Journal of applied physiology最新文献

{"title":"Repeated hyperbaric oxygen exposure accelerates fatigue and impairs SR-calcium release in mice.","authors":"Heath G Gasier, Jack Kovach, Kris Porter","doi":"10.1152/japplphysiol.00723.2024","DOIUrl":"10.1152/japplphysiol.00723.2024","url":null,"abstract":"<p><p>Breathing hyperoxic gas is common in diving and accelerates fatigue after prolonged and repeated exposure. The mechanism(s) remain unknown but may be related to increased oxidants that interfere with skeletal muscle calcium trafficking or impaired aerobic ATP production. To determine these possibilities, C57BL/6J mice were exposed to hyperbaric oxygen (HBO₂) for 4 h on three consecutive days or remained in room air. Postfinal exposure, fatigue was determined by grip strength and run-to-exhaustion tests. Other measurements included indices of oxidant stress and antioxidant defenses, mitochondrial bioenergetics, caffeine-induced sarcoplasmic reticulum-calcium release, and <i>S</i>-nitrosylation of ryanodine receptor 1 (RyR1). Despite grip strength being unaffected by repeated HBO₂ exposure, mean running time was reduced by 50%. In skeletal muscle from HBO₂ exposed mice, superoxide production was significantly increased, resulting in elevated lipid and DNA (nuclear and mitochondrial) oxidation. Accompanying increased oxidant stress was a reduction in glutathione content and increased <i>Sod1</i> and <i>Hmox1</i> gene expression; <i>Ucp3</i> mRNA was reduced. Mitochondrial respiration, mitochondrial membrane potential, and NAD⁺/NADH were not influenced by HBO₂. In contrast, caffeine-induced sarcoplasmic reticulum (SR)-calcium release was reduced by 66% and <i>S</i>-nitrosylation of RyR1 was increased by 45%. Exposing mice to repeated HBO₂ increases oxidant stress that activates some antioxidant defenses. Mitochondrial function is not altered and could be related to decreased production of UCP3 that serves to maintain the electrochemical proton gradient. <i>S</i>-nitrosylation of RyR1 may promote SR-calcium leak and reduce content, a potential mechanism for repeated HBO₂-induced fatigue.<b>NEW & NOTEWORTHY</b> Breathing hyperoxic gas during prolonged and repeated dives causes fatigue but the mechanisms are unknown. Here, we show in mice exposed to repeated hyperbaric oxygen that running fatigue is accelerated and accompanied by increased skeletal muscle oxidant stress and reduced caffeine-induced sarcoplasmic reticulum (SR)-calcium release. The latter may be due to increased <i>S</i>-nitrosylation of ryanodine receptor 1 (RyR1) and be a mechanism for impaired physical performance after repeated oxygen diving.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"415-425"},"PeriodicalIF":3.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142894725","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":"Acute selective serotonin-reuptake inhibition elevates basal ventilation and attenuates the rebreathing ventilatory response, independent of cerebral perfusion.","authors":"Jay M J R Carr, Jodie Koep, L Madden Brewster, Ayechew Getu, Jonah C Dizon, Declan Isaak, Andrew Steele, Connor A Howe, Philip N Ainslie","doi":"10.1152/japplphysiol.00751.2024","DOIUrl":"10.1152/japplphysiol.00751.2024","url":null,"abstract":"<p><p>Serotonin (5-HT) is integral to signaling in areas of the brainstem controlling ventilation and is involved in central chemoreception. Selective serotonin reuptake inhibitors (SSRIs), used to effectively increase 5-HT concentrations, are commonly prescribed for depression. The effects of SSRIs on the control of breathing and the potential influence of cerebral blood flow (CBF) have not been directly assessed. We hypothesized that a single SSRI dose in healthy adults would not impact resting ventilation, global CBF, or brainstem blood flow reactivity to CO₂ but would steepen the slope of the hypercapnic ventilatory response (HCVR). In 15 young, healthy adults (6 females, 25 [Formula: see text] 5 yr, 70 [Formula: see text] 10 kg, 172 [Formula: see text] 15 cm, 24 [Formula: see text] 4 kg/cm²), using a placebo-controlled, double-blind, randomized design, we assessed baseline cardiorespiratory and CBF (duplex ultrasound) responses to SSRI (40 mg citalopram), as well as to hyperoxic hypercapnic rebreathing (as an index of central chemoreception). Baseline measures of mean arterial pressure, heart rate, minute ventilation, CBF, and the