Journal of applied physiology最新文献

{"title":"Inhibition of muscle sympathetic action potential firing and recruitment patterns following cannabis inhalation in humans.","authors":"Andrew W D'Souza, Johan S Thiessen, Christian P Cheung, Massimo Nardone, Jordan B Lee, Ryleigh E Baker, J Kevin Shoemaker, Jamie F Burr, Philip J Millar","doi":"10.1152/japplphysiol.00135.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00135.2025","url":null,"abstract":"<p><p>Cannabis is amongst the most widely used recreational substances, but the physiological consequences of acute and chronic use remain poorly studied. We recently demonstrated that acute cannabis use reduces muscle sympathetic nerve activity (MSNA). However, MSNA bursts comprise action potentials (APs) of varying size, which exhibit distinct firing and recruitment patterns that represent the communication between the sympathetic nervous system and the circulation. Applying a continuous wavelet transform to the microneurographic MSNA signal, we investigated the hypothesis that sympathetic AP firing patterns would be attenuated following cannabis inhalation at rest and during an end-expiratory apnea in young habitual cannabis users (n=14; 7 females; 23±3 years). Following cannabis inhalation MSNA burst occurrence and amplitude were reduced (all <i>P</i><0.001). Cannabis inhalation lowered the firing probability of medium-sized APs (normalized AP cluster 4: 78±34 to 49±31 %; <i>P</i>=0.03) and induced a de-recruitment of larger AP clusters (22±11 to 18±9 clusters; <i>P</i><0.01). During an end-expiratory apnea following cannabis inhalation, there was an increase in MSNA burst frequency (8±8 to 28±10 bursts/min; <i>P</i><0.01), amplitude (51±8 to 94±34 AU; <i>P</i><0.01), AP frequency (74±146 to 327±387 spikes/min; <i>P</i>=0.01) and the number of APs per burst (6±5 to 10±9 APs/burst; <i>P</i>=0.03). However, the ability to recruit larger AP clusters (15±11 to 16±11 clusters; <i>P</i>=0.57) and alter AP latency (1.23±0.12 to 1.26±0.17 s; <i>P</i>=0.50) was absent. These data indicate that cannabis inhalation acutely decreases sympathetic AP firing and disrupts recruitment patterns in humans.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144086134","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":"Global mitophagy inhibition via BNIP3 ablation is not sufficient to alleviate skeletal muscle impairments in male and female tumor-bearing mice.","authors":"Francielly Morena, Ana Regina Cabrera, Toby L Chambers, Pieter J Koopmans, Seongkyun Lim, Stavroula Tsitkanou, Sabin Khadgi, Calvin Peterson, Eleanor R Schrems, Ruqaiza Muhyudin, Sepideh Shakeri, Kevin Zhao, Devan Mishra, Tyrone Washington, Kevin A Murach, Nicholas P Greene","doi":"10.1152/japplphysiol.00009.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00009.2025","url":null,"abstract":"<p><p>Cancer cachexia (CC) is marked by severe skeletal muscle loss and dysfunction, associated with mitochondrial degeneration. Our previous studies showed induction of the mitophagy marker BNIP3 3-weeks post-Lewis Lung Carcinoma (LLC) induction. We hypothesize excessive mitophagy contributes to muscle wasting in CC. To test this, we used a <i>Bnip3</i> knockout (KO) mouse model with LLC-induced CC to assess its impact on muscle outcomes. 8-weeks-old male and female mice were injected with 1x10⁶ LLC cells or PBS (sham controls). After 4 weeks, we assessed muscle function through dorsiflexor electrophysiology, muscle protein synthesis via deuterium oxide labeling, and mitochondrial respiration. Plantaris and white-gastrocnemius muscles were analyzed for mitochondrial respiratory function, tibialis anterior (TA) for muscle cross-sectional area, and mixed-gastrocnemius for protein and mRNA analysis. <i>Bnip3</i> KO showed some benefits in males, including attenuated fat loss and splenomegaly and near-significant attenuation of EDL mass loss. In females, <i>Bnip3</i> KO did not prevent relative muscle atrophy or functional impairments. In males, KO lowered protein synthesis independent of cancer. Despite KO reducing mitophagy markers, it did not improve muscle mitochondrial respiration or functional outcomes. In both sexes, KO mice exhibited unbalanced mitochondrial dynamics with increased fission and reduced fusion, processes also impaired by LLC. Overall, global <i>Bnip3</i> ablation may not offer significant benefits for CC by itself. These findings suggest targeting aberrant mitophagy via complete <i>Bnip3</i> deletion is insufficient to alleviate cancer-induced muscle detriments in both biological sexes, while BNIP3-mediated mitophagy may be needed to maintain protein anabolism.