA1-MEC circuit, demonstrating that exercise modulates processing, enhances integration, and boosts cognitive performance. Due to similar hippocampal electrophysiology in rodents and humans during movement and navigation, our findings suggest implications for human brain neural changes, advancing the understanding of neurophysiological mechanisms underlying exercise-cognition interactions and informing exercise recommendations for cognitive health.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"31-44"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142716118","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":"Stress appraisal is associated with sympathetic neural reactivity to mental stress in humans.","authors":"Jeremy A Bigalke, Neha A John-Henderson, Jason R Carter","doi":"10.1152/japplphysiol.00678.2024","DOIUrl":"10.1152/japplphysiol.00678.2024","url":null,"abstract":"<p><p>Muscle sympathetic nerve activity (MSNA) responsiveness to mental stress is highly variable between individuals. Although stress perception has been posited as a contributor to the MSNA variability during mental stress, prior studies have been inconclusive. Furthermore, the importance of stress appraisal and coping on MSNA reactivity to mental stress has not been investigated. We hypothesize that appraisal of mental stress as a threat (i.e., perceived demands of stress exceed coping resources) versus a challenge (i.e., perceived coping resources sufficient for demands of stress) would be associated with greater MSNA reactivity. Twenty healthy adults (11 males, 9 females, 21 ± 3 yr, 23 ± 3 kg/m²) participated. Beat-by-beat blood pressure (finger plethysmography), heart rate (electrocardiography), and MSNA (microneurography) were recorded during a 10-min quiet rest followed by the Trier Social Stress Test (TSST). After each phase of the TSST (i.e., speech prep, speech, and mental arithmetic), participants reported threat versus challenge appraisal. Endorsement of a threat appraisal was positively associated with changes in MSNA burst frequency (<i>r</i> = 0.548, <i>P</i> = 0.018), burst incidence (<i>r</i> = 0.599, <i>P</i> = 0.009), and total MSNA (<i>r</i> = 0.697, <i>P</i> = 0.037) during the speech stress period. Moreover, increases in threat appraisal across tasks was associated with elevated MSNA burst frequency (<i>r</i> = 0.531, <i>P</i> = 0.023), incidence (<i>r</i> = 0.512, <i>P</i> = 0.030), and total MSNA (<i>r</i> = 0.727, <i>P</i> = 0.027) responsiveness. These findings support an association between stress appraisal processes and postganglionic sympathetic neural reactivity to psychosocial stress and may partially explain interindividual variability in MSNA responses to mental stress.<b>NEW & NOTEWORTHY</b> The present study investigated the association between stress appraisal and muscle sympathetic nerve activity (MSNA) reactivity to the Trier Social Stress Test. Appraisal of the stress task as a threat (i.e., perceived inability to cope with the demands of the task) was associated with exaggerated MSNA reactivity to mental stress in humans. Threat appraisal is associated with exaggerated sympathetic reactivity to stress, potentially underlying the commonly observed interindividual variability in MSNA responsiveness to mental stress.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"55-65"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142728906","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":"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}

{"title":"Voluntary activation of maximal single and all finger power grip contractions.","authors":"Daanish Chauhan, Tivyan Aruneethan, Tina Tran, Jennifer Zarnett-Klein, Eshaan Shah, Sarira Behnia, Michael T Paris","doi":"10.1152/japplphysiol.00650.2024","DOIUrl":"10.1152/japplphysiol.00650.2024","url":null,"abstract":"<p><p>When all four fingers are engaged together during a grip strength contraction, the force produced by an individual finger is less than the force produced when it acts in isolation. The purpose of this study was to evaluate whether the reduced force output of a digit during an all-finger grip contraction is due to a decline in voluntary activation. Fifteen young adults (<i>n</i> = 7 females) completed voluntary contractions of the index finger in isolation and all fingers together in a dynamometer capable of separately recording forces from each finger during voluntary and electrically evoked contractions. The median and ulnar nerves were electrically stimulated simultaneously at the elbow to record individual finger flexion forces from doublet (100 Hz) pulses. Doublet stimulations were applied during and immediately following contractions at 50, 65, 85, and 100% maximal voluntary contraction (MVC) forces. Two-way ANOVAs were used to compare the effects of sex and finger (single vs. all) on flexion forces and voluntary activation. The index finger produced ∼25% more force when engaged in isolation compared with the all-finger contraction; however, there were no differences in voluntary activation between the single and all-finger MVCs (<i>P</i> = 0.344). The index finger force deficit was larger in females compared with males (34 vs. 18%, <i>P</i> = 0.030), but this was not explained by sex-related differences in voluntary activation. These data indicate that the additional force produced during single-finger contractions is not due to an alteration in voluntary activation, as all-finger contractions display near-maximal activation of each digit.<b>NEW & NOTEWORTHY</b> The deficit in finger flexion force when multiple digits are engaged is well characterized and often attributed to reduced motor unit activation. Using a custom-built, multifinger dynamometer, we report that the index-finger force deficit may not be related to a deficit in voluntary activation. Furthermore, the index-finger force deficit was greater in females compared with males, but this was also not related to sex-related differences in voluntary activation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"45-54"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142728910","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":"Sex-related hypothalamic-pituitary-gonadal and hypothalamic-pituitary-adrenal axis adaptation during military training.","authors":"Robert M Gifford, Thomas J O'Leary, Rebecca L Knight, Sophie L Wardle, Craig L Doig, Richard A Anderson, Julie P Greeves, Rebecca M Reynolds, David R Woods","doi":"10.1152/japplphysiol.00691.2024","DOIUrl":"10.1152/japplphysiol.00691.2024","url":null,"abstract":"<p><p>Reproductive endocrine function adapts to psychological, environmental, and