pressures of end-tidal oxygen and carbon dioxide were all not influenced by SSRI. Likewise, the sum of blood flowing through both vertebral arteries (as an index of brainstem blood flow) during hypercapnia was also unchanged. In contrast, basal ventilation (during rebreathing following hyperventilation and during hyperoxia) was elevated from 9.5 [Formula: see text] 4.1 to 11.5 [Formula: see text] 5.5 L/min (interaction <i>P</i> = 0.023); and counter to our hypothesis, the central chemoreceptor-mediated ventilatory response to CO₂ was reduced following SSRI from 7.5 [Formula: see text] 5.3 to 5.1 [Formula: see text] 4.1 L/min/mmHg (interaction <i>P</i> = 0.027). The implications of these findings in health and pathology remain to be determined.<b>NEW & NOTEWORTHY</b> Acute inhibition of serotonin reuptake with citalopram diminishes the ventilatory response to hyperoxic hypercapnic rebreathing, possibly indicating decreased sensitivity of the central chemoreceptors and respiratory control centers. Additionally, ventilation during minimal chemoreceptor activation-i.e., following hypocapnia during hyperoxia-is elevated, perhaps signifying an increased tonic activity of the respiratory control areas. These changes appear to be independent of brainstem blood flow. These findings may have implications for antidepressant drug use.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"592-602"},"PeriodicalIF":3.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143005995","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 leg immobilization and recovery resistance training on skeletal muscle-molecular markers in previously resistance-trained versus untrained adults.","authors":"J Max Michel, Joshua S Godwin, Daniel L Plotkin, Mason C McIntosh, Madison L Mattingly, Philip J Agostinelli, Breanna J Mueller, Derick A Anglin, Nicholas J Kontos, Alexander C Berry, Marina Meyer Vega, Autumn A Pipkin, Matt S Stock, Zachary A Graham, Harsimran S Baweja, C Brooks Mobley, Marcas M Bamman, Michael D Roberts","doi":"10.1152/japplphysiol.00837.2024","DOIUrl":"10.1152/japplphysiol.00837.2024","url":null,"abstract":"<p><p>We sought to examine how resistance training (RT) status in young healthy individuals, either well resistance trained (T, <i>n</i> = 10) or untrained (UT, <i>n</i> = 11), affected molecular markers with leg immobilization followed by recovery RT. All participants underwent 2 wk of left leg immobilization via a locking leg brace. Afterward, all participants underwent 8 wk (3 days/wk) of knee extensor-focused progressive RT. Vastus lateralis (VL) ultrasound-derived thickness and muscle cross-sectional area were measured at baseline (PRE), immediately after disuse (MID), and after RT (POST) with VL muscle biopsies also being collected at these time points. Both groups presented lower ultrasound-derived VL size metrics at MID versus PRE (<i>P</i> ≤ 0.001), and values increased in both groups from MID to POST (<i>P</i> < 0.05); however, VL size increased from PRE to POST in UT only (<i>P</i> < 0.001). Mean and type II myofiber cross-sectional area values were greater at PRE and POST versus MID (<i>P</i> < 0.05), with T being greater than UT throughout (<i>P</i> ≤ 0.012). In both groups, satellite cell number was not affected by leg immobilization but increased in response to RT (<i>P</i> ≤ 0.014), with T being greater than UT throughout (<i>P</i> = 0.004). Total RNA (ribosome content) decreased (<i>P</i> = 0.010) from PRE to MID while total RNA and certain endoplasmic reticulum stress proteins increased from MID to POST regardless of training status. Immobilization-induced muscle atrophy and recovery RT hypertrophy outcomes are similar between UT and T participants, and the lack of molecular signature differences between groups supports these findings. However, results are limited to younger adults undergoing noncomplicated disuse.<b>NEW & NOTEWORTHY</b> Formerly trained and untrained individuals demonstrate similar atrophic responses to disuse while untrained individuals exhibited a greater hypertrophic response to subsequent resistance training. The molecular responses accompanying these changes were largely similar between groups and included increases in satellite cell content with resistance training and increases in ribosome biogenesis, which was largely driven by the formerly trained group.