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144086128","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":"Histamine is a molecular transducer of adaptation to endurance exercise training in humans.","authors":"Dylan C Sieck, Sydney H Kobak, Emily A Larson, Hans C Dreyer, Matthew J Fogarty, Gary C Sieck, Christopher T Minson, John R Halliwill","doi":"10.1152/japplphysiol.00687.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00687.2024","url":null,"abstract":"<p><p>Histamine is an apparent molecular transducer of physical activity responses and antihistamines modify transcription of many of the genes responding to exercise. The purpose of this study was to determine the role of histamine-receptor activation in adaptations to endurance exercise training. Sixteen healthy, non-smoking individuals participated in a randomized double-blind placebo-controlled exercise training protocol with an experimental group receiving combined histamine H¹/H²-receptor antagonists (blockade) and a control group receiving placebo capsules (placebo) prior to each exercise training session. Following six weeks of endurance exercise training (21 training sessions), we determined the effect of blockade vs placebo on improvements in fitness and some of its determinants. The rate of improvement in peak power output over the period of the exercise training intervention was 1.62 (0.85, 2.39) % per week in the blockade vs 3.05 (2.27, 3.82) % per week in the placebo group (P < 0.05 placebo vs control). This was paralleled by blunted adaptations in vascular function and oxidative enzyme capacity but not by peak aerobic capacity (VO^2peak), which increased independent of blockade. Blocking histamine's actions during endurance exercise training via common over-the-counter antihistamines resulted in diminished gains in fitness, indicating that exercise-induced histamine release is important in generating many of the positive adaptations to exercise training that result in improvements in fitness.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144078270","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":"Twenty-One Days of Bed Rest Alter Motor Unit Properties and Neuromuscular Junction Transmission in Young Adults.","authors":"Fabio Sarto, Miloš Kalc, Evgeniia S Motanova, Martino V Franchi, Daniel Stashuk, Nina Murks, Giacomo Valli, Samuele Negro, Tomaž Prašnikar, Mladen Gasparini, Giovanni Martino, Giuseppe De Vito, Aleš Holobar, Boštjan Šimunič, Rado Pišot, Marco V Narici","doi":"10.1152/japplphysiol.00178.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00178.2025","url":null,"abstract":"<p><p>Previous studies showed that properties of higher-threshold motor units (MUs) and neuromuscular junction (NMJ) function are preserved during short-term disuse. This study aimed to test how a longer disuse period affects MU properties, NMJ transmission, and NMJ morphology remodeling. Nine young healthy males (age: 18-29 years) underwent 21 days of horizontal bed rest. Pre- (BR0) and post-bed rest (BR21), quadriceps maximal voluntary contraction (MVC), and size were assessed. We combined intramuscular electromyography (iEMG) and high-density surface electromyography (HDsEMG) recordings on the vastus lateralis to assess MU properties at 25% and 50% of MVC. Muscle biopsies and blood samples were also collected. Quadriceps MVC and size decreased at BR21. We found alterations in MU properties at both contraction intensities, including reduced discharge rate, MU potential area changes, and increased complexity. NMJ transmission was found to be reduced at BR21 at 25% MVC. This functional NMJ impairment was biochemically corroborated by an increase in serum C-terminal agrin fragment concentration, a biomarker of NMJ instability. In addition, a direct assessment of NMJ morphology revealed the presence of some denervated NMJs exclusively at BR21. In conclusion, 21-day bed rest altered MU properties across different contraction intensities and impaired NMJ transmission with initial signs of remodeling/denervation. Disuse duration appears to be a critical factor, as previous shorter studies failed to detect some of these changes. We believe these findings are clinically relevant for disuse after trauma, surgery, or illness, and may support the development of effective countermeasures.