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":"10.1152/japplphysiol.00135.2025","url":null,"abstract":"<p><p>Cannabis is among 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 (<i>n</i> = 14; 7 females; 23 ± 3 yr). 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 derecruitment of larger AP clusters (22 ± 11 to 18 ± 9 clusters<b>;</b> <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.<b>NEW & NOTEWORTHY</b> We examined the impact of cannabis inhalation on the firing and recruitment patterns of postganglionic muscle sympathetic action potentials (APs) in humans. We found that cannabis inhalation induced a derecruitment of larger, high-threshold APs, reduced the discharge probability and baroreflex control of medium-sized APs at rest, and impaired sympathetic AP recruitment during an end-expiratory apnea. Collectively, these data indicate that cannabis impairs the fundamental, homeostatic communication between the sympathetic nervous system and cardiovascular system.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1425-1434"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","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":"Corrigendum for Claflin et al., volume 111, 2011, p. 1021-1030.","authors":"","doi":"10.1152/japplphysiol.01119.2010_COR","DOIUrl":"https://doi.org/10.1152/japplphysiol.01119.2010_COR","url":null,"abstract":"","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":"138 6","pages":"1489"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144266320","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":"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, nonsmoking 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) before each exercise training session. Following 6 wk of endurance exercise training (21 training sessions), we determined the effect of blockade versus placebo on improvements in fitness and some of its determinants. The rate of improvement in peak power output over the period of exercise training intervention was 1.62 (0.85, 2.39)% per week in the blockade versus 3.05 (2.27, 3.82)% per week in the placebo group (<i>P</i> < 0.05 blockade vs. placebo). This was paralleled by blunted adaptations in vascular function and oxidative enzyme capacity but not by peak aerobic capacity (V̇o_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.<b>NEW & NOTEWORTHY</b> Histamine appears to be intimately involved with skeletal muscle responses during and following exercise. Blocking histamine's actions during endurance exercise training by taking common over-the-counter antihistamines resulted in diminished gains in fitness. These results indicate that exercise-induced histamine release is important in generating many of the positive adaptations to exercise training.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1398-1410"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","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":"Arterial structure and function in the years after long-duration spaceflight.","authors":"Stuart M C Lee, L Christine Ribeiro, David S Martin, Steven S Laurie, Sara R Zwart, X Chen, Millennia Young, Brian Crucian, Scott M Smith, Brandon R Macias","doi":"10.1152/japplphysiol.00264.2024","DOIUrl":"10.1152/japplphysiol.00264.2024","url":null,"abstract":"<p><p>Spaceflight missions expose astronauts to an increased risk of oxidative stress and inflammatory damage that might accelerate the development or severity of cardiovascular disease. The purpose of this investigation was to determine whether long-duration spaceflight (>4 mo) results in structural and functional changes in the carotid and brachial arteries in the years after landing. Common carotid artery (CCA) intima-media thickness (cIMT), CCA distensibility and stiffness, and brachial artery endothelial-dependent and -independent vasodilation were measured in 13 International Space Station (ISS) astronauts (10 males and 3 females) approximately 180 and 60 days before launch, within 1 wk after landing, and up to 5 yr after landing. Additionally, we reviewed reports of cardiovascular-relevant parameters received from National Aeronautics and Space Administration (NASA) data archives within the Lifetime Surveillance of Astronaut Health obtained during flight certification and postflight annual physical examinations for eight of these astronauts. Postflight cIMT, CCA stiffness, distensibility, and brachial artery dependent- and -independent vasodilation were not different than preflight up to 5 yr after landing. Further, there were no records of newly diagnosed cardiovascular disease. Long-duration spaceflight missions on the ISS did not result in thickening of the carotid artery wall, increased CCA stiffness, endothelial dysfunction, or development of new symptoms or signs of cardiovascular disease in the first 5 years after long-duration spaceflight. Continued long-term surveillance of cardiovascular health in the larger astronaut cohort is necessary to characterize the lifetime risk of disease, particularly in astronauts who venture beyond low Earth orbit and are exposed to deep space radiation.