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"450-467"},"PeriodicalIF":3.3,"publicationDate":"2025-02-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143006002","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Daily blood flow restriction does not affect muscle fiber capillarization and satellite cell content during 2 wk of bed rest in healthy young men.","authors":"Thorben Aussieker, Cas J Fuchs, Antoine H Zorenc, Lex B Verdijk, Luc J C van Loon, Tim Snijders","doi":"10.1152/japplphysiol.00461.2024","DOIUrl":"10.1152/japplphysiol.00461.2024","url":null,"abstract":"<p><p>The present study assessed whether single-leg daily blood flow restriction (BFR) treatment attenuates the decline in muscle fiber size, capillarization, and satellite cell (SC) content during 2 wk of bed rest in healthy, young men. Twelve healthy, young men (age: 24 ± 3 yr; BMI: 23.7 ± 3.1 kg/m²) were subjected to 2 wk of bed rest, during which one leg was exposed to three times daily 5 min of BFR, whereas the contralateral leg received sham treatment [control (CON)]. Muscle biopsies were obtained from the m. vastus lateralis from both the BFR and CON legs before and immediately after 2 wk of bed rest. Types I and II muscle fiber size, myonuclear content, capillarization, and SC content were assessed by immunohistochemistry. No significant decline in either type I or type II muscle fiber size was observed following bed rest, with no differences between the CON and BFR legs (<i>P</i> > 0.05). Type I muscle fiber capillary density increased in response to bed rest in both legs (<i>P</i> < 0.05), whereas other muscle fiber capillarization measures remained unaltered. SC content decreased in both type I (from 7.4 ± 3.2 to 5.9 ± 2.7 per 100 fibers) and type II (from 7.2 ± 3.4 to 6.5 ± 3.2 per 100 fibers) muscle fibers (main effect of time <i>P</i> = 0.018), with no significant differences between the BFR and CON legs (<i>P</i> > 0.05). In conclusion, 2 wk of bed rest has no effect on muscle capillarization and decreases the SC content, and daily BFR treatment does not affect skeletal muscle fiber size and SC content in healthy, young men.<b>NEW & NOTEWORTHY</b> We recently reported that the application of daily blood flow restriction (BFR) treatment does not preserve muscle mass or strength and does not modulate daily muscle protein synthesis rates during 2 wk of bed rest. Here, we show that 2 wk of bed rest resulted in a decrease in satellite cell (SC) content. In addition, the BFR treatment did not affect muscle fiber size, capillarization, and SC content during 2 wk of bed rest.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"89-98"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142769265","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 acute sleep restriction on cerebrovascular reactivity and neurovascular coupling in young men and women.","authors":"Matthew J McDonald, Megan L Marsh, Sharon D Fears, Brian Shariffi, Jill A Kanaley, Jacqueline K Limberg","doi":"10.1152/japplphysiol.00648.2024","DOIUrl":"10.1152/japplphysiol.00648.2024","url":null,"abstract":"<p><p>Chronic exposure to shortened sleep is associated with an increased risk of Alzheimer's disease and dementia. Previous studies show insufficient (e.g., poor or fragmented) sleep impairs cerebrovascular reactivity to metabolic stress and may have a detrimental effect on the link between cerebral blood flow (CBF) and neural activity (i.e., neurovascular coupling, NVC). The purpose of this study was to examine the effect of acute sleep restriction on CBF in response to a metabolic (carbon dioxide, CO₂) and a cognitive stressor. We hypothesized sleep restriction (4-h time in bed) would attenuate CBF and NVC. Sixteen young adults (8 M/8 F, 28 ± 8 yr, 25 ± 3 kg/m²) completed two morning visits following a night of normal (7.38 ± 0.82 h) or restricted (4.27 ± 0.93 h, <i>P</i> < 0.001) sleep duration. Middle cerebral artery velocity (MCAv, transcranial Doppler ultrasound) was measured at rest and during <i>1</i>) 5 min of carbogen air-breathing and <i>2</i>) five trials consisting of a period of eyes closed (30 s), followed by eyes open (40 s) while being challenged with a validated visual paradigm (Where's Waldo). Baseline MCAv was unaffected by acute sleep restriction (control: 64 ± 14 cm/s; restricted 61 ± 13 cm/s; <i>P</i> = 0.412). MCAv increased with CO₂; however, there was no effect of restricted sleep (<i>P</i> = 0.488). MCAv increased in response to visual stimulation; the peak NVC response was reduced from control following restricted sleep (control: 16 ± 12%; restricted: 9 ± 7%; <i>P</i> = 0.008). Despite no effect of acute sleep restriction on resting CBF or the response to CO₂ in young men and women, NVC was attenuated following a night of shortened sleep. These data support an important role for sleep in NVC and may have implications for the development of neurodegenerative disease states, such as Alzheimer's and dementia.