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144019625","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":"Lower Diastolic Velocity in the Internal Carotid Artery Mediates Lower Cerebral Blood Flow With Age.","authors":"John Ashley, Evan P Pasha, Takashi Tarumi, Tsubasa Tomoto, Rong Zhang","doi":"10.1152/japplphysiol.00847.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00847.2024","url":null,"abstract":"<p><p>Advanced aging is characterized by reduced cerebral blood flow (CBF) and increased central arterial stiffness. Increased arterial stiffness is associated with increased CBF pulsatility, which is detrimental to cerebrovascular integrity. We examined the associations between central arterial stiffness, diastolic, systolic, and total CBF in healthy cognitively normal subjects (n=163, age 20-81 years, 62% female) who underwent color-coded duplex ultrasonography of the internal carotid (ICA) and the vertebral artery (VA) to measure pulsatile CBF and total CBF. Cerebral tissue oxygenation was measured using near-infrared spectroscopy (NIRS). Carotid β-stiffness index and carotid-femoral pulse wave velocity (cfPWV) were assessed via applanation tonometry and ultrasonography to assess central artery stiffness. Age was negatively associated with total CBF (R² = 0.268, <i>p</i> < 0.001). ICA diastolic velocity was negatively associated with cfPWV (<i>R²</i> = 0.163, <i>p</i> < 0.001) and carotid β-stiffness index (R² = 0.134, <i>p</i> < 0.001). Higher carotid β-stiffness index was associated with lower CBF with age, which was mediated through lower ICA diastolic velocity. These findings suggest central arterial stiffness with age may lead to reductions in ICA diastolic velocity, contributing to a reduction in CBF.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143993866","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":"Circulating miRNA levels following a 14-week aerobicexercise intervention during pregnancy: A secondaryexploratory analysis of the PEACH RCT.","authors":"Alejandro A Candia, Rachel J Skow, Anita Quon, Craig Steinback, Sandra T Davidge, Margie H Davenport","doi":"10.1152/japplphysiol.00101.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00101.2025","url":null,"abstract":"<p><p>Physical activity (PA) during pregnancy decreases the risk of developing hypertensive disorders of pregnancy by 40%, yet the underlying molecular mechanisms are unknown. microRNAs (miRNAs) have shown potential in cardiovascular disease prevention and diagnosis. Circulating levels of miR-21-3p and miR-146b-5p are associated with early pregnancy leisure time PA energy expenditure. However, it is not clear how miRNAs levels change in response to exercise across pregnancy.</p><p><strong>Aim: </strong>To determine the change in circulating levels of miRNAs after a 14-week, moderate-intensity aerobic exercise intervention in pregnant women.</p><p><strong>Methods: </strong>A subset of 10 pregnant women from the Prenatal Exercise and Cardiovascular Health (PEACH) study were included. Participants were randomized to a supervised aerobic exercise program (n=5) or a control group (n=5). At 18-21 (baseline) and 34-36 (postintervention, PI) weeks of pregnancy, a fasted blood draw and neurovascular assessment were carried out. Muscle sympathetic nerve activity burst incidence (BI), heart rate (HR), systolic, diastolic, and mean arterial blood pressure (SBP, DBP, and MAP, respectively), cardiac output (CO), and plasma miRNA levels were measured at each timepoint.</p><p><strong>Results: </strong>Exercise prevented the rise in BI from baseline to PI. At baseline both miRNA-146b-5p and miR-21-3p levels were not different between groups. miR-21-3p increased from baseline to PI in both groups, but the exercise group had significantly higher levels at PI.</p><p><strong>Conclusion: </strong>A 14-week aerobic exercise training intervention during pregnancy increases miR-21-3p levels in maternal plasma. Future work in a larger cohort will allow us to determine the relationship of miR-21-3p with maternal outcomes.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143965615","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":"Effect of aging, endurance training, and denervation on innate immune signaling in skeletal muscle.","authors":"Priyanka Khemraj, Anastasiya Kuznyetsova, David A Hood","doi":"10.1152/japplphysiol.00038.