<b>NEW & NOTEWORTHY</b> Previous investigations focused on in- and immediate postflight cardiovascular health indices. Here we report that in the 5 years after long-duration spaceflight in low Earth orbit, there was no evidence of increased carotid artery intima-media thickness or reduced brachial artery endothelium-dependent vasodilation in 13 middle-aged male and female astronauts. Additionally, biomarkers of oxidative stress and inflammation are dynamic in the days after landing and may not reflect the long-term health consequences of spaceflight.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1474-1488"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143967229","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":"Increasing the health span: unique role for exercise.","authors":"Glenn A Gaesser, Stephanie E Hall, Siddhartha S Angadi, David C Poole, Susan B Racette","doi":"10.1152/japplphysiol.00049.2025","DOIUrl":"10.1152/japplphysiol.00049.2025","url":null,"abstract":"<p><p>Health span, that period between birth and onset of major disease(s), when adequate physical and cognitive function permit those daily living activities essential to life quality, is lower in the United States than other developed countries. Physical inactivity and excessive calorie intake occupy dominant roles both in the problem, and by redressing them, in the solution. Consequently, this review focuses on evidence that appropriate exercise engagement and calorie restriction (CR) can improve physical and mental health with a view to extending the health span. Humanity, writ large, has grasped these underlying concepts for Millennia but has been largely intransigent to them. Thus, the final section proposes a novel Monty Python-esque approach that encompasses humanity's inimical sense of humor to increase physical fitness and mental health, restore energy balance, sustain better cognitive function, and extend the health span.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1285-1308"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144063946","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":"Two paths to one destination: altered low-frequency oscillations of cerebral perfusion and oxygenation but not oxygen metabolism in mild cognitive impairment.","authors":"Leena N Shoemaker, Farah Kamar, Daniel Milej, Laura Fitzgibbon-Collins, Rasa Eskandari, Jaspreet Bhangu, J Kevin Shoemaker, Keith St Lawrence","doi":"10.1152/japplphysiol.00884.2024","DOIUrl":"10.1152/japplphysiol.00884.2024","url":null,"abstract":"<p><p>Cerebrovascular dysfunction, a risk factor for dementia, is challenging to detect in mild cognitive impairment (MCI). Herein, we used novel, light-based technology to investigate low-frequency hemodynamic oscillations (LFOs; 0.02-0.16 Hz) in cerebral perfusion, oxygenation, and relative metabolic rate of oxygen (rCMRO₂) in MCI (<i>n</i> = 13; 74 ± 6 yr) and cognitively intact controls (<i>n</i> = 10; 69 ± 6 yr). Relative cerebral microvascular perfusion and tissue oxygenation changes were recorded using a depth-enhanced optical monitoring system. Continuous wavelet transforms were used to compare average LFO power between groups (α = 0.025). Compared with controls, MCI had lower LFO power in microvascular perfusion, greater power in oxygenation (<i>P</i> ≤ 0.02), and no statistical difference in oscillatory power for rCMRO₂. Similar rCMRO₂ but opposing changes in oscillatory power for cerebral perfusion and oxygenation associated with MCI suggest an adaptation to maintain energy production.<b>NEW & NOTEWORTHY</b> We used a novel, depth-enhanced optical monitoring system to investigate low-frequency hemodynamic oscillations (0.02-0.16 Hz) in cerebral microvascular perfusion, oxygenation, and relative metabolic rate of oxygen in patients with MCI and cognitively intact controls. Our findings indicate cerebrovascular dysfunction in MCI, wherein the regulation of oxygenation is altered to maintain metabolism in an environment with attenuated vascular control. These findings highlight the potential of using optical technology to assess cerebrovascular function in MCI.