<b>NEW & NOTEWORTHY</b> Chronic exposure to shortened sleep is associated with an increased risk of Alzheimer's disease and dementia. We examined the effect of acute sleep restriction (4-h time in bed) on cerebral blood flow in response to a metabolic (carbon dioxide) and a cognitive stimulus. Despite no effect of acute sleep restriction on resting cerebral blood flow or the response to carbon dioxide in young men and women, neurovascular coupling was attenuated following a night of shortened sleep.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"282-288"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142807154","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":"Characterization of upper esophageal sphincter pressures relative to vocal acoustics.","authors":"Jesse D Hoffmeister, Jürgen Konczak, Stephanie N Misono","doi":"10.1152/japplphysiol.00385.2024","DOIUrl":"10.1152/japplphysiol.00385.2024","url":null,"abstract":"<p><p>Strength of vocal fold adduction has been hypothesized to be a critical factor influencing vocal acoustics but has been difficult to measure directly during phonation. Recent work has suggested that upper esophageal sphincter (UES) pressure, which can be easily assessed, increases with stronger vocal fold adduction, raising the possibility that UES pressure might indirectly reflect vocal fold adduction strength. However, concurrent UES pressure and vocal acoustics have not previously been examined across different vocal tasks. Doing so may offer insights into the potential use of UES pressure for relative quantification of the strength of vocal fold adduction and how this might contribute to vocal acoustics across different vocal tasks. We assessed UES pressure relative to vocal acoustics in 32 vocally healthy adults during sustained vowels, whispered sentences, and spoken sentences. Smoothed cepstral peak prominence (CPPs) and low-to-high spectral energy ratio (LHR) were derived from the acoustic signal. After controlling for resting UES pressure, age, and sex, we observed significant negative correlations between UES pressure and CPPs and a significant positive correlation between UES pressure and LHR. UES pressures were significantly higher during spoken sentences than whispered sentences and sustained vowels. Measuring UES pressure relative to vocal acoustics is a novel methodology for studying upper aerodigestive tract physiology during phonation and has the potential to enhance understanding of voice disruption in clinical populations. Clinical implications and considerations for implementation are discussed.<b>NEW & NOTEWORTHY</b> We identified relationships between upper esophageal sphincter (UES) pressures and vocal acoustics during phonation in vocally healthy individuals, potentially reflecting the influence of strength of vocal fold adduction and other phonatory factors on vocal acoustics. This methodology could lead to the development of a clinical and research tool that could provide insight into the strength of vocal fold adduction, a critical factor influencing voice quality that has historically been difficult to assess.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"203-212"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142789512","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 differences between postmenopausal women and similar-age men in response to orthostatic stress following 2 wk of bed rest.","authors":"Eric T Hedge, Carmelo J Mastrandrea, Courtney A Patterson, Richard L Hughson","doi":"10.1152/japplphysiol.00477.2024","DOIUrl":"10.1152/japplphysiol.00477.2024","url":null,"abstract":"<p><p>Reduced orthostatic tolerance is common following periods of bed rest that are associated with illness or surgery, putting individuals at higher risk for syncope and falls following hospitalization. Following menopause, mechanisms of female cardiovascular regulation change, which may