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00038.2025","url":null,"abstract":"<p><p>Skeletal muscle function relies on mitochondria for energy and for mediating its unique adaptive plasticity. The NLRP3 inflammasome complex is an innate immune mechanism that responds to mitochondrial damage-associated molecular patterns (DAMPS), however its activity relative to mitochondrial dysfunction in muscle requires exploration. The purpose of this study was to characterize immune signaling and mitochondrial function in muscle during aging, endurance training, and disuse induced by denervation. Denervation led to decreases in muscle mass, mitochondrial content, and impaired respiration. Protein analyses revealed increases in NF-κB p65 and downstream inflammatory markers including NLRP3, caspase-1, GSDMD-N, STING and IL-1β, along with pro-apoptotic BAX and AIF. When assessing potential DAMPS, denervation led to increased ROS production but no changes in cytosolic mtDNA levels, relative to total mtDNA. Since we hypothesized that inflammasome activation would be increased with age, we studied young (6-8 months) and aged (21-22 months) mice that remained sedentary or underwent a 6-week voluntary running protocol. Aging resulted in marked increases in the expression of multiple pro-inflammatory and pro-apoptotic proteins. Remarkably, training uniformly attenuated age-related increases in BAX, NLRP3, caspase-1, STING, and GSDMD protein expression, and tended to reduce the elevated level of cytosolic mtDNA evident in aged muscle. Training adaptations were evident also in the aged animals by the preservation of muscle mass and improvements in oxygen consumption and endurance performance and were achieved despite a lower training distance than in young animals. Our results strongly implicate endurance training as a promising therapeutic for combatting disuse and age-related inflammation in skeletal muscle.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143997431","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":"Cardiovascular Responses to Standing with and without Lower Body Compression Garments after Long-Duration Spaceflight.","authors":"Stuart M C Lee, Annelise Miller, L Christine Ribeiro, Marissa Rosenberg, Christopher A Miller, Steven S Laurie, Millennia Young, Jason R Lytle, Igor Kofman, Gilles Clement, Scott Wood, Ilya Rukavishnikov, Vladimir Kitov, Inessa Kozlovskaya, Elena Tomilovskaya, Millard Reschke, Brandon R Macias","doi":"10.1152/japplphysiol.00646.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00646.2024","url":null,"abstract":"<p><p>Long-duration astronauts (>4 months on the International Space Station, 87 total person-missions) participated in an orthostatic test consisting of 2 minutes of prone rest followed by 3.5 minutes of standing preflight, within hours of landing on the first day of recovery (R+0), and 1, 3, 7, 14, and 30 days after landing. Astronauts and cosmonauts performed exercise during spaceflight and fluid loading before landing to mitigate cardiovascular deconditioning. On R+0, astronauts participated in testing without compression garments or while wearing 1 of 3 garments designed to prevent orthostatic intolerance: Russian Kentavr, National Aeronautics and Space Administration's gradient compression garment (GCG), or SpaceX's gradient orthostatic protection garment (OPG). On R+0, the change in mean arterial pressure (ΔMAP) from prone to standing tended to decrease without compression garments (-8 mmHg, p=.053) and was less in astronauts wearing the Kentavr (-5 mmHg, p=.02), but not in crewmembers wearing the GCG or OPG. The heart rate response from prone to standing (ΔHR) on R+0 tended to increase in those not wearing compression garments (+11 bpm, p=.051) and was greater when wearing the Kentavr (+9 bpm, p<.0001) or the OPG (+10 bpm, p=.003), but not different in those wearing the GCG (+1 bpm, p=0.74). Although ΔHR when not wearing compression garments was greater (p<.05) for at least 2 weeks after landing, ΔMAP was not different from preflight. Wearing NASA's GCG mitigates cardiovascular stress during standing after long-duration spaceflight, and full recovery of orthostatic responses to standing without compression garments is not complete for weeks.