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1361-1371"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144063950","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":"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. Furthermore, earlier studies were completed in males, and we sought to elucidate whether biological sex impacts this relationship. Forty healthy individuals (age: 23 ± 5 yr, 50% female) completed 4 min 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/100 mmHg), following challenged exercise, greater than 1.96 times the coefficient of variation of unchallenged exercise represented the presence of compensatory vasodilation. Data are Δ from rest (means ± SD). Twenty-six individuals responded with compensatory vasodilation, whereas 14 individuals did not (49 ± 20 vs. 0 ± 4%FVC, <i>P</i> < 0.001). RBC desaturation was greater in individuals responding with compensatory vasodilation (-22 ± 9 vs. -5 ± 4%oxygen, <i>P</i> < 0.001) and was negatively correlated with FVC (<i>r</i>_s = -0.819, <i>P</i> < 0.001). Sex had no effect on the presence of compensatory vasodilation (<i>P</i> = 0.507) nor on the extent (<i>P</i> = 0.506) or rate (<i>P</i> = 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.<b>NEW & NOTEWORTHY</b> When challenging muscle blood flow during small muscle mass exercise, compensatory vasodilation may protect the matching of oxygen delivery to the muscle's oxygen demand. The present study extended previous work by revealing an absence of compensatory vasodilation in 35% of individuals. Vasodilation was correlated with red blood cell (RBC) desaturation and sex did not influence the occurrence of experiencing compensatory vasodilation nor the relationship between vasodilation and RBC desaturation.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1435-1448"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","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":"Contributions of the peripheral respiratory chemoreceptors to hyperpnea at intensities below the respiratory compensation point.","authors":"Nasimi A Guluzade, Kira Nishidera, Robin Faricier, Brad J Matushewski, Daniel A Keir","doi":"10.1152/japplphysiol.00103.2025","DOIUrl":"10.1152/japplphysiol.00103.2025","url":null,"abstract":"<p><p>We evaluated the contribution of the peripheral chemoreflex to the breathing response during steady-state exercise at intensities below the respiratory compensation point (RCP). Eighteen healthy, young participants (nine females) completed a maximal exercise protocol (<i>visit 1</i>) and three step-incremental protocols (<i>visits 2-4</i>) over 4 days. The step-incremental protocol involved two 8-min stages in the lower and upper regions of the moderate-intensity domain (MOD₁ and MOD₂; below lactate threshold, LT) and two 12-min stages within the heavy-intensity domain (HVY₁ and HVY₂; between LT and RCP). Six-to-10 breaths of 100% oxygen were administered twice at rest and at three time points during steady-state exercise at each intensity (<i>visits 2</i> and <i>3</i>), and arterialized-venous blood samples were obtained for blood gases and metabolites (<i>visit 4</i>). Gas exchange and ventilatory variables were measured breath-by-breath by metabolic cart and pneumotach. Peripheral chemoreflex contribution was determined as the absolute change in minute ventilation (ΔV̇e) between the average of breaths between 10 and ∼20 s after O₂ breathing and those in the 30 s before O₂ breathing. The average ΔV̇e at rest was -0.3 ± 1.0 L·min^-1 and this value decreased to -2.7 ± 1.6 L·min^-1 at MOD₁, -4.2 ± 1.8 L·min^-1 at MOD₂, -5.8 ± 2.5 L·min^-1 at HVY₁, and -7.0 ± 2.7 L·min^-1 at HVY₂ (one-way ANOVA; <i>P</i> < 0.001). However, the intensity-dependent reduction in ΔV̇e was no longer significant when accounting for [H⁺] [one-way analysis of covariance (ANCOVA); <i>P</i> = 0.515]. Therefore, the peripheral chemoreflex drive to breathe (in L·min^-1) increases with exercise intensity below RCP and may stem from a reflexive response to rising [H⁺].<b>NEW & NOTEWORTHY</b> We assessed peripheral chemoreflex (PChR) contributions to steady-state breathing at rest and at four exercise intensities below the respiratory compensation point by quantifying the fall in ventilation in response to surreptitious oxygen breathing. The magnitude by which ventilation fell increased progressively from rest to the highest intensity, indicating a rising PChR drive. Proton concentration from arterialized-venous blood also increased with intensity. Intensity-dependent increases in PChR drive may reflect a reflexive response to rising proton concentration.