be associated with sex-specific responses to orthostatic stress following bed rest. The purpose of our experiment was to investigate sex differences between healthy postmenopausal women and similar-age men (age: 55-65 yr) for their orthostatic tolerance and cerebrovascular responses to standing following bed rest. Twenty-two late-middle-aged adults (11 women) completed 14 days of head-down bed rest, with half of the participants being randomized into an exercise group that performed high-intensity exercise during bed rest. Supine-to-stand tests were performed before and ∼5 h after bed rest. Women had lower orthostatic tolerance than men after bed rest (bed rest × sex interaction: <i>P</i> = 0.004), without a protective effect of daily exercise. Both men and women were mildly hypocapnic while supine (main effect: <i>P</i> = 0.019) following bed rest and had lower middle cerebral artery blood velocity (MCAv) nadirs upon standing (main effect: <i>P</i> = 0.027). During the third minute of standing, both men and women had lower end-tidal Pco₂ (main effect: <i>P</i> < 0.001) and MCAv (main effect: <i>P</i> = 0.002) after bed rest, but only men had increased cerebrovascular resistance index (bed rest × sex interaction: <i>P</i> = 0.005) and only women were hypotensive (bed rest × sex interaction: <i>P</i> = 0.020) compared with pre-bed rest. Accordingly, lower MCAv of postmenopausal women and men while standing after bed rest was mediated by different factors.<b>NEW & NOTEWORTHY</b> Postmenopausal women had lower orthostatic tolerance than similar-age men while standing post-bed rest. Both sexes exhibited lower cerebral blood velocity nadirs upon standing; however, sex-specific interactions of the determinants of cerebral perfusion (i.e., Pco₂, cerebrovascular resistance index, and arterial pressure) were observed during prolonged standing after bed rest. These results indicate that postmenopausal women and men have different factors underlying reduced cerebral perfusion while standing after bed rest.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"226-237"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142828573","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 extraction of neural strategies from the surface EMG: 2004-2024.","authors":"Dario Farina, Roberto Merletti, Roger M Enoka","doi":"10.1152/japplphysiol.00453.2024","DOIUrl":"10.1152/japplphysiol.00453.2024","url":null,"abstract":"<p><p>This review follows two previous papers [Farina et al. <i>Appl Physiol (1985)</i> 96: 1486-1495, 2004; Farina et al. <i>J Appl Physiol (1985)</i> 117: 1215-1230, 2014] in which we reflected on the use of surface electromyography (EMG) in the study of the neural control of movement. This series of papers began with an analysis of the indirect approaches of EMG processing to infer the neural control strategies and then closely followed the progress in EMG technology. In this third paper, we focus on three main areas: surface EMG modeling; surface EMG processing, with an emphasis on decomposition; and interfacing applications of surface EMG recordings. We highlight the latest advances in EMG models that allow fast generation of simulated signals from realistic volume conductors, with applications ranging from validation of algorithms to identification of nonmeasurable parameters by inverse modeling. Surface EMG decomposition is currently an established state-of-the-art tool for physiological investigations of motor units. It is now possible to identify large samples of motor units, to track motor units over multiple sessions, to partially compensate for the nonstationarities in dynamic contractions, and to decompose signals in real time. The latter achievement has facilitated advances in myocontrol, by using the online decoded neural drive as a control signal, such as in the interfacing of prostheses. Looking back over the 20 yr since our first review, we conclude that the recording and analysis of surface EMG signals have seen breakthrough advances in this period. Although challenges in its application and interpretation remain, surface EMG is now a solid and unique tool for the study of the neural control of movement.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"121-135"},"PeriodicalIF":3.3,"publicationDate":"2025-01-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142687153","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}