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144036079","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 Contribution of Red Blood Cell Desaturation to Exercising Skeletal Muscle Vasodilation Heterogeneity.","authors":"Jacob L Schwartz, Adam N Di Salvo, Jonaline B Bernal, Sinan Osman, Robert F Bentley","doi":"10.1152/japplphysiol.00136.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00136.2025","url":null,"abstract":"<p><p>Experimentally challenging muscle blood flow during exercise requires cardiovascular compensation to protect the matching of oxygen delivery to oxygen demand; however, certain individuals may fail to protect this matching due to an absence of compensatory vasodilation at the local vasculature. We investigated whether red blood cell (RBC) desaturation explains the underlying presence of compensatory vasodilation. Further, prior studies were completed in males, and we sought to elucidate whether biological sex impacts this relationship. 40 healthy individuals (23±5 yrs, 50% female) completed four-minutes of submaximal forearm handgrip exercise at 30% maximum voluntary contraction both with and without brachial artery compression reducing forearm blood velocity by 30% and challenging muscle blood flow. Measures of forearm blood flow (ml/min), blood pressure (mmHg) and RBC desaturation (skeletal muscle oxygen saturation, %) were obtained throughout. Forearm vascular conductance (FVC, ml/min/100mmHg) following challenged exercise greater than 1.96 the coefficient of variation of unchallenged exercise represented the presence of compensatory vasodilation. Data are Δ from rest (mean±SD). 26 individuals responded with compensatory vasodilation while 14 individuals did not (49±20 vs. 0±4 %FVC, p<0.001). RBC desaturation was greater in individuals responding with compensatory vasodilation (-22±9 vs. -5±4 %oxygen, p<0.001) and was negatively correlated with FVC (r_s=-0.819, p<0.001). Sex had no effect on the presence of compensatory vasodilation (p=0.507), nor on the extent (p=0.506) or rate (p=0.857) of RBC desaturation during the muscle blood flow challenge. The presence/absence of compensatory vasodilation following a muscle blood flow challenge appears to be proportional between sex and associated with local RBC desaturation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144016345","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":3,"RegionCategory":"医学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Muscle temperature increases during a single far infrared sauna session without changes in intestinal temperature.","authors":"Emma L Reed, Colleen C Uzoekwe, Jessica K Atencio, Christopher T Minson, John R Halliwill","doi":"10.1152/japplphysiol.00067.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00067.2025","url":null,"abstract":"<p><p>Increases in muscle temperature during exercise and passive heating are associated with beneficial outcomes. Far infrared (FIR) saunas are a radiant heating stimulus. It has been claimed that FIR waves penetrate 3 to 4 cm deep into the peripheral tissues but muscle temperature during FIR sauna bathing is unknown. The purpose was to quantify muscle temperature at three different depths during a FIR sauna session. Ten adults had a multi-sensor intramuscular temperature probe inserted into the quadriceps muscles prior to sitting in a FIR sauna for 45 min. Thermocouples were 3.4 cm (deep), 2.4 cm (middle), and 1.4 cm (superficial) below the skin surface. Muscle, core, and skin temperatures, and nude body weight (to calculate whole body sweat rate) were collected before and at the end of heating. Data are reported as (mean [95% confidence intervals]). Muscle temperature increased at the deep (+1.1 [0.3, 1.9]°C), middle (+1.9 [1.0, 2.9]°C), and superficial (+3.0 [1.8, 4.1]°C) depths (all P<0.04). There was no change in core temperature (0.0 [-0.1, 0.1]°C) (P=0.94) but there was an increase in mean body temperature (+1.3 [1.1, 4.1]°C) (P<0.01) driven by increases in mean skin temperature (+6.2 [5.8, 6.8]°C) (P<0.01). Participants lost 0.48 [-0.60, -0.37]% of body weight and had a whole body sweat rate of 0.46 [0.31, 0.61] L/h. The magnitude of increase in muscle temperature was dependent on depth relative to the skin surface. These data imply commercially available FIR saunas provide only superficial heating of peripheral tissues.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143993046","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}