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":"1372-1384"},"PeriodicalIF":3.3,"publicationDate":"2025-06-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"143970454","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":"Cumulative Effects of Training at Different Weekly Energy Expenditures on Cardiorespiratory Fitness and Markers of Metabolic Syndrome in STRRIDE-Extension.","authors":"Garrett A Moseley, Leanna M Ross, Katherine A Collins-Bennett, Rebecca North, Johanna L Johnson, William E Kraus","doi":"10.1152/japplphysiol.00743.2024","DOIUrl":"https://doi.org/10.1152/japplphysiol.00743.2024","url":null,"abstract":"<p><p><b>PURPOSE:</b> Assess the cumulative effects of different weekly exercise energy expenditures, with similar total program volume and intensity, on cardiorespiratory fitness (CRF) and metabolic syndrome (MetS). <b>METHODS:</b> Following the 9-month STRRIDE trial, 22 participants continued exercise training for 6-24 months in one of two groups: 1) Low-Amount/Vigorous-Intensity (LAVI; n=14): 14 kcal/kg/week (KKW) at 65-80% peak V̇ O₂; 2) High-Amount/Vigorous-Intensity (HAVI; n=8): 23 KKW at 65-80% peak V̇ O₂. Outcomes included absolute (AV̇ O₂) and relative peak oxygen consumption (RV̇ O₂), body fat percentage, waist circumference, HDL-C, triglycerides, fasting glucose, insulin sensitivity index (SI), and modified MetS z-score. Group comparisons were made at equivalent and differential timepoints with similar total exercise volumes. <b>RESULTS:</b> SI improvements were greater in HAVI compared to LAVI at the LAVI 21- month/HAVI 15-month contrast (mean difference±SD: 2.13±0.68 mU/L/min, p=0.008). AV̇ O₂ and RV̇ O₂ improvements were greater in HAVI at both the LAVI 21-month/HAVI 15-month contrast (model estimate [95% CI]: 0.21 [0.01, 0.40] L/min, p=0.038 and 3.05 [0.14, 5.96] mL/kg/min, p=0.041) and the LAVI 33-month/HAVI 21-month contrast (0.25 [0.04, 0.45] L/min, p=0.022 and 3.21 [0.10, 6.32] mL/kg/min, p=0.044). These AV̇ O₂ contrasts remained significant after adjusting for age and sex. Adherence declined over time. <b>CONCLUSION:</b> When cumulative exercise volumes were similar, body composition and MetS markers adaptated similarly between groups. However, continued training at greater weekly volumes of vigorous exercise resulted in more substantial CRF and SI improvements compared to lesser weekly volumes. Findings suggest factors beyond total energy expenditure-such as exercise frequency or duration-may modulate some longitudinal health improvements.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144187059","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":"Motor unit discharge and torque steadiness is reduced in people with Multiple Sclerosis when performing voluntary muscle contractions.","authors":"Marc C Bruneau, Ben I Goodlich, Tyler T Henderson, Sean A Horan, Justin J Kavanagh","doi":"10.1152/japplphysiol.00096.2025","DOIUrl":"https://doi.org/10.1152/japplphysiol.00096.2025","url":null,"abstract":"<p><p>Although people with MS often report symptoms of muscle weakness and motor fatigue, it is largely unknown how motor unit discharge and force generation is affected by the disease. The current study recruited 13 individuals with relapsing remitting MS (age range: 33-56 yr) and age-, sex-, and height-matched controls to perform submaximal isometric knee extensions at 30%, 50%, and 70% of maximal voluntary contraction (MVC). Motor unit discharge properties were extracted from high-density electromyography (HD-EMG) of the vastus lateralis, and coefficient of variation of torque was used to assess torque steadiness. All data were collected before and after a motor fatigue task, which consisted of sustained MVCs that reduced knee extension torque to 60% of baseline MVC. Compared to healthy controls, the MS group had reduced maximal knee extension torque (-23%, p = 0.042), reduced discharge rate (-0.88 pps, p = 0.003) and increased torque coefficient of variation (CV) (+0.014, p = 0.006) during submaximal baseline contractions. The MS group had a shorter time-to-task failure for sustained MVCs (-19.3s, p < 0.001), reduced discharge rate (- 0.95 pps, p = 0.002), and increased torque CV (+0.039, p > 0.001) compared to controls following the sustained MVCs. Rating of perceived exertion was higher in the MS group compared to controls after the performance of the sustained MVCs (+18%, p < 0.001). These findings indicate that reduced motor unit discharge and torque steadiness are a feature of MS regardless of whether submaximal contractions are performed in the presence of motor fatigue.</p>","PeriodicalId":15160,"journal":{"name":"Journal of applied physiology","volume":" ","pages":""},"PeriodicalIF":3.3,"publicationDate":"2025-05-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"144149387","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}