energy-associated stressors. Multistressor environments upregulate hypothalamic-pituitary-adrenal (HPA) axis, causing suppression of the hypothalamic-pituitary-gonadal (HPG) axis, but it is not known if this pattern or its magnitude is sex biased. We compared HPG and HPA axis activity in 9 men and 34 women undergoing Army training. One-hour low-dose gonadorelin and Synacthen tests were conducted at 1 and 29 wk, measuring gonadotrophins and cortisol. Cortisol was measured from hair every 3 mo. Morning and evening salivary cortisol and psychometric questionnaires were measured at six timepoints. Sexes were compared over time by two-way ANOVA. Gonadotrophin responses were significantly higher in women than men in <i>week 1</i>, but no sex difference was seen at <i>week 29</i> (no significant sex × time interaction). <i>Week 1</i> cortisol response was higher among men, but <i>week 29</i> cortisol response was higher among women (sex × time <i>F</i>_(1,44) = 18.0, <i>P</i> < 0.001). Hair cortisol was higher among women than men beforehand, not different between sexes during the first 3 mo, and significantly higher among women during training <i>months 5</i>-<i>11</i> (<i>F</i>_(3,15) = 3.25, <i>P</i> = 0.024). Morning salivary cortisol was higher among women in <i>weeks 8</i> and <i>14</i>, but higher among men in <i>week 29</i> (<i>F</i>_(4,76) = 4.0, <i>P</i> = 0.005). No differences were seen in evening salivary cortisol. Psychometrics did not change or differ between sexes. HPA axis responses to military training were greater among women than men. HPG axis responses suggest greater downregulation among women. These findings will enable equitable and individualized management of people undergoing periods of intensive physical stress.<b>NEW & NOTEWORTHY</b> We conducted a comprehensive comparison of adrenal and reproductive function in men and women undergoing 11-mo military training. We found progressively elevated cortisol levels and dynamic cortisol response to stress among women, but not men, and suppression of reproductive function among women. The physiological impact of stressful military training was greater among women than men; this could not be explained by energy balance, and sex-specific effects of sleep, socio-ethnographic, or other stressors may be responsible.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"13-21"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142728905","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"An acute bout of 4 x 4-minute or 10 x 1-minute HIIT improves beta cell glucose sensitivity in post-menopausal females with type 2 diabetes: a secondary analysis.","authors":"J L Low, A Marcotte-Chénard, R Tremblay, H Islam, K Falkenhain, W M Mampuya, A Mari, A McManus, E Riesco, J P Little","doi":"10.1152/japplphysiol.00777.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00777.2024","url":null,"abstract":"<p><p><b>Aims/hypothesis:</b> Improvements in glycemic control following acute exercise are typically attributed to improved post-exercise insulin sensitivity (IS) with comparatively little known about how acute exercise impacts beta cell function, especially in post-menopausal females. We determined how two high-intensity interval training (HIIT) protocols, matched for total estimated energy expenditure, impact beta cell function in post-menopausal females with type 2 diabetes. <b>Methods:</b> Thirteen post-menopausal females (70 ± 5 years; 12 ± 7 years since diagnosis, 80.9 ± 13.8 kg, 32.4 ± 5.6 kg*m²; HbA1c - 49.8 ± 10.3 mmol/mol [6.7 ± 1.0]) living with type 2 diabetes were included in this semi-randomized crossover trial. The trial involved an initial resting control condition followed by two HIIT conditions [4 X 4-minute HIIT (HIIT4) and 10 X 1-minute HIIT (HIIT10)] completed in a randomized order 2-4 days apart. Beta cell function (glucose sensitivity) and insulin sensitivity were determined from a 2 h mixed-meal tolerance test performed 2 hours after rest or HIIT. <b>Results:</b> Both HIIT4 and HIIT 10 significantly improved beta cell glucose sensitivity compared to control (15 pmol*min^-1*m^-2[mmol/L]^-1, [95% CI 6, 23]; p= 0.002 and 16 pmol*min^-1*m^-2[mmol/L]^-1, [95% CI 7, 25]; p= 0.002, respectively), with no difference between HIIT protocols (1 [-8, 10], P = 0.79). There were no significant differences in IS metrics (Matsuda index, OGIS, Stumvoli, and QUICKI) between the conditions. <b>Conclusions/interpretation:</b> An acute bout of 4 X 4-minute or 10 X 1-minute HIIT improves beta cell glucose sensitivity in post-menopausal females living with type 2 diabetes.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-12-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142853862","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":"https://doi.org/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 to 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 weeks. 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, as well as 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 to 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 PGC-1α expression and an activation of AMPK/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.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-12-16","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":"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":"https://doi.org/10.1152/japplphysiol.00447.2024","url":null,"abstract":"<p><p>Endurance-trained athletes exhibit greater diffusing capacity for carbon monoxide (DLCO) at rest and during exercise as compared to 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 to untrained and that the supine position would elicit a greater DLCO response as compared to the upright position during exercise in both groups. Fourteen endurance-trained (Trained) individuals (<i>V̇</i>O_2peak: 61.1 ± 4.4 ml∙kg^-1∙min^-1) and 14 Untrained individuals (<i>V̇</i>O_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 (p=0.02) effect on DLCO with <i>post-hoc</i> analysis determining DLCO increased from upright to supine position in Trained (p<0.01), but not Untrained (p=0.58). There was no effect of position on exercising DLCO (p=0.16) regardless of group; however, pulmonary capillary blood volume (V_C) was increased with supine exercise (p=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 (p=0.25) and Vc (p=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 to upright position in Trained individuals near-maximal exercise, suggesting a plateau may be reached at maximal exercise.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2024-12-16","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}